Control surface skin repair

Maintenance, parts and services related to Cessna 120/140's

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Control surface skin repair

Postby 7147 » Sat Jan 19, 2013 2:37 am

What is the best way to split spot welded trailing edges?

I have a idea but would like to have input from the group.

The skins are hard to come by and I am considering a jig in a press to form them.
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Spot welds

Postby David Jose » Sat Jan 19, 2013 11:02 pm

When we reskinned the elevators several years ago, we needed to salvage the internal components; even though we replaced the spars and skins with new.

Found that a stiff (not the flexible type) 1.5" putty knife with full shank blade,
worked fine when tapped with a small hammer. Sure others may have ideas too.

The reassembly of the salvaged parts and the new spars/skins was obviously done with rivets...at the trailing edges and at the spars.

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Postby norm neuls » Sat Jan 19, 2013 11:13 pm

I learned this technique when many years ago I rebuilt a spotwelded stainless steel amphibian(1936 Fleetwing Seabird). Take a GOOD quality hacksaw blade and break off the ends so it's square on the ends. Then break it in two so you have two pieces about 5 inches long. Grind one end on each side so as to create a thin chisel. Quench in water several times to maintain the hardness of the blade tool. Then slide it between the spotwelded pieces and tap on the spotweld with a small hammer. A small hammer gives you better control than a large one. If the metal starts to tear, rotate the thin chisel and tap on the spotweld from the opposite side. It will take a little practice but pretty effective on relatively thin sheet metal.
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Re: Control surface skin repair

Postby Mike Smith » Sun Jan 20, 2013 9:54 am

7147 wrote:The skins are hard to come by and I am considering a jig in a press to form them.


Karl Anderson at Aircraft Northwest, Bow, Wa. 360-757-1946

This company makes replacement skins for all of the control surfaces on the Cessna 120/140/140A. Excellent quality, and the prices aren't that bad.
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skin replacement

Postby David Jose » Mon Jan 21, 2013 7:35 pm

Agree totally with Mike's above reference to Karl, as THE source for Cessna 120/140 control skins.

The elevator skins we acquired from Karl were beautifully cut, and needed only a slight final edge sanding at the curvature of the trailing edge, after assembly, for a perfect match. Karl is a real gentleman to conduct business with, regarding quality replacement skins.

The new spars came from Univair, and were only about $120 each, at the time...a definite bargain, considering Univair's customary pricing for parts.
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Postby flyingdakota » Tue Jan 22, 2013 9:45 pm

Also since you will need to put rivets back into the skin to hold it back together, Drill the center of the spot weld with a #40 bit before you chisel it, the odds will be in your favor for not splitting or tearing the metal. The only bad thing is that the spot welds don't have the greatest equal spacing. And if you use new skins from Karl you won't be disappointed. I have NEVER had a problem with his skins, I have done 120-140 elevators, rudders and flaps, 150 alierons and flaps and a 182 elevator, They were all spot on.
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