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"Foiled" mini


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#101 Doug Lord

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Posted 23 May 2013 - 12:54 AM

Excellent slide show here from Christophe Breschi-shows the interior in detail including the method used to move the foil: http://breschi-photo...illage-mini-dss

Click on 091--(or try them all!)

#102 facthunt

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Posted 23 May 2013 - 04:32 AM

doug isn't there a width restriction in the mini rule, is a foil that extends outside the box ok?



#103 Doug Lord

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Posted 23 May 2013 - 12:55 PM

I can't answer your question except to say that the boat is a legal Proto. The foil is legal. Hugh may add to this if he gets a chance.

 

doug isn't there a width restriction in the mini rule, is a foil that extends outside the box ok?



#104 BalticBandit

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Posted 23 May 2013 - 02:53 PM

Hmm Doug - and how do you know it is a "legal Proto"?  Has it been measured in for an event?  Which event?

 

or are you again making an assertion that you really don't know the answer to and probably should have deferred to the designer builder?



#105 sean9c

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Posted 23 May 2013 - 04:08 PM

doug isn't there a width restriction in the mini rule, is a foil that extends outside the box ok?

J-2-b Maximum beam: 3 metres including mobile keel(s), rudders, daggerboard(s) and mobile mast(s) (including spreaders) regardless their position, boat maintained without heel.
This would indicate that the deployed DSS foil would be included in the 3m Box


#106 Ryley

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Posted 23 May 2013 - 04:10 PM

it's hard to tell from the pictures and there I couldn't find hull measurements for the DSS mini, but with the foil extended it seems to be pretty close to the nearly 10' you're allowed in beam. Looks like around a 6' beam, that gives you nearly 4' in dss foil since the keel is fixed, but until someone publishes some solid numbers, it looks like a guess at best.



#107 Autograph

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Posted 23 May 2013 - 06:21 PM

Foil mech looks very neat, looks like a rubber wheel controlled by endless line?  I would guess it has a stop to avoid it falling out too.  Love the ballast plumbing, light and simple.  Just out of interest, why have the transducers (if thats what the 2 CL fittings are) aft?  new thinking?



#108 Ryley

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Posted 23 May 2013 - 06:25 PM

Foil mech looks very neat, looks like a rubber wheel controlled by endless line?  I would guess it has a stop to avoid it falling out too.  Love the ballast plumbing, light and simple.  Just out of interest, why have the transducers (if thats what the 2 CL fittings are) aft?  new thinking?

I'd bet that's the only part of the boat they can count on being in the water downwind.



#109 laser3818

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Posted 24 May 2013 - 07:54 PM

It looks like there is a trim tab on the keel. This thing should be a rocket upwind.


Attached File  phoca_thumb_l_20130405_quillageDss_206.jpg   149.93K   312 downloads



#110 BalticBandit

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Posted 24 May 2013 - 08:41 PM

I thought the reason for trim tabs were so that you can run a thinner foil section and thus minimize drag off the wind rather than improving upwind perf.  because isn't the tradeoff upwind always between lift and drag?  So if you dial in more trim tab and hence more lift, you also dial in a slower speed?



#111 Sailbydate

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Posted 24 May 2013 - 08:57 PM

I thought the reason for trim tabs were so that you can run a thinner foil section and thus minimize drag off the wind rather than improving upwind perf.  because isn't the tradeoff upwind always between lift and drag?  So if you dial in more trim tab and hence more lift, you also dial in a slower speed?

Better VMG?



#112 laser3818

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Posted 24 May 2013 - 09:03 PM

Trim tabs definitely improve upwind performance because the foil can be set at an angle that eliminates leeway. This makes the hull more efficient because it is moving straight through the water, not sideways at a few degrees. Upwind, the gains from a reduction in hull drag seem to outweigh the increase in foil drag.



#113 BalticBandit

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Posted 24 May 2013 - 09:18 PM

Trim tabs definitely improve upwind performance because the foil can be set at an angle that eliminates leeway. This makes the hull more efficient because it is moving straight through the water, not sideways at a few degrees. Upwind, the gains from a reduction in hull drag seem to outweigh the increase in foil drag.

