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Thread: Herreshoff dinghy planking material/treatment questions

  1. #1
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    Default Herreshoff dinghy planking material/treatment questions

    I'm building the 12' Herreshoff Columbia dinghy, cedar on oak. I picked up a gorgeous load of clear Northern White Cedar. Unfortunately, none of it is wide enough for the garboards (min. 8"). It should be sufficiently wide for all the other planks. It took me months to find that cedar, and I know I won't be able to find anything wider.

    My backup plan is to use CVG Eastern White Pine for the garboards, and the cedar on the rest.

    My biggest concern is the rot resistance of EWP.

    If you were doing this, would you coat the pine with CPES, cuprinol, or something else to increase the rot resistance?

    Any other recommendations?

  2. #2
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    Default Re: Herreshoff dinghy planking material/treatment questions

    considering they are garboards would it be so bad to use something a little heavier that is available wide and rot resistant, say sapele, for the garboards?

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    Default Re: Herreshoff dinghy planking material/treatment questions

    Is the 8" width you mention as minimum for the garboard the width of the actual plank, or does it include some sweep? If it does include sweep, perhaps you could make the garboards up of 2 or 3 pieces with artfully angled scarf joints to follow the required shape.

    In any case, I would avoid using White Pine at all cost. You'd just be asking for trouble.

  4. #4
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    Default Re: Herreshoff dinghy planking material/treatment questions

    Both of those sound like good suggestions. I know you could get sapele or Douglas fir wider than 8" in pretty long lengths at L.Sweet here in Providence.

    Love to see some pix as you progress.

    Mike
    "near it, a small whale-boat, painted red and blue, the delight of the king's old age."

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    Default Re: Herreshoff dinghy planking material/treatment questions

    I'd talk to Will Poliquin in Exeter, Newport Naval Timbers or elsewhere, about Atlantic White Cedar. I think with the sweep in the upper planks you will need wider pieces in any case (Sorry to say this) and I believe that Herreshoff went to AWC as well. I think white pine is ok if air dried heartwood, there is a lot of twist coming into the bow so you likely have to steam whatever you are using.

  6. #6
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    Default Re: Herreshoff dinghy planking material/treatment questions

    You are not the only one who has had this problem. This is a Aidkin 10' dink built by Kevin Wambach of Lahave Marine Woodworking in 2003. The boat was, at the time, somewhat of a stock product for Kevin, and he built around a dozen of them, I believe. I think that I remember that the garboard plank is mahogany, but I can't be sure after all this time. I do recall Kevin telling me that he opted for hardwood both for the plank width and for its ability to be steamed into taking the extreme twist without splitting.

    dinghy planked & framed 2.jpg

    interior without outfit.jpg
    Hope for the best, but plan for the worst.

  7. #7
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    Default Re: Herreshoff dinghy planking material/treatment questions

    @Rob Hazard - Unfortunately dogleg scarfs won't get me the width I need for the garboard. Though I fully expect to have to do this as I get closer to the sheer where the sweep of the planks is greater (cc @Thad).

    I like the hardwood/Sapele suggestions for just the garboards too. I know NNT has Wana on hand as well. I had been hesitant about it for a boat with such light scantlings, but it sounds like it's okay for just the gardboard.

    @Thad - I've heard of this Will Poliquin character before (through the Tips from a Shipwright series) - how might one find him?

  8. #8
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    Default Re: Herreshoff dinghy planking material/treatment questions

    "mmd" took my first thought, as I was writing, and so I second his suggestion. My choice is Honduras as it will be slightly harder than the Eastern White Cedar but more friendly to work with than sapelli and will afford good service for this application. As also mentioned by "ptscho" above, If the hull can be lined off so that the cedar can be used for the garboard and the mahogany used to make use of it for the sheer strake I see a much better boat as a result of using the Honduras for the sheer strake Using the mahogany for the sheer strake as a dinghy that takes a beating by coming in contact will all manner of items such as pilings, bouys and docking floats a bit of added strength there can be a plus!
    Jay
    Last edited by Jay Greer; 06-07-2019 at 12:36 PM.

  9. #9
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    Default Re: Herreshoff dinghy planking material/treatment questions

    You could go with Jersey white cedar (Atlantic white cedar), but you would have to take a drive to S. Jersey. It is as good if not a better planking stock, and the aromatic smell is wonderful!

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    Default Re: Herreshoff dinghy planking material/treatment questions

    Another thought - what do you all think of white oak for the garboards?

    I ask because it's cheaper and more easily available to me. I also know it bends easily and should have no problem taking the twist at the hood ends. I hear steam bending sapele is harder, though I'll defer to anyone who has actually done that before.

  11. #11
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    Default Re: Herreshoff dinghy planking material/treatment questions

    Those who suggested mahogany - if all I could get is kiln dried, do you think I can get it to take the twist at the hood ends after a soak and a steam? Planking thickness is 1/4 inch.

    I'd hate to drop another $100 without a reasonable chance at success.

  12. #12
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    Default Re: Herreshoff dinghy planking material/treatment questions

    No.

  13. #13
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    Default Re: Herreshoff dinghy planking material/treatment questions

    I would just strip plank the garboard right in place on the boat using the material that you have.

    I've done a lot of that. It takes a little longer but if you start with the strip closest to the sheer the grain will follow the sweep of the plank better than by any other method.

    Make it on the boat, take it off and run it through the thickness planer then put it back on, with or without glassing it first.

