Building a laminate beam

[dan-l-b]

Does anybody have any experience building arched laminate beam?  I'd like to build a couple beams to support a 8-10 foot roof addition to my sawmill building.  Slicing the beam in 1/2" slices, bending, gluing and clamping to desired shape are basically what I am thinking. Type of glue and method of application , clamp spacing, etc. etc....

[CHARLIE]

I believe Wood magazine had an article on that some time back. Go to www.woodmagazine.com and use their search engine for their articles. I'm pretty certain it was Wood magazine....but I could be wrong. I hope I'm not wrong though 'cause I've almost made it through the year with no mistakes. ;)

[whitepe]

Dan-l-b
Some recent woodworking magazine
in the last three or four months had
an article about bending etc.
Listed various species of wood, minimum
radius for a given thickness etc.
I'll do some digging in my stack of magazines.
Whitepe  

[whitepe]

Dan-l-b,
Charlie's right.  It's the December 2002 issue of
Wood Magazine.  Looks like it's a good place to start
and it also looks like you will need plenty of clamps.  ;D

Merry Christmas,
Whitepe

[dan-l-b]

Thanks for the help whitepe and charlie.  We'll see if I'm biting off more than I can chew. :  

[Wade]

dan-l-b,
  I've done a lot of bent laminations. I would think your biggest concern would be what glue to use. I'm assuming that you are trying to bend these right off the mill? So you would need a glue that will hold wet wood. If the wood is dry you can use any yellow glue. I don't know the size of the beam you are considering, but you might want to use an epoxy if it is large and will carry alot of weight. Wet wood bends easier than dry.The tighter the radius, the more clamps you will need. Figure how many clamps you might need and then have a dozen more on hand. ;D  Also the tighter the radius the thinner each lamination should be. Good luck Wade

[dan-l-b]

Thanks Wade,  The front of this building is cantilevered out 4' and I used some 4x 6 beams to give it a kind of post and beam look.  I now need to add an 8' shed roof off the 24' clearspan side of the building.  This wood be the area I would pull my WM under.  Slabs and lumber could be stacked in the existing building readily available to my skid steer for moving.  A curved arch from ground level up 8'6" and out 7' I  thought might look neat :  But I have been thinking... I have 2 I-beams from an old bridge.  Seams a dump truck with too big a load drove on it one day :( :( :( When the bridge gave way, the truck did too...and the homeowner was left with two arched I-beams.  I hauled them off thinking I would make a bridge over my ponds or something.  They aren't bent identically as the truck and bridge gave way to one side, but there is enough similarity that it might work. ;D ;D  A bar joist between them and some wood facia .... The future is so bright  I gotta where shades 8) 8)  Merry Christmas.

[ADfields]

Well now, steel is not hard to bend. ;D   Get a chain from end to end and pull it tight with a binder or two then heat the part you want bent with a rosebud so it will match up.   In no time you will have a mached set if you want. 8)  Have fun.
Andy

[Rick Schmalzried]

Dan-l-b,

Wade is certainly right about being concerned with what type of glue to use.  Yellow glue is OK for bent laminations in furniture, but you shouldn't use it for anything structural.  Yellow glues are really a "plastic" that never really sets, so it can (and will) creep over time.  What starts out as a solid structure can weaken and fall apart if continually under a load as you will have with a support member.

What has been recommended in several of my woodworking magazines when discussing building a wooden foot bridge is to use a resicorcal (sp) glue.  This comes as a powder and is mixed with a liquid (maybe water, I don't know).  It forms a hard bond that won't creep.  As already suggested another alternative is an epoxy, but you need to check on the use of it on green wood.

As Wade mentions, bent laminations aren't that difficult, you just need to get the glue right.

[dan-l-b]

Thanks for the suggestions and encouragement. I will check into that SP glue.  Thanks Rick.  I wonder if bandsawed strips will work or do they need to be planed? ???

[Minnesota_boy]

Epoxy is a gap filling bonding agent, so bandsawed lumber is fine with no further work needed.  I think resorcinol needs a smoother surface to bond.  If any leaks around the joint, it will leave a red stain.

[JeffS]

Here is a suggestion that requires the use of absolutely no veneer at all.  I have built beams this way in the past.  Gather up some of the widest boards that you have laying around and get them all layed out some where to be layed out.  Fix yourself a piece of string the length of the radious you are laying out and tie a pencil to the end.  Using the pencil and string layout various segments of the arch that will fit on your wide boards.  Use chop saw or similar to generate matching angles on the segments and begin to assemble the pieces.  The beam that I canstructed was for a cedar log home and we used 2" thick 14" wide cedar slabs and glued and screwed them together, 3 layers thick, if memory serves me correct it was PL600 construction adhesive.  I believe the beam ended up being around 6" thick and 8" wide. Another good reason to contruct using this method is the ease of adding a tenon to the ends for joining crossing members.  

Jeff S   8)

[Don P]

This months Journal of Light Construction has an article describing barrel vault rafters using a similar method to the one JeffS describes. I have a scanner if you want it.
Dad used alot of glulam beams in the homes he built, supplied by the Koppers company, the glue was resorcinol and moisture content was below 15% at glue up. They were worried about differential shrinkage causing shears above that. As an aside the defunct plant is now a superfund site . I've planed off the resorcinol squeeze out with no problem on another manufacturer's beams to turn a non appearance into a dressed beam.