rigging angles

[HansLab]

All,
I did not build the wings of my Mark IV Speedster myself (bought the whole lot as a project) and came only this week to rigging the plane (after a year building).
I noticed before that the former owner placed the left wing strut attach brackets for whatever reason somehow more aft than the right wing ones (about 1/2")...They are perpendicular on the wing, though.

When rigging we managed to get the dehidral for both wings right, however.
But, when folding the wings for the first time - just to see it work ;-))) it appears that the left wingtip is more than 3" higher than the right one.
Curious, because the angle 'fuselage attachpoint - wing/fuselage atttachpoint - strut attach bracket' is not changed by ffolding, is it?
Anyone got a clue?

[Dorsal]

Yes, I had this issue, for me it was the wing angle relative to the fuselage (and a slight washout error). If you are happy with the dihedral and the washout (check check and double check) then the fix is to shorten both struts on the left and (by the same number of turns) lengthen the right.

[Geowitz]

Had the same problem. You can look at the thread below for some explanation. The geometry does change as you fold the wings back if the lower strut attach points are shifted to one side. It effectively lengthens or shortens the strut which changes the dihedral in opposite ways as you fold the wing. If the dihedral is correct with the wings in flying position and the strut attach points at the bottom of the fuse are offset to one side then one wing is lowering 1.5 inches and the other is raising 1.5 inches as you fold um back. Make sense?

http://www.teamkitfox.com/Forums/showthread.php?t=1395&highlight=warp+fuse&page=2

Edit - Sorry, this is hard to explain. Let me try again. The lower strut attach points should be centered in the airframe relative to the upper rear spar attach points where the bolt goes through. Imagine this though - Lets say the lower spar carry through tube is shifted 1/2 inch to the right. You set up the dihedral in flying position of each wing equal to each other with a level. However as you fold the wings back, because the lower strut attach points are shifted to the right, the right wing lowers because the lower strut attach point effectively moves farther away from the wing attach points. The left wing will raise because the lower strut attach point effectively moves closer to the wing attach point. Sorry, this is confusing.

[HighWing]

This is a common issue with jig welded structures – heat warping. It doesn't take much movement at the wing roots to make a big difference at the 15 foot mark. A neighbor who is a managing engineer at Aerojet told me that when they require precise weldments they will bolt the welded structure into a very precise, very massive jig and heat it in a furnace to bring it into perfect alignment. While I was building my first Model IV, the manual called for folding the wing and checking the folded wing alignment and make necessary corrections – this was during the stage before final riveting of the attach brackets. Then due to a builder inquiry that basically asked why folded wing cosmetics should overrule flying attitude wing symmetry, there was a service letter published saying to leave it alone. The only issue might be the clearance over the horizontal stabilizer, specifically with the folded flaperon. The advice then was that if you can live with the folded wing looks and the flaperon clears leave it alone.
If your project was originally delivered in that time frame and the original builder saw that information he may well have built accordingly.

Lowell

[Geowitz]

As Lowel implied, 3 inches isn't bad and you'd be fine to leave well enough alone. My post is more to explain why this is happening, not that you have to fix it. Mine was bad enough - over 6 inches - to warrant remediation.

[Gary]

HansLab
I rigged my model IV for straight flight and it looks just like yours with the wings folded.

[HansLab]

Guys, it has been said a lot, but I'm still and meaningfull repeating:
thank you so much for replying - and above all so quick!
Hard to believe that someone across the world has the same thoughts and fears as I do - it really, really helps a whole lot!!

I will measuring my fuselage with a plumb bob - I didn't do it at first because i thought it has been SkyStar manufactured and therefore faultless..

And I will not worry (about this one) anymore - thanks to you all.
I now will take the task of covering my plane, getting an engine onto it, and rig once more to get it right - or to leave it if I can't.