I am making a 93cm front foil wing out of laminated ply wood. Using ply made it easy to see the different thickness (wood shades) of the ply as I sanded. First using a hand held belt sander. Then fishing it off by hand with sand paper, still some sanding to do around the top where the fuse should connect. I am planning to fiber glass it. The wing has a tiny bit of flex right now when I push down on the center of it when it's laying across chair arms. Hope that doesn't cause to much issue down the road.

What type of fiber glass would you guys use in this situation?

I am considering making a wood fuseledge extension like in the pic below, length of this fuseledge including the wood is about 95cm. It may need some sort of renforecement at the joint to make it a solid connection where the wood fuse meets the aluminum one. Maybe putting some sheet metal on the bottom part where the bolts go. Will have to figure that part out.

Would extending it in the front through off the balance of the foil causing too much front foot pressure needed?
The ruler it not a extra wing

Just consider that the front wing and any associated attachment is lifting your entire body weight, the entire board and rig plus any dynamic loading. These loads are significant so anything you build has to withstand them.

As a super rough test I'd grab the wing, support it 2/3 of the way out each span and bounce on the middle of it with one foot. If it can't handle that you're gonna have a bad time. Drill the mounting holes in the centre first too.

I'd reconsider the front extension idea

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CJW said..
Just consider that the front wing and any associated attachment is lifting your entire body weight, the entire board and rig plus any dynamic loading. These loads are significant so anything you build has to withstand them.

As a super rough test I'd grab the wing, support it 2/3 of the way out each span and bounce on the middle of it with one foot. If it can't handle that you're gonna have a bad time. Drill the mounting holes in the centre first too.

I'd reconsider the front extension idea

Thanks for the advice CJW. I did not bounce on it as it felt prtty flexy with prob 75% of body weight on it
I did chisel out the channel and drill the holes for the bolts to mount to the fuse. Figured if I've already gone this far mine as well finish it off. Btw I have ditched the extension idea

I think I may have made it too thin. It's weight is much lighter then my NP g10 front wing. It was pretty easy to shape and if it breaks on it first run o well. It cost me zero $ so far and it was a fun thing to make.

But I see why 99.9% of people just buy production wings.

At this point, you'll need to either use a lot of glass or decent amount of the expensive black stuff (cf). Have you seen Rob Rock's videos of building a wing? No sense in putting in all this work on something you think is probably going to snap the first day out.

Aside - this would have been a good time not to use a plywood as half the plys aren't helping you: the grain is not aligned with the stress. Plywood's virtue (other than being less expensive) as a building material is that it is relatively uniform in strength in different directions so useful as a "skin" - floors, roofs, etc (yes, it still has a "grain" in many sizes as the number of plys are odd). A laminate where all the plys run in the same direction would be a different animal. But, this is the fun part of the process: learning how and why things are the way they are. Good luck!

Yes Rob Rock has some very top notch stuff here


Didn't know that much fiber glass and carbon could make it that stiff for such a thin ply.

Bet that foil wing could compete with the top guys like pryde and starboard.

I am thinking of making another wing (Robs inspiration), as the first was just a prototype
I know I'm no rob and an running a pretty amature operation compaired to his builds.

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Bet that foil wing could compete with the top guys like pryde and starbooard.

Said in jest I'm assuming? in the racing world anyway, not even going to be remotely close.

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Paducah said.. >>>this would have been a good time not to use a plywood as half the plys aren't helping you: the grain is not aligned with the stress. Plywood's virtue (other than being less expensive) as a building material is that it is relatively uniform in strength in different directions so useful as a "skin" - floors, roofs, etc (yes, it still has a "grain" in many sizes as the number of plys are odd). A laminate where all the plys run in the same direction would be a different animal. But, this is the fun part of the process: learning how and why things are the way they are. Good luck!

What you say is true, but I don't think that's relevant. If you're relying on the timber's tensile strength, it's going to snap!!!!!!!!!!!