No, because unlike a gybing board which does do what you are talking about, the LE of the foil doesn't move.  And so what you are doing is changing the foil shape.  To some extent that changes the angle of attack, but I would be surprised if they are dialing in enough TE to change the attack angle that much.  Consider that if the mini is making 5 deg of leeway (which is optimistic)
 

the trim tab seems to be about 30% of the chord.  so to change the AoA from straight ahead to 5deg to weather, the TE of the trim tab has to create a 5 deg plane from the LE to the TE.  So you have an obtuse triangle with one short side 2x the other and the interior angle of the LE angle is 5. 

 

sin(5)=== height of the interior bisector/2units of TE length

2sin(5) = height of the interior bisector in units of TE == 0.17

sin-1(0.17) == 10 deg.  so thats 10 deg of dial in for 5 deg of leeway. 

 

That's a lot of shape alteration.  Think of it you've now created a max draft of 5% (1/3 of the 17% that is the bisector height) at 66% chord position.  That strikes me as quite draggy

 

And that's with just 5 deg of leeway with 10 deg which is more realistic, you have a 12% max draft at the 66% point.

 

Seems really draggy to me... but I've never sailed with a TE trim tab...



#114 ease the sheet!

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Posted 25 May 2013 - 09:10 AM

I thought the reason for trim tabs were so that you can run a thinner foil section and thus minimize drag off the wind rather than improving upwind perf.  because isn't the tradeoff upwind always between lift and drag?  So if you dial in more trim tab and hence more lift, you also dial in a slower speed?

+1

 

the foil can be smaller for the same amount of lift. means less surface area and therefore less drag.

in practice, same lift upwind, less drag downwind.

1 advantage of the non canting keel.

 

i like whats being done, and in some ways it all makes sense, but my money is on the scow



#115 fng

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Posted 25 May 2013 - 09:29 AM

trim tabs kind of lost the power with IRC so to speak. Having sailed with them and seen the gains I don't under stand why more people arn't using them.

I typical mini ( wide body ) actually will sail with the centerline off close to 8 degrees, then if we use your figure for yaw at 5 degress, our keel is still at -3 degrees angle of attach.

In the dds mini the 8 degrees off Cl will be a lot less, but the yaw relative will still be well within the range of a trim tab

Attached Files



#116 fng

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Posted 25 May 2013 - 09:33 AM

I bit of a trimtab play showing typical results

Attached Files



#117 fng

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Posted 25 May 2013 - 09:44 AM

just remember typically the biggest constraint to foil cord lenght and width is structural boundries. this generally always tells you how wide you foil has to be



#118 BalticBandit

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Posted 25 May 2013 - 01:08 PM

Well the immersed yaw isn't the drag issue that gybing boards deal with.  The gybing boards (and the Swing keel, Bilgeboarders are essentially doing this but with two bits of kit) are set up so that the immersed shape traveling in its longitudinally symmetric direction is aligned with the actual Course Made Good that takes leeway into account.  Thus hull drag is optimized.

 

given that leeway on the Series mini's I've seen is on the order of 10-15 degrees, and the Bilge board angles of the Protos are consistent with this, as I said you have to dial in so 20 degrees of trim tab to make this work.  And that's a really draggy shape.  I can't tell from the attached clips what that attack angle is with max deflection. 

 

I do agree that it absolutely allows for a much thinner shape.  But where that pays off is not upwind where you essentially "dial back in" the thickness saved - but in offwind mode where you set it to neutral or even maybe a few degrees negative so that you gain on the downwind even though the tab is doing nothing on that point of sail.

 

 

As to why boats have gone away from it - I don't think they have in the Protos.  But with the swing keels, they just do it differently. With the swing keels they use angled bilge boards to accomplish this with much less fuss and bother.



#119 quasi-expert

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Posted 28 May 2013 - 06:28 PM

In addition to the mentioned hull drag advantage there is also a considerable aerodynamic advantage from trim tabs or asymmetric daggerboards.

In this case with the very wide hull a trim tab is probably not enough though to really reduce the hull's induced resistance.

