Bill E Goat
Super Anarchist
Is that yellow hatted DEVO saiiling the boat, were the speeds spikes or over 5 or 10 second periods, Nic Press managed 26 knots in his 12 over a 10 second period the other week
89er
- Thread starter JulianB
- Start date
allweather
Member
So, the formula approach to build as light as possible and reinforce the areas you break testing? Sure sounds like you had fun with the boat regardless and those pictures going upwind! The boat even looks fast and light on it's feet.
Steam Flyer
Sophisticated Yet Humble
In the photos above, she doesn't look really cranked-in close hauled, footing off a bit, but there's a noticeable stern wave. In the one from high up & astern, it's hiding most of the transom... thus showing the crest of the stern wave is well aft of the transom. I always take that as a good sign for hull form, that the water isn't clutching the hull with a strong grip and holding it back.
JulianB
Super Anarchist
- Thread starter
- #864
I think 12 months ago took a shot with 2 champagne glasses from the same spot.
This year it's Gin & Tonics, got to keep up the traditions!
Alex and I went to some effort to bolt that block in because it's so inaccessible, not sure why it came out, could be the far finer threads on the Metric system, where as the BSW thread is coarser and possibly better suited to Brass, don't know but 2 x M5 MT should be close to 1.5 tonne especially in sheer and the brass is still there, happy as Larry, anyway, we did design the turning block to be capable of carrying 1 + tones, that should have been maybe a 3 times safety margin, we thought, shite happens, it won't happen again.
The issue with the jib was that the sheeting attitude was to vertical, so we cracked it. I was very happy with BS, and TWA, we were sailing through those boats that were around us easily and you can't do that going slow or going low, but the instrumentation we had, was tracking rather than live. The Veliciteck comes today I think, hard to find one in Australia at present, and it's GT's side of the arrangement, so next weekend, should be far more enlightened WRT BS and Tacking Angles.
Probably sailing Saturday, maybe Sunday.
jB
This year it's Gin & Tonics, got to keep up the traditions!
Alex and I went to some effort to bolt that block in because it's so inaccessible, not sure why it came out, could be the far finer threads on the Metric system, where as the BSW thread is coarser and possibly better suited to Brass, don't know but 2 x M5 MT should be close to 1.5 tonne especially in sheer and the brass is still there, happy as Larry, anyway, we did design the turning block to be capable of carrying 1 + tones, that should have been maybe a 3 times safety margin, we thought, shite happens, it won't happen again.
The issue with the jib was that the sheeting attitude was to vertical, so we cracked it. I was very happy with BS, and TWA, we were sailing through those boats that were around us easily and you can't do that going slow or going low, but the instrumentation we had, was tracking rather than live. The Veliciteck comes today I think, hard to find one in Australia at present, and it's GT's side of the arrangement, so next weekend, should be far more enlightened WRT BS and Tacking Angles.
Probably sailing Saturday, maybe Sunday.
jB
peterivanac
Member
- 321
- 19
Wow only 147kg in the bulb. The 79er we sailed on the weekend apparently had 240kg? Boat did seem very "stable"
JulianB
Super Anarchist
- Thread starter
- #866
DP's bulb is 136kgs, the fin is 11kgs making 147kgs.
Vivace's bulb was design from memory at 186kgs with about 15kg fin, so the design fin would/should have been ~ 200kgs.
I do know it has carried upwards of 350kgs bulb, no idea of the weight of the fin.
DP is amazingly stable, GT did the cockroach a few times on Saturday and those of us in the engine room (up fwd) did not even notice. Just had David (Lambourne) on the phone and we where commenting on form stability, may have got that right!
Both David and I have ordered a 70kg bulb (each) of Brain Partridge in SA, maybe I can pick them up when I'm in Port Lincoln. That will make it a tad more lively.
Vivace's bulb was design from memory at 186kgs with about 15kg fin, so the design fin would/should have been ~ 200kgs.
I do know it has carried upwards of 350kgs bulb, no idea of the weight of the fin.
DP is amazingly stable, GT did the cockroach a few times on Saturday and those of us in the engine room (up fwd) did not even notice. Just had David (Lambourne) on the phone and we where commenting on form stability, may have got that right!
