JKEpps

My Feedback: (1)

OK, at the risk of this sounding like a dumb question, here goes. What is the purpose of primer in prepping a plane for paint. I have a plane that I covered using fiberglass and ZPoxy finishing resin. I sprayed the entire fuse, stab and fin with primer (Rustoleum rattle-can). This is a practice piece for me (my trainer, Bud Nosen 8 1/2 ft span trainer) so I'm looking to learn, not necessarily have a perfect finish with this one. So basically, my question is, do I sand off nearly all of the primer, looking for surface imperfections to fix, prime again, sand, inspect, rinse, wash, repeat until satisfied. Or, do I do all of the surface imperfections prior to priming, then lay down a coat of primer on the entire plane, sand smooth enough to paint, then paint. Or is there some combination of both.

Thanks in advance.

Jorden

daven

My Feedback: (1)

So basically, my question is, do I sand off nearly all of the primer, looking for surface imperfections to fix, prime again, sand, inspect, rinse, wash, repeat until satisfied.

YES

Ed Smith

There is a lesson to be learned here.

The next layer of whatever is being put on the airplane will never improve the previous layer. So. rather than wait until the prime stage do to all the fixing, pay attention to detail at the balsa/covering stage. Then the same at the glassing stage. Ideally one coat of primer, sanded, should do it.

I learned this lesson making molds. If the plug was so, so, then the mold made from it was horrible.

Ed S

DHG

My Feedback: (7)

Jorden,

IMHO, the best thing about primer is that it gives the surface a uniform color so you can see the dimples & bumps. You should not need to put a thick layer of primer on anything except unfilled fiberglass weave -- and even then, you'd have been better off to fill the weave with clear resin, nitrate dope, Minwax Polycrylic, etc., before spraying the primer on it. Primer fills well, but it's also darn heavy.

As Ed suggests, I try to get my airplanes as perfect as I can without primer, then spray a thin coat of primer and take it out in the sunshine to look for low spots. These I fill with putty (see below). Then I sand everything with drywall screen until most of the primer is gone, and move on to the base coat. If you really want a show finish and weight isn't a big issue, spray a second coat of primer and sand lightly or not at all.

Putty recommendations, depending on the type of low spot and how much "stink" you can handle:

1. Pinholes in fiberglass, dry areas of glass weave: Vinyl spackling paste (harware store) -- rub into pinholes with a damp piece of old T-shirt.
2. Dents & gouges, small fillets: Bondo Glazing & Spot Putty (auto parts store) or Glaze Coat by Evercoat (paint store, auto parts store).
3. Large fillets, gaps: Epoxy resin mixed with micro-balloons, baby powder, or cornstarch until very stiff (like cake icing), thinned slightly with lacquer thinner if necessary. If it refuses to stick, prime the area to be filled using a very thin coat of pure resin.

Remember the rubber gloves & a mask for the stinky stuff. Good luck!

Duane Gall
RCPRO

hoofty

As stated above, you would be far better off trying to get a good finish without relying on primer to fill imperfections. My personal choice for filling the weave is bondo (it cures fast, sands easily, and is only slightly heavier than splackling putty) the best way to get a good finish is to vacuum bag the parts while glassing them. this method removed all excess resin and compresses the fibers to a uniform thickness where there should be little or no filling nessisary. but this only works on structures with a solid core (like foam core wings and tail feathers). don't try to bag built up balsa, you will end up with just that, a bag full of balsa(only it wont look like a plane anymore.

Hoofty

JKEpps

My Feedback: (1)

Thanks for the info guys. That really helps. I see I have a lot of sanding to do to get the primer off. I had done the bulk of surface prep, i.e. dents, ding, bumps, lumps, etc... before I sprayed the primer, so I think I'm in good shape there. As this plane had been previously covered with Oracote, (before the crash repair) so it was already in pretty good shape. I'll let you know how it goes.

Dave (KlassKote), was it you I met at Toledo this year? I was the Redskins fan who was looking to match the Skins colors.

Jorden