Hugh have you considered building a rotating keel?



#120 BalticBandit

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Posted 28 May 2013 - 08:20 PM

So Hugh.  Doug Lord is now claiming in other threads here that you told him that his foil design was very innovative and was going to work well.

 

Did you actually tell hi that?  Or is he doing what he did with Julian Bethwaite's comments?



#121 Lummux the Great

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Posted 28 May 2013 - 11:51 PM

So Hugh.  Doug Lord is now claiming in other threads here that you told him that his foil design was very innovative and was going to work well.
 
Did you actually tell hi that?  Or is he doing what he did with Julian Bethwaite's comments?


So, BB,
How many posts on this thread have you used to try to Fuck Doug Lord up the ass? Wanna Buttfuck Old DOugie, take it to general Anarchy! Fucking Piece of Shit.

#122 BalticBandit

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Posted 29 May 2013 - 07:23 AM

Dougie has no business fucking up perfectly good threads with his drivel and Hugh has every right to know that his name is now being used to justify some truly wackadoodle ideas.



#123 Lummux the Great

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Posted 29 May 2013 - 12:27 PM

Dougie has no business fucking up perfectly good threads with his drivel and Hugh has every right to know that his name is now being used to justify some truly wackadoodle ideas.


Then take it to general anarchy or send hugh a PM dumbass..You are killing the thread for the rest of us that are actually interested...

#124 r.finn

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Posted 29 May 2013 - 01:13 PM

SeriouslyBB, you seem crazy. And I've noticed Hugh has stopped answering questions. I'm sure it has nothing to do with you making this a fight for justice and qualified information in the ugliest way possible. Focus on the thread. It could be interesting again.

#125 BalticBandit

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Posted 29 May 2013 - 02:15 PM

I'm happy to focus on the thread.  It was doing just fine until Dougie stuck his nose into yet another class that he is clueless about and will never ever ever get near.



#126 fng

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Posted 29 May 2013 - 11:37 PM

Ok....

 

If we take your 10-15 degrees of your figure and work it backwards

 

we know that heeled a mini will present it's hull centreline 8 or so degrees in the negative direction to lift,

 

so sailing with 9-14 degress of yaw is ideal to get 1-5 degrees angle of attack on the keel, matching give or take your figures.

 

If we look at a proto with canards then depending on camber they have zero lift between -2/4 degrees, so they need to be set in the hull accordingly.

 

Drag increase from a trim tab doesn't really increase that much until the flap projects outside the foil profile presented. In flying we call this induced drag. So tab angles between 3/9 degrees are commonly accepted.

 

In the dds mini the heeled centreline change is greatly reduced, so the presented angle of attack is higher from yaw ( or you set it up for less yaw )



#127 BalticBandit

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Posted 30 May 2013 - 04:19 AM

OK so Im wondering where the heeled number comes from, because a heeled mini moves surface are laterally more in the wider parts of the hull than the narrower ones, so the bow's immersed shape will remain closer to the centerline and the stern will shift further to leeward.  So with a CMG of-14 deg.  wouldn't you actually see a yaw angle of -20 deg?

 

I'm askng because I haven't actually run the numbers and am looking to understand this better.



#128 Lummux the Great

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Posted 30 May 2013 - 09:37 AM

 

OK so Im wondering where the heeled number comes from, because a heeled mini moves surface are laterally more in the wider parts of the hull than the narrower ones, so the bow's immersed shape will remain closer to the centerline and the stern will shift further to leeward.  So with a CMG of-14 deg.  wouldn't you actually see a yaw angle of -20 deg?
 
I'm askng because I haven't actually run the numbers and am looking to understand this better.

 

Do you use software to run hull numbers?

#129 BalticBandit

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Posted 30 May 2013 - 09:57 AM

I said I didn't run hull numbers  that's why I'm asking



#130 fng

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Posted 30 May 2013 - 11:33 AM

As the mini shown heels the axis of the hull rotates in a delta form. 8 degrees give or take as shown.

