precaution when trimming your part ?

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precaution when trimming your part ?

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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	Ok, I see what you mean; thanks Warren
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	Ok so now I have a good surface finish, At least, no bubbles anymore (I let the resin flow some time after it reaches the outlet connector, then clamp off the vac line, then the feed line) But, as you can see on the picture below, I'm facing a new problem, that occured during the trimming step. More precisely, in the sanding step that comes after the Dremel trimming. It looks like the gel coat is delaminating. It's only 4 or 5 spots like this, and only on the part perimeter. As if it did not like me sanding with the permagrit files. What could these defects be the symptoms of ? Is there a risk it propagates ?
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fgayford	fgayford posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 433, Visits: 1.2K	carboncactus (05/06/2013) Looking at that last picture....... Take a heat gun to the surface for a couple of minutes. I have taken prepreg parts out of the oven and they looked a bit flakey. Like dry skin, sort of. Applied heat and the epoxy gelled a bit then fully cured, absorbing the dryness. I will second the heat gun attempt. Fred Did you lose vacuum when making this part?
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	fgayford (14/06/2013) carboncactus (05/06/2013) Looking at that last picture....... Take a heat gun to the surface for a couple of minutes. I have taken prepreg parts out of the oven and they looked a bit flakey. Like dry skin, sort of. Applied heat and the epoxy gelled a bit then fully cured, absorbing the dryness. I will second the heat gun attempt. Fred Did you lose vacuum when making this part? Hi Fred, are you refering to the problem shown on my very last picture, or the former ones ? Also, I can't be sure about losing the vaccum, apparently no, but how to be sure since the bag is clamped at both extremity (vac + feed lines) and there is no gauge on it anymore ? thank you
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carboncactus	carboncactus posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 243, Visits: 1K	Your vacuum was good, as there is no pinholes. Unless vacuum was lost after gellation Does the gelcoat follow the shape of the part? If it does, then you just had a bridge. Inject it with some more GC50 next time you mix some up. Edited 12 Years Ago by carboncactus
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	carboncactus (14/06/2013) Your vacuum was good, as there is no pinholes. Unless vacuum was lost after gellation yeah, I'm really starting to consider this might have occured. Hard to know though. Do you think that if I warm up the border with a heat gun, the, the GC would stick to the resin again ? Does the gelcoat follow the shape of the part? If it does, then you just had a bridge. Inject it with some more GC50 next time you mix some up. Yes the GC follow the shape. But don't see how to "inject" it.
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carboncactus	carboncactus posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 243, Visits: 1K	No the heat gun trick is only for uncured epoxy laminates. Get a smackhead needle on eBay, lay the part down so the void is horizontal, then stab with a pin. When you get the courage, inject some gelcoat into the void. You could also use lacquer or epoxy. Let it overflow a bit and cure. You should have a tiny blob just poking out. Rub it with 1500 and polish. Edited 12 Years Ago by carboncactus
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	Dr House party ^^
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wozza	wozza posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 688, Visits: 5.4K	Jess8bit (14/06/2013) Ok so now I have a good surface finish, At least, no bubbles anymore (I let the resin flow some time after it reaches the outlet connector, then clamp off the vac line, then the feed line) But, as you can see on the picture below, I'm facing a new problem, that occured during the trimming step. More precisely, in the sanding step that comes after the Dremel trimming. It looks like the gel coat is delaminating. It's only 4 or 5 spots like this, and only on the part perimeter. As if it did not like me sanding with the permagrit files. What could these defects be the symptoms of ? Is there a risk it propagates ? Nice to see that you are getting a much better finish. Sort out what looks like bridging on the edges and job done. Remember you can never have a bag that is too big but you can certainly have one that is too small If you lay down your first layer of carbon when the GC50 is still a tiny bit tacky approx 3-4 hours depending on temperature then it acts like "spray tack" holding the carbon against the surface of the mould. You can make sure that the carbon is fully down all over the mould before continuing with the rest of the stack. This way you should not get any bridging. Warren Carbon Copies Ltd
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Jess8bit	Jess8bit posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 133, Visits: 566	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 ?
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