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Thread: Steam bending issue

  1. #1
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    Default Steam bending issue

    I had originally figured a 10" board would be wide enough to get the arched 3.75" wide combing on this CY. After laying the final pattern on it I see now I really need 12". This clear piece of air dried oak was not so easy to come by and I was wondering if one could edge glue (yellow waterproof) a strip on to it before bending it. Any opinions on whether it would stay together in the steam box much less bend uniformly together?

    Have done very little steam bending and my guess making this in two pieces and spliced at the past partners, where the bend is the sharpest..would be almost impossible to get fare? Thanks -Dan-




    boat3.jpg

  2. #2
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    Default Re: Steam bending issue

    I would bet the price of a 10" board that you could rip it down to 4" and steam bend the 4" piece to this shape. If I am wrong, there are any number of folks here who will enthisiastically correct me. Steam bending is not difficult. Wallpaper steamers are convenient.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  3. #3
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    Default Re: Steam bending issue

    I once steam bent a piece that had been glued up with resorcinol. It did not seem to degrade the adhesion, but the glueline did not reliquify, and therefore created an area that didn't want to bend as readily as the softened wood. In the end, being a mild bend, it worked... with a bit of work... but that rigidity is something to be aware of. Also... I never did check with their tech folks to see if this was an approved process. I was in a bind and just did it. For all I know - heat does something bad chemically. No complaints from the client in the dozen years or so he owned the boat. I'd check that out before I did it again, though.

    Also - another boatwright, who I sometimes hire to help on a larger project - told me that he had spoken with Franklin, and was told that Titebond III WOULD soften above a certain temp. Maybe 120 or 140F?? Which was always my impression, and would have eliminated it from consideration for me. But, apparently, if heated above the magic number, than cooled, it engaged some sort of next-stage cross-linking - making it super strong when cool. He hadn't tried it himself, so I don't know if the heating/cooling also makes it brittle - which would be my next question. Another one to confirm with tech support before trying.
    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)

  4. #4
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    Default Re: Steam bending issue

    Glue up a test piece and steam it for the same amount of time it will take to do the final combing. Bend the test piece and see what happens, it's the only way you will know if it works or not.

    After all the work you put into that boat I would not use s edge gliued combing though. The grain will never match 100 % and it will show. Combings are highlights and draw attention to the observer automatically.

    There are a lot of saw mills in the north east, you should be able to buy a green board the correct dimensions without difficulty. It will bend much easier than dried oak and your combing will be dried by the steam.

    Kiln dried lumber is all dried by steam and it hardens the boards. Steamed lumber doesn't accept a second steaming well.

    In the commercial lumber business each kiln load must be started and finished without interruption and cooling. If a kiln shuts down during the process the load is ruined with case hardening. Steam doesn't penetrate the wood easily once this occurs.
    Last edited by navydog; 04-16-2018 at 09:40 AM.

  5. #5
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    Default Re: Steam bending issue

    My money is on Resourcinol for being the only glue that would hold up.
    Any chance for steaming and then edge gluing? That would complicate the clamping process as the precision will need to be dead on, but it could be done. Just give yourself extra width for final trimming after the gluing.

  6. #6
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    Default Re: Steam bending issue

    I question whether glue can really stand up to bending across the joint. The compression on one side and expansion on the other has to place tremendous stress on the glue.

  7. #7
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    Default Re: Steam bending issue

    Resorcinol would be the best glue to use.

    The pattern probably resembles a long "U", which means that the extra width could be sawn from the top edge of the board and glued onto the bottom. I'm talking about the ends of the board.
    Put the joints on the ends as this area will probably bend in without steam, if you're lucky. Saw the piece close to the pattern before steaming so you're not trying to bend extra width.

    Good luck.

    Jim

  8. #8
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    Default Re: Steam bending issue

    And of course sawing it after it is bent and shaped is a lot harder, not impossible but you wont want to do it.

