Internal Frame Rail Rot

[drcomanche]

As the title says, I just discovered this on my truck today. How do I fix this problem? Can I fix it?

[flint54]

Probably not. Can you describe it? Are there holes?

Can you poke your finger through it? Is the inside

full of flakes? What can you see? How much of the

frame do you think is affected? The only thing that

comes to mind is to spray chemicals to slow down the

deterioration. Suggest you rig up the ability to spray

through a tube, and then see how far in you can insert

the tube. The first item I would spray is Ospho, to

convert the oxide surface to phosphate. Then, there's

a product we have had good success with on aircraft

called Dinitrol AV-30. It's a CPC (corrosion preventive

compound) with good wicking ability. These two

actions will slow down the harm, but will not fix it.

BTW, the AV-30 can be sprayed with a wand from a

small pressure pot.

[jimoshel]

If it's already rusted then this is of no help. and it may not be of any help even if it isn't rusted yet. Just throwing it out there for what it's worth. In homebuilt aircraft, and some commercial applications when building a airframe, or repairing a frame a small hole is left, or drilled in one end of the frame. The frame is mounted on two spits, one on each end of the frame. Linseed oil is poured into the frame until it's full or kind a full. The frame is now rotated until the linseed oil has had a chance to coat every inch of the frame interior. The oil is now drained and the hole sealed. I have only seen one frame that rusted using this method and that was on a crop duster with a leaking chemical tank and then it rusted from the outside in. I did this on a '62 Corvair convertible I was restoring. I only had the car for a couple more years so really can't say how long it prevented rust, but then I mainly did it just to be doing it, kind of just proving it could be done. Didn't have rust problems with wooden airframes.

On a Comanche with frame rust I would cut out all the rust and literally build a new frame. Once rust has started your not going to stop it. Just remove it and repair as necessary.