Filling in rivets?

Discussion in 'Finishing Techniques' started by TXFlyGuy, Apr 24, 2017.

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  1. Apr 24, 2017 #1

    TXFlyGuy

    TXFlyGuy

    TXFlyGuy

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    The paint shop I will use makes a practice of filling in all the rivets before painting. This provides a super smooth surface. Is this something that all paint shops do? They also fill all the seams.

    This shop is a favorite of the RV crowd, and has customers in 37 states and Canada.

    IMG_1718.jpg IMG_1713.jpg
     
  2. Apr 24, 2017 #2

    Victor Bravo

    Victor Bravo

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    There are two opposing schools of thought on this, the "old school" feels that filler is a cop-out to hide poor workmanship, and that since rivets are part of the airplane they have a right to be seen if you are looking at it. The other school of thought is that if you went to all the trouble of flush riveting, they you have a right to have your airplane look like a mirror.

    The only directly relevant issue is weight. If all that filler and 20 coats of Imron paint costs you 5 gallons of fuel, then is it really worth it?

    Then there's the smart-aleck school of thought which says... you wanted an aluminum airplane because of the benefits and traditional values of a metal airplane, and you built a metal airplane, and you will be walking around the fly-ins with that huge RV grin parking next to all the other metal airplanes... so WTF do you want it to look like a composite airplane?

    None of this is commenting on the quality and mechanical integrity of the paint job, it is only addressing the concept of body filler in the rivets.

    Filling the seams, on the other hand, is a very bad idea IMHO. You will never have a flat level surface that reflects the light like a flat mirror, so what is the benefit of carrying that weight around? I would also bet dollars to donuts that there will eventually be hairline cracks through the filler at those seams.

    EDIT: I was referring to overlap seams, not butt-joint seams. A butt-joint seam over the wing spar should be smooth for airflow separation/transition purposes. My comment was against the idea of trying to make an overlap skin seam look flat.
     
    Last edited: Apr 24, 2017
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  3. Apr 24, 2017 #3

    TFF

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    All P-51 wings are filled so with a mustang wing its is what is real. The rest is preference. Fill is weight though.
     
  4. Apr 24, 2017 #4

    BBerson

    BBerson

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    I think filled rivets is a downgrade for EAA judging. Probably work loose over time. I would install VG's :gig:
     
  5. Apr 24, 2017 #5

    choppergirl

    choppergirl

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    I just want to keep water out, and the rivet stem in.
    Because the rivet stem adds some sheer strength.

    Rusty rivets = yuck.
     
  6. Apr 24, 2017 #6

    Victor Bravo

    Victor Bravo

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    He's not talking about rivets that have stems.... :)
     
  7. Apr 25, 2017 #7

    gtae07

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    Be very careful filling rivets on your control surfaces, and balance them after filling and painting. There was an RV-7 that broke up in flight several years ago and the extensive filler present on the rudder may have contributed to a flutter event. Of course, going well over redline probably didn't help either.
     
  8. Apr 25, 2017 #8

    lr27

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    Looking at drag, filling rivets in the first 25-55* percent of chord will reduce drag more than filling other rivets. The first part of the chord, if it's smooth, will have laminar flow, and the longer you preserve that, the less drag you have. Also, the boundary layer gets thicker as you move aft, so it "hides" the rivets more, or so I understand.

    Keep in mind that I'm only an armchair aerodynamicist. It's been a long time since I got into much of the math involved, and never for stuff like Tollmien–Schlichting waves, at the mention of which my eyes glaze over. I'm not sure I even heard of them in my classes.

    *Depends on the airfoil and the accuracy of the airfoil shape. I doubt you're going to get back to 55 percent with metal construction. I suspect much less, though I can't give you a very good number.
     
  9. Apr 25, 2017 #9

    TXFlyGuy

    TXFlyGuy

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    Good to know, thanks.
     
  10. May 3, 2017 #10

    rv7charlie

    rv7charlie

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    As a long standing member of 'the RV Crowd' (member since 1994), I'm really curious who these RV'rs are that are so fond of filling rivets. I can tell you that they are very quiet about it on the RV-related forums & lists. I've personally known of only one that had filled rivets; the one I bought in 1994 & sold in 2001.

    Having said that....The one I bought in '94 was very, very fast for its HP. It easily met Van's performance numbers (quite a few do not), and the only thing unusual about it was the filled rivets. And the only place it was done was the top of the wing. Fuse & wing bottom surfaces were 'normal'.

    If the correct prep is done, and the 'fill' is used (which ain't bondo) it will not come loose and it's unlikely you could tell the difference in weight. This assumes that the sheet metal work was done correctly, and you're not filling dents and 'smileys'. Filling a properly set rivet would mean a ring of filler not much bigger in cross section than the point of a pin. You'd still see the rivet head, until paint goes on.

    I don't know if I'll have the patience, but that's the only thing that would stop me from filling the wings on my -7 when I get to that point. Fill will get you a mark down in judging at OSH, but I have no illusions of winning that competition against the Parker P-51 pilots that win most years. :)

    Charlie
     
  11. May 4, 2017 #11

    gtae07

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    I've seen it in person on a couple of RVs, but mostly I think it was done with lots of high-build primer and a lot of sanding, both done by the paint guy being paid to do it.

    As I mentioned earlier, the only documented case I know of is the in-flight breakup described in the Canadian TSB report A10O0018.

     

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