    OR;

    Make a girder type spiling/template for it on the boat then lay it up to the shape of the girder on the bench, once again following the sweep, then thickness it and apply it to the hull.

    I would glass the inner face, or even both faces, before mounting it. Many would not, but that will help keep it from splitting when bent to shape.

  14. #14
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    Default Re: Herreshoff dinghy planking material/treatment questions

    Have you considered making the garboards of 6mm Sapele plywood? That's what I used on my Coquina and they took the twist just fine.

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    Default Re: Herreshoff dinghy planking material/treatment questions

    Quote Originally Posted by Gib Etheridge View Post
    I would just strip plank the garboard right in place on the boat using the material that you have.

    I've done a lot of that. It takes a little longer but if you start with the strip closest to the sheer the grain will follow the sweep of the plank better than by any other method.

    Make it on the boat, take it off and run it through the thickness planer then put it back on, with or without glassing it first.

    OR;

    Make a girder type spiling/template for it on the boat then lay it up to the shape of the girder on the bench, once again following the sweep, then thickness it and apply it to the hull.

    I would glass the inner face, or even both faces, before mounting it. Many would not, but that will help keep it from splitting when bent to shape.
    Respectfully, how the hell would you laminate up a twisting garboard to shape on the boat, then run that twisted board through a thickness planer?

  16. #16
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    Default Re: Herreshoff dinghy planking material/treatment questions

    It's quite thin Eric, perhaps 3/8 to net 1/4, so it will flatten out in the planer. Also, when it comes off of the forms it flattens back out a lot all by itself. That's worked for me anyway with western red. I've never worked with any of the eastern cedars but I hear that they're tougher and less brittle.

    The trick with 1/4 inch will be bending them back in place without cracking them somewhere even though the grain follows the sweep. They shouldn't be steamed if they're glued, regardless of the type of glue used, so that's out. That's why I suggest glassing, even if only with 4 oz. At net 1/4 I'd be doing that anyway for at least the garboard, including if they are scarfed to follow the sweep.

    The 6 mil ply is a good idea too, although 6 mill meranti is a lot stiffer than one would expect, and green steamed white oak should do nicely, especially with a helper or 2 in order to get it bent and twisted before it cools. Steamed in lay flat tubing would be a big help. I haven't tried that. It may be kind of awkward and slippery to clamp but it would stay hot for as long as it was connected to the stem generator so lots of time. Mahogany is too brittle.

    My preferences would be stripped and glassed then scarfed and glassed then oak then ply in that order. Ply has the advantage over oak of not ever splitting or shrinking but it's stiff. If it passes the boiling test I guess it could be soaked and steamed, but I've never tried that either.

  17. #17
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    Default Re: Herreshoff dinghy planking material/treatment questions

    Thinking about it some more I'm thinking that with that hull being so much shorter than what I do the bends and twists in the garboard would be of a shorter radius than I'm accustomed to. That might result in a bit of snipe in the planer. That could be overcome by running the strips long at one or both ends by the distance equal to the spacing between the feed rollers. That will only work if the stem is of the inner and outer variety, but not if it's rabbeted, in which case it would make more sense to build to a girder type spiling on the bench. That would be easier anyway, and probably faster since several strips can be glued up at the same time as opposed to one at a time on the frame.

    Glue it up following the sweep, thickness it, glass it and hang it. Glassed on both faces I doubt that it would split even if one tried.

    I've also experimented with glassing between layers and found it very effective. That would be 2 layers of 1/8 in this case. The plank could be strip built on the bench thick enough to resaw out 4 veneers netting 1/8 each. That leaves real wood showing on the surface and no need to protect against UV degradation.

  18. #18
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    Default Re: Herreshoff dinghy planking material/treatment questions

    Another thing you might consider, that is done one larger boats that lay up with a garboard that has a lot of twist and shape would be:
    to choose a very thick piece of mahogany or other wood of choice and work the twist by shaping the plank with various hand tools such as a draw knife or adze and shaping planes. Water line curve can also be worked this way.
    Another method is to build a degree indexer on the band saw. This is a pointer that is attached to the table with the arc indicator in a convenient place. It can be made up from plywood and attached to the back of the saw cover so that it reads from the top or side of the saw case. A long handle is then attached to the front or back side of the table. This takes two or three men to saw the plank, one to feed the cut and one read the degree marks that are chalked on the plank and to call out how much to change the table tilt to the guy on the lever. This way gives less labor than carving the plank. Once your band saw is set up in this manner, you have yourself a new and very handy tool!
    It is now your own home built mini Tannenhauser Bandsaw!
    Jay
    Last edited by Jay Greer; 06-14-2019 at 11:51 AM.

  19. #19
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    Default Re: Herreshoff dinghy planking material/treatment questions

    From what little reading I've done on the subject, it seems to me that by the time he designed the Columbia model dinghy, Nat Herreshoff had gotten pretty good at designing boats to be easily produced in his shop. Somehow I can't see the garboards of this dinghy needing such fussy manufacturing methods.
    Last edited by Rob Hazard; 06-14-2019 at 04:35 PM.

  20. #20
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    Default Re: Herreshoff dinghy planking material/treatment questions

    I think you failed to note that the poster here was unable to find stock wide enough to make the garboards of this boat and is seeking a solution to the problem.
    Jay

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    Default Re: Herreshoff dinghy planking material/treatment questions

    No, I got that, Jay.
    My first reply was to warn him away from Eastern White Pine, because I think it is unsuitable. I'm trying to offer alternatives. I suggested 6mm Sapele ply because I think it would do the job perfectly.

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