Warbird Information Exchange

Need some advise on putting the tube seal oil into the NA-64 tubular frame via the small screw hole in the upper Left rear tube. The manual is talking about spraying the warm oil in at around 30 p.s.i. How much oil is actually needed? Is there any tricks to doing this?



Patrick

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Hot linseed oil was used inside tubing way back when they were built. The procedure was to fill the tube at the lower end until it flowed out of the top and then let it drain out. After it drained the drive screw was put in each end to seal it up. It is important that air/moisture is not allowed to enter the tubing.

Many say that a better product is available today like tube seal or other products. I have worked with a lot of Beech 18 spars and those that had been sealed look just as nice as they did 70 years ago. Those tubes that were exposed to the elements inside will rust like any other steel structure.

I know the original linseed oil seems to work for 70+ years if properly maintained but I can't vouch for more modern products.

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Patrick: Bolt a couple of 4x4's to the engine mount lugs and stand the tubing on them. Make you a drip feeder out of some 2" pvc and appropriate fittings. Plumb that to the tube fitting via some Tygon type clear tubing. Pour the drip tube about 3/4 full of linseed oil and let it drain into the tube structure. Repeat til the structure won't take any more, cap the feed hole and lay the structure flat. Rotate 90 deg after a half hour or so, repeating until you've rotated through all 4 sides. Now hang the tubing from the motor end and drain all the oil out. When it quits draining, lay it down with the drain fitting at the bottom for a couple of hours. Rehang it and repeat until you get nothing but a few drips out of the hole. At this point, you can remove your feed fitting and plug the hole.

Just remember about using linseed oil, that it is HIGHLY FLAMMABLE AND CAN AND WILL PROBABLY SPONTANOUSLY COMBUST when rags coated in it are stored in closed cans. Treat the used rags and oil as ready to burn the instant you turn your eyes off of it. Properly dispose of the leftovers and rags. Having said that, It's not hard to use, just a little messy and time consuming to do. I did my L-5 fuselage, and it took me about two days to do and I used about 4 gallons and recovered all but about 10 ounces between what stayed in the tubes and what was spilled.

The beauty of using heated linseed oil is you can feel the tubes heat up as the oil passes through. This will ensure that you don't miss any, as it does take a little while to trickle through some of the small interconnecting holes.