carbon wet-out consistancy issues.


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jono
jono
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hi all, i'm having issues with the final part not wetting out enough consistently. I am using the same mould, same layers, same resin and temperature conditions. absolutely no leaks in the bag and obviously the same vac pump. it visually appears to infuse at the same rate every time but only 1/3rd of the time it's actually fully wetting out the weave. it seems to be luck of the draw for me? i'm using a low viscosity resin, pulling a vacuum for at least 40 mins before infusing. i've tried clamping off the vac line and resin line like the easy composites tutorial, i've also tried allowing the resin to almost empty the pottle and only clamping the resin line and allowing excess to reach the catchpot and letting it cure wit vaccuum pump going. also moving around the resin feed/vac lines. i honestly have no idea what the cause is. would appreciate any help here.

this is what my parts come out like 2/3 of the time.




yet sometimes my parts come out perfect like this (same exact mould)-ignore the traces of clay on it-




any idea what could be doing this? i'm doing a fully dry layup, no glue or gel coat (its a brake duct) should i perhaps consider brushing/spraying a fine layer of resin down and allowing it to almost fully cure to a late stage of tack and then layup/infuse? 
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ChrisR
ChrisR
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Before you read the below, understand this is not supposed to offend (therefore please do not) but this is from MY experience with infusion:

I infuse at FULL vacuum, the volatiles boil off thing (from my experience) is complete <insert expletive here> and does not apply to epoxy anyway. 

Yes, if you put a pot of poly resin in a vac chamber and pull a vacuum then yes they can/will boil off as the boiling point is lowered and the thing won't cure. I've used polyester infusion resins quite a few times with success every time, the only instance I've had with something looking like "boiling off" has been when the mesh has pierced the bag and it's letting air in.

Control the flow front with the type of mesh, barriers/dams/inlet/outlet positions and cutting off the flow by clamping - some (many) will probably disagree with me on this following point but hey... By controlling the flow using the above there is absolutely no reason I have come across to infuse at anything other than full vacuum (or as close as you can get).

Pull the vacuum for (depending on size and layup of course) at least 30mins, do a drop test, only infuse when you know for sure the bag is sealed.

Control the temperature of the resin, mould and fabric, just a few degrees change with some resins can change their viscosity considerably.
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