to much vacuum?


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Francis Soenen
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Next week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect...
I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply.
Is it common that they do a post-treatment after an infusion (sanding and varnishing)?



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Lester Populaire
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Francis Soenen - 1/26/2023 10:23:27 PM
Next week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect...
I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply.
Is it common that they do a post-treatment after an infusion (sanding and varnishing)?



To much vacuum is not really a thing for vacuum infusion (with epoxy). The better the vacuum, the less air in the bag, the less issues with porosity.
I'm fairly certain that the issue in the first picture is due to uneven resin flow between the two sides of the core. The best way to mitigate is to have resin passages throughout the core vertically, so the flow front can even out. You can drill holes through the core every inch or so. But honestly there is always a risk this will occur in some small section. The fool proof way is to infuse the outer skin first, then bond the core in place, then infuse the inner skin. But this comes with a lot of waste in consumables and resin.

The second picture clearly shows bridging. make sure the peel ply (each individual layer really) is firmly pressed against the tooling. Depending on the geometry it helps a lot to have a cut in the fabric and overlap two patches.

And regards of post treatment i would always recommend a 2k clear coat for UV and moisture protection.

I have quite a bit of experience with flax infusions, so if you're unsure you can also hit me up with a private message.

Good luck

Francis Soenen
F
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Lester Populaire - 1/27/2023 4:45:20 PM
Francis Soenen - 1/26/2023 10:23:27 PM
Next week we try to infuse a canoe in flax fabric, a big challenge for me because it's my biggest project for so far. I made a few test panels to figure out the lay-up composition, but it was not completely perfect...
I had a few places where the surface was bad, but I have no idea what's the reason. I've worked with MTI hose and clamped off the resin tube when the epoxy reached the MTI. I infused at 13 mbar, so is it possible that the vacuum was to much? I did the infusion very slow, so I don't know what I best can change during the next test? The second picture is the backside where I've put some Corecel ribs, but here I think it was bridging from the peelply.
Is it common that they do a post-treatment after an infusion (sanding and varnishing)?



To much vacuum is not really a thing for vacuum infusion (with epoxy). The better the vacuum, the less air in the bag, the less issues with porosity.
I'm fairly certain that the issue in the first picture is due to uneven resin flow between the two sides of the core. The best way to mitigate is to have resin passages throughout the core vertically, so the flow front can even out. You can drill holes through the core every inch or so. But honestly there is always a risk this will occur in some small section. The fool proof way is to infuse the outer skin first, then bond the core in place, then infuse the inner skin. But this comes with a lot of waste in consumables and resin.

The second picture clearly shows bridging. make sure the peel ply (each individual layer really) is firmly pressed against the tooling. Depending on the geometry it helps a lot to have a cut in the fabric and overlap two patches.

And regards of post treatment i would always recommend a 2k clear coat for UV and moisture protection.

I have quite a bit of experience with flax infusions, so if you're unsure you can also hit me up with a private message.

Good luck

Thanks! I've send you  a private message with more details of the project.

GO

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