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Thread: Bending Radius of Plywood?

  1. #1
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    Default Bending Radius of Plywood?

    Can anyone advise on the likely minimum bending radius of 1/2" ply (and of 3/8" as well if you can)?

    I would like to avoid designing too tight a curve and having to heat the stuff.

    I have had a look at some of the threads here and cannot find a similar title. I have also had a look on the tainternet, without reliable results.

    Thank you very much.

    Collin

  2. #2
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    Default Re: Bending Radius of Plywood?

    "If it ain't broke, you're not trying." - Red Green

  3. #3
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    Default Re: Bending Radius of Plywood?

    Quote Originally Posted by CollinR View Post
    Can anyone advise on the likely minimum bending radius of 1/2" ply (and of 3/8" as well if you can)?

    I would like to avoid designing too tight a curve and having to heat the stuff.

    I have had a look at some of the threads here and cannot find a similar title. I have also had a look on the tainternet, without reliable results.

    Thank you very much.

    Collin
    Hey Collin,
    In our "The Birth of the Night Heron" postings we posted photos of a contoured transom seat we built using bent 3/8" (9.5mm) plywood for the seat-back. We used the ambient conditions here in Florida, heat and humidity and a plain rope to give the BCX ply the bend. We used BCX because it's economical, will take a good bend and is exterior grade. The C surface can be finished with a good epoxy based primer if both sides are to be seen. We didn't use 1/2 inch (12mm) ply as it was unable to be bent as easily to the contour we were trying to achieve.

    Here are those photos - in case you haven't seen them before.
    Bending Ply.jpg
    We could've bent the ply tighter than the radius shown here - we experimented and bent it to, approximately, a 10 inch (25cm) radius after the ply was out in the elements for three days.

    Here is the seat we built that we call the contour transom seat unfinished.
    Friday 5.jpg

    The starboard finished seat is shown in this photo.
    Trim Pieces Topside Painted.jpg

    Hope this steers you in the right direction.

    Stay safe, stay healthy.

    J.
    "Ships are the nearest thing to dreams that hands have ever made." Robert N. Rose

  4. #4
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    Default Re: Bending Radius of Plywood?

    Quote Originally Posted by Garret View Post
    I have foudn that meranti ply will bend almost like rubber, until it doesn't. And you don't get a crack, you get a sudden break.

  5. #5
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    Default Re: Bending Radius of Plywood?

    If it's not a major structural component and is completely incapsulated wacky wood is fun to work with.




    https://www.boulterplywood.com/FlexiblePlywood_4.htm

    http://packardforestproducts.com/bending-plywood/
    Last edited by woodpile; 11-02-2020 at 09:05 AM.

  6. #6
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    Default Re: Bending Radius of Plywood?

    Thanks folks,

    The idea is to design a boat that conforms to the properties of the material used (decent ply, probably marine), and not to force the ply into tight curves.

    So Garret, many thanks for your suggestion, the prize for the best answer goes to you. Peb and J, perhaps I should have reworded the question, I wasn't looking to force the stuff (I enjoyed your Night Heron thread, J, though hot and humid is only partly right in Scotland). Woodpile, that stuff looks like fun, but I wouldn't want to be butting a head sea in the Minch in a boat made of that stuff, and neither (I suspect) would you.

    So thanks again, keep healthy,

    Collin

  7. #7
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    Default Re: Bending Radius of Plywood?

    A trick that I've used where a glued plywood lapstrake plank has to be massaged into a very tight curve, is to cut the sheet corner to corner and cut the plank along that diagonal. In my experience that will take a tighter curve than the normal orientation.

    John Welsford
    An expert is but a beginner with experience.

  8. #8
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    Default Re: Bending Radius of Plywood?

    Quote Originally Posted by john welsford View Post
    A trick that I've used where a glued plywood lapstrake plank has to be massaged into a very tight curve, is to cut the sheet corner to corner and cut the plank along that diagonal. In my experience that will take a tighter curve than the normal orientation.

    John Welsford
    That's "on the bias", in dressmaking!

    Andy
    "In case of fire ring Fellside 75..."

  9. #9
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    Default Re: Bending Radius of Plywood?

    The idea is to design a boat that conforms to the properties of the material used (decent ply, probably marine), and not to force the ply into tight curves
    Google: hull design; developable surface.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  10. #10
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    Default Re: Bending Radius of Plywood?

    I have no idea, but I would look at Dudley Dix's designs which are curved plywood, I believe.
    Good luck, keep us posted.

  11. #11
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    Default Re: Bending Radius of Plywood?

    Google, conical surface development.

  12. #12
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    Default Re: Bending Radius of Plywood?

    Google, conical surface development.

  13. #13
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    Default Re: Bending Radius of Plywood?

    Breakaway and Seagull, thanks for the suggestions, I've got a thread running about conical projection on this forum, with some useful replies.

    John and AndyG, yes, good idea, though I'll try to design things so as not to need to.

    Thanks to all, keep safe,

    Collin

  14. #14
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