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Thread: 2" Steam bent white oak frames

  1. #1

    Default 2" Steam bent white oak frames

    If I'm designing a round bottom cruising sailboat with 2" white oak frames, is it practical to use steam bent frames? Or, should I laminate all the white oak frames? The frames will be finished bright.

    This is a boat I'm drawing the plans for myself since I can't figure out where to buy a set of plans for the design. It's a 26' LOA, 9' beam, 4'6" draft, 45 square meter spidsgatter (Danish double-ender) design by George Berg. What I have to work with is a photo of the lines from a body plan and a construction drawing that is in profile view. I believe the design originally called for larger sawn frames at 22" on center with two smaller steam bent intermediate frames. I do not want to use sawn frames. My plan is to build molds, Herreshoff style, at 12" on center and bend the frames. After they've set up for a while bent, I plan to remove them from the molds and run them through the planer so that the sides are square to the floors, deck beams, and bulk heads. The frames will be originally bent oversized so that they are finished to a 2"x2" dimension.

    If anyone can give me some guidance on the sizes of structural members for this project, I'd sure appreciate it. Or, direct me to some publication that can help me. Once I've finished the plans, I will have a naval architect review the drawings before I proceed with construction.

  2. #2
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    Default Re: 2" Steam bent white oak frames

    I've never understood the reason for lofting and building a separate mold for each frame when 1/3 as many molds combined with ribbands will do the job so much more easily.

    Also, I cannot imagine how running the frames through a thickness planer will shape the fore and aft edges to be perpendicular to the centerline. I would just plan on shaping the faying surface of the floors and bulkheads to match the frames. Deck beams would be fastened to shelves and clamps.

    As for 2X2s being adequately sized, I don't know.

    I'm interested in hearing what others think of this.

  3. #3
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    Default Re: 2" Steam bent white oak frames

    How are you going to plank the boat? Plank style affects framing.(effects?)
    There are a few bona fide NA's here, I'm not one of em. When you ask for guidance....eh, I can only offer opinion.
    Laminating makes the best frame, imo.
    Oak is not the best wood to lame frames,imo.
    There is no point in doing the extra work of squaring up frames,unless they are sawn or being used as molds,imo.
    bruce

  4. #4
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    Default Re: 2" Steam bent white oak frames

    My initial thought is that 2" x 2" seems large for a 26ft boat. My boat, at 33 ft has 1" x 1 3/4" ribs on 7" centers,.... granted she is a power boat and not a sailboat.

  5. #5
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    Default Re: 2" Steam bent white oak frames

    Look harder for existing plans - for that boat, or for something similar for you to riff off of.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "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)

  6. #6
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    Default Re: 2" Steam bent white oak frames

    I was thinking pretty much the same as Bruce.

    If you are planning to use strip planking, edge nailed and glued, the 2X2s might be just the ticket, and you probably wouldn't need as many.

    On smaller hulls I'm inclined to laminate the frames oversized on the bench then run them thru the planer to clean up the edges, then trace the patterns on them and band saw and plane the inner and outer faces to match the patterns, then set them up as forms, then plane the outer bevels to match the planking.

    That sounds like a lot of work, and it is, but it works well for me.

    A problem you might have with my system would be bevelling the inner faces to accommodate ceiling, but if your hull doesn't have any that wouldn't matter.

  7. #7

    Default Re: 2" Steam bent white oak frames

    Quote Originally Posted by wizbang 13 View Post
    How are you going to plank the boat? Plank style affects framing.(effects?)
    Carvel planking. 1-1/4" Yellow Pine.

  8. #8
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    Default Re: 2" Steam bent white oak frames

    Quote Originally Posted by George Ferguson View Post
    Carvel planking. 1-1/4" Yellow Pine.
    Ahh, ... that explains it. (not lapstrake)

  9. #9
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    Default Re: 2" Steam bent white oak frames

    Lotta tricky curves in a spitzgatter.
    Sort of hard turn at the bilge,this is where steamed frames break,almost always.

  10. #10
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    Default Re: 2" Steam bent white oak frames

    I think a 2x2 frame is very large, and will be hard to bend. I've worked on two sailboats that had only bent frames. One was 29', the other 26', both Friendship Sloops. I remember that the 29' was built with 1.5" square frames, I think the 26 had 1x1.5. The weight and area of the frame section increases by the square. A 1.5" square has a section 2.25 square inches, a 2x2 is 4 square inches, almost twice as large.
    Good luck, keep us posted.

  11. #11
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    Default Re: 2" Steam bent white oak frames

    I suspect 2"x1.5" split would suffice. We built 35' lobster boats with that size frame spaced at 12". Yellow pine would not be my choice. It rots much to quickly and easily.

    So this part about making the frames a parallelogram. The angles change every couple of inches in every direction of the boat. From top to bottom and from front to back. There is no way to make all the edges 90* to the center line without extensive hand planing and fitting. Why bother at all?

    It is possible to put an angle on the side of a straight piece using the thickness planet using a jig. I put the cauking seam on decking that way.
    Last edited by navydog; 07-25-2018 at 12:28 PM.

  12. #12
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    Default Re: 2" Steam bent white oak frames

    "If anyone can give me some guidance on the sizes of structural members for this project, I'd sure appreciate it. Or, direct me to some publication that can help me."

    Books that should be in the library - or on your drawing board - for quick reference:







    All are available from our host.

    My advice: build your jig from molds and ribbands, not the Herreshoff method of a mold every frame; reduce the frame scantlings - square is overkill and too hard to steam bend; don't bother with trying to square the frames to the centreline, besides being egregiously fussy to do they won't look 'right' when done. But that is just my opinion, and is worth what you have paid for it. Good luck with your design/build endeavours. We expect pictures...
    Hope for the best, but plan for the worst.

  13. #13

    Default Re: 2" Steam bent white oak frames

    Quote Originally Posted by wizbang 13 View Post
    Laminating makes the best frame, imo.
    Oak is not the best wood to lame frames,imo.
    Why is oak not a good wood for laminated frames? I'd plan to use resorcinol. What would be your recommendations?

  14. #14
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    Default Re: 2" Steam bent white oak frames

    Oak glues up well with Resorcinol, provided that the glue line is fitted damn near perfectly (Resorcinol does not "do" gaps). An issue with oak is a.) acidity and b.) open pores. Acidity is not conducive for epoxy bonding, and pores suck the glue away from the glue line. Reasonable success can be achieved with epoxies if the glue line surfaces are wiped down with a solvent such as acetone just before laminating, but failures do occur even with this preparation. If you are going to use oak, glue up with Resorcinol, and have oodles of clamps at hand.
    Hope for the best, but plan for the worst.

  15. #15
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    Default Re: 2" Steam bent white oak frames

    Your original plan sounds like a very difficult way to build a boat. There is a reason nobody uses the herreshoff method. Bend them directly into ribbands over your molds and get on with it. Bevel floors to match where necessary.

    You can bend 2" frames, split down the middle. Without splitting you won't be able to fit those tight bends. I also think that is way too heavy, use more small frames if bent, few large ones if sawn or laminated.

    Dave Gerr's book above is easy to digest.

  16. #16
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    Default Re: 2" Steam bent white oak frames

    Laminate them to 2x2 with 8 layers of Alaskan Yellow Cedar to ribbands if you must go with those heavy scantlings. Make them too wide and take them out to plane the edges clean and square to the faces.

    You can achieve the parallelogram(ic) cross section, (once again if you must), by putting straight edges across and clamped down to the ribbands then offsetting and butting the edges of the veneers up against the straight edges. The edges will be stepped, but pretty easy to hand plane smooth.

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