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Thread: bending green wood

  1. #1
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    Default bending green wood

    I have an opportunity to obtain some fresh sawn black cherry and planned to air dry it of a year or so. But I was wondering if wood can be steam bent green?

    Anyone had any experience with this?

    David
    Ipswich, MA

  2. #2
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    Default Re: bending green wood

    Green is definitely preferred for steam bending.

    (I don't know how well cherry bends, I have never tried it, but I'm sure others have a lot of experience with it.)

  3. #3
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    Default Re: bending green wood

    Excellent! I've been told that cherry bends quite well.

    Thanks nedl

    How long should one leave it clamped and will it move after?

    David

  4. #4
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    Default Re: bending green wood

    Leave it until cold. It may spring back, but if you bend it over a form with a tighter radius you can take some over bend out by hand.
    It really is quite difficult to build an ugly wooden boat.

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  5. #5
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    Default Re: bending green wood

    Thanks Nick,

    So basically treat it as air-dry wood?

    David

  6. #6
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    Default

    Quote Originally Posted by DMBryant58 View Post
    Thanks Nick,

    So basically treat it as air-dry wood?

    David
    David what was the size boards that were air drying? it's basically one year per inch,

    What would you be making that is bent stems? frames ?rails? I have some very air dried cherry that I sliced up for laminations, soaking it in water was all I needed to do. I like how it bends for laminations not as great as Ash or White Oak, but acceptable

    Sent from my LG-M430 using Tapatalk
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  7. #7
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    Default Re: bending green wood

    Keep in mind that the steaming will hasten the drying considerably. Green cherry should bend into pretzels when its been steamed. The longer it stays on the form, the less sprinback there will be.

  8. #8
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    Default Re: bending green wood

    Quote Originally Posted by willin woodworks View Post
    Keep in mind that the steaming will hasten the drying considerably. Green cherry should bend into pretzels when its been steamed. The longer it stays on the form, the less sprinback there will be.
    That's almost true. If you take it off the form before the stick has cooled all the way down, and before the lignin has re-set, the springback will be magnified. Once it's set, however, leaving it on the form will have no effect. When doing production bending - we sometimes set up 'drying jigs' in addition to the bending form. Bend, let set a while, than snap on a drying jib and set aside to make room for another piece on the bending form. For the size of stock we work with - overnight, or over two nights - is sufficient. But there will always be a bit of springback. How much depends on things like: thickness of stock, tightness of bend and species of timber. You can largely compensate for it, as mentioned above, by making the radius of your bending form a bit smaller. There are formulae available online for calculating the required adjustments.
    Last edited by David G; 03-05-2018 at 01:36 PM.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  9. #9
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    Default Re: bending green wood

    Denise,

    I'm building a 14' catboat and want to use the cherry for the combing which I'll bend in an arch at the forward cockpit then straighten out aft to the transom ala Beetle Cat. I plan to bend it in place.

    David

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    Default

    Quote Originally Posted by DMBryant58 View Post
    Denise,

    I'm building a 14' catboat and want to use the cherry for the combing which I'll bend in an arch at the forward cockpit then straighten out aft to the transom ala Beetle Cat. I plan to bend it in place.

    David
    Cool would love to see it,. Bending in place is not without problems. That would be a pretty large radius wouldn't it?

    Sent from my LG-M430 using Tapatalk
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  11. #11
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    Default Re: bending green wood

    Denise,

    Yes about a 30" radius. I admit I'm a bit apprehensive, but I don't want to build a 5'x6' jig if I can avoid it. The combing will only be about 5/8" thick but 3" wide so I'm worried about twist and warping. Any Ideas?

    David

  12. #12
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    Default

    Quote Originally Posted by DMBryant58 View Post
    Denise,

    Yes about a 30" radius. I admit I'm a bit apprehensive, but I don't want to build a 5'x6' jig if I can avoid it. The combing will only be about 5/8" thick but 3" wide so I'm worried about twist and warping. Any Ideas?

    David
    Could you make the form out of the deck framing and then put it in the boat afterwards?