 

I was playing with foil placemnt at the time. so look at the aqua lines as CL and heeled CL, then yellow for resultant direction through the water

 

all based on windward sailing

 

I designed this hull to work this way. Some of the earlier hull forms will not heel in a delta ( or as much of a delta )

Attached Files



#131 fng

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Posted 30 May 2013 - 11:50 AM

With this hull I was trying to get the heeled water plane close to symetrical and reduce the wetted surface.

the hull on the far right has the keel root out of the water, so a faily good gain in lever arm with the CB shift

 

A lot of canters rake the pin down fwd 3 degrees to induce angle of attack on the fin when at full cant to aid in righting moment. kind of a reversed dds

 

with this hull form as it heels it naturally does it by the hull rotation alone ( look at the bulb relative to the waterplane )

 

So yes watching the dds mini with a lot of interest

 

Attached Files



#132 BalticBandit

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Posted 30 May 2013 - 12:55 PM

As the mini shown heels the axis of the hull rotates in a delta form. 8 degrees give or take as shown.

 

I was playing with foil placemnt at the time. so look at the aqua lines as CL and heeled CL, then yellow for resultant direction through the water

 

all based on windward sailing

 

I designed this hull to work this way. Some of the earlier hull forms will not heel in a delta ( or as much of a delta )

So I'm not sure I'm reading your image correctly, but I what I see is that the keel on centerline (Green line)  remains aligned fore aft

 

Now the immersed hull shape has about an 8 degree "point" angle WRT the centerline of the hull

 

Yet the compass still is on centeriine.   and we know that the Mini's are TRACKING WRT centerline of the hull a negative 10 degrees.

 

So in fact you need (according to how I'm reading your modeling) to "foot" the hull by 18 degrees to have the Fore-Aft immersed hull to align with the measured CMG

 

 

What am I getting wrong?



#133 fng

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Posted 30 May 2013 - 04:36 PM

i think you are adding the two together when you should be subtracting the yaw

 

the two bold yellow arrows indicate the yaw forces for the sake of the drawing.

 

so heeling rotates in the negative, and yaw skids in the positve

 

 

 

 



#134 BalticBandit

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Posted 30 May 2013 - 08:50 PM

But I dont see that heel rotates yaw in the negative,   a straight line down the centerline of the immersed body goes from the bow (which remains immesed) to a point somewhere between the midline of the hull and the stb quarter.   Now over the length of the hull that's at least 3 degrees  of leeward movement at the stern and ZERO movement to leeward at the bow.  How is that not an INCREASE in relative attack angle of the hull by 3 degrees?

 

what am I missing?



#135 quasi-expert

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Posted 30 May 2013 - 09:16 PM

First of all I think 10 degrees of leeway is a lot. I am no mini expert, but seems a bit much to me.

Secondly I am not sure if I understand you correctly, but I get the impression you want to get induced resistance of the hull to zero?

For a standard symmetrical keel foil you will probably have 5° (or maybe 10° for minis, see comment above) angle of attack to balance the side force from the sails.

In upright condition the hull will also have an angle of attack of 5°. As soon as it heels you have to add the angle between centerline and zero lift angle of the immersed volume to the keel's angle of attack to get the angle of attack of the hull.

For wide hulls this can easily be more than 10° hence why I suggested a rotating keel instead of a trimtab.



#136 diggler

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Posted 31 May 2013 - 09:25 PM

the trim tab seems to be about 30% of the chord.  so to change the AoA from straight ahead to 5deg to weather, the TE of the trim tab has to create a 5 deg plane from the LE to the TE.  So you have an obtuse triangle with one short side 2x the other and the interior angle of the LE angle is 5. 

 

Dude, if you are gonna ride others for not having a clue about how sailing actually works, essentially to the death of an otherwise most interesting thread, you better be damn sure you have your facts straight when you open your mouth. The above is completely incorrect. There are equations, such the one that be found on page 194 of "Hydrodynamics of High Speed Vessels", which can approximate the zero lift angle of attack of a foil with flap. Basically, for a "normal" size flap the ratio is pretty much 1:1 for small flap angles. This means if you want to change the zero lift line of the keel by 5 degrees, you deflect the flap 5 degrees. Not 10 degrees. 



