Wing Pin Alternative

[Rmendler]

Hey fellow Foxers. Looking for opinions or experience with the OEM wing pins. I've never had a problem with them but they do make me nervous when I start pulling back on the stick.

Any stronger or better alternatives or should I run what I got? I never fold the wings, my model IV is permanately hangared

[Dave S]

Hi Richard,

The only stress on the Front spar pins is some shear, no axial stress; and, they are plenty heavy for the load they need to carry. Certainly a person could use a bolt on the front spar as there is on the rear spar but there would be no difference between a pin and a bolt of the same size and material as far as strength is concerned.

For the hairpin retainer, there is no flight stress on that component at all, just keeps the spar pin from bouncing around.

The only issue I have had with a front spar pin is getting a small scratch on one....replaced it and have kept an extra spare on hand since. Have since used a little grease on them and all is well.

I think you can be confident the OEM design using the spar pin is very solid and safe.

I always thought I would be folding my wings often, but the way it has worked out, the only time I fold the wings is on annual condition inspection.

Take care,
Dave S
KF7 Trigear, Flying
912ULS Warp Drive
St Paul, MN

[Rmendler]

Thanks for the quick response. I went up with an instructor the other day and he put the plane in a steep turn and pulled pretty hard. Made me nervous. Good to know I can put that to rest

[ackselle]

If you need to gain confidence, check this out on YouTube.... According to the description, this is an absolutely stock Kitfox IV Speedster....

http://m.youtube.com/watch?v=513UTHqoZBc

Enjoy!

Cheers,
Ackselle

[Esser]

An AN5 shear strength is 5750 lb unless I am mistaken.

[HighWing]

I've never tried this to find out, but back in the day, it was mentioned by someone at the factory and pretty much agreed upon that the airplane would fly fine if the pin came out. With the lift struts essentially supporting the airplane from its attachment point under the seat back, the forces on the pin are shear as mentioned, but compressive relative to the carry through tube. In other words the two pins hold the wings from folding forward.

The only experience I have ever heard of that supported this idea was a report by a guy trailering his Kitfox nose first. He said that one of the fittings that secured the folded wing between the aft lift srut and the vertical stabilizer came undone - right side - and he suffered some damage to the wing as it swung out to pretty much flying position and the wing tried to take down some road signs. This report was on one of the early Kitfox email lists.

[t j]

Folding wings have been around for a long time.

http://www.youtube.com/watch?v=YnvCFlG21ZM