Modern Adirondack chair question (Tom McLaughlin’s plans/magazine/video)
chuckcoleman
| Posted in Joinery on
In the January/February 2019 FW magazine, there are detailed photo’s of building the “Modern Adirondack” chair. On page 39 in the magazine Tom shows using a 14 degree wedge when cutting the back seat rail. I understand the ends of the rail are cut at a 6 degree angle, (like the front seat rail), but for the life of me I can’t figure out what the need is for the 14 degree wedge. I’ve built the legs and mocked them up and it seems to me the wedge/compound cut on the ends, isn’t needed. The mortise slot in the legs is at 14 degrees, per the plans, but I don’t know why the back rail needs a compound cut on the ends. Any insight would be appreciated. Thanks.
Replies
It is needed, but as I found out when building a pair of the chairs, it is not 14 degrees (I can't remember what I worked it out to be though I think it was 5.2 degrees)
It is required because the sides splay AND the rear element is tilted relative to the ground.
If you think about it, you can see the problem. Imagine that your back piece is going to be totally horizontal. It will be longer at the front than the back because the sides are angled relative to each other so the front is further apart than the back.
Now, turn the piece so it is vertical, with the front at the top. The bottom is now too short to meet the sides because it was tapered to match the sides. If the pieces were perfectly cut bits of plastic or metal, only the front lower corners and their adjacent short edge of your piece will now be touching the sides.
The compound angle is needed to compensate for this.
You need to copy the angles of the intersecting planes, which is NOT an easy concept to get your head around.
The easiest way to see this in action is to make a test piece. I made these cuts on my compound mitre saw because that is what it does best. It is not an easily visible joint in the finished project so minor tearout on the ends makes no difference, and blue tape can fix even that...
There are a few other minor errors in the plans, including the thickness of the back pieces too - 3/4 inch is the right thickness.
Thank you very much. I need to digest what you said. I appreciate you taking the time to help me out.
Take care!
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