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29er Outhaul and Cunningham Control Combined


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So, I just stumbled across the 29erC rig videos from 2 years ago and I noticed the implementation of the combined outhaul cunningham control. I sail 29ers currently and I don’t change my outhaul very dynamically but I play the other controls a lot so this caught my attention. It looks like this method could be the best way of changing the camber mid-race but I don’t know if it would be entirely legal to use it on the standard rig. I wouldn’t be adding any additional hardware or purchases, but to my understanding the 29er is a “closed” class (can only change things that the rules specifically say you can change). I might try this out on an older 29er that I’ve been refurbishing. Just looking to see if anyone has tried this out on the standard rig and some feedback from those who have seen it in action on the carbon rig would be nice too?

Here is the video:

I also found this really cool thesis paper on the standard rig vs the carbon rig if anyone is interested in it:

29er Thesis.pdf

 

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@cooperdelbridge I hadn't seen those videos before, thanks! 

@JulianB I just wondered if you had any additional information about the winglet in this video? I assume its using the end plate effect, is it noticeable?

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The short answer is yes they work.

The justification for that answer is from the WING program and it acheiving a drag singnature which is not explainable other than from various drag reductions that things like the winglets afforded.     Basically the boat performed better than prediction, and if you fold them down (and paper clip them flat) it performs "less well"!

The initial ones where too big, and the parasidic drag was excessive.   You also have to get the head agnle just so and it has to be intergrated with sail design, it's not a bolt on extra, it's more a intergreated drag reduction excersize.

I have no data from the 29erC rigs other than they are still all standing, the jibs are completely trashed (and they are the new version) but Mains still look good, don't think they have broken a mast yet and are sailing about 6 days a week, 6 hrs a day.     Let me see if I can find a photo for you.

                        jB

 

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Just found the photo, you can see the winglets at the top, but I have no data on these rigs.

I was in Rizhou for 49ers & FX, I did not even know 29erC's would be there.    I think there where 8 of them.

                             jB448916919_29erCrigRizhouChinaMay2019.thumb.jpg.478b5ca2699ca8374f0fcfd14cff5971.jpg

 

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19 hours ago, JulianB said:

The short answer is yes they work.

The justification for that answer is from the WING program and it acheiving a drag singnature which is not explainable other than from various drag reductions that things like the winglets afforded.     Basically the boat performed better than prediction, and if you fold them down (and paper clip them flat) it performs "less well"!

The initial ones where too big, and the parasidic drag was excessive.   You also have to get the head agnle just so and it has to be intergrated with sail design, it's not a bolt on extra, it's more a intergreated drag reduction excersize.

I have no data from the 29erC rigs other than they are still all standing, the jibs are completely trashed (and they are the new version) but Mains still look good, don't think they have broken a mast yet and are sailing about 6 days a week, 6 hrs a day.     Let me see if I can find a photo for you.

                        jB

 

That's really interesting, thank you.

So I imagine the difference between the end plates in a decksweeper and a winglet is that at the foot we already have a hull, so we are just using what's already there to seal the sail but at the head we have to add material which has weight and drag penalties? So although the aerodynamics of the rig would like a large winglet, the added material means you have to compromise?

 

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There is a huge amount of air gong from the windward side of the main low down, spiralling down and around(the boom) and upwards on the leeward side of the main, even more so in a cat rigged boat.  Huge vortex!   There is that great bit of footage, some foiling Trimaran (Mantis, single handed) that has graced these pages where he let off a smoke flare and you can see the spiral. Prior to that, we did a series of tests to see how effective the cuff luff is, and we have tweaked its size so it’s just big enough 95% of the time.   (If you really squeeze on main (49er) and don't bend the knees, you get a massive spiral, massive amounts of drag, but bend the knees and ease the main as little as 150mm and it cleans up within 0.5sec,   Really interesting!   That was 1994-5, we re-tested the ground in 2012, and we have redone it recently, that is leading us to making the 49er cuff bigger cord (for-aft) and going further down right now with the new sail spec.      

Add to that we did an experiment with foiling moths, where we took a bit of string and tided it between the spreader and deck, probably 400mm away from the mast on one side and 200mm on the other, and then went sailing with me in a speed boat taking photos/videos to get a grasp on span-wise drift.     So the up-lift, the screwing of the air in the front 10% of a non-end-plated moth main is at least 10° up on the lee-side bit more at 200mm, but still a full 10° at 400mm.   I have the photos somewhere see if I can dig them out.

