Plywood Foil Board

[daspi]

After building a few light wind plywood boards, I am going to build a plywood foil board. Initially everyone was telling me that a no volume board will not work well. Over the last couple of years, more and more manufacturer have flat foil boards in the line up, which now encourages me to finally give it a try.

Going to build a mix between the Naish Hover and the Eleveight Carvair. I'm going to give it a generous amount of nose rocker. Also adding a bit of extra lenght as these are only 130cm. Other than that, I plan on placing one center strap in the front, mainly to help water start, and a fixed position for the mast attachment.

So far work is going well and I have to decide where to put the mast. This is where I want your input folks. Is a single attachment point sufficient or are you really playing with moving the mast back and forth on these tracks? Does a larger wing maybe require you to move the mast more forward? Smaller wind more back? Depending on your feedback I might consider drilling a seconds position.

[grigorib]

You might want to set up multiple mast attachment points.
With a large wing you might be standing over rear mast plate bolt, for fast/small wing your thumb will be behind rear mast plate bolt so I’d do two attachments about 50mm apart.

Flat thin boards work perfectly - with a large wing all you do is flying and almost never touch water. And if you do and push the pocket board under water you’d still ride it up and out.

You can do fairly thin 1/4” upper deck reinforced with another layer of the centerline (mast width) lower deck, like our old skateboards were. Or if you can manage single layer concave construction, like modern ones are made - that would be awesome too.

[daspi]

Thanks @grigorib. Good info. So I want space for my foot behind rear attachment points, this is what I was wondering. Seems like the sensible thing will be drilling my first set of holes at about the center of where the Eleveight mast slot. I plan on shortening the board once I get the feel for riding it. I'm still at the early stages of foil riding. Touching down for each jibe. Hardly ever get around my jibe. Stressing about foot switch when up above water. This is why I want to stay at reasonable length and nose rocker initially. Second build will be more like a real pocket board. This will be my learning/intermediate board.

[direnc]

I build a couple of plywood foilboards last summer. I was inspired by the one built by forum member Plummet. I used two layers of 4mm cheap plywood. Put a 20cm wide plywood strip in the middle from the mast mount to the foot hook. Also gave the deck some concave to make the boards stiffer. One is 135cm, and the other 140cm. About 46-48cm wide. They ended about 4kg. A bit heavy, but not that much. There are some production boards that heavy. They do work, but I liked the thicker boards I build in the past better. 2-3cm thickness is what I prefer. I am now building boards with 2-3cm XPS foam sandwiched between 3mm plywood skins. I need to fill insert/hook holes now and decide how much glass to put on....

These are the ones I built last summer:

[JakeFarley]

Any problems with a plywood board sinking or sitting so low in the water that it is hard to see after you fall off?

[daspi]

I build a couple of plywood foilboards last summer. I was inspired by the one built by forum member Plummet. I used two layers of 4mm cheap plywood. Put a 20cm wide plywood strip in the middle from the mast mount to the foot hook. Also gave the deck some concave to make the boards stiffer. One is 135cm, and the other 140cm. About 46-48cm wide. They ended about 4kg. A bit heavy, but not that much. There are some production boards that heavy. They do work, but I liked the thicker boards I build in the past better. 2-3cm thickness is what I prefer. I am now building boards with 2-3cm XPS foam sandwiched between 3mm plywood skins. I need to fill insert/hook holes now and decide how much glass to put on....

These are the ones I built last summer:

Nice man. Just what I want to do. Can you tell me why you put 20cm strip? Where did you put it, bottom? Can you show me a picture? I was considering putting something like this on the bottom too to make the whole board stiffer and reinforce the mast base attachment area. Not sure if needed.

What kind of cheap plywood did you end up using?

Could you put a link to your inspiration from that other member please? Can't find it.

[direnc]

I build a couple of plywood foilboards last summer. I was inspired by the one built by forum member Plummet. I used two layers of 4mm cheap plywood. Put a 20cm wide plywood strip in the middle from the mast mount to the foot hook. Also gave the deck some concave to make the boards stiffer. One is 135cm, and the other 140cm. About 46-48cm wide. They ended about 4kg. A bit heavy, but not that much. There are some production boards that heavy. They do work, but I liked the thicker boards I build in the past better. 2-3cm thickness is what I prefer. I am now building boards with 2-3cm XPS foam sandwiched between 3mm plywood skins. I need to fill insert/hook holes now and decide how much glass to put on....

These are the ones I built last summer:

Nice man. Just what I want to do. Can you tell me why you put 20cm strip? Where did you put it, bottom? Can you show me a picture? I was considering putting something like this on the bottom too to make the whole board stiffer and reinforce the mast base attachment area. Not sure if needed.

What kind of cheap plywood did you end up using?

Could you put a link to your inspiration from that other member please? Can't find it.

I ordered the plywood online. The lighter colored one is poplar. The darker one is okoume (leftover plywood from previuos twintip build). Any type of plywood should work, but lighter and cheaper is preferable.
I put the strip between the top and bottom skin, 10cm from the back of the board. One cannot tell there's another layer in the middle of the board.

The inspiration was this one from Plummet:
viewtopic.php?f=199&t=2394150&p=1000512 ... l#p1000512
Concave deck is very clever. Makes it super stiff. Mine has 18mm of concave on the deck. I bolted down a 15x60cm block of wood from the back of the board while I raised the sides of the board with two strips of 18mm wood. Raised the tip with some blocks and put some weight over the board, and screwed down some parts of the edges if necessary.

[direnc]

Any problems with a plywood board sinking or sitting so low in the water that it is hard to see after you fall off?

When paired with a very heavy aluminium foil (more than 4kg), it was a bit of a problem. But with a regular, sub 4kg aluminum or carbon foil, it's not an issue.

[daspi]

@direnc Alright, so if you want to put in concave to the board ans strap it down as you describe, how will the concave be permanent? Did you glass it, or just two layers of plywood glued together? Did you put in the nose rocker at the same time you clamped the concave?

[TomW]

I suppose for learning a heavy board is merely an inconvenience. As you improve you'll really want a lighter board. Try to find 10-15mm thick 80kg/m3 corecell or divinycell and glue those together to get rocker, then laminate. It will be much lighter.