#137 BalticBandit

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Posted 05 June 2013 - 07:04 AM

Diggler, I'm happy to admit when I'm wrong.  I've not looked up the zero lift angle so I'll happily take your word for it and learn something.

 

 

Quasi - as it was presented above, the idea of a trim-tab is like that of a gybing CB.  Namely to drive the induced hull resistance to zero if possible. As for leeway of 10deg.  That's roughly what I observed sailing next to a series Mini on a 49er.  10 deg leeway isn't that bad actually.  It means that if you are sailing an TWA of 33 deg you are making a CMG of 43 deg.  About right for a boat of that size.   Again, I'm happy to be told I'm wrong



#138 fng

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Posted 05 June 2013 - 08:13 AM

I think how you came accross intitally was confusing leeway with yaw, ( well it was for me )

basically a tacking or gybing centerboard/keel will work in the same way as a fixed with a trim tab, lets just forget the science. they will reduce leeway buy presenting a better lift profile.

yaw is the twisting effect of the boat as it sails through the water.

go sail your/the 49r with just the mainsail, you should experience adverse yaw up wind.

a wide bodied mini has lots of other issues when heeled which revole around yaw and heeled cl projection



#139 BalticBandit

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Posted 05 June 2013 - 12:57 PM

No - this has been discussed to death in Dinghy Anarchy (and I started from the same place you were) - but the experimentation and analysis by folks like Paul Bieker and Julian B is quite solid.  Gybers/Trimtabs cont change the leeway at all.  As Quasi pointed out,   The net AoA of the sails and the keel are the same (well almost but the diff is minor) regardless of the hull orientation.   And what a gyber/trim tab does is change the AoA of the keel to be offset to weather.  This allows the hull to rotate to leeward.  The sailplan is then adjusted so that it has the same AoA wrt the wind (and also the keel's AoA that it would have under "normal" circumstances.

 

So in effect the only thing that changes is that the hull yaws to leeward a bit.  And since the boat is making leeway, this means that the hull is less crosswise to the CMG through the water.  Hence it presents less drag.  Hence for a given sail area you go faster.

 

Observationally I put the leeway of a proto Mini in flat water and moderate breeze at around 10 degrees.  I'm open to being wrong as I've only observed them sailing next to one particular one and not one any or even seeing that large a cross section of them



#140 fng

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Posted 05 June 2013 - 10:57 PM

without answering in the style of yourself and the early Doug with a no..... if you look at the results in post 116 you will clearly see that the foil section with 6 degrees of flap is producing approximately 25% more lift in total so the given section is producing more lift. But it is only a small part of the picture.

If you turn it into aviation terms of say a glider wing loading, ideally the bigger the foil ( wing ) the less the wing loading and the better the glide slope ( leeway ).

this all comes with penalties, drag being the foremost. 

with yachts there are generally boundaries, weather it be the class/box rules, where you sail, or how you transport.

for example we are working on a new keel design for a local boat and have been looking at several test cases based on the gp rules. they give you keel fatness minimums. one boat has a 15% section Very small on paper and looks wow in profile with the skinny trend. the other has a 12% section and looks old on paper with a bigger keel.

the test results show the bigger 12% keel is better to windward.

Both the keels have the same frontal area, so it comes done to surface drag. then it's really L/D.

it's always a compromise

then you've got to get the boat to actually behave on the water as designed on paper

Paul B has done some great stuff that he has kindly made public, nice guy in person as well

Frank and Julian are a legacy



#141 BalticBandit

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Posted 06 June 2013 - 08:02 AM

ok sorry about the style - and thank you for taking the time to bop me on the nose about it.

 

I agree about the loading and the drag issues.  As you say, more lift also means more drag.  My understanding of the curves is that for a given fluid density and target velocity, you have a general maximum for thickness as well as chord (and the two are interrelated since a perfectly round surface generates a lot of lift and also a lot of drag) that you can work within for practical purposes, and different shapes give you slightly different curves based on variability in AoA, flow velocity etc.

 

to me, a TE flap is a mechanism that both offsets the AoA of the foil (since geometrically the TE moves laterally in the flow thus changing the "midline" of the foil) as well as changes, and increases the thickness of the foil. 

