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Thread: batten seam planking

  1. #1
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    So I finally have a place large enough to build a boat and I've collected all of these runabout plans over the last year or so. Some are designed to be built cold molded (which I understand) but some specify "batten seam planking" which is apparently much harder but more authentic. Could anyone out there define batten seam planking for me? And does anyone know if it's worth the trouble?

    Thanks
    Adam

  2. #2
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    Moose,

    Batten seam is certainly more authentic, but requires a lot more ongoing maintenance than cold molded.

    essentially - batten seem in the case of a runabout would have to of the planks butted tightly against each other, with a batten over the seam on the inside. I think there would be some bedding compound there (not 100% sure)

    The bottoms of the old runabouts were 2 layers of planking with a canvas layer in between. The modern restoration of the bottoms uses 3M5200 as the bedding layer.

    You should get the Dannenberg Runabout restoration books. They describle much of the old style of construction.

    In the end - if you want a new boat built the old way, go batten seam.. But there will likely be much more ongoing maintenance that cold molded construction.

    Hope this makes sense,
    Bob

    ps. I'm building a cold molded mahogany runabout

    My Current project is at:
    http://www.imagestation.com/album/?id=4291051329

  3. #3
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    Batten seam means each plank seam has a smaller piece backing it up for the full length of the boat, and the planks are fastened not only to the frames but also the battens. All Chris Craft boats were built that way. My instructor at the WBS said it is not as durable as carvel planking, as the area between the batten and the plank is prone to rot. Carvel planking, in comparison, would use thicker planks that would not need the reinforcement of the batten behind the seams.

  4. #4
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    I do not have any experience with building a batten seam boat, but I am surprised by the idea that it would be "much harder" than cold molded. Yes you have to fair the battens carefully in batten seam construction, but cold molding also has its challenges.

    That said, I certainly agree that from a structural and longevity perspective cold molding is far and away better than batten seam.

    As I understand it, batten seam was developed as a way to build a boat with thinner planks that would be viable with carvel construction. Lapstrake planking is another route to a similar end...

  5. #5
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    I built the chamberlain gunning dory "Leeward" to Gardiner's directions for plywood seam batten and found it easy and durable. In this case epoxy was used as well.

    Plywood is a super material for runabouts. In the seam batten method, the battens are installed over the mold stations and let into any frames. The can be scarfed up to full length and are commonly of rectangular section. I think it well to bevel at least the top edged (both if the boat's ever stored upside down) such that the inner exposed face is smaller. This will prevent water and dirt from collecting atop the batten.

    The battens are installed such that the outside center of the batten is the seam line. Mark this in advance with a chaulk line or scribe it in situ with your adjustable square or spiling marker.

    If you tap a nice steel rod to your plane's side that can reach the next batten, that will guide the plane to the correct bevel. Do a little on each batten working up and down and around the boat as the first cuts with the guide on an unshaped batten will be at too flat an angle. But by working around with a good hand plane, you'll get out the bevels fast and accurate.

    I hit on an incredibly easy way to spile out the planks from here. If you must, remark the battens' centerlines to ensure a fair curve. Then lay some tape on the battens against the seam line, folded and creased such that more of the sticky side is exposed than hitting the wood and the free (sticky side up) edge is at the marked batten centerline. Lay down a dumby plank you've taped up from mildly stiff drawing board or whatever, press a bit, and pull it up. the tape should come up with the cardboard showing the exact shape of the inside face of the plank. Easy to cut out and then transfer to the planking stock.

    With light plywood on seam battens with epoxy, there is no need to bevel the plank edges. Just fill in with thickened epoxy and when you fair the hull slightly relieve the corner to make final outside glassing easier and neater.

    G'luck

  6. #6
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    I think this has been pretty well covered above, but as a small point, not all Chris Crafts are built batten seamed. My '57 Cavalier runabout wasn't, and I think a lot of the larger Connies and Commanders aren't either, being double planked.
    Lew

    [QUOTE]Originally posted by David McCollum:
    [QB]Batten seam means each plank seam has a smaller piece backing it up for the full length of the boat, and the planks are fastened not only to the frames but also the battens. All Chris Craft boats were built that way.

  7. #7
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    So all things considered, there's no real reason that a design meant for batten seam planking couldn't be built cold-molded is there?

  8. #8
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    Look at the design. Most seam batten shapes have a flat bottom or knuckle between garboard and strake or hard chine or something such. Cold molded is most suited for a round bottom and /or soft chine shape.

    You can do most anything but not everything is best in a particular application.

  9. #9
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    And does anyone know if it's worth the trouble?
    Batten seam was favoured for runabouts in cold climates. (The other favourite method was lapstrake.) I think this is because the boat is out of the water for so long, seams on a carvel planked boat can open REALLY wide. Batten seam provides a backstop that can be more readily caulked.

