question about the trim shafts in horizonal stabs--

[fairchild1934]

I guess I should know this - but the plans dont show it explicitly----
do the two trim shafts - one lt. and one rt.-- do they fasten together in the center ? The plan seems to show a tubular coupling--- but the plans also say to make TWO trim horns. i would think if they are connected in the center- there would be only one horn--- not two......

If they have to hook together in the center- then alignment could be a problem- so they dont bind---

I f anyone has a good pic of that area-- that might help-------

Tim

[jaredyates]

There are two horns that are bolted back to back. Very similar to the elevator horns.
Screenshot_20250713-212646.png

[fairchild1934]

Thanks Jared---- that helps-----
so it appears that the two shafts have to be exactly aligned with each other.....
Not to that point yet-----

Are building another Bearhawk ? (or is this is the first one during the build... ? )

Tim

[jaredyates]

This is our blue plane from many years ago. The shafts have to be aligned and co-axial or you will get binding. The horns are offset laterally to make room for the elevator cables. You can see aluminum tubes that help accomplish that.

[fairchild1934]

do you remember-- did you leave the bushings for the trim shafts unwelded in the ribs until the stabs were fitted into the fuselage ?
I was thinking of welding the bushings to square sheet metal washers that would float in the ribs- with the rib holes a little oversize.
that way the bushings could be moved into alignment with the other shaft and the square plates welded into the rib..... ( I would weld the bushings and plates together on the bench ahead of time) Can make a jig to keep the plate and bush very close to square while welding.

do you think that would work ?

Tim

[spinningwrench]

The other thing you should be aware of is that as the fabric is tightened it will cause a bit of binding on perfectly aligned shafts. A little drag is actually helpful in the trim system, some have reported a problem however.

[fairchild1934]

I wonder if a lovejoy coupling would be safe to use between them ? Thats the problem it is designed to fix.....

[alaskabearhawk]

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=7248&log=169970&row=48