Talk Composites - The Forum for Advanced Composites

finishing after infusion

http://www.talkcomposites.com/Topic33419.aspx

By 8900120d - 7/25/2019 12:13:58 PM

Hi guys, 
Ive finally got the hang of making moulds and infusing. ive managed to infuse several times, however i get pin holes in the same area everytime, which makes me believe its the mould?

its an automotive part, so it needs to have a nice appearance but it also needs to be protected from the elements. 
i have experimented with XCR :
1. apply 2 coats of XCR
2. sand down with 180 grit until smooth
3. apply 2 coats of XCR 
4. sand down with 240 grit until smooth
5. apply final layer of XCR 
6. sand with 400 - 800 grit
7. polish

however everytime i apply a layer of XCR, by the time it becomes tacky it has loads of "craters" (see pic) 
it feels like a never ending process to get it smooth again and then apply another layer which again has craters when it drys!

the reason why i use XCR is to get hide of the pin holes and small dry spots in the corners on the finished product
but its an extremely long process! especially if i decide to sell this part.

is there a quicker method of using resin clear coat which will get rid of a small amount of pin holes and dry areas?

for e.g; can i apply 2 layers of XCR, sand down with 180 grit, and then spray some automotive clear coat ontop?



 
By MarkMK - 10/4/2019 4:15:44 PM

Completely normal given the relatively large diameter nozzle (FN6?) and an 'orange peel' surface is fine, as long as you've not got too many large-ish lumps that might serve to distort the fabric once infused. If so, just smooth these down a bit with some coarse paper. 

You might find that warming the gel coat a little prior to mixing-in the catalyst will leave a slightly smoother finish, but be mindful of the gel 'going off' quickly if the spraying takes more than 10 mins or so. The GC50 is quite thin already, so unless it's below 15 degrees C where you're working, it should still spray on okay

The cup gun is not such a precise instrument, but as long as you're spraying with a decent pressure it you should be able to get an even enough coating with a little practice.