"New(bie)" joint?

[Toadze]

Hi you good people,
Thanks in advance for all the brill. info I've been reading for the last 3 nights.

I'm attempting a TF workshop, 20' x 30' simple 4 bent. I would like to support both the roof and wall sips at the top plate and also have no horizontal forces to contend with as my math is non-existent. I couldn't find a joint to do this directly so I came up with the attached (rough) sketch. What do you think? Give me a second to get out of the line of fire.

Also, I reckon for the clear span beams @20'  8" x 12" should do it. These will have an unbraced king post. Am I on the money?  I don't know what allowance to make, if any, for the king post.

[beenthere]

Toadze
Welcome to the forum.

Get your pics (images) in your gallery (see Help above for a tutor) and then you can paste them in your post (message). Also, use the Preview button to verify you are going to send what you want to send. And, you can modify your original post.

We're anxious to see the design you have, so hope you pull up a stump, and persevere with getting an image posted.

Sounds like a great TF workshop you have in mind.

[Jim_Rogers]

Welcome to the forum and if you need help with the photos you can email them directly to me and I'll reduce them for you and send them back and you can create your own gallery and post them there, for including in your thread....
Jim Rogers

[Tony_T]

When you mention span/beam sizes it will also help to know what species of wood you intend to use and where you are located (snow loads?).  The same size that works for oak might fail using pine....

[Toadze]

Sorry about no photy people, I think it's sorted now Jim, many thanks.

Tony-T   I shall be using spruce Tony, I live in the Outer Hebrides Scotland, LOTS of wind, most snow I've seen in twenty years is about 4 inches. The long term trend for this area over the last fifty years is lessening. Can you answer my query about the effect of a kingpost in the middle of the beam? I can't make up my mind if the beam is supporting, or supported by, the kingpost!

[TexasTimbers]

Welcome Tony. Glad you decided to post it. I am not qualified to answer your question but as I said I can assure you no one will laugh at your joint. It looks good to my layman eye but we shall see.

[beenthere]

Tony
Good drawing/photo.  One question, as the 16 x 8 post has dimensions for the cuts at the top, of 2" 2" 2" 8", for a total of 14".  What is missing? 
I can see a 6" plate fitting on the post, but not the 8" plate shown. And the vertical tongue going up through the girt and rafter may be at risk of splitting off the post, it appears anyway.

[Toadze]

Hi BeenThere,

Apart from the obvious fact that I may be a few cells short between the ears, the sketch has not been finally sized as there are other factors, like final beam/post size and whether a thicker than normal tenon should be used. My own assessment is, for; not too difficult to cut, good strength during the raising and allows me to support wall and roof sips ( the original reason).Against; not proven, possibly extravagant on wood but I'm hoping some thorough critical appraisal from the gang here will push me in the right direction. Thanks to everyone!

TOny with an ADZE.

[Jim_Rogers]

More information needed, you've said the building is 20' wide but you didn't say what the roof pitch was. Please tell us in degrees or ?/12....
This is important to understand.
Also the top tenon of the post usually doesn't go through the tie beam and into the rafter.
The rafter foot goes into the top of the tie beam thus making a triangle like truss.
In your case you're relying on the post tenon to hold back the thrust from the rafter foot and this would/could cause the jowl to break off the post along the grain line.
A jowl dimension would/should be shown also.
How long is it down from the shoulder of the plate or tie beam or both?

Also, if that is a corner post the plate does not have a fork joint, very weak....
You should offset the post to plate tenon to the other side and make the plate go to the end of the building with an offset mortise as least 2"

Like this:




Jim Rogers

[Don P]

Welcome to the forum Tony. I want you to answer Jim's Q's but wanted to say hi and ramble  ;D.

The long tennon through the bottom chord and rafter is one I just did. I got the thrust resistance for the rafter heel by burying the back of the rafter in a notch large enough to take the rafter's thrust load. The long "blade" of tennon from the post helped keep everything in alignment during the lift but made me pretty nervous, its pretty slender for its length.  I changed alot in the second bent, that was one of the changes, it looks alot more like Jim's drawing, well a little fatter, overkill the other way, once bitten..  :D

On what is going on with a kingpost, call it a rod, it could be a rope. It's in tension normally.
Visualize a log across a creek. If the log is too small it sags in the middle, we can cut the span in half and put a post down if its not in the way. Another is to prop logs up from each bank, lash the tips together and drop the line down to the middle of the sagging log and cinch it up flat again. The weight the rope carries is tension pulling on it. The 2 logs propped together deliver the tension load back to the creekbanks, they are in compression.

