Looking for wood species in Asia for strip planking

Paulownia is excellent for sheathed strip planking.

Its mechanical properties are on par with a good cedar, it's a bit lighter, quite resitant to rot, and it's dirt cheap all over SE-Asia and China, because it's a local wood, grown big-scale in plantations. Only downside is that it is less nice to saw and abrade.

It's NOT suitable at all for ordinary strip plank construction, only for (Epoxy/Fibre-) sheathed strip construction, because it sucks up astonishing amounts of water (doesn't rot though)

Botanical Name: Scrophulariaceae Paulownia Tomentosa
Trade names: (Royal) Paulownia, Paulonia, Polonia, etc.

[trimix]

Originally Posted by erik44

Paulownia is excellent for sheathed strip planking.

Its mechanical properties are on par with a good cedar, it's a bit lighter, quite resitant to rot, and it's dirt cheap all over SE-Asia and China, because it's a local wood, grown big-scale in plantations. Only downside is that it is less nice to saw and abrade.

It's NOT suitable at all for ordinary strip plank construction, only for (Epoxy/Fibre-) sheathed strip construction, because it sucks up astonishing amounts of water (doesn't rot though)

Botanical Name: Scrophulariaceae Paulownia Tomentosa
Trade names: (Royal) Paulownia, Paulonia, Polonia, etc.

I heard about this wood but I don't find any reliable values about its mechanical resistance ! All the values needed to calculate the scantlings of my boats. If someone have them, I'm very interested in.

[nero]

This is good news. When I think of strip planking, I think only of epoxy encapsulated with fiberglass layers inside and out.

So, I am happy ... if I can find this wood at a cheap price. I did a net search and found that it is grown commercially in Georgia, USA. This is a lot closer to me than the WRC.

Do you know of an importer of this wood? Perhaps it is even less expensive from someone who has brought in from Asia? I am looking for 3,000 bd ft. I have the values in cubic meters ... somewhere. smile

Thanks for the info!

[trimix]

Nero,

Before building with that wood take care of the possibilities to register your boat when built ! In Europe, it seems to be very hard to register because the wood is not as known as red cedar !
Besides how are you sure that wood fits your requirments ? How do you calculate your scantlings ?

[nero]

Trimix,

You brought up a very good reason for one of my decisions to build in the U.S. (probably other contries that apply too) As to my research to date, all I have to do to have my boat title of ownership is send in a form and small bit of money to the Illinois government. Then it seems that I need to send in a form I downloaded from the U.S. C.G. and again pay around $250. I can have a free safety inspection by the U.S.C.G. also. (this applies only to how the boat is equipted and what I need to be in regulation. Then I can risk my life and go sail it anywhere. ... or at least to the country whose flag I want to sail under.

In France, my wife (french), found out that my plans have to be authorized by some french agency, then the building place authorized, several inspections thu out the build process, and a final control check out before they give me a "certificate of navigation". Then it would seem that I would need a boat drivers license ... for the dingy (if the motor is over 10hp) My 14 meter cat will not require a sailing license even if the motors are over 10 hp. And I can not sell the boat for five years after the certification.

I am not looking to complicate my life! (... so why did I marry a french girl? you ask) smile

This boat is adventure ... and is for the adventure. (it is posted under sailing multihulls) If I had lots of money ... or even a little money, I would hire a group of talented Marine Architects. I do not so I am digging out the best alternative. This is in design, cost, cost/performance, and availability.

Catamarans in the 14 meter range built in WRC use between 15 and 19 mm strip planking. If I use equal thickness and like fabric layups. The results of the hull will be about the same. If I change something then I need to comprehend the way I am changing it, and the effects.

If I go to a wood that has a lower density, but a higher density/strength ratio, then a bit more of the wood will give like structural support. Other advantages to having a thicker hull and core are enhanced also. (sound, heat insulation, impact absorbtion)

Other than that I find other things to worry (or investigate) about. Like the bridge deck cross structure. (This is the part of my design that sees all the twisting, bending, magical, loads. smile

[trimix]

Nero,

I think that your approximations are too approximative !!!
You cannot choose the same scantlings for WRC and Paulownia. Strengh/weight ratio is one thing but this is the proper wood resistance which is interesting. Particularly the shear resistance is not as important as the WRC one. So you will problably have to increase the scantlings of fiber glass. I'm not a specialist but if you want your boat to be resistant take care about what you do !

[nero]

Your absolutely correct.

Of course I am still interested in this wood. So, the shear longitudinal to this wood is not as important as WRC. It still is a lot more than any foam. (this is a guess from the spec sheets I have seen)

I am planning to make these hulls a bit thicker 20 mm, with a layer of 10 oz boat cloth layed on at 45 degrees, then another layer of 10 oz. in the longitudinal direction. (triangulate the fibers). And since I am building on a female forms, I can do this inside and out (balanced I beam).

The extra thickness should equal or exceed the strength of WRC structuraly. In load transfer between the skins, the same amount of force if it was WRC or P, should be recieved by each skin. Only the skin will take up the load quicker since the moment is longe and the fibers will come into their working tension quicker. Perhaps this will result in a stiffer hull.

