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49 er C board section


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#1 Andrew P

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Posted 20 February 2013 - 11:18 PM

Many years back Julian & Frank B published an article on the development of the 49 er Cb section and in particular some improvements to drag reduction as a consequence of some changes to the leading edge radius.

Anybody got a copy of the article or in E form that can be posted.

#2 Rohanoz

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Posted 20 February 2013 - 11:44 PM

I'll dig through my stuff - I remember reading this with great interest, something about low speed lift increases without drag increase.

I think Julian may be working on something similar again with 29er foils as well... Probably worth sending him a PM (JulianB on here).

#3 mustang__1

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Posted 21 February 2013 - 12:37 AM

rumors are correct - there is a nearly definite change coming to the 29er CB/rudder. The change will at the least be in materials - i am not sure if there will be a shape change as well. i cant say im particularly a fan of it, but, whatever.

#4 Jethrow

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Posted 21 February 2013 - 06:54 AM

I don't sail either of these boats but why would they change the foils on an established OD class? I can't imagine that many would be racing handicap...

#5 mustang__1

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Posted 21 February 2013 - 07:07 AM

yeah... im aware... the claim is that it will actually be cheaer because quality Al extrusions are getting harder to source.

#6 duncan (the other one)

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Posted 21 February 2013 - 09:57 AM

extrusions? Isn't the board hollow: Al plates mashed into a mould?

#7 JulianB

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Posted 21 February 2013 - 11:02 AM

Yes I am here.

3 completely different issues at play here.

#1 Is the most efficient profile, and then section and then % camber which includes LE radius of a Centre board and then all that again for the Rudder, because by definition they should be different. And again this is for a given boat.

#2 What is more cost effective, extruded alloy foils or infused FRP foils included in that longevity, maintance etc etc, into this comes long term supply issues and the class changing rules Etc Etc.

#3 Is should there be a progressive technology process in a OD class.

So to not go way off on tangents, which do you want to talk about first?????

JB

#8 B.Wilkinson

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Posted 21 February 2013 - 06:18 PM

Id like to hear more about your #3^^^^

#9 Rohanoz

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Posted 21 February 2013 - 09:26 PM

Can we add #4?
- board stiffness and twist design trade offs

#10 Luke Piewalker

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Posted 21 February 2013 - 09:52 PM

My take on #3 is that in a lot of (SM)OD designs things remain static for a long time and then any changes are seen as too great (causing ructions) or you end up with poor value parts because you remain tied to a specification that seemed like a good idea at the time, but five years down the line you suddenly find you are the only customer left and are paying an increasing amount for something (this often seems to happen with sailcloth...) which could have been replaced by something readily available 'off-the-shelf'

Of course, I could be talking crap...

#11 Ben G

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Posted 21 February 2013 - 10:35 PM

I'm interested in topic #1.. profile shape and section shape.
My conclusion so far (assuming draft isn't a problem) is:
-a stretched elliptical chord distribution (ie more triangular than an ellipse) which allows a higher aspect ratio without increasing the overturning moment
and (for the same curved-triangular shape)
-a slightly thinner % foil section at the top and slightly fuller at the tip, to allow for the change in angle of attack due to washout (tip vortex). What thoughts about LE radius?
#4 twist and stiffness are interesting topics but I've no idea where to start.. talk on!

#12 JulianB

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Posted 21 February 2013 - 10:43 PM

#3 is easy, in my case does not matter if it’s the 49er or the 29er or any of a raft of other Closed Class One Designs.

The class, the sailors decided if they want it to be an evolving class or a ridged class.

WRT the 49er and 29er, the entire proposed "spec" changes are/where sailor driven. The carbon mast, Square head sail, whole new hull/deck/wing tooling (in the case of the 49er) where all sailor driven.

As a builder there is at least a 3-4 year pay back on these things, they cost a huge amount of money to do, and when you launch them you have 1-2 years of teething issues always.

It’s a fact that we sold almost 450 carbon mast in the first six month of introduction. That is testament to the fact we had sailor buy in. 50-100 maybe for Olympic aspirants, but the rest of the fleet just wanted the new kits, their kit! And I can tell you it’s also a fact that Southern Spars did not make a cent on those 450 masts. They probably broke even around the 700th mast. First we had them twisting, then we had the 5mm bolts sheering then we introduced the tongue system, and with that we had to alter the whole mast wall issue at the joints.

Dose not matter how good you are and SS are possibly the best, nothing prepares you for what I call "live" testing or testing in "anger".

We also had issues with the sails, with excessive downhaul loads, so you end up chasing your tail.

So bottom line, sit on your hands and you get to the point where say the Club 420 is now, (I have been told by 2 builders, both have the same story) where a foam sandwich boat would be cheaper, more durable, last longer, and incidental more fun, and this is because more than anything else technology is marching on, it won't stay still.

Or you do an evolution, which is what the 49er class and sailors has chosen to do.

The biggest issue is information. People don't like to be treated as mushrooms, If you are public, you say you are looking at this or that change in 3-4-5 years’ time for these reasons and they have merit, they you have cohesion and the sailors "buy in".

If you as a class or a builders group can’t get the buy in, then you don't do it. It’s a beating from hell if you try.

WRT foils on the 29er, there are lots of good reasons not to do it, and lots of good reason to do it. It is very much a sailor driven thing (FRP 29er foils), coming from Scandinavia. The present issue is cost of the core, & what is the core. Technology is known, its being used every day in the 49er but the cost is presently a little too excessive to warrant the change ( I normally quote a 7% hassle factor) but it is also inevitable that alloy will get more and more expensive, and infusion/RMT/milling is getting cheaper, so it’s inevitable unless you want to stick you head in the sand and a switch to infused or RMT foils is going to happen.

The other issue that was sailor driven, this time from Perth but it also has merit is turn-buckles on 29er shrouds. Again technology, a sensational Blue Wave turn-buckle has become available, its almost as cheap as the existing rack, and the evidence, again from the 49er is it will pay for itself in the lack of breakages and people getting out of control as the wind alters during a 3-4 races per day.

But again, all of this is presently held up by the Class technical committee. Being commercial, I hope they sit on their hands for a long time. From a sailors POV, it’s probably time.

​In closing, I hasten to add, without sailor buy in, without class buy in, & without builder buy in, your unlikely to get ISAF approval (WRT Int classes) and to change any "spec" with the 29er or the 49er, you need both my signature (so you also need my buy-in and that should not be taken as given) but you also need Dr Jason Smithwicks (ISAF tech manager) signature.

So there are more than a few hoops to jump, so by the time you have got through all of those, it probably has merit!


JB

#13 JulianB

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Posted 21 February 2013 - 11:39 PM

#4 and #1 are very related, need to give me a few hours to work that answer up.

Got a bit on with China right now also, so your going to have to wait 24 hrs.

JB

#14 Andrew P

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Posted 22 February 2013 - 12:32 AM

#4 and #1 are very related, need to give me a few hours to work that answer up.

Got a bit on with China right now also, so your going to have to wait 24 hrs.

JB


My interest was #1 and not production based.

PM sent

#15 facthunt

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Posted 22 February 2013 - 12:51 AM

what does a set of 29er foils retail at v a set of 49er blades?

#16 Reht

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Posted 22 February 2013 - 02:37 AM

29er vs 49er (at least in NA):
Daggerboard:
29er: $425
49er: $850

Rudder:
29er: $350
49er: $550

Just a little difference in price there. Though the 49er blades are pretty darn tough all things considered.

#17 JulianB

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Posted 22 February 2013 - 06:37 AM

Andrew, sorry if I got off the tangent already, this is very much a favorite topic. Spent yesterday covered in Carbon dust, re-modeling Trilogy's center foil, it’s got well out of shape and needed major adjustment.

So back on track:- #1 and with it a bit of #4

Very first point, by definition the Center-board and to some extent the Rudder are as equally as important as the rig. And just about no one takes anywhere as much notice of them as they should. They should also match the rig. By that I mean if you chose to run a fat sail set up, you should be running fat foils.

Second key point, Rudders tend to have a shorter cord than the Centerboard and therefore by definition has a different RE number and therfore by definition should be a different section even if they were doing the same job, which they are not.

Centerboard operates 99% of the time at +/- < 2° AoA and should be optimized for minimum drag at operating speed.

Rudder is a “balance” device, also a control device, its probably spends 80% of its time at +/- < 2° AoA but it also spend a some of its time at higher AoA and if you really ask it to turn the boat it had better bloody well stick. Rudders tend to be a higher drag device, not a lot, but a bit, they also tend to be bigger than they need to be. But that comes back to - “it had better bloody well stick”.

So we are talking I14 here, and that makes this job a whole lot easier, because it defines the max RM and it also defines the likely Average speed.

What it does not define is the speed out of the tack and that is pretty important.

Just coming back to the point here Andrew, you asked about the work we had done. There were 2 quite distinctive bits of work and in the end they reinforced each other. Both where empirical, one involved the 18teens, and I am talking about the GP 18teens, the other as you quite rightly referred to involved the 49ers, and that again was reinforced by a 29er study.

I’m going to cut to the case and simply make some statements based on those empirical tests and then justify them. This also may take a few days to get across, I welcome feedback and I have absolutely no doubt that some of it will be negative. Always has been, always will be.

So assuming you have a self-tacking jib, relatively efficient rig plan, all that general stuff, and assuming that your competent, etc etc, then the amount of centerboard area you need coming out of a tack to get going in what could be deemed a reasonable period of time is around 0.26 sq m, and once you get going you will need only about 0.128 sq m.

So putting this into perspective as a I14 has a very similar rig to a 49er, 49er has 0.315 sq m.

What a I14 does not have that a 49er does have is wings, so it’s down on horse power and therefore likely to be down on cruise speed.

Therefore it should probably be a tad fatter than a 49er and have a marginally higher AR.

Think a 49er foil is 1.1m in the water and 325mm Cord, running at 10.5% camber.

So logic would suggest that the I14 foil should be 1.05m in the water 290mm cord and running 11% camber, truncated ellipse, not at truncated as a 49er but similar.
And if you look at the other class that is very similar in size and power, the 16ft skiff, this is exactly what they have morphed to.

The factory I was grinding down Trilogy’s foil in yesterday was littered with 8-12” of the tops of 16teen foils, where they simply have cut off the top of the foil, because they were running with them up a foot for the whole year.

