Glued Lap and Stitch and Glue

[Frank R]

I was reviewing the photos from last summer's WoodenBoat Show (http://www.thewoodenboatshow.com/)

Some of the photos showed the boats being built by particpants during the event. I think the construction method is called glued lap. The pictures showed the pieces of ply wired together with copper wire like a stitch and glue boat.


Some questions come to mind:

• Is glued lap stronger than stitch and glue or is it used primarily for asthetics?
• If it is generally better to leave a slight gap between panels for the epoxy fillets in a S&G build, why do the ply laps touch one another in ply lap? Or do they?

[Peerie Maa]

Better glues make better looking glued lap possible. There will be gaps if you do not brow off the lands, but with good modern glues you can probably brow off, to reduce the "stand off" of the laps.

[Cuyahoga Chuck]

It may have been constuction of a CLC hull built with their patented "Lapstitch" method. With glued lap you need a mold. With Lapstitch you don't. It's just wired together.

[Rich Jones]

I believe they were Chesapeake Light Craft boats. Think it was the lapstitch method. I was there but didn't pay much attention to that exhibit. One method is not any stronger than the other. I prefer glued lap as it best resembles regular lapstrake. And glued lap doesn't depend on lots of messy epoxy fillets.

[JimConlin]

I think that they were CLC 'lapstitch' kits.
In the 'lapstitch method, the strakes are rabbeted and the material at the joint is therefore thinner. I don't think that it's as strong as conventional glued lap where the thickness of the strakes is not reduced at the lap point.

[James McMullen]

I've built over two dozen boats using all three of these methods Glued lap is lighter, uses less goo, requires vastly less amount of time spent sanding to get fair, and is at least 231% more fun to do than stitch and glue. That being said, stitch and glue is probably ultimately stronger, not that either of these construction methods are weak. Either of them are substantially stronger per weight than any form of traditional construction of any kind.

Lapstitch is a sort of in-betweener method. I think it is excellent for smaller craft, though I expect there is an upper limit for what is possible or recommended as it is clearly not quite as strong. Still more than plenty strong enough for rowboat or canoe sized stuff.

[wizbang 13]

I like to leave a gap in S n G panels. But it would not be a problem to have them touch.

[Rich Jones]

To address your final question, the laps in glued lap are in close contact as they overlap just as they are in regular lapstrake. Just a thin layer of epoxy glue and the laps are clamped together until dry. I agree with James about liking glued lap over s&g. A lot less goop and mess and very little sanding. I've built two s&g boats then turned to glued lap and built four of them. No turning back now.
That said, I believe s&g might be easier for a beginner and is easy to produce as a kit boat.

[John Turpin]

My Lapwing project was glued lapstrake. It was a great project, but significantly more difficult than stitch and goo. This building technique is probably not a good match for a beginner.

[Frank R]

Thanks everyone. Another question:

Are all ply lap boats made from straight pieces of ply with only the bottom-most and top-most boards cut to fit?

[James McMullen]

No. Each and every single plank is shaped. The simplification of straight edged planks would force a compromise in the shape of the boat that wouldn't be good.

[Frank R]

No. Each and every single plank is shaped. The simplification of straight edged planks would force a compromise in the shape of the boat that wouldn't be good.

So each plank is drawn and cut out similar to the S&G method?

I just reviewed Ultralight Boatbuilding on Amazon and some Iain Oughtred's designs. At first glance it seems like all laps are straight.

[James McMullen]

The art of lining off is to make those curves sweet to the eye when they are wrapped around the three dimensional hull. Spread out flat, they are anything but straight lines.

[wizbang 13]

Only on some FG boats with fake lines molded in, are the planks straight. And maybe Popeyes barge.

[John Turpin]

Thanks everyone. Another question:

Are all ply lap boats made from straight pieces of ply with only the bottom-most and top-most boards cut to fit?

Here's my third plank. Anything but straight.

