Boat building epoxy question?

[Tomos C]

Hi, I'm in the process of redoing the floor of my boat. I have somewhat of a dilemma, however. I laid the plywood, after I've epoxied the edges and bottom, and there are gaps. The edges where the wood meets the side of the boats have big gaps. I was thinking about filling it with fiberglass mat and just pouring epoxy over it to fill the space. I think its a bad idea however because epoxy is expensive.I've come up with another plan, however, and don't know if it will work. I was thinking about buying a can of bondo and filling the empty space at the edges with it. Then I can sand it smooth, and just apply the epoxied fiberglass over that. Will that work? I don't want the bondo to react or crack underneath, which would cause problems.If that can't be done, does anybody have a better way to do it? I know I can add stuff to the epoxy to thicken it, but don't really want to do that. Let me know, thanks a lot for your help!

[ricsudukai4604]

Well not wanting to put modifiers in epoxy misses the point - that is what it is designed to do. You thicken epoxy in order to glue and laminate in order to prevent voids. As long as you have a good mechanical bond between the hull and the floor, thickened epoxy is the best option. So sand well. Brush mixed straight epoxy on the surfaces, apply thickened mix (peanut butter consistency or a little thicker) and fair evenly while soft, before full cure brush straight mixed unthickened epoxy over your work for a glass finish. Done right you will have minimal sanding to do, and a structural join that won't fail. You could tape over the join if you really want ultimate belt and braces strength - but the above technique will break the timber before the epoxy I promise you.Glass with epoxy pored on it will not be as strong, might have voids and all sorts of issues - you need to use E-glass made for epoxy too. (I use vinylester cloth for better (sharper) corners and complex curves.)But this job is perfect for thickend epoxy - the supplier of the epoxy will have bags of the modifiers needed - one sort is for gluing, the other for filleting (west system 403 micro fibres and 406 colloidial silica for example)Wear all the safety gear - don't let epoxy touch your skin, it is bad for you in really life shortening ways - don't think it is not. If you become sensitised to it it will NOT be fun.Bondo or any bog won't work - it isn't structural, and that join is one of the most stressed parts of any hull.

[Mike T]

I agree with Ric. You can used use fumed silica (Cabosil) as a thickening agent. Prime the edges of the wood with a thin epoxy to soak into the wood. When tacky but not fully cured, mix the epoxy putty and fill in.MAS Epoxy has good tutorials on their website.

[clawless]

I also agree with RIC, however I have also used long strand bondo-glass, the green stuff made with polyester resin gel, its about $12 a quart, so depending on how much you need the savings may not be that much. It has held up very well, no cracks that I know of. The the gaps I filled were about a 1/2 - 3/4 inch, if you have more than that...some stitched bi-axial cloth over thick cabosil or milled fibers thickened epoxy will be amazingly strong. Good Luck!