Fiberglass question

Hello everyone,

I am getting ready to fiberglass the exterior hull of my Shw 17 S&G but have a couple of questions.

In laying out the glass fabric, I found that my second layer is wide enough, but not long enough to cover the entire bottom panels.  Can I use two pieces of fiberglass for the second layer?  If I can use two pieces, should they overlap ?  Or should they meet end to end?

I know this is an important step for the strength and look of the finished product, so I want to get this right!  Thanks in advance for your help...I've learned lots from all you pros out there:)


4 replies:

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RE: Fiberglass question

I don't know what's specified for the SW17, but in general, it's good to overlap your glass at least 2 inches, if you can. Glass gets its strength from continuous fibers. Butting the pieces leaves a weak spot. overlapping them lets the threads in one piece bind to the threads in the other. It's not as strong as a single continuous piece, but good enough and very much better than butting them.



RE: Fiberglass question

Why are there two layers?  Did I miss something?  I would suspect one external layer and one internal layer would be more than sufficient.

As for overlapping, yes that's a good idea.  If you try to lay the two pieces out end to end, you'll have a stringy mess where the two pieces meet and will likely not have continuous coverage everywhere as a result.


RE: Fiberglass question

The Shearwater hull uses 3 layers of 4 oz external glass. The first covers the entire hull. The second covers the bottom panels slightly overlapping onto the sides. The third layer are strips that lay along the keel at the bow and stern running from near, or just above the waterline to about 4 or 5 feet back.

It's too bad that the 2nd layer is too short. You should be able to overlap at the cost of having another joint to feather and probably some slight visual artifact in the end depending on how carefully you work. I think the length of glass specified to do the Shearwater assumes that you will cut long diagonals across sections that run the length of the boat in order to minimize waste. I found that too difficult to do working by myself so just bought an extra 20 feet or so of glass.

The glass is pretty inexpensive, why not just order enough to cover it up in one go? Probably worth the time saved cleaning up and feathering an extra joint?


Ogata (eric)

RE: Fiberglass question

I went ahead and ordered the extra glass. I figured why make it difficult when the cost is fairly low. I finished glassing the hull and am pleased how it turned out. Have to do some sanding of a few stray threads but overall it looks good ! Thanks for the input.  

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