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Old 26-09-2006, 22:52   #1
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Fibreglassing Secrets

I am having a bad day with some fibreglassing and wondered if anyone has done what I am doing.

The fibreglass under the halyard winch on the cabin top (under the dodger) flexes quite a bit when I wind up the main. There is a large inspection hatch under it in the cabin lining so I decided to do some strengthening under it (on the cabin ceiling so to speak).

I bought some International Resin and hardner and some cloth. Cut up four 400mm x 400mm squares and wet out the first one with the resin/hardner mix and brushed it onto the cabin ceiling under the winch. Then the second, third, and last.

........then I noticed it starting to sag. I tried brushing it back but it kept sagging.

I scraped off the lot and just put on one and went home!

It looks like the weight of the four was just too much.

Do you reckon I just do one patch a day? I thought the best thing to do was add each layer as the first started to go tacky. Does anyone know if there is a secret to this?

cheers
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Old 26-09-2006, 23:00   #2
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Aloha Seafox,

There is no secret. Fiberglass resin and cloth are heavy and will flop down unless you hold it in place and keep reattaching it (rolling it out) until it starts to kick. Whenever you are doing an overhead patch two or three layers are about maximum. Epoxy is harder to do overhead because there is no way to make it go off quicker. You just keep rolling it out until it hardens. Polyester is a bit easier for overhead because you can make a quick batch using a bit more catalyst.
Keep on experimenting with it until you get a feel for the right amount of hardener (catalyst) and the right amount of layers.
Kind Regards, JohnL
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Old 26-09-2006, 23:22   #3
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Aloha John
cheers for that. I will have another go tomorrow.
Still trying to get the resin out of my hair.
I have learnt that you should wear a hat!!
Darryl
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Old 27-09-2006, 01:13   #4
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Hi Darryl, Hey a good method of cleaning epoxy off you is to use White Vinegar. It is also great to wash brushes in before final cleaning in a solvent. It's stops the reaction and so brushes or what ever wil not harden.
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Old 27-09-2006, 05:14   #5
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I find that "Baby Wipes" work well for cleaning resins, epoxy and caulks off my hands. I keep a big container on the boat all the time..
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Old 27-09-2006, 09:37   #6
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if you need to hold a patch up while it hardens you can use a layer of waxed paper over a piece of plywood ... epoxy will not stick to it. to thicken the epoxy it is recommended to mix in west system 404 High-Density Filler. this will make the patch stronger too.
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Old 27-09-2006, 10:33   #7
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Epoxy is the Best Stuff

I disagree that epoxy is harder. It defiantly has better secondary bonding characteristics than polyester. The trick with epoxy is to roll on a coat then allow it to become sticky just prior to it hardening. Roll on your cloth dry, then roll on and wet out the cloth layer, do the same operation to all of the layers and you will have a very strong (chemically bonded) and unbreakable patch. I am reinforcing my hull deck joint using 5 layers of bi-ax cloth this very same way. I use a 30-35 minute gel hardener after it is batched I hit a 45-50 minute timer to notify me when it is time for the next layer. The type of cloth you use is a big factor in achieving good strength to your lamination
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Old 27-09-2006, 11:57   #8
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Overhead fiberglassing?

My thoughts on doing overhead fiberglassing is to use the vacuum bagging trick. Get yourself a kit, put the putty down around the area, layer the glass/matt/epoxy with the absorbant stuff, use regular polyethelene drop cloth with a valve in it, and hook the vacuum source to it with the epoxy trap.
Sounds easy, but I have yet to do it... can't wait to try it out. If I ever have to do my deck from the inside, will use that method.
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Old 27-09-2006, 16:23   #9
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I have been doing quite a lot of fibreglassing recently, and have picked up a few little tips.

If you are laying fibreglass in an area where gravity is not your friend (i.e. above your head), then mix small quantities of resin and use a little more MEKP (or whatever is your catalyst) than recommended, so that the resin goes off relatively quickly.

Do not try to lay more than 2 layers at a time... if you have plenty of time on your hands, do 1 layer at a time, and apply the 2nd layer just as the first layer is going "tacky" (i.e. starting to go off).

Also, I tend to use bi-directional woven rovings for strength, but alternate with a thin layer of chopped strand mat (this was recommended to me by a professional fibre-glasser), and I have never had any problems with adhesion or sag.

Finally, if you are laying multiple layers, make each layer slightly larger than the previous, so that each layer has at least some bond onto the original parent surface.

Oh, and those cheap paper suits are the business!

Good luck.
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Old 27-09-2006, 17:08   #10
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Sheela III

Hello everyone, Anyone out there that I know???? svsheela III, I sail east coast of Florida then on to the Abacos.
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Old 27-09-2006, 21:50   #11
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MEKP is for Poly/vinylester Resins ONLY. It is a catalyst and the amount you use can alter the gel times. But care is also needed. There is still a resonable exactness in ratio required
You MUST NOT mix in more than the correct amount of Epoxy hardener to Epoxy Resin ratio. Epoxies work very differently to ester resins.
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Old 28-09-2006, 02:34   #12
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All done. Wore a hat today and some longer gloves so none on me. I just put the patch on a peice of cardboard. Wet it with the resin using a brush and then brushed the patch onto the surface. Used a heat gun in between coats and all is ok.
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Old 28-09-2006, 15:26   #13
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Quote:
Originally Posted by Alan Wheeler
MEKP is for Poly/vinylester Resins ONLY. It is a catalyst and the amount you use can alter the gel times. But care is also needed. There is still a resonable exactness in ratio required...
Wheels,

I use 1% MEKP on a stinking hot day and 2% on a freezing cold day... everything else (faster go-off / slower go-off, etc.) falls within these boundaries. Does this seem about right to you?
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Old 28-09-2006, 21:52   #14
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Yep that sounds good.
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Old 29-09-2006, 07:15   #15
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Tip for using polyester. On each job...log the temp, humidity, amount of catalyst (I measure in CCs), amount of resin and how long it took to kick. Once you do this a few times it gives a benchmark chart for catalyst. It lets you dial in the work time.
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