I have been doing research for about a month now on rebuilding a 16' Mitchell style skiff. This boat needs a complete overhaul, I will be replacing the transom and cutting out all seats and adding front and rear decks. It will be powered by a 25 Johnson. I'm beginning to compile a list of materials and having trouble deciding what type cloth to use on certain parts. First, the transom. I plan to rebuild with a marine grade plywood, more than likely 2x 1/2" glued together. After gluing the core in place and then filling any gaps on the sides/bottom and filleting, do I need to glass over the fillets with tape or do I go straight to glassing the entire core in place? What weight and type of cloth do I need to use? Second, the stringers. I will also construct these from marine grade plywood, again 2x 1/2" glued together. To glass these in place what weight and type cloth should I use? Third, the decks/bulkheads/floor. These I will construct from 3/8" exterior grade plywood. I plan to coat everything with 2 coats of epoxy and then glue in place. After that I plan to glass over the top/exterior facing sides with 6oz plain weave cloth. Should I use something heavier here for more strength? This isn't my first time working with fiberglass/epoxy, but it is my first time selecting the materials. I've read through so many build and repair threads and there seem to be many ways to skin the cat. I just want to make sure I'm on the right track.
I hate wood, and here is my advice. Spend the extra 40$ and buy a sheet of 5lb divynal for the transom. 2x 3/4" and it will hold a 50. Mine is done the same way with 3 layers of 1708 and will hold a tohatsu 40 on running 25mph into a log. (Real world results not a wives tale.) thicken your resin with 3m micro balloons and use it for your filler and then just glass straight over it. Don't use plywood for the stringers. Plywood is not necessary and it is very heavy. 2" thick 2lb polyurethane foam with 3 layers of 1708 to glass them in is all you need. Check out the old aquasport 222. All it had was 2 foam stringers in it and it was one of the best hulls ever built. Decks, again I hate wood. Do not ever use exterior ply in a boat. Use 3/4 nida core or divynal with a layer of 1708 on each side and call it real. No rot, and way stronger. I'd put an extra layer or two of 1708 where I plan to mount my trolling motor pedastol seat. Also, don't glue anything in. Figure out exactly where your floor will sit on the stringers and wet out 2 layers of 1.5 oz mat on the bottom of the floor and two layers on the top of the stringer and then lay the deck on. Stack bricks or buckets of water or anything you can find that's heavy along the entire length. Glass the edges in with a Matt,1708,matt Why spend all that money on epoxy to protect the wood when for the same pice you can use polyester resin and divynal and core it just like hells bay does. Pm me your number and I'll go through how to bed the core fill it and glass it in if you choose that route.
Where are you finding nida core/divynal for the same price as plywood? From everything I've researched, epoxy/plywood is cheaper than a composite/polyester. It's not like the first time you launch a plywood core boat it's going to rot out. With the correct building techniques and maintenance it seems as though I can build a boat that lasts a really long time? I've seen a number of builds and also people recommending exterior grade ply for the decks/bulkheads/floors.
Yea, I'm just biased and very passionate about no wood. Divynal is 50-60$ a sheet for 48x32. Just my opinions above. Someone else will chime in later with advice on wood. Epoxy is 100$/ gal and polyester is 20$/ gal. Your going to use 5-10 gallons on this build
I will definitely look into it more, just from everything that I've looked at shows the composite core costing way more, plus most say that it will need more layers of glass meaning more resin than plywood. I haven't seen a build that used full composite core that was in depth. I'm having a hard time picturing how all the separate cores are joined to create decks/floors.
CW is telling you the way to make it last. I too use composites but also understand the usage of wood. Note...that price is for 1/3 of a sheet of divinycell. Under your premis - use all marine and lose the exterior. Then do as CW describes. If you are a novice you will spend 5 times more on composites than wood and save very little weight when done. Extra glass and excess resin will eat a hole in your wallet. Also if you use the honeycomb stuff and put a hatch in then you have a completely different problem on your hands.
I think for this project I want to stay with wood. I'm just unsure of the type of cloth/weight to use on each specific part. For the transom do I need to tape the edges before laying the 1708, or do I just go straight to laying 1708 over everything after filling/filleting? Will 6oz over the floor and decks be strong enough?
I have never done wood work, the idea with the core is that it increases the section modulous with little weight and you need the thicker glass on the outside for tensile and compressive loading. With wood, the wood its self can handle the tensile and compressive loads. I would assume that a thin layer of glass in the epoxy just helps prevent the epoxy from flaking off or cracking and allowing water in. I have never worked with wood, but am an engineer. these are just my thoughts. someone else may have more to offer on this route.
Look at the wood and glass schedules on a similar sized hull at bateau.com. Camber your deck lumber to avoid having to use overly thick plywood. The curved plywood is extremely rigid and allows no flex and minimal weight.
Yes. Cover everything with 15-17 oz. The use of cloth on the deck is not for strength, that is what the wood is for, it is for abrasion and impact resistance to protect the wood. It also prevents checking of the wood. Yes 6oz will be fine. Re-read CWs post, he tells you the steps.
