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Tie down ring specs


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I would hazard a guess no one will know this one. You may have to call FD and they probably won't know either. If the wind is that strong it will most likely be tornado or hurricane strength. You will probably have the ground anchors pull out first like many planes at Sun'n Fun had happen. When winds get that strong all bets are off.

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Roger,

 

Someone ought to know. When I go to a hardware store, chain has a load rating, which of course we need to know if it is used for something like holding down cargo on a truck.

 

I was looking into a tie-down system and of course one thing that went through my mind was the chain tie downs that are sometimes used in the West. Sometimes these are set in concrete. So, it is by no means obvious that in all cases the anchors or rope/chain will break before the tie-down ring.

 

At the same time, I got to thinking that even if one used log chain, it is not very useful to use tie downs that exceed the capabilities of the ring. When you get to thinking about it, the ring is not very big and not very massive. I broke a chain on the farm the other day. Chain links break.

 

An airport I flew into recently had no tie down ropes because of liability concerns, and I've seen that situation in other places, as well, so it behooves us all to have some tie-downs with us in the planes, especially something as light and subject to winds as an LSA. So, while I'll likely get a Claw or the alternative thereto, for when there is no anchor, I'm also looking for a light and strong tie-down system and I was even considering light chain when this question came to my mind. As we all know, the junk rope we get in local hardware stores is very weak and even nautical line isn't always of sufficient load capacity to hold an airplane in let's say a 50 knot gust.

 

Rope load strength by itself is fine, but when we tie a know or otherwise use it in some way other than a straight pull, we weaken it. So, if a person puts a fitting on the end of the rope and terminates it in some kind of a hook or latch to fasten to the tie-down ring on the wing, one still has to wonder what the ring will sustain.

 

 

 

 

 

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Roger,

 

Someone ought to know. When I go to a hardware store, chain has a load rating, which of course we need to know if it is used for something like holding down cargo on a truck.

 

I was looking into a tie-down system and of course one thing that went through my mind was the chain tie downs that are sometimes used in the West. Sometimes these are set in concrete. So, it is by no means obvious that in all cases the anchors or rope/chain will break before the tie-down ring.

 

At the same time, I got to thinking that even if one used log chain, it is not very useful to use tie downs that exceed the capabilities of the ring. When you get to thinking about it, the ring is not very big and not very massive. I broke a chain on the farm the other day. Chain links break.

 

An airport I flew into recently had no tie down ropes because of liability concerns, and I've seen that situation in other places, as well, so it behooves us all to have some tie-downs with us in the planes, especially something as light and subject to winds as an LSA. So, while I'll likely get a Claw or the alternative thereto, for when there is no anchor, I'm also looking for a light and strong tie-down system and I was even considering light chain when this question came to my mind. As we all know, the junk rope we get in local hardware stores is very weak and even nautical line isn't always of sufficient load capacity to hold an airplane in let's say a 50 knot gust.

 

Rope load strength by itself is fine, but when we tie a knot or otherwise use it in some way other than a straight pull, we weaken it. So, if a person puts a fitting on the end of the rope and terminates it in some kind of a hook or latch to fasten to the tie-down ring on the wing, one still has to wonder what the ring will sustain.

 

 

 

 

 

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I doubt it is a chain or tie down ring issue. My guess it will pull out of it's threads before that metal ring breaks. I still believe if your in that much wind it's going to be a tornado or hurricane force and all bets are off.

 

A system is only as strong as it's weakest link and I don't think the actual ring itself is it.

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I doubt it is a chain or tie down ring issue. My guess it will pull out of it's threads before that metal ring breaks. I still believe if your in that much wind it's going to be a tornado or hurricane force and all bets are off.

 

A system is only as strong as it's weakest link and I don't think the actual ring itself is it.

 

Until we know the strength of the tie down ring, we are just making assumptions and guessing. For example, I'm pretty confident that if I tied the CTSW down with 3/8" grade 70 chain hooked to heavy anchors set in concrete, the ring or it's fastenings would be the weakest part of the system.

 

 

I sent Arian an email and asked him to check with FD. When he reports, I'll pass it on. Then we'll all know.

 

 

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  • 1 month later...

What is critical, though, to how much load the rings take is the angle of the wind and the position of the tail. Wind on the nose is worst of course because the plane wants to fly, but if you push the elevator trim all the way forward (which I always do in gusty conditions), then it wouldn't even at 100MPH. With alot of back trim, like for take off, you could see 600lb of net lift force (with empty tanks) at just 50MPH on the nose, 300lb per rope. Trim pushed forward, it will just dig the nose in. In between, (it's hard to say bacause I haven't tried this) but, with only modest back trim like for TO or landing, it would probably be more like 90MPH before the plane would fly which also would be equivalent to 600lb of net lift of an empty plane.

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My guess it will pull out of it's threads before that metal ring breaks.

 

Nope. General rule of thumb is that a threaded fastener is as strong as the surrounding material when you have 1.5 times the diameter engaged. I agree that the limitation would probably first be a bending failure from the force being at an angle, followed by the female part failing at it's attachment to the composite structure.

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I seriously doubt the threads or shaft of the tiedown ring would fail. That would be at 2000lb or something. The failure would be the 'helicoil' sort of threaded sleeve that must be glued into the spar ripping out. My WAG is somewhere around 300lb that could pull out. Pulling the stick full back would be the worst possible thing. Cessna and Piper have the right idea. A yoke lock will hold the tail slightly forward.

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