WOODEN BOAT SCANTLINGS

[Adrian77]

Dear Sirs:

I'm carrying out a complete project for an already built wooden ship,(two masts and L=12m). I would need some information about what kind of rules would be usefull in ordeer to scantling the main structural members. I would also need information about how to include the sail effect on the stability calculations as well as info concerning natural air ventilation systems on accomodation spaces on sail ships (double cone exhaust, etc...).

Thanks in advance for your answers.

 

[eponodyne]

Hi,
I'm not sure I understand your question as it's posed... Is the vessel already finished? Are you working on a restoration? What's going on here, really?

As far as rules of thumb for addressing scantling sizes: Look to the past. The old designer/builders such as Herreshoff, Fife, and Atkins knew more about applied physics than they would've cared to admit. They determined scantling size and position largely intuitively, but with so much experience; modern testing has shown their construction specifications to be well within "acceptable" parameters.

It's not just strength of structure that determines scantling size (though that certainly plays a part!). If the boat is plank-on-frame, will there be enough wood in the frames to allow for refastening? Is the turn of the bilge too quick to allow steam-bent white oak its full strength? How about if the vessel runs into an awash CONEX at 9knots some breezy night at 0300 hours?

Sorry I can't be of more help, but I would say find the oldest and crustiest boat carpenter in your local shipyard and buy him all the ale he can handle whilst pumping him for info!

Kind Regards,

_____________
eponodyne

 

[Adrian77]

OK, the ship is already finished, is very old boat it was used during a lot of years to pick the mussels and carry them over deck (this deck is still very reinforced with beams each 100 mm). The ship has been modified adding him two masts andother modifications for sailing, now we need the documentation for the flag authorities, so we must perform a basic scantling calculation to justify the actual size of beams and frames. Local ship carpenters have already worked on it and there won't be any kind of problem in this way... We have sailed with all the sails and everything was ok (stability, seakeeping, etc,..) The biggest work is to draw the required drawings and measure the whole hull in order to obtain a hull form drawing.

Kind regards.

Adrián

 

[eponodyne]

Greetings, Adrian;

After some thinking about your situation, I realized that every possible answer to your questions about the sizes of your framing members cam be found in one volume:

It is titled WOOD As An Engineering Material; I forget the author, but it's published by the Forest Service Laboratories at the University of Wisconsin. Price is something in the area of $40 U.S. Contains tables that show relative strengths (Modulus of elasticity, properties under torsion loads, suitably in depth for your needs; as well as entire chapters devoted to understanding why glue even works at all on wood, and why some species are rot-resistant and others aren't...)

I hope this helps.

 

[sorenfdk]

Hi Adrian

Wood as an Engineering Material won't help You much as it - as far as I remember - says nothing about determining the scantlings of boats. But it is a great source when it comes to mechanical properties.

I would instead recommend one of the old classic books about yacht design, Skene's Elements of Yacht Design. In it, You'll find information about determining the scantlings as well as information on stability and ventilation.

You could/should also get in contact with one of the classification societies (Lloyd's, Bureau Veritas, Germanischer Lloyd's etc.) Many of them have rules and guidelines for the design and construction of wooden boats.
I have used the rules of Germanischer Lloyd's a couple of times, and they are quite straightforward.

Using the rules of a classification society has another advantage: The authorities know these rules.

Hope this was helpful!

Søren

 

[eponodyne]

Well, Soren certainly can give out the good advice!!

Kudos!

 

[unclesyd]

Yake a look at this website.

http://www.woodenboat.com/

 

[sorenfdk]

Hi again

First of all: Thanks to eponodyne!

Secondly: You could also check this website out:

http://www.boatdesign.net

There are some great forums there, too!

Søren

 

[nerozen]

MacNaughton Associates have a scantlings for sale. They cover all types of wooden boat construction. They have a web sight

http://www.macnaughtongroup.com.

They will gladly take your phone call and are enthusiatic about wooden boats.

 

[atahawaii]

Lloyds Rules for wooden vessels would help. Det Norske Veritas has some rules for the sailing rig mentioned in the first edition of Principles of Yacht Design. Dave Gerr's book on Boat Structures would help some. These sources give actual values of what the scantling sizes should be. There are many other sources that simply talk about the subject.