GTG, got a meeting will carry on tomorrow, I’m wifeless this weekend.

Just me and my 3 boys.

Julian

#18 Reht

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Posted 22 February 2013 - 06:20 PM

GTG, got a meeting will carry on tomorrow, I’m wifeless this weekend.

Just me and my 3 boys.

Julian


This'll be a good learning weekend. There goes studying for my classes...
Always a pleasure reading your insights JB! It would be interesting to hear what you'd change in the 9ers if you can completely free reign...

#19 JulianB

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Posted 23 February 2013 - 10:34 AM

Rent, thank you for your vote of confidence! I appreciate it.
A lot of people will tell you I'm talking crap, but I will leave that to you.

So, the reason I have been a tad long winded is, it should be obvious that once you get back up to a reasonable boat speed then all of us are likely to be carrying excessive foils area. The analogy to a aircraft is obvious, they deploy flaps and LE solts and all this other stuff to get off the ground but then once they get enough speed, they clean it up, reduce wind-age by pull it all in and then fly higher to get into thinner air.

The point I am trying to get across is you need "X" amount of area to get the boat going again after a tack, then by definition you need something like "X/2" or 1/2 that area once you get going again.

This all come back to AoA [Angle of Attack] Unless you use a gybing board or a flapped array, then your boat going up wind will Yawl! It will track a little sideways. Not a lot and we have got very good at measuring this, but it has to or you cant generate lift. Yes this is topic #4 but I wont go there just yet. The GP 18teens had a AoA or Yawl of less than 1d, 49er is about 1.25d, Just happen to be right at the edge of the bucket. More on this latter.

The next question is what is a acceptable level of yawl.

So to try and answer this question I have attached to file from the beloved NACA Theory of wing sections.

Couple of riders here, This book is 1 year younger than I am, Its got some age allowance, also Dad had long meaningful conversations with these guys, both as a pilot but also in the marine field. To cut a long story short, they are very happen to stand behind the book for all manner of Airplane applications but as soon as you use it for water which is 812 times as dense, RE scaling/error factors will completely off set any meaningful analysis. Hence our pre-occupation with empirical testing.

So what is of interest to me, and this has been borne out by full-size emperical testing on Tasar's 49ers, 18teens, 16teens, 5o5s and more recently 29ers is there is a very definite Bucket drag curve.

So what I am talking about is, WRT the 9% section, at .004 Section Drag Coefficient between approx +/-1d it sort of "flat lines" and with the 12% section you have a bit more room to move. The difference between a 1d and a 1.5d is 50%, so its a fair bit more room to move.

It looks a little like a bucket, hence the name!

Ok what is happening is at low AoA the board remains ostensible laminar flow, as you go to higher and higher AoA the board will start to go turbulent. This is not cavitation or ventilation, it is the layer of water directly against the surface of the board starts to form a roll. It most likely to start just aft of the max camber, propagate aft. Then at some stage move fwd, and as you go higher and higher it gets worse and worse until it stalls. If there is free air it may ventilate before this, but unlikely at the speed we are dealing with to ever cavitate.

Turbulent foil foils are great in that they can generate high CoLs, so coming out of a tack, perfect. But you pay a price of high CoD untill you come down in AoA and it literary snaps laminar! You probably have felt it and not know what it is, or passed it off as being in the groove.

Foils just like the sails have a groove, when your in it they feel great, when your out of it they feel sticky!

A Tasar foil is too flat, its about a 8% section. Gong up to a 11-or even 12% on a Tasar would make the boat come out of tacks fast, accelerate faster and give it a much better groove. Dont get me wrong, Tasar sails well and it compensates for having too flat a foil by carrying excess areas, which because its so thin is low drag (CoD) and they have developed very refined tacking system plus of-course they have a very low drag rig via over rotation. I also could be totally wrong, but I think if we did a Tasar again it would have a 10-11% section.

I have suggested that the I14 foil should be up around 11% that a educated guess, Given the boats parameters the boats around it and what they have morphed to it may be 12 or it maybe 10.5% but I am pretty sure it should not be under 10 and I think 10.5 - 11% is likely to end up being the sweet spot.

Andrew you asked about some of the tests we did and the refinements.

The 18teen tests where 2 fold, first I mentioned before about self tacking jibs as being important to foil size, In 1993 we chose to go the self tacking route, we tested our speed prior to that with these new fangled primitive things called DGSP, big, difficult, but what it showed was from a cruise speed up wind of about 11-12knts we dropped right back to 4 knts coming out of a tack, We did 2 things, first we analysed just about every aspect of the tack, things like easing the jib sheet 2-3" before you go into the tack, our movement through the boat, etc etc. And we then put on a self tacking jib, cleaned up the ergonomics, Cut a long story short, we where able to reduce our "loss of speed" to about 7Knts which in turn meant we ran a lot more often like the latter day 16teens with the foil up 6-9" and we found ourselves changing down rigs a lot earlier. We simply did not need the area coming out of the tack and in the lulls.

Yesterday a good friend of him, Noburo Ono (yes he is Japanese) gave me 20+ DVD of all those old 18teen bits of footage. Absolute treasure trove! Harry was watching a particular bit of footage where Brownie dump on us off Bardley's head, I bore away 4-5d probably, crack sheets a little and the boat accelerated straight through the bigger boats lee, as soon as we where ahead of his down wash, squeezed it back on again and climbed from beneath him to above his line and well in-front infact we made the mark, he did not. He simply had too much drag, he could not match us. I do remember it well. Dad standing on Bradley's talked of seeing the flash as we eased the sails and the sun reflected in a particular manner, and he when on busily measuring, as he always did, and then gave me a lecture after the event how I could do it better. But he saw exactly what happened and had it analysed down to a few minuets of a angle. (we won the race, the event and the series with one event to spare BTW,)

That was only possible because we had smaller more efficient foils and rig. It was infact the end of the big boat era.

The second thing we did with the 18teens, during that 10 year period we made or designed all but one of the 18teens (Trash Bag's boat was a Muarry) and we did make every set of foils plus virtually all the rigs. So often we would play with our own foils and also those of our training partners (Ella Bache mostly) WRT profile, camber and most importantly LE radius.

Bottom line is we where able to consistently lift our, and I hesitate to call it a CoL but its sort of a CoL as its a scaling factor, from 0.31 to 0.354 which again dose not seem like much, but it is infact a 15% increase (inversely a decrease in drag) and allowed us to reduce foil size even further.

This whole 18teen testing program, we have virtually replicated with the 16teen in recent years.

The 49er program came from this and from the 29er.

29er is milled extrusions, the huge advantage of milled extrusions is the consistency of the section. Very simply the 29er foil operates at a CoL (our scale) probably in excess of 0.4 and we where not prepared for that. Also its CoD was lower than expected, so as these things are always a compromise the sailor had little to gain by lifting the foil until much latter, which again we where not prepared for. It is true that we added 6" to the LOA of a 29er foil so a light person could get it up easily, but they don't seem to mind it.

Ok there are 2 bits I have left out, which is why 11% for a I14 beyond the educated guess and also what to do when you need only 1/2 the area when you up to cruise speed, that you need coming out of a tack.

Plus there is the 49er testing program.

That's tomorrows pontification if it keeps raining!

#4 come a few days latter.

JB

Attached Files



#20 Andrew P

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Posted 23 February 2013 - 12:46 PM

Julian

nice disertation,

agree on the bucket thoughts. The aim of this programme is to lower the drag coefficent but maintain the width of the bucket on alternate tacks without requiring the yaw slip to generate the lift. Achievable with the flapped board in theory.

Max loading on the cb is in 8 knots of wind at about 7.8 -8 knots SOG. At this wind speed the 14 is just fully trapped with in this case 175 kg total crew weight on a 6 ft beam. average crew height say 6 ft.

I have fiddled in 2D simulation with modifying the leading edge of the presently used Eppler 836 section, scaled down from design camber to 10 % and then added the asymetry via the flap to shift the bucket Col max out to the required level to cope with the low speed/start/tack manouvres.

Look forward to the next episode to get to the detail of the changes to see what can be done to lower CoD.

thanks for the images I'll look at them at the opi regatta tomorrow instead of pulling my hair out watching the daughter.

#21 Andrew P

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Posted 23 February 2013 - 09:06 PM

Julian

can you please expain your terminology of 1d & 1.5 d? Leading edge radii?



Can you expand on the CoL scaling factor as you call it. I presume its a measure of section L/d ratio, with the planform effects added in?

#22 JulianB

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Posted 23 February 2013 - 10:38 PM

Hi Andrew, 1d & 1.5d = 1° & 1.5° as in degrees yawl. I not smart enough to find the symbol section of this page. Should have written it in word or pages. (which I just did)

Our CoL, if you did not know Dad, he was more than anything a scientist, he was a consummate almost to the point of absurdity recorder of fact with which he then tried to make sense of the world. So you end up having all this very verifiable (which is why we went empirical early) data and a series of results. Otherwise known as FACTs! So we would make an algorithm of that data to match the results. To be honest I was better at this than Dad, (I'm more lateral) but once he got on a stream then stand back and watch him refine it. He would spend weeks in his study, into the wee hours, all long hand, if you have ever seen his hand writing is so small and so perfect so he could get it all in. And then came along Excel. In his mid 80s he was doing things with that program that I struggled with! Anyway, these where living breathing algorithms. So when data and results changed to an extent that the algorithm could not explain what we were getting, we had to change the algorithm. (Theory has to equal Fact, not the other way around) The only variable that we could change with merit was the CoL. When we did change it, everything else fell into place.

I know that will be frown upon by many, but we needed to explain a performance increase when everything else was fixed, so to speak. It was the only viable variable to alter. Those number probably are very close to what is achieved, just we have not developed a test to verify it, so I am not hanging my hat on it.


When we did the 49er on foils program, we where regularly achieving in excess of double the lift per unit of area that a Moth was achieving on our main lifting foil. So in the Moth's defence, it had a flap on the back and our array was a H foil, so we had near perfect end plates. But again, we had to alter the CoL to get our algorithm to equal the facts we where observing.

~~~~~~~~~~~

Yep, like your analogy of max load and your spot on, some would call this your "design wind". From that we can also work out working/operating load, (1.83m Beam x .5 (CL -> Gunwhale) + 1m(distance (approx) from your feet to your Centre of Mass) x Crew weight so you have 336kg/m RM

Assuming a I14 is very close to a 49er in Arm (http://9eronline.com...il dynamics.jpg)

Then you take 336 (RM)/4.378 (arm) = 76kgs side load, 49er has 95kgs, 470 for instance has 58kgs max side load

More on this when we get into #4.