Both David and I have ordered a 70kg bulb (each) of Brain Partridge in SA, maybe I can pick them up when I'm in Port Lincoln. That will make it a tad more lively.
DickDastardly
Super Anarchist
Will it still self-right at 70kg? I'm assuming you've done the numbers on that!
JulianB
Super Anarchist
- Thread starter
- #868
We will pass ISO 3 which is the self righting rule, highly probably.
With 70kgs, I doubt you would self right, but even Vivace when I sailed her in 2004, with 186kgs at Belmont, we would have easily passed ISO 3, but 2 of us had to get on the level, when we capsized, to get it back up.
The plan is to do the self-righting test next week (with 136kgs), if when doing that you get the load at the tip, (you need to hold it down) then it becomes a simple sum as to how much lighter the bulb can be.
JulianB
Super Anarchist
- Thread starter
- #870
Barney, 3 completely differing things at play here.
#1 Sails up or sails down, if your capsized, it's likely the sails are up, where as the ISO 3 is main on the boom and jib somewhere.
#2 How quickly is "it coming back up, self righting" & the 3rd
#3 did you capsize to windward or to leeward, so worst case or best case.
In Super30, my understanding is it's Cat 7, so if a Opie can sail, you can sail! No bulb required, don't even need a motor.
Port Lincoln, Cat 6???, Bay to Bay is Cat 5m, Airlie & Magie, Cat 5.
But regardless, and I am very sure that 136kgs of lead will satisfy ISO3/Cat 5 in-terms of "self-right", we have tested the "fin" to 250% which is above ISO because I am very sure, if we happen to capsize, some of the crew will be on it very fast, and we may also find one of the crew 1/2 way up the mast holding it down while we pack a spinnaker or what ever.
But I am sure a NA in our midst, will pontificate what he thinks is enough.
#1 Sails up or sails down, if your capsized, it's likely the sails are up, where as the ISO 3 is main on the boom and jib somewhere.
#2 How quickly is "it coming back up, self righting" & the 3rd
#3 did you capsize to windward or to leeward, so worst case or best case.
In Super30, my understanding is it's Cat 7, so if a Opie can sail, you can sail! No bulb required, don't even need a motor.
Port Lincoln, Cat 6???, Bay to Bay is Cat 5m, Airlie & Magie, Cat 5.
But regardless, and I am very sure that 136kgs of lead will satisfy ISO3/Cat 5 in-terms of "self-right", we have tested the "fin" to 250% which is above ISO because I am very sure, if we happen to capsize, some of the crew will be on it very fast, and we may also find one of the crew 1/2 way up the mast holding it down while we pack a spinnaker or what ever.
But I am sure a NA in our midst, will pontificate what he thinks is enough.
DavidYacht
Member
Are you referring to ISO 12217-3? If so why bother, it’s a racing boat … the ISO considers complete ignorance on the part of the operator.
DavidYacht
Member
Ah. Trouble the ISO assumes that the boat is being sailed by numptys, which you are not
Sorry for digging up this old post but it's giving me a sleepless night. I tried to do the same calculations for my I14 daggerboard but couldn't get near your 1° AoA even though the boats are somewhat similar.
So, I tried to double check your numbers:
If i put 7kts, ~90kg and 0,3m² into the lift equation, the resulting CoL is far from 0.2 (more like 0.45-0.5).
This would give an AoA of ~6° and the foil would operate outside the laminar bucket. Obviously the 49er doesn't operate at 6°. Is there an error in my equation?
JulianB
Super Anarchist
- Thread starter
- #876
I14 Berlin, great town, we did NYE there 2019-20, Alexander Plaza, what a an extraordinary experience. You guys and fireworks are made, one flat caught on fire from memory!
And always have to respect someone (as you (& I) are) that has a greater number of + reactions than posts.
The short answer is, doing theoretical maths as you have done above, is definitely NOT my strong suite. Probably why my father said, best thing I didn't do, was finish NA.
