diagonal planking

Just a nice boat picture for Boston. http://www.boatdesign.net/gallery/showphoto.php/photo/5587

 

I'm a very lazy man so I go always to the simplest:

There has been some confusion of vocabulairy:

Diagonal planking, almost classical: mecanically fastened, or riveted, or nailed. That was primitively a double planking, the two layers are separated by a compound. A lot of things have been tried; white lead, oiled calicot, tar, and at last glue. The planking is done over a classical structure: wood, or steel or aluminium (German S boats).
Some boats have a V bottom double planked, chine, and classical top sides.
An old method. But very useful for example in Third world countries for fishing boats because it can use simple materials and galvanized nails.

Strip plank: there are a lot of variants:
-One of italian origin, used on fast boats with slim strips all glued and nailed over a classic structure.
-One of North American origin, used on fishing boats entirely nailed with a compound between each plank. The purpose to use very smal planks which swell very little.
These methods are obsolete now.

-One appeared in the fifties I think (at least one french shipyard was using it around 1960) using resorcinol or similar glues. Finishing with nylon cloth (Cascover for example) glued with resorcinol. I know several english examples.
A light classic structure remains. its the beginning of the strip plank we know.

- First variant: Cold molded wood is very time consuming, a lot of pieces of wood to adjust, spill, glue and a lot of grapes or nails to put and take off after, plus a sanding at each layer.
So why not to replace the central plies (3 for example) by strips of same thickness of the replaced plies. A lot of job is saved. At least 2 outer and inner plies at 45 degrees are required.
Very strong. A light wood can be used as strip, the requirement of quality is lower so cheaper wood can be used. A lot of big yachts have been done by this method. An fast calculation shows if the skin is thick enough a lot of internal structure can be saved.
Little problem: not for yachts under about 50 feet. It would be too heavy on a 35 feet for example.
If I understand well it is about this method you're talking about. In epox class finishing with 6 or 10 oz glass cloth, many times clear and varnished.

- Second variant is going further to composites and to replace the outer plies by glass, kevlar or carbon cloth (kayaks) or UD, or biaxial on bigger boats. It's a sandwich where the core is active and gives the longitudinal rigidity, the fibers at 45 degrees give the torsional strength. The structure is totally suppressed, only remain a few bulkheads. I won't describe all the possibilities of playing with the densities and thickness of the woods used as core (you have also the Duracore strips) and the fiber reinforcements.
It's my preferred method.
First you can make virtually any shape without using a costly mold. For a one off boat it's a big saving.
Second it's reasonably fast and rather foolproof. Difficult to make a total mess. I have seen once the infusion of a sandwich boat going wrong; expensive accident.
Third the outer and inner fiber/epoxy skins are rather thick (ok not for varnished boat...) so the resistance to impact is pretty good and the waterproofing excellent. Very little probability that water will find its way into the wood. Generally these boats are totally impervious to rot.

The first boat I saw using this method was in 1976, and last time I saw it 30 years late it was like new. The method asks a good epoxy resin with 5 % elongation and rather fluid (about 1000 centipoises), a resin too rigid will give trouble.

There a lot of small tricks speeding and easing the construction of a strip plank composite boat. You can attain ratios of rigidity/strength/weight very good, juste under sandwich and exotic fibers. But if you add a fourth factor: cost, that becomes very hard to beat.

The nicety of the method is a relatively low tech method so it can be done by a good amateur or a small shipyard without a costly tooling and installation.

I have used it on several fishing boats (alone or combined with plywood) and on a Formula 40 race catamaran in 1989 (just at the moment when the french federation killed the formula...) and I think that 1900 kg complete, ready to sail is a very good weight for a boat made in a barn.

The formula 40 trimaran Adrenalin by the Gougeon bros used the same method.
Ilan Voyager, the motor trimaran designed by Nigel Irens, built in strip plank/fiberglass in 1989, goes well and strong 20 years later, used as ferry in Cabo Verde Islands (hard seas in this place), and makes the journey from Africa to England directly...nice for a 5 metric tons (dixit Nigel) boat for 21 meters long. Ultralight doesn't mean delicate.
This boat reaches 28 knots with a single 250 HP Yanmar 4 cylinders and made the trip around Great Brittany (2200 nautical miles) at 21 knots of mean speed...Never had a structural problem. That's proof, not unverifiable claims.

 

Completely d accord, and as mentioned above "wooden sandwich".
But the "strip planking" methods promoted and widely spread for amateur buildings have NO inner layer of hardwood or glass usually. So the whole junk is weaker than a multiple diag ply of cold moulded (a irritating term, the usual high tech layup is tempered to degrees that would ignite some bare wood) veneers.

the "unverifiable claims" were addressed to?

