I infused a part this morning and all seemed to go fine,no air leaks etc.When I removed the part from the mold the gelcoat had seemed to seperate from the rest of the part in a few places at the edges .It did not look like a dry spot and the carbon below was totally infused.It was very hot in the shop at the time and the part got very hot to touch as the resin went off.
Could this extra heat be the problem or is it possibly that the vinyl ester resin doesnt like the the polyester based gelcoat?.
The laminate was 1 layer of 200g 2x2 twill carbon and 1 layer of 300/d3/300 rovicore.Here is a pic of the problem
All PER?
How long was the gel coat cured before VIP?
Sounds like expansion and temps between the two were too great.
Try a slower and cooler resin cat %?
Thanks Werksberg
Gel coat had cured overnight before infusion but I have infused a part recently that was laid up but never bagged for weeks with no problems.I was also trying out a new gelcoat that I think is actually designed more as a clear casting resin somebody reccomended to me so maybe there is a problem there to.Re gelled the mold with durabuild and will try another infusion to see how it goes.will move it to a cooler part of the shop as well with no direct sunlight.The place I infused before was below a clear rooflight and got very hot.laminate became almost too hot to touch as it went off.I also have a new infusion resin to try.its actually a polyester designed for rtm but the viscosity is 200cps so should work good with infusion as well.its about a third of the price of the reichold vinly ester infusion resin im currently using.
clear casting resin needs to be in big quantities to cure properly… no thin layers like gelcoat. i think there lies your problem.
Well, if the gel coat was applied real thin, let to fully cure and then a hot batch lamination done…that is a sure way to get “alligatoring”…or the lamination resin pulls up the gel coat as the Lam. shrinks up more.
pop off a little section of that gel coat that seperated and see if it is sticky underneath.
Did another small test infusion using durabuild clear as a gel as I know this works fine.No high heat build up this time and infused while the gel was still tacky.Had exactly the same problem with the gel not sticking to the laminate below.I now think it is the vinyl ester resin that is the problem as it was still sticky on the surface of the cloth below the gel when I peeled it off.This batch of resin is now about 9 months old and perhaps is going off.No use by date on the keg.I have noticed that some other vinly esters have a very short shelf life.Will get some of the other resin tomorrow and give it a try.Thanks for all the advice guys.
I would definitely say it’s old stuff. VE past 3 months is considered old IMO.
Are you buying 55 gallon drums? Should use it up fast otherwise, as the styrene evaporates as the resin sits, which causes viscosity to increase along with gel and cure times.
You can help to increase uncured resins shelf life by injection a little nitrogen into the containers while closing the lids and storing it in refegerators.
It is oxygen that starts the curing reaction…
Casting resin doesn’t work well for composites work. We tried a whole gallon of it using different techniques and none with great results.
Remember the other bad thing with clear casting resin is it will yellow with age.
Buy styrene monomer and add as needed 
That’s not a solution, it’s a shortcut to fix problems that shouldn’t occur anyways! How do you know how much has evaporated and then how much to add?
No pun intended?
add 5% he’s not building airplanes haha.
anyone think about if the fabric was pushed into the mold corners well enough? The problems seem to be in sharp corners…
If the fabric was bridging…then of course it won’t touch the gelcoat.
Fabric was well down in corners.I allways spend time making sure it is because the ve resin is green and a resin rich corner shows up badly.the gel actually peeled away all over the next test part even on flat areas.Got the new resin today and it works perfect.no dry or peeling areas and it costs 1/3 of the ve I was using.I now am sure the problem was the ve resin which was past its best.