Epoxy

General discussion on any topic which doesn't have a natural home on any of the other boards.
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RobbieB
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Re: Epoxy

Post by RobbieB » 02 Jul 2019, 23:05

B Sharp wrote:
02 Jul 2019, 18:59
Robbie, I used epoxy rather than polyester for the canopy mould for my BG135. I also used cloth rather than mat thinking I was being smart. BAD MOVE!
When heated during the pulling process the epoxy shrunk and left me with a pronounced weave pattern on the finished canopy. Barry at Sarik put me right!
Brian. :)
Brian, are you saying both the epoxy AND the cloth is a bad idea as I was intending to use cloth?

Once glassed (two layers) I do intend finishing with P38 or similar.

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B Sharp
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Re: Epoxy

Post by B Sharp » 03 Jul 2019, 08:22

Robbie, I used 3 layers of heavy weave cloth applied with laminating resin. The cloth was then rubbed back to as smooth as possible. A further coat of resin was applied and rubbed back. I suspect that if I had used mat I would have got the same result but with an imprint of the mat.
I have returned to using a blue foam core on 1/4 ply base, covered in parcel tape then fiberglass mat and polyester resin. After sanding with 60 grit it gets a coat of P38, sanded and polished to a finish.
Brian. :)

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Cliff Evans
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Re: Epoxy

Post by Cliff Evans » 03 Jul 2019, 08:41

P38 will react to the heat, how it reacts varies. Cracks, bubbles or just weakens and sticks to the plastic. I have wasted so much time and effort over the years. There is no easy answer.

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RobbieB
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Re: Epoxy

Post by RobbieB » 03 Jul 2019, 17:15

B Sharp wrote:
03 Jul 2019, 08:22
Robbie, I used 3 layers of heavy weave cloth applied with laminating resin. The cloth was then rubbed back to as smooth as possible. A further coat of resin was applied and rubbed back. I suspect that if I had used mat I would have got the same result but with an imprint of the mat.
I have returned to using a blue foam core on 1/4 ply base, covered in parcel tape then fiberglass mat and polyester resin. After sanding with 60 grit it gets a coat of P38, sanded and polished to a finish.
Brian. :)
Exactly as I've done in the past Brian (only two layers of matting used) and it has produced almost perfect results albeit on easy canopies to pull:

canopy_plug1.JPG

canopy.JPG
I was just trying to avoid using polyester and mat - not nice to handle but the heating/softening of epoxy does make sense - classic method to extract a metal component from an epoxy enclosure.

MDev
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Re: Epoxy

Post by MDev » 03 Jul 2019, 17:29

Use a marine epoxy white undercoat and add pigment to it at 6percent, polishing each successive layer with wet and dry with a higher grade each time. You’ll get a much better finish. Or easy sand particulates with pigment added.

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