iDRY Vacuum Kilns

Sponsors:

How much bow is acceptable?

Started by oe_alex, February 27, 2014, 10:10:00 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

oe_alex

Hello everyone, I'm a landscape contractor located in Iowa. Timber framing has always piqued my interest, this forum seems like a good group of helpful guys.

We are going to be building an 18x18 Western Red Cedar pavilion this spring. Plans are drawn, I will attach a photo from SketchUp of what we're planning on doing. I just the other day got in the 8x12x24's for the headers, plates and ridge beams. I pulled a string along the edge of one and noticed a little bow in it, maybe a 1/4" in the center. Is this acceptable? There is also one with a bit of crown in it. I'm thinking the best place for that would be the ridge, and the two that have the slight bow in it for the headers. Planing will probably not be an option, so any advice you may have would be greatly appreciated! I also must admit that this won't be an actual timber frame, we're planning on using 3/4" lags with malleable iron washers.

  

 

Raider Bill

Welcome to the FF!

The way I build a 1/4" off it in 24' is dang accurate :D
The First 70 years of childhood is always the hardest.

Dave Shepard

That shouldn't be a problem. Does the sag go away if you put the timber on saw horses with the horses right at the ends? I bet it does.
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

oe_alex

I just went out and pulled the string on all five. Three are pretty true, one is 1/4" and the other 3/8". So for 24' I would also say that's pretty dang good. Aside from the middle one, crown is very minimal.

These will be sitting for a while before we cut them, should I have them sitting another way than how I have them in the picture? I am thinking of sitting the two with bowing on the face with the bow up to get them to settle a little. I also have the dunnage spaced about 4-5' currently. Trying to correct the crown on a 12" tall piece of timber seems impossible to me, will have to make sure to crown up when building and let the load take care of them.

thecfarm

oe_alex,welcome to the forum. That will look nice!!
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Dave Shepard

I'd place them all crown up, and move the dunnage out. Maybe ten, or even twelve, feet apart. I sawed some 30' white oak timbers last June. They had a little bit of crown to them, but the framers said that if they put them on horses and someone sat in the middle, it was enough to take the crown out.
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

Peter Drouin

A&P saw Mill LLC.
45' of Wood Mizer, cutting since 1987.
License NH softwood grader.

Brucer

WRC is notorious for moving as you saw it. That amount of bow is trivial.

Where possible try to have your beams a little higher in the centre of the span, rather than lower. The weight of the roof is going to try to straighten them in any case.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

oe_alex

Thanks everyone. When I say "bow" though, I am talking on the face side (the 12" side). That's where my 3/8" and 1/4" inch are coming from. The main reason I was concerned about that was that 5/8's of an inch throwing something off. The roof is something I definitely don't want to mess up.

As I was turning them all crown side up yesterday I ran across this. I didn't see it at the yard in Colorado as they had them wrapped for me. This particular beam is going to be a plate on the side. Is there any way of remedy-ing (?) besides facing it outwards and trying to have the rafter overhang hide it? Unfortunately it's right smack in the middle of the beam, and driving 10 hours to replace I think would be a bit silly.


dukndog

Chamfer the "bad" looking part out. Basically take a draw knife and chamfer it to a 45 on the edge. If you do a search on "timber frame beam chamfer", there are some pictures explaining it.

Good luck!

Rich Miller
WM LT-15G25 w/PwrFeed, Mahindra 3510, Husky 385xp, Stihl MS261 and a wife who supports my hobby!!

Jim_Rogers

Patch.

If you bought 24' long timbers and the frame is 18' you've got an extra 6' of timber, cut a patch out of one of the extra pieces and put it in where this defect is.

like this:



 

It can be done and not show much.

Good luck with your project.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

witterbound

I'd chamfer it too, and put it outside and up.  The roof will be coming down there.  Nobody in their right mind should care ... But some clients think timbers should all be perfect like trim work.  It isn't trim ...

oe_alex

Quote from: Jim_Rogers on February 28, 2014, 01:14:34 PM
Patch.

If you bought 24' long timbers and the frame is 18' you've got an extra 6' of timber, cut a patch out of one of the extra pieces and put it in where this defect is.

like this:



 

It can be done and not show much.

Good luck with your project.

Jim Rogers


Yes! Exactly what I was looking for. Five of the timbers will actually by 22' long for a two foot overhang on the gable ends, but I will still have enough to patch it up like that. Any other photos that explain the process?

Thanks

Magicman

Welcome to the Forestry Forum, oe_alex.   :)

The tear out, personally I would turn it up and never think any more about it.  No one will ever see it but once, and then only if you point it out to them.
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

VictorH

Welcome to the forum oe_alex.  Not sure what your time frame is on your project but Jim Rogers will be teaching a workshop on Basic Timber-framing in Southeast Nebraska in late May.  We have 2 slots still open if you would like to join us.

Victor

Peter Drouin

Yup the yard boy with the forklift, they knew they did it before they sent it.
A&P saw Mill LLC.
45' of Wood Mizer, cutting since 1987.
License NH softwood grader.

oe_alex

Quote from: VictorH on March 01, 2014, 01:10:56 AM
Welcome to the forum oe_alex.  Not sure what your time frame is on your project but Jim Rogers will be teaching a workshop on Basic Timber-framing in Southeast Nebraska in late May.  We have 2 slots still open if you would like to join us.

