Results in for Ultralite Tree Pro (Tree Protector) straps.

[GT]

But that is not the goal with a 2" strap. The goal is to distribute the weight born by the tree.

1/2" folds at 45* do not accomplish that.

A 30* fold might.

Bar tacks in 1" straps running several inches into the 2" material do not contribute to anything but final weight.

Not sure that I get your meaning. The 2" strap is 4' feet long and goes around the tree with the 1" fed thru the eye of the 2" strap. The tree is carrying the weight, no? I can understand if the 2" strap was say, 1 foot long and didn't completely go around the tree, but a 4 or even a 3 ft strap will easily wrap completely around. If you have trees bigger than that, order a longer 2" piece.

[MDSH]

One has to follow the forces exerted on various elements of the system.

In your design the 2" material serves only the purpose of appearance. Load is distributed only through the bar tacks to the width of the bar tacks.

It breaks at the point described because the tacks at that point are elongated by the layers of material that they have to span (and because the tacks actually damage the weave at that point).

At the other points (where it does not break) the bar tacks are assisted by friction where the pieces join.

The folds at the first bar tack in your system actually mitigate against said friction.

You have only a < 1" inch system.

If the 2" material was folded and tacked to the 1" strap then the fibers would sort out the load to the tree and friction would assist in transferring the load from one point to another. A strong thread tension would be your best bet in such a joint. And bar tacks are not the strongest joint. The W is better.

[GT]

One has to follow the forces exerted on various elements of the system.

In your design the 2" material serves only the purpose of appearance. Load is distributed only through the bar tacks to the width of the bar tacks.

It breaks at the point described because the tacks at that point are elongated by the layers of material that they have to span (and because the tacks actually damage the weave at that point).

At the other points (where it does not break) the bar tacks are assisted by friction where the pieces join.

The folds at the first bar tack in your system actually mitigate against said friction.

You have only a < 1" inch system.

If the 2" material was folded and tacked to the 1" strap then the fibers would sort out the load to the tree and friction would assist in transferring the load from one point to another. A strong thread tension would be your best bet in such a joint. And bar tacks are not the strongest joint. The W is better.

Yeah, right. Whatever you say.

[Firesong]

I agree with you RSGary, you method should make it easier on the trees.

[MDSH]

My dad was an architect, Gary, who explained to me the distribution of loads through elements in the construction of a building system. I have actually seen the engineering tables upon which he relied in buildings that have no cracks or leaks.

The sheer strength of nails, for instance, must comport with the dimensions and spacing of framing members. The same principle applies to sewn materials.

[GT]

My dad was an architect, Gary, who explained to me the distribution of loads through elements in the construction of a building system. I have actually seen the engineering tables upon which he relied in buildings that have no cracks or leaks.

The sheer strength of nails, for instance, must comport with the dimensions and spacing of framing members. The same principle applies to sewn materials.

All I know is that I am getting over 1300lbs out of a webbing that is rated by the manufacturer for 1100lbs. I would consider that satisfactory.
As far as the load being place on the tree itself, I would imagine that it would be equal to the weight of hanger and equipment in dead weight. Unless of course you're jumping around in it then it would be a little more. And besides, I think the problem is damage to the outer bark which is why rangers want to see a 2" strap rather than a narrow strap or rope.

[MDSH]

Your argument is not with me, Gary, but with government officials that might require 2" straps. They presumably care for trees more than your bottom line and probably know less about it than any of us, though their jobs depend more on political appearance than 2500 years of science.

Heck, I intend to hang from Dynaglide where permitted.

But when 2" straps are required ...

I'd be willing to go to court over the 2" polypro tree huggers I'm making at 3.5 ounces.

[nothermark]

I think the forces will spread across the 2 inch strap within a couple of strap width's of length. The cross wise threads of the weave will act like beams to spread the load. The low load part would be the edge flaps along the 1 inch overlay where it is stitched.

FWIW I like these for even big trees. By the time one deploys 4 ft of 2 inch there is ~ 80 sq in spreading the load so the weight per unit area is getting down. 1 inch strap to lengthen further reduces the load/unit area on the tree. Figure the same strap on a 6 inch tree would have less than 20 sq inchs bearing the same weight.

[ksbcrocks]

Imagine instead of straps, you were constructing this out of 2 inch and 1 inch strips of T-shirt like material that wouldn't break. If you were to put it up on a tree and attach a hammock to it, would the 2 inch section show stress and be pulled tight along the whole width? Or would only the middle 1 inch take most of the stress and the edges be loose? If the latter is the case then the strap is effectively acting as only a 1 inch strap as far as force per square inch on the tree bark. I believe this is the point MDSH is trying to make. I don't know if the current design is distributing weight to the entire width of the two inch section or not.

[MDSH]

I think the forces will spread across the 2 inch strap within a couple of strap width's of length. The cross wise threads of the weave will act like beams to spread the load. The low load part would be the edge flaps along the 1 inch overlay where it is stitched.

Yes, a couple of strap lengths at least ...

IF, a big if, the sheer of the bar tack can hold.

But it does not, apparently.

The three elements must work together: 2" material, fastener, and 1"material.

Imagine instead of straps, you were constructing this out of 2 inch and 1 inch strips of T-shirt like material that wouldn't break. If you were to put it up on a tree and attach a hammock to it, would the 2 inch section show stress and be pulled tight along the whole width? Or would only the middle 1 inch take most of the stress and the edges be loose? If the latter is the case then the strap is effectively acting as only a 1 inch strap as far as force per square inch on the tree bark. I believe this is the point MDSH is trying to make. I don't know if the current design is distributing weight to the entire width of the two inch section or not.

Exactly.

As a practical matter we're wanting to pinch down 2"of load distribution at the tree to 7/64ths or less.

There has to be some graduation through thicknesses to accomplish that.

A relatively abrupt change in forces at 45* where the strap goes from 1 to 2 inches will be the weakest point. Too much depends on the bar tack.