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Discussion Starter · #1 ·
This is my first attempt at a bent lamination. It's 2.5 inches wide and 9 plys of 1/8" laminations. I'm making a headboard for a bed and wanted to cap the top curve of the headboard.

The headboard piece is 6/4 maple and after I cut the curve I used the headboard and the cutoff waste as the bending form.

So the two issues I ran into are that the lamination developed a Twist, and secondly, the lamination sprang back a bit and now doesn't follow the shape of the form. Any ideas on how to prevent this in the future?

For this piece, I am ok with the twist since it isn't too severe and I took some of it out with a block plane and a sander. For the shape not fitting, I will cut a dado into the lamination so it will fit over the headboard piece so you won't see the shape mismatch.

However, I'd like some suggestions on how to do this better next time.



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I have a few suggestions. I take my lams in sequence from the stock. IOW, I don't mix up the pieces. The thickness might benefit from making them a bit thinner. I block sand each lam on both sides to remove any fuzz, to get them smooth. Clamping only a few...like 2 to start makes clamping easier, and it's easier to control the sliding around. When clamping, getting even pressure, so one edge doesn't get more compressed than the other.

If it's possible to have a top form in addition to the bottom one, will help. Leave them clamped over night...or at least for a day.






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Anytime you bend wood in a form it straightens out a little when you take it out of the clamps. It's best to over bend one so it comes out of the press to about the desired shape. Having said that though it's a guessing game to say how much to over bend the part so I make that part first and then make the build fit the curved part. I would just reshape the headboard to fit your part.
 

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You need a more substantial form, one that will allow you to clamp down the pieces as well as to the shape. Use plastic resin glue to reduce creep and extend assembly time. Tight curves may spring back to some extent but it shouldn't be an issue with that head board. Rethink your construction methods. I might have cut the top piece out of the solid rather than laminate it in that situation.
 

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Anytime you bend wood in a form it straightens out a little when you take it out of the clamps. It's best to over bend one so it comes out of the press to about the desired shape. Having said that though it's a guessing game to say how much to over bend the part so I make that part first and then make the build fit the curved part. I would just reshape the headboard to fit your part.
If the pieces are glued to the bottom form there wouldn't be any springback. Using solid wood in one piece to do the top curve would require a fairly wide section. Shorter pieces could be scarfed to make the joints.





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Discussion Starter · #6 ·
Thanks for the suggestions. I really wanted to try this technique since I think it's very cool what some woodworkers are able to do with it.

I did use a top form and left it clamped for over 24 hours. I believe these parts are usable and that my best options are to either machine a dado in the Lams to get it to fit down on the headboard, or to drill and countersink screws through the top of the lams into the headboard to get the pieces to fit solidly then add another lam to hide the screws.

Thanks for your suggestions. Lessons for next time: use thinner lams, only glue up a few at a time, and glue them to the form during the glue up if that is how the finished piece will be.

Another lesson learned during this build: when making multiple parts, don't just crank out identical parts when there is supposed to be a left and right side piece. I love the learning curve I'm rapidly climbing as I try and learn new techniques. Thanks for sharing your experience guys!

Jeremy
 

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You've been given some good advice so far but I'll add my $0.02.

A bending form should have two sides. Also, ideally, the form should be a wide as the workpieces then it's easy to use a side clamp or two to get the lams realigned should they slip out around.

I make my bending forms heavy duty so that I can apply a lot of clamping pressure evenly and from both sides. I have found that chunks of old glue lam beam cut-offs work very well for bending forms. When cutting the forms to the desired shape of your finished curved piece, use a sharp blade on the band saw and make sure it is cutting square to the saw table. You will have to cut both faces of the form and figure the width of the workpiece when laying out the curve because the radius will be slightly different do to the thickness of the curved piece.

The tricky part is the springback and how to estimate it. The type of wood, the tightness of the radius, quantity and thickness of the individual lams all make for different springbacks. I've done a lot of this type of bending so I am pretty good at guessing but the range is from 1 to 5 percent.

Sometimes I'll add some metal tape or varnish to the faces to prevent the glue from sticking.

The only difficult part, IMHO, is the glue-up. I use Titebond II so I have a limited working time. To make sure it all goes smoothly I do a dry run and get all my clamps set to the right width and get everything all ready before I begin gluing. Once you start spreading glue there is no stopping. I pour a stream of glue on each face and spread it out to a thin coat with a short knapp mini paint roller. I like to see some glue squeeze out after clamping but too much glue and you'll have a mess on your hands and will have trouble with the pieces sliding around out of alignment.

Bret

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If the pieces are glued to the bottom form there wouldn't be any springback. Using solid wood in one piece to do the top curve would require a fairly wide section. Shorter pieces could be scarfed to make the joints.









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I don't see how you can say you can laminate wood like that and not have it spring back. What the OP is experiencing is what will happen every time no matter who does it. It is just a characteristic of wood to spring back when bent. Only when it is steamed and the cellular structure is altered the deflection is minimal.
 

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I don't see how you can say you can laminate wood like that and not have it spring back. What the OP is experiencing is what will happen every time no matter who does it. It is just a characteristic of wood to spring back when bent. Only when it is steamed and the cellular structure is altered the deflection is minimal.
If you read my post, the first line...If the pieces are glued to the bottom form there wouldn't be any springback.






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A bending form should have two sides. Also, ideally, the form should be a wide as the workpieces then it's easy to use a side clamp or two to get the lams realigned should they slip out around.
I will second what Bret just mentioned. I think this is the most important point. Two sided bending forms, equal width to the workpieces. Be sure to factor the thickness of the wood.

Line with packing tape. Set the whole thing on a table that is flat and covered in packing tape so that at least the bottom edges are lined up.

I am working on a demilune table with a bent lamination apron. It was my first bent lamination project, and they turned out great. I used the same process mentioned above.
 

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Discussion Starter · #12 ·
Thank you for all the great words of wisdom. I was able to get a good result and learned a lot during the process.

I ended up cutting the headboard curve again to closely match the lamination. I also cut a dado in the underside of the lamination so it fit right over the headboard. After lots if glue and clamps it looks great and feels very solid. It's not perfect, but I am very happy with the result and my daughter is so excited to see the progress.



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