Victor

We're hoping to have the everything wrapped up by Memorial Day, so there's plenty of season left for use yet this year. However, with 4+ feet of frost in the ground here, I'm starting to question that time frame as we will need a good 6 weeks to get everything done. The fireplace will be about 18 feet tall with 400 SF of thin natural veneer. 800 SF of concrete pavers, and the model image doesn't even begin to show the extensive landscape design with just about everything you can imagine included.

That said though, maybe you could provide me some more details? If I can make it work I'd love to come down. I have a brother that attends UNL in Lincoln.

Brad_bb

Welcome!  It would actually be uncommon not to have some bow or crown.  This can be accounted for in which timbers you select for which location in a frame.  You can often orient to work with the crown.  Additionally, laying out your joinery with square rule method will help you compensate. If you have some very bad crown or bow, snap line square rule will allow you to use a wonky timber.  If you have a location where you are going to need a straight wall, you select posts that are going to help you with that.  If you have a free standing post, you can use a wonky timber for that.  If a timber is really too wonky, you can cull it (set it aside and not use it).  Maybe you can then re-cut it later or have that timber re-cut for brace stock or something else?  Even very wonky timbers can be used, provided they are structurally acceptable.  Much like round or natural logs are incorporated into a frame using scribe rule layout technique, so too can a very wonky timber be used that way.  But you should first learn basic square rule, then snap line square rule.  Once you're very comfortable using those, then you can learn scribe rule.  Your timbers sound relatively straight though, so I doubt you'd need scribe for this project. 
   You also need to learn how to identify defects that will affect strength, joinery etc., basically how to grade your timbers and cull as needed.  It's not that hard to learn.
   That corner damage is not a big deal.  As someone else said, draw knife it until it's relatively smooth (won't catch anything or stick anyone).  If that section will be exposed, maybe sand it a bit to round the edges and blend it in.  Basically make it look like natural wane.  It's then possible to still layout joinery in that area using square rule layout.  This is, provided there is enough wood left to layout the joinery that it will not weakened.  For example, if there's a tenon on the end, It may have no effect.  It's not all that uncommon to occasionally get some wane on a timber.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Jim_Rogers

Quote from: oe_alex on February 28, 2014, 06:07:35 PM
Quote from: Jim_Rogers on February 28, 2014, 01:14:34 PM
Patch.

If you bought 24' long timbers and the frame is 18' you've got an extra 6' of timber, cut a patch out of one of the extra pieces and put it in where this defect is.

like this:



 

It can be done and not show much.

Good luck with your project.

Jim Rogers


Yes! Exactly what I was looking for. Five of the timbers will actually by 22' long for a two foot overhang on the gable ends, but I will still have enough to patch it up like that. Any other photos that explain the process?

Thanks

The only other photo I have is of the entire piece with the two timber framers who did the repair:



 

They just cut away the rotten wood and shaped the ends to the angle. Made a repair piece the same size and slid it in.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Back in 2009, I wrote up a paper on definitions from NeLMA's rule book. And included some pictures to show that these definitions meant.
I have attached it as a pdf so you can download it and keep it on hand to understand what they mean.
I hope you find it useful.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

VictorH

The workshop will be over Memorial weekend.  Here is the thread for it

https://forestryforum.com/board/index.php/topic,71929.0.html

Brad - he's planning on a post and beam so square rule won't really apply, although I'm trying to pull him over from the dark side  :D :D

Victor

oe_alex

Quote from: Jim_Rogers on March 01, 2014, 11:34:38 AM
Back in 2009, I wrote up a paper on definitions from NeLMA's rule book. And included some pictures to show that these definitions meant.
I have attached it as a pdf so you can download it and keep it on hand to understand what they mean.
I hope you find it useful.

Jim Rogers

I should clarify myself then. The "bow" is very minimal, is the "crook" that I'm worried about. 1/4" in the center on one, 3/8"-1/2" on the other.

PaAnkerbalken

You might want to check with FF member Rooster.  I sorta remember him patching in pieces into beams that had rot, damage, etc.  There were pictures as I recall.
logosol M7

PaAnkerbalken

 It's under re-facing a rotten beam by Rooster.....might give you an idea. smiley_thumbsup
logosol M7

oe_alex

So we have footings going in for this project sometime early next week.

My staff and I are still planning out the stages on how we're going to do this whole project. As we were discussing yesterday, the question came up about cutting the rafter seat cut. The two beams that have the 1/4 - 3/8" 'crook' to them are going to be the plates on which the rafters will sit. Will it be wise to get the beams up first and cut the rafters, individually measuring each one? The reason I ask is because the rafters are going to come together on top of the ridge with a 2" deep seat cut, my thinking that is if we cut them all the same that where the crook goes out on the plate beams, the rafters won't come together at the peak, leaving an open gap that will be seen. We also discussed maybe taking a strap and pulling them straight once in place, attaching the rafters, then letting it loose, but I would think that they will want to pull out, maybe taking the rafters with them.

Thank You Sponsors!