Last year I built a cedar strip canoe and had fiberglassed and epoxy'd the outside. DO NOT use regular hardware store epoxy. It is brittle and will crack with the flex of the boat. Theres different marine type epoxies out there such as the popular west system. I personally used a 3 gallon kit of Aeromarine epoxy and its been working great for less money.

As far as titebonding the plywood, I don't see why that wouldnt work. As long as the glue isn't going to be in direct contact with water, titebond 3 (the waterproof one) should be sufficient. You could also probably use the epoxy in its place.

I think the boat will be strong enough with the ribs and 1/4" ply. Just make sure the ribs run across the entire hull and not just along the bottom. Also, use a stronger joint on the ribs other than a butt joint.

I'm no pro boat builder but just sharing my experiences. I was also under the assumption that the gunwale is a huge strengthening force on boats. You may want to think of adding a hardwood edge for support.

 

I am getting my resin from US Composites i just emailed them and they said that epoxy resin has no uv resistance so you have to put polyurethane or varnish over the epoxy. They also said epoxy can be softend in the sun. They suggested for me to use poyester resin but i am adding black pigment. I have orderd a few thing from us composites and they seem to be very knoledgeable and have very good prices.


I think for the ribs im thinking mabe 1 1/2"- 2" wide by 3/4" thick, might cut notches in the sides for the ribs.

 

I wouldn't worry about the epoxy softening in the sun. It will soften a bit, but not enough to cause problems unless you have it baking close to 200 degrees. It will definitely last longer if you put a Spar Varnish (UV protectant) on as your final finish, though. I have a kayak I built about 9 years ago that I never bothered putting the spar varnish on and you can tell. I'm still trying to re-build a strip deck for it and hopefully she'll hit the water this summer. I'll be putting UV protectant on this time though.

 

I would use west systems epoxy, and instead of TB use the epoxy for the bottom too.

 

If you use the poly resin, let me know how it works out! And, yes, you/they're right about the lack of UV resistance on epoxy. I did put a couple coats of Helsman (sp?) Minwax polyurethane over the epoxy for UV protection.

I think we'll all agree here that you need to add more pictures!

 

I have used polyester resin in the past to make "acrylic pen blanks" it seems like pretty impresssive stuff. Ill let you know how it works on the boat. I pretty much just wingd this whole project. My goal was to build the boat the same weight or lighter than my smaller aluminum one. I wanted low cost too. The long side boards are each 2 pieces with a big old lap joint holding them togeather. They are 5/8 thick, i think i could have gone a fraction thinner. The sides ha a 30 degree taper to them. I used a 30 degree router bit for the flat part but there it tapers in the front i had to use a hand plane to get the proper taper so the plywood would lay flat. The cuts in the corner of the seat supports are so the water will drain back to the plug and not get stuck under the seats roting things. The back plate for the motor is 1 1/2" thick as of now and screwd to the sides. the back seat is on hinges to store stuff in it. All the seat supports ar 5/8 thick. they are just glued and nailed to the sides. I think with being glued and nailed to the sides and bottom it should be strong enough.
I only plan on using an electric trolling motor and mabe a small 4ph outboard.

In the first picture the seat supports look higher than the sides but they are actuall flush.

 

a few more pics

 

Im interested in this one. I'll be watching.

 

I think the grass bottom boat is a great idea:laughing: I think you'll be ok with using a 1/4" bottom as long as you put some cross rails to support it. For the cross rails I would use 1 1/2"x 1 1/2" yellow pine. What I don't like is the white latex paint. You would be better fiberglassing over raw wood. Titebond 3 would be much better than liquid nails if the parts fit well. If you have some parts that don't fit real good I would use gorilla glue. If you have access to a staple gun, staples will hold better than brads.

 

Here is an idea to attach the bottom from a skiff I built in 2004. It is called stitch and glue.

The ideas is to drill holes every 4" and 3/8 from the edge along the seams and use an electrical tie to stitch it together. After stitching you form a gusset with epoxy and wood flour using a plastic putty knife cut to the shape you want. You use this round form to shape the gusset. This gusset also makes it water tight.