~~~~~~~~~~~

Re Eppler 836, nice section, don't like hollows aft in lifting foils. and this was borne out by the 49er tests. They have a place sometimes in a rudder in some scenario's, but, and this is where it gets real interesting, this sort of section with an aft edge articulation, now that's interesting. Love to help. Actually been doing a lot of work on this over the last 3 months, Mostly non sailing related. And yeh, 10% is fine because as you articulate then the windward surface will go beyond 5.5-6% camber which is what you want (6% is a magic number, don't know why, it just is).

Again, and I stressed it when I gave you those 2 graphs yesterday, be very careful how the tests where done. The biggy is they are very different fluids, not just density and that one is wet and the other is not. The real biggy is one is compressible and the other is not. Talking about the difference between water and air here!

GTG, try and get back with your other answers tonight. But love articulation particularly the way you’re thinking of.

Go look after those Opie kids, far more important! I know it’s been aired in other places, but it’s also sad that the Opie is our lead-in class, tad un-inspiring!

JB

#23 BWR

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Posted 24 February 2013 - 02:31 AM

Great discussion guys, very much enjoying. Not understanding it all, but great to think about it.

#24 jimster

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Posted 24 February 2013 - 04:40 AM

The Eppler 836 is very popular for windsurf slalom boards these days too , typically scaled to around 10-11% t/c . It can be driven really hard as long as speed
is kept up to pump that big roof . The nicest feature is the benign stall with a little growl warning of onset ... post-stall reattachment is good too . Some guys dick
with the LE radius - I don't know if there is a consensus mod .

#25 Rohanoz

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Posted 24 February 2013 - 06:14 AM

The 'cavitation'/stall is the thing with rudders.

The fastest and lowest dag rudder in the world, turns to being a piece of shit the day you lose a race cause you spun out!

#26 JulianB

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Posted 25 February 2013 - 07:39 AM

Re different cambers. Two competing forces, and an envelope of best fit between the 2.
Once up to speed there is a optimum camber for an expected boat speed. Very simply the faster you average speed is the thinner you would make your centreboard. It pretty straight fwd, it a Lift/Drag ratio. If you expect to be cruising around at 5-7 knts which is a Tasar and 470 speed then you should be opting for a 11-11.5% section.
[Interestingly neither of those boats do that, they opt for excessive area instead which will really cruel their top speed]
Go a bit faster then you come down in % camber for 2 reasons, the penalty at top end speed become more apparent and the lowest speed in a tack is higher so you don’t need as much camber to get going again.
49er has a cord of 335mm and a max thickness of 34mm, almost exactly 10%.
29er has a cord of 320mm and a constant thickness of 32mm, again 10%.
29er should really be up around 10.5% but it pretty hard top tapper a extrusion, plus we made it bigger so light kids could get it up after a capsize, so it balanced out.
It has been very interesting to see the 16teens go through this whole evolution. In the late 90s I help a near known group of sailors with their boat, the centreboard was huge, 12-13% and a long way aft in the boat. I remember and was reminded of this only a few days ago that I said do this and do that, it was a 10.5% foil, we cut almost 18” off the top and we moved it fwd over 1 foot (325mm), Cutr a long story short, they went on to win the Nationals, and the rest followed.
But it has been a interesting transition, as I commented before, when grinding down Trilogy’s foil the place was littered with tops of centreboards because long after I had come and gone, they are still evolving.

The other competing factor is obviously a big fat foil will stick earlier coming out of a tack. So if that was the only factor then a 49er foil should be fatter than a I14 foil. Because of the wings a 49er can load up the foil out of a tack more than a I14.
So now we get into ergonomics and technique. And this is the reason why we can get away with thinner foils, and thinner foil = higher top end speed.
How you tack the boat is so important to getting back up to speed, not just self tackers, easing the sheet before the tack, not a lot, 2-3” on a 49er is all it takes to exploit the Circular air flow principals [HPS2 page 334]. Both the 29er and 49er decks are design to be ergonomically sympathetic, its easy to take them but it also easy to mess it up.
This all started with the 18teen called Looney Tunes, we went to solid wings, The difference between having to think where you where going to put your foot and knowing you could put you foot anywhere and know you would not go down the gutter and when you put your foot (on a solid wing) it was just that, Solid! One less thing to think about, more time to get other things right. It all adds up.

