Fibreglass help... Kayak

[chuckyNZ]

Okay so I have had a look around on this site but I am having trouble finding the info I need. Sorry if this has been asked 1000 times (which I probably will hear) but if so please point me in the right direction. I am new here and new to boat building so it maybe I am just searching in the wrong areas...

So... I am building a kayak (plywood stitch and glue) and I was wondering what the best method for fibreglassing? there are so many kinds of fibreglass sheets and epoxy resin that I don't know where to start. Also this was set as a challenge of building a boat to go around a local island for under $150 NZ which I should be able to do.

Thanks captain!

 

[rwatson]

The best method - is to roll the epoxy on, and squeegee it level with the first layer.

If its the best material you are after, just use epoxy and 200 gsm ( 6 oz) fiberglass cloth. A popular epoxy is West System ,but see if you have the perfectly good FGI R180 epoxy, which is significantly cheaper

never use Polyester resin

Its about standard for stitch and glue kayaks

eg.
http://schoolroad.weebly.com/kayaks---build-photos.html

 

[Black The Mac]

I agree with Watson.

 

[PAR]

Welcome to the forum.

The above is about correct, though the first coat on raw wood, shouldn't be allowed to "stand" on the surface, but should be scraped clean with the edge of a putty knife or plastic applicator. This prevents out gassing, which can only occur if epoxy is pooling on the surface. Once this is dry or past it's "green stage", subsequent epoxy coating can be done with a roller and squeegeed smooth.

Do yourself a big favor and download the free "User's guide" from westsystem.com and the "Epoxy Book" from systemthree.com. These will cover the materials, techniques, methods, etc. A simple sheathing is pretty easy to do, once armed with the information in these two free bits of goo instructions.

If you're looking for a natural wood finish under the 'glass, then you'll want 4 ounce (150 GSM) cloth or lighter. Cloth of this weight ( or lighter) will all but disappear when it's coated with goo.

Lastly, the plans should tell you what weight cloth to use. Most taped seam builds (stitch and glue) like yours, don't really need the cloth for structural reasons, but some do. My point is if your plans say you need a minimum of X ounces, you can usually go lighter. Light fabrics like these only offer abrasion resistance, not much strength, so if the plans say 8 ounces (270 GSM) and you want a bright finish, using 4 (150 GSM) will not threaten anything at all.

 

[rwatson]

Welcome to the forum.

The above is about correct, though the first coat on raw wood, shouldn't be allowed to "stand" on the surface, but should be scraped clean with the edge of a putty knife or plastic applicator. This prevents out gassing, which can only occur if epoxy is pooling on the surface. Once this is dry or past it's "green stage", subsequent epoxy coating can be done with a roller and squeegeed smooth..

Dont worry, outgassing can happen with just the minimum epoxy/glass layer, if the temperature is rising. It can even raise a centimeter or so of glass off the surface of the wood, and make a distinct 'ringworm' that needs treatment, and will show forever on a clear finish.

Ask me how I know !!!

The ideal technique is as Par describes, but if its not convenient to do the final 'dress' layer before the first layer is done, there is no major drama if you wash the first layer thoroughly with soap and water, then sand lightly.

West and others recommend foam brushes to finish off the final layer. I found them to be better than paint brushes, although specialist brushes can be bought for an impeccable finish.

 

[rasorinc]

Use No-Blush epoxy. No washing or scrapping.

 

[PAR]

I don't use brushes very much with epoxy, though there are some occasions they're the only thing that will fit into a corner. I prefer a squeegee or plastic applicator, which can apply a uniform layer of goo, with a little practice. Foam rollers do apply a uniform film thickness, assuming you don't try to "stretch" it out by over rolling. Going back and tipping off with a foam brush will break up bubbles and let the resin "self level".

I've found there's no such thing as a true "non-blush" epoxy (in the usual marine formulations), in the back yard builder's world. Unless you can really control environmental conditions, some level of surface contamination, be this blush, dust, dirt, or suicide minded bugs will be in the cured goo, so all freshly coated surfaces should be cleaned and toothed up, prior to subsequent coatings.

 

[rwatson]

......
I've found there's no such thing as a true "non-blush" epoxy (in the usual marine formulations), in the back yard builder's world. Unless you can really control environmental conditions, some level of surface contamination, be this blush, dust, dirt, or suicide minded bugs will be in the cured goo, so all freshly coated surfaces should be cleaned and toothed up, prior to subsequent coatings.

Absolutely !!! A good wash and 'toothing' is insurance if you cant do the final coat 'wet on wet', blush or no blush.

 

[PAR]

Agreed, unless you have climate controlled shop environments or are using a "micro environment", there's no such thing as an uncontaminated surface. Even peel ply, not in a bag, has some level of environmental exposure, though this can mitigate quite a bit of these issues, still not a guarantee. Again this is assuming the things usually found in a small shop or someone's driveway doing a repair.