Question regarding a possible mod of Rabbit Ear Stand

[latriper]

I have been thinking about trying the rabbit ear stand and noticed some have had cracking/splintering issues of the 4x4 base. I have made and used the turtle dog stand with good results but would like to try the rabbit ear stand for inside the house. An idea floated around inside my NON engineering brain and would love some feedback whether this would help at all or is it totally worthless. Hopefully the picture will explain my thinking but basically it utilizes one piece of amsteel from one "ear", ran down and under the 4x4 along a channel that has been cut out and back up to the same position on the other "ear". My thinking is that when the hammock is loaded, the force of the "ears" pulling together would be somewhat offset by the opposing force of the Amsteel. Thanks!

[DavyRay]

Your sketch is quite correct in dealing with the forces. The only problem is getting the right tension on each section of cord. That would be a challenge.

From what I have read, the biggest problems with the original design is getting the right diameter holes cut into the 4x4 piece, and in getting a 4x4 which does not have structural flaws.

[latriper]

The only problem is getting the right tension on each section of cord. That would be a challenge.

Thanks for the reply DavyRay. I was thinking in terms of distance between attachment points. With one continous length of Amsteel (very low stretch) attached to each "ear" and just having that tight but not necessarly pulling against an unloaded hammock, it would keep the "ears" from moving toward each other when the hammock was loaded. More of an additional anchor instead of just relying on the angle of the pole in the 4x4.
I know what I am trying to say but I am not sure my writing is conveying it

[jlink79]

This would help reduce the moment about the point where the poles go in. A moment is the rotational force at an anchor point between 2 pieces. The best way to reduce this with wood is lamination.
1: use 3 to 4 boards laminates side by side the middle board(s)are cut to leave a hole/pocket the desired angle for the poles. A piece of wood that is as hard or harder than the frame is placed and glued in the pocket 90° to the laminating both for and aft of each hole this will help spread the force along the pocket instead of at the ends due to the rotational moment. The lining or shimming of a mortise and tenon joint is an old way of strengthening the joint.

[perchancetodream]

The horizontal force vector of the hammock pull on the free end of the rabbit ear is approximately .87 x Your Weight for 30 degree hang. If the rabbit ear bends enough to move the rope say 5 degrees from vertical, the tension needed to stop it from rotating would have to be about 10 x Your Weight at each rabbit ear, which is to say the total rope tension will be 2 x 10 x Your Weight! Extending the ends of the beam so that the rope is not vertical would work reduce this load. Beam extensions long enough for the rope to be pulled at 45 degrees to the beam would reduce the tension to 2 x 1.2 x Your Weight. However, this does defeat the compact advantage of the rabbit ear design.

[gmcttr]

You can use a turnbuckle to pretension the amsteel.

[f k]

You can use a turnbuckle to pretension the amsteel.

Yeah those would be the best solution I think. Been thinking about making one of these as well and the cracking issue had been brought up in another thread. I think the idea of the amsteel on the ends will do the trick.

[latriper]

I appreciate everyone’s response but I don't think I have adequately explained my idea.
In one responses,

The only problem is getting the right tension on each section of cord. That would be a challenge.

there seems to be the idea that I was talking about sections or individual pieces of Amsteel. This may be the best idea but my original thought was one length of Amsteel running from one ear down and under the 4x4 and up to the top of the other ear. Kind of like what the top rail does in a turtle dog stand but from the opposite direction. Or, like the rope anchors driven into the ground to secure some BI-pod stands. In my sketch, the dotted line was drawn to indicate that that area of Amsteel would not be seen, not that it was a different piece.
Also there was a formula mentioned

If the rabbit ear bends enough to move the rope say 5 degrees from vertical, the tension needed to stop it from rotating would have to be about 10 x Your Weight at each rabbit ear, which is to say the total rope tension will be 2 x 10 x Your Weight!

which sounds logical, could the solution be a higher tensile strength Amsteel? Like 1/2 inch or 3/4 inch (which has a much higher tensile strength) and leave the length of the 4x4 the same.
Again, I have no background in engineering which I'm sure is painfully obvious so please keep that in mind if this all seems quite ignorant.

[gmcttr]

... could the solution be a higher tensile strength Amsteel? Like 1/2 inch or 3/4 inch (which has a much higher tensile strength) and leave the length of the 4x4 the same...

1/8" (2500 lbs avg breaking strength) or 3/16" (5400 lbs avg breaking strength) amsteel blue would do the job.

Because of your narrow angle between the pipe and amsteel, the amsteel will need to be pretensioned as a 1/4" of slack in the amsteel will result in a much larger movement in the pipes.

When making the rope support, keep in mind that the amsteel will lengthen the first time it is loaded. This is due to the braiding and splices taking on their final set and not actual stretching of the fibers. A turnbuckle on one end will give you a little more room for error in the length.

rabbit ear stand idea.jpg Rabbit Ear Stand Corner Detail.jpg

[f k]

I echo what gmcttr said. Pretensioning is the way to go.

... A turnbuckle on one end will give you a little more room for error in the length.
rabbit ear stand idea.jpg Rabbit Ear Stand Corner Detail.jpg

Plus it will allow you to actually connect the rope supports. Without that, getting the rope on any kind of attachment that will not slip, with any useful tension, might be pretty tough, and also difficult to disassemble.

gmcttr, bolts in the ends are a good idea.