[Cuyahoga Chuck]

S&G-
Can produce both hard chine and round bilge hull shapes.
Is probably better at controlling scrap. Once you have the plank shapes a computer program can spot the pieces onto the plywood panels and arrange them to use the fewest sheets of ply possible. That is called a "nesting".
S&G does not require tight fits. Glassing seams with small gaps does not impair the strength of the finished product. As long as one side is the mirror image of the other the hull should be OK.
You don't need a mold until you get into larger hulls or hulls that will carry a lot of HP.

Lap/Glued lap
Hulls that are completly lapstrake inhabit a modest range of hull shapes because the angles between the planks must be within a narrow range.
You need a mold.
The mold needs to be "lined off" i.e. the places where the overlaps occure need to be designated so the plank shapes can be determined.
Every design needs it's own mold.
The under plank at each joint must be planed into a "rolling bevel" along it's upper outer edge so that the mating surfaces are tight enough for gluing/nailing/riviting.
Some hulls will generate a lot of scrap because some of the planks are very curved. A depiction of a complet set of lapstrake planks shows a surprisingly wide variation of shapes needed to form a rounded hull.

[Frank R]

Are traditional lapstrake boards just as curvy?

How are such curvy boards cut from solid wood? Seems mighty wasteful.

[James McMullen]

Traditional lapstrake boards are every bit as curvy. More numerous, narrower strakes makes this somewhat easier, as does a longer length-to-beam ratio for the hull. In smaller boats like whitehalls or peapods it's not too hard to find wide enough full-length planks. Dories and wide-straked faerings do still have a little more problem finding the super-wide planks needed for garboards and broadstrakes these days. Sometimes you'll scarph to length to get the curve. But part of the answer is that many trees are curvy too, and if you select your stock properly, you can often find live-edged planks that are just a perfect match for one strake or another.

Here's Eric (emf)'s new faering built from solid yellow cedar planks:

[Frank R]

Sometimes you'll scarph to length to get the curve.

Do you scarf the boards at an angle?

[Cuyahoga Chuck]

It's possible, if you know how to scarf, to join two or three short pieces of lumber into a roughly curved blank that will give you the curved plank you need. Of course, if you finish it bright it will be rather obvious.

[gibetheridge]

You can also strip build your lapstrake planks if you cannot find long enough or wide enough material. Apply as many strips as will fit, meaning until you will need to overlap the "land" at the end of the previous plank, then remove the beginnings of your plank and clamp it down on the bench and add the remaining strips. It's more work, but not that much.

[Frank R]

Is this strip building like what is done on kayaks, only with thicker wood? Your photos are throwing me off a bit. Is this a different kind of construction? Where do the lapstrakes come in?

[gibetheridge]

The garboard is strip planked first with 1/4" bead and cove, just like the kayaks, then veneered with 2 layers of 1/8" x 3", in other words cold molded. Then the bevel for the lap is planed on the edge and a clinker (lapstrake) plank is in place. Then the bevel to accept the next plank is planed on the edge (it's hard to see at this angle, but you can see the pencil line marking the edge of the 1 1/4" bevel on the left), including the land, which starts right where the pencil line ends. The land (tapered bevel at the end of the plank) is just barely visible at the stem. Next you see the sheer plank starting to be edge glued. Each of the forms has a wedge glued to it's edge which goes from zero at it's lower end to the remaining thickness of the previous plank after beveling at it's top end. The wedge is used to ensure laying up th plank in the correct plane, the plane that it will lie in once it is applied. I used screws to clamp the glued laps rather than making a whole whack of deep throated clamps. Once the screws were removed I filled the holes with epoxied in dowels, I like the clean and minimal look. Also, since this boat will have no frames the inside of each plank is glassed in epoxy and sanded smooth before it is finally attached to the boat. This also incorporates a layer of glass into the lap. Each plank will be (is, at this point) individually glassed in epoxy on it's exterior face as well for the same reason, no frames. It's lighter and cleaner and easier to maintain on the inside as well.

