Installing the "Snap Latch" wing retention clips

[lenb]

A few of us have been jumping on the bandwagon lately with these Snap Latch clips obtained from McMaster Carr. They're easy to install and make wing installation at the field a "Snap".

The following is a brief outline of the process for my installation. Your process may vary slightly, but it's pretty straight forward.


Parts needed

These Latches can be ordered from McMaster Carr

304 Stainless Steel Part latch, Part # 1872A71 They cost about $6.00 each and come with the latch and the stud head. This is called a "set", so don't, be fooled thinking there are two in a package.

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Parts needed

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Step 1,

Make a plywood spacer block for the latch, thickness is determined by what's needed in the plane. Typically about 1/4" thick will allow you to attach the latch to the block.

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Make the block so it rests up against the stringer, bulkhead, or some sort of "positioning" guide and centers over the bolt attachment hole.

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Step 2,

The outside diameter of the stud head is 3/8", so you will need to accurately drill a hole slightly larger ( 7/16 or 1/2 ) through the airplane and block at the same time. This will ensure proper alignment. Hold the block on the inside with a clamp or tack glue. I like to use a stepping UNI-BIT for drilling these type holes, however any bit will work if you're careful.





You'll need to hold the block in its exact location as you make the hole.

[lenb]

Step 3,

Attach the clip to the block, CAREFULLY align the hole in the clip to the hole in the block. Attach with a cap head screw. You can use a bolt if you want to go through the effort of countersinking a blind nut on the backside of the block. I just use a cap head wood screw then grind off the tips that protrude through the backside.

It's important to use a cap head screw so the "cap" acts as a stop and does not allow the clip to come apart when pulled open.
(Pre-drilling the hole for the screw will help when attaching the clips to the block)




Step 4

You will need a longer attachment bolt than the one that came with the plane. Slip the stud head over the bolt and screw it loosely onto the wing root.


**** At this point you need to determine a couple things. If the bolt you are using is thicker than 5/32" ( about an 8-32 ) then you will need to drill out the stud head.

I have drilled the stud head out as much at 6mm recently with no strength issues.




IF it is smaller than 8-32 size, you will need to bush the hole so the stud head stays somewhat centered on the bolt.



Slip the wing onto the plane with the attachment bolts and stud head on the wing root.
Slid the block with the clip over the stud head and into position on the fuselage side.






Snap the clip over the stud head and tighten the screw so it's snug. NOT TIGHT. Holding the block in place, test the latch a few times and ensure its a snapping movement, not too difficult.







Step 5 Photo


Unlatch the clips and carefully pull the wing off the plane, try not to let the screw turn and loose your setting.

Measure the spacer size needed to fit the bolt. You can get standard spacers and shim the clip off the plywood or you can make the spacer yourself. I make them out of Delrin on a small lathe





The OS diameter of the spacer should be a little less than the hole in the fuse side. This will allow the fuse side to help support the bolt when locking the wing on.

Place the spacer under the bolts and snug them down.



Step 6 Photo


Slide the wing back on the plane and snap the latches over the stud heads, test the pressure and adjust the bolt in place. (the spacer will crush into the wing root a little if you need to tighten the pressure a bit)


They do not have to be straight up and down, since there is a positive snap to the latch they can even be mounted upside down as in a high wing airplane where you access the latch from the cabin

If you are happy with the setup, remove the blocks/clip and apply a small amount of 5 min epoxy to the back of the block, do not get it near the hold. Carefully place the block/clip back into position and snap it shut.


WAIT for the glue to set, test the left over glue on the mixing pad. Once it is firm, remove the wing immediately to ensure you did not get glue on the stud head or spacer. (I usually do, so now is the time to clean it off with rubbing alcohol)



*** At this point I will usually do the other wing and get it to this point.

[lenb]

FINAL STEPS





Remove the bolts from the wing root and clean with rubbing alcohol or lacquer thinner, then apply a generous amount of BLUE Loctite to the bolt and screw back into position.



Slip the wing onto the fuselage and check the latch for firmness. Now is the time to make any final adjustments before letting the Loctite set up. Once happy, let the plane sit for the night while the Loctite sets.



Notes:


These latches work great for holding the wings on, they are simply meant to keep the wing from sliding off the plane. They are not a structural part of the plane. If you rely on the wing bolts to hold flying loads, you may want to think of something else. If your plane uses a wing tube, wing spar or struts, then these are perfect for keeping the wing from sliding away from the fuse.


I use a wire with a hook at the end to reach down into the fuse for the hard to reach clip, then pull up to release, a screwdriver can be used to push it closed when attaching.


Also, be sure to have the clips in the OPEN position when putting on the wing or you can damage the clip by pushing too hard against it if it's closed.


You can squeeze the clip sides before installing to create some resistance if the clip slides too easy in the tracks. This will help keep them open when installing the wings.

[ARUP]

Noyce! Thanks for the tutorial! Very helpful stuff, son!!!

[gunny11]

Excellent write up Len! Handy little things for tight spaces. Thanks for sharing.

[Mosquito]

I just finished up a set for my 170 Bidule. Work nicely so far!

Tim

[Mark Taylor]

Very cool LB, I dig it!

[dcwwcp]

I know this is an old thread, but these are pretty cool!
how much do they weigh?

Thanks
Don