Lapstrake vs Carvel

[SBrookman]

While looking at plans for the next boat, I'm leaning towards lapstrake as it will have to live on a trailer. (and less epoxy than strip, less intensive than cold molding) When looking at plans, can a boat designed as carvel planked be built lapstrake or do I need to limit my search for boats designed to be built lapstrake?
IOW, what design criteria determines the planking method, or it is just the designer's desire?

[rbgarr]

In any case, if you build lapstrake and wish to keep the boat on a trailer, investigate Walt Simmons building methods for lapstrake construction. His designs are meant to be used in that way: http://www.duck-trap.com/dtpress.html

He has designs that incorporate concave lapstrake planking also, i.e., Lincolnville Salmon Wherry.

[TerryLL]

Doing a quick search through the WB design catalogs (30-40-50 Wooden Boats) I found quite a few designs that offer multiple building techniques. For many smallish round bottom CB boats it seems that either lapstrake, carvel, strip, or cold molded will work.

[Ian McColgin]

In general you can switch but the planking schedule will be a little different. Given the difficulty in really getting the planking to look right in lapstrake - you want the changes in size of the plank over it's length to harmonize with the changes in the other planks - you may be aesthetically better off to get a design that tells you how to line the planks for lapstrake. It's not always obvious, even in a simple design.

Lapstrake with dimensional wood is most elegantly rivited. But however fastened, it's not suitable for dry sailing. If you're going to make a trailorable lapstrake, use epoxy sealed epoxied together plywood. It's still a lot less epoxy than strip or cold molded.

Ply makes for great lapstrake since planeing down the upper edge of each plank makes a great site for saturation and bonding. There was a nice article in WB, I think in the last year or so, that shows how to use monofilament and some intelligently made bits of wood and spring clamps to make great planking clamps that pull out when the work is dry and leave no marks to disturb your elegant workmanship. Hopefully someone here will be able to cite it.

G'luck

[Wooden Boat Fittings]

Lapstrake .... however fastened, it's not suitable for dry sailing.

Ian, as usual, has got it right -- exactly. The reason I had to sell Aileen Louisa a few weeks ago was because she was traditional clinker construction (in other words, riveted strakes) and so dried out on her trailer -- in her case, to the point where she's taken a fortnight in the water to take up.

You should not expect to trailer a normal clinker (lapstrake) hull. If your boat is to live on a trailer, then for clinker you should definitely build using full glued construction. (Failing that, you could consider strip-plank, carvel, or hard-chine ply.)

The best-known designer of glued-strake clinker boats is undoubtedly Iain Oughtred, and if it's a clinker hull you're after you should check his designs. Here's an example of his 8' 'Auk' (thanks, Rick) --

Traditional clinker boats are meant to live in the water, not in the air.

Mike

[SBrookman]

Thanks, I pretty much determined it would be glued lapstrake. Was just wondering if I had to limit my search to boats specifically designed for lap. I read Ian's book (Clinker Plywood Boatbuilding Manual) about determining plank widths. The way I read it it seemed like he was showing how to modify existing (non clinker) plans to clinker construction.

[esingleman]

One advantage of glued lapstrake is that the boat will be watertight, and you will need less ribs (my Pooduck has one rib centrally located). Trailering will make it less likely to need repair, but I imagine glued lapstrake would be difficult to repair if it ever became necessary. That wasn't an issue for me as I do not let water sit in her, and I keep up the paint jobs.

You might consider Robert Brooks' book on glued lapstrake boat building if you don't already have it, it is a great resource.

[Keith Wilson]

Almost any boat of moderate size designed for carvel planking can be built with glued-lap plywood. The possible exceptions might be those with really unusual hull shapes (a Seabright skiff, for example, might pose problems) or lots of concavity somewhere. Not impossible, but definitely more difficult. There would be lots of changes in the conversion - thinner planking, first, since plywood has equal strength in both all directions, unlike solid wood. The frames would likely change as well, since frames in a glued-lap boat just give the hull rigidity and provide a convenient place to hang seats and other bits, unlike with carvel planking where they're essential to hold the thing together. Studying lots of other designs of similar size and displacement would be a good way to start thinking about the how to convert.

Ian's right about lining off the planks; because the plank edges show, it's important that it be done right or the boat won't look good.

I really like building glued lapstrake. It's light and strong, it involves less nasty goop than any other modern building method, materials are readily available, and, best of all, it requires less sanding than any other construction method I know of.

[ahp]

Back about 1960 I had a Spartan class boat built and shipped over from England. She was similar to a Folkboat. I had the choice of carvel or lapstrake. I chose carvel, but lapstake would have been slightly less money. There are less steps in the construction.

