Log cross cut jig

[wavekiter]

Hi all:

I am a relative newcomer to log and timber construction and have really enjoyed this forum over the last year or so - lots of good stuff here.

My plan is to build a log post and beam gazebo so I will need to accurately crosscut the ends of all logs perpendicular to the 2 reference planes within the log (as defined by the cross hairs on the end of the log.)

Recently, I purchased "A boys big book of jigs" (I.L.B.A.) and 2 jigs in this book caught my eye - The "multipurpose square cut jig" and the "Chris Clay square cut jig". Both of these jigs align with the top cl (centreline) and side cl of the log. The cut is then made with with a chainsaw in a guillotine style bracket on the end of the log. Has anyone out there built or used one of these jigs? Both jigs look very effective but I was just wondering what method others use to accomplish this task before I get the welder to whip on of these jigs up.

I have used "the piece of linoleum wrapped around the log" trick which works reasonably well if the log is straight and has little taper but in my case some of the logs have flare butts.

The 2 square method (one square on the top cl in contact with another square on the side cl) also works well again if the logs have no taper.

My logs are too long and heavy (some 20"-22" butts) to try to stand them vertically plumbed in both directions and then use the scribers against the flat concrete slab to mark the cut.

Any input or comments would be appreciated.

Thanks-------------Craig

[jander3]

snap 4 chalk lines on the log, use a couple of squares to draw your line.  If you want it very clean, use a chisel to mark your line.  Cut her with a chainsaw (freehand); you will be be fine

[wavekiter]

Jon:

Thanks for replying.

I've used this method before and it works well if the log has no taper.

I've run into problems using this method with aggressive flare butts though because the body of both squares aligned with the cl's snapped on the log needs to be parallel with the arris (intersection of the 2 reference planes within the log). Do you then "float" the end of the body off the surface of the log to achieve this?

Craig

[Jay C. White Cloud]

Hi WK.,

I need to know a few things to share the correct method.  What is the length and width of the biggest log you will be building with in it's roughed in size?

Regards,

Jay

[wavekiter]

Hi Jay:

I wish I had a sketchup dwg to show you my plan. (learning this program is on my to do list.) The logs are arriving next week (wintercut!!!) and my plan is to strip the bark immediately and wax the ends. Hopefully I will get at this later in the summer.

This project is 12'x12' in plan (dim'd from centre of logs) and consists of 4 - 10' (16"tops) corner posts. These 4 posts support 4 - 17" (20"tops) log plates. These log plates will be lap joined on each corner post and will get a 12:12 pitch rip on top. At the midspan of each log plate there will be a 6' (+-) king post (16" diam). A continuous log ridge (17' x 20"top) will span from one king post to the opposite side. The adjacent 2 kingposts (6' x 16" diam again) will support the 2 other ridge logs (8' +-) which will join into the perpendicular continuous ridge at midspan. (All ridge logs will again have 12:12 pitch rips).

Each post will have 2- 4x10 braces in 2 directions. (the posts and underside of the plates will recieve a "flat" to mill the mortise's for the 4x10 braces into.

A timber roof system will piggy back on the pitch rips of the plates and ridge - 4 valleys and 2 perpendicular ridges - all jack rafters.

That's it in a nutshell-----------Craig

[wavekiter]

I should add the reason why I want to be so accurate with these log end cuts is because I'd like to house the jacks into the valleys and with a structural ridge (unlike fork and tongue) errors will really show up here.

Craig

[Jay C. White Cloud]

Hi Craig,

I will help where I can, or where you think I may assist you.  The joint you are describing is called "Engawa no keta" (縁側野桁) or "Sumiki keta" (隅木桁) in Japanese.  If you cut and past the Kanji (Japanese Print,) into Google Images, you can see other examples.  They (Japanese) have the oldest examples of this work.  I'm sure you could modify it to your application and liking.  Here are some more examples.






http://www16.ocn.ne.jp/~ikgroup/kentikurei/gijyutu.html
the above link is in Japanese, but if you use google translate, you should be able to make it out.

If I did things correctly there are two Sketchup files for you to play with also.

Layout is all in Asian Line Layoff method, similar to what you have already described, it just sounds like you need to "tweak" you method a bit and things will work fine for you.

Regards,

jay

[Jay C. White Cloud]

Craig,

I couldn't find this before, here are other photos for inspiration.

Log Pavilion

Ceiling log Branch Work

Ceiling Log Beam Work


Engawa no keta photos from a friend

[wavekiter]

Jay:

Thanks a lot for taking the time to dig this stuff up. Lots to digest here.
There is no question that the Japanese have this stuff figured out.

Seeing this has definitely got me thinking about the valley / Keta beams connection. Originally, I was planning to bevel the bottom of the valley rafter (Hawkendale angle C5 -30 deg for 12:12) where it lands on the pitch rip of the top plate log (and the one with the continuous pitch rip). I am now thinking I should "slot" the intersection of the Keta beams while incorporating level bearing within the joint - similar to the Japanese approach.

I just realized the book "Japanese Joinery" has a whole chapter dedicated to "hip rafter assemblies".

Craig