Taper Pin Installation

[bbz8]

Hello everyone,

I have been flying my IIL for about 21 hours. I had to move airports and rent out a friend's hangar. Long story but my wings had to get taken off to make room in the hangar. I never took photos or even thought to take them when I bought the plane. My A&P buddy and his home builder wife took them off (with permission) while I was out of town. I go to reattach them today and realized I have no clue what I'm doing.

I'm an A&P and could figure it out but after looking at plans I'm even more confused. I'm used to bolts holding wings on and am not ashamed to ask for help. I work on jets primarily so this never comes up.

I see we use taper pins in the plans. I have taper pins with threads on the aft side, a bolt head on the fwd side and about 2-7 washers on each.

Dumb questions:
1. Is the nut head to prevent spinning while attaching the nut which acts as a security measure to prevent it from backing out? Or is the nut being used with washers on the aft side to pull the pin aft (forcing the thicker taper into the smaller hole)?

2. How deep do the pins go in? Buddy swears they were flush. I don't remember the fattest part being flush and remember seeing bolt heads sticking out an inch.

3. Do you hammer these in until the sound changes? His wife brings up a good theory that this would give us our depth. To me it could also damage the spar and the taper profile over time(?)

4. I'll try to get a photo of them, but does my taper pin setup sound correct? The read spar pins are missing so that's another can of worms

Any photos of your setups would be greatly appreciated and speak volumes.

I was hoping to find a post I saw a while ago but can't locate it after hours of searching.

 

[wsimpso1]

I Was hoping a Sonerai person would respond. I can only respond with more general knowledge.

I see we use taper pins in the plans. I have taper pins with threads on the aft side, a bolt head on the fwd side and about 2-7 washers on each.

Washers usually allow us to tighten the nut that loads the taper to work without bottoming.

Dumb questions:

Probably not...

1. Is the nut head to prevent spinning while attaching the nut which acts as a security measure to prevent it from backing out? Or is the nut being used with washers on the aft side to pull the pin aft (forcing the thicker taper into the smaller hole)?

If there is a bolt type head on the larger diameter end and theads and nut on the smaller diameter end, the nut is tightened to secure the pin in the tapered hole and preload the assembly. The bolt head on the larger diameter end allows you get torque on the nut and perhaps to help with loosening the pin for withdrawal.

2. How deep do the pins go in? Buddy swears they were flush. I don't remember the fattest part being flush and remember seeing bolt heads sticking out an inch.

Depends on how deep the tapers were cut...

3. Do you hammer these in until the sound changes? His wife brings up a good theory that this would give us our depth. To me it could also damage the spar and the taper profile over time(?)

Ideally they maked holes and pins so each hole and pin stay together. Once it hss been assembled once, you should be able to seat them pretty well by hand and finish by tightening the nut. I have always hated using hammer as a verb... sounds destructive. Using hammer and punch to acheive assembly and preload bothers me too. Wherever possible a lever or screw type press makes way more sense for assembly and disassembly. Biycycle crank arms used to be assembled to the bottom.bracket with pins with a tapered flat, and if you used a hammer, the threads were destroyed- a lever press was used.

4. I'll try to get a photo of them, but does my taper pin setup sound correct? The read spar pins are missing so that's another can of worms

Any photos of your setups would be greatly appreciated and speak volumes.

I was hoping to find a post I saw a while ago but can't locate it after hours of searching.

With us all carrying a camera in our pockets, they did not take pictures as they went?

Taper pin joints are designed to secure an assembly with zero slop. I expect that a taper pin wing attachment is intended to facilate transport from shop to airport, then remain assembled. They usually are not intended for frequent assembly/disassembly.

They can be schemed up with only taper, with threaded ends for assembly and securing in place, and even with threaded ends for extraction.

I am accustomed to only using a hammer and punch on pretty small stuff - on the order of 3/16 and less. I would not be inclined to use a hammer and punch on a wing attach scheme with them.

Now that I have stuck my neck out and posted, someone more knoledgible on the Sonerai wing attach is likely to chime and tell us how wrong I am, hopefully with useful info specific the your bird.

Billski

 

[lr27]

It might help to put Sonerai in the title.

Sailplanes have their wings on and off frequently, some with taper pins. If the Sonerai is set up the same way, there may not be much need to worry. At least if you do it right, anyway.

There may be a torque specification for assembling these pins. If so, it's probably important that the threads' and pins' surfaces are per spec. Either just nice and clean, or cleaned and lubed somehow.

deleted useless remark

 

[soneraifred]

Don’t make this harder than it is. The taper pin is placed in the hole and lightly tapped into place. You should have about 1/16” of the pin sticking out the small end. Use taper pin washers on the threaded end, and tighten the nut just enough to keep the washer from turning. Do not tighten the nut any tighter or you will have hell to pay to drive the pins out (ask me how I know).

 

[wsimpso1]

It might help to put Sonerai in the title.

It IS in the Sonerai sub forum...

 

[lr27]

Oops!

 

[wsimpso1]

Oops!

Little stuff...

 

[bbz8]

Don’t make this harder than it is. The taper pin is placed in the hole and lightly tapped into place. You should have about 1/16” of the pin sticking out the small end. Use taper pin washers on the threaded end, and tighten the nut just enough to keep the washer from turning. Do not tighten the nut any tighter or you will have hell to pay to drive the pins out (ask me how I know).

Thank you for the reply! I felt stupid asking but when life is at stake, why not? I appreciate the detailed replies and after finally seeing the plane today it sounds like they're properly installed.

These taper pins seem easy but sometimes easy gets messed up the worst. The narrow ends stick out about 1/4" so we're pretty close.

Thanks Fred!

 

[bbz8]

Thanks for all of the detail in your reply. I appreciate it greatly. Your message made me make the drive up to check out the pins again. It's amazing how simple it is now without the frustration and external input of my friends who removed them.

I wish they grabbed photos but I guess they assumed I had some before giving the okay. A breakdown in communication I suppose. I assumed they'd take photos out of respect/courtesy. You know what they say about assumptions.

Thanks again,

Greg

 

[lr27]

Might be something to check after the first flight and a couple more.

 

[Daleandee]

Thank you for the reply! I felt stupid asking but when life is at stake, why not?

Asking was not stupid ... not asking would have been!

 

[Ebell]

What Fred wrote above is the correct answer. On my SIIL, I over-reamed two of my pins slightly and use a washer in addition to the taper pin washer to hold the pin in place. Additionally, I use a castellated nut to secure the pin with safety pins to ensure the nuts don't back off. Even more additionally, I welded nuts on the fat ends of the pins to facilitate removal (i.e. Fred's comment above - if they go in too tight, they can be very difficult to remove.

 

[TFF]

Depending on multiple things, repeated removal and installation will reseat the pin deeper and deeper. Much harder with bigger pins but small ones almost always do.

 

[Skippydiesel]

Don’t make this harder than it is. The taper pin is placed in the hole and lightly tapped into place. You should have about 1/16” of the pin sticking out the small end. Use taper pin washers on the threaded end, and tighten the nut just enough to keep the washer from turning. Do not tighten the nut any tighter or you will have hell to pay to drive the pins out (ask me how I know).

Listen to Sonaraifred - Tapers like the ones described do two things;

• Locate/align holes
• Secure IN SHEAR not compression

They are usually secured in place by a thread bolt/rod under low torque ie the bolt does nothing (no load) other than keep the pins in place.

If used correctly, they should not experience wear - they don't move so there is nothing to cause wear.

Depending on installation instructions, they may be lubricated or not. If lubed, use something that will assist in removal & resist corrosion eg a long life high solids anti seize.