Sunday, May 13, 2012

Minor Obstacle

Okay, so things are going pretty well - I'm ready to fit and install the chines. Unfortunately, the chines are not ready...

The plans spec the chines at 20mm x 70mm x 5,790mm (that's 3/4" x 2-3/4" x 19'). The chines fit flat on the outside of the hull bottom so they have to bend in that dimension. They also conform to the rocker in the bottom so they have to bend in that dimension...

I'm using Monterrey Pine and it is not going to bend in those two directions... not without some serious convincing. Steaming the wood seems the logical means of "serious convincing" but steaming wood is one of those black-box mysteries I've always considered to be beyond my skills. However, I am thinking about it...

Several questions come to mind:

1. What do I use to steam 19' long pieces of wood?
2. Can I fit the wood and then re-steam it once I'm happy with the fit? (I don't think I'll be able to remove them if I let them sit long enough to dry to shape.)
3. How do I glue steamed wood in place? Can I glue wet wood after re-steaming?

Okay, I can answer the first question. It is the other two that are troubling me.

Any suggestions?


  1. Bob,
    Once you do it, you will not be intimidated again.
    You can use a length of black ABS pipe as your steam box, steam can come from any source. Let some of the steam escape from the opposite end. It will take awhile, half hour maybe? I don't know the characteristics of Monterrey Pine.

    You can't glue the wet wood. But you can pre-bend to the approximate shape - it doesn't have to be set in place, necessarily. For pre-bending you want to exaggerate the bend a little to allow for the wood's natural memory.

    The wood changes cell structure when it's heated, so you don't want to do it more than once per piece. Try some scrap first to get the feel for it. Unless your hands are like shoe leather, wear gloves.

    The hot wood will stay supple for awhile - if you were riveting frames, you would have to move fast, but for two chine pieces you'll have plenty of time.

    One last word: epoxy melts over 120 degrees and stays soft forever, so no scarphs allowed.

    1. Michael,

      Thanks for the comments. Very helpful: You've saved me some trouble - I knew epoxy softened when hot (didn't know the melting point) but didn't know it doesn't reset. Obviously (well, it should be), the chines are scarfed for the length. I'll mill new pieces to laminate the chines as Rob suggested.

      I'll have to get over my concerns with steaming on another project.

      Thanks again.


  2. For what it's worth Bob, I'd recommend not using steam even though those twists and bends are pretty severe. With my Navigator I found it possible just to cut through horizontally aft where the bends were both up and in - it's like having a lamination part of the length of the member. Epoxy in the saw cut, then bend and it sets bent.

    Some people use two thinner pieces all along (ie 2 laminations that add up to 2 3/4 x 3/4)...and this is the easiest way. You'll be surprised how much easier it is to clamp two laminations at one end and let them form a complex curve together as you bring them around to the other end.

    I'd do it dry with just clamps first, thinking through each clamping issue, then when you know how you'll do it, do it again but with epoxy. If you are still worried, maybe clamp it all up except for the twists at the stem, even glue the aft formers first, then bring all your attention, clamps and ratchet straps to the most difficult bits at the bow. And remember, you'll spend more time planning the bends than actually doing them, and then you'll only have to deal with it once!

    It is useful to look for a nice even line around the hull and believe your eye- even if that means taking a bit out of a bulkhead notch here, and adding a shim is easy to create a nasty 'hardspot' in your planking if a stringer has been stressed unduly at a former.

    Lastly, I'd like to say that there are so many strong curves on a Pathfinder and they all depend on getting the stringers nice. So if you can get some space on each side to really look hard at your curves before you glue the stringers it may make a pretty boat more easy to achieve. And they can be SO pretty.

    Hope that is helpful in some way.

    1. Thanks Rob,

      Your comments/suggestions are very helpful. Somewhere in my memory I recall reading about using two thin pieces to laminate the chines in place. Thanks for the reminder. I can mill the two 3/4" pieces I have now to laminate one chine and mill two new pieces for the other one.

      I feel better about this approach.

      Thanks again.