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post #1 of 18 Old 04-09-2013 Thread Starter
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How to glass

This picture is of a piece of construction plywood made into the top piece of the centerboard trunk that also is a support for the mast of a dinghy.
It is for my rainbow dinghy if you remember my prior post.

I have some fiberglass cloth and some epoxy so I figure I might as well cover it.
Covering a flat surface with cloth is easy enough.

This piece has so many corners and curves, any tips on how to cover it smoothly to cut down on the sanding.

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post #2 of 18 Old 04-09-2013
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Re: How to glass

Coating with epoxy may be a good idea, but I am not sure why you would need to coat an internal part with fiberglass, so long as the boat was designed without it.

If you do want to coat it, the lighter the glass the easier it will conform to complicated curves. So instead of a heavier glass try switching to 3oz or so. If its really weirdly shapped you can go down even further. The lighter the glass the easier it conforms, but the more layers it takes.

If you want to do the best job possible, after all the glass is layer up wet, encase the part in a vaccume bag, and pull down a reasonable vaccume. This will help apply preassure evenly across the part, and press the glass into complicated curves.

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post #3 of 18 Old 04-09-2013
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Re: How to glass

the weight of the cloth has less to do with the way it will conform to compound curves then the type of weave, looseness of weave and size of the tow. the standard boat cloth with it's plain weave is the worst. the cloth with the smaller tow numbers will form to a smaller radius. using a loose 4x4 twill or 4 harness satin weave works much easier. also orientate the cloth so the weave is at 45 degrees to the curved surface and it will lay around the curve easily. one of the best cloths for compound curves is #7725. it is a modified 2x2 twill with a very loose weave about 8 oz.

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post #4 of 18 Old 04-09-2013 Thread Starter
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Re: How to glass

So basically just smush it in their and do the best you can.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #5 of 18 Old 04-09-2013
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Re: How to glass

No picture that I can see....?? Be sure to radius the corners well (1/2" or more) or the cloth likely won't lay down all the way around.
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Re: How to glass

There are also plastic sheets you can put over new glass to smooth the surface, and reduce sanding (after removing plastic). Might not work on sharp corners.

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Re: How to glass

Sorry here is the picture
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2013-04-08 22.04.34.jpg  

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #8 of 18 Old 04-10-2013
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Re: How to glass

I wouldn't even try to cover that in glass - you'll never get any fabric to conform. Cover it with epoxy resin instead. If ease of sanding it is a concern, thicken the resin with talc or microballoons. Don't thicken it too much - you want it to be runny enough to still have some flow so it will self level.

Ease all the edges (corners) first or the resin will be too thin on them. Don't sand the edges after coating, just scuff them with Scotchbrite.
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post #9 of 18 Old 04-10-2013
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Re: How to glass

I agree with JonB, no glass needed - unless it's for toughening up the surface.

Additives to the epoxy can do that as just as well (graphite strengthens, thickens, and makes smoother/slippery).

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post #10 of 18 Old 04-10-2013
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Re: How to glass

Agreed. Unless this part needs abrasion resistance I would cover it with three coats of neat epoxy to seal it, then paint it for UV protection.

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