Planking methods and materials

Hello everybody

Several months ago I've decided to build small classic wooden boat. I haven't known what troubles are waiting for me. I live in Poland, country with no yachting tradition, and no great history in wooden boatbuilding. Most of my problems are gone today, but one of the most important still exists. I’m talking about the core material for my boat – planking wood. I’m not going to explain you complicated situation on Polish timber market, but belive me it’s really dark for small boatbuilder.

Ok, after this preface lets state my problem precisely.
a) I’m going to build small sailing dinghy about 12’ length, and I was thinking about 5/16’’ lapstrake planking.
b) After lofting on the floor I used some 3D designing software and it turned out that some boards should be about 10’’ wide to make 4 ‘’ planks. This width is almost unobtainable quartersawn. To obain such wide board I have to find 25 wide log, then convert it to boards. No lumber mill is going to do it. They are milling construction lumber and stopping production for 2 hours to make convert one log is out of question (they can do it but for very very high price, which means 6-10 times more then standard price). Of course, still remains problem of finding appropriate log…

Seeking for solution for this problem I have started to consider other planking methods. I’m thinking seriously of two of them, and here come my questions.
1) Diagonal Ashcroft – What do you about planking such a small boat using diagonal planking without a glue (only soft fabric and white lead or shellac between). There is very little information about diagonal planking in this archaic form around. I have only found some pages in chapelle’s Boatbuilding, and few verses In Herreshoff’s “SYD”. I don’t like using epoxy as well as modern planking methods (say plywood lapstrake). Maybe you know some good text about Ashcroft method?
2) Strip planking – It’s rather heavy, I know, so I do not know if it’s applicable to such a small craft at all. What’s more I could use only two three species of wood: Larch, Dug Fir and Oak. All them are heavy, but, what is more important all of them have high shrinkage rates, so In strip planking they could lead to leaking disaster not a nice boat. I could use Norway spruce to, but it tends to rot quickly as far as I know. Once again, I’m not going to use epoxy.
3) And… Caravel – more like a wide board strip planking in this project. I’m wondering if it could use narrower planks then lapstrake. And of course there remains problem of species of wood in rather thin planking of my boat.

Any suggestions are welcomed. Especially from European builders who have some experience with our native timbers.

I still hope that it could be done traditionally, though I do not know why it’s so important to me ...

Thanks

Lech

 

Ashcroft method has been pretty much replaced with double diagonal planking methods, though I find this to be slower and harder to do. Ashcroft is not quite as strong, but both layers can be applied at the same time, which speeds up the build considerably. You can use traditional sealants between the layers, but I wouldn't recommend it over the modern possibilities. Shellac, tar, felt and the other things used were done so, because they didn't have the real waterproof glues and adhesive we have today. It would be foolish not to incorporate the benefits of these newer materials in an Ashcroft build. I'm just finishing an Ashcroft runabout and I used resorcinol between the layers.

Clinker wouldn't be my choice for a novice builder. It is one of the most difficult building methods around, with repairs being even more difficult. Its advantages are light weight and flexibility, plus the ability to live on a trailer and remain water tight.

Carvel, in small craft, can be quite heavy. This is because the planks require a substantial caulk seam and the planking must be thick enough to accept this. Carvel is is likely one of the easiest of the traditional building methods, with repairs being equally easy.

You're right strip planking can be heavy, especially in small craft with 'glass or veneer and 'glass sheathings. It's a very user friendly method, requiring little traditional boat building skills.

The choice is up to the designer, who often has several alternate planking methods per design model. If you're designing your own boat, then the nature of your questions, suggest a lack of understanding in the fundamentals. This would be a poor exercise, without a more complete understanding of the concepts and principles involved in yacht design.

The traditional methods are wonderful, but in most cases, much of the previously used materials are no longer available or are of such poor quality, that reasonable substitutions must be made. Polysulfide for shellac as a sealer for example. Shellac just sucks in this role, but polysulfide will out live you and your grandchildren. This is just an example, another would be finding suitable solid planking stock for a lapstrake build. Thin, stable, vertical grain softwood, will be quite difficult to get in the lengths you need, even though it's only a 10' boat. The cost of such lumber will be quite dear. It would be a sin to have butt blocks or scarf seams in the planking of a ten foot boat and certainly not very traditional.

These substitutions can be had with a modern set of plans based on a traditional hull form. There are quite a few of these types of plans (hundreds) available, including several of my own. You can contact me by clicking on my name and sending an email or by one of the many plan sellers or design offices around the world. It would be a strong recommendation to suggest you use a set of plans rather then attempt to develop a design yourself. Small boats are particularly sensitive to weight, material usages and shape. These aren't things that the novice builder/designer would typically understand.

