Tie Down fitting ideas

[RhinoDrvr]

I’m sure everyone knows this already, but I didn’t.

At least on the RV-8, there are threaded spots in the baggage compartment for the tie down rings. I assume this is so they can do double duty to secure loose baggage during flight, then the airplane on the ground!

[Taltruda]

Originally Posted by Glen P

I'm looking at tie-down ring options and I was surprised to find that my -7 QB wings are threaded for 5/16" bolts so the rings from Van's and Cleaveland won't fit.

I wonder if someone tapped them 5/16 and don’t have full thread engagement? Or possibly used Helicoils to bring them down to that size? Either way, that’s odd..

[rvbuilder2002]

Originally Posted by lr172

Not a structural engineer, but I would be concerned with those alum rings. It looks like 1/8 X 3/16" at the thinnest point. I struggle to see how aluminum of that size could hold up to the loads imparted during a strong blow from a T storm. The plans use 3/8" dia steel, threaded into a .5 X .5 X 6" chunk of alum bolted directly to the thick part of the spar. At least they did on the 6 and the 10; cant speak to the 14. Hard to tell from the pics, but look like it is using thin support material rivetted to a thin wing rib, possibly tied into the thin spar flange. This appears WAY less structurally sound than what Vans designed. Certainly not saying it won't hold, just saying that it seems substantially under engineered comparied to the original design.

I agree with Larry.

There is a reason that the tie down anchors on RV's are designed the way they are.
The small cross section area of the small rings will be way deficient by comparison.

Keep in mind that when you really need a tie down to work, the load imparted can be quite high.

[MacCool]

Originally Posted by RV8JD

Should have said so in your first post.

Anyway, here is a fairing set designed to be used with the Cleaveland tie down rings I linked in my Post #4. Easy on and off.

https://www.rvplasticparts.com/produ...wn-fairing-set


Attachment 26256

I have those Cleaveland tie downs and leave them on all the time. If it had been me, I'd have been just as happy with the rings. I did remove the Cleaveland item from the tail and replaced it with a ring in order to mount a Go Pro.

If I ever need to jack up the airplane such as at condition inspection, I replace the wing tie-downs with some grade 5 carriage bolts to use as jack points.

The previous owner of my plane apparently knew Scott Melton here and put on a pair of those, as well as other 3-D printed items. I have similar fairings for the sump drains, and fairings for the flap struts. They're secure, but don't really take paint well and look a little rough.

No clue about the aerodynamic effects of the Cleaveland tie downs and the 3-D fairings. I'm sure that there's no downside, not sure if there's any benefit.

[David Paule]

Originally Posted by rvbuilder2002

....Keep in mind that when you really need a tie down to work, the load imparted can be quite high.

When I determined that wingtip tiedowns could overload the spar on an RV-3B, I was using 70 mph winds to assess that. Remember, that's based on RV-3B geometry which differs a bit from the other RVs. But the 70 mph is roughly what was encountered at Sun N Fun not that long ago, and LESS than I've personally experienced at Boulder, CO in '81, standing next to my C170, which was tied down.

Loads can indeed be quite high.

Dave

[Alchemist]

we made ours out of stainless, serves as a tie down and a jack point.

[spstout]

Originally Posted by KenB

This is the first good reason I've seen so far for covering those holes. Well, unless you're a homeless mud dauber.

One of those little demons got into my house last week. I really don't want one living in my airplane!

[gregfuess]

I'm thinking, without knowing any better, that when Van's says to remove the eye-bolt tie-downs before flight, that's what it means.

So I'm wondering if these would stay in place when the eye-bolts are not screwed into place, as in when flying?

https://www.widgetco.com/hole-plugs-...IaAhUKEALw_wcB

[mr.sun]

I ordered two titanium threaded ring bolts with the right threads, cut it to length, put a rubber washer on to protect the paint and just leave them on. Saved weight and increased bragging rights.

[Webb]

Why not grind some of the trailing edge off and make it the classic tear drop pressure recovery shape?

As robust as the standard Vans rings are, I think they would still be sufficiently strong enough to do their job.

That’s what my plan is and I plan to leave them in place. I don’t like the idea of wear on the aluminum threads from the steel threads that would occur over time from repeated insertion/removal or an invitation to mud daubers.

As a bonus, if a person could find some type of rubber wheel shaped like a tire rim to leave in place when not in use, it would look and act like wheel pants. Or even two buttons that could be easily separated by using something like magnets. Make each button from 2 hole saw circles. One to cover and one slightly smaller to prevent movement. JB Weld a button magnet on one side and washer stack on the other. When needed, easy to remove.

It would be a 9 to 1 reduction in drag if you use the round to teardrop methodology. Hey, a speed mod!