[MrNomad]

Given that this is our second RV building project and we’re talking about a third, I decided to experiment and figure out which method of filling pinholes gets the fiberglass sections of the airplane ready for paint with the least effort and lowest cost.

Method 1: According to Van’s, mix 1 part WEST to 1 part Acetone. Squeegee it on, sand it smooth. After 2 coats of $200 per gallon primer (good stuff), it was ready for paint.

Method 2: Using $200 per gallon primer, give the piece 2 coats, and squeegee the second coat. This method filled the pinholes but the primer will require sanding and (given that I am a perfectionist) it will need another coat of primer.

Method 3: Using $200 per gallon primer, give the piece 2 coats. This method left many pinholes. The fiberglass piece will need more work and another coat of primer.

Method 1 was the least expensive, and most productive. Sanding WEST is more difficult that sanding primer, but you get to paint status fastest via Method 1.

Your results may differ. No flaming please!

 

[LettersFromFlyoverCountry]

What's the $200 a gallon primer?

 

[MrNomad]

Product we used

DUPONT NASON? SELECTPRIME? 421-17 2K URETHANE PRIMER & ACTIVATOR, TAX was about $200 per gal.

Good adhesion, nice finish. It's held up quite well on other projects.

 

[SHORTRV7]

epoxy/acetone cure

Barry, I couldn' t get the one part epoxy/one part acetone to cure hard enough to sand even after 4 to 5 days, did yours cure out completly?
Don

 

[Pmerems]

About $150/gal

DUPONT NASON® SELECTPRIME™ 421-17 2K URETHANE PRIMER & ACTIVATOR, TAX was about $200 per gal.

Barry,

I bought the same stuff from the same place you did and I only paid around $150 for the primer and activator.

A few folks recommended Metal Glaze as a pin hole filler. I costs ~$35/quart. This is a polyester product but adheres to many surfaces great. It really sticks to your fingers and almost impossible to remove once cured (don't ask me how I know, now I wear latex gloves). It dries rather quickly, no shrinkage and is relatively easy to sand. I squeegeed it all over the cowl to fill the wave. Then sanded. Shot a thin coat of primer (due to bad weather that shortened my primer session) and sanded. Put on a second coat and it is 95-98% perfect. The remaining defects will be taken care of prior to the application of paint (By a professional paint shop).

I used the same process on the wheel pants that had thousands of pinholes. Used some of the primer with my fingers to fill the tiny pin holes the Metal Glaze didn't, then shot two coats of primer. Worked out well.

Keep in mind I didn't use the Metal Glaze to build up any surface, just for filling minor weave.

If I had to do it again I wouldn't hesitate to use these products again.

No matter how you spin it there sure is a lot of fitting, filling and sanding to make these fiberglass parts look great.

 

[MrNomad]

Answers to two posts....

Method 1 - WEST must always be mixed with hardener in the proper ratio, then cut with acetone on a 1 - 1 ratio. If you don't add hardener, it will never cure. The piece I did with this method was hard in 1 day and sanded OK. Admittedly, sanding WEST is tougher than sanding primer but using Norton 80 grit paper and a fairly rigid block, it came out smooth. This method was suggested by Vans in my 9A manual.

My friend Paul Merems used Metal Glaze which is a great product (especially in comparison to lacquer based fillers). Metal Glaze will fill holes and sands easier than Method 1, and I've used Metal Glaze on many car projects and the airplane too. However, it's expensive and much more time consuming than "squeegee-ing" WEST (with the appropriate hardener and acetone) or "squeegee-ing" a quality primer. But Metal Glaze will definitely work.

One final suggestion. If you decide to use Metal Glaze or any other filler, never mix on a cardboard or wood surface. Use a piece of glass or a glazed floor tile so that the filler does not soak into the mixing surface or pick up anything from the mixing surface. After every mix of filler, I clean my glass mixing surface and applicators with cheap laq thinner. Yes, always wear gloves and try not to breathe the vapors.

Mixing WEST is even easier. My wife buys butter spread in those little plastic cups. After cleaning, the little plastic cups work great for WEST.

A big mistake I made ONE TIME was to NOT wear a quality mask when sanding WEST and fiberglass (or any filler, for that matter). For $15, you can buy a quality mask with replaceable filters. Please don't inhale the dust that comes off of these products. Filters & gloves are much cheaper than chemo (sic)!