By the way the sides are 1/4" and the bottom is 3/8" marine ply.

I do not want to steal your post but if you want I can post more pic's, or PM me and I can give you more details.

 

Not sure how well it would float with the grass bottom lol. The latex paint is only on the inside. I was only planning on fiberglassing the outside and maybe the bottom inside. I thought acrylic latex would hold up to water well? Would it be a good idea to put a polyester resin coating over the paint or would it not stick well? Im hoping i can get away with less support than 1 1/2" 1 1/2 because ill probably end up tripping on them lol. guess ill just see how it feels when i put the bottom on.

 

I think the inside should be fiberglassed especially being made of plywood. If you deside to fiberglass the inside I would sand as much of the latex off as possible. If you are just going to paint the inside you would be better off using an oil based enamel. Latex paint is porous and water will pass through the paint rotting and delaminating the plywood. As far as the supports, if you don't make the floor ridgid enough the flexing will cause the fiberglass to crack and fail especially on the joints. I know it would make it heaver but without the cross members you might consider using 1/2" plywood for the bottom.

 

Bob that thing looks very light! I would be interested in more pictures if you have some. Guess i should have held off on the paint and did the epoxy first.

 

bob that thing looks very light! I would be interested in more pictures if you have some. Guess i should have held off on the paint and did the epoxy first.

I epoxied the bottom and sides as well as extra strips on all of the edges for strength. The floor boards are plastic trellis from HD. I bought one length and made templates to cut the trellis. I Velcro’d them in so they can be removed for cleaning. The entire boat weighs 100 lb’s. The bottom and sides were covered in two coats of epoxy, one with cloth, sanded and than a final coat. Everything was sanded and then painted with marine paint. The paint was applied with a 1/8 closed cell roller than brushed over with a closed cell foam brush, just do areas of 2ft square at a time. This give a near spray on finish.

If you notice some of the clamps are sch 40 PVC cut to 1 1/2" lengths. You can acheive more pressure if they are cut longer. Cheaper than clamps.

The seats are covered with none skid strips to protect the paint and keep from slipping.

The wire ties are cut off just before epozying the outside. The seats were fastened using the same technique.

 

You can use house paint over West Systems epoxy (after sanding -removing the blush). That will improve the UV resistance.

 

Could i just cover the paint with a uv resistant polyurethane? Also im not sure how i would fiberglass both sides of the plywood because i would have to do the inside then put it on wile its still wet. If i did it wile it was atatched to the boat i would not be able to get the spots under the seat.

 

Could i just cover the paint with a uv resistant polyurethane? Also im not sure how i would fiberglass both sides of the plywood because i would have to do the inside then put it on wile its still wet. If i did it wile it was atatched to the boat i would not be able to get the spots under the seat.

You really shouldn't put a polyurethane coating or oil based enamel directly over latex paint. An oil based coating is likely to crack putting it directly over latex. From where you are I would sand it to where the paint was at least thin and prime it with an oil based primer for wood and then topcoat with an oil based enamel.

You don't have to fiberglass the entire boat at one time. You can do as much or as little as you want and get applied before it sets up. The stuff works like paint. You brush on a layer of epoxy or fiberglass resin and then lay the cloth in it and then work some more coating over it to where there is no air in it. Then you let it dry and move over to the next spot and do it again. I normally sand it a little where I overlap it. On the corners where the joint is I would use three layers of cloth to re-enforce the joint. When you get all of it on if you are using fiberglass resin I would go over it with fiberglass filler and fill and level everything and then put another coat of resin over everything. Then I would do a final sand and paint it.

 

Thats one fine looking boat. I will be doing the same thing in the corners as you , extra cloth to strenghtne the joints. I will have pretty much the same colors scheme as you. black outside white inside. I think for the black outside im just going to add pigment to my resin on the 2nd and 3rd coat. I forgot to mention that i will have runner stips on the outside bottom running long ways (like on a all jon boats)for stearing purposes. This should also help tie in the rails and make things more solid. They are going to be about an inch thick and 2 1/2" at the wides part.

