I am making a twin size bed for my daughter, and the design calls for a maple curved piece on the head, and foot boards. I have decided to try bent lamination, and will make an DF form, and use clamps. My questions are… what type of glue to use. if urea? is it toxic? this is a kids bed so the formaldehyde part made me nervous. And, is there a way to prepare the thin strips of wood with a planner? some type of bed for thin pieces to ride through on? I do not have a drum sander, and doubt there is any way I could prepare the strips by hand. How thick should the plys be? Any other tips any one can offer? Thanks!
Edited 7/17/2003 1:34:39 PM ET by SQUEAKY_JEEP
Replies
"what type of glue to use?" Use a glue that doesn't creep. Yellow glue creeps. Urea-formaldehyde is often used for bent lamination because of this. Cured urea-formaldehyde is not toxic -- that is, you can eat it without poisoning yourself.
"the formaldehyde part made me nervous." There's three answers to this. First, the formaldehyde is supposed to be all gone from the cured glue. Second -- and this is more significant -- there is just very little glue in bent laminations. The glue line is a few thousandths of an inch thick, and there are only a few of them. This is very different from MDF or other manufactured panels, where glue is a much much larger fraction of the product. And third, if the first two arguments don't satisfy you, use epoxy. Epoxy is more expensive than U-F, and as a practical matter you can't clean mixing tools, but it has many of the same characteristics as U-F -- no creep, long open time (with the right catalyst), and waterproof when cured.
"some type of bed for thin pieces to ride through on?" Well, maybe. At some thickness you have to use carpet tape to stick the thin pieces to the sled, otherwise they'll get sucked into the cutterhead and destroyed. At that point, you may find you can't get them off the tape without destroying them.
"doubt there is any way I could prepare the strips by hand" Yeah, you want the faces of the laminates to be nice flat faces, otherwise you'll see thick glue lines.
"How thick should the plys be?" Thin enough to bend around your curve. Try making test laminates of different thickness and bending them to your smallest radius. Use the species that the finished piece will be. One more thought: the amount of springback depends on how many layers you're laminating. If you use only two or three layers, you'll get more springback than if you use five. Springback isn't a bad thing, it is just something you may want to allow for. For seven or more laminates, there is almost no springback.
Oh, you can most certainly flatten the laminations by hand. Surely you don't believe that the process was only made possible by the advent of electrical tools? Careful sawing out makes the process much easier if you decide to flatten by hand.
The thickness of the the each ply depends on the severity of the curve. Springback can happen with a bent lamination, several very thin plies minimizes the problem as has been mentioned. This may not be an issue with your project. If you could post a picture or drawing we could tell you. If the lamination is to be applied to another part of the project, any minimal springback can probably be handled at the stage in which the parts are to be afixed. I would venture a guess that you couldn't go too far astray with plies around 1/8" thick, but I haven't seen a drawing.
Urea formaldehyde is fine. Epoxy would be fine, too. Put yellow glue out of your head, as another poster mentioned.
Edited 7/17/2003 4:16:09 PM ET by BossCrunk
The thinner the strips, the less spring back and hence the less load on the glue. So make the strips thin and then yellow glue will be fine. Pull the strips dry around the form and if you have to "put your back in to it" then cut the strips thinner.
I just finished some rocking cradles where I laminated 1/8" walnut between curly maple pieces (to get a unique look ... the pieces ended up being slightly thinner than 3/4"). The walnut went through my planer on a "sled" and the only problem was tearout at the end when the piece had the grain going the wrong way. The dimensioning was perfect. What I'd do is cut pieces that are at least a foot longer than you need (two feet would be better) and plane away.
If you get them to 1/8" you slhould be able to make any curve you want without springback. As suggested above, make some tests to see how thick the laminations need to be.
John
"The thinner the strips, the less spring back"
Not to nit pick, but springback is related to the number of strips used, not the respective thickness. The more laminations used, the less the springback (inversely squared, I think).
Scott
Thanks for all the help. I think I am ready to give it a try. Boss- no, of course I don't belive that it was not possible to do bent laminations untill the advent of power tools, only that my very limited to nill expertise of hand tools would lead me to shy away from trying to do it this way. As others have said it sounds like how the stock is prepared before glue up directly relates to the quality and longivity of the joint. I guess I need to work on that though. Thanks again for all the info!
Best of luck, SJ. You can fashion little carry board (and you might not need that) to plane the lams on the ubiquitous portable 12" planer. I've done it without much problem, althought it's been a while.
When you need to plane to less than 1/8" you might need a "spacer table" to use inside the planer. Always make too many thin strips and take a thin cut when getting down to final thickness. face the spacer with standard finish formica (not gloss) some strips will get Eaten by the planer instead of "thinned". Its not as tough to do as it seems.
I've recently become aquianted with the joys of adult onset asthma, aren't I lucky?
I'm very sensitive to irritants (like my supervision) and know that my lungs react to formaldehyde. So I have to avoid the entire class of urea/formaldehyde adhesives even though they are very good glues.
I use west systems epoxies for lamination and have had good results so far. No creep, absolutely water proof, and very good joint filling. I thicken with sawdust or with west's chopped cotton fiber filler (I don't remember the official name, another symptom of advanicng age).
Note that epoxies can also be VERY sensitizing, especially to the skin. The sensitivity goes away when it's fully cured (24 - 48 hrs). Cover up well with nitrile gloves and long sleeves. If you sand before the epoxy is fully cured, use good respiratory protection.
You can get the strips to about 1/8" with most thickness planers. That'll give a pretty good radius. Remember that only the faces need to be really beautiful - the inner plys can be plain grained strips of the same species and color. I use a drum sander to get below 1/8". A piece of plywood with a thin fence glued to one end holds the thin strip as it goes through the drum sander.
If your bend lamination doesn't have to be very wide, try cutting with a very good blade in a well adjusted table saw.
Edited 7/21/2003 1:01:33 AM ET by telemiketoo
What I did for a project several years ago was to cut the plies from a sheet of veneer. The veneer was a consistent thickness so I had no need to resaw, thickness, etc - just had to make the form, apply the glue and clamp up.
This forum post is now archived. Commenting has been disabled