Replies to This Discussion

Permalink Reply by Andy Elliott on November 16, 2009 at 6:06am

I did some reverse calculations from the ultimate load test report, and determined that the wings need to weigh at least 55 kg each to make the 2280 kg ultimate load test valid. I never did any weights of completed wings during my build. Is the 55 kg per wing a good number, even for folks with some lighter skins and no paint?

Permalink Reply by Matt Heintz on November 16, 2009 at 10:17am

Andy,
This is an in depth question you are asking. Did you take into account the weight of the centre spar and things directly attached to it. I think that Chris used 59 kg. Also, for the span wise lift distribution, did you take into account the geometric wing twist and the aileron twist?

Permalink Reply by Andy Elliott on November 16, 2009 at 10:58am

Mathieu:

No, I just did it the quick and dirty way: 2280 / 6 = 380 kg. Design gross - 600 kg. Delta = 220 kg. A/C is upside down (1 * wing weight) and [2] usually one leaves out the wing weight when looking for root bending loads (another 1 * wing weight). So the delta mass ought to equal 2X weight of wings set, or 4X weight of one wing. 220/4 = 55 kg.

Of course, a proper accounting would, as you say, take into account the spanwise lift and mass distributions, but the Q&D approach at least checks that we are in the ball park and with a tapered wing like the 1XL's, should be conservative. (That's why sometimes loads problem can be band-aided with some mass out at the end of the main spar!)

So, anyway, what is a reasonable range for real one wing weights??
Andy

Permalink Reply by Matt Heintz on November 16, 2009 at 1:12pm

For just one wing, the reasonable weight is about 43 kg. With paint, extra large fuel tank, lights etc. it would could well be your 55 kg.

Permalink Reply by Franz S. on November 16, 2009 at 10:16am

Hello Mathieu,
I have my wings completed but an edge problem with the wing locker with the new "L" extrusion.
The distance of my wing locker hinge from the main spar is 21 mm, the "L" extrusion 25.4 mm. Thus does not fit the wing locker cover and I would have to renew the whole upper skin and the wing locker cover, because in the front part of the rear top skin is a 5 mm gap between piano hinge and rear top skin.
Should I put instead of the new extrusion a doubler L-angle (.063) on the underside of the spar angle 6W3-6?

Franz

Permalink Reply by Matt Heintz on November 16, 2009 at 1:16pm

You have already upgraded your wing?
I am surprised as the drawings are on the web as "DRAFT". We are still looking at changes as we are consulting with outside engineers right now.
I would not start the upgrade until you have the final drawings.
Regarding your wing locker question, I do not follow. Please fax me a drawing at 705-526-8022 and I will forward it to Chris.

Permalink Reply by Bob Pustell on November 16, 2009 at 4:48pm

Mathieu -- I read this as he has not upgraded his wing yet. It is built and has winglockers. He has done some measuring and thinking and has a problem. I think, in his wing locker question, he is saying that if you mount the locker door hinge on the aft edge of the new L extrusion (similarly to how it was mounted on the old flange), the door and hinge will be moved a little over four mm aft, which will not line up with the existing locker hole in the wing skin. This gives you a large overlap in the back of the door and a four or five mm gap ahead of the door where there is no skin. This also means all the fasteners in the door to hold it closed do not line up with their mates in the wing. This, however, allows the rolled portion of the hinge to be down inside the wing.

In a post yesterday by Jerold Ebke, he worried about the fact that the hinge will not sit flush with the skin due to that four mm increase in the flange (he was assuming the hinge and door will stay in the same place to line up the door with the existing locker hole in the wing and allow the door fasteners to line up with their mates in the wing).

So, it boils down to this for an existing wing locker installation: If you install the hinge at the aft edge of the new L extrusion, your door is 4mm aft of the hole in your wing. If you install the door so that it lines up with the existing hole in the wing, the rolled portion of the hinge (the part that has the hinge pin in it) conflicts with the larger overhang of the new L extrusion and your hinge and door leading edge will be cocked up above the top of the wing.

Both these concerns should be moot for someone (like me) who has not built the wing yet. I can put the locker hole in my wing skin four mm further aft and solve the whole problem. I think. ??

Permalink Reply by John Partridge on November 16, 2009 at 5:48pm

Good point Bob. I have wing lockers and came up with the same problem.

Regards,

John

Permalink Reply by Matt Heintz on November 16, 2009 at 7:51pm

Franz and Bob and other who have the wing lockers.
If you want to use the same wing locker door, here is what I recommend.
- Cut the wing locker door so that it fits at the piano hinge which you need to attach to the new "L" extrusion.

Problem you will have is that the old rivet line is at the edge of the door at piano hinge. So put new rivets between with proper edge distance and fill old holes with body filler. Once painted, it will look great.

Also, please see the 650 wing locker assembly as there is a new "L" angles that you may want to install on the door.

Attachments:

• 650 wing locker.jpg, 109 KB

Permalink Reply by Bob Pustell on November 16, 2009 at 11:26pm

I will be starting my lockers from the start (my wings are not yet built) so this discussion was mainly for Franz and Jerold and others with already built wings with lockers. I thank you, however, for the 650 locker door drawing. I have been thinking it would be good to beef up that door to prevent bowing in flight, looks like you guys came to the same conclusion.

Just to clarify. When I build my wings, if I just move my locker opening back that four mm or so to allow for the L extrusion, I should be able to install the locker as previously planned, correct?

Permalink Reply by Franz S. on November 17, 2009 at 9:34am

Ok, thank you, but in the front part of the rear top skin will be a 5 mm gap between piano hinge and rear top skin. Maybe in this area trim the new L-angle on the rear edge and on the underside an additional L-angle?

Permalink Reply by Tim Juhl on November 17, 2009 at 2:58pm

Mathieu,
[Ref: XL Plans 3/06 - for wings already built.] I'm having some trouble following your explanation of how to deal with wing lockers in the modification of the wings. Forgetting about the wing locker door for a moment, if you install the new top angle and it is 5 mm wider then I think as you look into the existing locker opening you would see the edge of the angle extending into the opening beyond where the edge of the leading edge overlaps the top skin. Currently that edge is flush with the door opening and the hinge pin rests against it. With the additional top angle width a wider hinge would have to be used in order to use the original holes but you would still have an unsightly space between where the leading edge skin ends and the hinge begins where the spar angle would be exposed (rather than hidden under the top skin.) People who have yet to install the lockers can easily deal with this but what about the rest of us?

One option would be to machine 5 mm off the edge of the top angle in the area of the locker to bring everything back into alignment. The question is whether doing so would affect the angle's strength. Of course, the addition of the thickness of the piano hinge in this area would lend some additional strength to the angle so maybe it would equal out in the end. In addition, it would be necessary to shim the hinge section attached to the door in order to account for the extra thickness of the spar angle and bring the door into alignment with the skin. With the rivets in this area going through two skins, a thicker angle and the piano hinge I wonder if you should consider installation of some larger or perhaps stainless steel rivets in the modification.

Am I making any sense here?

Tim

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