Twill vs chopped strand for first few layers after gelcoat


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lovethepirk
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I'm doing a wing mold from a carefully smoothed 3d printed plug and 3d printed flange. Although the geometry is not that complex, I am doing a test piece right now b/c I am a rookie.

The issue I am having with the test piece is I don't like how the 6.75oz / 228 gram chopped strand fiberglass is following the contour in the below picture. I have read somewhere where I can build up that area with extra gelcoat to make that area not as drastic.

I'm wondering if a better way to go would be to start off with twill fiberglass so I can get the contour perfectly without the risk of the chopped strand pulling from that tight curve or if I should stick with chopped strand.  I'm planning on making a rigid mold so I'm considering tossing in layers of twill and also maybe even leftover carbon fiber twill.  Any suggestions on building up that area with extra gelcoat or skipping or not skipping the chopped strand is helpful.  Thank you.



Warren (Staff)
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Typically you would use a glass surface tissue or fine/light weight CSM for the first layer or two against the gelcoat to help with conformity against the mould and also as a print through blocker before you use the thicker chopped strand mat. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Lester Populaire
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lovethepirk - 7/1/2019 6:16:22 AM
I'm doing a wing mold from a carefully smoothed 3d printed plug and 3d printed flange. Although the geometry is not that complex, I am doing a test piece right now b/c I am a rookie.

The issue I am having with the test piece is I don't like how the 6.75oz / 228 gram chopped strand fiberglass is following the contour in the below picture. I have read somewhere where I can build up that area with extra gelcoat to make that area not as drastic.

I'm wondering if a better way to go would be to start off with twill fiberglass so I can get the contour perfectly without the risk of the chopped strand pulling from that tight curve or if I should stick with chopped strand.  I'm planning on making a rigid mold so I'm considering tossing in layers of twill and also maybe even leftover carbon fiber twill.  Any suggestions on building up that area with extra gelcoat or skipping or not skipping the chopped strand is helpful.  Thank you.



I usually fill this kind of corners with resin and short glass fibers (a filler you can buy like this). You mix in as much fibers as needed to get a thick paste and then continue wet in wet with chopped strand mat. And as Warren said i would really suggest to start with a lighter matt or fabric as first layer after the gel coat to avoid print through.
lovethepirk
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Lester Populaire - 7/1/2019 5:16:16 PM
lovethepirk - 7/1/2019 6:16:22 AM
I'm doing a wing mold from a carefully smoothed 3d printed plug and 3d printed flange. Although the geometry is not that complex, I am doing a test piece right now b/c I am a rookie.

The issue I am having with the test piece is I don't like how the 6.75oz / 228 gram chopped strand fiberglass is following the contour in the below picture. I have read somewhere where I can build up that area with extra gelcoat to make that area not as drastic.

I'm wondering if a better way to go would be to start off with twill fiberglass so I can get the contour perfectly without the risk of the chopped strand pulling from that tight curve or if I should stick with chopped strand.  I'm planning on making a rigid mold so I'm considering tossing in layers of twill and also maybe even leftover carbon fiber twill.  Any suggestions on building up that area with extra gelcoat or skipping or not skipping the chopped strand is helpful.  Thank you.



I usually fill this kind of corners with resin and short glass fibers (a filler you can buy like this). You mix in as much fibers as needed to get a thick paste and then continue wet in wet with chopped strand mat. And as Warren said i would really suggest to start with a lighter matt or fabric as first layer after the gel coat to avoid print through.

Thanks...i will start with much thinner fabric.

What is. "print through"?  Is chopped strand used for it's cheaper cost, wet out ability, strength directions, etc?  Why not use twill only?  Thanks in advance.

Warren (Staff)
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Print through is when the pattern of the fabric shows on the surface of the mould.  CSM is mostly used for cost and ease of use on moulds. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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