Control Stick Assy interference with Wing Spar Tunnel

[RodgerC]

Hello fellow Waiex builders,

Has anybody else encountered interference between their control stick assembly, in particular the AN4 bolts connecting sticks to horns, with the top surface of the spar tunnel?

In my case it is particularly noticeable when the sticks are in the fully deflected left and right positions. The outcome is that when the stick assembly contacts the top of the spar tunnel there is approx 1.125" of clearance between the aft side of the spar tunnel and the stick assembly, whereas the plans recommend a 1/16" gap...This in-turn means that my idler to mixer pushrod is too long to permit the mixer assembly from reaching the full forward stop (full down) position.

One possible mix might be to shorten the idler to mixer pushrod, but this seams extreme.

Anybody else experience this?

Regards
Rodger Waiex #155

[N111YX]

Rodger, I do recall tolerances being tight there. Are you sure that the clearance cannot be taken up with the threaded (adjustable) pieces downstream? Can you post some pics...?

[RodgerC]

Hi Kip
Thanks for your interest...It may be possible to take up the excess length with the threaded rod ends at the ruddervator end, but because the interference between the AN4 bolts (at full left/right aileron deflection) and the top of the spar tunnel, I cannot get full forward stick travel. This means that the idler to mixer pushrod (which is supplied with an undrilled "tab" on the mixer end) is about 1.125" too long.

I hope the photos attached will clarify the situation. They depict the stick position when it contacts the spar tunnel in the full left and right positions.

BTW, I've emailed Kerry at Sonex for comment and eagerly await his advice too.

All the best
Rodger

Full Left

P4251551.jpg (72.18 KiB) Viewed 7600 times

Full Right

P4251552.jpg (72.96 KiB) Viewed 7600 times

Recent Pic

P3030619.jpg (54.41 KiB) Viewed 7600 times

[MichaelFarley56]

Hi Rodger,
Boy I wish I could help on this one, but I don't remember having that issue with my stick. Just my opinion but it would almost appear that your entire stick assembly is too low. If you keep your stick centered, can you then get full forward deflection? You may want to check the attach angles and spar tunnel for proper size and location.

Your project looks good!! Keep up the good work!!

[N111YX]

Rodger, I would have to side with Mike, here. Your clearance seems unusually tight. An option is to consider taper pins like those used in the mixer. It's very easy to end up with "slop" with this "tube in tube" arrangement. I originally used bolts and I could not stand the 1/4 inch of stick travel before the ailerons would move. I installed taper pins and it's tight as can be. Also, the taper pin will have very little "head" on one side that might be an advantage with your situation....

[RodgerC]

Thanks for the feedback gents...At the real risk of sounding like a self righteous Aussie, the position of the control frame is determined by the attach angles which were supplied predrilled from Sonex and the idler to mixer pushrod is a fixed length unit also supplied by the factory with end tabs for bushings welded insitu...I.e. Not the Sonex tube-in-tube type...I've checked and rechecked and there has been no opportunity for me to misinterpret any location positions, because they have all been predrilled or fixed by factory supplied components.

I've also discovered on Doug Boyd's online Waiex #80 log (23 Sept 2009) that he believed the idler to mixer pushrod was supplied too long which suggests he also wasn't achieving full forward control stick travel. (Doug, if perchance you monitor this forum, please feel free to pass comment.)

Kerry came back and said they believed that there are no errors with factory dimensions....I'd be more inclined to take his word if I hadn't recently cut the control stick penetrations in my seat sling to factory dimensions.

[Andy Walker]

My understanding is that the problem is not the stick not having full forward travel, but rather once there it can't turn properly because of bolt-to-tunnel interference, is that correct? If so Kip's taper pin suggestion might be a good first thing to try, it might free up some space for you.

The only other way I could see to solve this without re-dimensioning something is to install some kind of stick travel stop (either on the stick assembly or the spar tunnel) that prevents your stick from entering the part of travel that causes the interference. The problem with that solution is that you can't then get full down elevator. As sensitive as the Waiex controls are, the need for a full *down* elevator stick input will probably rarely/never happen, but installing a stop would limit you a bit. You'd have to evaluate how much travel you'd be giving up.

Have you sent this one to the factory? It definitely looks like something they could help resolve.

[RodgerC]

Hi Andy...Your understanding is correct and Kip's suggestion would help with travel in one direction, but not both. The factory's response was..."Hi Rodger,
Without the ailerons and elevators connected there is nothing to limit the travel of the sticks so something will strike them in any position.
There are no errors in this area of the well tested design (both the Waiex and Sonex share the same stick installation) so if your installation is per plans it will work. Some things for you to check, however: Correct hardware usage. Pivot mounting holes for the Universal Control Frame are in the correct location so the stick assembly is at the correct height and fore and aft location."

I have since discovered via the Australian Sonex group, another builder with this issue and that it may be associated with variations in the tolerances of the Universal Control Frame weldment.

At this stage the simplest fix seems to be shortening the idler to mixer pushrod by an inch which will still permit full travel but will result in the stick being positioned aft of its standard position in all phases of flight...I could live live that.

[Andy Walker]

[quote="RodgerC"
I have since discovered via the Australian Sonex group, another builder with this issue and that it may be associated with variations in the tolerances of the Universal Control Frame weldment.
[/quote]

Hmm...When I was getting my (Jabiru 3300 Trigear) engine mount ready for installation, I noticed that it was about 1/8" more narrow on top than the plans say. I asked Kerry about it, and he said something to the effect of "these things are all welded individually, and will never be 100% exactly to the plans, that's just the nature of welding."

So it very well could be the welded frame is not 100% true to plans. If it's not too much bother, you might want to pull your frame out and measure it against plans. At least if you found a glaring error you'd have something to respond to the somewhat snotty factory response with...

[RodgerC]

I have some sympathy for Kerry as he must receive many email enquiries from builders who haven't thought through their issues, so I'll let it slide and shorten the idler to mixer pushrod and inch or so, after I confirm that I'll still achieve full control travel, albeit with the stick an inch further back in my lap than standard.
Thanks for your interest...Onward and upward