  9. #9
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    Default Re: Steam bending issue

    To save wood and to avoid grain runout on both the top and bottom, most pros make this out of two pieces with an elegantly shaped and vanrnished butt block at the center join. Most of the time an "outside" butt block is better and sometimes two butt blocks, inside and out, are best.

  10. #10
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    Default Re: Steam bending issue

    Scuppered gunnels? look great but will let water in seems a shame to make them splash rails.

    Suggest resaw the plank into thin wide as you need them strips. If you keep them in order as cut the glue lines will be near invisible I'd not hesitate to steam bend green WO but never kiln dried. Ash (because it's not below the water line_ could be easier to obtain.



    http://forum.woodenboat.com/showthre...d-Tricks/page2
    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: Steam bending issue

    I think that if you rip out a piece of 4.25 inch with as much of the edge set as possible sawn into it (a curved board) then plane it to thickness then weight it and sink it in a pond for a couple of weeks before steaming and clamping into place you will stand a pretty good chance of being able to bend the rest of the edge set on the hull IF you have a couple of competent helpers on hand and all of your clamps and blocks and any other paraphernalia well set up and placed. A wide thin piece like that is going to lose it's heat really quickly, you'll have to work efficiently.

    It might, probably will in fact, be to your advantage to steam it in lay flat poly tubing, that way you can keep it hot while you work.

    You will lose some of the edge set when you remove the clamps, but since the work would be wider than necessary you will be able to slide it down rather than try to re-edge set it cold when fastening into place.

    If you find that once it's in place it's a little narrow and therefore low in the middle perhaps you could bend a dadoed cap on top to increase the height a bit. A cap that's a bit wider than the coaming's thickness and is glued in place provide's a pretty good hand hold.

    Green lumber will be much easier to work with.

    I like Denise030 set up above. It could be improved by adding blocks extending into the cockpit from the bottom surface of the ply to act as height guides, just push or pull the work down to the blocks to achieve the correct edge set. I would also screw or bolt the vertical blocks to the ply to free up more clamps and get the ones that are in place out of the way so that the clamps you apply to pull the work into shape can extend forward and out to the sides rather than into the cockpit where they will interfere with each other.
    Last edited by Gib Etheridge; 04-16-2018 at 04:54 PM.

  12. #12
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    Default Re: Steam bending issue

    I didn't see your photo when I opened this thread. How in the heck are you planning to clamp the coaming in place, and how are you going to fit it around the partners? Maybe on a remote form? Maybe remove the staving on the bulkhead?

  13. #13
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    Default Re: Steam bending issue

    It would only require removing a few of them. Well maybe 10. With deep throat clamps he could come in from the top by removing pieces of decking.
    Last edited by navydog; 04-16-2018 at 03:47 PM.

  14. #14
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    Default

    Quote Originally Posted by Gib Etheridge View Post
    I think that if you rip out a piece of 4.25 inch with as much of the edge set as possible sawn into it (a curved board) then plane it to thickness then weight it and sink it in a pond for a couple of weeks before steaming and clamping into place you will stand a pretty good chance of being able to bend the rest of the edge set on the hull IF you have a couple of competent helpers on hand and all of your clamps and blocks and any other paraphernalia well set up and placed. A wide thin piece like that is going to lose it's heat really quickly, you'll have to work efficiently.

    It might, probably will in fact, be to your advantage to steam it in lay flat poly tubing, that way you can keep it hot while you work.

    You will lose some of the edge set when you remove the clamps, but since the work would be wider than necessary you will be able to slide it down rather than try to re-edge set it cold when fastening into place.

    If you find that once it's in place it's a little narrow and therefore low in the middle perhaps you could bend a dadoed cap on top to increase the height a bit. A cap that's a bit wider than the coaming's thickness and is glued in place provide's a pretty good hand hold.

    Green lumber will be much easier to work with.

