despirately need fiberglass help

[scotttanner]

I need some help. I have done alot of reading, researching and watching videos. I am using west system epoxy.

I removed my windlass in preperation for a new one and have to patch the old hole.

I would like to know how to calculate the number of layers of fiberglass needed for the patch? My deck is wood core with 5/16" thick glass and gelcoat on top.Locally, I can buy 6 oz cloth and matt (not sure what weight matt). If anyone can elaborate the use of 1708 biaxial thickness/calculating layers would be useful.

(5" hole left from windless) I routed out the deck, down to he bottom skin about an 1" wider than the hole, to receive the wood patch and beveled the fiberglass at a 12:1. I cut the 6oz cloth into consecutive smaller circles, about 12 pcs total. I wet the hole and the wood plug with epoxy, then used a thickened epoxy and inserted the plug. Then, I wet each pc of pre-cut cloth and stacked them macking a patch (all 6oz cloth).

This is where the problems occured: I transfered the patch to the hole. The patch changed shape drastically while wetting, It wasn't oval now it was round. Once I laid the patch in the hole and started to squeegy, the edges of the cloth started pulling and fuzzing up (but wet). It was an awful looking patch so I pulled the wet glass out and trashed it. I left the wood plug in place and cleaned up the epoxy for another attempt.

I must have over worked the epoxy into the glass. It did wet very easy with a brush. I feel like I should layup a piece at a time, right in the hole instead of transferring all layers at once.

Any tips would be appreciated.

By the way I did order 1708 biaxial. It will not be in until next tuesday so if it is okay to use cloth, please let me know. I would like to get the patch done.

and .......the new windlass location will no be over the old hole but further aft

thanks

[marshmat]

Hi Scott,

The rule of thumb is to make the patch similar to what's already there, and feather it out into the existing laminate. What you've done so far sounds just about right, except for one thing: it's much easier to lay up the patch in place, than to try to wet it out on a bench and then glue it in place. The cut edges of fibreglass cloth will always make a mess if over-worked. You might use a sheet of wax paper or flexible plastic (saran wrap is a bit too thin, industrial poly sheeting a bit thick) overtop to help get a smooth surface as it cures and to keep junk out of the wet resin.

Just put some epoxy on the wood, work the first (smallest) disc of cloth into place, add a bit more epoxy, then the next layer of cloth, etc. until it's flush with the surrounding deck. You'll also want to glass up the side of the patch facing the interior of the boat, if you can get to it. Whatever fibreglass cloth you can get your hands on should work just fine, it's just a 5-inch hole after all. Chop-strand mat, I find, is just a pain in the backside most of the time, its only real advantage is that it's a cheap filler.

[PAR]

Try to avoid using wax paper, as the wax can come off while the epoxy heats up during the cure and contaminate the surface. Skip the mat, it's not necessary nor desirable with epoxy. The last layer of material on the outside should be light weight cloth, not biax. This finishes much easier. Fill the hole from the outside until it's just below being flush with the surface, so you'll have room to fill and fair it smooth without grinding 'glass fibers. It's also important that layers of fabric are applied on the inside as well.

[scotttanner]

thanks guys, as soon as the rain gets out of here i will try it again. This time i will try laying it up in place and will use poly to help protect.

I do have another question: if my gel coat is a little less than an 1/8" and i am going to paint the patch, should I fair so I am even with the top of the gelcoat or slightly lower? How thick can the fairing layer be? Do i have to fair while the patch is still tacky or wait until the next day once the epoxy is cured? Also, can I lay up the patch all at one time, 5/16"?

Thanks again for the help

[PAR]

Yes, when you're finished fairing it should be flush with the gel coat.

Fairing can be as thick as necessary to get it really smooth. Ideally you want to keep the amount of fairing thin, because it's not structural.

You pretty much have to let the fairing compound dry completely before you can sand on it.

Yes, you can layup the patch all at once and this is preferred, because it's stronger.