R

RFSchaller

Well Known Member
I am thinking about pinning the stub spars in the sockets with 1/4" bolts to eliminate play. Any thoughts on this approach? Forget the issue of flexibility to remove wings as I don't care about it.
 
The socket allows the rounded end of stub spar to rotate a bit in the vertical plane as the wing responds to flight loads. If you bolt it, the stub spar will be much more restrained in its socket, and this could have unintended consequences. High shear loads in the stub spar for one. Also, would you envisage an interference fit for the bolts, or would the holes have a tolerance as well?
I don't have the answers, and it may be quite OK, but I wouldn't do it on my plane.
 
If you have play in the wings add brass shim stock to the fore and aft spar sockets to take up the slack. No need to bolt them.
 
I am no engineer (although I have played one on TV), but before I made such a move, it would have the blessing of the engineering department at Van's A/C. If you have an issue, take the time required to work through it. Good luck and most of all, be safe!
 
Thanks for the comments. My take on it is that the stub spars are basically anti-rotation devices that counteract the tendency of induced drag and lift to rotate the leading edge upwards.

My wing leading edge on the pilot side moves downward about 1/32" when I step on the wing walk, so that's why I concluded the easiest solution would be to pin the stub spar in the position where the stub spar contacts the socket (leading edge upper most) so loads would be distributed to the socket in all but negative G.

Does this reasoning make sense to you guys? Nothing like a little peer review for a reality check!
 
RFSchaller said:
My take on it is that the stub spars are basically anti-rotation devices that counteract the tendency of induced drag and lift to rotate the leading edge upwards.
Click to expand...

Flight loads could make the wing move either up or down, fore or aft, or twist about it's longitudinal axis (ie. rotate around the main spar). In order to accommodate the rotation of the stub spar that results from the up and down flexing of the wing or any twisting in the wing, the stub spars need to be able to rotate in the vertical plane (like aileron hinges), which is what the rounded end in the socket allows it to do. Obviously they also need to resist the straight up and down loads (and fore and aft loads) at the socket.

My concern was that introducing a bolt, depending on exactly where you put it in the stub spar, how much tolerance there is in the bolt holes and how well the rounded end of the spar matches its socket, you may tend to `lock-up' the joint and impede the hinge action. We are not necessarily talking about large movements, but you don't need large movement to induce large forces in a locked joint. The forces will still go somewhere, but you may not like the result. Even if nothing broke you risk additional wear in the socket due to friction. I'm not an aeronautical engineer, but I'd at least get Van's opinion before I did it.
 
For the guys who used shims: was it to shim the socket depth or socket width? I can see using thin plates on the width, but what are you guys using on the depth?
 
There are alternate aft spar stub parts available to resolve this issue on an RV-12 if it occurs.
They are available in small increments for the rear spar and are quite easy to replace.
Contact Van's tech. support... they can help you order the size you need.
 
Scott,

My main concern is the 1/32" movement of the wing leading edge when I step on the wing walk. Have you guys seen that before?

Rich
 
Rich, I am curious as to how you are measuring the movement of your wing? Are you rigging a dial indicator between the fuselage and the wing?
 
RFSchaller said:
Scott,

My main concern is the 1/32" movement of the wing leading edge when I step on the wing walk. Have you guys seen that before?

Rich
Click to expand...

1/32" of vertical movement sounds like a huge amount, but with the way the joint is designed, it could possibly move vertically if it is pulled away horizontally.
Though for this to happen, I would expect there to be an even more noticeable amount of fore and aft (sweep) play in the wing.
Measuring the lateral play at the rear spar stub while trying to sweep the wing fore and aft, is the best indicator of what is going.
Once you have that measurement, it should be easy to determine which replacement part you need. I think tech. support has a document they can e-mail you that described the measurement procedure.
 
Scott,

I have some barely perceptible for and aft movement. My understanding is that 0.03" at the wingtip is the limit. Is that correct? I'll measure it with a dial indicator this week and see what it is. The corresponding tolerance at the wing root is 0.01" isn't it?

Thanks

Rich
 
Dave,

The 1/32" is a calibrated eyeball looking at the wing root line at the leading edge relative to the fuselage skin.

Rich
 
Call me Rich

Rich we visited last year during a visit to Phoenix. Please call me if you get a chance. 303-435-4098
 
You must log in or register to reply here.