markshancock@hotmail.com

We live in a neighborhood at the top of a hill in Connecticut and are surrounded by trees. Our lot is about 1 acre and most of the trees are 40 ft high (a guess) hemlocks - more of them than I can count.

We have two boys (4yo and 6 yo) and they really like swinging so I thought why not build a "swingset" in the backyard by running a beam between two of the trees supported by lag bolts and hanging the swings from that. It would take up no yard space, be cheaper, easier (I think), and act as a beginning point for the tree fort I have been dying to build them.

Have any of you tried something like that before, or generally got some advice. I can figure out how to know what type of structure I need to support a static load but I'm not sure what type of trouble I me be getting myself into with the dynamic load a boy swinging (actually boys) will create. Swingsets seem pretty simple but they do always have the angled support posts that probably support the stress from the horizontal forces of swinging. I am concerned that swinging could pull the lag bolt right out of the tree and I wasn't sure if drilling a hole fully though the trees (10" diameter) and putting a support on the other side was a good idea or not since the trees are still growing. Also, we do have high winds from time to time (but not often) so there could be some relative motion between the trunks.

Thanks,
Mark

Square Eye

Keep talking and you wil realize that permanently mounting anything to a living, still growing object is NOT a good idea. As you seem to be speculating, anything could, and will likely go wrong. Growth patterns will not be exactly the same between the two trees even though they're side by side. Soon the growth of the tree will swallow the bolt or the reaction of the metal to the sap and constant moisture will cause the bolt to rust and fail.

Tree swings are meant to be tied loose (with room for the tree to grow), on a limb that is far enough away from the trunk to swing freely, and with rope that doesn't cut into the supporting limb. Nylon twist will strip the bark off and leave the limb exposed to infestation and will cut short the life of the limb. A soft braid is better for the tree and the larger the diameter, the better.

A tree grows by forming a cellular network of tunnels every year as the moisture from the ground is absorbed through the roots and makes it's way up the tree just under the bark. The more moisture and sunlight, the larger the cellular structure. Then winter comes and the structure hardens, the tree kind of dries out and becomes dormant. Then it all starts over again the next spring. A rope too tight, a puncture wound, a bolt through, any of these can disturb the life and health of the tree.

Hardwood trees are better for swings, Oak, Hickory, Walnut, Pecan.
Softwood trees are likely to be damaged by having anything attached.

Hemlock is a softwood, stronger than Spruce, lighter and much weaker than Yellow Pine, which is also a softwood. It's more comparable to Fir, another softwood.

Yadda yadda yadda, they're your trees. Do what you want. If you have plenty of trees to keep you happy, enjoy what you can from these.

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