[ishmael]

I've said this at least twice before. One reason for a lapstrake boat was always that it would take up better in a life boat or recreational boat often dry, than would a carvel. It's also inherently stiff and strong. That's why, traditionally, the lifeboats on ships were often lapstrake. Think about how the wood moves! One quarter inch per foot of width is the rule of thumb... Now how many feet are there in the joint between lapstrake planks?

Just because an old riveted lapstrake hull takes a long time to take up doesn't mean a new construction needs to be that way.

Simmons has, with good success, made trailer sailors with his polysuphide beads between the laps of solid planks. It's doable, and not that hard. The laps come and go a bit between wetting and drying, but the polysuphide gasket works with the movement.

If you want to build glued lap, go for it! Not me, never again.

[neilm]

The latest woodenboat mag has a nice article on the pros and cons of all the planking techniques. Also John Gardner loves to discuss it as well in his books. Basically lapstrake is best for small boats on a trailer because they stay watertight better and carvel is better for non-trailered boats where the planking is thicker than 3/4 inches. But it's hard to deny the beauty of a carvel planked whitehall or peapod...and many where built.

Neil

[ShagRock]

The latest woodenboat mag has a nice article on the pros and cons of all the planking techniques. Also John Gardner loves to discuss it as well in his books. Basically lapstrake is best for small boats on a trailer because they stay watertight better and carvel is better for non-trailered boats where the planking is thicker than 3/4 inches. But it's hard to deny the beauty of a carvel planked whitehall or peapod...and many where built.

I read that article and it provides a decent summary of build methods. However, it didn't mention a method that combines strip and carvel using wooden planks about 1.5" wide (roughly) nailed to steam bend ribs. The planks are not nailed to each other and no chalking is required. The boat can be trailered and takes up in a couple of days even after 6 months out of the water.

[Yeadon]

Lapstrake with dimensional wood is most elegantly rivited. But however fastened, it's not suitable for dry sailing. If you're going to make a trailorable lapstrake, use epoxy sealed epoxied together plywood. It's still a lot less epoxy than strip or cold molded.

G'luck

Glued lap is almost certainly a sure bet if you want to dry sail your boat. I can't blame a fellow for going that direction, especially due to the ease of adding bulkheads and flotation chambers. But from experience, I don't agree with your charactorization of traditional lapstrake.

My peapod is traditional plank on frame lapstrake ... clench nailed between the laps, riveted on the frames. It lives on a trailer next to the house and there is little or no taking up required or overnight soaking to be dealt with. My amateur joinerwork around the centerboard trunk and the keelson was another story, but that's been dealt with.

I do get a touch of weeping along a half dozen clench nails per launch, but within the hour or so that tends to end. I think this is sort of charming.

Other people's boats likely offer differing experiences.

[Dick Wynne]

Lapstrake with dimensional wood is most elegantly rivited. But however fastened, it's not suitable for dry sailing. If you're going to make a trailorable lapstrake, use epoxy sealed epoxied together plywood. It's still a lot less epoxy than strip or cold molded.

It depends. I had my (clinker - aka lapstrake - larch on oak) boat liberally doused with linseed oil throughout the build, as a rot-proofing measure, having read of boats so treated being as new after 100 years. I think it also may 'take up' the planking permanently somehow. Even after a winter ashore, she doesn't leak worth mentioning when launched.

[James McMullen]

Yeadon's right, you know. In my trips with him, he's taken far more water over the bow or the side than he has through the plank seams.

[Thorne]

I also have a similar experience with Yeadon -- my copper-riveted fir over oak Chamberlain dory skiff leaks a bit in the aft area where I messed up some caulking, but otherwise is trailer-sailed in hot climates with no leaks through the lapstrake fir hull.

I used a modern flexible sealant recommended here ( Vulkem116) between the edges of the strakes when restoring the boat, and it handles the changes in moisture and wood size really well.




So if you really want to use (mostly) traditional materials and dry-sail a lapestrake boat, it can be done if you can deal with occasional pumping. But if building with marine ply I'd sure go with Oughtred's glued method -- ply really doesn't like zillions of fastener holes that let in water and cause rot.

[SBrookman]

Thanks all for the advice. I'm thinking after the sharpie gets launched (hopefully sometime soon) I'll order the plans for Gartside's 7' Clinker Pram and do it traditional lapstrake , as best as I can anyway, as a warm up for the next larger project.

[Wooden Boat Fittings]

I had my (clinker - aka lapstrake - larch on oak) boat liberally doused with linseed oil throughout the build...

Interesting you should mention that, Dick. A thorough internal soaking with (raw) linseed was what Eric Hiscock mentioned in "Cruising Under Sail" about fifty years ago as a permanent cure against leaking.

Mike

[ShagRock]

Interesting you should mention that, Dick. A thorough internal soaking with (raw) linseed was what Eric Hiscock mentioned in "Cruising Under Sail" about fifty years ago as a permanent cure against leaking.

The only "permanent" cure I know is to never put the boat in water!