And yes, with thicker sqare edged wood, 5/8" initially, and thickness planed to 1/2" once it is glued up and shaped.

[gibetheridge]

Here's another picture, showing the laps a little better.

[James McMullen]

That seems bizarre, gibetheridge. Are you sure you're not doing it the hard way? I bet you spend as much time Cold-molding your garboards as most glued lap builders spend on planking the rest of the boat. I don't get it.

[BBSebens]

Are traditional lapstrake boards just as curvy?

Speaking purely about the process of making planks, it would seem that solid wood is a bit more forgiving than ply, since it bends in two directions, so you can force it into place if its a bit off. Ply only likes to bend one way, so you plank shape needs to be pretty spot on.

am i right?

[Frank R]

Are there any lap boats made from straight boards?

[WI-Tom]

Are there any lap boats made from straight boards?

Well, not quite real lapstrake, but my brother designed and built a boat that used "lapstrake" construction in a simple flat-bottomed sailing skiff, and it turned out great. He glued up the plywood side panels lapstrake style, all straight cuts, and after the panels were glued up, he assembled the hull screw and glue style--I don't know if there is much advantage to be had building this way, but his boat gets a lot more admirers then mine.

I can't figure out how to attach an image, but here's a link to a photo of the boat:

http://i1022.photobucket.com/albums/...m/IMG_4813.jpg

Tom

[gibetheridge]

That seems bizarre, gibetheridge. Are you sure you're not doing it the hard way? I bet you spend as much time Cold-molding your garboards as most glued lap builders spend on planking the rest of the boat. I don't get it.

I see your experience showing through. I wouldn't say that it's bizarre, just practical in my circumstances.

First, I am using up a lot of 1x3. I could edge join them and get wide enough stock to do the entire hull with glued laps, but there's more to it than that. I don't ever want to have to think about leaks, I want a smooth bottom and I want the added strength and stability that I can get by cold molding the garboard. Remember, there will be no frames other than the floor timbers in this hull. And yes, it takes a lot longer, a LOT longer, having to fair the garboard on the inside once and on the outside 3 times, especially since, in the interest of making the bottom as bulletproof as possible I glassed the inside with 12 oz. cloth and used 6 oz. between the layers and 12 oz. on the outside. That's a lot of long boarding, it's a good thing that I have a lot of time and patience and buckets of elbow grease. I was able to use the belt sander to a certain degree, that saved some work, but it, too, got really heavy sometimes.

As for the strip built clinker planks, they didn't take much longer to do than it would have taken if I had used wider stock and scarfed for length, and I like the way the grain is dead parallel to the upper edge of each plank, no run out at all, which is better also with no frames. Being somewhat obsessive that feels really good to me, as well.

I'm just about to flip it right side up, after applying a teflon powder/epoxy resin layer to the bottom, along with a 1/2" UHMWPE wear shoe to the bottom of the keel and stems. I got the powder from Paul Oman.

I don't think the job could be done to any higher specifications, and since I have the time, the need and the will it suits me perfectly.

I would not recommend that anyone try doing it this way commercially, unless asked to do so. It's very time consuming and uses lots of glass and epoxy, which besides being not much fun to work with is expensive, and heavy, although I don't mind the weight down low like that, this is not a cartopper. Anyway I'm having fun, and even if, in my opinion, this were bizarre, that wouldn't stop me. Fun is what it's all about, that and producing what for me and my needs will be a superior product.

I'll post more pics as things progress, I think you'll like what you see. I had hoped to row it down to PT in September, but it's taking longer to build than I anticipated, which is normal for me, but I should be there next year, and am looking forward to seeing some of your boats "in person". Maybe you'll even take me out for a row/sail?

[James McMullen]

To each cat his own rat. If your boatbuilding pleases and entertains you, then it is a success by any measure! Meet you in Port Townsend next year? I'd be delighted!

