Saturday, August 28, 2010

Zipline Tree Platform

Finally finished building the tree platform today.  As usual, half the time was spent working on it, and the other half was spent looking for tools and making yet another trip to Home Depot.  It is rather small, only about 5'6" ft wide at the end and about 5' long.  And some of the floor space is eaten up by the big hole I left for the ladder.  But I think this means of access is safer and I really don't want a lot of space up there anyway.  Enough for 2-3 people max is all I wanted.  Plus, with a cantilevered design, I was concerned about snow loading, but this should be fine.

The maple tree also takes up a lot of space since it comes up right through the middle of the platform.  I didn't even cut off the branches even though they're in the way.  Those branches have a lot of leaves on them that help to hide the platform, so I'm keeping them.
You can see the tree plaform...or actually you can't because of the tree limbs I saved

View from the bottom - the deck is 21 feet off the ground
View of the platform from above
3/4" bolts anchor the main braces to the tree

The platform was built using pressure-treated 2x8's.  I originally anchored these to the tree with 1/2" bolts but those are not really beefy enough.  Plus I broke two of them off in the tree when tightening with a breaker bar because I hadn't drilled the holes out big enough and this is an oak tree.  So I ordered 3/4" bolts, 8" long (you can't buy these at Home Depot or other stores, the biggest they carry is 1/2" stuff). 3/4" bolts are huge - they're actually twice the size of 1/2" bolts (do the math).  You have to get a long 5/8" drill bit to drill out the hole and also a 3/4" drill bit for the first 3" or so that is not threaded.  I actually took the 1/2" bolts out,  drilled the holes bigger and put these 3/4" bolts in there.  The whole thing was really stiff after I did this.

Framing it out was a bit of a pain because of all the bizarre angles. For example, the main braces are tilted at angles because the tree leans slightly. Finally, I used 3/4" plywood for the decking (just because I already had it in my basement) and it is really solid. This helped to stiffen the whole structure.
From the duh ground looking up the ladder
Plenty of room for the small maple tree
View from the platform looking down
View from the platform, looking down the zipline
DIAPERS RECOMMENDED (I wear them anyway)

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