Regards
Richard

 

more - really nice boat indeed
http://www.cannellclassicboats.com/cbb_acadia.html

 

no worries Richard
and you got me
Im all about building it
the living in it part is just gravy
Im about done contracting and as soon as I get my stock trading account up to limit then Ill probably never work again
at least not as a contractor
ill play the rest of my days building boats and occasionally sailing off into the blue

those old commuters suet my tastes just perfectly and I think I can make a few minor alterations to the hull form that will seriously improve on there seaways

Im also guilty of knowing all about one thing
old school building, caravel or clinker planking, pine tar and whiting
copper bottom paint

I got joinery down and I remember a few things about basic seamanship
but thats about it
I know what woods I want where
although Ras clued me in to Black Locust and I am better off for it
cant believe Id never used it for anything before

I want to build and be left alone basically
Ive learned to hate my customers and love my job
building
Ill be building till the day I drop

its the design elements that I need work on
each carefully ties into another to make a whole
one piece out of place and youve made a useless hole in the water as old Roby used to say

nice picture Ras
your killing me

APex

close
but no glass or epoxy glue
Im going to go with the diagonal planking between two longitudinal layers all wood and bedded in 9 lb shellac with tree nails turned out of black locust
Im still up in the air on what glue I might go with but sample shellac is on the way and once I boil some up Ill know a lot more
I am preferring shellac because its permeable to vapor and not liquid which will allow the wood to breath, its completely safe ( you can eat the stuff ) and it used to be used as a bedding and as glue, so might as well test it and see what I see

the exterior of the hull will be painted in epoxy paint and copper bottom
over shellac
with everything else lathered in shellac over light stain
depends on what and where

best B

 

I agree with you Apex: a sandwich must have 2 skins to be effective...I know the reasoning behind no plies inside so you put a little varnish and go on, if the strip is thick enough. But I do not feel that safe in a high stress event. Light woods are not strong in shear.
If the guys ( NA) could show me a good pack of data, trials, destructive experiments etc I'll admit. But without that all the experience ask for 2 skins.

Boston you'll build your boat as you want. You're a free man. But unhappy are you for hating your customers (said with Yoda's voice...)

 

Boston,

Shellac originally is the excretions from the Lac beetle, it was mixed with metho to form what we call shellac. There are modern versions of this that are in fact plastics, so be very careful what you are using if you expect to retain the qualities of the old shellac.

 

Sorry Ilan,

a little varnish?

who promoted that? Or was that not addressed to me?

 

holly boat building Batman

I knew one of you home slices would come up with something
those guys didnt modernize much but they sure got the look I was after
my bet is they are the ones to check modifications on my Elco plans

maybe not, I dislike the ribs to keel assembly technique and would have liked to see her being built the easy way,
upside down. The teak cockpit was well done and the raised panel was well done but the companion way steps edge treatment was not a large enough piece and looked unsupported by the stringers or the risers. There steam bending technique would have sent old Roby into fits and the lack of horizontal supports from beam to beam almost guarantees an uneven top side. Im probably being to critical of there style but we had a set manor of building back in the old shop and any deviation from it was always more trouble than it was worth.

 

Boston
the black locust is a very nice wood
and a very difficult to machine one as well!! It has his valuable properties though. And I would like to talk my clients into it for a substitution of Teak decking, but boaters are thumb, blind, greedy and scrooge if it comes to a sort of skimp on their dreams.
And the boat you would love most if it was the shape and nothing else is:

This???

 

ya I found a suplier of old school shellac buttons
they offer bulk discounts for boat building and are dying to have me use there product
Ill send random samples to a chemist friend at the university to have it checked for authenticity as I hear the fake plastic stuff is indistinguishable from the real stuff

 

that would be spounce
french schooner
I looked into it long ago
the guys prints are extraordinary with every screw and its placement noted
a work of art he should be dam proud of
I dont really have enough good things to say about that boat but its got the same issues as the Sophia Christina in that although it is flawless for its intended use it is less conducive to live aboard use than one of the old commuters

Ill give the locust a turn on the lathe and see how it does
it can be a little rough and still work as a nail its just I insist on the old tapered real tree nails instead of just a dowel on planking
as I kid I turned thousands of them
boring but if you want it to hold with or without glue
Ive also whittled barn spikes
tells you how old school the folks were eh
B

 

for those of you who know were I sorta work
I got offered a grant today to cover all my expenses
one step closer to having a real job
( fingers crossed )

and was asked to do the training for the volunteers
which surprised me since Ive only been there for a few months

 

thats great news

 

Yes, it is "Shpountz" and it is In My Humble Opinion the furthermost designed and engineered boat ever. (In terms of ability and beauty for a pleasure craft)
And the most beautiful watercraft I have ever seen!
The prints are unbelievable exact and as you mentioned every single bolt and screw is shown in the drawings!! I have never seen any NA doing such effort, even at three times the fees.
Regards
Richard