What I am good at, and what I have sort of made my thing, is going looking for empirical evidence and then using that to make a judgment about a similar project, but while doing that, use checks and balances to make sure I don't go off the rails. So the maths of comparison and estimation I am good at. With that training/familiarisation I have made decisions and very few have been wrong.
What I can do is get a NA to do the maths, I have 3 I can ask, and they also all know that a 49er dose not have a yaw of 6° - but in the interum I can make the following comments.
A I14 is 14ft, really great boat, really only sailed one seriously maybe 3 times, and, BTW, there are lots of great boats at 14ft, NS14, Tasars, GP14, etc etc. and one of my lofty ambitions was to win a POW (that aint going to happen now). But a 29er is longer than 14ft, and a 49er is almost 2.5ft longer. They are 70kgs, so 20kgs less than a 49er (similar to a 29er).
Main and jib similar! Spinnaker, I14 is bigger (but 49er has reduced spin area and gone faster)
But WRT RM, your about 1/2 the grunt, because you don't have wings.
Hull shape is dramatically different, 49er (& 29er & 89er) have long fine Freud angles, where as a I14 is has a fullish bow, which it has to to stop plunging with all that sail area, and narrow width.
You have almost an exact sequel (you can make up your mind which came first), the GP 18teen had long fine Freud angles, the current 18teens, much fuller bows. No argument as to which did the course fastest, and yes one had 17ft wings, (as opposed to 14ft) but the fastest 18teen ever where the 17ft winged boast, not the 34ft, or the 21ft or the 18ft, so that corollary dose not hold much water.
Current 18teen far easier to sail. GP 18teen where beasts! F--ky scary!!!!!!!!
Can't say that a I14 is easy to sail because I have not sailed one and I doubt it, but a 49er can be a beast, especially if you have not come from a class like a I14, 29er, 16teen, F11 etc etc.
So, my expectation is that you have not taken into account 3 things.
#1 is the end plate effect. 49er effectively seal their Fin/Hull interface, probably less than 0.2mm gap, which a I14 with a tacking foil can't do. More to the point, every 49er foil is within +/-0.25mm of another one, so you can invest a lot of time getting that joint (bottom of the center-case) right. Add to that we have had the opportunity to experiment over 10-15 years and get the feathering of the tip right. It will never be perfect, but the 49er ratio of % camber reduction and tip flex plus probably some natural washout (feathering) is pretty damm good, and that should lead to a 2nd increase in AR
#2, is that with approx double RM, an extra 2+ft of WL and very fine Freud angles, a 49er is likely to accelerate straight past 7knts effortlessly. So the reality is that 7knts is a minimum operating speed, Cruise speed is likely to be low to mid 8's and I know (because I used to personally do it, and they are so much better than me now) that peak up-hill speeds where just shy of 12. An I14, because people still opt of a tacking board, that by definition means it spends a lot of it's time at/below HS, and that aint a lot. Finally
#3 Big believe in this, thin low drag foils/hull work best with thin low drag rigs. The corollary to that is fuller foils/hulls work best with fuller rigs. On DP (and this is a SB page afterall) we are all about drag reduction, so letting the D2's go (ease) so as to flatten the lower main so as to reduce the drag where as on the FE28r or the 6Pac or the Farr30 it was all about grunt to "smash" through . If I could have last weekend, and what I will do next weekend is ensure that I can sheet the jib right, again so I can blade it off to reduce drag, rather than up the grunt. My point being in all of this is that the 49er is now so refined that they simply blow past 7 knt's without even noticing it.
~~~~~~~~~~~~~~~~~~~~~~
But, very interesting point of yours!!! Sorry to everyone for going of topic, but my guess is that a 49er enjoys a significant increase in AR by very effective sealing of the hull/fin interface, plus the tip dose a 2ndry seal and that it blows straight past 7knts because of its fine Freud WL's and low drag rig.
And that in turn allows it to operate with a Fin that is far smaller than basic theory would suggest. And the proof of that is the fine yaw°.
What will be interesting is to ask these NA's to factor in increase AR (due to effective end-plating, at the keel that could be 180-200%, at the tip, maybe another 125-140%) and then work out what speed the boat has to go to hit the yaw angle that we empirically observe!