The other issue is structural, thin foils need a lot of material to make them structurally sound and they need to be longer which again increase structural issue within the boat.
Shorter fatter foils are lighter, stronger and once up to speed, if they have been design well will have a higher CLR and therefore you will be able to convert more of your RM into fwd drive.
~~~~~~~~~~~~~~~~~~
49er tests.
Early in the life of the 49er, people played, they with everything and foils where no exception.
The Europeans where pretty big on fattening the foils up, making them very bull nose, straightening the aft sections, going closer to a classic 0010 section, Technically illegal but what can you do.

It soon became apparent that we need to do something to stop this, so in true Bethwaite fashion we did do a series of empirical test, and the people who did the test, often did not even know they were party to it.
These test mimicked the old 18teen tests with AAMI, Ella Bache and Old le Passo.
You can do a lot within a layer of gelcoat, LE radius can be altered significantly, you can pull cambers fwd, especially with 2-3 layers and you can also clean up longitudinal irregularities.

The results were quite predictable, LE radius and detail are 90% of the battle, fatter section just aft of that will develop more lift at low speed and attach sooner (ie coming out of a tack) but also are quite limiting at higher speeds. Difference is stark flat out, could be as much as 2 knts.
We did not (could not) alter profile and therefor area. That development has really come from the 16teens. Also all of this ideology has been transfer to countless other classes, including OMR multihulls, Trilogy and the alike, and yachts. Every time with an improvement.
Anyone can go measure a 49er foil, but when we went to re-design the foil, it was in fact very close to the original, a 1.5% LE radius at the root (near the keel line) Elliptical front 45% of the foil with a simple circular arch aft of that, 1- 1.5mm TE. 10% camber at the root, tapering to 6% at the tip. Lot of attention to the transition. From LE to the front section and also around the tip.
Lots of care was taken to ensure that everything was very fair, and then we pumped out 3 sets of identical matched alloy moulds at one time from one source, and they are still in use today and probably will be for the next 20 years.

Re what to do when you have approx. double the area you need when you get up to speed.
Just go copy the aircraft industry, you tapper the wings and you tapper them hard.
You don’t go under 6% because then you get into un-stability and flat plate drag issues.
If you go faster, then you use smaller foils and tapper them latter, because it harder for the positive pressure to get around to the leeward side before the board has advanced a cord or 2 lengths (classic vortices stuff), if you go slower you use a longer foil and tapper it earlier.

#27 cantp1

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Posted 25 February 2013 - 10:21 PM

Anyone can go measure a 49er foil, but when we went to re-design the foil, it was in fact very close to the original, a 1.5% LE radius at the root (near the keel line) Elliptical front 45% of the foil with a simple circular arch aft of that, 1- 1.5mm TE. 10% camber at the root, tapering to 6% at the tip. Lot of attention to the transition. From LE to the front section and also around the tip.
Lots of care was taken to ensure that everything was very fair, and then we pumped out 3 sets of identical matched alloy moulds at one time from one source, and they are still in use today and probably will be for the next 20 years.


So did you re-design the 49er foil because sailors were getting better at coming out of tacks / sailing in the groove or to help increase the top end speed? Empirically what type of top end speed advantage did the new foils bring to the 49er?

It is sometimes quite noticeable the speed difference when a well sailed boat with old foils lines up against new foils in quite light airs. The old foils are a bunch quicker upwind... :) I'm going to be using an old style boat for the first few events of the 49er.ca GP season...!

#28 IC Nutter

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Posted 26 February 2013 - 03:06 AM

A while ago I was discussing issue of foil area on another forum. Often the foil area is expressed in terms of sail area and there are some rules of thumb used to determine ballpark figures (e.g. 4% of sail area is a common figure used), but with little justification. I decided to look at the maths and determined that for given lift coefficients for the foil and the sail, the determining factor is the boatspeed/windspeed ratio.

To add weight to what Julian is saying about foil area being a function of boatspeed, the attached plot shows how the required foil area varies with boatspeed for one set of CL values.

Attached File  FoilArea.png   62.32K   97 downloads

#29 FishAintBiting

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Posted 26 February 2013 - 05:42 PM

Julian,

Out of curiosity - how much attention did you pay to the water temperature?

If I understand things correctly the kinematic viscosity of sea water changes by roughly 30% when going from 10ºC to 20ºC. Would you alter the design if you knew vaguely what the water temperature would be?

Happy sailing,

Fish

#30 JulianB

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Posted 26 February 2013 - 11:25 PM

Craig, great graph, and that would be borne out by Vesta also, lots we will learn from that. Great line(s) in the latest SeaHorse (April 2013) by Larsen, goes something like " ~~~ the philosophy of "big is better" was not the way to I thought it should go. Big boats costing stupid amounts of money to campaign when there are more elegant solutions"
The last 3 words are the key, more elegant solutions

Fish, to the best of my knowledge, and again its a co-opinion with Bora Gulari is that its not till you approach 4c that things go wonky. So at 10c you will start to see the effects of the state shift that happens in water at 4c, getting progressively worse as it gets colder. The thing you have to do is create surface roughness fwd on a foil to get it to stick! On a moth that was a roughening up with 80g sand paper from 5-15% back from the LE of the foils.

Interestingly when I had this conversation with Dad he said, yes its called "xyz" (cant remember the name but its in another post on SA few years back) because they had it with the step on a flying boat. Same issue.

By the time your at 12-13c then it will be similar to water all the way up to 24-25c.

#31 FishAintBiting

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Posted 27 February 2013 - 06:24 AM

Julian,

Thankyou for your time to respond. It is appreciated.

Fish

#32 pcraig

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Posted 27 February 2013 - 09:32 PM

My understanding of the temperature issues, were that as you approach the change of state of water, the viscosity rises dramatically. As the viscosity increases, the laminar boundary layer thickens. A thick boundary layer is draggy and therefore there comes a point where it is more efficient to be operating in a thin turbulent boundary layer. The roughing up of the leading edge will trip the flow from laminar to turbulent. 5-15% tends to be the optimum region.

#33 JulianB

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Posted 28 February 2013 - 09:59 AM

Mr Craig, I have the good fortune of never having to have ever sailed in water anywhere approaching 4c other once when I stupidly took a Phase 2 for a sail (pre runner to teh Laser 2) in Montreal, and it promptly sank, I was a tad more concern about getting back to the shore as I was out in a tee shirt and short.

The sort of thing you would expect a 20 year old antipodean to do in Canada. Very young and stupid!

#34 couchsurfer

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Posted 28 February 2013 - 04:44 PM

Mr Craig, I have the good fortune of never having to have ever sailed in water anywhere approaching 4c other once when I stupidly took a Phase 2 for a sail (pre runner to teh Laser 2) in Montreal, and it promptly sank, I was a tad more concern about getting back to the shore as I was out in a tee shirt and short.

The sort of thing you would expect a 20 year old antipodean to do in Canada. Very young and stupid!


....mmmm,,you refer to the 'frozen-nutsack' factor of canadian sailing and design :mellow:

#35 BalticBandit

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Posted 28 February 2013 - 08:56 PM

Craig, great graph, and that would be borne out by Vesta also, lots we will learn from that. Great line(s) in the latest SeaHorse (April 2013) by Larsen, goes something like " ~~~ the philosophy of "big is better" was not the way to I thought it should go. Big boats costing stupid amounts of money to campaign when there are more elegant solutions"
The last 3 words are the key, more elegant solutions

Fish, to the best of my knowledge, and again its a co-opinion with Bora Gulari is that its not till you approach 4c that things go wonky. So at 10c you will start to see the effects of the state shift that happens in water at 4c, getting progressively worse as it gets colder. The thing you have to do is create surface roughness fwd on a foil to get it to stick! On a moth that was a roughening up with 80g sand paper from 5-15% back from the LE of the foils.

Interestingly when I had this conversation with Dad he said, yes its called "xyz" (cant remember the name but its in another post on SA few years back) because they had it with the step on a flying boat. Same issue.

By the time your at 12-13c then it will be similar to water all the way up to 24-25c.


Julian in one of these threads I remember running the numbers, and the threshold for moths is around 4oC but a lot of it depends on the radius of curvature as to wherre the threshold is (and a bit on whether it is salt or fresh) as well as the velociity that the foils are travelling at. Basically because the issue is whether or not the viscosity/fluidity is below the threshold of how fast the water has to re-accelerate back towards the foil aft of the max thickness. (so shape also matters a bit)

#36 Speng

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Posted 28 February 2013 - 09:55 PM

Yes I am here.

3 completely different issues at play here.

#1 Is the most efficient profile, and then section and then % camber which includes LE radius of a Centre board and then all that again for the Rudder, because by definition they should be different. And again this is for a given boat.

#2 What is more cost effective, extruded alloy foils or infused FRP foils included in that longevity, maintance etc etc, into this comes long term supply issues and the class changing rules Etc Etc.

#3 Is should there be a progressive technology process in a OD class.

So to not go way off on tangents, which do you want to talk about first?????

JB


Julian,

Regarding #3: Having been a 29er owner in the past one of the things I appreciated about the metal foils is their absolute ruggedness and I'm not sure that there's another way out there that could achieve that other than metal. Please correct me if I'm wrong. I suppose too that since a 29er is a trainer that the boat can't be so optimised for the expert crews who can flick thru tacks etc that the 14 y.o. neophyte can't handle it. I must say that the first time I pulled off a gybe on the boat that me and my skipper were so amazed it went so well that we capsized because we were congratulating each other. I imagine though that going to something other than an extrusion would allow for a non-rectangular planform, taper etc that would likely result in a more hydrodynamic foil? Perhaps hydroforming or whatever it is that Rolls-Royce uses to make the hollow turbofan blades might be better/cheaper.

What airfoil sections does a 29er use? My recollection is that they were pretty normal and the c/b was pretty thin. I guess a lot of designers still use the pre-war NACA sections but I'm a big fan of the ones they (NASA) developed in the 70's and early 80's along with the modern ones from guys like Eppler, Roncz etc. Better designs for boat-y Reynold's numbers and they had greater design thicknesses so you can have a slick, fat foil that you can stuff some structure into. Does using an extrusion limit what sections you can use (e.g. no hollow sections etc)?

Personally I think that the rig is the low hanging fruit on the 29er though as the mast is a bit of a telephone pole. I reckon a 49er-esque rig might bear more fruit in pace and usability than foils, but as you point out rigs and foils go together so if you're going to redo the foils you might as well redo the rig as well :lol: . On the 49er does the new carbon rig take as much rig tension as the old rig? If it's less that might be another reason to go that route.

I'm no longer one of your constituents (unless the 59er gets brought back) so the input's not so relevant.

#37 Speng

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Posted 28 February 2013 - 09:57 PM

My understanding of the temperature issues, were that as you approach the change of state of water, the viscosity rises dramatically. As the viscosity increases, the laminar boundary layer thickens. A thick boundary layer is draggy and therefore there comes a point where it is more efficient to be operating in a thin turbulent boundary layer. The roughing up of the leading edge will trip the flow from laminar to turbulent. 5-15% tends to be the optimum region.


Not to mention that whacky density change...

#38 JulianB

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Posted 28 February 2013 - 11:07 PM

Re 29er foils. Totally agree they are stupidly tough and I think they are a great concept.
The other thing that I pointed out earlier in this thread, is when we first put the foils on the boat, they out performed their "spec" both in terms of CoL and CoD.

Section is same as a 49er, only we went a tad thinner than we would normally do because we used a tad more area (so light weight could get the boat up), so in fact its virtually a identical scaled mirror of a 49er, same % camber, etc tec,

By way of explanation, a 29er should technically a little fatter in terms of % than a 49er, because it goes a bit slower (most of the time) but because we used a bit of extra area, so the light kids could get the boat up, we compromised. They are both about 10.15%.

2 interesting side points,
a) max speed I know of a 49er going (not on foils) was 26.7 knts, Max speed I am aware of a 29er going is 32.4knts.
B) when you pull a 49er foil up, when its fresh its in the order of 2-6" 50-150mm, when you pull a 29er foil up for the same reason its a 10" - 1ft.

And 3 things are working against all alloy products, be they foils, or masts or booms of what ever.
i) alloy uses a lot of electricity in its manufacture and we have seen significant prices rises and will continue to do so.
ii) The big alloy maker have been brought out by even bigger companies, so the expertise to press hi end alloy is reducing to a few, which has price consequences.
iii) Regulations around the worlds as to composition of material like Poly-urethanes is tightening up, and they don't stick any more. So it becomes more complicated to put in end plugs.

Bottom line, it just costs more.

I did write a #5 to this whole string which also alludes to the inevitability of the switch from alloy foils and the 29er alloy mast to FRP, so Speng, your right in my opinion for what it is worth. As to if it will happen, yes, if you use hi tech alloys then in the next 5 years. Low tech alloys 15 years.

Not so sure there is that much to be gain from tapering the foil hydrodynamic, as I said before the 29er operates above spec already, so if there is a gain it will be limited to it will be a lot easier to get the board down the case.

Jb in a very wet SYD

#39 Reht

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Posted 01 March 2013 - 01:59 AM

Mr Craig, I have the good fortune of never having to have ever sailed in water anywhere approaching 4c other once when I stupidly took a Phase 2 for a sail (pre runner to teh Laser 2) in Montreal, and it promptly sank, I was a tad more concern about getting back to the shore as I was out in a tee shirt and short.

The sort of thing you would expect a 20 year old antipodean to do in Canada. Very young and stupid!


Any idea where it sank/was it retrieved? Would be funny to go hunting for it (turns out there are a lot more boats down there than one would expect).

#40 facthunt

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Posted 01 March 2013 - 02:09 AM

32.4 kts now theres a challenge for all you 29er sailors.
next nuclear weather event is calling.

#41 Reht

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Posted 01 March 2013 - 02:25 AM

32.4 kts now theres a challenge for all you 29er sailors.
next nuclear weather event is calling.


To get that far you gotta also get a little lucky in that nothing breaks or slips. Though I'm curious what conditions it was done in and whether it was with or without the spin. When I was sailing 29ers there were a few guys around claiming that over 25knts (or something like that) it was useless putting up the spin (something about adding more drag than anything else). I never got a chance to confirm that, anyone ever tried?

#42 Rohanoz

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Posted 01 March 2013 - 07:03 AM

Yeah, I'm a bit 'huh?' on the 32.4kt claim!!!

JB has achieved more than I could ever aspire to, and is one of my sailing 'heroes', but getting a 29er above even 25kts is just something I can't believe.

25-30kt NEr at Belmont Nats this year, one of the top Cherubs hit 25.4 - and that is about the limit for a boat with half the weight and same sail area!

#43 facthunt

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Posted 01 March 2013 - 09:27 AM

did it blow his hair off

#44 Speng

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Posted 01 March 2013 - 03:20 PM

Not so sure there is that much to be gain from tapering the foil hydrodynamic, as I said before the 29er operates above spec already, so if there is a gain it will be limited to it will be a lot easier to get the board down the case.

Jb in a very wet SYD


I was thinking about mentioning how hard it was to put the boards in but I didn't want to come off as a whinger :lol: .

I think most of us would be interested in understanding the balance between material cost and building (labor etc) cost for a Aluminium foil vs a composite one. Based on the price comparison between a 29er and 49er board there might be some time yet until that is an issue. Maybe a "green" approach would be to require each person who wants to buy and Aluminium board to send in enough old cans etc to build new one?

I reckon the 32.4 on the 29er was on a nuclear 2 sail beam reach with a couple fatties on flat water. Kinda like how you can take a Hobie 16 out in stuff that an F18 wouldn't even consider.

#45 JulianB

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Posted 03 March 2013 - 02:25 AM

Hi re speeds, I was not there for either.

To the best of my knowledge,

The 49er record, was done with GPS off Neilsen Park in SYD harbour with Emmett Lazich and Cam (caveman) McDonald yes with a spin on, in a fresh southerly.

29er record, was done is southern USA, cant even tell you whom but again by GSP track and their track and the reports where such that I give it credence.

What I can tell you is that I was driving a StFYC protector, with about 6 people on board including Janet Baxter who at the time was the Pres of US Sailing, we where taking photos, we where tracking about 10-12th place, gold fleet 2004 29er Worlds they where on a leg from StFYC to Alcatraz, think it was a Norwegian brother and sister combination and we where doing 25-26 knts on 3 instruments, I remember Janet's face! And these kids where sailing away from us, and again, the 1st and 2nd place (also girl boy teams) where sailing away from them.
Yep spins on.

Got to remember the definition of a skiff (ISAF) is it sails faster than the wind most of the time. Its all about Apparent wind sailing.

When life slows down just a tad, what I would dearly love to do is have a quarterly challenge, get people to send in their fastest run, any run for that matter via Velociteck or what ever, fastest speed, we get special "legal" speed fanatic" spins made with there speed in the clew and that's their reward.

Need to work that out, and I dont have the time right now. But we are good enough to look at a plot and work out if its fabricated or not.

Do it for 49ers, FX and 29ers,but I can tell you right now, 29er will be the fastest, followed by the FX and then the 49er. 49er will always win around the track but pure burst speed, 29er will eat it.