Perhaps I should add that the wet hull (area below the WL) and a bit above this will be strip planked in Black Ash of Cypress with a bunch of stringers and a full length keelson.

Does this information make you feel better? smile

I visited the sight of a harryproa this past summer. 8 and 12 mm WRC with one layer of cloth. on a 12 meter hull. Of course these are two entirely different boats.

Trimix, Nero..

About the relative mechanical properties of WRC and Paulownia:

You said, you wanted "reliable values for mechanical properties".
There's no such thing: A plank of WRC you can buy in place A at time A may have wildly different properties than one from place B at time B. Same goes for Paulownia.

Still, some woods in some places are relatively homogenous in their properties, because they are grown and processed on a quasi-industrial scale. For these woods, you can rely on published figures. WRC in in American North-West is such a wood, usually. Otherwise, published values are only good to establish the relative merits of severals species of typical properties.

If your boat plans call for, and are calculated for WRC, any wood with similar, or better longitudinal strength will do as well (for sheathed strip planks ). Obviously, the caveats about knot-freeness, not being oily, rot-resistance, moisture content, and weight apply.

Shear strength is unimportant, as all the shear loads in a sheath stip planked hull are handeled by the GRP skins. The shear loads the wood will have to handle are those of load transfer between the two skins, and any wood that is not paperweight (like balsa) will to that without further calculation warranted.

Buy some planks of WRC where you would buy them for "the real thing", and some of Paulownia. Bring then to the same dimensions (say 1" x 2" x 10 ft.) and let them dry to your environmental conditions. This will yield between 12% and 18% wetness, depending on where and when you do it. These figures represent about the upper and lower limits of wood suitable for epoxy/GRP sheathing, incidently. Then do some simple and repeatable mechanical tests on both specimen, like bending weighted planks over levers, and such like. Also, observe how much their weight differs per volume. See how the two compare mechanically (impact, workability, etc). This is all the precision you'll need for material properties.

If they differ much in either weight or strength, you'll have to recalculate the scantlings. Do this only when you really know what you're doing.


Besides: The thing about heavy regulation or supervision by gov't authorities in France, or Europe in general, is a myth. This is for boat yards or production builders. If you build a boat for yourself, and don't sell it within 5 years, there's zero regulation.

To drive you boat legally, you do need a "driver's license" in most places (Britain being the only exception in the EU I know of), and this does practically restrict you to 15m, (49 ft.) length, because the licenses for longer boats are really involved affairs (time-wise and financially). A 15m license will cost you about $200 and is a one-week-end affair. If you hold a license that is legal in your jurisdiction, or your jurisdiction does't require a license, then of course you don't need the European license at all.

Erik

[nero]

Thank you Eric44!

Not only do you understand but you comprehend also. Rare these days.

As for Paulownia here in the states: What seems to be the situation is, It is too early to use this wood here. The old wild growth trees scattered thruout the east coast are gone. They cut and exported to Japan. The plantation trees are still too young. The Paulownia association is starting to cut a few for marketing purposes. When the wood does come available, it will not be cheap here! (cash crop)

To import the wood it costs about $2.50. But the minimum quantity is something like 50,000 bd ft.

I did find an old boy down in South Carolina who has 1,500 bd ft. He is letting it go for $1.50 bd ft. Lengths are 4 to 8 ft. (a bit short for me)

Also, the wood is not rot resistant. This accoarding to the president of the association that grows it.

As a result to my wood search, I found a small company in Texas that saws Cypress. By chance he had some old growth WRC beams. He is sawing these up for me at $2.50 bd ft. Unfortunately, there will not be enough to plank all the boat. So, I will be making some of the parts in Cypress. (a bit heavier, harder, not much stronger) The cost is $1.40 bd ft (green)

So France has zero restrictions. Are you trying to ruin my get-away vacation? (smile) I will not tell my wife (a true green frog) about this. She is the one who found information on building boats there. I tend to trust your advice. Maybe I will build my annex (dingy) there.

Thanks also for the down to earth talk about wood cores.

Ah, I got this mixed up: You're in the U.S. , whereas the original poster of this thread was from SE Asia, apparently. For him Paulownia would have been the easy route, for you it would be an oddity. Stay with the wood you find locally, amd in abundance! WRC is premium wood, white cedar is barely o.k.

Besides: For plywood (in the U.S.), stay away from local brands and buy Canadian, just to be safe. 5 years ago, U.S. plywood was the worst there was. (In the Seattle Area. This may or may not have changed.) Imported wood was much better then, prdominantly Canadian, German and Scandinavian brands. Some U.S. manufacturers used to hide behind scandinavian-sounding names, so beware.