 

But my understanding of foil shapes, and I defer to you on this since mine is fairly rudimentary based only on an intro fluid dynamics MechE course from 3 decades ago - is that the resultant shape is not the best lift/drag tradeoff.

 

So to me it seems the primary advantage is the same as it is in dinghies:  since normally you are sailing upwind at the optimized AoA, by increasing the AoA of the keel, you allow the hull to be yawed back to leeward so that the keel remains at the optimized AoA but the hull now presents less form resistance to the CMG (due to leeway made).

 

As someone commented in Dinghy Anarchy recently about gybing CBs in 5ohs... once you are solidly planning upwind, you lock out the gybing action because the hull form drag from leeway is no longer a meaningful factor.



#142 fng

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Posted 06 June 2013 - 09:23 AM

minis never get out of displacement mode to windward, unlike a dinghy. they require a more forgiving ( fatter ) foil section. but also note there intended course is basically downwind all the way. so windward sailing is always a trade off.

What I was trying to achieve with the renderings shown, was that when heeled and sailing to windward the hull shape presented kind off resembled what Hugh's mini is. The one bonus I got was a hull that would happily plane well heeled ( on the comp anyway ).

As you get into fatter foil sections the lift drag between a flapped or cambered section less of a jump than say the 10/11% dinghy sections

airfoiltools.com is quite a good site to have a play, it has sort of replaced the worldofkrauss site.

I don't know if you do figure 8 training in the 49r, but how far apart would the buoys have to be to keep a mini moving without stalling 



#143 BalticBandit

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Posted 06 June 2013 - 04:16 PM

Well I no longer sail the 49er since after my first campaign ended, getting steady crew willing to make that sort of commitment was a problem and I couldn't stand pulling my foot off the gas so often.  so I opted for a Musto.  And I would do a "double 8" trainging (instead of just a single figure 8, two linked 8s with 4 buoys:  3 tacks, set, three gybes take down, 3 tacks, set, three gybes take down.... cuz I found in my 49er that a 3x repetition was necessary for locking in a change.

 

Thanks for the airfoiltools site.  Didn't know about it.  

 

As for a mini doing figure 8s.... the curious thing is that I think a Series would out do a Proto - because of the greater simplicity of the keel.  which gets us right back to the flap issue.



#144 nroose

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Posted 07 June 2013 - 01:39 AM

Is the single figure 8 windward-leeward or even with the wind?  Are the double figure 8s like a box or a row of 4?



#145 BalticBandit

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Posted 07 June 2013 - 07:50 AM

Row of 4...  Usually 2 milk cartons set between two permanent marks in the bay I sailed in (Shilshole)



#146 quasi-expert

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Posted 10 June 2013 - 01:53 PM

No - this has been discussed to death in Dinghy Anarchy (and I started from the same place you were) - but the experimentation and analysis by folks like Paul Bieker and Julian B is quite solid.  Gybers/Trimtabs cont change the leeway at all.  As Quasi pointed out,   The net AoA of the sails and the keel are the same (well almost but the diff is minor) regardless of the hull orientation.   And what a gyber/trim tab does is change the AoA of the keel to be offset to weather.  This allows the hull to rotate to leeward.  The sailplan is then adjusted so that it has the same AoA wrt the wind (and also the keel's AoA that it would have under "normal" circumstances.

 

So in effect the only thing that changes is that the hull yaws to leeward a bit.  And since the boat is making leeway, this means that the hull is less crosswise to the CMG through the water.  Hence it presents less drag.  Hence for a given sail area you go faster.

 

Observationally I put the leeway of a proto Mini in flat water and moderate breeze at around 10 degrees.  I'm open to being wrong as I've only observed them sailing next to one particular one and not one any or even seeing that large a cross section of them

 

Actually with a trim tab or gybing keel you can change the angle of attack of the sails.

I have done a bit of research regarding the effects of alterable keels and IMO the aerodynamic advantages exceed the hydrodynamic gains of less induced resistance of the hull.

