I'm puzzled about the RV-12 spars.

[pierre smith]

God smiled on the South yesterday and handed us the most perfect flying day we could ask for...to Sebring!

Mitch Locke, Van's East coast rep is a wonderful guy, very knowledgable and accomodating. The crowds were all over the -12!

What puzzles me, is the location of the spars within their respective wings. Since they overlap each other, it would seem that one wing will have a spar further forward or backward, by their thickness, so that the leading edges align. Well, Mitch showed me that they do, in fact, align and so do all the rivet lines on both sides, align with the vertical rivet lines of the fuselage.

So what is going on inside the wings to make this alignment happen? Seems that one of the spars should be offset by their thickness.

Best,

[mrt890]

Pierre

The spar offset is compensated for by having different length ribs. The forward spar has shorter nose ribs and longer main ribs. Opposite for the aft spar.

[sailvi767]

Pierre, It was a great day to fly in the south yesterday. I took off for a quick autopilot check and ended up flying for over an hour. It was completely dead calm from the surface to 5000 feet. I don't think I felt a single bump. Almost kind of eerie. I ended up flying to two different airports doing touch and go's and just putting around. On final the airplane just flat did not move. Not a wing waggle. I finally nailed a bunch of wheel landings but conditions were so easy I don't think I can really count them!!!!

George

[rvbuilder2002]

Originally Posted by mrt890

Pierre

The spar offset is compensated for by having different length ribs. The forward spar has shorter nose ribs and longer main ribs. Opposite for the aft spar.

Expanding the explanation...

The main spar channel is in the same cord wise location in each wing, but the spar cap materials are not. On one wing, all of the spar cap material and the spar stub portion ( the portion that inserts into the fuselage to overlap with the opposite wing spar) is on the front side of the spar channel, and on the other wing it is on the back side. This is what allows the two to over lap each other but still have the wings in the same for/aft position on the fuselage.

So, as Michael pointed out, there is a means for having variable length ribs to accommodate the differences in structure between the left and right wing.

[pierre smith]

Thanks guys...a very impressive little airplane!

I also learned from Mitch that the wing pins' locks are wired to magnetic reed switches that prevent the starter from turning if the locking pins aren't seated.

Thanks again,

[Geico266]

Originally Posted by pierre smith

Thanks guys...a very impressive little airplane!

I also learned from Mitch that the wing pins' locks are wired to magnetic reed switches that prevent the starter from turning if the locking pins aren't seated.

Thanks again,

On the panel is a big red button switch that lights up if the wing spar pin handles are not in position. If the light is on and you are confident the pins are in correctly you can depress the button switch to override the lock out feature also. That way you can start the plane and fix it later if it is a malfunction of a reed switch. Very cool idea.

[DaveLS]

This is the forward face of the right and left spars. The forward ribs are attached to the angles. Note that the angles are of different lengths to allow the spar stubs to overlap in the fuselage.

-Dave