Prepping a Polyester Hull

[Terry Heddin]

Update, Not polyester, it's epoxy.
What's the best way to prep an older, (early '80s) polyester glass hull to avoid pin holes? I have read that you should not sand before primer, but I don't think the primer would hold up without a pre-sand.
Several years go, I built a giant scale P-39 Aircobra with a polyester glass fuselage, and I fought pin holes for weeks.

 

[Mark Anderson]

Wet sand it to remove the gloss. If you break through pinholes, they likely would have broken at some point anyway. I brush my first coat of primer on which forces primer into the pinholes. Many people spray it and as pin holes are seen use a gloved finger to wipe primer into them.

 

[FloridaScaleBoater]

What's the best way to prep an older, (early '80s) polyester glass hull to avoid pin holes? I have read that you should not sand before primer, but I don't think the primer would hold up without a pre-sand.
Several years go, I built a giant scale P-39 Aircobra with a polyester glass fuselage, and I fought pin holes for weeks.

Are you sure that's a polyester hull?
Sure looks like epoxy to me?

 

[Terry Heddin]

Are you sure that's a polyester hull?
Sure looks like epoxy to me?

I stand corrected, just looked at copies of the review of the kit, 1984 Flying Models mag, and it states it's epoxy

 

[Mark Anderson]

Same procedure.

 

[P THOMAS]

FINISHING EPOXY GLASS PARTS


Epoxy glass parts will get tiny pin holes or small air bubbles due to the air trapped in the epoxy surface coat. We try to keep this to a minimum but you will find some on your parts.
The best way to finish the epoxy parts is to start by dulling the surface of the hull and cowl with a green finishing pad or 150 grit paper, do not sand into the glass cloth, this will cause more pin holes. Inspect the part for pin holes, use a sharp pointed knife to open any pinholes you can find. Use a red glazing putty to fill any voids or pinholes
Spackling paste used for wall board is good for filling pinholes.
Apply light weight filler with a spreader. Fill all pin holes with the spackling remove any excess and let this dry for 2-4 hours. Lightly dry sand the parts with a red finishing pad.

Give the hull a coat of primer and check for additional pin holes and apply a second coat of spackling.
Sand the final coat of spackling and apply a coat of primer.

For gas/nitro fuel boats use Klass Koat epoxy primer and paint or polyurethane paints.

Rustoleum 2X primers and paints work well for Gas or Electric power boats.
Apply at least 3 light coats of 2 part clear to ensure your paint job will be fuel proof.

I like the Klasskoat white primer, fills pinholes and sands easy. Klass koat colors are easy to use too. 1-1 part mix

 

[Roxyflash]

Be careful if you use red spot putty don’t put it on thick if you do it shrinks and cracks lite applications and let it dry overnite.Sand it with 220.Do that till you think you have all pin holes filled then prime if using rattle can primer make sure you get the automotive sandable kind.Dont spray it on thick or it will shrink and crack.

 

[frankpulte]

Go to Bob Violett models web sight, look under finishing products, look for pin hole filler. You apply like a past wax, let dry buff off and prime. Works great have been using for years.

 

[Timbo Whalen]

https://dreamworksrc.com/product/pinhole-filler/