Steve Thomas said a few days back that the single biggest speed advancement in Moths has been end plating the sail to the deck, and as I said above, even more so on a cat rigged boat.      Now just look at what the AC's are doing.     And I do laugh at the shit we coped back in the mid 90's with the 49er.   Inertia is an almost overwhelming force and you just need to ignore doomsayers.

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

Mast head, so the photo that twigged me to this was

1786616452_VORCapeTown.jpg.16e69b7ff744491b015c4665a9ea9ffe.jpg

VOR 75’s coming out of Cape Town.      Just think about the 1000’s and 1000’s of tonnes of air that is been churned by those square heads.

The energy to churn those countless 1000’s of tonnes of air is coming from the boats, and in turn is slowing the boats down.     Its energy that could be far better spent.

The design of the 49er and 29erC square heads is very different to those of VOR 75’s, the biggest one being we don’t have to hang onto a mast head code zero and for the mast not to fall down in the middle of the roaring forties in the middle of the night.

The weight reduction of the Carbon-mast and Square head mains inc the dropping of the CoE so greatly trumps the downside that they are over-whelming-ly more efficient but more than anything else that are vastly more enjoyable to sail, mostly because of the reduction in weight aloft so a significant reduction in inertia.      The reason that just about any 49er sailor can now go out in 25-30knts and not just get around the course but have fun, is due to this reduction (in inertia) and that’s across the whole fleet, and not just the Rock Stars.    In the 49er, it has been stark, black and white!

But if not done well square head have the potential of generating a tip-vortex.      Purely because of it’s extra “head board” length, the FX is at greater risk of doing this than the 49er is.    Plus if its been designed well the pressure differential at the mast head will be small.   Far smaller than the pro-rata VOR 75 pressure differential that you can see so vividly in that photo.

Winglets have been around for years, just look out the window of any airliner.   There are various ways of doing it, and in the wind-turbine industry where length is not such a bit deal, they do it by feathering of the tips.    I used to make model aeroplane propellers with my father and he had a (then) 40year old book on the theory of propellers design.   Modern Turbines do it by end plating just like the Moths/ AC’s are doing it at the bottom.

With the WING and the 29erC, they are particularly well design square heads, the WING more so, and we started with an almost ½ cord length winglet, but we are down to something much closer to ¼ cord, if that.    Width (per side) is 4 x mean camber so it did not alter much.

No theoretical data, only a bit of pretty elementary empirical intuition that is driving this (the same intuition that drove original cuff luff back in the early 90’s that’s now all over Moths, A-Class and ACs) and the most telling boats is the WING.   I’m sure that there is plenty of info off the 29erC, but we have moved on from there.

 

                                   jB

 

 

 

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1 hour ago, JulianB said:

There is a huge amount of air gong from the windward side of the main low down, spiralling down and around(the boom) and upwards on the leeward side of the main, even more so in a cat rigged boat. 

This is why "conventional" mains are so flat in the bottom. If you have fullness, the air wants to dive under the foot, rather than continue around the camber. By doing the deck sweeper, not only do you eliminate that air movement under the sail that Julian describes, which makes the bottom of the sail work properly but it allows you to increase camber low down. The combination reduces the height of the centre of effort of the rig, which works for all boats but on a foiling boat, it is huge as it reduces the loads on the foils.

People have played with end plating the top of the rig, without a lot of success, but I see this development above as a bit different. I think it is about organising the airflow off the back edge of the top of the sail which is a vortex and if that can be reduced, it should be beneficial. Another thing to add the the A Class test program!

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On 3/15/2021 at 9:59 PM, JulianB said:

Just found the photo, you can see the winglets at the top, but I have no data on these rigs.

I was in Rizhou for 49ers & FX, I did not even know 29erC's would be there.    I think there where 8 of them.

                             jB448916919_29erCrigRizhouChinaMay2019.thumb.jpg.478b5ca2699ca8374f0fcfd14cff5971.jpg

 

Holy hell and i thought i had trashed practice sails... 

(circa 2009)

No photo description available.

 

Hey cooper/OP, give me a shout if you've got any questions about 29er's and dealing with old boats. I'm a SYSP alum and some people probably still remember as the 29er obsessed dude (still am). I get down to Sarasota once or twice a year these days and could help you out in person as well. Shoot me a PM if you're interested. 

 

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