~~~~~~~~~~~

Re 29er foils. Already we get sails single sourced, and we also get masts (49er and FRP lamianates) single source. If you get quantities up enough, you can invest.

We have already seen significant reductions in cost of sails and spars. We already have quotes from ARG, ESP, IND and CHN which would suggest similar quantities of scale are possible with foils.

49er foils are precision custom made and A+++ product. Its one of the bain's of being a Olympic class. The 49er sailors are demanding and they get costed accordingly.

A 29er foil dose not need to be that and if we, get volumes up, switch from Epxoy to Vinyester, switch from PVC to PET foams, or even purpose blow, but pre baked PU foams, and you alter laminate schedules they its amazing how quickly these costs come tumbling down.

For instance, go high temp pre backed PU cores, and go to Nickel plated moulds, cure temps go from 50-80 C to 80-120c and cycle times go to 2-3 per day rather than one. Plus the cost of the moulds is dramatically reduced. The quote we have for Nickel plated 29er moulds is 20% of the milled alloy moulds we have for the 49er.

This product would be at-least a A+ product. If you knew what you where looking for, yes you could fault it, but a quick wet & dry plus a polish and it would be faultless.

At present we are about 10-11% above the alloy figure. But as sure as today follows tomorrow, the cost and complexity of all alloy products, be they Snipe masts or 29er foils will march for ever upwards and RMT/Infusion will continue to decrees.

Julian

#46 Reht

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Posted 03 March 2013 - 10:55 PM

Hi re speeds, I was not there for either.

To the best of my knowledge,

The 49er record, was done with GPS off Neilsen Park in SYD harbour with Emmett Lazich and Cam (caveman) McDonald yes with a spin on, in a fresh southerly.

29er record, was done is southern USA, cant even tell you whom but again by GSP track and their track and the reports where such that I give it credence.

What I can tell you is that I was driving a StFYC protector, with about 6 people on board including Janet Baxter who at the time was the Pres of US Sailing, we where taking photos, we where tracking about 10-12th place, gold fleet 2004 29er Worlds they where on a leg from StFYC to Alcatraz, think it was a Norwegian brother and sister combination and we where doing 25-26 knts on 3 instruments, I remember Janet's face! And these kids where sailing away from us, and again, the 1st and 2nd place (also girl boy teams) where sailing away from them.
Yep spins on.

Got to remember the definition of a skiff (ISAF) is it sails faster than the wind most of the time. Its all about Apparent wind sailing.

When life slows down just a tad, what I would dearly love to do is have a quarterly challenge, get people to send in their fastest run, any run for that matter via Velociteck or what ever, fastest speed, we get special "legal" speed fanatic" spins made with there speed in the clew and that's their reward.

Need to work that out, and I dont have the time right now. But we are good enough to look at a plot and work out if its fabricated or not.

Do it for 49ers, FX and 29ers,but I can tell you right now, 29er will be the fastest, followed by the FX and then the 49er. 49er will always win around the track but pure burst speed, 29er will eat it.

~~~~~~~~~~~

Re 29er foils. Already we get sails single sourced, and we also get masts (49er and FRP lamianates) single source. If you get quantities up enough, you can invest.

We have already seen significant reductions in cost of sails and spars. We already have quotes from ARG, ESP, IND and CHN which would suggest similar quantities of scale are possible with foils.

49er foils are precision custom made and A+++ product. Its one of the bain's of being a Olympic class. The 49er sailors are demanding and they get costed accordingly.

A 29er foil dose not need to be that and if we, get volumes up, switch from Epxoy to Vinyester, switch from PVC to PET foams, or even purpose blow, but pre baked PU foams, and you alter laminate schedules they its amazing how quickly these costs come tumbling down.

For instance, go high temp pre backed PU cores, and go to Nickel plated moulds, cure temps go from 50-80 C to 80-120c and cycle times go to 2-3 per day rather than one. Plus the cost of the moulds is dramatically reduced. The quote we have for Nickel plated 29er moulds is 20% of the milled alloy moulds we have for the 49er.

This product would be at-least a A+ product. If you knew what you where looking for, yes you could fault it, but a quick wet & dry plus a polish and it would be faultless.

At present we are about 10-11% above the alloy figure. But as sure as today follows tomorrow, the cost and complexity of all alloy products, be they Snipe masts or 29er foils will march for ever upwards and RMT/Infusion will continue to decrees.

Julian


Interesting, so I assume the top speed all comes down to drag, smaller hull and rig on the 29er means more drag, and you can always add more wind... I do like the idea of custom spins for the fastest, or even have an option to order a kite with your top "verified" speed once you've submitted. Then anyone can show off their top speed, there's always people who will never even be close to the top speed in their respective boat, but are at least as proud of their top speeds as any of the guys who have the "record"...

One thing that I really loved about 29er foils that I now miss sailing a 49er and contender is that you could not crack an alu foil. The 49er foils if you slip off and catch your trap hook or even if you aren't careful getting on the board post-capsize, you crack the trailing edge. It's not a hard repair, but for a youth class it's one more repair that you have to deal with (and you'll probably have to deal with on a regular basis), just a case of keeping the boat as simple as possible.

#47 mustang__1

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Posted 04 March 2013 - 01:03 AM

not to mention the deck of the 29er being none too kind to foils. Imagine beach launching in a surf and having to get the foils out of the pelican case on shore instead of having the foils laying down in the boat ready to go. There's no way i can see letting shiny glass foils lay down on the grab rails and all that other nasty stuff. I still think changing the rigs would be the biggest problem, though. Given that a new set of sails already runs $2800us, and a complete aluminum rig already runs $2500, you are already looking at a replacement cost that is worth more than a lot of the boats currently on the used market. Given the current rate of inflation on sails i see the cost of sails at the least going to be around $3300 by 2017 given that in 2009 they were $2300 if i recall. The end game that i see happening is the old boats not being competitive with the few people who buy a new boat with a new rig, and the new boats not really having anyone to race against. I remember a couple years ago i brought up adjustable turnbuckles and the argument against it was that they were too complex for what was suppose to be a youth boat. Now we're talking about new foils, new rigs, and new sail plans... for what is supposed to be a youth boat. Im no longer a youth - but im not made of money, either. I just dont envision people wanting to shell out the money to retrofit the boat. The top guys who are going to worlds etc every year probably wont have an issue or even want it, but i dont think that represents the majority of the class.

#48 facthunt

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Posted 04 March 2013 - 02:11 AM

its a hard call, i think both 9er boats are in a performance market niche, and the boats of today perform way better than they did when they were released, boats like these need to be developed to keep pace with the general state of play, i think they are a little behind but the responses seem to be carefull and measured.

if you dont like something you can vote with your feet, i think this brands strength seems to be its ability to walk that fine line, i suspect the theres a lot more political tweeking than boat tweeking keeping these products on the rails.

#49 JulianB

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Posted 04 March 2013 - 04:27 AM

As you have brought it up.

I expect a decrease in the cost of sails once we go to Chinese based cloth.
I also expect a increase in longevity because we will be able to custom design cloths for specific needs.
I expect that one of the triggers of going to a FPR/Carbon mast will be cost.
I wont do it unless the FRP/Carbon mast has significant increase in longevity.
And foils, the laminate we are trailing now on the trial 29er foils (1 is in Scotland, the other here nth of SYD) is significantly heavier than a 49er, plus trapezes hooks still dented the alloy foils. Again, cost of the alloy foils is rising, cost of the FRP foils is dropping.

Yes alloy foils ARE a great idea, they remain so, but they are thin walled which is why they weight only 125% of their bigger 49er cousin and they have their own issue.

No reason why a set of alloy foils cant sail against the set of FRP foils, they have to be the same section where it matters, by definition, the hole in the boat is just so.

Watching a girl/boy team out yesterday in a fresh 20knts with lots of lump, assure you we will not be going any bigger in sail area.

And to finish off, the politics is within the sailors, not us builders. Very easy for us to sit on our hands and continue to supply products that where once "best practice" but the test of time has marched onwards which has made them wanting. Sailors and particularly Coaches then go and torture the existing piece of equipment to make it do what it was never designed to do.

As we speak a new sail material is being tested and will probably be turned into a very pre production prototype 49er set of working gear, that I expect to be cheaper and last longer than the existing material.

Just prior to the 2000 SYD games a 49er Spin was approx $2000 inc AUST GST (10%). Today Ovington sells a 49er spin for GBP 1339.96 inc VAT (20%) That = $2014.96.

Sure, ex-change rates are in there, al-sorts of comings and going, but we have done a good job. A 49er jib in Australia today is only just getting to the late 90s prices.

I expect this new foray, which, BTW I fund completely myself along with Maka and Neil Pryde will again restrain the cost of re-kitting a 49er. If it works, then I would hope to pass that on the the 29er.

But that is all up to the sailors, and the class, all I can do is say no!

Lucky I have very thick skin!

JB

#50 Reht

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Posted 04 March 2013 - 04:34 AM

not to mention the deck of the 29er being none too kind to foils. Imagine beach launching in a surf and having to get the foils out of the pelican case on shore instead of having the foils laying down in the boat ready to go. There's no way i can see letting shiny glass foils lay down on the grab rails and all that other nasty stuff. I still think changing the rigs would be the biggest problem, though. Given that a new set of sails already runs $2800us, and a complete aluminum rig already runs $2500, you are already looking at a replacement cost that is worth more than a lot of the boats currently on the used market. Given the current rate of inflation on sails i see the cost of sails at the least going to be around $3300 by 2017 given that in 2009 they were $2300 if i recall. The end game that i see happening is the old boats not being competitive with the few people who buy a new boat with a new rig, and the new boats not really having anyone to race against. I remember a couple years ago i brought up adjustable turnbuckles and the argument against it was that they were too complex for what was suppose to be a youth boat. Now we're talking about new foils, new rigs, and new sail plans... for what is supposed to be a youth boat. Im no longer a youth - but im not made of money, either. I just dont envision people wanting to shell out the money to retrofit the boat. The top guys who are going to worlds etc every year probably wont have an issue or even want it, but i dont think that represents the majority of the class.


Much could have been said similar with the 49er class as it transitioned. I got an old boat and to upgrade the rig cost me as much as the rest of the boat (and that was buying a used rig and sails). But to say they'd be noncompetitive, that might be a stretch. I was sailing a 49er in about 15-20knts with an old rig, old foils, and it was the first time my skipper and I had sailed together (and we were both pretty new to 49ers). We hung in close to the back end of mid fleet, not shabby.

The foils are exceptionally convenient on the 29er, and unless the price was to drop to get the "new" foils, I don't think it would be welcome with the mid to back end of the fleet (where most of the long-term 29er sailors are). Same with the mast. But provided (as JB pointed out in the post he got in while I was writing this) the foils are the same section, the sail area remains basically the same, you'll see that "old style" boats will be just fine for the average sailor. If the longevity of the parts remains constant or improves, and the cost for replacement sails/spars remains steady or decreases, then slowly the sailors will change as they have done in the 49er. You break something, you'll replace it with the "new style" part, slowly but surely the old stuff gets replaced. Of course there will always be that part of the fleet that ends up sticking to the old equipment, but they probably weren't serious about racing so much as going out and having fun...

#51 mustang__1

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Posted 04 March 2013 - 05:17 AM

yeah sorry JB, i tend to get a little heated sometimes. If the prices are truly going to drop for the end user, i would be swayed a little bit. Even so, it was a big deal for me to shell out for a new jib and kite this winter to replace my heavily used sails from 2009. My race main is almost new. I recognize that exchange rates have a lot to do with it - so perhaps the $600 increase in sails since 2008 was in-part exchange rate related - i dont know those numbers offhand.. As far as sails are concerned - i would expect that at least the current production mains would not fit the new carbon masts? I think you had also mentioned going squarehead? I realize you dont really get power from the squarehead, but i would expect there would be a speed advantage between two equally skilled teams. I also suspect the jibs would go to a zipper luff but i doubt there would be much performance gain. But, would they fit or would the mast geometry be changing? I would hope that kites stay the same. I mean, i wish it was masthead or at least bigger overall - but it would be a chance to save a few dollars. Either-way, most of these changes wont effect me since i dont expect to stay in the class after NA worlds (which im hoping to buy a new boat for vs chartering. hello loans!), but i want to see the 29er succeed because it truly is, imho, one of the best youth or little people's boats out there. Anything to get american kids out of c420;s...

#52 JulianB

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Posted 04 March 2013 - 09:28 AM

The issue re making the old sails fit a new mast is this.

Anything is possible, and as you get down to the last 1mm in luff round, it is also possible but it gets more and more labour-some.

So do you build a new mast the most efficient way you can, with tapper layers doing specific jobs to ensure a mast with longevity and a good action.

Or do you bastardise it so it works well with a old main.

The answer to that question is pretty obvious.

