Jayson - scarfs

[Greg]

Ok Jayson,

A first question is how is the scarf joint assembled in a raising, or does it "just depend" on the situation? I have asked this before, but I don't think scarf joints are very common. And those that are true experts typically are out there working/ don't have time to answer these dumb questions...

Are the two ends members joined/reinforced with clamps on the ground then the entire piece "flown" into place, or are they put up separately and joined via wedges or whatever "in situ". (sorry if that terminology is not right - thats a fancy phrase I've heard Jack Sobon use!)

Since its difficult for me to cut or acquire > 16' beams, I was planning on scarfing the two plates on my (infinitely slow) garden shed building.

Secondly, in your experience what is the best technique and/or power tool to cut the long diagonal mating surfaces. I have tried several ways, but it still a *ton* of hand chiseling and planing. I've used a prazi (?) beam saw that gives a nice quick rough cut, but its the precise work evening out the last bit of material that takes forever.

I have concluded there is simply no good way of doing it  :-\

Greg

[Jayson]

First of all the only dumb question is the unasked question.Secondly my take is that all joinery fits into the "just depends" section.Thirdly(is that a word?)the good way is relative.Patience and perseverance usually being the key.The scarf is not really all that uncommon other than the fact it is intimidating.I usually cut that sloped table from both sides with a circ saw starting with a 71/4 and then a bigger circ according to timber size,watching out for the hidden tenon if neccesary.I wood think you have one(internal tenon)in that plate to resist lateral movement.I should have mentioned that prior to the saw cuts that you could drill the inside corner on that slope,again watching out for that internal tenon.(I should really have a picture of your scarf to suggest how to cut it).Your scarf should be 3 to 4 times(I do 3)in length what your plate is in thickness.If you have an 8 inch plate your scarf should be 24 inches in length.That wood be 2 feet of joint on each member.There are great pics of scarfs in Historic American Timber Joinery ,A Graphic Guide,by Jack Sobon I believe.You should be able to find it on the Timber Framers Guild page.Worth every dime.I do not do alot of drawings online for I am not very good and do not have the software,but if you have a picture to post or fax to me I wood be happy to look it over.And where are those busy timber framers.I need work till Christmas.

[Raphael]

A first question is how is the scarf joint assembled in a raising, or does it "just depend" on the situation? I have asked this before, but I don't think scarf joints are very common. And those that are true experts typically are out there working/ don't have time to answer these dumb questions...

Are the two ends members joined/reinforced with clamps on the ground then the entire piece "flown" into place, or are they put up separately and joined via wedges or whatever "in situ". (sorry if that terminology is not right - thats a fancy phrase I've heard Jack Sobon use!)

 Scarf joints aren't as rare as you may think, there are a total of seven "scarf joints" in my house frame all were assembled "in situ".  I see this as the preferred way to do it but there is no reason you can't raise and assembled scarf with appropriate care.  The scarf is a weak spot in the timber and must be well supported if it's going to be moved.  Jim_Rogers covered the use of "strong backs" in raising a king post bent.

 My 36' plate in the eve wall of the shed was raised as two assemblies each was ~½ of the plate and a pair of posts with supporting knee braces:

 The post in the picture carries the lower portion of the scarf joint, this assembly was raised first and fully tied into the rest of the frame before the second half was brought in.

 My top plates and sill plates were brought in as individual timber and assembled in place.

Secondly, in your experience what is the best technique and/or power tool to cut the long diagonal mating surfaces. I have tried several ways, but it still a *ton* of hand chiseling and planing. I've used a prazi (?) beam saw that gives a nice quick rough cut, but its the precise work evening out the last bit of material that takes forever.

I have concluded there is simply no good way of doing it  :-\

 The "good" way is whatever gets you to the line quickest without going over: chainsaw, prazi, handsaw, circular saw, hatchet, axe, and coopers adze work for bulk removal and slick, chisel, hand plane for fit and finish.  And, as Jayson mentioned, patience.  If you've got the $$$ for a monster Mafell 25 3/16 in. then that's the good way of doing it.  :D

 My house has four simple half lap scarfs with tennons.  My approach here* is to rip with a chainsaw on a timber jig set to leave the whole line on the visible side and leave a 'line of white' on the far side.  I hand saw the shoulders and clean to the line with a plane before laying out the mortice and tennon.

 The *exception* is high tension wood:


This was scarf cut #1 in hickory, the kerf has opened up to greater than ¾" from it's original ¼".  My nice straight line I had cut so precisely to was now a graceful curve, funny how I can preach hickory in a sawmill forum and totally not see that coming when timber framing.  :D

[Greg]

Thanks guys. Excellent pics and info!