What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Can you spray West 105 ?

Larry DeCamp

Well Known Member
I have re-read the pinhole filling threads. I have large areas of smooth fiberglass on cowl, pants, canopy etc. that have not been filled with micro cosmetic work. The Dan H credit card pinhole process is compatible with small areas but leaves ridges that risk glass balloon fracture when sanding.

Also, 80 grit sanding to feather micro filled areas can leave abraided glass , a potential pinhole source ? Dan advises to not thin 105 with acetone. I have tested it over sanded micro and it feels great, but, no long term experience .

My curiosity is to prep pinholes with credit card, cloth/sponge wipe , sand “carefully” etc,
Then spray with thinned 105.. this would leave a finish for minimal 220 wet sanding ready for primer. Your thoughts ?
 
Larry,

I'm all in for sensible experimentation...but if you want to spray, just buy a water-viscosity epoxy. My old favorite is System Three Clearcoat.

That said, reading your account suggests some confusion. Using a squeegee to wipe on the first coat has the effect of forcing epoxy down into the pinholes....after which you can simply work a dry foam roller over the wet epoxy. The roller leaves a level finish much like orange peel, no ridges. If you want to add more thickness, wait until the epoxy gels, then roll on a second coat. Roll a third later, if desired.

Don't use 80 grit to sand the epoxy coat(s). All 80 grit shaping and leveling should be done before epoxy sealing. For that, use 120 or 180, and sand just until the orange peel disappears. It is a great sanding guide.
 
Thanks to all for the input

Dan,
I missed the credit card / roller sequence in previous posts. I assumed the ridges need sanding and the roller application was a separate step.

Randy,
Smooth prime sounds like a good option also.

David,
I have a cheap HF gun that i assume solvent would clean good enough for this application. Maybe not.
 
Last edited:
Larry, the cheapest vinegar is a decent solvent for epoxy. Acetone would also work and probably other solvents like MEK. I use vinegar - but I don't spray the stuff.

Also, if you're trying to thin the epoxy, don't use the vinegar. It's a good cleaner but I'm pretty sure it's not good for the epoxy. I think I remember that 5% acetone by weight is allowed but you should check that.

Dave
 
You can spray 105 as much as any other epoxy. Dilute with acetone or other similar solution. 20-30% by weight should be enough depending on your spray gun and painting experience. I used to produce dozens of widsurf boards decades ago. We routinely sprayed epoxy gelcoat into moulds or sprayed above ready product. I plan not to paint all plastic parts in my 14 including cowls. Just spray gelcoat then sand and polish. Most of dinghies or even big boats are not painted. Gelcoat easily withstands salty water and UV within years if not decades. Your hangar is much less aggressive. And gelcoat in most cases is just epoxy or polyester and powder dye. I use titanium dioxide for white. About 30% added to clean epoxy by weight is absolutely sprayable. You may need a little bit more acetone then for clean epoxy. Filter before spraying. And don’t forget when you calculate weight of hardener that you add hardener to epoxy not to entire solution.
Even more viscous solution than clean epoxy or gelcoat is still sprayable. I used to add some silica filler like West System 406 to epoxy or epoxy based gelcoat until it stops flowing then a lot of acetone and spray. Ending up with perfect nonskid boat or windsurf deck. Sand it just a little and you find nice matt surface. I recently did entire RV-10 cockpit panels exactly this way.
 
Back
Top