Movement in fibreglass deck

[steviecops]

I've got a British built Wilson Flyer 17 ft fishing boat. It is a Tri-hull, or cathederal hull as we call them over here.<br /><br />The floor is fibre glass, and under that there is a layer of foam of about 4 inches thick, and then the hull itself.<br /><br />My question is, should there be any movement in the deck? I suspect not, but when I stand in certain place on the deck, I can feel the floor flexing. It only moves about half an inch.<br /><br />I was wondering if I could drill a few holes in these areas and squirt some expanding foam into them to fill the slight gap between the existing foam and the fibreglass deck.<br /><br />Any advice would be gratefully accepted.<br /><br />Thanks<br />Steve

 

[DJ]

Re: Movement in fibreglass deck

steviecops ,<br /><br />The real question is what is directly under the deck fiberglass? Wood? If so, it is probably rotten. Best to find that out first.<br /><br />A few very small exploratory holes (core samples)may be in order.

 

[steviecops]

Re: Movement in fibreglass deck

djohns19.<br />As far as I know, there is only foam directly under the deck fibreglass.<br /><br />I suspect that the foam has either suffered some shrinkage over time, or it has been compressed, as the area that moves is the exact spot where you have to stand to drive the boat, and has therefore been subjected to more weight/pressure than the rest of the deck.<br /><br />Does this make sense to you, and if so, will my idea of putting in more expanding foam work?<br />Thanks again<br />Steve

 

[Solittle]

Re: Movement in fibreglass deck

Steve - I suspect your boat is made like most. The floor consists of a layer of fiberglass over plywood and the better boats have a layer of glass under the ply creating a sandwich. A half inch play is not normal and indicates rot in this type of construction. Yes you could put foam under it but that won't stop the rot.

 

[DJ]

Re: Movement in fibreglass deck

steviecops,<br /><br />As mentioned, I believe a small hole is needed to really see what's under there.<br /><br />If it really is just f-glass, your expanding foam idea will work. Be careful with that stuff, it can get away on you.<br /><br />Fill your exploratory hole(s) with MarineTex.

 

[steviecops]

Re: Movement in fibreglass deck

O.K, thanks for the advice. I'll drill a hole at the weekend and see what it reveals. I'll keep you posted.<br /><br />Thinking about it, I could just phone the builder and ask!

 

[steviecops]

Re: Movement in fibreglass deck

I phoned the boat builder today, and the construction of my boat deck is as follows.<br /><br />Three quarter ply ribs every 2 feet from the transon forward, glassed in. Layer of three quarter ply fixed to the ribs. 2 layers of fibre glass matting layed onto the ply and 4 inches up the sides of the boat. One layer of gel coat. No foam. Air tanks under the deck.<br /><br />He said it sounds like the glass just de-laminated from the ply and advised me to drill some holes to make sure the ply is dry. If the ply is dry, he told me to pour some resin into the inspection holes so that it creeps and fills up the slight void. My idea of putting expanding foam into the holes was a bad one! He said doing that would just blow the rest of the floor! <br /><br />If the ply is wet/rotten in places, he advised just cutting out and replacing the bad bits. Good news for me ;o) I won't have to take up the whole floor, and I don't have any foam in the hull to worry about.<br /><br />I'll let you know how the inspection/repair goes.

 

[Solittle]

Re: Movement in fibreglass deck

A suggestion if I may - I would use Marine Tex instead of resin for the inspection holes.

 

[steviecops]

Re: Movement in fibreglass deck

Hey Solittle.<br /><br />What exactly is marine tex? I haven't seen it in any of the shops over here, but I'm sure that we must have an equivelent. Is it like a fibre glass putty? Or a sikaflex type mastic?<br /><br />Please can you give me a description of marine tex.<br /><br />Thanks.<br />Steve