Wing Attachment Hardware

[n307tw]

I posted this question as a poll in the Facebook group but I want a little more insight as to what the Sonex community is using to attach their wings to the fuselage. Do you use the standard AN Bolts and Nuts method or do you use the McMaster Carr quick release pins suggested by the factory? I’d like some feedback as to the pros/cons for both options. Thanks! -Tim


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[Bryan Cotton]

A lot of stuff from McMaster seems to be from China. Hopefully my AN bolts from Spruce are not.

[Sonex1517]

My two cents, worth far less.

I used AN hardware from Spruce. And I have to tap it in place.

Personally I like it that way.

[pappas]

Personally, I can't think of a reason that I ever want to take my wings off. I will never trailer the thing anywhere, I don't have limited space in my hangar, I do not want to take 45 minutes mating the wings and reattaching electronics and pitot static systems prior to every flight nor 45 minutes removing and storing them after each flight. Subsequently, I put the nuts and bolts in every plane I build.

Others surely have other needs. But for me, I'm flying it where I want it to be next, not trailering it.

Lou Pappas

[builderflyer]

Tim,

After 14 years of flying my Sonex, I recently recently removed the wings for the first time to do an internal inspection not otherwise possible, and to add wiring for new wingtip strobes. The wings went back on with the original "an" hardware. Like Bryan alluded to, I would hope that the "an" designation would provide a bit more credibility as to what we are relying on to hold our wings in place.

I believe that Sonex went to the pins back in the days when they were trailering their product to various airshow around the country. I wouldn't think there would be much of an advantage for even them to use pins any longer.

Art,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[Spaceman]

I'll offer a different opinion. My wings haven't fallen off yet, however they have 0 hours of flight time so take this for what it's worth. I'm building a B-model, and unlike the legacy, the seat on the B-model (if you follow the plans) isn't removable once everything is riveted. So once the seat is on you can't really get at the back of the main spar tunnel.

The plans give you the option of using AN bolts or pins, but after thinking about it I went with pins for that reason. I guess if you planned on removing the wings regularly you could build in some access panels to the seat pan to access the back side of the spar tunnel, but I didn't want to put that much thought into it.

The specs on the pins from McMaster Carr list a breaking strength in double shear of 36.5k lbs. So two of them, divided by the max gross weight of the plane is like 60 g's. So at max rage factor you're stressing the pins less than 10% of what they're rated for. I'm not too worried about it!

[Bryan Cotton]

Probably not 60 G. You have to do the pin joint analysis considering the shear each pin sees from wing bending.

[Spaceman]

Haha yeah I guess you're right.

Still, after 30 seconds of googling, I'm not an expert, but AN bolts have a minimum shear strength of 76,000 psi. So ~15k lbs for a 1/2" bolt, which is less than the pins.

My only concern with the pins was, how hard would it be for them to inadvertently slide out? I thought there would be some spec for the linear force it would take to yank one out without pressing the button but I haven't found it yet. When I got mine I put one in a hole in some scrap, stood on it, and tried to pull it out and I couldn't do it. I'm no bodybiulder but I know I can deadlift a couple hundred pounds easily so I don't think they're going to fall out. Plus with any load on the wings the pins would be pinched in place anyway I guess.

[mike.smith]

I have the pins and regularly do aerobatics and pull up to 4.7Gs. Nothing has fallen off, and after 5 years and nearly 500 hours, everything is still tight as a drum. I'd say either way works, so do whatever makes you happy. The chamfered end of the pin does help them go in easier.

[Rofomoto]

What direction do the 3/8” spar bolts in sonex A model go? Front to back? Thanx billy