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Russell Duffy wrote:
Greetings,
As I ponder my choices for mounting the single rotor engine, I noticed something that surprised me. 304 stainless is cheaper than 4130 steel. One thing that's always bothered me about steel tube type construction is the concern for rusting inside the tubes, so stainless is appealing. There must be a catch here. Is there a good reason I should use 4130 instead of 304? Either will likely be sized much larger than needed, since I don't have the means to do any proper analysis of the strength. Thanks,
Rusty (Autoflight drive supposed to be shipping next week)
Something Richard Sohn told me, and I soon after found to be VERY true. The HAZ of stainless weldment will rust almost as easily as mild steel if not properly treated. It must either be buffed to the original shine, passivated/pickled, or painted. Since you won't have access to the inside of the tube, going stainless may not get you much.
I've often thought of a tube and fabric fuselage made of stainless would make a lot of sense. Most tube airframes are heavily overbuilt just from a materials availability point of view. That is, one size tube is just barely under the stress limit, so there is no choice but to choose the next larger size which give you an extra 50% margin. Any increase in weight from needing to use larger tubes would be offset by the work and weight saved from not needing to paint it. If there was a way around treating the HAZ zone, it could be a winner of an idea.
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,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |
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