will an eyebolt through a branch hurt the tree?

iphotostuff

I have a really old Oak in the front yard that seems to be in pretty good shape. I want to put a rope swing on it (single rope) and came across this video from "this old house" that recommends putting an eyebolt straight through the branch instead of tying the rope around the brand because it will "kill it." This doesn't make sense to me, so I appeal to your expertise. The branch I am thinking of using is about 12 inches thick and the eye bolt wouldn't be completely vertical, more like a 45 degree angle if it's perpendicular to the branch. Also, I don't think I could get a bolt long enough, so the bolt may just screw straight into the brand for a few inches not all the way through with a nut on the other side as recommended in the video.

Any advice? Something seems extremely wrong to me about putting a huge piece of metal into the branch, but at the same time, I think my son would just love swinging on a great long rope from this tree and since there are no low branches for climbing I'd like him to start "interacting" playfully with trees in this way. Advice about how to do this without killing the tree would be MUCH appreciated!

Garry Brockley

try this thread
want to build a swing between two trees

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Eric Frei

My comments in green.

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TreeSpecialist

Use a forged eye bolt heavily galvanized - minimum 1/2 inch in diameter backed up with similar quality washer and nut.

The hole through the limb is not nearly as damaging as a "tourniquet" wrapped around the limb.

You might want to further support the limb by installing a cable on the limb distal to the rope swing.

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The Tree Whisperer

Although this can be done and you will probably not notice any significant injury or damage in the short term a key point to remember that any cut including drill holes etc is in fact creating a wound in the tree that would not other wise be there. This wound can and often does become a site for decay and ultimately becomes a weak point in the branch. I recommend that use a stainless steel threaded eye bolt and if possible avoid going right through the branch as this in effect will create 2 wounds.

There are other methods of cabling and bracing available now such as the Cobra TM system. the whole reason this was developed was as an alternative to drilling into the branch and placing bolts and such in trees.

Try to find a non invasive method of attachment if you can and EKKA is right in agreeing tying off around a branch will eventually kill the branch as it will constrict and cut of vascular connectivity.

Eric Frei

There's an engineering issue with this approach, the direction of loading is inline with the thread. Unlike say putting a coach bolt into a fence railing where the load is trying to shear the bolt.

What happens here is the rating of the bolt/thread is irrelevant as it's now up to the integrity of the timber, which you have mentioned yourself can decay. So in a few years time a kid is swinging merrily away and the bolt pulls out, child crashed and sustains spinal injuries all because you didn't want to drill through.

A through bolt is loaded inline but has it's rating, the only way it can fail is the nuts strip or it pulls the whole bolt assy through the limb (including the washer), highly unlikely and a better bet than relying on a thread in wood.

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Brent Ferris

I agree that an eyebolt thru the limb will be the strongest. If worried about nut and thread failure, use a double nut with a lock washer between.. i would use a 5/8 or 3/4" eyebolt, and they are available up to 18 inches long, so getting one to reach thru a 12 inch diameter limb should be no problem. I suggest drilling from the top down so that the bolt will be in line with the force.

Wrapping a rope around the branch usually kills the branch. It is like tying a tourniquet around one of your limbs to hold broken bones together. THe sap flow (in your case, blood) stops, the leaves can't get the water and nutrients from the roots, and the limb dies. (in your case, the limb gets gangrenous and needs to be amputated). Only the time line is different. A pin becomes part of the system.

BUt I would wonder if having a swing from a tree is so important to permanently damage part of a mature oak. WHile swinging on a long rope seems like a great way to interact with trees, I am afraid that your son will learn that you can't hurt trees, and you can do almost anything and they just keep on living. And that is not so.

The Tree Whisperer

IN a FEW YEARS TIME BRANCH DECAYS BOLT PULLS OUT BRANCH FAILS KID CRASHES DAMAGES SPINE AND GETS BRAIN INJURY THEN BRANCH FALLS AND CRUSHES KIDS HEAD CHEST AND TINY LITTLE BODY ALL BECAUSE YOU DRILLED THROUGH.
READ THE LAST PART OF MY POST I SAID TRY TO FIND A NON INVASIVE METHOD

EKKA I didnt know you were such a highly qualified structural engineer !!!!!!