It is also possible to sail a bit higher with these keels, but you don't get the full rotation/trim tab angle because of the needed angle between wind direction and sail forces.



#147 BalticBandit

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Posted 10 June 2013 - 02:39 PM

The research from folks like JB and PB is that the aero is not the factor.  consider this, two 5ohs with identical DBs but one is gybing.   the Gybing one doesn't change hull angle from the other but does increase AoA on the DB... both foils are otherwise identical. AGybe Bnorm

 

If in fact Agybe can carry a higher AoA on the DB than so can Bnorm because the foil shapes are identical  So at some point we will reach an optimal AoA for the DB  and both boats will be running that AoA.

Now your claim is that in this configuration somehow magically Agybe is able to pull their sheets in tighter on the sails in a way that Bnorm is somehow prevented from doing?  What prevents this? both have identical rig configurations so slot effect etc is identical.  QED nothing limits Bnorm from matching AGybe in both

 

  • Foil AoA

     

     

  • Sail AoA

  So something else must be in play because we know that in sub-plaing speeds, the gyber is faster.

And the reason is that even though both sets of keels and both sets of sails are operating at the same AoA,, the hull angle of the Agybe is "lower" (essentially rotated "bow down" WRT the Keel and Sails)  and thus presents less drag due to the leeway made.  And that drag reduction is what increases net speed



So for a given amount of lift/drag out of a keel a tabbed or gybed keel cannot "sail higher" than a similarly shaped keel that is not tabbed or gybing.  It just doesn't work that way.



#148 LeoV

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Posted 10 June 2013 - 03:08 PM

you sail faster because of the rotated hull, so you have less leeway effect on the same distance, so it looks like you sail higher.



#149 BalticBandit

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Posted 10 June 2013 - 04:08 PM

Well except that you track the same course, if anything because your hull is generating slightly less lateral resistance you might actually make a bit more leeway (I've not seen the numbers on this).  But you do have better VMG.  but VMG isn't pointing



#150 Poida

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Posted 12 June 2013 - 10:57 PM

Raps, once immersed, surface tension of a surface has no bearing on boundary flow effects - this has been discussed to death in other threads.  Unless you are changing the sheer characteristics of the water column by introducing aeration, or some other low viscosity liquid, once your surface is smooth enough that boundary layer effects dominate, your surface tension has no bearing.
 
As for foiling and my irritation with Doug - frankly he's polluted so many threads not with his "passion" but with his ignorant fanboyism that I now have an allergy to him as do a lot of very good sailors.  Hugh I 'll put it to you this way.  I'm working on funding a 2015 or 2017 go at the Mini Transat.  And even if I dont do that I'm likely to buy one anyway because its a boat that suits the kind of sailing my wife and I both really like.
 
Doug OTOH hasn't sailed in coming onto 2 decades and won't ever by a boat.  Tell me who you would prefer to have a discussion with.

Probably neither of you.

#151 Autograph

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Posted 15 June 2013 - 10:11 AM

Enough technobulshit, to say that the trim tab is the most interesting and exciting part of this boat, is like saying kiwis win because they wear red socks.

Tell us more about the dss foil, and how it makes this boat behave.

#152 BalticBandit

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Posted 15 June 2013 - 05:15 PM

I thought it was because they painted their keels orange :-)

 

Well it will be interesting to see.  It doesn't look like they made the entry for the Mini Fastnet http://www.winchesclub.com/minis650/fastnet650/EN-153-1-2-1--type-.htm  So are they going to make it for the Mini Transat?



#153 Tanton Yacht Design

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Posted 19 June 2013 - 08:51 PM

Attached File  243pic8_crop.jpg   27.51K   127 downloads

Not a Mini, but a Monomaran.



#154 bruno

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Posted 20 June 2013 - 05:44 PM

monomarans are good

#155 quasi-expert

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Posted 20 June 2013 - 06:21 PM

The research from folks like JB and PB is that the aero is not the factor.  consider this, two 5ohs with identical DBs but one is gybing.   the Gybing one doesn't change hull angle from the other but does increase AoA on the DB... both foils are otherwise identical. AGybe Bnorm

 

If in fact Agybe can carry a higher AoA on the DB than so can Bnorm because the foil shapes are identical  So at some point we will reach an optimal AoA for the DB  and both boats will be running that AoA.