It needs either glass or carbon fibres to take the tensile loads, the timber should only be there for compression.
My recent fins have been end grain palm, before that end grain balsa. This is where timber has it's best compressive strength, but end grain balsa is hard to shape, it's density varies too much. The end grain palm works a treat though, only problem is thin sections are very fragile, (the advantage of ply). I shape one side, then glass over it, before shaping the other side. This holds it together.
Not sure you could get a single piece of end grain palm big enough for a foil though, it would probably need to be joined.

Here's some picks.


so fin marked out and a layer of 4oz cloth over the top.




Using a tiler's profile gauge to check the foil.






And here's the carbon cut out ready for laminating on

I see your point but in a way he already is relying on the wood core for strength since he's only using glass so far (I'm under the impression that cf is out of the budget) and already doing the bendy-bendy backyard stress test. Wood, in grain, is surprisingly strong which is why bike frames can be built of it and still have a high performance weight (ie not heavy). The glass on a wood wing is as much for protection as strength.

From some of the stuff I found under a quick google search wood can be 8 times stronger with the grain than across. (I'm open to someone more knowledgeable providing better numbers).

Here's one. The bike worked well. The company, however, didn't and just folded.

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Nice fins, btw!

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Paducah said..
I see your point but in a way he already is relying on the wood core for strength since he's only using glass so far (I'm under the impression that cf is out of the budget) and already doing the bendy-bendy backyard stress test. Wood, in grain, is surprisingly strong which is why bike frames can be built of it and still have a high performance weight (ie not heavy). The glass on a wood wing is as much for protection as strength.

From some of the stuff I found under a quick google search wood can be 8 times stronger with the grain than across. (I'm open to someone more knowledgeable providing better numbers).

Here's one. The bike worked well. The company, however, didn't and just folded.

%2Ccompress&ch=Width%2CDPR&crop=entropy&fit=crop&h=347&q=60&w=616&s=6295ae8ccea1affeeafc3d54b0989c3e

Nice fins, btw!

Yes that's why I had the grain running long ways on the wing. But ply wood has multiple layers each piece having a opposite grain direction and stiffness. Which means it will flex a lot but not break so easy compaired to wood. The more stiff the wood the easier it will crack.

This link explains the difference between ply and pine.

www.google.ca/url?sa=t&source=web&rct=j&url=http://www.differencebetween.info/difference-between-pine-wood-and-plywood&ved=2ahUKEwiMo9X49p_eAhWDq4MKHbunCSAQFjAAegQIARAB&usg=AOvVaw0kGQ0fd8cPd2ZeBkZ2w2h6

I think I should shape my next wing using pine wood. I think ply was a bad idea because it's flexyer. Im not a wood expert but think pine has good stiffness properties.
Thoughts

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CAN17 said..

Paducah said..
I see your point but in a way he already is relying on the wood core for strength since he's only using glass so far (I'm under the impression that cf is out of the budget) and already doing the bendy-bendy backyard stress test. Wood, in grain, is surprisingly strong which is why bike frames can be built of it and still have a high performance weight (ie not heavy). The glass on a wood wing is as much for protection as strength.

From some of the stuff I found under a quick google search wood can be 8 times stronger with the grain than across. (I'm open to someone more knowledgeable providing better numbers).

Here's one. The bike worked well. The company, however, didn't and just folded.

%2Ccompress&ch=Width%2CDPR&crop=entropy&fit=crop&h=347&q=60&w=616&s=6295ae8ccea1affeeafc3d54b0989c3e

Nice fins, btw!

Yes that's why I had the grain running long ways on the wing. But ply wood has multiple layers each piece having a opposite grain direction and stiffness. Which means it will flex a lot but not break so easy compaired to wood. The more stiff the wood the easier it will crack.

This link explains the difference between ply and pine.

www.google.ca/url?sa=t&source=web&rct=j&url=http://www.differencebetween.info/difference-between-pine-wood-and-plywood&ved=2ahUKEwiMo9X49p_eAhWDq4MKHbunCSAQFjAAegQIARAB&usg=AOvVaw0kGQ0fd8cPd2ZeBkZ2w2h6

I think I should shape my next wing using pine wood. I think ply was a bad idea because it's flexyer. Im not a wood expert but think pine has good stiffness properties.
Thoughts

You must not have seen any carbon or glass wings break yet ....

