Plywood boat finished time for glass but a few questions first?

Hey guys so I was recently given extra plywood from a construction project and I decided to build a boat with it. I don’t have many pictures but I will post a few. I am confident in its construction and strength but I wanted to fiberglass all the joints to keep her water tight (she is in no way water tight right now as I haven’t added the silicone II sealant yet) and add a little more strength. I know I should use epoxy resin but can I get away with polyester resin instead? The epoxy resin is just so expensive, I know it’s not as flexible but I am not sure I can get all the epoxy I need for fewer than 100 dollars which is about my remaining budget for the project.

I was thinking I could use this:

http://www.ebay.com/itm/MARINE-GRAD...356?pt=LH_DefaultDomain_0&hash=item35b8b44bf4

So I figured I would lay down one coat of epoxy and hardener then for the second coat add in the fiber glassing matt cloth with the epoxy resin and hardener, then sand down paint and done....am I on the right track here? I am still learning and this is my first time using fiberglass as well.

Can you guys help steer me in the right direction here?

Thanks
Wolfgang

 

There is a difference between designs in terms of total expenditure, usually due to the pedigree or sophistication of the build, that determines the cost of materials and labor.
A simple experimental design, especially a first boat, will last for years even if the materials were cheap and the design dirt-simple to build.
By all means avoid epoxy especially on a dry-sailed (trailered each time) boat. What has been done so far? What was used to glue or seal joints?
Seam-taping is probably the best solution for you. You could use polyester instead of epoxy and save maybe fifty bucks. The polyester will last for ten years if carefully done (IF YOU KEEP IT WELL PAINTED). At that point, would you care whether epoxy or polyester was used? Even then, the boat can likely be rebuilt and serve another ten years, given a day or two of work.

 

Hi WG. From the photos, I think you have a viable boat there. It appears to be quite a well thought out shape.

That marine grade epoxy should be ok, but I think that matt cloth will be overkill. It adds little in strength, and just weight. 6 oz cloth or higher is much more effective.

Purely in the interests of economy, I think you would get good results doing the following.

1) Use the epoxy, with a little bit of silica mixed in, to do a bead around the insides of all the joins ( and inside any gaps ). I would also lay a strip of 6" x 6oz cloth over that bead, wetted out with epoxy.

2) use the epoxy with say fine wood sandings, to fill in any gaps on the outside of the joins, and lay about a 6" strip of 6 oz cloth in epoxy around all the outside joints.

Normally, at this stage I would suggest a layer of 6oz cloth and epoxy all over the bottom of the boat, as it looks like you will be using an outboard on the boat, and this would add bottom strength for motoring, and a bit of grounding protection.

However, if you use whatever is left over of the epoxy to do as much of the hull bottom as you can ( starting from the keel ), you could probably get away with using cheaper polyester resin on the bottom and sides of the boat with the 6 oz cloth.

Once that is done, you could most likely get away with some good sealer paint and top paint to the inside of the boat, and it would give you satisfactory results.

The only warning about all this, is assuming that the plywood is quite good quality. If you noticed little gaps along the edges of the pieces you cut, or that the wood itself is quite soft and easy to splinter, then epoxy in glass over the entire boat would be a great idea to make sure that the boat doesn't fall apart from water ingress.

You should certainly keep this boat under cover when not in use.

 

Thanks for the help guys! I went to a local boat yard and copied all the angles and measurements from one of the Jon boats there, I also bought a set of plans and compared and compromised with all the measurements and angles to give me a boat that I could build given my skill level and needs. I used screws, wood glue on all the joints, and silicone II caulk sealant crammed into every where I could put it inside and out. The boat is "complete" construction wise I just need to make it seaworthy.

So polyester resin it is then with 6 .0z cloth at the joints inside and out (is this seam-taping?), then cover the inside and outside with 4 coats of exterior house pant. How does all that sound? Good plan? Also where should I go about purchasing all these materials?

The boat will be dry-sailed and i do plan to mount up to a 7hp motor on it.

 

If using polyester resin, don't use 6 ounce cloth as your tabbing. Use a stitch-mat product.

 

Yes, as Par says, Polyester is not wood friendly, and would need a better quality glass material.

I would STRONGLY recommend Epoxy on at least the seam taping - especially as you have already got a lot of gunge in the joins.

If you sheath the outside of the hull with Polyester - don't bother doing any Polyester on the inside. Sheathing the whole boat in Polyester will encourage moisture retention and rot the plywood.

 

Ummm, er... Does epoxy bond with Silicone II caulk?

 

make some fillets on the inside with PL glue or construction adhesive comes in a caulking tube.Do the same on the outside seams ,paint it call it done.Next boat don't put in any silicone and do as what has been said above.