Now your claim is that in this configuration somehow magically Agybe is able to pull their sheets in tighter on the sails in a way that Bnorm is somehow prevented from doing?  What prevents this? both have identical rig configurations so slot effect etc is identical.  QED nothing limits Bnorm from matching AGybe in both

 

  • Foil AoA

     

     

  • Sail AoA

  So something else must be in play because we know that in sub-plaing speeds, the gyber is faster.

And the reason is that even though both sets of keels and both sets of sails are operating at the same AoA,, the hull angle of the Agybe is "lower" (essentially rotated "bow down" WRT the Keel and Sails)  and thus presents less drag due to the leeway made.  And that drag reduction is what increases net speed



So for a given amount of lift/drag out of a keel a tabbed or gybed keel cannot "sail higher" than a similarly shaped keel that is not tabbed or gybing.  It just doesn't work that way.

 

Imagine those two boats sailing an identical course, and let's say sailforces are equal to keep things easy (meaning the AoA of the DB are practically equal) then the centerlines of the boats will not be parallel which affects the aerodynamics.



#156 BalticBandit

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Posted 20 June 2013 - 09:38 PM

The centerlines of the boats will be different but the sails will be trimmed to adjust for that.  Aero will be the same.



#157 Ryley

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Posted 17 July 2013 - 07:01 PM

any updates?



#158 Ryley

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Posted 03 September 2013 - 07:16 PM

so... it appears all the news on the interwebs about this boat is as old as this thread. anything new? is it sailing? testing? so fast it has to remain secret? so slow it has to remain secret?



#159 r.finn

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Posted 04 September 2013 - 05:45 PM

I'd love to hear an update too.  Even if it doesn't work I want to hear about it.  I think it's a great experiment, and want to compliment the designer for not making any claims before launching.  Any updates would be appreciated.



#160 BalticBandit

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Posted 05 September 2013 - 06:39 AM

Well except the designer did.  He came in here and told us that in his view Dougie knows what he is talking about....

I suspect the boat has failed to qualify for this years MiniTransat and hence the silence



#161 hughw

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Posted 05 September 2013 - 06:26 PM

something called real life, money and time is all so the boat has been sailed a few times only.  V quick downhill, main way too big to get uphill so thats being sorted at the moment, I'm going sailing on the boat after Les Voiles with someone who is very keen to take the boat on for the next couple of years ( and extremely qualified in all areas to do that too ) to develop and sort for the transat after this one.

Disappointing not to be doing this one, but getting sponsorship is ****in hard...

So no chance to qualify, no big story one way or another. 

What do we know so far?  Not a lot, we know what it should and can do downhilll and no surprise there, balance is really nice and again thats as it should be, sails are critical to make it work and thats the same for any of these types of boats to get the rig to match up with how the rest of the package works.

 

FYI the Q30 won its first race by 15min in a 90 min race so thats doing what it should, don't expect less from this petit monstre:)



#162 BalticBandit

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Posted 06 September 2013 - 09:33 AM

Hint Hugh - I realize RL sucks up time, but it shouldn't take a gybing poke from a curmudgeon like me to get a response out of you.  One of the sad realities of this "social media connected world" is that you need to create a social media engagement strategy that is as important to your agenda as filing your taxes.    For example if you set aside 30 minutes every other week to post to FB, SA and on a blog - just a blurb - you will find much more positive response.

 

Now this happens to be an area of expertise of mine, so I'm happy to offer you consulting services for that.   And if the boat is in France, those could be paid off with a ride or two :-)



#163 Little Bleck

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Posted 28 September 2013 - 07:02 AM

Looks like a pretty roachy jib. Any issues with taking it through in the light?
HW


Looks like a running backstay.

#164 haligonian winterr

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Posted 09 October 2013 - 11:58 PM

Bit late, but where do you see the runner?

HW


Looks like a pretty roachy jib. Any issues with taking it through in the light?
HW


Looks like a running backstay.





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