surface rust on an airframe.

[racer956]

I have two sonerai airframes. one with surface rust all over it and one that has been etch primed. What I am looking at is the welds on the etch primed frame do not look as good as the other airframe. I want to use the fuse with the surface rust but dont know how deep it goes. If I sand blast the airframe and etch prime it will it be ok or should I scrap the one with surface rust. Also in aircraft spruce I found a covering kit but they listed different types with different prices. What is the best kit to go with. Thanks for all the help this web sight has been great so far.

 

[eschrom]

Racer,

If it truly is "surface" rust, blast it off and spray primer. I'm not sure where the dividing line between surface rust and nonsurface rust is. Look at it closely for pits and craters and try to gauge how deep they are. Or better yet, post a couple of photos.

As for the sock, make sure you know which model you have and then speak with someone at AS to confirm. The first one they sent me for my stretch was too short. Turned out it was made for the standard II model and someone there thought the stretch and the II were the same thing. They agreed to replace it and I remained a happy customer, but of course there is something to be said for getting it right the first time.

Ed
2LS

 

[oahupilot]

If its surface rust just send the frame off to be powder coated, they will clean it and seal it for you resulting in an excellent corrosion resistant finish. If the frame is not pitted severely its surface rust, better yet post photos.

I recommend that you don't buy a sock from AS as the plane is very easy to cover with the blanket method, also cheaper. I prefer the stewart systems of covering the best since its not hazardous to your health or require mek. You can check out videos explaining the entire fabric process and the use of their product.

http://www.youtube.com/user/stewartsystems

Also you can look at my older writeup on this product

http://www.sonerai.net/CMS/index.php?option=com_jfusion&Itemid=160&jfile=index.php&topic=1017.0

 

[Schmleff]

If I recall, the AC43.13 calls out an acceptable pit depth. I just don't remember what the spec was anymore, sorry.

 

[Bil4381]

I somehow wound up with the wings and fuselage for a Pitts S-1C. The fuselage had been stored indoors since 1974 but the roof leaked, and in some places on the fuselage tubing. The entire fuselage was rust covered and some areas had pitting. It took 6 bags of sand to blast off all the rust, just to inspect it.
Now for the good news. Though they looked bad, the deepest pits were .002" deep. I'll use a finger splice to cover that one area, before the pre-close inspection.
Bill

 

[n3480h1]

Bill, I'm glad for your good fortune, but I'm curious - how does one "somehow" end up with a Pitts S1C? What was the remaining wall thickness after blasting 6 bags of sand at it?

Tom

 

[Bil4381]

Tom
There is a senior local member of the EAA who began his Pitts in 1964 but never finished it. It came time to move so he offered the project to the Chapter. The BOD inspected it and decided to accept and finish it.
Members donated money, time, fuel tanks, instrument the upper wing and in one case an engine.
Itr came time to put names down for the project documents and the CofR and the signing space suddenl;y became vacant. Thus it appear at the end of the day the S-1C will be mine.
I may be doing something right. I was offered a hangar this past Sunday, at the owners cost. .

We measured some new sections of the tubing, then compared those dimensions to the sand blasted sections. In most cases the loss of metal was less than .001". The worst pitts were .002" deep. So... I think the worry about the depth of surface corrosion is more dust than steel.
Bill