Wing Bolt Pros and Cons

[Area 51%]

The spars have been built, and it's time to mate the "Mothers".

I'm leaning heavily toward reaming the attaching holes to full size, rather than stop at 1/4in untill the rigging process. Just seems to be less of a chance of a hole screw-up.

Is there anyone out there that has had a bad experience in doing it this way? Avoidable?

My other concern is the actual hole size. I do like the idea of the hitch pins. In fact, I just ordered a his-and-hers set from McMaster Carr. Are these actually .375in in diameter? The mounting bolts that came in the hardware kit are only .3715in as measured in the middle of the bolt. They actually get slightly fatter near the threads and head by almost .0015in which makes a reamer choice difficult for me. Would I ream to the .3730 dimention, or use the .3715 I already have on hand and either drive the bolt in, or polish the fat spots? I only ask that question in case the hitch pins have similar characteristics.

The wing assembly process is on hold until I get this sorted out. Fortunately, I still have plenty to do on that "pesky" fuselage.

P.S. Did anyone else find the Sebring Light Sport Expo a waste of time? (excluding the drone races of course)

Fat, Dumb, and Happy here @ Area 51%

[Bryan Cotton]

Randy,
I have a hard time understanding the appeal of hitch pins rather than bolts. Polishing down the fat part of the bolts seems ok. I figure grease and oil can be corrosion protection rather than cad plate which will get scraped anyway. Never hurts to drill and ream scrap first, at least for a non-machinist like myself. That is how I like to check fit.

[mike.smith]

Randy,
I have a hard time understanding the appeal of hitch pins rather than bolts. Polishing down the fat part of the bolts seems ok. I figure grease and oil can be corrosion protection rather than cad plate which will get scraped anyway. Never hurts to drill and ream scrap first, at least for a non-machinist like myself. That is how I like to check fit.

They are smooth, pointed, drive easily, and secure with a cotter pin that will never back out under vibration. I secured the cable of my cotter pins to the spar tunnel so if I ever take the wings off the cotter pins will not get lost. Sonex uses them in their factory planes. It's a pretty win-win solution.

https://www.grainger.com/product/Hitch- ... Pid=search
http://www.mykitlog.com/users/display_l ... 948&row=16

[sonex892.]

The spars have been built, and it's time to mate the "Mothers".

I'm leaning heavily toward reaming the attaching holes to full size, rather than stop at 1/4in untill the rigging process. Just seems to be less of a chance of a hole screw-up.

Is there anyone out there that has had a bad experience in doing it this way? Avoidable?

I agree there is definitely less chance of a screw up, when drilling attach holes in the mated spars to full size. I did that, then later used the drill guide method to rig the wings. It worked a treat.

With regard to up sizing these holes on the mated spars prior to building the wings. Sonex appear to have now changed their minds and altered their instructions. For the B model they are now recommending up drilling the mated spars. One difference between the models here, is the wing bolts on the B are increased in size to 1/2" and the new attach blocks are machined from billet. Not a block bolted to aluminium angle. Check out Spaceman's B model build log. http://paegelow.blogspot.com/

I didn't use a reamer, I rigged my wings well before the reamer conversation came along. I just used a long 3/8" bit. The AN bolts are as tight as. Even lubricated they need to be tapped in and out.

Steve
Sonex 892

[dtwolcott]

Reply to Sonex 892

After doing it both ways, don't ask why, I would definitely recommend up drilling to 3/8 with just the spars mated and using the 1/4 drill guide to rig to airplane. This make these hole in the attach blocks in perfect alignment.
Don

[Area 51%]

Just for kicks, I got a pair of hitch pins from both McMaster-Carr, and Grainger. What I found was the Carr pins have a tighter tolerance. They only varied .0005 as measured anywhere on the pin. The actual measurement was between .3700 and .3695.

The Grainger pins went from .373 at the head, to .3705 in the middle, to .3715 near the tip. Even at that, they are better than the AN bolts.

.3705 and .3710 reamers are on the way, and will be available to anyone who might need them when I finish.

Now, about those drill guides. Are they homemade, or is that something I need to go shopping for?

The glaciers are gaining on me here @ Area 51%

[Bryan Cotton]

Randy,
They are both. You will need 3/8" OD, 1/4" I'd tube. The 3/8" will need to be turned down to your hitch pin size. The 1/4" is actually less and you will need to run a drill through it. You need a lathe, or in my case a friend with a lathe who knows how to use it. Mine were turned down to .3725".

[sonex892.]

Now, about those drill guides. Are they homemade, or is that something I need to go shopping for?

The glaciers are gaining on me here @ Area 51%

For the shopping part I bought a foot of bushing stock form ACS.
https://www.aircraftspruce.com/catalog/ ... ushing.php