What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

8-32 screws for wing tips?

mstrauss

Well Known Member
Patron
I was looking at using the Click-Bond nut-plates for my RV14 wing tips, but at $4-5/each, I am thinking not. I started looking around for alternatives to click-bond, and came across a company called Rotaloc that manufactures "bonding fasteners". They come in all sorts of sized, materials and finishes. They are meant to be adhesive bonded to a substrate. They look to be popular in lots of fields, and applications including composites. They do support a screw size of 6-32, but it is not a stock item, which means a custom order is needed, and that involves minimus of 1,000 parts and 5 month lead times.

The Up side to all this is the price, they are less then $1/each if ordering from stock. Down side, they only stock some options with the smallest nut size being 8-32. That is why I ask, are 8-32 to big for attaching the wing tips?

I have not started my wings yet, so I have the time to put in a custom order, but I don't need 1000 plates. I suppose, if a group were interested, we could pool together an order.

Now I am not a chemist or structural engineer, I know there are those that would advise not affixing the fasteners (plates with nuts welded to them) with adhesive, but I love the idea of not riveting these in place.

Thoughts?
 
Last edited:
I know of one builder who went wild ($$$) with click-bonds for the wing tip screws. More than 1 detached and would just spin with the screw. He had quite a time trying to get the wing tips off. I would stick with the nutplates attached to the wing tips with a backing strip of aluminum.
I don't see any advantage using a larger screw size. You would have to use a larger dimple and it is already close to the edge of the wing skins.
 
Just curious - what's wrong with the 6-32 nutplates? Another option is piano hinge - many have had success with that method.
 
To answer your question, yes #8 screws and nutplates will fit just fine. The RV6 kit that I didn’t start but finished, had the tips installed already with #8 screws. It looks good and is easy to remove/install. #6 screws also work very well. I built one RV with the hinges for wingtip attachment and that looked and functioned well too. However, it was a lot more work to make that hinge fit right. On my first RV8 I made my wingtips non-removable. I pop-riveted them on and glassed over the seam. After paint it looked terrific. I had no reason to ever remove the wingtip, so this was the least work required for a beautiful installation.
 
Hinges

I did the hinge thing. I wrote an article. If you want to read the draft, shoot me an e-mail. See below.
It was a bit of work, but the wingtips go on an off easy.
If the hinge isn't of interest, I would go with nutplates for sure.
 
I would never use bonded on nuts for anything that you have no access to the back side and definitely not were you have dozens required to work. That just multiples the chance of an issue and at some point you will have one spin. The headache one failure would cause is immensely more than that of doing riveted platenuts in first place. Also cleaning and having smooth surface for good bond on fiberglass takes some prep work maybe equal to riveting on platenuts.

I used the #4 fastener kit from, I think, Cleveland tool. I would not go as small as #4 again as there is too big a chance of stripping or twisting off a head. I have a special bit that came with the kit that I store in special place so I don’t loose it. What I did do, and do again, for all platenuts on the back side of fiberglass is bond on a 0.016 aluminum strip. Then attached the platenuts with rivets through fiberglass and aluminum strip. I don’t like forming a rivet shop heads against fiberglass as it crushes it. I then use dimpled washers under all the attaching screw heads. This has held up without any problems for screwing on and off through 16 condition inspections. YMMV
 
Last edited:
I was looking at using the Click-Bond nut-plates for my RV14 wing tips, but at $4-5/each, I am thinking not. I started looking around for alternatives to click-bond, and came across a company called Rotaloc that manufactures "bonding fasteners". They come in all sorts of sized, materials and finishes. They are meant to be adhesive bonded to a substrate. They look to be popular in lots of fields, and applications including composites. They do support a screw size of 6-32, but it is not a stock item, which means a custom order is needed, and that involves minimus of 1,000 parts and 5 month lead times.

The Up side to all this is the price, they are less then $1/each if ordering from stock. Down side, they only stock some options with the smallest nut size being 8-32. That is why I ask, are 8-32 to big for attaching the wing tips?

I have not started my wings yet, so I have the time to put in a custom order, but I don't need 1000 plates. I suppose, if a group were interested, we could pool together an order.

Now I am not a chemist or structural engineer, I know there are those that would advise not affixing the fasteners (plates with nuts welded to them) with adhesive, but I love the idea of not riveting these in place.

Thoughts?


I have gone the clik-bond route with 6/32. To keep costs down I used 2 ordinary floating nutplates for every clik-bond nutplate. I managed to reuse the clever blue silicone fixturing devices by re-stuffing them into the floating nutplates.

Both installation surfaces should be roughed up and clean. No epoxy gloss should be evident in the wingtip. Adhesive oozes up through the rivet holes.

Longevity in the field remains to be seen.
 

Attachments

  • IMG_1427.jpeg
    IMG_1427.jpeg
    189.6 KB · Views: 161
Last edited:
If I have access during construction I will snap a riveted nut plate in place and NEVER use something that can come loose and make my life a real disaster in the future trying to get a screw out.
Been there done that with Riv-Nuts and such.
My luck varies with life.
Art
 
I have gone the clik-bond route with 6/32. To keep costs down I used 2 ordinary floating nutplates for every clik-bond nutplate. I managed to reuse the clever blue silicone fixturing devices by re-stuffing them into the floating nutplates.