Im building a wing that is 80cm in span and 17.5 cm wide at its thickest point and around 180 sq in or 1161 sq cm.
For light wind what is a good size front wing?

From my experience with fins, which are under less stress than a wing. Timber just isn't strong enough ,for the thickness an efficient foil needs. Glass is about the same tensile strength as carbon, it 's just no where near as stiff, so probably allows the timber to take some of the load. Where as carbon being ultra stiff has to take all the load. Unidirectional stuff would be the go, that way all the fibers are sharing the load. Maybe one layer of cloth over the top to stabilise things.

I'm fairly sure if there's only one layer of cloth over any timber, the foil will give way, probably as soon as you start to fly.

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CAN17 said..
Im building a wing that is 80cm in span and 17.5 cm wide at its thickest point and around 180 sq in or 1161 sq cm.
For light wind what is a good size front wing?

So if your foil is around 10% thickness to chord ratio it's only 1.7cm thick. I bet there's a timber engineering guide somewhere , that will give you feasible loads for thickness and span.

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Paducah said..
From some of the stuff I found under a quick google search wood can be 8 times stronger with the grain than across. (I'm open to someone more knowledgeable providing better numbers).

Undoubtedly that's the way timber is supporting the lateral forces on the tree, like branches hanging out.
Cross grain has very little strength, it's not doing anything. And this varies with the tree, try splitting a jarrah log, then a karri one.
But I'm not talking about cross grain, I'm talking about end grain, a different kettle of fish altogether. End grain is taking the down ward force of the tree, it's duty is compression, it's fighting gravitational force of all the tree's weight, at the tree's base.
So in a beam structure, it's ideal for the central element.

I have sanded the top of the new wing. I need to sand the front and side leading edges. I did a stress test on it before I sanded and it held up to 330 Lbs and only flexed slightly. Compared to my fisrt wing made from ply wood it is not even close in stiffness. This model has very long chord length to provide surface area and wanted it to be strong enough. Can post a pic when done sanding.

The next thing I guess I need to think about is how to finish it. Fiber glass seems like the most popular choice. I could varathane or laquer it.

I was also reading about rough vs polished surfaces. Some guys racing sailboats would sand the bottom to give it a rougher surface. Thay say it produces less drag because the rough surface traps water so it is water passing over water and water has less friction passing over water then water passing over a smooth surface. People also say it is in most cases slightly slower to have a rougher surface then polished one. I don't know.
What do yous think.

A few reads here

forums.ybw.com/index.php?threads/smooth-hull-for-racing.178554/

www.google.com/url?q=http://forums.sailinganarchy.com/index.php%3F/topic/154567-rough-hull-could-be-faster-than-smooth/&usg=AFQjCNEN-_95laTnMtUC1oEOrl4vUaLPvA

Wing update: Sanded with 400 grit and chiseled out a channel for the fuse










I plan to make a rear wing larger then the my Neil pryde one. It will be without curved tips like on the new 2019 pryde rear wing as it is too difficult to do and not needed if I have the verticle stab in. My template is 51.5 cm in span vs my pryde one at 42cm, would it be too big. I assume it should be bigger to offset the extra front foot pressure added by the front wing.

Does anyone know what the best wing mounting methiod is. I know the original way is they have flush set bolts set into the wing at the bottom. I need to buy new longer bolts as there are only 2 threads poking through the top of the wing with my current bolts. But I think I would benefit from using 3 washers one on each bolt on the bottom to spread the load more and prevent the wing from teatering and use like a hex head style bolt. This wing is a fair bit bigger then the NP AL one.

Do you think the idea I have with using non flush blots would create excessive drag ( ie 3 washers with 3 hex heads poking out the bottom of the wing)? Just donno if the wing with flush set bolts would make it rigid enough. Willing to sacrifice a bit of drag for a more secure wing mount.