Keep Checking Tail Strut Threads

[Battson]

How you you guys have your strut rigged? IE, during preflight is the strut in tension, compression or neutral? I wiggle my h-stab and strut during preflight and the tiny bit of slop I feel in the strut makes me wonder if I should rig it differently. Currently I have it rigged neutral.

That will allow for more and slightly larger stress cycles, at full power especially. I suggest taking a turn off each side to put a little pre-load on the fittings.

[whee]

That will allow for more and slightly larger stress cycles, at full power especially. I suggest taking a turn off each side to put a little pre-load on the fittings.

Preload in which direction; compression and tension? I think they should be preloaded in compression but I wanted to know what others had done.

[Battson]

They are loaded in compression in cruise flight, so that is the way to load them. Fewer stress cycles doing in that way. However it will depend on the build, some people may end up with compression on side and tension the other, that is no problem.

[alaskabearhawk]

My H stab struts have a bolt in each end, no adjustment. I thought the later addition of adjustment at the bottom of the strut was to make fabrication easier, not to make adjustments. No?

[Battson]

My H stab struts have a bolt in each end, no adjustment. I thought the later addition of adjustment at the bottom of the strut was to make fabrication easier, not to make adjustments. No?

If they are perfect without requiring any adjustment, then you hit the jackpot. Refer to the thread on rigging Bearhawks to understand why they need to be exactly right.

[Nev]

Jon could you add a link to this thread - thanks.

[alaskabearhawk]

I really am missing something here. The plans (#708) are unambiguous. H stab straight using a laser level, weld the struts. The only adjustment possible before the strut is welded is where the forward H stab spar attaches to the fuselage. My plans say negative 4 degrees for a flat (non-airfoil) H stab setting. I put an airfoil shape in my H stab and it generates more down thrust. Per Bob’s recommendation I went to a negative 2 degrees. There is no other adjustment available to me.

[Mark Goldberg]

Paul, we do it a little differently on the kit hor stab struts. On the bottom we weld in a AN490 and thread on an AN665-34. That way there is some adjustment. Not a ton, but enough to adjust the outboard side of the hor stabs.

You might find that 2 degrees down is not enough and you need 3 degrees to get good elevator authority. Time will tell when you fly. Mark

[alaskabearhawk]

I just double-checked my build log. I did make the incidence a neg 3 degrees after having talked with Bob about it. Hopefully that will be good. I do have a couple of the rod ends you described, got them from Jared last year. So, in case any changes have to be made I have what I need.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=7248&log=166979&row=78

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=7248&log=167621&row=71

[geraldmorrissey]

This string is an eye opener. I would rather build solid bolt on struts, fly them and if necessary build additional struts until it is dialed in. In the grand scheme of things, steel is cheap.

[Mark Goldberg]

Gerald, the above discussion is about the 4 place. On the Patrols - the bottom is pinned in place and on the top we use an AN5 bolt with the head cut off and forged. They cut a few more threads with a die. Has worked well. Mark

[geraldmorrissey]

Mark, your confidence in the Patrol design difference is reassuring. I'm not as confident I can build the hardware.