Wednesday, January 18, 2012

"Good idea" ...

One of my favorite lines from the movie, Never Cry Wolf. In the scene a puzzled Eskimo hunter comes across the environmentalist picking up wolf skat. The environmentalist explains that he is trying to figure out what the wolves are eating to stay alive. He tells the Eskimo, "what goes in comes out." The Eskimo replies, "Good idea." I love this movie and the story of the government sending this guy to study the wolves.

Years ago a fellow teacher used to take me rabbit hunting. I remember we would drive around after a new snow and look for a patch of woods to hunt. He stopped on the road and then backed up onto the shoulder to get off the road. This seemed odd to me. After the third time doing this maneuver  I asked him why he didn't just pull off the road like a regular person. He told me that the way he did it (backing in) made a set of tracks in the snow and a path for the tires to follow when pulling out so he would not get stuck in the snow. Good idea.

Now when it comes to cutting 1/2 dovetail notches in logs to make a log cabin I think you need a "good idea" or two. Oh, and maybe one of those Easy buttons from Staple too just in case. What I wouldn't give to go back 150 years to see, first hand, an original log cabin builder at work.  Bridgewright, Will Truax touches on this a bit on his Bridgewright blog but that is another story line. Back to log cabin building. Most things I have read are pretty scant on what I will call "the details". Most are using sawn timbers or pretty straight "Lincoln" logs.  So how hard can it be? Really!

As a youngster my buddies and I would scrounge the neighborhood for any scrap boards we could find. We built many a fine tree house. No plans, no measuring, just cut and nail. Too long cut it again. Too short, nail a piece on. No muss no fuss.

Using "Tree house" mentality this is what the logs for a cabin would look like.

Here's what the cabin would look like. Stack'em up and away we go. That was easy!

Are you thinking what I'm thinking? Round logs don't stack like this. How do you get them to stay in place? Now here is where a little knowledge and know how starts you down the path. Lets go for the details of 1/2 dovetail notch cutting and what we want the notches to do? Answers:
- hold the log in place
- determine the spacing between logs
- keep the center mass (chalk line) of each (below the top log) log level
- keep the center mass of opposite logs in the same layer at the same height
- keep the top surface of the top two logs level to support the roof rafters.

OK then, lets start a cut'en. In a nut shell with the top piece in place (the far side N log is done) and the top corners of it are at 4.250 height . The near "log" S is sitting in place on top and the corner at F is 4.750 high the other end is 4.875. Doing the math we need to lower F side .500 and the other end .625. We do this with the notch. We split the amount to be removed taking half from the top piece and half from the lower piece. You can see this layed out in red pen.

And that is how it works. After the notches are cut logs S and N are level and at the same height ready for the roof rafters. Well sorta.

Now I just have to apply this thinking to this pile of logs and I got my tree house (log cabin)!

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