~~~~~~~~~~~~~~

Square head, now this gets interesting. Perception is a wonderful thing.

You would expect a square head to be more powerful up top, to make bearing away at a top mark harder and to be in general, more difficult.
For what ever reason the inverse is true.

Mush easier to pull away at the top mark, they power up and power down more fluidly and effectively, and when you get over powered, they blade off and behave better.

So by going "square head" we can dramatically widen the "sweet spot" while making the boat look cool/modern.

One has to take your hat off to Chris Cairns, the Tornado guru who first pursued this line of attack. I thought he was mad! He proved me wrong.

The other thing we can do re square head is play with the ratio's. All critical ratio's that ended up a tad askew with the 29er.

I get a dry run at all of this with the Tasar, and that's another story. Going to NZ next week to pursue this, its 3 - 4 year project.

Julian

#53 couchsurfer

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Posted 04 March 2013 - 06:34 PM

.......thanks JB,,it's really interesting to hear about the details involved in keeping the 9er classes evolving! :)




..................too bad laser doesn't take a similar approach!!! <_<

#54 mustang__1

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Posted 04 March 2013 - 08:44 PM

yeah i can totally see changing the main - thats pretty easy to justify. but, what about jibs and kites? say you have relatively new sails, if all you have to throw out is the main then you cut down on the costs of upgrading significantly. I realize that technology has improved a lot, especially in spinnakers, but money is money...

#55 Reht

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Posted 05 March 2013 - 12:43 AM

The 49er seems to go just fine with an old-style jib on a new rig. The new jibs are just so much more convenient with the zipper. The spin is another issue, less so with the 49er as the top teams are rolling through a few a year and selling them out on the second hand market incredibly cheap considering they've been through maybe a handful of regattas total. I figure if/when the 49er changes spin it'll take a whole year before basically everyone has a new style spin (everyone being those who race regularly and thus already have the carbon rig, etc). Though it might turn out that in certain conditions the old spins are faster, you're going to have a messy overlap period where top teams try to hold on to lots of old spins (unless you ban them nearly immediately upon releasing the new ones).

The 29er is a different class, but I'm sure some parallels can be drawn...

#56 JulianB

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Posted 05 March 2013 - 05:48 AM

When we did the new rig, it was designed so the existing spin and the jib would still, and still do fit. Exactly as per Reht's comment.

As time has gone on, you still see a few old style jibs but not many.

Gold fleet was mandated to use the new gear, so the exchange burden was borne by the rock stars, but that being said, as I mentioned before we sold something like 450 rigs in 6 months. There are not 450 rigs worth of rock stars so the Weekend Warriors also brought into the new package.

The big driver on the spin is the FX. The boys don't like the idea of been beaten by the girls.

The current 49er spin is now 17 years old technology, and the boat is going at least 2-3 knots faster downwind, so its also inevitable it will be switched.
Surely the industry has learn something in that time.

And plans are afoot, being done by the class and the sailors, as it should be, I still just get the right to say NO, if I wish, and there are a few requesting I do so. Regardless the decision will be made well before Brazil, but the actual switch (if at all) will be after the games for very obvious reasons.

#57 SimonN

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Posted 05 March 2013 - 08:13 AM

Having been through the change from alloy to carbon spars in 4 different classes, including 2 of Julian's (B14 and 49er), I can report that in every case, a fair number of people expressed huge concerns and predicted it would hurt the class and in each case, it hasn't. In addition, I am pretty certain that the classes involved, if they could have the time again, would go down the same route.

#58 mustang__1

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Posted 05 March 2013 - 01:17 PM

alright, having to only replace the rig and main at the time of the swap makes it a bit more palatable - for some reason i always envisioned having to do everything at once. its still a lot of money, but, i dunno...

#59 Reht

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Posted 05 March 2013 - 02:25 PM

alright, having to only replace the rig and main at the time of the swap makes it a bit more palatable - for some reason i always envisioned having to do everything at once. its still a lot of money, but, i dunno...


If money is a serious concern, you can always hold out for a season or two, and especially in a fleet like the 29ers, there will be plenty of boats that stick with the old rig for a while. Once used new rigs on come the market it can be quite inexpensive to make the upgrade. And if the mast is anything like the 49er mast, it'll be absolutely bullet proof.

#60 Speng

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Posted 05 March 2013 - 08:52 PM

The mast was the one thing on my 29er that I didn't like. My understand is that the lower 2 sections are the same extrusion as the original 49er mast so perhaps not optimized to the boat. That and the required stiffness to get the automatic rig made it a bit telephone pole-ish. Compared to the taller rig on a Melges 17 scow it is way heavier and reckon antipodean mast builders would do a better job than that so a composite rig for the 29er should be a huge improvement. My understanding too is that the carbon rig makes the 49er more accessible than the old rig so more and more pluses if a carbon rig on a 29er had the same improvements. Do the carbon rigged 49ers use more or less rig tension than the old mast?

I reckon compared to the toilet paper rags on your typically youth dinghy that a 29ers sails might seem a bit expensive but being so heavily battened they should hold their shape longer. Probably a good idea to keep them in a cool place so the Mylar doesn't go off but I loved the sails. I like zip luffed jibs on boats I've sailed with them but I also liked the hanks on the 29er so no real preference there.

In any case kudos to JB for making sure that 20 years from now his boats aren't antiquated shitters like the 470 is.

#61 mustang__1

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Posted 05 March 2013 - 09:28 PM

the mains are pretty easy to keep going. The leeches can see a fair bit of load, but they certainly dont flog themselves to death. I would still be happy to race with my 2008 main, which has seen a fair bit of race and practice time, at most regattas. Thats irrelevant if they're changing the rig, though. The jibs flog themselves to death as fast as anything else and they still develop a nasty hollow in the leech (just because i raced and practiced with mine for years doesnt mean i was fast doing it!...). kites dont get kind treatment with the launcher. Do they last longer than 420 sails? yes - especially mains. the cost of sails is systematically high for everyone, though. I mean, $560for a laser main? $585 for an opti sail? yeesh.

#62 BalticBandit

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Posted 05 March 2013 - 10:02 PM

The 29er/49er hanks just sucked... going to a zip luff for the 49er is a HUGE improvement.

#63 mustang__1

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Posted 06 March 2013 - 08:24 PM

i dont have strong feelings one way or the other with hanks or zip. If you're gentle with them they dont break - i only broke one on my 2008 jib and its been through hell. I've used zipper luffs on other boats, they're nice, but, i dont hate the hanks.

