Flying wire options

[schu]

It's just the links according to plans with some 7/16x.120 tubing welded into place. It's easy to make and super strong. It's pretty much .120 all the way around so I think a AN665 would certainly be lighter, but a bit more expansive and possibly more draggy, hard to say. I'll probably use an AN665 on one end and MS20667-5 on the other since it will look a bit nicer, and I can build the wires with 1x9 cable for about $200.

Hope that helps.

[schu]

Using the above with some thick welds and shaping would yield something fairly streamlined. Combined with the streamlined wires would probably be a bit less drag than 6 AN665 forks with pins. (Probably still use 2 on the bottom to mate with the tabs welded to the lower longeron.)

[schu]

Here is my prototype. Looks super strong and super cheap. I bet Bob would be proud.

[Mark Goldberg]

Schu - on the LSA Bob originally had us supply end fittings made from tubing instead of AN665's. They were really STRONG. But after vibration broke the same tailwire on my plane twice (in the same place but months apart) then Bob decided that vibration fatigue from very rigid end fittings was causing this. So we went to the same kind of end tabs and fittings used on the others.

Now the wires are your plane are 1/4" and not the 3/16" like the LSA. But I would be concerned about the same thing. You should keep a good eye on them. A preflight close inspection at the least. Sometimes too strong is not desirable. Mark

[Chris In Milwaukee]

You mentioned wire earlier in this thread. Still using it? Or is that solid all the way up? I like the fitting!

[schu]

I'm using 5/32 wire just like Bob recommends. I don't expect to have any problems. The part that is most prone to vibration is .125 3/4 wide strip of 4130 just like every other airplane. All I changed was the threaded part.

[whee]

I like the concept of what schu has done but I'd be very careful about how it is implemented and I'd talk to Bob or someone equally knowledgeable in these kinds of structures.

The flying wires live in a high stress environment subject to constant tension and vibration...the perfect recipe for fatigue failure. Weld imperfections and cut threads (rather than rolled threads) are the perfect places for cracks to propagate from. This change is a major change.

I'm not saying schu didn't do it right, I just want everybody to be safe.

[schu]

schu - on the LSA Bob originally had us supply end fittings made from tubing instead of AN665's. They were really STRONG. But after vibration broke the same tailwire on my plane twice (in the same place but months apart) then Bob decided that vibration fatigue from very rigid end fittings was causing this. So we went to the same kind of end tabs and fittings used on the others.

Mark, please tell me about the fittings Bob had you supply? Did you take tubing, squash one side, bend, then tap like this:



Where did they break? On the bend, next to the bolt?

If that's the case, then I'm not really concerned, the fitting above is WAY more rigid than what I did. My part uses the same 3/4 x .125 strip at the bend as any other link used on all of the flying airplanes, only the threads change.

One thing to keep in mind is that the fatigue from vibration has a lot to do with the harmonics, and that any change in the system could have eliminated the failures.

[Mark Goldberg]

Schu - if you would like to call me and discuss that would be fine. Mark

[schu]

Whee, I did talk to Bob, he said it was fine....