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davidpm 04-09-2013 12:23 AM

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.

Stumble 04-09-2013 02:04 AM

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.

overbored 04-09-2013 02:27 AM

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.

davidpm 04-09-2013 01:32 PM

Re: How to glass
So basically just smush it in their and do the best you can.:)

Faster 04-09-2013 01:38 PM

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.

Barquito 04-09-2013 03:31 PM

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.

davidpm 04-09-2013 09:58 PM

Re: How to glass
1 Attachment(s)
Sorry here is the picture

SloopJonB 04-10-2013 02:03 AM

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.

chucklesR 04-10-2013 10:19 AM

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).

Stumble 04-10-2013 02:36 PM

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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