precaution when trimming your part ?

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precaution when trimming your part ?

Author	Message
wozza	wozza posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 688, Visits: 5.4K	Jess8bit (16/06/2013) Thank you Warren for your suppor In this case I assure you it is not a bridging problem, the picture may mislead you. I try another one : The resin follows the carbon an d the mould perfectly (I use a spray gly to stick the cloth to the mold), and there is no bridging once demolded. It occured while sanding the border of the part, after having done a rough trimming with the Dremel. The Gel Coat peels off, under mechanical action, I'd say. Why so fragile ? Bad bonding between GC and the resin ? How much and what type of spray tack did you use? Also how long after the GC50 was laid down did you do the infusion? Carbon Copies Ltd
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	I use 3M super spray 77. Not perfect I know... It's the only one I can find (SprayZ still missing) I leave up to 24hrs (left it cure during the night) so it's not tacky anymore, following the guidelines from the EC (Matt) car bonnet video tut.
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wozza	wozza posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 688, Visits: 5.4K	Ok 24 hours for the GC50 is ok but no longer Ditch (stop using ) the spray tack. It is very easy to get a thick layer of it on edges and corners etc. When not using GC50 this is not really an issue as it will just effect the surface finish of the part which can be polished out but when using GC50 the spray tack forms a layer between the GC50 and the resin preventing a good bond between the two. Try the method I suggested before if you need to stick the carbon down Warren Carbon Copies Ltd
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	mmmm you're right, although I'm really carefull with applying a very light spray (knowing it might cause bonding issues since it is not a epoxy compatible spray), that could still explain the lack of bonding here or there, especially in the croner, where I spray a bit more to ensure cloth sticking. I guess I'll have to re-schedule my work so that I lay down the carbon while GC is still tacky (it was handy to let the night passes ^^). If only I could find a genuine tackifier... anyway, thank you Warren, for all
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wozza	wozza posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 688, Visits: 5.4K	Unless the part is really complicated with lots of recesses and steep sides etc you should not really need to stick the first layer down. Just pull vac in stages ie pull a small amount of vac and close off the valve, position the bag carbon etc and pull some more vac. Continue this way until you have full vac and everything is in place and tight against the mould surface. If you are not happy just release some of the vac and start the process again. Carbon Copies Ltd
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	yep, should do that as well. It's a kind of (bad) habit I have, like if I was working with prepreg ^^
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CarbonMike	CarbonMike posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 31, Visits: 45	fgayford (05/06/2013) It almost looks like the epoxy is not cured to a hard state and the sanding dust is fusing into the soft surface? This without a doubt. I am a composite trimmer/fitter/laminator by trade, and have seen this happen many many times on virgin parts.
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	CarbonMike (23/06/2013) fgayford (05/06/2013) It almost looks like the epoxy is not cured to a hard state and the sanding dust is fusing into the soft surface? This without a doubt. I am a composite trimmer/fitter/laminator by trade, and have seen this happen many many times on virgin parts. Thank you CarbonMike What I do now is I wait for 48hrs+ before demolding. What I could try is some post curing to reduc this delay, I guess.
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