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Matthieu Libeert
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it's been a while, I haven't been working on the helmet since a long time but now i'm going to finnish it  I will need some advice... I didn't used any gelcoat this time. The problem I have are some dryspots. I've seen the movie with the kayak on how to repear small areas. Should I put some extra resin to fill the dry spots, then sand the whole helmet, then use a clearcoat and pollish? I won't use the helmet because I've made a "little" designmistake in the beginning of the project; I've used the "strongest resin" I should have used a flexible resin to absorb the impacts on the helmet. Still have the mould so will be for the next helmet Can someone tell me how I should finnish it? heres a videotutorial on how the helmet was made.
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Matthieu Libeert
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Ok Matt, Thanks for helping me out, So maybe I'll first explain the whole proces in full detail on how I've worked. 1. The product I want to reproduce was the helmet and it's backplate (top of this topic) 2. I've waxed the helmet 5 times I think with TR 104 High temp mouldrelease 3. I've mixed some vinylester gelcoat (transparent) and added some colour (red) 4. Second layer of gelcoat once it got tacky 5. Put polyester on the gelcoat 6. First layer of Fiberglass with gelcoat 7. many more layers for a strong mould LET IT CURE FOR 2 DAYS 8. Sanded the mould smooth with sanding paper grid 600-1000-1200 9. Pollished with your Pollishing liquid (Pollarshine C20 and Pollarshine F05 TWO WEEKS PASSED BY 9. I've did a first test with just 2 thin layers of fiberglas (no vac bagging) and polyesterresine to test for the finnish 10. Product came out how I've wanted and Finish is good ONE WEEK PASSED BY (no smell) Waxed the model with the same mouldrelease 6layers I guess ( waiting for it till it dries and pollish smoothly by hand in circular movents) 11. Mixed gelcoat and apply 12. Mixed gelcoat layer 2 13. Brush epoxy (IN expoxy) 14. Add first layer of reinforcement) 15. more layers with where added 16. Bagged everything and part came out very difficulty 17. The part was strong and firmly bonded together but the first layer of gelcoat (layer on top) was still jelly and sticky THE FIRST LAYER OF GELCOAT DIDN'T CURE (probably my mistake whrong measurement of A+B) 18. Started again and mixed everything very precisely A+B and mixed it with a plexi stick (mixed for 5min by hand in a cup, stirring in all directions and scraping the entire cup from up till down) 19. Apply first layer of gelcoat and waited for 3h (in my garage at around 20degree) everything cures and got tacky 20. New epoxy gelcoat and applied on top of the first one. 21. waited for it to get tacky 22. add first layer of epoxy IN and put all reinforcement materials on top TIME FOR DEMOULDING AFTER 26h under Vacuum (bagged) 23. Had to hammer the part out with a wedge and hammer because everything was firmly stucked together. 24. I Hear some cracking sounds and got more careful 25. the part comes out but there is hardened out gelcoat sticking on the mould and missing pieces on my part. EXTRA - The fact is I have some experience with infusion and bagging and so on and everything went perfect (vinylester mould, waxed, added all materials, bagged, came out perfectly I.E carbon car model few comment above this one). - I'm surely not saying this is EC products it doesn't work out now  it's just that I want to know for myself WHY it doesn't work out, so I can learn out of it and not making the same mistakes... - Thanks again for the time all of you spend helping people out!
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Matt (Staff)
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Hi Matthieu,
There should be no compatibility problems between a vinylester mould surface and our epoxy gelcoat although if you're only using mould release wax then I would hope to hear that the mould was very thoroughly cured before you used it because the styrene (partiuclarly from the polyester resin you used to reinforce the part) would still be leaching out of the gelcoat and through the gelcoat for quite a few days after making the mould. Epoxy gelcoat should behave, in release terms, just the same as an epoxy resin (i.e. a part made with no gelcoat). If you can normally release epoxy parts out of your vinylester moulds (which I would expect that you can) then this should be no different.
It would be useful to know when the mould was made (how many days/weeks/months old is it) and also whether it has undergone any kind of a post cure. Finally, does the mould 'smell' of polyester; i.e. can you still smell the styrene in it.
Regarding your use of the epoxy gelcoat, perhaps we could look closely at that for a possible explaination. How long did you leave the epoxy gelcoat to cure before you backed it up with the epoxy resin/reinforcement?
The cure problems that you've had with the gelcoat I could say with reasonable confidence are down to the thoroughness of the mixing of the gelcoat - it's a very thick substance and it is difficult to get the hardener to full disperse through the gelcoat. We have been contacted several times by people who experience curing problems with all of our epoxy gelcoat and the problem is always attributable to thoroughness of mixing).
I think some readers of this thread might think you're using our GC50 Epoxy Compatible Polyester Gelcoat but actually you're using our Clear Epoxy Gelcoat. The GC50 (seen in the bonnet making video) is much thinner and also, being a polyester gelcoat (so reacted with a catalyst, not a hardener) does not require such thorough mixing because the reaction is a chain reaction not resin/hardener pairs.
If you could post me some answers to the above points I'll see if I can identify the problem more accurately.
Best regards, Matt
Matt StathamEasy Composites / Carbon Mods - Technical Sales
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Matthieu Libeert
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Thanks for your reponse Warren! the fact is that I'm kind of familiar with the technique and had some good results in the past with vinylester gelcoat on a polyester gelcoated mould this is an example  The thing I would like to solve is to know if there is a problem with the combination of vinylester gelcoat and epoxy gelcoat... The mould is ultra-clean and ultrasmooth so that shouldn't be a problem.
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Warren
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are you using the uni-mould system??? that is supposed to be compatible with epoxy and shouldnt have any release issues at all. The system was used in the bonnet video. Maybe you might want to try a chemical release agent like Easy-Lease. The product video of the bonnet they used easylease and wax on top to make the mould then easy lease on the mould to make the carbon part. I would suggest getting your mould really spotlessly clean then re-doing your release agent. If youre using a chemical release agent, the surface should feel really slick to the finger once the release agent has been properly applied.
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Matthieu Libeert
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Group: Forum Members
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Hi, Ok so all my projects went well untill now, but now I'm having some trouble with this gelcoat :p The first time it didn't cure...  Now the gelcoat broke after I had to force it a bit to get my part out of the mould...(had to hammer it out of the mould ) Some part of gelcoat still on the mould, some are on the part... The mould was waxed over 7 times with mouldrelease so shouldn't be a problem.
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Matthieu Libeert
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Haha nice!
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Joe
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Hi, Thought I would share what I have. I'm a lazy guy so I had to do something which keeps work to a minimum...It cost me nothing, and it's reusable. The downside is that degassing the resin is mandatory, but hey I'm never in a hurry 
 A $1000 electronic device will always protect a 10 cents fuse
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Manu
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 q this is what I use, does its function and very low cost! throwaway
www.ktuning.es https://www.facebook.com/Ktuning.es/
www.carboncycleparts.com
https://www.facebook.com/CarbonCycleParts/
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Matthieu Libeert
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Group: Forum Members
Posts: 955,
Visits: 3.4K
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