    I like Denise030 set up above. It could be improved by adding blocks extending into the cockpit from the bottom surface of the ply to act as height guides, just push or pull the work down to the blocks to achieve the correct edge set. I would also screw or bolt the vertical blocks to the ply to free up more clamps and get the ones that are in place out of the way so that the clamps you apply to pull the work into shape can extend forward and out to the sides rather than into the cockpit where they will interfere with each other.
    Oh, thank you Gib, but it's not mine, it's a copy from a long-running thread on this forum.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  15. #15
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    Default Re: Steam bending issue


  16. #16
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    Default Re: Steam bending issue

    As Jim mentioned you can certainly cut a wedge off each end and glue it to the opposite edge.

  17. #17
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    Default Re: Steam bending issue

    Yes I like that idea of Jim's as well and will probably give that a go. Was also planing on clamping it to a form so I don't have to wrestle it in place when its time to fasten (thanks to Rich Jones build)

  18. #18
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    Default Re: Steam bending issue

    You probably already know this, but if I was doing this I would cut the notch after steam bending, it'll snap otherwise. It's a pity you can't remove the mast gate and put it through holes in the steamed coaming after the coaming is bent in.

  19. #19
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    Default Re: Steam bending issue

    No, did not know it would be best to cut the notch...later. Thanks for that, most definitely a better idea. What is missing in the pic yet is a "bump" (?) block which sits below the mast gate against the t&G and keeps the mast away from the combing etc. Thus the notch will snug up to that below

  20. #20
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    Default Re: Steam bending issue

    That notch would concentrate the stress of the bend into one particular area, something to avoid.

    Another thing I like to do is to bend the piece in with a little bit of extra width, say a quarter or half inch, to leave some wiggle room. Then I like to take a router and a small round-over bit along all four edges. This rounding-off removes small irregularities that act as crack starters. There seems to be two ways that bendings fail. There's a sudden catastrophic snap that is often the result of grain runout, and there's the kind that starts with a little sliver popping up on an outside corner which then runs into the plank and causes it to fail. The rounding of the edges is an attempt to mitigate the last cause.

    Jim

  21. #21
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    Default Re: Steam bending issue

    As Jim has said, the notch will be problematic. If bent with the notch the wood will split right at the corners. This is due to the board wanting to cup (bending across it's width) as it is bent. The cupping acts like a tearing motion. Your bend is not unlike that encountered in circular or spiral staircases. Cupping is always anticipated on those projects.

    I suggest that you cut out a sample coaming from some lesser/cheap wood. Something that will bend dry yet still has some thickness to it. Even if this breaks the bend will show you what is happening to the board, how the bending is affected in three dimensions. You will learn a lot from this exercise.

    Jeff

  22. #22
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    Default Re: Steam bending issue

    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  23. #23
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    Default Re: Steam bending issue

    We used four layers of laminates for this. The glue is G/flex and is invisible. Herreshoff used solid Eastern Rocl Elm for this kind of bending. More flexible than oak it is whippy and easy to steam bend. Eastern rock elm is hard to find though.
    Jay

  24. #24
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    Default Re: Steam bending issue

    Honduras, Jay? Just how thick were those laminates individually?

    Jim

  25. #25
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    Default Re: Steam bending issue

    Quote Originally Posted by Dmq400 View Post
    Owwww,....... yes, that notch won’t make it. Definitely would need to cut it after bending, and sitting for a while.

    When I was building these as I remember we used four 1/16” mahogany veneers for a finished 1/4”.
    Attached Images Attached Images
    Last edited by nedL; 04-17-2018 at 12:55 PM.

  26. #26
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    Default Re: Steam bending issue

    Quote Originally Posted by Jim Ledger View Post
    Honduras, Jay? Just how thick were those laminates individually?

    Jim
    Yes, it is Honduras. The finished rail was half inch thick when finished so the lams were roughly 1/16". I would have preferred to use Rock Elm but we could not find any.
    Jay

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