View Full Version : Plywood Lapstrake
04-02-2001, 07:55 AM
I have an idea for a boat in the egg forming stage. This is a boat for myself. About 26'-30' LOA 6'1/2 - 7'1/2 beam. The hull will
be much like a Sea Bright Skiff. The shape dosen't lend itself to plywood developement.
I could strip build, but would like to try lapstrake (less glass work). Is 30' to long for ply-lapstrake?
04-02-2001, 08:49 AM
I don't see why not. You are talking glued lapstrake?
04-02-2001, 08:51 AM
Yes, glued lapstrake.
04-02-2001, 09:08 AM
Probably not. There are a number of successful 20' - 25' plywood lapstrake designs. Lots more if you consider plywood multi-chine designs, basically lapstrake without the overlap. It will require a lot of scarfs. Most likely it will be easiest to scarf the planks on the mould. You will also want to install some permanent frames. Take a look at Sam Devlin's book for ideas on how to build larger plywood boats.
[This message has been edited by Don Maurer (edited 04-02-2001).]
04-02-2001, 09:12 AM
Iain Oughtred has designs for glued lapstrake
to 20ft or so. In a coversation with Tom Hill he expressed the opinion that he saw no reason why 30ft and longer boats could not be built glued lapstrake (appropriately using thicker plywood). I would liberaly treat with CPES, especially the end grain.
04-02-2001, 09:27 AM
Yes to frames, but probably considerably less than conventional methods. I would consult an NA. You would need about three scarfs per plank but you'd soon get good at making them. You might also realize an economy in the use of the ply if scarfed sections were angled to each other to follow the curve of the final plank.
04-02-2001, 12:10 PM
If I decide on glued lapstrake the planks would be designed to be cut on a CNC router, scarfs included.
04-02-2001, 08:38 PM
Oh, yeah like we all have one of those at home...
04-02-2001, 09:16 PM
Come on Paul, this is an idea in the back of my head. I carry it with me all day and bring it out when I can. When I can't build I day dream. I think this would work. Today I found a 28' Pilot Schooner, by
Reuel Parker. Plywood lapstrake with 3500# ballast. So give me your opinion. The router work can be contracted.
04-03-2001, 08:32 AM
Gary, take a look at Sam Devlin's stuff. It'll give you more feel for plywood designs, but not especially lapstrake. Also check with Dave Gerr and look at his book "The Nature of Boats" which mentions the Sea Bright skiffs.
04-03-2001, 10:00 AM
Sea Brights also were featured in the MotorBoating Ideal Series. I think most were by the Atkins. You may wish to look through their design catalog (which is a good idea anyway). Prices for plans are very reasonable.
04-03-2001, 10:17 AM
Here's another instance where the NA ought to be consulted as to scantlings, plank lap dimensions & who knows what else. At some LOA would commercially manufactured plywood be available in a sufficient thickness. You might have to laminate the plywood to the required thickness as well as scarf to length. Is there a point of diminishing returns with the labor involved?
04-03-2001, 11:31 AM
I would echo your advice. Devlin's Boat Building is a great book for working with sheet plywood. And Dave Gerr has two excellent books, The Nature of Boats, and The Elements of Boat Strength. My idea for a Sea Bright is from Gerr.
I have looked at the Atkins Sea Brights. I also have rough drawings for my own Sea Bright done in plywood stich an glue. This could be the best I can do. I am comfortable
with S&G construction. Glued lapstrake would give me fairer lines and less glass work.
I will get a NA involved if I go beyond the dreaming stage. I hope that some of the forumites here can help define that point of diminishing return.
Thank You for your input. I would like to hear others.
04-06-2001, 07:17 AM
I'm also in the dreaming stage, and the biggest boat I've built is 12 ft. However, it seems to me that when you get to 26 to 30 ft, the interior (including bulkheads, frames, etc) starts to become much more important and involved than the planking. With a small boat, once the planking is done it's about finished. At 30', when the planking's done you're not even halfway through.
Most stitch and glue, and almost all the glued lapstrake designs I've looked at have been smaller than that. I'd be nervous building a boat (to which I'll trust my life and the lives of my friends and family, and possibly even my dog and lunch and some good red wine) just because a designer says he sees no reason why it wouldn't work at that length.
My inexperienced, often wrong, but never humble opinion is to build a 30 ft boat designed to be a 30 ft boat, preferably one that's been built and tested and survived, rather than try and stretch small boat techniques to something larger. Plenty of strong, sound, tested 30 ft boats have been built strip planked, cold molded, layered plywood, POF, etc, etc, and the time (perhaps) saved in planking glued lapstrake would probably only make a difference of a few weeks in the scheme of things.
As one designer told me, when you increase length, the time and effort and materials and cost and stress and everything else increases geometrically (at least). And therefore the type of planking becomes less important.
04-06-2001, 08:12 PM
Not only that, Tom, but clinker construction on anything other than an open boat just doesn't seem to look right, somehow.
Carvel does, though, and once painted, strip-planking is pretty-well indistinguishable from it.
04-08-2001, 02:39 PM
I have recently launched a 6.4 metre (21 foot )lapstrake gaff rigger. It's an exceptionally strong construction method. Using 7 mm ply epoxy glued over 20 mm stringers makes a very stiff boat.
And it looks great,too !!
04-09-2001, 08:31 AM
It's amazing, when I think out loud on this forum how fast an idea evolves. I have for now dropped plans for glued lapstrake.
The reading of another thread has me thinking again of strip planking. This area has an abundance of eastern larch (tamarack).
I'm going today to pick up some samples to do some tests. It might be that with miracle in a can (CPES) and epoxy to stabilize
it this wood might make good planking. I will let you in on the results when I have them.
Greg P thanks for your input. We all want to see pictures.
