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Building Tips and technical articles. => Paint and finishing => Topic started by: Dick Pacini on April 11, 2014, 02:55:30 PM

Title: Primer Protocol
Post by: Dick Pacini on April 11, 2014, 02:55:30 PM

I sprayed the NAPA 540 gray primer on my Coyote fuselage.  Should I sand most of it off, fill dings and respray?

I cannot believe the imperfections the primer showed up.  As pristeen as this kit was, (Umland) and the careful sanding I thought I did,the fuselage has picked up some serious hangar rash.  Ultra light contest balsa apparently will show even fingernail nicks.

Title: Re: Primer Protocol
Post by: Tim Wescott on April 11, 2014, 03:16:52 PM

Primer inside a ding is adding to the appearance of the airplane.

Primer over the whole thing is adding to the weight.

I used to work for my dad, getting car parts ready to take molds from.  We're a picky family.  Add to that the pressure of knowing that any imperfections left behind will be replicated 500 to 1000 times (that's the usual life of a fiberglass mold in the process we used), we inspected things very carefully.

Steel parts will get hanger rash just from being in a room next door to a living human being.  Of course balsa gets it from being touched!

Title: Re: Primer Protocol
Post by: Tim Wescott on April 11, 2014, 03:20:17 PM

That reminds me: if you really want the job to be perfect, before you call it done get a buddy over who has a good hand for feeling imperfections and whose workload isn't going to be burdened every time he notices a flaw.  Get him to fondle and gaze at your new pride and joy all over -- he'll point out all the imperfections that you didn't want to know about, and you can go into another round of paintin' and sandin'.

Or you can just call it good and paint it up -- my response any time someone looks at my work and says "oh, that's perfect" is a strong urge (usually suppressed) to start pointing out all the defects that I know damned well are there.

Title: Re: Primer Protocol
Post by: Dick Pacini on April 11, 2014, 05:45:15 PM

I plan on sanding most of it off, leaving primer in the dips and dings.  Those spots I will hit with Hobbylite, sand and re spray with a dusting of primer.

I just don't remember ever having so many issues in finishing 40 some odd years ago.  Either I was better then or just didn't give a crap. HB~>

Title: Re: Primer Protocol
Post by: john e. holliday on April 12, 2014, 09:52:04 AM

It is amazing how primer will all of a sudden show the imperfections you thought were taken care of with the base coats.  I too am working on an Umland kit, another of several of his I have built.   Trying to get the base redy for the silkspan/poly-span is a lot of work.   Then after getting it all down and then spraying the primer you wonder what happened.