MONTY THE ANSWER MAN... ALUMINIMUM WRINKLES
IF YOU'RE OVER 50
YEARS OLD, YOU'RE BOUND TO HAVE A FEW WRINKLES...
From: Bob Runge (firstname.lastname@example.org)
Attached is a photo of my Swift. Notice the dimples in the skin at this
angle of light. Can't say I can feel them, just see them. What do you
think caused this and what might I be able to do about it? Thanks Jim
and have a good day.
I presume you mean the waves in the skin visible from the cockpit aft.
Your a/c is s/n 31. Some early Swifts had light skin on the fuselage.
I would guess yours is .020. My first Swift was s/n 42 and had the same
thing, except the factory had installed a vertical stiffener angle in
each bay. It was still kind of wavy. Later, I owned s/n 26 which had heavier
guage aluminum, .025 for the side sheets. It didn't have any waves in
it. Evidently Globe was aware of the fact that their little Swift was
a little heavy for 85 hp. Skin thickness varies on various s/n Swifts.
I have seen late s/n's with .032 for most of the fuselage. It doesn't
do much good to save a few ounces on skin guage, then put a 15 lb block
of lead in the tail! Cessna uses .016 and .020 a lot in their airplanes.
The Boeing 747 elevator end rib has .016 skin! I don't think there is
much you can do about the situation, short of reskinning your fuselage
with heavier guage aluminum. I sold s/n 42 and bought a later Swift! Mark
Holliday is restoring s/n 76, the skin didn't polish up to his standards,
so he drilled it off and changed it! -- Jim
GETTING RID OF THOSE
Has anyone actually tried the procedure on p.27 of the blue Swift Maint.
and Ops info book to remove wrinkles in the fuselage skin? It seems a
bit far fetched to me. Thanks. Keith Bracht <email@example.com>
I've tried it, with varying degrees of success. If the airplane is more-or-less
hanging from the lifting eye on the engine (most of the weight between
the engine and the tailwheel) and the rivets in the row below the windshield
are removed, some skin wrinkles may come out. Then replace those rivets,
being sure to use 1/8". (some airplanes had 3/32" rivets from the factory)
Sometimes you can slip in an extra STEEL washer at the spacers in the
belly. The forward fuselage skins are usually .025, I like to replace
them with .032 (the side skins behind the firewall) If the spar web has
wrinkles I had a factory letter on installing stiffeners. (requires fuel
tank removal) Good luck! -- Jim Montague
From: Allan Erickson <firstname.lastname@example.org>
We are preparing to attach the engine to the firewall. Was looking at
the wrinkles on the side of the fuselage. Tried to eliminate them years
age as the blue book described, but did not have much luck. Do you have
any other suggestions? -- Allan Erickson
If those are the original skins, the forward section is only .025. The
best solution is to reskin that piece with .032. I didn't say easiest!
I just finished one of those this weekend and it is not too bad, except
a couple of rivets at the fwd top corner. Having said that, if your skins
are otherwise OK and have no venturi holes or other bad stuff they can
be straightened. If your engine is off this is the ideal time to do this.
Or hoist the engine and see if the wrinkles come out. If they do, bend
up a couple of .025 or .032 angles to bridge the area between the formers.
Locate them so they push the wrinkles out. Drill out one rivet in each
former to hold the angle in place. A shim can be slid in behind the angles
to help. Release the hoist and make sure the wrinkle stays out. Shoot
the one rivet back in, capturing the new angle. No additional rivets need
to be installed, so it won't look bad. Structural adhesive can be used
to further hold the angle and any shims. Sometimes, with the engine lifted,
a rivet row can be drilled out and reshot to eliminate stress wrinkles.
The aft row in the forward skin should be 1/8" rivets. A few airplanes
left Globe with 3/32" rivets in this seam. I think all of these have
been replaced by now, but you never know! If I can clarify or elaborate,
let me know. -- Jim
IF YOU WERE ALMOST 60 YEARS OLD YOU’D HAVE WRINKLES TOO! (FEB 04)
From: Jim Salmonsen <Topgunn62@aol.com>
Subject: Re: Question on a Swift.............
I was talking to a fellow who is interesed in my 172 for sale,says he
knew a little about Swifts,and advised the Earlier Swift Models had "thinner
skins" that were known to" wrinkle",any truth to this?
Do you have a/any favorite year(s)? ( You must be starting to look for
my questions each night, aren`t you?) As always,THANKS.........Jim Salmonsen
The first 100 GC-1As varied a bit as Globe tried to get it "right".Some
early GC-1As only used .020 skin for the main sheets of the aft fuselage.
Other early airplanes used .025 skin for the same areas. Real late s/n's
used .032 for the aft fuselage. I would say the .025 was about right.
I think .032 was overkill. I suppose their thinking was "why save
a few ounces on skin weight, then bolt a 9 lb block of lead in the tail"
for CG?" The early airplanes used 15 pounds of lead ballast with
a 125 installed. My s/n 42 had the light skin and it had wrinkles in it.
But so what? They didn't really hurt anything. Later on, I owned s/n 26
and it had heavier skin The GC-1As had .050 stabilizer spars, where the
later airplanes used .063. This has not been a problem. The early wing/fuselage
joint is superior than the later setup. Overall, not much to worry about.
See "Aluminum Wrinkles" in the "Answer Man Archive."