Panther Sport Aircraft Forums

The skins and steel Longerons are the structure of the forward fuselage. Welding tabs or other means of securing the skins is unacceptable. The tube structure does not have diagonals , the skins carry the diagonal stress (as in any stressed skin structure). A better idea for sealing the tubes is to dip each rivet in Proseal before pulling it.


Rachel

Has anyone considered a different way to attach the fuselage skins other than drilling into the fuselage tubes? Maybe a welded tab along the tubes instead ? It adds a little weight but the tubes would remain sealed and you don't have to put holes in the structural bits....


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That's an easy one. Just change Tubeseal to boiled linseed oil. What's the Milspec on that?

Tony

FYI,

I looked up the Mil spec listed on the Polyfiber website for Tubeseal, and it is listed as a preservation oil for break in of internal combustion engines. Since it says fine, the lightest oil in the spec is SAE-10W which I believe is commonly known as 1010 oil in the Navy. We use it to preserve fuel systems and fuel tanks in the Navy, any time there is no fuel in the aircraft for at least 2 weeks.

Basically, I believe tubeseal is a light motor oil with possibly some additional additives not listed. I think they listed the mil-spec to make it sound high tech.

Paul

Glen,

All the tubes that have skin attached to them will have holes. Before the last rivet goes in a tube, give it a shot of Tubeseal. Drill, squirt, then plug interior tubes. Doesn't seem to me that just rolling would do a good job of spreading the liquid. Needs to be rotated in both pitch and roll. Have a look at 3:55 to see what that looks like:

http://www.youtube.com/watch?v=3TuYBMvByEo

Tony

Thanks Tony,

That's the information I was looking for. I didn't know how the cross members and uprights would be treated after the fuselage was welded. I figured internal holes had to be drilled between the welded together tubes and the oil would have to work its way around the structure. Drilling a small hole from the outside and treating each piece makes a lot more sense.

Glen

Glen,

Here's something for you to read: http://www.polyfiber.com/products/tubes ... ibitor.htm

It would be very easy for you to drill the recommended holes after receiving your cage. Looks like I now have a use for the 1000 AD-41H closed-end rivets I bought for the fuel tanks which ended up being too short. Dan has indicated that SS rivets are to be used to attach the aluminum skin to the 4130 tubes. SS rivets are available with a closed end, but only domed, not flush.

Don't recall having heard of any engine mount manufacturers that use tubeseal, nor any builders that have bothered to use the product.

Tony

Glen,

I will most likely use some oil in the fuselage. As Dan said, there are literally a thousand holes, and the fuselage is light enough for one person to roll around to coat the internals.

Paul

Glen,

Please go back and read the second post in this thread. Maybe you missed this: "you can certainly treat with linseed oil and we can give you some tips for doing that". Seems pretty clear.

Tony

Paul,

Laser cutting, of course shouldn't have anything to do with corrosion control. I only included that, because I was quoting the author's sentence. I don't know how SPA cuts their steel, but I'm sure they have an acceptable way of doing so. The exterior powder coating of the steel fuselage should prove durable and long lasting. My concern is corrosion of the un-coated, internal steel fuselage. I'm confused as to why you are going to great lengths to corrosion protect your wings (made with 6061 aluminum), but you don't seem to be concerned about internal corrosion of your fuselage tubing.
The Great Lakes people pulled apart one airplane and found "big corrosion problems with the steel tube fuselage". Maybe this airplane was the only one with a problem. Maybe others have worse problems. I think it's still a common practice to oil the interior of a steel tube fuselages.

Glen