Yes in the pictures that is about 5 pounds of jb weld smeared everywhere to fix holes lol

 

Bob, just curious how much resin you used.

I put the bottom on today with glue and brad nails, lots of brad nails. I did not have a staple gun. The bottom actually feels alot more stable than i though it would even withouth the cross rails. I think what im going to do as far as the finish on this inside is, sand all the structual areas fiberglass them then paint over it. Then i will fiberglass all the outside and paint it if the pigment dosnt work well. I really dont care that much about how it looks. I know the latex paint isnt the best but i think im going to stick with it because it would take alot of work to get it all off. If the bottom is still not as strong as i would like i will probably sand off the paint aand fiberglass the bottom inside.

 

Bob, just curious how much resin you used.

I put the bottom on today with glue and brad nails, lots of brad nails. I did not have a staple gun. The bottom actually feels alot more stable than i though it would even withouth the cross rails. I think what im going to do as far as the finish on this inside is, sand all the structual areas fiberglass them then paint over it. Then i will fiberglass all the outside and paint it if the pigment dosnt work well. I really dont care that much about how it looks. I know the latex paint isnt the best but i think im going to stick with it because it would take alot of work to get it all off. If the bottom is still not as strong as i would like i will probably sand off the paint aand fiberglass the bottom inside.

I think I used about a 1 1/2 gallons.

 

frankp My boat will get quite hot in the summer as the bottom will be black and it will be kept outside. But i dont think it will get to 200 degrees.
I already orderd the polyester resin and cloth. I tried fiberglassing a few seams and boy does working with this stuff suck.

Bob how wide were the sprips you used in the corners and along joint?

 

Well I've built over a dozen boats and went though a ton of epoxy so I think I'm moderately qualified to offer my opinion.

Personally I think 1/4" is too thin for the bottom, I'd use at least 3/8. I've used 1/4 for the sides on several boats and the bottom on a few canoes, but on my flat bottom skiffs the bottoms have all been 3/8 plus a layer of 12oz biaxial fabric with epoxy resin.

I know you already ordered it, but I'd recommend you stay away from polyester resin, I know some people use it and like it, but it's not much cheaper and it has nowhere near the bond strength or tensile of epoxy.

I'll not get into a super long reply here, but I'm a regular at http://forums.bateau2.com/ as well as http://forum.woodenboat.com/ and a few others. Building boats is my side job / hobby and I currently have over 70 plans in my possession (it's an addiction). If you have any questions I'm more than happy to help out so feel free to send me a PM. If you want to learn more about boat building jump on over to one of the forums I linked, study some of the thousands of build threads, maybe even buy a set of plans if you want a solid, proven design from an actual naval engineer and lastly have fun with the build!!

That's my $0.02 on the subject

 

Well I've built over a dozen boats and went though a ton of epoxy so I think I'm moderately qualified to offer my opinion.

Personally I think 1/4" is too thin for the bottom, I'd use at least 3/8. I've used 1/4 for the sides on several boats and the bottom on a few canoes, but on my flat bottom skiffs the bottoms have all been 3/8 plus a layer of 12oz biaxial fabric with epoxy resin.

I know you already ordered it, but I'd recommend you stay away from polyester resin, I know some people use it and like it, but it's not much cheaper and it has nowhere near the bond strength or tensile of epoxy.

I'll not get into a super long reply here, but I'm a regular at http://forums.bateau2.com/ as well as http://forum.woodenboat.com/ and a few others. Building boats is my side job / hobby and I currently have over 70 plans in my possession (it's an addiction). If you have any questions I'm more than happy to help out so feel free to send me a PM. If you want to learn more about boat building jump on over to one of the forums I linked, study some of the thousands of build threads, maybe even buy a set of plans if you want a solid, proven design from an actual naval engineer and lastly have fun with the build!!

That's my $0.02 on the subject

1/4 inch is what all the wood stitch and glue boats are made of and there are thousands of them in the water without any troubles. They run the gamut from kayaks and canoes to racing boats. It's more than sufficient strength-wise especially with glass on the surface.

