Dovetail Formula

[Redmt]

I want to create dovetail corners for a wood shed and eventually a small cabin. Is there an actual formula for laying out the dovetail cuts? I see that there's at least one seller of the pattern size to build a jig for a specific log/timber size. I'm not exactly sure what size logs I'll end up with but guessing it will be in the 6-8"x4" and probably 6-8"x6" . Is there a standard type formula to create my own cutting jig dimensions?

[Don P]

Don Chapman had a program for figuring out notches and heights but I never saw it. 

Part of it would be whether it is to be chinked or not, are the logs bearing full length and making a tight dovetail, or, is it bearing on the tails, chinked and somewhat adjustable in between.

[Redmt]

Right now I'm leaning towards tight logs bearing on the one below. I'm going to start with firewood shed about 10-12' x 16-18' with  4"x6-8" logs. Cut flat on 4 sides and thought I would run a bead of caulking between them.

[Don P]

To get everything to hit at once with a jig would take good repeated dimensioning of the material is where I was going with that thought.

This is a pair of corners from a precut log home I built.



 

 

You can see their sad little attempt at a great idea, that draft stopping tenon, just make it about 3/4" deep instead of 1/4".  

[Redmt]

We built a custom log home in 2005 with D logs. We used the butt and pass style. In each corner or wherever 2 logs needed to be joined, we drilled at the joint and squirted in a couple pumps of caulking then drove a 1" wooden dowel. It does not leak anywhere. 

[SLVA_D]

Check out this link, has a customizable beam size, dovetail calculator for cabin building.

https://www.blocklayer.com/woodjoints/log-dovetaileng

[logman]

Don Chapman had a program for figuring out notches and heights but I never saw it.

Part of it would be whether it is to be chinked or not, are the logs bearing full length and making a tight dovetail, or, is it bearing on the tails, chinked and somewhat adjustable in between.

You know I think I still have my notes from his class.  I will look and see what's in there.  I know he used a piece of plexiglass with the angles on it and I still have that too.  One of his guys that worked with him still builds log cabins so I'm sure he knows.  Gary Horton, you may know him.

[Don P]

I do know Gary... hmm, I have notes from him here somewhere.

Welcome SLVA_D, where are you?

[SLVA_D]

Thanks, im in Upstate South Carolina

[Don P]

Cool, my folks first retirement place was near Seneca, Keowee. They are back in eastern NC now.

The blocklayer app looks like it would do the job if you're planning half dovetail. If it's full I would do my first trial around the center x center point of the notch and make it half the timber height at that point, working everything from there.

[Redmt]

Thanks for the pointers. I had tripped over the link for the calculation of the angles but looking at it on my phone, I passed it by. When you posted the link I fired up my PC and that's exactly what I'm looking for. Thanks for posting it.