Ok, im honestly starting to come over to wanting a carbon mast. It took me a while to realize that you dont need the whole set of sails to make the conversion (and i think that if the cloth for the jib and kite were to be changed that it should be phased in after the rig/main). Id be lying if i havent said i wish the boat came with one from the start - its changing midlife that bothers me.. In any case, if we're going to a new stick, what is the chance that it can be a bit more tuny? im thinking adjustable butt (either XX style - although i realize that was just supposed to be an equalizer - or something a bit more complex) and/or spreader rake? Yes, its a bit more cost, but not astronomical - the spreaders arent free anyway. What about an OTW adjustable forstay via purchase system? Clearly if we're talking about a very expensive upgrade then we are starting to shift from the super simple, relatively easy to sail, youth boat into something a bit different, IMHO. Yes it will still be easy to sail - but a multithousand dollar upgrade puts the class into a more elevated level of racing than just getting out on the water.

#64 JulianB

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Posted 06 March 2013 - 10:46 PM

This started off about foils, and now we are onto Rigs.

This is 99% of the problem, people see the bit in the air, they forget about the bit in the water!

Some of this conversation is priceless, the 4% area of foils compared to Sails. Plus the graph, my favourite!

And even though water is 812 times more dense than air, the foil is moving at BS where as the rig, up wind, where it seems to matter is going at a combination of BS and WS.

Plus again, you need area coming out of a tack, once your going, you need about 1/2 that area.

So the 4% is arguably correct.

Guys time to go, need to do some other stuff, Enjoy.

JB

#65 Reht

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Posted 06 March 2013 - 11:26 PM

This started off about foils, and now we are onto Rigs.

This is 99% of the problem, people see the bit in the air, they forget about the bit in the water!

Some of this conversation is priceless, the 4% area of foils compared to Sails. Plus the graph, my favourite!

And even though water is 812 times more dense than air, the foil is moving at BS where as the rig, up wind, where it seems to matter is going at a combination of BS and WS.

Plus again, you need area coming out of a tack, once your going, you need about 1/2 that area.

So the 4% is arguably correct.

Guys time to go, need to do some other stuff, Enjoy.

JB


I think everyone is excited to see what is coming up. The 29er with a face(rig)lift? Cheap and durable foils? Change up the 49er spin? And all the bits of information. I think next time I go out on a 29er I'll just shimmy that board up a few inches and see what difference it makes.

You do know that any time you want to put up information or show off a recent development there will be plenty of us here who would be happy to read (and probably share our thoughts)...

(Man, winter is long...)

#66 facthunt

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Posted 06 March 2013 - 11:34 PM

im not excited, thought its more interesting than another laser thread.

#67 Rohanoz

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Posted 07 March 2013 - 01:09 AM


This started off about foils, and now we are onto Rigs.

This is 99% of the problem, people see the bit in the air, they forget about the bit in the water!

Some of this conversation is priceless, the 4% area of foils compared to Sails. Plus the graph, my favourite!

And even though water is 812 times more dense than air, the foil is moving at BS where as the rig, up wind, where it seems to matter is going at a combination of BS and WS.

Plus again, you need area coming out of a tack, once your going, you need about 1/2 that area.

So the 4% is arguably correct.

Guys time to go, need to do some other stuff, Enjoy.

JB


I think everyone is excited to see what is coming up. The 29er with a face(rig)lift? Cheap and durable foils? Change up the 49er spin? And all the bits of information. I think next time I go out on a 29er I'll just shimmy that board up a few inches and see what difference it makes.

You do know that any time you want to put up information or show off a recent development there will be plenty of us here who would be happy to read (and probably share our thoughts)...

(Man, winter is long...)


JB - your input and information here is invaluable. (You can only read books so many times!!!)

Just a Q on the rig ratios you mentioned earlier - jib too big on the 29er? or main too small?

#68 cantp1

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Posted 07 March 2013 - 01:49 AM

i dont have strong feelings one way or the other with hanks or zip. If you're gentle with them they dont break - i only broke one on my 2008 jib and its been through hell. I've used zipper luffs on other boats, they're nice, but, i dont hate the hanks.

Ok, im honestly starting to come over to wanting a carbon mast. It took me a while to realize that you dont need the whole set of sails to make the conversion (and i think that if the cloth for the jib and kite were to be changed that it should be phased in after the rig/main). Id be lying if i havent said i wish the boat came with one from the start - its changing midlife that bothers me.. In any case, if we're going to a new stick, what is the chance that it can be a bit more tuny? im thinking adjustable butt (either XX style - although i realize that was just supposed to be an equalizer - or something a bit more complex) and/or spreader rake? Yes, its a bit more cost, but not astronomical - the spreaders arent free anyway. What about an OTW adjustable forstay via purchase system? Clearly if we're talking about a very expensive upgrade then we are starting to shift from the super simple, relatively easy to sail, youth boat into something a bit different, IMHO. Yes it will still be easy to sail - but a multithousand dollar upgrade puts the class into a more elevated level of racing than just getting out on the water.


You REALLY need to sail a 470 man. Really. Or an i420 maybe... Please stop complaining about the 9er class evolving.

And yeah, major thanks to JB for enlightening us mere mortals!

#69 mustang__1

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Posted 07 March 2013 - 01:51 AM

i do sail 470's on occasion. And yes, i will be shutting up.

#70 Ben G

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Posted 07 March 2013 - 02:44 AM

Well, many things were talked about but nowhere is there any mention of the profile shape of the boards, the first part of question #1.
ie rectangular foil compared to triangular foil, with an elliptical foil somewhere in between., and foil rake.

Here are some hypotheses, which you may be able to shed more light on:

1/ An elliptical foil is supposed to be the most efficient shape due to minimising induced drag, but it is not optimised for overturning moment.

2/ Some kind of tapered ellipse may be better, as you can achieve a higher aspect ratio without increasing the overturning moment. Maybe the effect on overturning moment (ie due to increased length of the moment arm) isn't that significant?
http://www.tspeer.co...orms/Planar.htm

3/ raked foils may be more efficient when boats are heeled

After reading your discussion about accelerating out of tacks I'd consider adding:

4/ Assuming it takes two chord lengths to re-establish most of the lift (due to the starting vortex), it follows that a narrower chord foil reaches full lift sooner. This seems somewhat counter to my experience

5/ A rectangular foil will create a large tip vortex with correspondingly more energy in it, does this make a rectangular foil better or worse out of tacks? I've heard a rumour that semi-triangular foils are a bit slippy at first.

Cheers

#71 couchsurfer

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Posted 07 March 2013 - 03:07 AM

Well, many things were talked about but nowhere is there any mention of the profile shape of the boards, the first part of question #1.
ie rectangular foil compared to triangular foil, with an elliptical foil somewhere in between., and foil rake.

Here are some hypotheses, which you may be able to shed more light on:

1/ An elliptical foil is supposed to be the most efficient shape due to minimising induced drag, but it is not optimised for overturning moment.

2/ Some kind of tapered ellipse may be better, as you can achieve a higher aspect ratio without increasing the overturning moment. Maybe the effect on overturning moment (ie due to increased length of the moment arm) isn't that significant?
http://www.tspeer.co...orms/Planar.htm

3/ raked foils may be more efficient when boats are heeled

After reading your discussion about accelerating out of tacks I'd consider adding:

4/ Assuming it takes two chord lengths to re-establish most of the lift (due to the starting vortex), it follows that a narrower chord foil reaches full lift sooner. This seems somewhat counter to my experience

5/ A rectangular foil will create a large tip vortex with correspondingly more energy in it, does this make a rectangular foil better or worse out of tacks? I've heard a rumour that semi-triangular foils are a bit slippy at first.

Cheers


.........a good set of questions!......................

................definetely worth comment by someone -much- more qualified than myself!!! ;)

#72 duncan (the other one)

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Posted 07 March 2013 - 05:12 AM

Well, many things were talked about but nowhere is there any mention of the profile shape of the boards, the first part of question #1.
ie rectangular foil compared to triangular foil, with an elliptical foil somewhere in between., and foil rake.

Here are some hypotheses, which you may be able to shed more light on:

1/ An elliptical foil is supposed to be the most efficient shape due to minimising induced drag, but it is not optimised for overturning moment.


careful here. Elliptical shape is not the most efficient. Elliptical loading is theoretically the most efficient.

#73 JulianB

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Posted 07 March 2013 - 01:16 PM

A truncated Ellipse.

How truncated depends on the difference between expected lowest speed (tacking) and expect cruse speed up wind.
It will also dictate AR and cord.

So a light boat like a skiff will have heavily truncated foils, quite short, and longish cords, and low AR, because they slow down a lot, but are easy to accelerate and therefore the gain by reducing frontal area grossly out weighs the in-efficiency of acceleration out of a tack, because that acceleration will be short and you are happy to wear extra short term drag for long term gain. Low AR because there is not much opportunity for tip loss once up to speed. Carrying twice the area needed anyway.

Heavier boats like Yachts, the drag from the hull so massively out-weighs the foils that you tend to go for long thin foils that stick, you don't really care if they generate more drag, your just worried about climbing as high as you can, because you just cant push it any faster than .95 of HS.

More Corinthian type boats, and here I'm talking 470, Laser, up wind, your still bound most of the time by HS, so you want to point, so more area to minimise yawl.

Most interesting boat is 5o5. At low speed, its gybes it foil, because yawl is important, as soon as it starts planning to windward, it racks the foil aft and lock it in the middle because its up on-top of the water, so yawl drag become irrelevant.

(we measure yawl drag in one series of test, its quite significant in a 49er, at slow speeds so a more displacement/Corinthian type boat, it will be even more extenuated.)

Cats, a lot of the side force is carried by the leeward hull/ahma so whole new ball park, but asymmetrical foils or symmetrical foils toed in 1-2degrees, but the cats tend to carry foils which are far closer to there operating area than there "tacking" area, again a compromise, as cruise speed is so much greater than tacking speed.

Re Rack, in practice, other to to postpone ventilation (Moths) rack within +/- 5-10 degrees is not that important, balance far outweighs any gain.

JB

#74 Speng

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Posted 09 March 2013 - 06:06 AM

JB, if you could ( I think it got lost in my earlier post) but what's the rig tension on the carbon rig 49er vs the tin rig? Higher or lower? Thanks.

