lapstrake canoe construction?

[almeyer]

I'm starting to do a little advance planning on my next project. I've pretty much settled on a Ranger 15 canoe design, the lines and offsets are given in Ted Moores' "Canoecraft". I don't mind working with epoxy, but the idea of fiberglassing both the interior and exterior of the hull is something less than appealing. I'm familar with glued lapstrake construction, it came out well on my Penobscot 14. If I can do a decent job of lining off the planks, I was thinking about taking the Ranger lines and building it glued lap. I haven't thought this completely through yet, but was considering using 4mm occume for the planking, to stiffen up the hull I'd add 1/8" x 2" steam bent frames spaced about every 9 inches (the frames would also add a lot of eye candy to the interior). Granted, this seems a hybrid approach, but I think Marc Barto used a similar construction method on his Melonseed Skiff designs. Any thoughts/suggestions?
Thanks, Al

[RonW]

Do you have a copy of Rushton's 1903 catalog? He built some of his canoes in lapstrake.
You are just replacing the white cedar with occume plywood, which is not as rot resistant, but the plywood won't split like the wood will, and is stronger.
Why not take it to the next level and use ribs 1/4 x 1 or so,along with rivets, and copper clenched nails in the laps and forget the epoxy all together.

[almeyer]

I've ordered a copy of "Building Lapstrake Canoes" (I think by Walt Simmons??) from Duck Trap, which I believe is based on real wood construction. The real wood is certainly more appealing from an aestetic standpoint, but my limited understanding is that the bevels on laps have to be much more exact if the boat isn't going to leak. Glued ply is a little forgiving in that respect. I've also heard that real wood likes to shrink and swell, an important consideration as the boat will be stored out of the water and spend some time zipping along the highway on it's way to the bayou. Thanks for the suggestion though, I'll give it some more thought.
Al

[JimConlin]

Tom Hill's book "Ultralight Boatbuilding" describes building glued lapstrake canoes of okoume ply. There's a companion video and our hosts offer them. I recommend them.

With okoume's low rot resistance, I'd be concerned that applied ribs would create rot pockets unless the ribs were jogged to the planking or filled behind. For canoes which have thwarts, 6mm okoume is strong enough with no full ribs, just limited bottom stiffening.

[Bob Smalser]

Canoes were strip-built built successfully for generations, covered with painted canvas and varnished on the insides.

Still the best-looking method by far, IMO....no toxic goo handling, unpleasant plywood handling and faster construction than either lapstrake or fabric-goo. I've seen such canvas go many decades with only the occasional repaint.

Look at WB 121, Nov 94...the Grand Laker article.

[ 06-07-2005, 09:40 AM: Message edited by: Bob Smalser ]

[RonW]

No Al, you are reading me wrong.
I am saying yes ,use plywood instead of solid planking. The plywood is stronger, won't shrink and swell like solid wood, or split along the grain and is more stable.
I was suggesting just taking it to the next level with real working ribs and rivets instead of eye candy ribs.
The canoe will be more flexible and comfortable.
Do use plywood, you can easily bevel the edges, and in between the ribs you use copper clenched nails to draw the laps tight.
You are just afraid it will leak without the goo.
You will be surprised at how easy it is to make water tight laps. Particularly on a little canoe.

[Keith Wilson]

Most glued lapstrake canoes don't have frames. Plywood doesn't need reinforcing across the grain like solid wood planking, and the gunwales, seats, and thwarts stiffen the hull enough. If it were my boat I'd leave them out - lots of work, no functional benefit, difficult to finish and refinish, and many excellent places for rot to start. Gluing the laps essentially forms a double-thickness stringer running the length of the boat, and makes a functionally superior joint in every respect.

[ 06-07-2005, 10:24 AM: Message edited by: Keith Wilson ]

[Bruce Taylor]

Still the best-looking method by far, IMOOh, the old lapstrake canoes were pretty fine, in their day.

http://freepages.genealogy.rootsweb.com/~fassitt/canoe_mirror/museum_vesper.jpg

Here's a Walter Simmons interpretation of Rushton's Vesper:

http://www.mainecoastboats.com/17canoe3.jpg

Cedar-canvas proved more practical, in the end (durable, easy to build with semi-skilled factory workers...even Rushton resorted to it, later in his career), but the beauty & workmanship of the Victorian lapstrake canoes has never been surpassed, I think.

Some of the lap/ply boats are quite pretty, too...especially the decked, double-paddled sailing canoes like Oughtred's Macgregor, and Bill Clements's updated Rushtons.