    Sent from my LG-M430 using Tapatalk
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  13. #13
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    Default Re: bending green wood

    Denise,

    So do you mean build the deck framing outside the boat, use it as a form to bend the combing into then install the entire assembly? That might work.

    I had planned to install the combing after the decking was on. But now I realize that I having the deck framing to clamp to would be a major benefit.

    I have a few months to think about so I'll mull it over...

    David

  14. #14
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    Default Re: bending green wood

    Given the working time you will have I would recommend a form to bend around.

  15. #15
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    Default Re: bending green wood

    Nedl,

    Well, I wanted to avoid the extra work of building a form the size required but I suppose once again it's always easiest to do the the hard way.

    David

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    Default Re: bending green wood

    Quote Originally Posted by DMBryant58 View Post
    Nedl,

    Well, I wanted to avoid the extra work of building a form the size required but I suppose once again it's always easiest to do the the hard way.

    David
    Such is often the case. But not necessarily in this case. Using the boat for a form is not a bad one, if you can arrange it. What makes it workable is that - no matte how much fussbudgets like me want to achieve absolute precision - the reality is that if your bent piece is just 'pretty close' to the final shape needed, it will very likely then flex into final position.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  17. #17
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    Default Re: bending green wood

    "a few months"...It will be dried out by then and much more likely to break when you bend it, especially if it is not very straight grained and flat grained. It would be nice to keep it saturated until steaming time. I would find a way to keep it under water until then, and I do mean under water, where there will be no oxygen so that it is less likely to discolor.

    5/8" by 3"....If you have a crowned deck you may want to start with a wider piece and fit it to the crown when you install it, 3" won't edge set very well.

    I would laminate up some curved frames to describe the bend between the deck beam and the side decks. That will give you framing to support the after ends of the decking and to clamp then fasten the coaming to.

    A separate female mold to bend to will be much much easier than bending to the inside of framing.

    If possible you should have 2 or 3 pieces to bend in case the first 1 or 2 break. If you can back the piece with a piece of full width metal, on the outer face that is, while bending it you will lessen the odds of breakage considerably. Another way to accomplish that would be to bend it in 2 or 3 layers then laminate.

  18. #18
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    Default Re: bending green wood

    If you work alone and bend first the starboard side then the port side onto a female mold the port side will have cooled quite a bit and will not take the bend as well. Then when you remove it from the mold the port side will spring back noticeably more than the starboard side and you will have a bit of a time of it getting it to fit. Best to get a helper and get it clamped to the form as quickly and evenly as possible.

  19. #19
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    Default Re: bending green wood

    Quote Originally Posted by DMBryant58 View Post
    Denise,
    So do you mean build the deck framing outside the boat, use it as a form to bend the combing into then install the entire assembly? That might work.
    I had planned to install the combing after the decking was on. But now I realize that I having the deck framing to clamp to would be a major benefit.
    I have a few months to think about so I'll mull it over...
    This is a good place to use the poly bag method of steaming -- some good videos on the method:

    https://www.youtube.com/watch?v=--iPQIwSEJM&t=11s

    https://www.youtube.com/watch?v=50uXPPt8-VI&t=31s

    http://forums.wcha.org/index.php?thr...99/#post-66199

    You don't have to worry about a large piece of wood cooling off before being properly clamped in place. If you go this route, have a good source of steam -- a wall-paper steamer is not enough.

  20. #20
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    Default Re: bending green wood

    I had a 30 lb flat bow made out of air dried cherry and it drew and flexed for over a year before it started to fail in compression on the belly side. I'd think a 30' radius should be zero problem!

  21. #21
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    Default Re: bending green wood

    You will have a better chqnce of getting a good lam by bending on a form as opposed to in place. There will be more room for clamps, you can walk around it, you wont be doing any yoga trying to keep things in place. I would make the lams wider as has been suggested so you have some trim room.
    Depending on the glue you choose you will want to plane the lams nice and smooth or leave the faces "Sawn" for the best adhesion. Id opt for TB3 so you can minimize the glue lines and hide the lamination.

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