Replies

1. 
   PSeverin | Feb 02, 2011 07:18pm | #1

   Maybe I don't get what you are asking.

     If I remember my structures well enough your web is just linking the top and bottom flange in a fixed relationship to each other.   Most of the real work is done in the flanges.    Why, is it critical to have much more accuracy than the web pieces cut out by a saber saw.   After all you could replace your web with a series of pinned strait struts and end up with much the same thing.

   By "chords" do you mean flange?  

   Since you've made these before I trust that you or someone did the engineering on them.  You've taken on quite a job.

   Peter

    

2. 
   DonStephan | Feb 02, 2011 08:27pm | #2

   A 2.5 or 3 HP router likely would be strong enough to rout a through slot in OSB.  I'm sure NC routers rout through slots all the time.  Be aware however that the router may want to wander  away from the template if routing a through slot.  A router bit manufacturer could recommend a bit design.

3. 
   sapwood | Feb 03, 2011 12:04pm | #3

   I have always worked by the axiom that a router is for trimming and not for hogging. I would think you will loose time by trying to cut the curved sections by using the router only. You will also create a great deal more dust. Nasty work, I should think. 

   If the curve is not too severe, a circular saw might work. I once cut out rails for a hockey rink enclosure using a wormdrive saw. Otherwise a big jigsaw would be my choice... guided by a shop built jig it will cut as clean a line as you could possibly need. Accuracy to within 1/16 is easily achieved and your metal roof will never know the difference.

   And: you are not building "trusses" you are building curved beams. The top and bottom members of these "I" sections are the flanges. The 18" member is the web. As an architect you ought to know the terms. Using them correctly goes a long way toward efficient communication.

   One more thing. You cannot possibly duplicate onsite the product that a factory can. For one thing, the pressure they use to  clamp the members together with isn't achievable in your house/shop. So I hope you've over-designed these beams to compensate and are not simply duplicating what Boise-Cascade would build. Better, you've had a licensed structural engineer design them for you.

4. 
   acornw | Feb 03, 2011 02:55pm | #4

   Well.....

   Well, the way the world does this is to swing a trammel jig through a band saw. Stack up a few sheets, mount to the trammel jig set at whatever radius you need, and swing it through the saw. Fast, accurate, safe, quiet and simple.

   A trammel jig is a fixed pivot point set out at 90 degrees to the band blade, with a pivot arm and apparatus of your own design to hold the OSB how you like.  Trammel - like a compass.

   Dave S

5. 
   PSeverin | Feb 03, 2011 03:35pm | #5

   Pattern routing?

   Ken,

   Sounds like you want to do pattern routing to make the webs.  Since they use routers to cut openings in SIPS panels, it is certainly possible.  You just need a perfect pattern, a big router and a pattern bit.  I would think with the depth of the member that span will make the radius 20' or more, which makes trying to swing the router on a big beam compass or the boards on a long trammel,  a bit impractical

   I understood that you are making curved TJI.  I also sympathetic in not quite finding the right name for the part of a building.  Just the other day I tried to label that solid part on a storefront under the windows.   I called another architect.  He said he called them bulkheads.  I said I was leaning toward plinth panels.   That works too, he said.  Which one communicates best is hard to always a question.

   On the other hand, I did have trouble with the news talking about removing the last beam from the World Trade Site.  It's a column I said.   But nobody cared.  

   Peter

6. 
   zolton | Feb 03, 2011 07:31pm | #6

   Routing..

   This is certainly doable. You'll burn up a few bits, but routing OSB isn't that big a deal.

   I'd make a template that you could attach temporarily to the web material with a few screws. Use a plunge router with a collar and a half inch spiral carbide bit. Don't try to cut through the piece in one pass. Use two or even three passes, lowering the bit a quarter inch each time. You could lay the set-up on top of a piece of rigid foam board (on top of a rigid - and flat - plywood platform) so you could rout all the way around the piece without having to reposition it.

   It'll take some time, but if you're doing it for yourself and not as a paying job that shouldn't be a factor. And after you've done a couple of them you'll figure out ways of working that will make the process go quicker.

