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Old 10-17-2013, 02:03 PM   #1
craj1031tx

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Default in mold clear compatibility with release agent

Hey all,
I'm trying out the in mold clear method using a 2k automotive clear which is sitting above frekote 770 semi perm. I'm getting some beading in areas though. it appears that if I really hit it hard with a thick and heavy coat, it doesn't bead up, but medium coats for whatever reason are able to.

has anyone ever experienced this? is 2k paint even supposed to bead with a semi perm? I saw wyomings video and he seemed to have an easy enough time applying it after a wipe down with semi perm.

I would imagine the best way to apply it would be one ultra light coat at first that can flash nearly instantly - this would be the contact coat with the frekote semi perm release - and then whatever (light to heavy) coats afterwards since there is no contact anyways. is this correct? I haven't had time to experiment with this yet though.


Thanks in advance!
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Old 10-17-2013, 07:21 PM   #2
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Hi
I paint all my planes in mold with 2k. I use marbocote and chemrelease semi perminants.

By far the best way is as described. Fine dust coat , and then follow up with thicker coat etc.
Also one thing to try is wax over the semi. Doing this gives the paint something to bite to and reduces fish eyeing or beeding. I done this with marbocote , but I don't need to do it with chemrelease.

Tim

gizmo 36 glider

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Old 10-17-2013, 11:28 PM   #3
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I agree with Tim. Use a silicon -free wax.
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Old 10-18-2013, 01:45 PM   #4
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Thanks for the advice! I'll put a layer of Meguairs #8 and see how that works (I'm assuming that's silicone free, right? their product page doesn't say but I've used it with PE before so I'm guessing it is).


Anyways, I pulled some the IMC test parts today. I did 3 panels each, all laminates are impregnated out of mold;

1) part with a .6 oz/yd FG veil that I also wet out with epoxy in the mold before laying the laminates down

2) part with a .6 oz/yd FG veil, NO surface wet out (surface between IMC and laminate stack)

3) straight carbon part. for this part, I wet out half the mold with epoxy before introducing the stack and the top half was dry; the laminate was laid directly on top of the IMC.


Here's a photo. What are the white chalky lines between the weave patterns? Are those air gaps between the fiber partern and the clear coat?

https://skydrive.live.com/redir?resi...KeWGh16iAE&v=3





WP_20131018_001 by redalert1031tx, on Flickr


WP_20131018_002 by redalert1031tx, on Flickr




Will sanding take care of it or will I just burn through the IMC layer into the voids?
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Old 10-18-2013, 02:55 PM   #5
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To answer my own question, sanding will just burn through it and open up the air voids. The gaps between the weaves are still there, deep as ever. I'm thinking I might be using too little resin, and too much of it is getting wicked away by my breather.

I used a P6/P31 perf release film (very widely spaced pores) and it worked well but then I got too much resin build up in corners where the hole pattern didn't match up with the very tight radius curves so using it isn't possible.


I'm thinking the next step is to just crazy over saturate the laminate stack and hope for the best. I just ran some numbers and it turns out, for a 1.2:1 fiber to resin ratio I need to be using about 100 mL of resin per part instead of the 80 mL I've been using, so hopefully that'll improve the situation

I'm using strechlon so reducing vacuum isn't an option either :/
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Old 10-18-2013, 06:15 PM   #6
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It does look like the backing is sucking out to much resin. Either way it is very even across the laminate. So I agree try more resin , roll it very well with fabric roller , and back off vaccum a little.

Tim
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Old 10-18-2013, 06:18 PM   #7
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sounds like the same problem im haveing in the air bubble/voids post... we cut out the 3/4 oz veil and the voids were still there with -24 vac but it was better then with the veil sinve the air was trapped between the two layers.. we had a 1.15 to 1 ration and upped our resin as well.. It helped but still now where I want to be.. I was told to lower my vac after my initial deep pull... ( large vac will make any air voids larger.. less vac will make smaller voids... ) kind of a strange way to think but with less air in the mould the bigger the bubble is.. The whole pressure thing..

keep posting if you get it dialed in..
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Old 10-20-2013, 07:38 PM   #8
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Had another round where we upped the resin fraction significantly, and while things did look better there are still voids between the IMC and the fabric twills.

Midwest, how long do you run your part under full vacuum (or at least as full of a vacuum as your pump can get you to - mine can't get us very far :/) before reducing vacuum back to shrink down the enlarged air bubbles?

What's the upper limit of low pressure (the reduced vacuum pull) that you can/should run at for the curing stage after debulking the reinforcements at high vacuum?
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Old 10-21-2013, 03:01 AM   #9
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What are the minimum and maximum recoat times on the clear coat?
Are you degassing the resin?
Has the resin been thinned? i.e. Does it have high solvent content?
Why are you wetting out the cloth out of mould?
Are you consolidating the laminate stack before bagging?
How much vacuum?
Gel time?
Time under vacuum?
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Old 10-21-2013, 12:29 PM   #10
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What are the minimum and maximum recoat times on the clear coat?
Im using a fast activator and when I set up the bag with the laminates, its not tacky at all anymore. the one I made yesterday was allowed to cure for 2 hours in the sun (molds are black so they got up to 100f)

Are you degassing the resin?
Yes, but to be fair my vacuum pump has seen better days so it never pulls a 'full' vacuum

Has the resin been thinned? i.e. Does it have high solvent content?
no, but it is a very thin resin - sp115

Why are you wetting out the cloth out of mould?
this is more of a production thing - it is much faster for me to do the main wet out outside of the mold, lay the laminates up, and then do some extra wetting out inside of the mold

Are you consolidating the laminate stack before bagging?
I'm not sure what you mean by this. I am laying up multiple dry plies of fabric and then wetting them all out on a flat surface all in one go, and then laying them into the contours of the mold. i'm insuring that the resin soaks through, or at least the best I can. the 'bottom' of the laminate stack appears to be as wet out as the top when I do this

How much vacuum?
honestly I don't have a proper gauge so I can't tell you specifically but it's definitely not a full vacuum. one of my problems is that i'm using stretchlon so I have to have some amount of vacuum, otherwise the bag doesn't full compress corners down.

Gel time?
no gel time, essentially immediately after wet out (10-20 minutes) I set it up in the bag and pull a vacuum

Time under vacuum?
quite a bit, i'm working outside in very variable weather conditions so I usually let it sit under vacuum for hours to insure a decent cure before shutting the pump off, at which point it immediately goes to atmos. pressure (stretchlon.... can't hold a vacuum worth garbage)





I really want to go the wet lay and bagging method to work but at this point i'm considering trying a vacuum run. trying to get my hands on some mti hose but for right now i'm going to settle with the old school spiral and single point draw method

Chetan

Last edited by craj1031tx; 10-22-2013 at 12:18 AM.
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