Very interesting bit of maths. Maybe I will reach out to Simon (FRA), he did it before with Dad, or Joaquin (ARG). Then again I have Martin here, and he sailed DP with me last WE.
Give me a week or so, I will have to convince someone to put their name to some maths, and that could well be controversial, but I believe the answer lies there.
Plus there are some really smart people reading this, who can do this stuff while they have breakfast, just for fun, so I throw it out there for anyone to have a go.
Really, thanks for the question, makes the grey matter move.
jB
And always have to respect someone (as you (& I) are) that has a greater number of + reactions than posts.
The short answer is, doing theoretical maths as you have done above, is definitely NOT my strong suite. Probably why my father said, best thing I didn't do, was finish NA.
What I am good at, and what I have sort of made my thing, is going looking for empirical evidence and then using that to make a judgment about a similar project, but while doing that, use checks and balances to make sure I don't go off the rails. So the maths of comparison and estimation I am good at. With that training/familiarisation I have made decisions and very few have been wrong.
What I can do is get a NA to do the maths, I have 3 I can ask, and they also all know that a 49er dose not have a yaw of 6° - but in the interum I can make the following comments.
A I14 is 14ft, really great boat, really only sailed one seriously maybe 3 times, and, BTW, there are lots of great boats at 14ft, NS14, Tasars, GP14, etc etc. and one of my lofty ambitions was to win a POW (that aint going to happen now). But a 29er is longer than 14ft, and a 49er is almost 2.5ft longer. They are 70kgs, so 20kgs less than a 49er (similar to a 29er).
Main and jib similar! Spinnaker, I14 is bigger (but 49er has reduced spin area and gone faster)
But WRT RM, your about 1/2 the grunt, because you don't have wings.
Hull shape is dramatically different, 49er (& 29er & 89er) have long fine Freud angles, where as a I14 is has a fullish bow, which it has to to stop plunging with all that sail area, and narrow width.
You have almost an exact sequel (you can make up your mind which came first), the GP 18teen had long fine Freud angles, the current 18teens, much fuller bows. No argument as to which did the course fastest, and yes one had 17ft wings, (as opposed to 14ft) but the fastest 18teen ever where the 17ft winged boast, not the 34ft, or the 21ft or the 18ft, so that corollary dose not hold much water.
Current 18teen far easier to sail. GP 18teen where beasts! F--ky scary!!!!!!!!
Can't say that a I14 is easy to sail because I have not sailed one and I doubt it, but a 49er can be a beast, especially if you have not come from a class like a I14, 29er, 16teen, F11 etc etc.
So, my expectation is that you have not taken into account 3 things.
#1 is the end plate effect. 49er effectively seal their Fin/Hull interface, probably less than 0.2mm gap, which a I14 with a tacking foil can't do. More to the point, every 49er foil is within +/-0.25mm of another one, so you can invest a lot of time getting that joint (bottom of the center-case) right. Add to that we have had the opportunity to experiment over 10-15 years and get the feathering of the tip right. It will never be perfect, but the 49er ratio of % camber reduction and tip flex plus probably some natural washout (feathering) is pretty damm good, and that should lead to a 2nd increase in AR
#2, is that with approx double RM, an extra 2+ft of WL and very fine Freud angles, a 49er is likely to accelerate straight past 7knts effortlessly. So the reality is that 7knts is a minimum operating speed, Cruise speed is likely to be low to mid 8's and I know (because I used to personally do it, and they are so much better than me now) that peak up-hill speeds where just shy of 12. An I14, because people still opt of a tacking board, that by definition means it spends a lot of it's time at/below HS, and that aint a lot. Finally
#3 Big believe in this, thin low drag foils/hull work best with thin low drag rigs. The corollary to that is fuller foils/hulls work best with fuller rigs. On DP (and this is a SB page afterall) we are all about drag reduction, so letting the D2's go (ease) so as to flatten the lower main so as to reduce the drag where as on the FE28r or the 6Pac or the Farr30 it was all about grunt to "smash" through . If I could have last weekend, and what I will do next weekend is ensure that I can sheet the jib right, again so I can blade it off to reduce drag, rather than up the grunt. My point being in all of this is that the 49er is now so refined that they simply blow past 7 knt's without even noticing it.