   Zolton

1. 
   kreidy | Feb 03, 2011 11:49pm | #10

   Thanks Peter, Zolton and All,

    I am still up in the air on whether to go with routing or rough cutting with a circular saw.  In my boat building days, we would use a table saw to rough cut all the planking and then hand plane it to the final dimensions.  Since the radius of the curved TJI's (The structural engineer referred to them an "I: Sections Trusses) is 21', there won't be any problem in using a circular saw.  I am having the pattern CNC cut out of Acrylic from an AutoCAD drawing I made.  I was thinking that if I permently attach a second pattern that would allow for running a saw and then with the same pattern use a router to bring it to the final dimension.  This way you would not have to switch patterns or make multiple passes with the router.  I like the idea of using the foam board although I had originally thought about using raised blocks on a pair of saw horses placed end to end.  I still have time to come up with an efficient solution.  Thanks for all the ideas.

   Ken

7. 
   BruceS | Feb 03, 2011 08:00pm | #7

   engineered joists

   Insurance carriers in my area charge higher premiums for their use.   And the local fire dept's  really hate them.

1. 
   sapwood | Feb 03, 2011 10:02pm | #8

   Regarding the insurance carriers: This is interesting because I've never had my insurance company, or companies, ask what the framing material is in my wood frame building. I've owned several houses and one commercial building. 

   Is your experience different? Maybe it's a state thing....

   And why would the fire departments hate them? Does OSB burn faster and more readily than solid timber? More pertinent... does it loose it's strength faster when under fire? But again, I've never been asked by a fire department to "please not use osb in the framing."

   The stuff's code approved for crying out loud.

1. 
   BruceS | Feb 03, 2011 10:17pm | #9

   Fire depts

   My Son is a lieutenant on a local Fire dept. and they hate those I-beams.   He says they burn through much quicker than solid floor joists.   And with the spans they are being used for makes them even more dangerous when they are weakened by fire.

   I know they are trying to get the codes changed for fire reasons.

1. 
   PSeverin | Feb 05, 2011 02:30pm | #11

   Proposed Code Revisions

   I read through a proposed code revision about light wood frame construction that used both I joist and roof trusses.  Both fail relatively quickly, 10 to 15 minutes, if unprotected.

   The proposed solution was not to require increased protection but to put a big blue diamond on the fronts of building indicating the use of wood roof trusses and floor trusses.   The idea being that firemen would not rush into a thus marked building only to have the floor give way or the roof fall down on them.

   Back to Ken making the trusses I would think if industry is using routers in making those structurally insulated panels that they will hold up.  I would probably have used a saber saw before I gave up at how slow it was.   Let us know how it goes.   Since you've done this once before, you obviously know what you're getting into.

   Peter

2. 
   DonStephan | Feb 05, 2011 07:50pm | #12

   2x framing stock is 1 1/2"

   2x framing stock is 1 1/2" thick with few through holes.  Wooden I-joist webs are 1/2" thick with regular holes that make them burn even faster.

1. 
   BruceS | Feb 05, 2011 08:29pm | #13

   I-joists

   I  know what they are.  And I dislike them as much as I dislike steel studs.   I might be a bit old school.  When I built my house and shop I Stick built  everything   and used  Southern yellow pine 2 X 10's   for floor joists and the roof rafters.

8. 
   [email protected] | Feb 06, 2011 12:29pm | #14

   The framers do it all the time.

   Watch the framers doing the sheathing  put the osb panels on a building. 

   The sheathing goes over everything, including all the openings. 

   They then plunge in a plunge piloted bit, and use the framing for the opening to guide the bit and cut out the osb, before picking up thier niler and nailing the osb to the perimeter of the opening. 

   There are even dedicated ones with center pilots designed for doing the thin walls on trailers, that let you do both the interior, and exterior skins at one time. 

   So yes you can do it.  Try going to the Whiteside, or Amana sites, and then contacting the tech reps for a recommended bit.