[ 06-07-2005, 10:25 AM: Message edited by: Bruce Taylor ]

[Cuyahoga Chuck]

I'm kind of confused by the construction details mentioned.
On any lapstrake the knuckles form hard angles that would seem to defy coverage with 'glass/epoxy without a tremendous amount of filleting. Why go to all the trouble?
Tom Hill built glued lap canoes that seemed to be structually sufficient without any 'glass or ribbing. His boats were clean inside and out. No traps for water or debris on the inside. And weights that are better than most other wooden hulled canoes. Making the boat carry a blanket of 'glass/epoxy would, certainly, give away the weight benefits that glued lap is noted for.
Installing ribbing that is only 1/8" thick seems to be a soley cosmetic add-on. I can't conceive of it adding any structural integrity.
Ribbing in a nailed lap construction is necessary to tie the planking together. But because lapped hulls had a lot of integrity the ribbing was usually very small. In the range of 3/8" x 5/8". A sufficiently wide epoxy joint in glued plywood should be more than adequate by itself.
If anyone has knowledge of why Tom Hill's approach won't work I'd certainly like to hear it.
Charlie

[Bruce Taylor]

Chuck, Hill does put a layer of glass on the garboards on his plywood canoes.

But I don't think anyone would recommend sheathing an entire lap/ply hull.

I agree that frames on a lap/ply canoe are mainly a stylistic affectation.

[Andrew]

Tom Hill's canoes have a wide garboard strake which he ususlly covers in glass/epoxy for abrasion resistance. No ribs, though his larger designs have a doubling of ply inside the canoe along the keel for added strength.

[J. Labaree]

I built a traditional construction lapstrake decked canoe 20 years ago when I was in college - cedar planks on sawn frames (apple). It was my second lapstrake boat - the 12' Rob Roy from Mystic. It wasn't perfect, by any means, but it really did not leak that much. More attention to the bevels at the laps and at the stems than I gave would create a boat that hardly leaks, if at all. I'm not pooh-poohing Tom Hill's method, but if it's traditional that you want, don't be afraid of it. Just be aware you'll need to be careful and take it slow (a concept lost on me at the time).

[Dan Lindberg]

Checkout this string over on the WCHA BB.

They are building an all wood lap and rib canoe.

Dan

http://forums.wcha.org/showthread.php?t=387&page=1

[Brian Palmer]

I built Tom Hill's 11 1/2 foot canoe as he describes in the book. It is a lot smaller than a 15 ft canoe, but it is plenty stiff without any frames at all. Even much larger boats that use glued lap (like the Caledonia Yawl) are relatively free of frames compared to others of the same size built with traditional methods.

I do not see the need to add frames; it would only complicate the interior and add weight to what is already a very good construction method.

Our canoe does have a double layer of plywood on the floor in the center 2 1/2 ft of the boat, but this is almost as much to provide a flat spot for your butt over the keel as it is to provide strength.

-- Brian

[almeyer]

Thanks for all the replies, you've certainly given me a lot to think about. Fortunately, I've still got time to hash this out, I probably won't start building until Thanksgiving when the water temperature starts getting too cool to safely sail the Penobscot.
I've borrowed and read several times a copy of Tom Hill's book, and almost wore out a copy of Iain Oughtred's book on glued ply. The only real difference between these methods and the one I used on the Penobscot is that on the Penobscot, the stringers/ribbands are permanently installed on the boat. Other than a six-hour canoe, it was my first real attempt at boatbuilding. Others who have seen it say that it came out pretty decent.
The woodstrip and fiberglass-sheathed canoes shown in Ted Moores book are certainly nice (my father built one 20 years ago - it belongs in the living room, not the garage), but I'm trying to get away from fiberglass.
I've also noticed some very nice canvas covered on the web, I briefly looked at a book on this method of construction. No offense meant to Bob, but frankly this method of construction looks beyond my level of wood-butchering ability.
Keith is correct, I haven't seen any glued ply canoes with frames. My original thought was that a 15-foot glued ply canoe should probably use 6mm (1/4") ply for planking. To cut down the weight, I thought about reducing the thickness to 4mm and adding the frames to stiffen up the hull. That may be faulty logic on my part.
Ron, thanks for clarifying, and you're exactly right - I'm concerned about leaking without the goo. Just not confident about my ability yet. On the Penobscot, I used a belt and suspenders approach - goo on the laps and planks screwed into the stringers. It was per directions, and probably overkill, but one or the other probably would have done the job.
I hadn't thought about the possibility of rot forming at the junction of the planking and the frames. The boat will be stored indoors (garage) out of the weather, but it's something I hadn't considered.
Thanks for all the comments, I've definately got some more thinking to do before I start construction. Sorta maddening but also fun!
Al

[Andrew]

Tom Hills 15ft canoe is 4mm with no frames. Be carefull, those strakes are floppy and weak until you get them on the boat.