Both installation surfaces should be roughed up and clean. No epoxy gloss should be evident in the wingtip. Adhesive oozes up through the rivet holes.

Longevity in the field remains to be seen.


OK, I'll bite...*why*? If you *can* use riveted nutplates, why use Clik-bonds only every 3rd one? If there's a problem with either one (not saying there is), you've got the worst of both worlds.

Riveting them works just fine, and is a helluva lot cheaper to boot. This makes no sense to me.
 
Thank you for all the responses!

Thank you all for your thoughts! You have me rethinking, and leaning to riveting with a thin backer strip. Does anyone have a picture they would not mind sharing?
 
When I bought my plane the wingtips were riveted on. I bonded these 6-32 screw mounts. I run a 1/4" pinstripe tape down the edge of the joint between the wing and the wing tip. It covers the screw heads and make a nice pinstripe at the intersection of the wing tip. When I need to remove the tips I just heat the tape with a hat gun and peal it off.

https://www.mcmaster.com/90611A320/
 
When I bought my plane the wingtips were riveted on. I bonded these 6-32 screw mounts. I run a 1/4" pinstripe tape down the edge of the joint between the wing and the wing tip. It covers the screw heads and make a nice pinstripe at the intersection of the wing tip. When I need to remove the tips I just heat the tape with a hat gun and peal it off.

https://www.mcmaster.com/90611A320/

These are better than platenuts how?
 
If you worry about mis drilling the many holes to install the nutplates , I would recommend to use the floating nutplates . I was advised by an engineer working at some specialized company in Mojave that they only use floating nutplates because the they will salvage the hole even if you misdrill it. I used the regular nutplates on the wingtip but I had to replace a couple regular ones with the floating types because of the misdrill.
 
Embedding the bonding fasteners in fiberglass

Just a thought, epoxying on a thin aluminum backer plate before riveting on the nut-plates, has me wondering if there is much difference in effort embedding the bonding fasteners (not nut-plates) in a layer of fiberglass. I mean to epoxy the aluminum strip, one has to prep the tip, same as adding a new layer of glass to embed the fasteners. I am just taking about effort. I get that the real concern is a plate coming loose after the tip is mounted. However, would embedding the bonded fastener in a layer of glass provide better strength in this regard? I suspect testing would help answer that question, but there must be known torque limits. Are the click-bond failures due to installation error, or a problem with the solution. When they do fail, there is nothing left to hold it in place. With the fastener embedded in glass, there may be more to help. I especially like the size of this bonded fastener, as at 38mm long would have a long area to manage the rotational force.

3c0e36d61827283068aadb6c9f82884b.thumb.png


Then again, is the real issue with bonding these and failures due to the rotational forces, or the downward forces that is needed if the nut is not "seasoned". I guess one should not have to provide to much downward force when removing, especially with a hex or torx head.
 
Last edited:
These are better than platenuts how?

I never claimed they are better, was just supplying the OP with my solution. However, since you asked I have thought about it and determined they are better for a few reasons:

1. Bonding is the preferred attachment process with composites.
2. Rivets in fiberglass loosen with use.
3. They take less time to install.
4. They are 1/10 the cost.
 
When I bought my plane the wingtips were riveted on. I bonded these 6-32 screw mounts. I run a 1/4" pinstripe tape down the edge of the joint between the wing and the wing tip. It covers the screw heads and make a nice pinstripe at the intersection of the wing tip. When I need to remove the tips I just heat the tape with a hat gun and peal it off.

https://www.mcmaster.com/90611A320/

Thanks for the link, yet another interesting option.
 
Can't recall what I paid, but I bought a couple bags of 50 floating 6-32 nutplates at one of the booths at Oshkosh one year - couldn't have been much more than $25 or so. They worked great, and I used soft rivets to rivet them to the fiberglass - don't need to squeeze too much. I think I followed up with a dab of epoxy on each rivet.
 
4. They are 1/10 the cost.

McMaster part, "$19.97 per pack of 50", or 40 cents each

ACS K1000-6 51 cents each

They are *8/10* the cost, not 1/10. A savings of 11 cents per unit.

Oh, and per MC

"These nuts have three mounting holes to accept screws and rivets.", not epoxied.
 
Last edited:
Can't recall what I paid, but I bought a couple bags of 50 floating 6-32 nutplates at one of the booths at Oshkosh one year - couldn't have been much more than $25 or so. They worked great, and I used soft rivets to rivet them to the fiberglass - don't need to squeeze too much. I think I followed up with a dab of epoxy on each rivet.

I am now thinking the floating nut-plates are the way to go. :) The slight shift that may happen during installation should then be no problem. rv8ch did you also put in the aluminum backer under the nut-plates? I am just not sure how that helps. Is it spreading the forces to help with potential cracking?
 
I am now thinking the floating nut-plates are the way to go. :) The slight shift that may happen during installation should then be no problem. rv8ch did you also put in the aluminum backer under the nut-plates? I am just not sure how that helps. Is it spreading the forces to help with potential cracking?

Just looked at some old photos, and I didn't use an aluminium backer - just riveted the nutplates right on the fiberglass, carefully and slowly.
 
I used an aluminum backer underneath the fiberglass tip because the fiberglass is very thin. The aluminum strips provide the majority of the support for the nutplates.
 
Back
Top