Fleece/cotton fiberglass boat

I know its not the best way, but i'm curious if anyone has tried it, the old car audio way. Make your frame as solid as possible, stretch absorbent and stretching fabric over the frame(usually fleece or t-shirt material) resin the "skin" then glass over your now hardened shell?

any reason why this wouldn't work?

what would be the major downfall to this method?

 

I suppose you could make a boat out of anything but the reason we don't use cotton is because it hasn't proven to be as light and stiff and water resistant as such things as fiberglass or kevlar or dynel.
The method has I'm sure been tried with materials that are better suited. My guess is that using a female mold is more efficient and maybe more reliable. The stretching idea might have merit though. Probably not using cotton, but using some other more appropriate cloth that would stay stretched tight even when wetted out.

 

I can think of several considerations that might cause issues, with a rigid, relatively low modulus skin.

Puncture resistance will rear it's head up, pretty quickly, which is why we tend towards tougher, lighter fabrics, such as polyester, nylon, kevlar, spectra, etc.

 

I wasn't suggesting the only later be the fabric layer, its just meant to be a shell to fiberglass over as opposed to plywood which is not as easy to make bends on multiple axis

 

It is going to dish to some degree with the weight of the lay-up placed upon it, and pass this on to the finished product, unless you have very closely spaced underlying frames. You also have something that will be as floppy as all hell when lifted off your "mould".

 

Why would you remove in from the frame?

 

I see, the resin soaked canvas, or whatever you intend using stays, as does the framing it is tacked to. Sounds like a real atrocity !

 

worked pretty decent for these guys, i don't have pics at the moment but my door panels are 5mm back plate with baffle on 1/2 dowl rods, stretched T-shirt material and 2 layers of cloth, they get kicked everytime someone gets out of the car(ok not the greatest design) finished them 3 years ago and still solid as a rock

 

Many years ago (back in the 60's I think) there was a GRP runabout boat kit that used a similar technique. The kit shipped as pre-cut cardboard formers that slotted together to form a criss-cross 3D structure. A stretchy knitted fabric "sock", that was supplied pre-sewn to shape, was then stretched over the form to give a hull shape and this was then brushed with resin and allowed to cure. Once the skin was hard, the hull was laid up using chopped strand mat and resin as normal, then filled and faired before being painted.

It wasn't the lightest thing around, and there was a lot of work in fairing the hull to get a good finish, but that was offset to some extent by not needing a mould and the very quick way the cardboard form went together. Somewhere on the web there are some photos of this kit, but I can't find it from a quick search.

 

But, needless to say, the cardboard and sock were discarded ? Not what our correspondent here envisages.

 

No, the sock ended up bonded to the GRP skin, it was just the cardboard that was ripped out and thrown away, IIRC. The idea was to produce a flat-pack boat kit that could be shipped easily, I think.

From what I can recall, the knitted sock was fairly thick, so must have absorbed a lot of resin. Not good for weight, but the boat so constructed was intended as a fun outboard runabout, so weight wasn't a big issue.

 

What would the sock have been made of do you think ?

 

I don't know for sure, but always assumed it was a bit like the knitted cotton sold in some auto stores on rolls for polishing - pretty stretchy. I recall seeing photos, and maybe even a video of an old film, of one of these boats being built some time ago, but try as I might I can't seem to find it on the web now.

 

I found the old film, see here: http://www.britishpathe.com/video/stills/do-it-yourself-boat

 

Good job Jeremy, I'd say the OP will be agog. Like doped aeroplane skin I suppose, the fabrics would need to not sag whilst being wet-out, and not let the resin run through it.