 

No, not at all - but it will form a tighter, more waterproof seal on the wood around the edges of the silicon.

Polyester will lift off, and trap water under the wood around the edges.

Fillets of Construction Glue etc will be a complete waste of time, and just become a moisture trap. They also add no appreciable strength to the seams. They will also be impossible to sand fair on the outside.

Potentially, we are looking at very soft, void prone edges on this type of plywood.

 

Now I am all confused. At first I got the impression I should use poly resin because it is a dry-sail boat…. So silicone doesn’t stick to epoxy? (freakin great!) I am just going to stop working on it now till I get pointed in the right direction here… So am I back to the original plan of using epoxy along all the seams with some forum of cloth and that’s it?

This IS my first boat so lets pretend I don’t want to epoxy anything (not suggesting this just wanting to investigate all possible routes) how would I go about finish up the boat?

 

You have many options. You went ahead and used silicone and now you have to deal with that.
I suggested polyester resin based on your saying you had limited funds. It's not a bad option. Yes, it eventually lets go (I guessed ten years), but I figured you were building this boat on a strict budget with low tech methods.
Epoxy is great but probably you can't make a silk purse from a sow's ear especially if its your first ear.
Epoxy or polyester and tape will work but you have to grind off any silicone (except what is left flush at the joints.) You don't have to dig out any silicone that is in the cracks. The tape will bridge the joint if it's not more than 1/2" or so wide. A double layer of tape would be good, staggered 1/3 (ends up 3" wide).

 

You find that silicone isn't viewed very favorably in the industry, unless you're putting in some windows. It has no real strength and nothing stick to it.

You can use polyester, just knowing it doesn't stick to wood very well. I repair lots of production boats that have wooden parts covered in polyester, so I'm grateful the manufactures still use this technique. You can improve the quality of your build with more polyester then the typical factory uses in their boats, but it still has limitations.

Hack out as much of the silicone as you can, then fillet the bonded areas with thickened polyester, after fully saturating the areas with straight resin. Apply a few courses of mat and roving over the seams and joints, well tabbed out onto the hull shell and surrounding elements. This will give you the polyester price point, some level of structural bonding and you'll get some 'glassing experience too.

Will it be as good as a fully encapsulated, taped seam epoxy job? Nope, but so what, go have fun, learn what you will and fix the stuff that breaks, as you need to. This is what it's all about. Everyone here has had to learn the lessons you'll be learning, so enjoy, catch some big *** fish, drink some cold beer, in the hot sun and your next project will be a lot better off. My first boat had mild steel fasteners, polypropylene lines and house paint to finish it off, which looked like it was put on with a wire brush. I loved it, fished the crap out it and eventually built another boat, with the things I learned from the first. Welcome to the wonderful world of boat building. The point is to get out on the wet, so get on with it and let the things fall where they will. The boat will not explode the moment it hits the water, just because you used silicone and covered it in poly, so build in a big beer cooler (mandatory equipment) and go have some fun.

 

As Par says, the difference in budget between doing the seams in poly versus epoxy may not be as huge as you think after thickening, especially as you don't really need to glass the whole inside of the boat.

I would only apply matt glass very sparingly for huge gaps if you use epoxy, as matt and epoxy can be a bit difficult, especially for a new builder. You certainly dont want to introduce voids and gaps in the matt.

The extra longevity, strength and lower future maintenance of using epoxy will pay for itself many times over.

 

Agreed on epoxy use, but he apparently has the polyester (my assumption). He's also got the silicone and other issues, so lets just get him out there and he'll figure things out, just like the rest of us. The most important thing is getting her bottom wet, which is what I tell the other half all the time.

 

you screwed this together yes?so you have some strength already.if you want to go as cheap as you can then theres some things you can do.
no boat buliding pro here but i can make anything out of wood.

get some wood maybe hardwood of some sort something that will lay flat in the seam area on the inside.cut it to match the angle of your sides then glue this down,you could use whatever, silicone will work if you still have some.then screw this in from the outside predrill all your holes this wil hold the wood tightly until it dries.use the right length of screws.where the pieces intersect like at the front where you'll have 3 come together try your best to shape them to get a flush fit and glue it all up.this will give you a pretty good seal.will it leak ,ya maybe a little but thats what a bailing bucket is for.seal the outside holes from the screws with the same.

now you need to add some stiffness to the boat, corner blocks on the inside will do this.right at the top where the sides meet the end panals again glue and screw.if you plan on rowing then you'll need some gunnels maybe 1x 3/4 they go all around the outside again glue and screw.

paint it and call it done.like par says go enjoy it.

remember your life jacket and were it!!

again just some suggestions to finish it on the cheap.