  10. #10
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    Batten-seam construction also increases the longitudinal strength of the hull, which was a problem in the old high-L/B dunabout and racing hulls.

  11. #11
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    I think that most batten-seem designs are very sitable for cold-molding. A lot of them are not suitable for plywood, because there is usually a lot of twist, making compound curves. You probably won't have to change the scantlings at all, leave the battens where they are on the plans, and cold mold on top of them, with the last layer for and aft, varnished. It will look exactly like the original seam-batten boat, and be much more durable.

  12. #12
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    As implicit above, there are two sorts of seam batten hulls: Those developed from what might otherwise be lapstrake and/or hard chined and/or dory shapes vs. those with narrower planks that might otherwise have been round bottomed/soft chined clinker. The latter are mostly suitable for cold molding, the former usually not.

    Have fun.

  13. #13
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    Most batten-seam runnabout plans that I've seen are hard-chined, but with too much twist in the sides and bottom to be planked with plywood, therefore, cold-molding would be a good substitute for seam-batten planking. (perhaps the best substitute?)

  14. #14

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    I have a 1964 36 foot chris craft, essentially a constellation hull. It is bottom planked with strips of approximately 3 foot wide fir ply, 5/8" thick, then covered with 5/8" philipine mahogany plank. The seams on the plank are cottoned lightly then caulked.

    At the hard chine, (all of the CC of this era are hard chined) the planking becomes 5/8" mahogany, battened behind with a mahogany batten approximately 3" wide by 1/2" thick. The seams above the waterline are filled with a harder putty. All the frames above the chine are notched to fit the batten, and the plank is screwed with bronze to both the frame and the batten. This method was used on all Constellation models to 57 feet as far as I know.

    I had a 1932 Gidley launch that was batten throughout, using long leaf yellow pine plank and white oak battens.

    Batten construction is extremely strong, and still relatively light compared to double plank, or closer framing. I suspect that on high speed boats that may be pounding some, that batten was used to keep them dry. Keep in mind that at the seams, it means that the surface is over an inch thick on CC on topside planks

    The biggest advantage I can think of tho, is the how stable the topsides stay as a result. My boat has artificial carvelling seams, which are filled with putty. At 40 years old, the hull is extremely fair, and the original putty in most places is quite good. When I painted the boat this last spring we replaced approximately 35% of the putty between the topside seams, but the rest was still very stable.

    As for the rot question, I can only tell you that the Gidley launch was 50 plus years old at the time, and my Chris is 41, and there is no appreciable rot, except at the occasional plank butt.



    [ 12-27-2005, 03:13 PM: Message edited by: Peter Malcolm Jardine ]

  15. #15
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    Below is a snap of a 1956 54 foot Commander. Wonderfully stable, she has been absolutely rock solid for the 6 years I've known her. Doesn't crack out, doesn't move, doesn't leak, has a fancy Sterling paint job that stays put and wears on and on. Incredibly spacious too....
    She belongs to our friends Esther and Bill (hence, "Esther William's"). No battens on the bottom, I'm sure, but I can't vouch for the areas above the chines, will need to look. Last time I was "down there" adjusting the packing glands, I could have sworn I saw no battens anywhere, but I could be embarrassingly wrong.
    This boat has turned my head around regarding the basic durability of Chris Craft's construction technique and long term durability. They may have been the basic production boats of the pre fiberglass era, but they had a great deal of "experience" built in over the years. Light? certainly. Stable? Very!
    However, I do know for a fact that my old Cavalier had no battens so will stand by my original statement; not ALL Chris Craft are batten seam [img]smile.gif[/img]

    Esther William's (Rita in background)



    [QUOTE]Originally posted by Peter Malcolm Jardine:
    This method was used on all Constellation models to 57 feet as far as I know. .......... The biggest advantage I can think of tho, is the how stable the topsides stay as a result.

  16. #16

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    Cavaliers were plywood construction or simplified construction in comparison to other series in the CC line. They were the budget CC, less money than the others.

  17. #17
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    No one would know better than the man who owned one just how "budget" they were, (and I do believe they were always plywood, just some finished differently than others) but still...... [img]tongue.gif[/img]
    Lew

    Originally posted by Peter Malcolm Jardine:
    Cavaliers were plywood construction or simplified construction in comparison to other series in the CC line. They were the budget CC, less money than the others.

  18. #18
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    Take a look at www.vandamwoodcraft.com if you haven't already. This is a great website for those interested in cold molding traditional looking runabouts. There is a wealth of details in their photo albums on both the construction method and design.

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