#75 JulianB

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Posted 09 March 2013 - 09:22 AM

Completely off the subject, but F/Stay tension is a function of F/Stay length. New F/Stay is about 120mm longer than the old, so you would expect to the new tension to be a little higher, not a lot, but a tad higher than than the old.

#76 aus_stevo

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Posted 09 March 2013 - 09:19 PM

yaw
http://1.bp.blogspot...awPitchRoll.jpg
yawl
http://static.flickr..._caf83a8074.jpg
sorry for being petty. its been annoying me

#77 Reht

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Posted 10 March 2013 - 04:52 PM

JB, if you could ( I think it got lost in my earlier post) but what's the rig tension on the carbon rig 49er vs the tin rig? Higher or lower? Thanks.


The shrouds run very close to the same numbers on the two rigs (within a number or two on a LOOS gauge).

#78 JulianB

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Posted 11 March 2013 - 10:21 PM

Reht, don't know because I dont look.

I get fore-stay tension first
Then I look at lower mast bend
Then dial in the uppers

Go around that cycle 1-2 times

And what is left is shroud tension.

Im in NZ right now, but I can ask Harry for you when i get back home, he would have a target Shroud/Primary tension.

The issue is this varies a lot depending on how you chose to sail the boat, a lot of nuances in there, and its a fine line. 1 turn on lowers is all it takes from bound up to free for one person, but may be totally ok for another, depending on every other variable.

That's the beauty of this sport, the nuances.

JB

#79 Reht

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Posted 12 March 2013 - 01:22 AM

Reht, don't know because I dont look.

I get fore-stay tension first
Then I look at lower mast bend
Then dial in the uppers

Go around that cycle 1-2 times

And what is left is shroud tension.

Im in NZ right now, but I can ask Harry for you when i get back home, he would have a target Shroud/Primary tension.

The issue is this varies a lot depending on how you chose to sail the boat, a lot of nuances in there, and its a fine line. 1 turn on lowers is all it takes from bound up to free for one person, but may be totally ok for another, depending on every other variable.

That's the beauty of this sport, the nuances.

JB


I have difficulty just looking at something and saying it's the same as last time I was in similar conditions, are you aiming just to have everything look "close enough" or do you go and tweak it so it looks perfect? So you set the forestay to whatever you feel the appropriate number is, fix the bend with the lowers, then adjust the primaries? Or the caps (or both)?

I guess I just need numbers that I know I can reliably recreate (it's how I can convince myself it's my sailing ability that's causing me to be useless and not that I set up the boat totally wrong), that means I have my chart of basic numbers given the conditions (which took a while to figure out what felt just right). Of course then there's always a few little adjustments, too many variables to count, but I normally leave that last turn or two until we're on the water and can have a better idea of what needs to change in the feel.

#80 JulianB

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Posted 12 March 2013 - 01:47 AM

Yeh, let me go hunt a set of numbers down for you.
Also make sure you can change rig tension on the water in a controlled manner
Take a chinagraph pencil with you.

But I will try and get you a set of numbers.

JB

#81 Kelm872

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Posted 12 March 2013 - 01:52 AM

Kinda off topic but I have a old 49er that doesn't have the isaf number is there a way I can get one of my boat?

#82 Reht

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Posted 12 March 2013 - 01:58 AM

Yeh, let me go hunt a set of numbers down for you.
Also make sure you can change rig tension on the water in a controlled manner
Take a chinagraph pencil with you.

But I will try and get you a set of numbers.

JB


I have a set of numbers that I've been using, but I'm always open to a different perspective to try, especially at the start of the season in a month or two.

Kinda off topic but I have a old 49er that doesn't have the isaf number is there a way I can get one of my boat?


If the serial number is on it, the hull number should be part of the serial number (along with a year of production). Probably the easiest way would be to call up the manufacturer and they could tell you which part of the serial number to look at. Then talk to ISAF about getting a replacement sticker for it.

#83 Kelm872

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Posted 12 March 2013 - 02:12 AM

Ya it says AUS109 9029 but it's kinda hard to call Australia from Boston but ill shoot them an email in the morning to see what I have to do. Thanks very much

#84 JulianB

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Posted 12 March 2013 - 09:06 AM

That is not a std AUS serial number, we use the US CG system.
Its a alpha numeric system, yes its most likely a AUS boat but the number dose not make sense.
At a guess its out of the #1 mould, which is the original master mould.
It was built in the 2nd month of 1999
But the hull number is throwing me.
We where building number 400-500 then.
Got to remember there where 156 boat build before we went to Garda for the selection trials in 96.

Yah got me. Is it a interesting colour, any other marks????

No point in ringing AUS, im in NZL at the moment.

JB

#85 Kelm872

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Posted 12 March 2013 - 11:14 AM

There is a silver starboard production sticker but it seem to only have the fax number and it's a normal white hull but it has two massive Mclube on each side so I'm guessing they did something with the boat

#86 BalticBandit

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Posted 12 March 2013 - 01:20 PM

Sounds like one of Charlie and Jonathan's original hulls

#87 Reht

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Posted 12 March 2013 - 03:28 PM

Sounds like one of Charlie and Jonathan's original hulls


Maybe they have a recollection. Another interesting case of identifying an old 9er...

#88 BalticBandit

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Posted 12 March 2013 - 05:05 PM


Sounds like one of Charlie and Jonathan's original hulls


Maybe they have a recollection. Another interesting case of identifying an old 9er...

And I have a vague (remember I'm blonde....) recollection of one of their boats being a 109 series.... that would be from the first containerload Julian that you sent to seattle. I think my sail number was like 149....

#89 JulianB

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Posted 13 March 2013 - 02:13 AM

Very possibly.

First container load went to Florida, (Punta Gorda ????) BTW, when you had that icelandic storm that froze everything.

JB

#90 BalticBandit

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Posted 13 March 2013 - 02:28 AM

oops correction. Mine was Hull 172.... just looked it up. like I said... I'm blonde. But if mine was 172, then the rest of the Seattle hulls were similarly in that range. The orgininal hull for the McKees was 77, and 33 for Rehnehan/Lanzinger. but I know they got a second "travelling" hull that went in the USA team container. I wouldn't be surprised if that was 109

#91 Kelm872

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Posted 13 March 2013 - 11:16 AM

could this possibly be the boat http://www.powellwri...ig_McLube_1.jpg I was looking up team mclube 49er and this one seems to match what you guys where talking about?

#92 BalticBandit

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Posted 13 March 2013 - 02:27 PM

It sure could be. that would make the number 139 instead of 109 though... but that's right in the range of the numbers that arrived in Seatttle in March/April of 1997. (or was it 1996? damn I'm being blonde again)

Good Old Meadow Point Hurricane!!!

#93 Kelm872

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Posted 13 March 2013 - 03:43 PM

So i should email ISAF about a replacement plaque with the hull number?

#94 cantp1

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Posted 13 March 2013 - 03:53 PM

There is a silver starboard production sticker but it seem to only have the fax number and it's a normal white hull but it has two massive Mclube on each side so I'm guessing they did something with the boat


Andrew, for some reason, I have you in on the 49erNA contact list as hull # 023. Not sure where that came from though...

#95 Kelm872

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Posted 13 March 2013 - 04:08 PM

Ya when I first got the boat the guy told me that it was 23 but I meant to send you a msg about the miss communication and that's it's 109

#96 Ben G

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Posted 15 March 2013 - 01:51 AM


Well, many things were talked about but nowhere is there any mention of the profile shape of the boards, the first part of question #1.
ie rectangular foil compared to triangular foil, with an elliptical foil somewhere in between., and foil rake.

Here are some hypotheses, which you may be able to shed more light on:

1/ An elliptical foil is supposed to be the most efficient shape due to minimising induced drag, but it is not optimised for overturning moment.


careful here. Elliptical shape is not the most efficient. Elliptical loading is theoretically the most efficient.


- An elliptical shape will have an elliptical loading if the twist and section are the same top-bottom, fair assumptions I think.
- Also Rectangular or triangular profiles will tend towards elliptical loading, ie the tip of a rectangular foil is 'lazy' wheras the tip of a triangular foil will do more than its share.
- Elliptical loading is not necessarily the most efficient, depending on its effect on overturning moment.

#97 duncan (the other one)

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Posted 15 March 2013 - 04:41 AM



Well, many things were talked about but nowhere is there any mention of the profile shape of the boards, the first part of question #1.
ie rectangular foil compared to triangular foil, with an elliptical foil somewhere in between., and foil rake.

Here are some hypotheses, which you may be able to shed more light on:

1/ An elliptical foil is supposed to be the most efficient shape due to minimising induced drag, but it is not optimised for overturning moment.


careful here. Elliptical shape is not the most efficient. Elliptical loading is theoretically the most efficient.


- An elliptical shape will have an elliptical loading if the twist and section are the same top-bottom, fair assumptions I think.
- Also Rectangular or triangular profiles will tend towards elliptical loading, ie the tip of a rectangular foil is 'lazy' wheras the tip of a triangular foil will do more than its share.
- Elliptical loading is not necessarily the most efficient, depending on its effect on overturning moment.


is 1. a fair assumption? Tapering to any great degree means a thicker (% of chord) section is needed at the tip to avoid going too slim.

#98 JulianB

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Posted 15 March 2013 - 06:39 AM

And what's the problem with going to slim! I assume you mean % camber, anything down to 6 % is acceptable.

If the top is say 10% and the tip is 6% thats fine, your not going to slim.

#99 Presuming Ed

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Posted 15 March 2013 - 07:31 AM

The aim of this programme is to lower the drag coefficent but maintain the width of the bucket on alternate tacks without requiring the yaw slip to generate the lift. Achievable with the flapped board in theory.


Late and a bit OT, but there we go. Only photos I took at the dinghy show. National 12 flapped board.

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#100 duncan (the other one)

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Posted 15 March 2013 - 08:52 AM

And what's the problem with going to slim! I assume you mean % camber, anything down to 6 % is acceptable.

If the top is say 10% and the tip is 6% thats fine, your not going to slim.


What, 6% of something like 100mm or less? That's mighty thin and crunchable.

I thought the better bet was to thicken the % section near the tip to keep the thickness relatively constant as the board is tapered?




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