The one thing I like about you mate is that you are so arrogant to believe that you are never wrong!!!! Its a good trait to have

kiddalaska

Easy now. No need to get touchy. I am an engineer. I am not an arborist. I get EKKA's deal. I'm building a zipline and a swinging bridge to be attached to a very large doug fir. I want to know how much it can hold. The wood is a big unknown. I don't want to hurt the tree though, and there's no way I'm drilling through it (it's three foot in diameter). I'm thinking about wrapping chain or cable around the tree but protecting the tree from being completely strangeled by placing 4x4's around it in an octogan or hexagon shape. This would put 6 or 8 (whatever I can get away with as a minumum) compressive point loads on the tree. If the diameter is roughly 10 ft, this would amount to a maximum of 27% of the trees cirumference being impacted. Do you think this is more than the tree can bear?
THANKS!

Eric Frei

LOL, and another typical extremist ignorant attack. <yawn>

Errr, how many cables have pulled out in in the decades the yanks have been using eye bolts?

Errr, how many nails have you chainsawed and the wood around it was fine?

Seems some do not understand compartmentalisation nor decay prevention, lot easier to attack people than seek knowledge.

Seems the arrogance comes from being so ignorant, it is contagious too I assure you, fill a room with daft fools and they soon think they're geniuses to govern the world.

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Garry Brockley

The cambium is actually quite a delicate structure and if you compress it enough it will get damaged its like a tornequet around an arm and as the tree expands more pressure is applied, personally iwould say see if you can find another option

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Eric Frei

Many a tree hugger attempts non invasive methods to satisfy their nuances..... but not the tree's.

Nothing new in seeing blocks of wood or half Koppers logs around a tree with cable tensioned around that, I see it in lots of places, lots of ropes courses.... and there's lots that do not follow that practice and drill with more permanent yet serviceable results.

http://www.treeworld.info/f2/zip-lin...que-11121.html

Attaching tree swing

Oh and on the engineering front, I was a fitter/turner for 8 years so I have bit of an idea.

That poinciana branch in the picture above, you really thing it's going to pull through? You really think it's all rotten?

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TreeSpecialist

To Kiddalaska....

That's quite a tree - 10 ft in diameter!

Any thing placed around the tree will ultimately be damaging to the tree. The water conducting vessels in any tree lie just beneath the bark. Anything that impedes the flow of water and nutrients should be considered a negative.

As to the zip-line itself, over-engineer it. Most engineers (and I was going to be one at one time) build in a redundancy of as much as ten times actual load. Any hardware put into the tree should be placed so that it is loaded in line with the pull on the zip line.

A ten foot tree is too big to drill through and the expectant useful life of the zip line (the child's interest in such things) is relatively short. (It's not the kid you need to worry about - it's the adults who decide to try it after a few drinks.)

As far as what to use to attach it to the tree, go to:
Treehouse Engineering - Charles Greenwood PE. Recognized authority on the Engineering Analysis of Treehouses.

Charlie Greenwood, a professional engineer, has designed some serious hardware for trees. If he doesn't have what you need, I bet he could craft something appropriate.

I have seen the result of a few zip line accidents and it would be prudent to wrap the trees or posts at either end of the zip line with the kind of padding sold in sporting goods stores to protect basketball or football goal posts.

Good luck...... and don't worry about a hole or two being drilled into a tree. Eric's right - tree whisperer needs to do a little more homework. The tree didn't get that big without being able to significantly compartmentalize decay.

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Eric Frei

Thanks, and a great link with good resources.

We have custom made some specific gear for suspended bridges, some span over a 100', some people here do know and have seen it but as it is a restricted site and paying client I do not publicise it ..... keeping it as the clients/riggers IP.

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Eric Frei

http://www.treeworld.info/f2/zip-lin...que-11121.html

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