 

if you can loft the individual planks, narrower pieces can be scarfed together with epoxy to form a shape that will allow the plank to be cut from it with minimum waste. be sure to vary where the scarfs occur to maintain hull strength

 

You obviously have some knowledge of construction. Possibly enough to get away with a lines drawing and do a bit of your own design work by figuring out the scantlings and framing for your chosen method.
The Norway spruce is light and will lend to strip method, which also happens to require the least design expertise. Rot issues would only follow poor construction resulting in other kinds of failure, so don't worry about rot in a boat skinned inside and out with epoxy and cloth.
Atrip planking spruce would make a light and strong boat. In fact, outside of the qualities of rot resistence and expansion resistence of cedar, which shouldn't come into play in encapsulated construction, spruce is actually a better choice. Nobody would use cedar for a mast if they could get spruce or fir. Why? Because cedar, for all of its other qualities, is not as strong for its weight.
I recall an issue of WoodenBoat that had an article on traditional Polish boats. Poland has a rich seafaring tradition. Perhaps there are a few builders you could contact closeby. I remember the Polish sailing workboat designs had side-tilting daggerboards in a vee-shaped case---- a real development that is still a great idea.

Alan

 

I am sure there must be some boat builders in Poland who could help you locate materials. It may be very difficult to find them (the builders), but if you can it could be a great source of information about your local options.
Have you considered the possibility of trying to redesign the shape of the boat so it would not require such wide planks?
I believe Western Red Cedar would be perfect for a small lapstrake boat. I do have some boards that I believe are 13' long. I can't remember how wide they are. They are socked away in my lumber pile and I haven't looked at them for a long time. I expect the freight would be prohibitive, though.

 

Thank you very much for your replies
I think that I have to add some comments to my 1st post:
- Im not designing. I'm going to build Ian Oughtred design "sheerwater". It's intended for Ply + epoxy, but can be adopted to traditional lapstrake construction (I have Ian's notes on adopting). I know that changing to other than lapstrake planking method needs some redisigning, but I do not fear it.
- I thought about scarphing, but problem lies in upper strakes, which due to sheer line, have reverse turn, so I would have to scarph in three pieces and put all scarphs in one line to take the advantage.

My main questions are
- do you know some good source of information about traditional ashcroft diagonal planking
- Is Larch suitable for caravel or strip 1/2'' planking (taking to the account its shrinkage rate) I'm not going to cover planking with glass. maybe battend caravel would be an answer?

tomorow I start bike trip around my building place. there are some small lumber mills around. If i don't find suitable spruce or larch stock I will turn to ashcroft or stripo planking. I'm gonna to visit some tradboat builders too.

kind regards
Lech

 

As well you know, Chapelle describes the traditional method.
Scarfing ply may indeed take two scarfs, if you were referring to ply. It's all part of the building process. A glass skinned boat can be epoxied simply by butting ends together, The stress is on the skin, and as such I'd glass those joints double inside after the plank is hung. Very strong.
I wouldn't recommend glassing over solid wood over 4" wide, though I don't see a true traditional lapstrake with wider planks except possibly at the garboard area. Glassing seems appropriate on wider lapstrake (ply construction) but not on traditional anyway.
I know little of larch, but I know thast at least some species of larch make for good planking wood for larger boats, which is to say it is probably heavier than you would prefer (to say, pine, spruce, or cedar).

A.

 

It's extremely difficult to 'glass sheath lapstrake craft. With traditional lapped hulls, the planks move around quite a bit, which will sheer any sheathing pretty quickly, not to mention getting it stuck well at the laps. I can't think of a single book that covers Ashcroft planking method in detail. It's not dissimilar to a cold molded build, just the planking layout is in the same direction rather then double diagonal.

 

I am no specialist in the wood but I have sawn in the past with my dad. Back here - not too far - in Finland there are number of small antrepeneurs who have mobile tractor pulled sawmils. Might be overkill for one dinghy but I am pretty sure local farmers and forresters do similar stuff there. Finding the right people might be the tricky part.

In the past we had a friend come by with his big circular saw setup ran by a tractor. very efficient business in few days you can fly through quite a pile of lumber. Nowadays my dad and other older neighbour farmers co-own smaller bad saw rig that runs with a 12hp Honda. If the blades are sharp and the operator knows what he is doing the results are great and much less waste than on circular saw.

h

 

That's a good system, h, and more people should get together and make planks.

Alan

 

I know this is a long-dead thread, but if someone happens to stumble on to it, here is a link explaining Ashcroft Diagonal Planking.

The Ashcroft Method for Planking a Wooden Boat Hull