France... I built a boat there in the late eighties. La Rochelle was then the epicenter of amateur boat building in Europe, with building space, materials, parties, help, (and advice, both good and bad) available for a song like nowhere else. Catamarans were very popular, too. All this has ebbed a bit (I've heard), but is still going on. You should be able to speak French, though...
In France, people usually build (sheathed strip) with scandinavian pine, or siberian larch if they can afford the weight penalty. Or, indeed, with WRC in its "speed strip" mutation. If you have the time and the resources to relocate for a building project, France may still be the place to be, although the weak Dollar may dampen its attraction for you somewhat these days

erik44

Nero,

I hear you local pope for Paulownia says it's not rot resistant. That's interesting, because my (limited) experience with the stuff says otherwise.
But then, not all Paulownias are alive, and there's this rot and that rot.

The rot of concern in a sheathed-strip plank environment is the oddly named "dry rot", which are some funghi that thrive on wet(!) wood, and need only marginal oxygen and fairly commonplace temperatures.

Then there's rot, which are actually bacteria, that hardly need water at all, but want sunlight and lots of air. Must bacteria don't like saltwater much.

There's also other critters and mussels, but these, as a rule of thumb, are only of concern for all-wood vessels, at least outside of the tropics.

From what I've seen, in a dutch built strip planked vessel with polyester/Glass sheating on the outside only, is this:

The original planking was a mixed bag of larch, pine, some sort of mahagony, and unidentified matter on bent oak frames. After 10-15 years service about half of the planks (mostly about the walterline) had to be replaced: This vessel had been in the tropics for 2 years and was coming apart.

A yard near Hong Kong (I think) replaced the stuff with part paulownia, part mahagony. and re-sheathed with polyester/glass. 10 years later, the vessel was at the yard I was with at the time (in Germany). The Polyester had (predictably) come off again, and the hull was wet throughout, and had been for some time. The pine had to torn out completely, and some of the original larch and mahagonny (20+ years old at that point).

The replacement (HongKong 10 yrs old) mahagony was in worse shape rot-wise than the (hongKong 10 yrs old) Paulownia. The P., however, unlike the M., was completely soaked, and needed drying for months. There was talk of stripping the polyester off and replacing with epoxy, but I think the hull was scrapped eventually.

[nero]

I have lived in France for pretty much of the last 11 years. Except for the red wine, health care, apartment rent, and utilities, everything else is almost as bad as Tokyo. (well that may be a stretch)

I have been renovating apartments in and around Marseille. I have business price reductions on all wood, electrical, plumbing, and building supplies. Still nothing is cheap there! There is a good supply of excellent plywood. I always thought it to be expensive until the other day. I bought 45 sheets of 1/2 inch B/C X pine plywood at $20 TTC the sheet. It looked great laying there in the bundle. When I got it back to the barn and started unloading it, the pannels were warping and twisting in strange ways. It may or may not be useable for female forms. I am cutting a few tomorrow to see what happens.

I should have gone an extra $4 a pannel to get 18mm (3/4) meranti plywood. It has a strange core of laminates that have been cut into strips (it looks some what like solid core)

I can take the plywood back and exchange it if need be.

My current income is in euros. So, building in the states is another advantage with the current exchange rate. I also have a free barn. (it cost me $1,500 to clean it up, bird proof it, and wire and add lights.

I have not been to La Rochelle. I have seen some multihulls built along the med cost. The production cats I visited were not the style I was interested in. The one off cats that I saw were CP (plywood). This is probably what I should be doing. I still have too much ego, so I am going to loose some of it by sculpting, fairing, and sanding. (this will also give me a reason to drink more wine when I kill winter in Marseille.)

Too bad I did not hear your advice on La Rochelle this summer. It would have made a nice tour of france to go see the area.

I have bought some WRC from TX. It is resawn from old beams. Also some Cypress. It is heavy but not expensive. I have stumbled across some Lebaneese Cedar logs. Can not find info on this. I think it resembles WRC in characteristics, but it seems to have natural oil in the wood. Not good for epoxy. Ever heard of this?

You bought Lebanese Cedar in logs? I doubt it! This stuff is mighty expensive. Almost all there still remains of it goes into veneer for boxes of expensive cigars and jewellery. It's hard, greyish stuff with a fuzzy surface and smells real good. (And keeps moths away, because it's mildly toxic). Racing rowing shells were made of the stuff in the past, because it's light for its strength.

If your stuff is bright brownish, and of a soft regular texture it's probably from some place in Middle America (Honduras Cedar). Despite the name, it's no close relative of the former. Good allround stuff, durable and easy to work. I'd keep it for the interior joinery (Needs lots!! of varnish). Will of course work well for the hull, too, but it's overkill, and will soak up your expensive epoxy like there's no tomorrow.

If your stuff is more reddish and fibrous, it's probably Tabasco-Cedar, and will not take to the sea...

erik44

[nero]

Did not buy the three logs. They are in texas. It seems at one time planting Lebanese Cedar was a trendy thing to do. Emailed the seller but have not had a responce.

Thanks for the info.

[dogboy]

what about Luan?, aka Philipine mahogany....rot resistant, available, strong...don't know the botanical name....i bought a cheapo park bench with luan slats 20 years ago and you can still sit on it w/o worries