Bending Wood

I have developed a system for bending wood for my arch bridges, and though I do not claim it is the best way, it works well. It does require some materials and equipment that hopefully you will already own and not need to get.

I have a pot, or basin rather, that is about 18″ long and 12″ deep. I fill it with about two cups of water (I have found that more water just takes longer to start boiling, and I usually don’t boil all of it anyway) and stick it on a stove burner. Currently I am using a stove that has a glass top and the burners are underneath, but in the past I have used one that had burners above the top of the stove.

I place any wood I am steaming on top of the basin, I usually have at least one or two pieces that are longer then the basin and some that are shorter, but the shorter ones lay on the longer pieces so that nothing is actually touching the water at this time, for the goal was to steam and not soak the wood. I turn the burner on high, and wait for the water to start boiling. I also place a shallow cookie sheet on top, to hold in the steam.

I have never steamed my wood for over a half hour, perhaps I am too impatient. But with this amount of time the wood is very bendable.

Beforehand, I have prepared two “molds” that consist of two sheets of wood, with a form of nails hammered into each, to mold the steamed wood. I have taken to making the mold a half inch or so taller then what I want the actual height of my arch, because the wood always bends a little less then the form afterward. You may want to use more or less extra height depending on the overall height of your arch.

This form is fairly easy to make, I just set the height and length of what I want with nails, and then bend a stick of wood (usually 1/16″ by 3/16″) and hold it in place by clamping the wood to the nails with clothespins. I then add as many additional nails to the form as I see fit, along the arch of the wood.

After steaming the wood I clamp the pieces to the form and wait another thirty minutes to an hour for it to dry. Again I may be impatient, but it works for me. I then apply glue to the wood, and wait 4-5 hours for it to set (that is the amount of time my glue takes to set). I then do a little sanding, and finish building my bridge. So far, I have built an 8.5 gram bridge (as of Jan/19/04) that held 16k and broke. However, the testing apparatus was not ideal, in the fact that I forgot to bring an S hook to the place I was testing, and had to make do with something else, which I believe may have unevenly applied the load to my bridge. But then again, that may not have been the case.

I usually make my arches into the shape of an L beam, but have used a T beam in the past. I have never used an I beam, though that would most definitely be stronger but heavier. It is worth experimenting with.

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14 Responses to “Bending Wood”

  1. first timer - October 18, 2008 at 9:47 am

    This Method is A+!!!!

  2. shawna - December 3, 2008 at 11:37 am

    thanks like the others said this was really he3lpful lol thanks

  3. Dave - January 8, 2009 at 9:33 pm

    Some notes from round 1 bending:
    Tried steaming long pieces over jelly roll pan of water in oven, but even covered didn’t get enough steam. (Was covered with 2nd pan.)
    Finally steamed on two stove burners.
    One piece had gotten wet and was the most pliable.
    When we tried clamping to nails used for the form, the balsa squished.
    Another piece was not all the way steamed and bent. I think it would have not bent if we put the bending stress over more points and fingers.

    Hope this helps others trying this.

  4. first timer - January 18, 2009 at 9:11 pm

    Hey Garret,

    Can you post a picture or blueprint of the bridge. I would love to try it out

  5. Ed Jolliffe - February 18, 2009 at 7:21 pm

    My arch will require me to glue my popsicle sticks together before I bend it. Will this work?

  6. Cris - March 24, 2009 at 7:30 pm

    im not doing a balsa wood bridge project ( did it already) but is this also useful way for making the wood bend into a shape of a circle?

    • Garrett Boon - March 25, 2009 at 2:41 pm

      Cris, yes. You could use this method to bend wood into a circle.

  7. James - June 14, 2009 at 11:05 am

    Can you please post a picture of the mold?

  8. Jessica - October 26, 2009 at 5:32 pm

    Is there a faster way of bending wood? THANK YOU FOR THE HELP!

  9. Matt bonner - December 23, 2010 at 8:06 pm

    I am going to ITT- tech in KC, we want to have a bridge building contest. I was wondering if there is a standard set of rules and if so, can you e-mail them to me of tell me where I can find them.

    Thank you,
    Matt

  10. Ric Ephraims. - June 7, 2011 at 8:30 am

    what about a long length of wood, say finger jointed pine or treated pine, 45 by 45. is it able to be bent by wetting and clamping? or by steaming in a basin at point of arc, then wetting and clamping? cheers.

  11. Josh - November 17, 2013 at 6:30 pm

    Can you explain what L-beams, T-beams, and I-beams look like in a bridge structure or redirect me to an article or something that explains those? Thanks.

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