Cull the post, put the bow to the inside, or move the brace -- those are your options, mo.

This happens in other circumstances -- crowned rafters with a collar joining. Or a bowed floor beam -now your joist only has a 1/2" bearing because you laid your joist pocket depths out from a chalk line -- you got to make your joist longer and get a deep enough housing. Or anywhere 2 sticks join each other and one bows away from the other so much it is outside the lines of it's "perfect timber".

The bottom line is that working with wood this curvy is a pain. You can't get all the efficiencies of square rule going, because you end up with an exception to each rule. "Was this the girt that is only 7" tall?" "Which one was it that had a 3/4" sweep, so we have to move the . . . ?" The drawings end up covered in little notes to remind you what you did here or there, so you can remember to shift this or change that length. You end up square-mapping it and it's a real pain. But it can work.

It's a really strong argument for using good wood.


Then there's always what a guy I worked with once told me. "You'd be amazed how much you can bend wood"

and sometimes, that's the approach that makes sense.

Good points about all of those notes becoming clustered.
Maybe scribing is the way to go?

You guy sound like Al Gore and global warming, in that he stretched he truth to make a point. Ifits that bad cut it in half and us it elsewhere, re saw it, hew it straight, or something. But lets not make this more dificult than it needs to be. Square rule is simple. If your timbers are that wanky, scribe, or have them resawn. With that all said, If I have to snap lines for lay out, my line represents one side of the mortice, no need to recalculate off a center line or some other number. You can still plumb and level on the ends with lines that are not centered. I also only snap lines I need, if no joints on the other three sides, no lines. Tim

Many ways to skin a cat...

Jim, the book I was looking at was Jack Sobon's book "Building a Timberframed House, copyright 1994. I was reading the short section on layout for Hewn timbers. There he uses 1.5 inches, the width of the narrow tongue of the square, as the approcimate inset distance for the snap lines.
Brad

oh well, so much for thinking

by the way "narrow tongue" is the department of the redundancy department. "tongue or blade" and body. Just some basics. OK thats all from me on that.

brad, in that book the post are hard wood, Jack is using 1-1/2" mortises due to the fact that it is much harder to bore 2" holes in hardwood, if the post were softwood you would of seen a line 2" off the ref. face. He would not of snapped a line 1-1/2" off than calculated the extra 1/2" to the 2" mortise. On page 78 it clearly says "edge of mortise/tenon" with a arrow pointing to the line. Also notice that every thing is housed to 7-1/2" on a 8" timber, forming the inside face ready to receive the incoming member. That is only an example, on the actual frame he used a layout tool, based on the hard edge of the timber, no snap lines, see page 85 top left photo. Tim

Timbbeal,
So what are you saying? If you didn't have the exact example he did, you would always snap your line exactly to the edge of a mortise/tennon? Let's say your reference face is not uniform. What do you base the measurements of the end points of your chalk line on? Do you stretch a chalk line to hit the highest points of your reference face and measure from there?
What if you have multiple mortises in a face at different locations like a beam intersecting in the middle and a brace whos mortise is not centered? Just trying to clarify and get a better understanding...I'm really surprised that there doesn't seem to be a nice layout video out there that shows all three techniques and their nuances. That would be a good thing for the guild to sell online. I've heard that there have been demos at conferences. Surprised no one taped them for a video. There could be quite a number of demos by different Timber framers.

Brad, when a timber frame designer make a set of decisions about a frame's design they are generally called "General frame rules".
These general frame rules are such things as 1)all joints are reduced to the next 1/2" down in size. 2)all joints are 2" off layout face and then 2" thick. 3) all bents are laid out from the west side except the east most bent. 4) braces are framed to 4" thick.
What this means (#1) is that all joints are reduced to a common size so that irregardless of the size of the rough sawn timber the joint is sized to one common size. So the tenon on the end of a 8x10 tie beam is sized to 9 1/2" and and mortise is sized to 9 1/2" and the housing where this tie beam enters a post is sized to 9 1/2".
What this means (#2) is that all joints are laid out from one of the reference faces on both the tie beam and the post, using the above example again. So even though the tie beam is 8x10 and the post is 8x8 the tenon and it's mortise is 2" off the layout face and then 2" thick. Also, the brace pocket in the tie beam and the post are also laid out to the same spacing. This keeps everything lined up and easy to layout and cut. This the value of square rule framing.
What this means (#3) is that irregardless to which way the frame will sit on the lot when it's raised, the designer has placed a compass north arrow on the plan and it is used to understand which way is east and which way is west. And the interior bents are laid out to this rule. This again makes it easy to layout joints and cut them.
What this means (#4) is that if you have a rule like #2 and you have 4x6 braces the tenon will be 2" off the layout face and then 2" thick. But the brace is 4" thick so what happens when the brace stock has shrunk while waiting to be cut? You can't move the tenon off the 2" offset. You can't make the tenon 2" thick as the stock has shrunk. So, what do you do?
You don't order 4" stock for braces; you order 4 1/8" stock or thicker. Then you have enough wood to layout your tenon 2" x 2" and then you shave the back side of the brace stock so that the tenon ends up 2" thick, using a hand plane.

So in your frame your chalk line will show you the 2" offset and all mortises should be on the line, if that's your "general frame rule".

Now in Jack's house the posts were oak, and therefor stronger so he used a different rule that the tenons on the oak posts could be 1 1/2" off the layout face and 1 1/2" wide. And as I have just reviewed his book and frame design again, it appears that most of the joints in that house frame are 1 1/2" x 1 1/2", with the exception of the scarf joint tenons. So that frame will have some general frame rules and some exceptions to those rules.

Standard timber framing rules for sizing tenons are that the tenon should be 1/4 the thickness of the timber. So an 8x10 tie beam should have a 2" thick tenon. And another standard timber framing rule is that the peg diameter should be 1/2 the tenon thickness. Now each frame has to be individually evaluated by a timber framing engineer to make sure the joints won't fail, but these are some standard rules.

Jim Rogers

That makes perfect sense Jim.
I would like to make a couple of comments on set up, and you guys please tell me if I am off or on.
Say I'm preparing to layout a post. I decide to put the crown to the inside of the building. I stretch the chalk line along the primary reference face let's say two inches from the edge that meets the secondary reference face. If there are any high spots in the middle pushing on the chalk line, plane those down. I could also optionally plane down the ends to try to take some of the concave bow out of the primary reference face, if I want to, if it's excessive. When setting up this first chalk line, I measure 2 inches from the edge at each end of the timber. There is nothing, however, to say that the secondary reference face or edge doesn't have crown or wankyness of it's own. Therefore, before snapping my primary face chalk line, I must make sure that my chalk line is 2 inches from the highest point of the secondary face edge. I may want to stretch a chalk line along the secondary face and look for high spots and plane that face closer to being straight and level(square with primary face). It is only then that I may snap my first chalk line. Is this normal or typical? I understand that you may elect not to plane or modify the timber at all, such as in the case of a hewn timber. In that case, you may decide to measure as best you can and determine the location of the first chalk line. I then assume that you will determine the secondary face chalk line endpoints by both using your square on the end of the timber and measuring 2 inches as best you can from the reference face. Comments?
Brad

A while ago I discussed this with a friend and former timber framing teacher of mine. He said that you can plane down the ends some, but the limit is the amount you're going to reduce the timber to make a joint. So for example if your general frame rule is 1/2" under the size of the timber then 1/2" is all you can plane off the ends to try and straighten it out.
If you plane off more then you're going to be under size on your joint on the ends.

I thought at the time that idea made sense to me....

Jim Rogers