First mould attempt


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jonnyl888
jonnyl888
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Hi, just attempted making my first mould of a spoiler. So I pretty much followed the how to make a carbon bonnet video tutorials but one thing I didn't have was filleting wax. I used signboard all the way round and the inevitable happened. The gel coat seeped through under the part. What's worse was that it was difficult to get the chopped strand mat to stick into the edges without creating an air void which weakened the gel coat at the edges. As you see in the picture below, I got the basic shape and very nice shiny surface even with PVA, but the "mechanical lock" caused by the gel coat made me impatient and I ended up forcing the part out and cracking the edges around it. I really don't want this to go to waste, so is it worth repairing? Can I use fibreglass car body filler to do the job? Or is this a better way?

Thanks

http://www.talkcomposites.com/Uploads/Images/e25a5c00-0915-4bbc-b448-20ef.JPG
Edited 12 Years Ago by jonnyl888
carboncactus
carboncactus
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I had a similar issue when making a wing mould, the CSM didn't get into the corners, even though I bent it before applying then pushed it in. When I released, the mould looked impeccable..... Until I postured it in the oven and blisters started popping up. Then I took a screwdriver and tapped the corners an it revealed just how much air was in the mould:



After speaking to some people, they suggested mixing the gelcoat with some silica and milled glass to make a paste, then spreading this paste into the corners to give it more of a radius, then laying the CSM on top of that. 

After doing this for a few months, I'm convinced you can't get a mould right the first time, or the first 10 times for that matter. Theres too many variables, and something WILL go wrong. It also doesn't help that when you're looking for help, different people give you different and often contradicting advice.

As for your mold, start over. Repair work is a different art altogether. Repairing a mould with that much damage will take you much longer than binning it and starting over. Also, the repair work will be weaker and will inevitably cause issues down the line. 

http://www.talkcomposites.com/Uploads/Images/db628ad5-e0e7-47b9-873a-3d84.png
jonnyl888
jonnyl888
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Yea, I might end up binning it. I was looking at the fibreglass putty, which would make life so much easier. Do you think it's worth giving this a try? Will it work out more expensive or similar?
Jaydien
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I'm a still at noob at this, so take everything I say with a grain of salt. 
I saw this first tip on YouTube. 
Get some woven roving and extract one thread of the weave. Use that thread on the hard angles BEFORE you lay anything else. 
I think I also saw that guy just use clumps of individual fiberglass strands on top of the tacky gel coat and soaked it with resin. I might be wrong about that, though. 
My personal THEORY is to lay the chopped strand mat in small sections. I've started two moulds like this so far. They are the unseen "bottom" sides of interior car panels which are extremly complex and have MANY right angles. I've only done one layer so far and my technique needs MUCH refining, but I think it could be a very promising course of action. It's a pain in the ass and is extremely time consuming. You need to measure, measure, measure. Everything must be cut before you start anything else. 

I hope this isn't against the forum rules, but the YouTube video is by gasserglass, I believe. Their not well edited at all and very long. I would actually have to call it "unedited". They are very boring as it's basically just a dude going about his fiberglassing and talking story (i think you Brits call that jawing) like you're a dude just hanging out at his shop with him. However, you do pick up a good tip every now and then. 
Jaydien
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Also, just so you know, I've yet to make a single mould I would consider useable. I've made 5 so far and totally agree with carboncactus. You definitely are not gonna get it right the first bunch of times. 
wozza
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Are you using a finned/bristle roller when you lay up? You need to give the whole area a good going over with the roller especially any corners particularly internal ones. This should get rid of any trapped air. Also after using the roller I go over any difficult areas with the heat gun, this also helps to "pop" any small air bubbles. Hope that helps. Also for moulds I tend to make them resin rich.

Warren

Carbon Copies Ltd
carboncactus
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jonnyl888 (10/02/2013)
Yea, I might end up binning it. I was looking at the fibreglass putty, which would make life so much easier. Do you think it's worth giving this a try? Will it work out more expensive or similar?


The putty is made of resin, chopped strands, milled glass, and some sort of powder like fillite or talc. Give it a shot, there's no harm in trying. Some people will tell you it's no good, others will tell you it's a must. I've got some here I'm gonna try next. I have seen moulds that are mainly putty sandwiched between some glass layers.

http://www.talkcomposites.com/Uploads/Images/db628ad5-e0e7-47b9-873a-3d84.png
wozza
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I have had mixed results when trying to repair moulds. If it is being used for wet lay then you have a chance. If you a planning to infuse from it then remember just the smallest pin hole will prevent you from holding vacuum. If the part is a one off then I would say give it a go, but if you want to pull a few parts from it then make a fresh mould it will work out cheaper and less hassle in the long run.

Carbon Copies Ltd
jonnyl888
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I didn't use a roller but I probably will next time. I used normal EL2 epoxy laminating resin and ended up using more than I thought I would making it quite expensive. I just realised, should I be using that uni-mould tooling resin? It seems so much cheaper, does this work with the clear epoxy gel coat or do I have to get the uni mould one?
wozza
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The Epoxy Resin could be the problem. Depending on which CSM you used epoxy won't break down the binders in the CSM. Therefor it remains stiff and inflexible. The Uni-Mould system is excellent, it's a three part system and works really well. I use it all the time and my moulds come out bang on first time every time.

Carbon Copies Ltd
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