Question Time!

[Miraj]

OK, Q & A time for you building gurus.
I 've just started on a Sagitta XC, yipeee! The ribs are done and now its time to choose either carbon square tubing, carbon round tubing, brass round tubing or brass square tubing for the wing joiner system.
What are your thoughts?

[rdwoebke]

Hey Miraj,

I'm building a Sagitta XC too. Have been since 2003. :)

I could be wrong, but I think the brass tubing is fine for the wing joiner housings. Now the diameter/length of the joiners themselves on the Sagitta XC, that could be a question to debate (aka, improving it somehow).

Ryan

[rdeis]

The composites thread(s) seemed to show very clearly that squares are preferred over round for strength, but that they may be impractical in many cases.

The joiner system has at least three distinct parts that are important:
1> The rod or pin that carries the load from one spar to the other
2> The tube within each wing that house the rod
3> The joint (as it were) that tranfsers the load from the rod housings to the spars.

I'd guess that (2) is the least important, and brass in whatever shape best fits (1) would do fine, so long as it was well epoxied to the spar and the spar was wrapped properly to carry the load from (3).

Carbon square tube is certain to have the best strength/weight for the job in (1), but is an awful lot more expensive than a simple steel or aluminum rod and it's not clear to me how much the weight savings matters on the big Sagitta.

Carbon tube will also be stiffer than metal, I think, and so won't flex before breaking under severe launch loads. That always leads me to choose metal pins instead of carbon.

[Curare]

I'm much the same, I went for steel in my sagitta, mainly because I didn't really like the idea of snapping a carbon spar, at least the steel will yield before it goes to peices, you can land a bent plane, but not one that's in 3 peices. (thinks back to the stepp 3)

Miraj, my sagitta 600 has stopped (not that it really began I got suckered into making a DLG) but now I have a more pressing project to deal with.

http://image2-0.rcuniverse.com/e1/forum/upfiles/79454/Fd92560.jpg

[lincoln]

Square is stronger if you know orientation of stress. If not, round is better. Is design stress JUST launch load and not dork load? Dork load might not be straight fore and aft.

[Miraj]

Sounds like the round maybe it, Brass and steel! I like the bend rather than break and can save weight in other areas.
Cheers for the input!!
Miraj, my sagitta 600 has stopped (not that it really began I got suckered into making a DLG) but now I have a more pressing project to deal with.
Sounds like me, my Blanik has taken a back seat for a month or two. lol
Never mind, we will get back to them one day!!

M

[Curare]

Too many planes, not enough lifetimes mate:)

[Miraj]

So true, I went out yesterday and spent $100 on hardware for the sagitta. I have everything now to get it done. I've given myself to October 1 to have it complete, should be enough time to do a plane that size?
M