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Old 04-15-2014, 04:34 PM   #11
Gilbert

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Here is my mold that I ruined where I let a layer of resin cure prior to wet laying
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Old 04-16-2014, 01:08 AM   #12
morepower

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Quote:
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Here is my mold that I ruined where I let a layer of resin cure prior to wet laying
If you ruined a mould I would say you need to get a better release agent. What do you use? If you want a good finish you can use Marbocote fastcote or their 227ce release. Both are a wipe on and leave release so you do not need to buff them up and both will give a good cosmetic finish.

Here is a cover for some diving bottle system and it releases wonderfully...


Now for the voids and pinholes. I have done quite a lot of wet lay vacuum bagged parts but all of them have been in polyester resins. I found I could get a good part but it was variable and failure rates were too high for me making cosmetic parts. I swapped over to pre-preg because of it.. But I would use a preforated release film with the least number of holes possible as it would restrict the loss of resin from the part but still allow some trapped air off the part. I also found putting some peel ply round the perimeter helped too... I would put the peel ply over the last layer on the flange area and that would help too... I always used to run a full vacuum.
I swapped to pre-preg just to save money to
be honest.. OK the materials do cost more but if you do wet lay vacuum bagging you only need to have an oven and controller... The money I saved with the lower percentage of scrap parts (single digit I would say) it just made sense.

The oven can be quite simple and made using a fan heater and MDF.

Even getting the controller from ebay is cheap and accurate. I was testing mine here to see and used an old meat thermometer to check and I get it to 1 degree maximum deviation when I check it on the opposite side to the controller thermocouple and at a lower level. With parts in there the turbulance should make the oven even more accurate.
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Old 04-16-2014, 05:57 AM   #13
sammymatik

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Nice setup. I"m actually gonna do this in the next week or two myself. I agree with the reliability of pre-preg, it's worth the extra curing expense. Plus if you cure the parts at 180 or more you should be pretty covered for any normal operational temperatures. Besides, the oven controllers are not expensive and the heaters as well. The only thing I really need to invest a few more dollars in is a freezer and more bag material.
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Old 04-16-2014, 08:41 AM   #14
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Here is my mold that I ruined where I let a layer of resin cure prior to wet laying
Gilbert, explain to me your release agent strategy. I don't understand frekote and wax. Are you using sealer with the frekote? Please explain your release agent.


Morepower

I'd love to swap over to prepreg, but I have a great supplier for my epoxy, so I would probably end up paying alot more. I also mainly do large car parts and would have to construct a large oven to suit my needs, so infusion is where I'll stay at for the near future, but I do eventually want to move to a setup like yours.
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Old 04-16-2014, 09:06 AM   #15
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I wipe 3-4 coats or frekote on the mold drying between coats. Then I apply 1 layer of wax and polish the mold. The reason I do this is because when I only is frekote and I apply a layer of resin in my mold I have issues with it separating and fish eyeing so I don't have a smooth coat across the mold. The wax seems to help cut back on the resin separation. I tried a sample last night where I had a small leak on my vacuum bag to cut back on vacuum because I currently do not have a regulator. It is by far the worst part I have made so far. Next question, is it better to wet the fabric out first and pay it in the mold or put the fabric in the mold dry and then wet it out with a brush? I have to find a way to have a better cosmetic finish soon because the supplies are about to break the bank. I really do appreciate the help.
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Old 04-16-2014, 12:41 PM   #16
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Quote:
Originally Posted by Gilbert View Post
I wipe 3-4 coats or frekote on the mold drying between coats. Then I apply 1 layer of wax and polish the mold. The reason I do this is because when I only is frekote and I apply a layer of resin in my mold I have issues with it separating and fish eyeing so I don't have a smooth coat across the mold. The wax seems to help cut back on the resin separation. I tried a sample last night where I had a small leak on my vacuum bag to cut back on vacuum because I currently do not have a regulator. It is by far the worst part I have made so far. Next question, is it better to wet the fabric out first and pay it in the mold or put the fabric in the mold dry and then wet it out with a brush? I have to find a way to have a better cosmetic finish soon because the supplies are about to break the bank. I really do appreciate the help.
Alright first off, you did use the Frekote mold sealer (frekote FMS) before you put the frekote in the mold? Because if you didn't then your mold is still porous and that could explain the bad releases. And hopefully the 3-4 coats the frekote was just initially because you do not need to use frekote every time. You can apply a few more coats after the first pull, but after that it is semipermanent, and you can get away with multiple pulls before needing to recoat.

Okay, you should eliminate the trying to have a gelcoat layer because right now its more important to just try to get an acceptable part out of the mold. After you get the hang of that, then you should look at adding a gel layer in the future. It is possible to use a heat gun to get a first layer of epoxy to set, but right now, but in my opinion you should hold off on that until you get the other issues fixed.

If you still want to have a gelcoat layer, then it would better to just spray the mold with PVA partall instead of using the wax, but in this scenario the frekote is just wasted.

I would Brush a layer of epoxy, and then lay in my first layer of fabric. Take extra care to make sure you have it in correctly, and that it is down. Pleat where needed. After this layer is in saturate that layer, and then add subsequent layers, saturating the fabric after every new layer.
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Old 04-16-2014, 06:14 PM   #17
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If you've got a well polished mould, ie. 2000 grit then polished with cutting compound, then you won't have an issue with not sealing the mould before using the Frekote. I don't use the sealer, I never have. I pull parts from epoxy moulds, vinyl ester moulds and polyester moulds without issue. However I always do 8 coats of the Frekote initially, then another coat between each pull.

The one thing I'm not sure about is using the wax with the Frekote. I know it's common practice with semi perms, but I've never personally tried it and I have read about several people having issues with release after using Frekote with wax. Fasta could probably comment on that, I believe he does use the two together frequently. Could depend on the brand of wax too.

OP, how long are you leaving your 'gelcoat' layer before laying up your fabrics? If it's delaminating, my suspicion would be that you are leaving the resin too long and not getting proper adhesion.
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Old 04-16-2014, 07:02 PM   #18
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Hanaldo, I understand what you are saying that you can get away without the sealer if the mold is smooth enough, but with the pictures that the OP showed of the first layer of epoxy being adhered to the mold, then that suggest that the ruined mold was not to that level or did not have adequate release, which is why I suggested that he use the sealer in the future to assure that the epoxy releases.
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Old 04-16-2014, 07:10 PM   #19
Gilbert

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I let the gelcoat completely cure, then I sanded it with 1000 grit to scuff it before I laid the fabric and it didn't adhere. I am going to let it stand until tacky next time. First I need to figure out why I have a lack of resin on my finished product and why I can't seem to get a smooth cosmetic surface side.
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Old 04-16-2014, 10:33 PM   #20
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Yeh that's definitely the issue then. 1000 grit is faaaaaar too fine, that won't give any adhesion at all. With epoxy, you want to be using 80 grit to scuff it for mechanical adhesion. BUT, with a gelcoat you don't want to be sanding it at all. First of all you still won't get the same level of adhesion as you would with a chemical bond, and secondly if you scuffed it with 80 grit to get a sufficient bond then the gelcoat would no longer be clear and defeats the purpose. It NEEDS to be done while the resin is in a tacky state.

As for your parts, I don't think the look TOO bad for wet-layed parts. If you're drawing resin out of the part while it's under vacuum, why not clamp off the hose?

Wildcard, apologies, I hadn't seen that photo. You're possibly correct about that, though with the cost of Frekote's sealer I personally prefer to just get the mould to a better finish haha! Having an inadequate bond to the gelcoat layer is also likely to have caused some issues there.
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