Flying wires slack on Quicksilver MXL

zaitcev

zaitcev

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Pete Zaitcev
I met a local pilot at the airport today, Joe, who disassembled and reassembled his MXL. It's not the first time he's done this. However, mysteriously, this time a couple of rear flying wires are completely slack. The airplane does not look crooked, so he is unable to figure out what's wrong. I proposed to ask on the Internet.

Please see the attached picture.

The cables going from the front anchor (A) to _both_ leading edge (C) and rear edge (D) are taut. Only the cable between the rear lower anchor (B) and rear edge (D) is slack. The wires are exactly symmetric between left and right (two wires are slack on left and right).

Is this something of a well-known assembly mistake, and if yes, what is it?
 

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Is the angle of incidence on the wing correct? That would be my first check, potential missing mounting block or such for either the wing or Kingpost.
 
It's my understanding that the angle of incidence against the root bar is fixed. So the question can only be if root bar is aligned to the wheels (lower frame).

It seems to me that rear uprights are too short. But I cannot imagine how they can be too short, since they are originals for the airplane. They cannot be mounted onto a wrong hole, because they are at right angles to the root bar and cannot be made sticking out longer. It is similarly impossible to swap rear and front uprights, if only because the front ones are shorter, so the effect is going to be greater if you do it.

As the kingpost is adjusted on that airplane, the slack comes out of all wires uniformly (both landing and flying wires), except the B-D.

I did not realize a mounting block was involved, so I'll pass it on. I thought uprights just bolted to root bar. It cannot be seen in the picture because of the 2-ply sails.

Joe decided to fly it like it is (he may be a little crazy), and observe in flight. He returned safely and said that the B-D wires do not come tight in flight. And no wonder, the slack is so great.
 
Wires put back in the wrong place? Just guessing.
 
As for mounting block, that was a guess as it appears that a small part could be missing which would solve Occam's Razor, it could be an issue as small as washers in the wrong place. I'd really need to see the drawings for the craft to find the most likely issues. Since the root bar to the frame sets the angle of incidence with regards to the required geometry, this is where I would be looking. Is it possible to mount the root bar upside down? You're only looking at an issue that will change the mounting a fraction of an inch off center positive to negative to cause that slack.
 
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If they're "flying" wires, they may well be loose on the ground. They're only under tension when the wing is producing lift.
 
Henning said:
Is it possible to mount the root bar upside down?
Click to expand...
I saw that root bar and I think it may be possible. It's definitely not possible to mount in wrong direction due to welded-on hinges, but upside-down may be possible. I'll pass it on, thanks.
 
From what I understand, that rear axle cable is suppose to be slack, from B to D.

From TriKite.com 's website:
The wires from the wing to the landing axle should have some slack to allow the axle to move from side to side a bit. This allows the axle to get both wheels on the ground to cut landing loads by two. One wheel landings with tight wing/axle wires would put all the load on one wheel until the plane slowed and got level with the ground.
 
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I would hope that between 2102 and now the OP's buddy figured it out. ;)
 
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