Tail strobe mount

[mratzburg]

While I was attempting to remove my tail strobe the lower #40 screw bound partway and snapped off in the nut. I attempted to drill it out with a left hand bit but was unsuccessful. It looks like the builder of my plane fixed a nut using some composite material.

I am considering a potential fix that I found in a thread from vans airforce circa 2007. Sparky suggested installing blind rivets and tapping them as a mounting solution. In my case, I'd only install a rivet in the hole that is broken. For those of you who followed this method did it stand the test of time? Other option is to get and install the alu doubler that is now called out by Vans.

Originally Posted by*Sparky*

I thought about all the great ideas on this thread, but in the end decided to do this my way...

1. Drill mounting holes in the rudder bottom fairing to #30
2. Install a couple of LP4-3 blind rivets, using 5-minute epoxy for added strength and to help keep the rivet from rotating
3. Punch out the rivet mandrels
4. Drill the holes in the rivets to #43 for 4-40 screws
5. Tap the holes in the rivets with a 4-40 tap
6. Mount the strobe/tail light using 4-40 screws supplied

This is a very simple, cheap, lightweight solution that seems to work very well.


[Raymo]

The professional version of this is to use a riv-nut but not many builders would have the tool to install them. You might find an A&P in your area and borrow his/her tool and a couple riv-nuts. (this is what I did).

https://www.youtube.com/watch?v=dkPhGIaPCVs

[lr172]

A rivet won't work well. Seems unlikely that it will have a bunch of metal left after tapping. Just make an aluminum ring out of 1/4" aluminum to fit on the back side of the f/g. Drill to size and tap. Then secure to inside with epoxy or JB weld. You can also make a small block of 1/4" aluminum for backing behind the damaged hole. Trim to fit area and clear light housing. Drill and tap then secure with epoxy or JB weld. It's like a nut plate. Doesn't need to be overly secure. Just secure enough to resist turning while tightening the screw.

Just be sure to coat threads with vaseline while epoxy is setting up. Lkely previous builder didn't do that and why you couldn't get the screw out.

The method you mentioned will have some ot the new thread made up from epoxy and will be very easy to stripe.
Larry

[rapid_ascent]

I bought a tail light mounting plate from Cleaveland Tools. It gets blind riveted onto the fiberglass, then you can just screw your strobe to the plate. See the link below. It may not be the cheapest solution, but it seems pretty clean to me.

http://http://www.cleavelandtool.com.../#.XK9ZNRplCf0

[mratzburg]

I don't think I'd be comfortable putting a rivnut in fiberglass - I already have enough problems with spun rivnuts on my airplane.

The version of the plans that Vans provided me on the USB stick indicates they are now selling a doubler similar to the Cleveland Tools plate (R-00911B.) I'm not sure when they introduced that but the drawing I have is dated 2015.

I think the first step is to carefully remove the nut that is epoxied in now - I do not want to damage the fairing. The comment that epoxy may have gotten on the the threads seems possible - screw was coming out nicely until it wasn't and then pop!

Thanks,
Mark

[lr172]

Originally Posted by mratzburg

The comment that epoxy may have gotten on the the threads seems possible - screw was coming out nicely until it wasn't and then pop!

Thanks,
Mark

new data. If you have enough screw thread protruding from the back of the nut, you can possibly get a curved needle nose pliers or needle nose vice grips (better) on it and rotate clockwise, driving the screw back into the cavity. You could then re-use that nut, as the epoxi si only on the screw, not the nut.

Larry

[Mike S]

Originally Posted by mratzburg

I attempted to drill it out with a left hand bit but was unsuccessful.

Originally Posted by lr172

If you have enough screw thread protruding from the back of the nut, you can possibly get a curved needle nose pliers or needle nose vice grips (better) on it and rotate clockwise, driving the screw back into the cavity. You could then re-use that nut, as the epoxi si only on the screw, not the nut.

Larry

You could also try a right hand twist drill, and see if you can run it back into the cavity like Larry said

[mratzburg]

Thanks, I'll try the right twist drill - I didn't have much luck trying with pliers or mini vice grips, can't get enough purchase.

I think I buggered the nut when I tried to drill it out - the nut apparently was made of softer material than the screw and my left hand bit deformed enough under pressure to find the path between the bolt and nut.

[Tim Lewis]

I drilled the two tail strobe mount holes a little over size, filled with JB weld, then drilled and tapped the holes in the JB weld. Has worked fine for 1100 hr and a few remove/replace cycles.