I'll agree entirely on the polyester resin, though. Great for surfboards, not so great for boats, in my opinion.

 

Here's an example of why I avoid polyester of wood boats. It bonds to itself pretty good, but it does not form as strong a bond with wood and given time it will delaminate. A picture is worth a thousand words so...

 

No sir, 1/4 is NOT what "all the stitch and glue boats are made of" I'm very familiar with S&G boats and I've built 6 S&G boats myself. The only ones that used 1/4" for the bottom were the two canoes. What S&G plans are you using, I have plans in my file from over a dozen different designers and on anything larger than a canoe they all call for thicker material on the bottoms to deal with the load stresses, especially on planing hull boats.

The designers I have plans from are Mertens, Gatehouse, Spira, Haskins, Witt and a few others I don't remember off hand.

I'm really really not trying to be a jerk about it, but boat building is something I spend several hours a day either doing, studying or assisting others with. Even my little 14ft bateau.com "FL14" displacement hull skiff uses 3/8" ply on the bottom and it has nowhere near the loads of a planing hull boat.

This is the FL14 I built a few years ago. It's a S&G displacement hull 1/4" sides and 3/8 bottom.

 

I stand corrected, sir. I have used 4mm on the kayaks I've built and that or 6mm is what CLC and several other manufacturers use on their other boats as well. Those are mostly canoes/kayaks and skiffs or sailboats. I was not aware of several of the manufacturers you list, who seem to be geared more toward larger boats, which isn't where my experience is.

The point being, that a 14 foot john boat of that size should be perfectly fine with a 4mm (.157 inches) or 6mm (.236 inches) S&G hull, if properly glassed and reinforced. (I'm thinking the longitudinal "Rub rails" along the hull would be plenty of reinforcement.) That said, a 3/8" will definitely be stronger and give a bit more "peace of mind".

 

Thanks for all the help guys im really wishing i would have started this topic before i started. I did some more research on polyester resin after what gstanfield said and like he said epoxy would be better for my application. Im going to just go with what i have because it would be quite expensive to ship 20 pounds worth of resin back and order 20 more of epoxy. Hopefully i can get a decent bond to the plywood. If it starts to peel after a few years i will try to get it all off and do it the propper way. If i could do it all over i would most likely use 1/4 for the sides instead of 5/8 pine. I would also use 3/8 for the bottom. Resin and fiberglass will be here tomorrow. I will post some pictures of the progress.

 

Poly will work and there have been thousands of boats built with it, it's just not the best option. Consider this one a learning experience, have fun doing it and have fun catching some fish. If it lasts 10 years great, if it lasts 5 then so be it!

The one and only reason to build and use boats is for the fun of it so don't ruin the fun by stressing. Learn from this one and make the next one even better. I will give you one serious word of caution; boat building is highly addictive!! I bet that by the time you finish the first one you are already planning out the next build in your head

 

Im having a great time building this one. Sure its not going to be perfect and i did learn quite a bit. Total build costs will be under $300 and if it floats and works for a couple years i will be plenty happy. Im sure i will be building more in the future.

 

Frank, please don't think I was trying to be argumentative or negative. I know some larger boats that use 1/4" bottoms, but they are usually sailboats and rowboats (and a few odd Phil Bolger creations) If he's using this boat with oars or an electric motor 1/4 would probably be just fine. The severely increased bottom loads created when planing is where my concern comes in and most people with jon boats that I know want to put a 10-15hp outboard on it and plane. A pair of decent size skegs running full length on the bottom would make dramatic improvements, although I'd personally recommend those even with 3/8

IF you want a great set of plans for a S&G jonboat the best I have found are from bateau.com. Their GF12/14/16 series of boats are good looking and super strong, plus they are fairly large for their size. Here's one that a friend of mine built:

BTW, CLC has some great designs for small craft and yes they love to use the super lightweight stuff. Then again for really light I enjoy SOF designs suck as those from kudzucraft.com or gentrycustomboats.com