[Frank R]

The mold needs to be "lined off" i.e. the places where the overlaps occure need to be designated so the plank shapes can be determined.

Years ago, were lap boats made by a cut and fit method over a mold? Planks laid on a mold and cut to fit and then beveled for the next piece? Is this the purpose of stringers (I think that is the right term) on a mold, to help line them off?

[Thorne]

Well, not quite real lapstrake, but my brother designed and built a boat that used "lapstrake" construction in a simple flat-bottomed sailing skiff, and it turned out great. He glued up the plywood side panels lapstrake style, all straight cuts, and after the panels were glued up, he assembled the hull screw and glue style--I don't know if there is much advantage to be had building this way, but his boat gets a lot more admirers then mine.


Tom

The Whisp is also constructed that way (ply planks glued flat into sides, then bent into shape), but I was unaware of any others. Looks like a nice boat!

[James McMullen]

Years ago, were lap boats made by a cut and fit method over a mold? Planks laid on a mold and cut to fit and then beveled for the next piece? Is this the purpose of stringers (I think that is the right term) on a mold, to help line them off?

Yes, that is one of the ways how you build lapstrake boats. . .and it is probably the best method if you are determined to build a very specific shape as it is nicely controlled. The stringers used for lining off help you get perfect looking plank runs. You only need to do it on one side, and you remove them as you go generally, though there are a few designers such as Tom Hill or Arch Davis who have you go through the extra time and effort to embed them into the forms for every strake on both sides to make it more foolproof for a first-time builder.

Here's a link to a photo album showing a fancy little lapstrake rowboat I built a couple years ago pretty much from start to finish. I bet you'll find some pictures there that will answer some of your questions--much of this is exactly the same whether you are glueing or riveting your laps.

Lining off with battens the same width as the laps:




Patterns laid out on the planking stock for garboard and 1st broads:







Patterning for the next strake using 1/8" doorskin plywood:

[WI-Tom]

The Whisp is also constructed that way (ply planks glued flat into sides, then bent into shape), but I was unaware of any others. Looks like a nice boat!

Thorne,

thanks for posting the photo; I'm e-helpless. I think Redmond's Whisp is where my brother might have gotten the idea for this kind of construction.

Tom

[Rich Jones]

Now, now, James. The Tom Hill method isn't just for first timers. I've used the method four times and love it. I don't embed them into the molds, though. Too much trouble and you can't do those little adjustments that are so necessary to sweet curves. I subtract the thickness of the stringers from the molds and just screw them to the molds. It allows me to see the sweep of the planks and makes clamping much easier without the use of temporary screws which leave holes that would ruin a stain and varnish finish on the boat. I'm a sucker for varnished canoes.
Next boat has to be a small sailboat, though. Looking for the perfect design. Have to put it off for a year or two, as I'm in the process of preparing to retire and move. Have to get my shop set up first. And finish building our retirement home...

[James McMullen]

Richard, I've got nothing too much against Tom Hill's method except for this: Those perma-stringers will only work for a glued-construction boat. They're completely in the way of clenching or riveting for trad. lapstrake. If you're planning to use the epoxy glued lap technique as practice for traditional construction, then you should learn to do it without them. . . . .

[Rich Jones]

Richard, I've got nothing too much against Tom Hill's method except for this: Those perma-stringers will only work for a glued-construction boat. They're completely in the way of clenching or riveting for trad. lapstrake. If you're planning to use the epoxy glued lap technique as practice for traditional construction, then you should learn to do it without them. . . . .

Very true and an excellent point.. By the way, I love that boat of yours. I'm looking for a sailing design in the 12'-14' range. I'll have to take a good hard look at some double-enders.

[Cuyahoga Chuck]

Years ago, were lap boats made by a cut and fit method over a mold? Planks laid on a mold and cut to fit and then beveled for the next piece? Is this the purpose of stringers (I think that is the right term) on a mold, to help line them off?