~~~~~~~~~~~~~~~~~~~~~~
But, very interesting point of yours!!! Sorry to everyone for going of topic, but my guess is that a 49er enjoys a significant increase in AR by very effective sealing of the hull/fin interface, plus the tip dose a 2ndry seal and that it blows straight past 7knts because of its fine Freud WL's and low drag rig.
And that in turn allows it to operate with a Fin that is far smaller than basic theory would suggest. And the proof of that is the fine yaw°.
What will be interesting is to ask these NA's to factor in increase AR (due to effective end-plating, at the keel that could be 180-200%, at the tip, maybe another 125-140%) and then work out what speed the boat has to go to hit the yaw angle that we empirically observe!
Very interesting bit of maths. Maybe I will reach out to Simon (FRA), he did it before with Dad, or Joaquin (ARG). Then again I have Martin here, and he sailed DP with me last WE.
Give me a week or so, I will have to convince someone to put their name to some maths, and that could well be controversial, but I believe the answer lies there.
Plus there are some really smart people reading this, who can do this stuff while they have breakfast, just for fun, so I throw it out there for anyone to have a go.
Really, thanks for the question, makes the grey matter move.
jB
Bill E Goat
Super Anarchist
12 knots upwind !!!!
I think your boat is awesome but GPS spikes can give unrealistic top speeds, thats why I asked previously about the time period over which the speeds were recorded. Thats why Nick Presse's 26knots over a 10 second period would have to be one of the fastest 12's skiff speeds ever recorded, rather than a GPS spike speed
Last edited:
Bored Stiff
Member
Interesting stuff, thanks JB.
Berlin (reminds me of Money Heist, great Netflix series), your sums are right but… first of all you have ignored any lift contribution from the rudder (which is typically about 15-25% of the lift from the daggerboard) and:
secondly, I suspect JB’s numbers are slightly out. 49er polars by Simon Watin show that boat speed of a 49er is almost equal to wind speed, upwind in 8-12kt. So, 7kt boat speed is slow for a 49er and the leeway angle will be more than 1 degree. I would suggest 4 -4.5 degrees at 7kt (including rudder contribution) which would reduce to 2.5 deg at 9kt.
Berlin (reminds me of Money Heist, great Netflix series), your sums are right but… first of all you have ignored any lift contribution from the rudder (which is typically about 15-25% of the lift from the daggerboard) and:
secondly, I suspect JB’s numbers are slightly out. 49er polars by Simon Watin show that boat speed of a 49er is almost equal to wind speed, upwind in 8-12kt. So, 7kt boat speed is slow for a 49er and the leeway angle will be more than 1 degree. I would suggest 4 -4.5 degrees at 7kt (including rudder contribution) which would reduce to 2.5 deg at 9kt.
Thank you, JB! It's great how you share all your experience as it is hard to come by any real world scenarios.
This thread motivated me to start playing around with xflr5 to get a feeling on how my boat operates at different speeds. But I learned that being able to do the math is wort nothing if you don't have the empirical knowledge to estimate all the parameters.
Btw gybing centerboards in 14s are out of fashion, except for the (very successful) Holman design all top Brits went to fixed boards.
Thanks, you are correct. I didn't take the rudder into consideration and the hull probably carries a little bit of side force, too.
For me it's really fascinating how significantly crew weight, speed and board up/down change the AoA (at least theoretically). Add to that, that real foils all have a seam at the leading edge which might effect the nose radius and surface quality, I wonder if we really achieve laminar flow most of the time.
JulianB
Super Anarchist
- Thread starter
- #880
Hi guys, Berlin, Boredstiff, got to admit I was a bit hesitate writing this bog but certainly stirs the grey matter.
Yes, rudder should takes about 10-12% of the side load. WRT the 49er, the square head and the movement of the CoE back its probably up higher than that. I would not be surprised to learn its 20%. you need to factor that in.
The other factor that has not been taken into account is that just about every good 49er crew sails the boat heeled 4-5⁰ to windward so there will be some windward suck. I have never quantified that.
