Rigging jury struts

[carlisle]

As I understand it, jury struts' purpose is to prevent bending/buckling of the main strut during negative G conditions. Thus the jury strut should be perpendicular to the spar or it's tendency would be to buckle too under high negative G loads. When all was said/done with my Model 2 kit, I also had a little angle to the jury struts when installed per the manual. The angle was < 1.5 deg though and the simple clamp style fittings that attach the jury to the main were easily adjusted. This puts the jury maybe an inch or so further out the span of the main but preserves it's perpendicular orientation.

Chris

[jtpitkin06]

It sounds like this is a minor alignment problem. I’ll just make a longer set of brackets at the front where the jury strut connects to the forward spar.


This will accomplish two things:


I’ll get the jury strut alignment into the slipstream which probably won’t make a bit of difference in drag but makes me think I did a better job; and,
The forward attach bolt will not be buried halfway in the fabric covering.


One thing I have to say is how impressed I am with the kit. I got this far without a major snag in construction and this is only a minor detail. Sure, I had a couple of oops along the way like cutting a trailing edge piece on the wrong side of the line. But, so far, I haven’t run into anything that couldn’t be corrected. Great kit!
JP

[jtpitkin06]

Well, it turns out I don’t need longer jury strut brackets.



I made a short phone call to John McBean at Kitfox LLC to ask about fitting the jury struts. He was very helpful in telling me my situation was not normal. We agreed I needed to look for the cause. While not able to diagnose over the phone he did give me some tips on where to look. I have to say the Kitfox customer support is terrific.


Per the assembly manual, I used a taut string to ensure the forward lift strut was not sagging; but the jury strut was still low by 1/4 inch. Shifting the front of the jury strut outboard to raise it up put the fore and aft alignment off by one inch. Not ideal in my book.


With some clues from my conversation with John, I checked the rear lift strut and found it had a warp in the upward direction. That was totally unexpected. I had assumed it would be sagging from gravity.
I gave a quick tweak to the rear lift strut to remove the upward warp and everything came into place.


While some may find this episode a bit boring, I pass this information on as a reminder. When you get stuck, keep asking questions. Try different sources. Keep searching. And feedback, no matter how small, is a big help.


And lastly… if something doesn’t seem quite right, it probably isn’t.
Net result here is: The problem is resolved and I get to move forward.

John Pitkin
Greenville, TX

[carlisle]

Good job John. An engineer's perspective for sure and while I can't always claim I'm as persistent about such problems and sometimes compromise where I shouldn't, reading someone elses success stories helps to keep me motivated.

Chris

[Maverick]

Thank you. Did you drill the attachment holes in the top attach brackets before trying to fit the jury strut/brackets to the lift strut brackets? The ones I received do not have a hole drilled to which you would attach the jury strut and it appears to be something that you would determine where to drill it in the fitting process. Same for the bottom brackets, no hole so, do you drill these holes prior to putting them on the lift strut?

[Meyer]

Yes I drilled mine ahead of time. There were dimensions of where they should be, and those brackets are of a size such that you would not want to deviate from the dimensions.

Once it all bolts up loosely it can move around enough to get the geometry right.