Zandman wrote:
Yes, as a first project I want to go as KISS as possible. Both materials and tools. (e.g. I'd rather wait for epoxy curing)
What I think of doing is:
1) Get 2 or 3 of sheets of wood sized 135x45cm
(2 or 3? How many mm? 3mm? What kind of wood? Where do I find it?)
2) Glue the sheets together, while drying use a 7x7cm square beam and the car to create a rocker
3) Cut a symmetric round/elliptic nose with a template and a saw and then sand the cut
4) Use fiberglass and epoxy at bottom side - Extra glass layers where the foil will mount
(Which epoxy? Which glass? How many layers? )
4.5) Wait to dry
5) Turn the bottom side down and pour extra epoxy at the rails - in the V formed between the dried fiberglass and the wood
5.5) Wait to dry
6) Do Steps 5 & 6 at the upper side
7) Use epoxy and salt at the upper side for grip
8 ) Drill 4x10mm holes for foil and fill with epoxy (using paper tape at the bottom to hold the epoxy)
9) Once the epoxy is dry, drill 6mm hole and use big washer on the upper side and nut at the bottom to hold the foil.
This all sounds pretty reasonable.
1.) 3 layers of 3mm plywood with a full deck pad should be enough flotation and strong. If you can find it, marine plywood like Baltic birch. Any plywood is probably fine though if you glass it. This will sit pretty low in the water, so consider painiting it a bright color.
2.) a gap filling glue like gorilla glue probably best for gluing them together. Plan on some spring back, so put in a bit more rocker than you want. Might take some experimentation to figure out what works.
4.) I don’t know, let’s say 2 layers of 4 oz fiberglass on top and bottom. Strips of unidirectional carbon fiber, a few inches wide, along the length of the board will add a lot of stifness and is cheap and easy to work with. West system epoxy 205 or 206 is available everywhere and good enough. I prefer system three epoxy as it is is a 1:2 mixture instead of 1:5. Fast epoxy in cold environments, slow in warm environments. The thicker the board, the less fiberglass you need, but you want a couple layers of epoxy for waterproofing anyways. Also, you don’t specify glassing the top, but glass the top too. 1 layer glass on top and bottom is a lot stronger than 2 layers on either top or bottom.
5.) not really sure what you mean here by “the V”. Honestly, I would just paint a few layers of epoxy on rails and leave it at that. You want them waterproof, but don’t need to strengthen them. Just brush a thick layer on the rails every time you do any epoxy work on the board. If you ding them too much, they might start taking on water, but you’ll probably want to build a new board by then anyways.
7.) just get a full deck pad, you’ll want the extra flotation with a wooden board anyways. Epoxy/salt is really nasty on skin if not done well. When drilling holes and filling with epoxy, you want the holes smaller than the washer you will use, can use large fender washer though. Also, epoxy tends to break down tape and leak out, so i like to drill through just to the layer of glass, but not through it, that way when you pour epoxy in it can’t leak out. Or just add extra tape and put something flat like a book under the holes.
9.) when re-drilling, make sure you don’t get off-center and drill wood. The epoxy is there for water proofing. Use stainless steel hardware, preferably 316 grade.
Extra notes- buy several cheap paint brushes, an epoxy squeegee and gloves. Epoxy is easiest to mix by weight with a kitchen scale, you need to be pretty close to the correct ratio for it to work right. Don’t try to mix tiny batches, as it is hard to get ratios right. Don’t try to mix huge batches because it will cure too fast and could start on fire. I would start with a 200 g batch of epoxy for one side, how much you’ll actually need depends on a lot of factors.
It is much better to build a silicone blanket for that, with a PID. Even than be careful.