Lapstrake hasn't changed much in concept since the Vikings invented it 1200 years ago. Covering a complex shape like a boat that's fat in the middle and skinny on th ends with flat boards means there has to be something to act as a mold. On traditional hulls the mold is a framework that may become part of the boat. Glued lap may or may not have interior structure depending on the size. But you have to have something that establishes the shape before you start hacking out planks.
You could get a pretty good understanding of the various processes by reading the how-to books by Walter J. Simmons and by Tom Hill. Simmons is into traditional style and Hill has a particular glued style that would be good for first timers.
To answer another question flat-bottomed dinghies can have lapped sides made from straight planks. But on a round-bottomed hull there is hardly a stright line anywhere.

[WI-Tom]

there has to be something to act as a mold

Actually, weren't many traditional Scandanavian lapstrake boats (in the old days, anyway) built without molds, with sticks propped in between plank and ceiling to define the shape as the build progresses?

Tom

[James McMullen]

That is indeed another way to build certain kinds of lapstrake boats, but it requires a touch and some practice to acquire the eye and skills to do it properly. Unless you really know exactly what you are doing beforehand, you are much more likely to get the boat the shape you want if you use station molds.

[WI-Tom]

James,

have you tried it that way? Seems like I read about it, and how occasionally one of the prop sticks slips free and gives the builder a good clobbering.

Not for me, by the way. Wasn't it John Gardner who said something like, "It's good if it looks good--but a lot depends on who's doing the looking" ? I'm just finishing a strip-planked hull, over molds. It should float.

Tom

[mick allen]

Lapstrake seems to be fairly well established in the 300 AD Nydam Ship. However, thousands of years prior, the hypothesized (I believe from ethnological practice) first lap joint examples would be the use of displacement increasing washstrakes on the upper edge of log boats. Though sewn, the hjortspring boat of 400 BC used lap joints where both planks edges were shaped for lands (a lap joint - but flush planking resulted).


Historically, Nordic overlapping edge-joined boat construction was a shell (ie prior to frame use) approach that did not use moulds but just the successive trimming of the planks to achieve the boat form. I think there is no instance found yet in Viking boats of keel attached frames, implying frame placement was after the shell was formed. I believe just latterly, in Nordic boatbuilding, was a single midships template or mould (not a building form) brought into practice with, in some cases, the subsequent use of multiple templates, rigid forms and the use of framing.


Building complex boat shapes was readily achievable with lapstrake because this process can arguably be thought of as the crudest possible plank/panel building method of all. Large, contact joints could still happen even when both plank edges were left unfinished and barked. And of course, that allowed leeway for shifting and adjustment of plank locations as the build progressed because of the large width of the overlap – a process much more precarious with butt-joined planking or panelling!


(One common example using straight planks was/is the dory. The base was built of straight butted planks – but with a curved edge (so some shaping of the outside edge of the outside plank(s)), the first side plank had a shaped bottom edge to meet the base profile and to establish rocker, and then the rest of the strakes up the sides were all straight, with some possible sheer shaping.)


With regards to the OP:
1) As was seen at the show, that glued lap process was identical to stitch and glue except for the lapping. One often thinks of stitch and glue as mainly having butt joints, so glued laps will more naturally have larger gluing surfaces as well as the double material thickness along the joints adding some more rigidity to the panel edges. The aesthetics of either depend upon the intent of the aesthetic design of the boat. Certainly lapping helps accentuate the panelling shapes and possibly form of the boat, but then the panelling/straking needs to justify their accentuation, heh heh . Sometimes strake shapes are left up to the builder with widely varying results, but many S&G lap boats have strakes predesigned so that big visual errors are minimized. In any case, well designed stitch and glue boats can be equally aesthetic.

2) Generally speaking, for an adhesive to adhere, it must wet both sides of the joint. Using that as an initial guide, panel wiring for either lap or butt joints should be in such a way as to admit the epoxy in the joint. In most lap cases, there will be slight angles or spaces between the panels that allow epoxy wicking, and in butt joint cases, a slight open mitre between forming the butts will do the same. In both cases, an additional filler step is often used to increase the joint size for strength, gap filling and/or filleting for glass bridging.