Another way to do the same thing, put the kingpost under the log and stretch a cable from end to end under the king. Draw tight on the cable and the kingpost lifts the log up in the middle. In that instance the kingpost is in compression and must be of a stiff enough material. The chords lifting it could be ropes, they are now tension elements.

In high enough wind parts that are normally in tension can go into compression and vice versa, one reason to be careful with tension parts that can't take compression if there is a stress reversal possible.

[Toadze]

Hi Guys,

Great Response!  Jim, I'm green over your drawing prog. and expertise, I know it's not as quick as it seems but the clarity is absolute.
The main hesitation I have with your design is that I can't raise the bent in one piece. Also I don't quite understand why the jowl should split except under extreme wind perhaps, if required the jowl width could continue to the floor. I plan on using 40 degrees which I think is also 10/12 for the roof pitch. Fork joint weak...Yes I can see that! As far as final dims go I havn't finalised anything but basically thought of 8" x 14" for the jowl top, 8" x 8" for the plate and rafters and 8" x 12" for the beam. Everything times 4 to give me 3 bays of 10'. Actual dims. will be to suit the Sip joints based on 8' x 4's.
DonP,  Hi!  Yes, I think a chunky birds mouth plus a half tenon cut into the top of the beam would take care of horizontal movement. Sounds like parallel thinking with you one + laps ahead.
Keep 'em coming fellas, this is fun!!
Tony.

[Jim_Rogers]

I did a new drawing in just lines to show you the projected tenon and it doesn't look good:



As you can see with a 16" wide jowl and you project the tenon lines up through the tie beam and the rafter foot, the tenon doesn't come anywhere near your drawing.
The slope of the rafter and tie and plate is 40° or 10/12 the chamfer on the plate is 2" but even if you made it smaller you're not going to gain very much.

I did this to show you that this tenon up through isn't that good of an idea.

What Don has suggested is usually the way it should be done.

Jim Rogers

[Toadze]

Thanks a lot Jim, it seems I can't build a bent in one and still have my top plate where the wall joins the roof. Unless anyone has an alternative design?

Thanks to all for your interest and help. I must think more on this. And draw it properly!

Just off to bury my idea with full honours (sob).

Tony.

[Jim_Rogers]

There are many ways to build a timber frame....

[Max sawdust]

Toadze,
I used a tongue and fork joint on a TF swing set.  I do not like the way it has "aged".
Have you done much reading on the subject of Timber Frame Joinery?  Loads of good books out there ;)
Try a search on this forum.  Several threads on the subject.
I look forward to watching your progress on this project.
max

[Toadze]

Hi Max,

I have Jack Sobon, Steve Chappell, Steve Elliot, 3 by Ted Benson and 3 on design coming from the TFG Oh,, and one by Larry Haun from before I found out about TF.

Great Crack here!!

Anybody have experience/preference on portable bandsaws?

Hope everybody is having as good a day as me.

Kind Regards to all,

Tony.

[Jim_Rogers]

Woodmizer all the way......
go orange.....

[Toadze]

I wish, Jim Oh how I wish, but what I meant was, portable as in hold it in your hands. I am trying to find out if this is a good way to go for roughing out joints, it would obviously be useful for jowls and curving arches. Cheers,

Tony.

[Dave Shepard]

I've never met a 'Mizer I didn't like! If you click on the Woodmizer sponsor link on the left you can search the dealer locator. There is one in Scotland.


Dave

[Tom]

While it isn't a bandmill, this is a machine that has enthralled me for several years.  I've yet to see one in real life.
http://www.awed-machine.com/bandsaws.html

[Dave Shepard]

That's pretty wild Tom!


Dave

[Jim_Rogers]

There are several brands of hand held band saws.
I'll see if I have any links.....

http://www.timberwolftools.com/tools/kind/bandsaws.html

And if you're like to get something cheaper you could get just the Prazi beam cutter chain saw bar attachment.
Here is their link:
http://www.praziusa.com/beamcutter.html

Jim Rogers