Gelcoat and alligatoring

General Composites Discussions Products Talk
#1

I know this has been covered before but…

on my first hood mold, i sprayed the first layer of tooling gelcoat, left it for 2 hours, then sprayed the next one, and after another 2 hours started laying fiberglass.

i got alligatoring all over.

on my 2nd mold, i sprayed only 1 layer, left it for about 12-15 hours, and layed fiberglass on top of that. it came out sweet, but it still got a patch of alligatoring like 5 x 4 cm at a place!! :eek:

why? what am i doing wrong? i know that the reason for laying fiberglass while the g.c. is not completely dry is to make a better bond with the resin and the glass , but still… was that a reaction the gelcoat did on its own?

#2

im not a pro with spraying gelcoat but i wil say this…from my knowledge its because its sprayed too thin when you get that…ive had it on 1 part and it was just because it was thin…let me find a picture of a mold i recently sprayed…ill spray the entire mold and after the cup is empty ill spray some of the air to force the gelcoat into tight tight corners that normal spray wouldnt get into…hence the reason it looks like it does…but you can see how thick it is after 2 layers, i used 4oz in each layer on this mold

layup0.1.JPG
layup0.1.JPG800×600 108 KB

and this was on mydesktop so i figured id post it too :stuck_out_tongue_winking_eye: gotta love bein on 1 wheel!!! maybe ill post more of me stuntin it up

stunt9.jpg
stunt9.jpg600×627 205 KB

#3

layup3.JPG
layup3.JPG800×600 89.4 KB

after the glass

#4

super-polished-sv650-part.JPG
super-polished-sv650-part.JPG800×600 411 KB

after some polishing

#5

I spray the gelcoat to the proper thickness in 1 coat, and let it B stage. Then infuse the mold. We NEVER use CSM on anything. It consumes a ton of resin, has little strength, and looks like crap. Resin rich areas increase exotherm, and increase chance of alligatoring thin gelcoat areas.

Here’s a prepped plug, coated once with gelcoat and ready to infuse the mold. This is how the surface should look when done right:

#6

These tanks are made from CSM, are strong enough for use on serious competition motorcycles but not as strong as other materials, lighter than the std parts, and I think look quite nice on the surface…

#7

yea those look really nice actually

#8

on more complex parts esp ones that i use clay on glass…the parting edge along the part…spray gelcoat wont get into those tight corners so i lay down 1 coat and use the air to try and force it into the cracks, wait an hour until stage b and spray up another layertrying to get in the tight spots

#9

so you guys say that its how thin the gelcoat is that causes alligatoring rather than the time passed between 2 gelcoat spraying sessions… the first i got which got the most alligatoring was a lot thinner than the other now that i think of it…