[Paul Fitzgerald]

Are there any lap boats made from straight boards?

The Banks Dory used straight planks after the first plank, which was also easily shaped once it was fitted as it had a straight upper edge.

[pipefitter]

Are there any lap boats made from straight boards?

Yes. The Simmons Sea Skiff. By straight I mean 'straight edged'. One edge of the plank is straight and the other side is tapered but in a straight line. There is no curve cut into the side planks. The Simmons starts out with the first side planks cut with a curve that helps set the shape of the hull. The rest of the remaining side planks, at least on the low sided versions of the boat, are tapered on one side only. The boat is shell constructed using at most some spreader boards holding the hull fair until the remaining planks are installed. As you can see, the hull is not straight to the eye in any sense of the term.

[erster]

These planks are straight sided even though the planks are fan blade shapes. Cut one and then flip the measurements over and extend them a few inches because of the stem and transom angles and walla create any hull that you want in lapstrake. No special tools are needed and no rocket science CNC machines and for sure no wiring the planks. Scribe your lap distance on corresponding planks and fasten them together using simple sheetrock screws until the epoxy or caulk dries amd just remove them. Spacers across the hull foward is about the only framing, temporary for the build that you need. Go back if you wish and fit side frames if need be. The only place thats framed is the cockpit area. The rest of the boat has three main bulkheads in the cabin area.

Foward I have none except for the rope locker area which is nothing more than a foot or so from the stem. Of course you got to cut the gains at the ends if you want the planks and the ends to have a smoothe finish vertically. Lapstrake hulls can be built weighing less and pretty rigid too. Pipefitter has no framing in his boat, only covering boards which stiffens the structure fore and aft.

[Shawnzoom]

These planks are straight sided even though the planks are fan blade shapes. Cut one and then flip the measurements over and extend them a few inches because of the stem and transom angles and walla create any hull that you want in lapstrake. No special tools are needed and no rocket science CNC machines and for sure no wiring the planks. Scribe your lap distance on corresponding planks and fasten them together using simple sheetrock screws until the epoxy or caulk dries amd just remove them. Spacers across the hull foward is about the only framing, temporary for the build that you need. Go back if you wish and fit side frames if need be. The only place thats framed is the cockpit area. The rest of the boat has three main bulkheads in the cabin area.

Foward I have none except for the rope locker area which is nothing more than a foot or so from the stem. Of course you got to cut the gains at the ends if you want the planks and the ends to have a smoothe finish vertically. Lapstrake hulls can be built weighing less and pretty rigid too. Pipefitter has no framing in his boat, only covering boards which stiffens the structure fore and aft.

Interesting construction technique. I'm surprised this thread would end here. Everyone must know something about this technique that I don't know. Erster, Pipefitter, anyone, can you guys elaborate a little more on the technique you used to build the boats shown in the images.

Erster said: These planks are straight sided even though the planks are fan blade shapes. Cut one and then flip the measurements over and extend them a few inches because of the stem and transom angles and walla create any hull that you want in lapstrake.

Erster also said: Lapstrake hulls can be built weighing less and pretty rigid too. Pipefitter has no framing in his boat, only covering boards which stiffens the structure fore and aft.

I have been doing the background research to design and build my first (I plan to building a few) boat. In fact, I pretty have the design (an 11' skiff with a motor well - think mini Simmons Sea Skiff) for my first boat. I had pretty much settled on S&G but I find the technique you describe, intriguing. I have accumulated quite a few books on boat building and browsed many forums but I have not come across the technique you describe for lapstrake hull construction. One of the books I have is the John Brooks and Ruth Ann Hill book on Glued Lapstrake construction. Great book but not a technique I would use to build my first boat. At least not the one I designed.

Any pointers would be much appreciated