Plus the section we use is totally hydromanic, there is no aerodynamic data on it, and it has been refined and refined, especially the LE.
Just a couple of points.
The Simon Watin 49er work was 2008, pre the refinement of the Carbon rig, and pre the refinement of the new Alloy foil moulds so the boat speeds now being achieved higher.
We did (Dad & I) do a range of experiments to determine yaw. Yes you can compare SOG and Heading (compass) on both tacks and average that out. That instrumention was not good enough when we did it.
Far more fun was dye down the centercase and a camera (GoPro) mounted on the rudder frame. Also fishing line down the TE of the Centrecase with a small streamer at the transom, plus the same GoPro. I have done it so often now that I can pick the change in wake, especially on a heavier less refined boat. In the GP 18teens it was approx 4" (100mm) off CL and that would suggest sub 2⁰ yaw/AoA.
49er I have not done for a while so not going to venture there but we are well inside the bucket.
And you can feel the boat (49er) going turbulent (outside the bucket) and then clean up and accelerate as it comes back laminar/inside the bucket
But a fun project for DP on a Tuesday sail.
We did have a situation early in the GP 18teen days where we sailed in water only 1.1m deep (Perth] so our solution was to make a board that went in from the bottom and had a endplate (Goodman Feilder).
That board worked exceptionally well (& we won) other than being a real pain to get in and out, so I believe effective sealing the hull/fin joint plus careful dealtailing of the tip net significant AR benefits that you have not factored in, and I believe you should.
Final points, LE joints, paint/gelcoat is harder than epoxy, (& then you have kelp cutters) but a well detailed LE, as in 1200g you should not be able to determine the difference. Then again one of the things we did to de-whomp DP was refine the LE and that inclouded common material right around the LE.
And I14 going away from tacking foils makes total sense, as performance rises, the boat lifts and yaw drag drops.
jB
Yes, rudder should takes about 10-12% of the side load. WRT the 49er, the square head and the movement of the CoE back its probably up higher than that. I would not be surprised to learn its 20%. you need to factor that in.
The other factor that has not been taken into account is that just about every good 49er crew sails the boat heeled 4-5⁰ to windward so there will be some windward suck. I have never quantified that.
Plus the section we use is totally hydromanic, there is no aerodynamic data on it, and it has been refined and refined, especially the LE.
Just a couple of points.
The Simon Watin 49er work was 2008, pre the refinement of the Carbon rig, and pre the refinement of the new Alloy foil moulds so the boat speeds now being achieved higher.
We did (Dad & I) do a range of experiments to determine yaw. Yes you can compare SOG and Heading (compass) on both tacks and average that out. That instrumention was not good enough when we did it.
Far more fun was dye down the centercase and a camera (GoPro) mounted on the rudder frame. Also fishing line down the TE of the Centrecase with a small streamer at the transom, plus the same GoPro. I have done it so often now that I can pick the change in wake, especially on a heavier less refined boat. In the GP 18teens it was approx 4" (100mm) off CL and that would suggest sub 2⁰ yaw/AoA.
49er I have not done for a while so not going to venture there but we are well inside the bucket.
And you can feel the boat (49er) going turbulent (outside the bucket) and then clean up and accelerate as it comes back laminar/inside the bucket
But a fun project for DP on a Tuesday sail.
We did have a situation early in the GP 18teen days where we sailed in water only 1.1m deep (Perth] so our solution was to make a board that went in from the bottom and had a endplate (Goodman Feilder).
That board worked exceptionally well (& we won) other than being a real pain to get in and out, so I believe effective sealing the hull/fin joint plus careful dealtailing of the tip net significant AR benefits that you have not factored in, and I believe you should.
Final points, LE joints, paint/gelcoat is harder than epoxy, (& then you have kelp cutters) but a well detailed LE, as in 1200g you should not be able to determine the difference. Then again one of the things we did to de-whomp DP was refine the LE and that inclouded common material right around the LE.
And I14 going away from tacking foils makes total sense, as performance rises, the boat lifts and yaw drag drops.
jB