Alan D. Hyde
04-09-2001, 03:46 PM
Chris-Craft Sea Skiffs were basically glued (5200) and riveted marine plywood lapstrake vessels. They were built well into the thirty-foot range, and perhaps into the low forties. The curator of the Chris-Craft collection at the Mariners' Museum would know for sure.
The ribs (sorry, Cleek, steam-bent frames) did tend to crack at the turn of the bilge, but these were (and are, in some cases) still strong, seaworthy, boats.
The labor required to build them was not, for the most part, highly-skilled.
I will reiterate what Alan said, Chris Craft built using plywood lapstrake up to at least 37'. They were solid good quality boats. When you refer to a "Sea Bright Skiff" you are referring to boxed garboard or rolled garboard construction? In the first half of the 1900's all the pound boats that made their living by running off the beaches and through the surf of the Jersey shore to tend the pound nets set in the Atlantic were of lapstrakeconstruction with either boxed garboard or rolled garboard 'keels'. The pound boats averaged about 30'in length, but were built up to 42'. That construction was also common for pleasure boats up to WWII. Your idea is a very realistic one. I will add that boxed or rolled garboard construction is a fair bit more complicated than straight lapstrake construction so unless you have a real need for its functional advantages, or are a real fan of the design for whatever reason (like I am)then you might want to think about the type of bottom you want to build.
04-11-2001, 11:06 AM
At Skiff Craft we've built glued (5200) plywood lapstrake boats up to 35', The hulls are like Chris Craft Sea Skiffs but with fewer (wider) planks. www.skiffcraft.com (http://www.skiffcraft.com)
04-11-2001, 12:19 PM
Ned, can you tell me more about your Boxed and Rolled Garboard construction, please? Or drawings perhaps, if you have any? I'm not familiar with either term.
04-11-2001, 12:27 PM
You have confirmed what I know about the Sea Bright Skiff. The boxed garboard is the reason I choose this style. But, is it your opinion that using plywood for planks would work. My concern is, to get the longitudinal strength the planks would be so thick that the finished weight would be to great.
Great boats, but very different than a Sea Bright. What thickness are the planks? Do you sheath the outside of the hull?
Plywood would work just fine for what you have in mind. Half the secret of traditional lapstrake construction is to let it stay flexable. When I was growing up, our family had a 30' Ulrichsen skiff (typical N.J. lapstrake construction) when out in a chop, you could lift a hatch and actually see the bottom flexing up and down a bit. Remember that you have all those steam bent ribs (yes, we call them ribs on the Jersy shore)adding strength. Typically there are also some quite hefty stringers inside that add longitudinal stiffness.
As I have said, boxed garboard keels and rolled garboard keels are kind of a complicated construction method, so I will probably do a bad job at describing but I'll try. (I will try to post some pics. and drawings later tonight.) The two methods look very much alike when finished, its kind of two ways to the same result.
I will try, the easiest way I can think of, to describe the bottom shape of a Sea Bright skiff or pounded boat. (The constuction is actually quite different). If you think of what a banks dory with only the garboard on would look like. Now cut the tombstone transom off at the top of the garboard and stick a traditionally shaped soft chine transom in its place. When the second stake (the broad) is put on, it will run from the stem where it is vertical to amidships where it will start to roll horizontally, and on to the transom where it will be laying flat (horizontal)and be fastened to the underside of the transom. The rest of the hull is planked as you would a typical lapstrake hull. It makes for a pretty interesting looking bottom when finished. The two major advantages being 1) when beached, they remain upright with the prop protected(because the shaft runs out through the small deadwood at the garboards, and 2) it allows for a very flat engine angle installation. It is also an easy hull shape to push through the water at moderate speeds.
<a href=http://albums.photopoint.com/j/View?u=1504427&a=11355807&p=46423206>See my photo, pound boat 002 at PhotoPoint</a>
I obviously have forgotten how to post photos and have lost my 'crib sheets'. As soon as I can find the directions i'll put some pic's here.
[This message has been edited by nedL (edited 04-13-2001).]
[This message has been edited by nedL (edited 05-31-2001).]
04-13-2001, 07:03 PM
The hull planking is 1/2 MDO fir ply... currently using pressure treated XL from Greenwood Forest Product
This is was the last of the true "pound boats" on the Jersey shore, reduced to an advertising sign in front of a boat yard in Sea Bright ~1976. She was 30'long and built to go off the beach throught the surf every day. (Detail is of the rolled garboard keel.)
A small(~16')inboard Seabright skiff,~1975.
A 17' Joralemon skiff built in Monmouth Beach in the first part of the 1900's. You can see how a "rolled garboard keel" is built. She was originally built as an inboard.
Construction of rolled & Boxed garboard construction - courtesy of "The Sea Bright Skiff and Other Shore Boats" by Peter Guthorn
How would you like to keep that 36 footer on the beach every night & take her out throught the surf every day to earn a living! I'd love to spend an afternoon on board!!
[This message has been edited by nedL (edited 04-16-2001).]
24' Hankins skiff with a boxed garboard keel, built by Charles Hankins in Lavallette, N.J. 1972 - Power 4 cyl. Lehman Ford diesel.
[This message has been edited by nedL (edited 04-16-2001).]
04-17-2001, 11:42 AM
Great pictures Ned. I would love to have a ride on that 36 footer.
Thanks to all for your help.
The dream goes on.
Alan D. Hyde
04-19-2001, 02:39 PM
I'd encourage those who haven't done so to have a look at the Skiff Craft site mentioned above by Bill Berrisford.
It is gratifying that someone continues to do a good job building a well-designed wooden boat of this type, while managing to make money at it.
Whenever quality wooden boats can be commercially successful, we ought to be among the first to applaud.
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