Jargon Buster - Scantling

[Owen]

The definition on Wikipedia is a good start,

but I get the feeling there is somewhat more to this word.

Could anyone spare the time to run us through exactly what we mean by Scantling.

Thanks, Owen.

[alan white]

Scantling means "level of heaviness of construction".

Alan

[PAR]

More precisely, the word literally means the physical dimensions, of the elements that make up a boat. This usually offers a list of each boat part and it's fitted measurements, often following specific guidelines.

[Owen]

So will the scantlings define just the hull, its structure and material composition or do they extend to the each and every boat part?

If so what kind of format are they usually in, a table similar to offsets, or technical drawings with dimensions and notes, etc?

[MikeJohns]

As Par said; It is simply the physical dimensions of the materials. How these dimensions are presented is immaterial. We often talk of hull and rig scantlings separately and the word scantlings on its own refers to the hull.

[PAR]

There are some common conventions in the presentation of scantlings, but it is subject to the designer's whim. I personally list the major elements, usually keying them to areas of the construction drawings. This is a classic application, but I've seen many other approaches to provided the information.

[yipster]

Dave Gerr wrote a good book on scantlings and scantling number called Boatstrength (http://books.google.nl/books?id=y2GT5JyVrzAC&printsec=frontcover&dq=dave+gerr&hl=en&sig=Djy3fi2BShVvPaIWLz-GAv1OqeE#PPA5,M1)

[Ike]

There are various "scantling rules" These are essentially formulas for determining the dimensions of the various parts of the boat;hull thickness,deck thickness, thickness of frames, deck beams and so on. The "rules" vary by material and by whoever made up the rule. For instance for wood boats Skenes Elements of Yacht Design has scantling rules for wood structures. What these really are is shortcuts so you don't have to do the strength caclualtions yourself. Most scantling rules are very conservative and you end up over building.

[PAR]

Not all of them Ike, try building to Herreshoff's rule. You'll get light and strong, though you're generally correct about "scantling rules" producing a heavier then necessary boat.

[MikeJohns]

The Rules are supposedly based on worst case estimates of possible loads.

Sometimes they are not conservative enough, particulalry ABS for racing yachts which have tended to be overly light in some composite scantlings. Initially with composite hulls around the area of keel attachment (corrected 1987 ?) Lately ABS appears to be deficient for composites for deck loads from breaking waves knockdown and inversion, as was apparent after assessing the damage to 'ABS rule' yachts in the 98 Sydney Hobart.

Also beware; scantling rules should only ever be considered a guide, the whole idea of the rules is that conformation indicates likely compliance but to fully comply requires review of the design by the society.

[lazeyjack]

some good terms in our trade, BREST HOOKS
Now watch the silly lot climb on:))

[MikeJohns]

Interesting jargon would be a good thread to start Stu, but in this one he just wanted to know what scantlings meant.
There's 'Breast ropes' too :-)

[Ike]

Yep, I over generalized.

[Pericles]

The EU RCD is not much help. Part of an email I received.

"The first point is to clarify that there is no legal obligation for you to
CE mark the boat at all. If you are building the boat for yourself, you are
classed as "home-builder". The boats of home builders may be exempted from
the EU Recreational Directive after 5 years from completion. In the 5 years
from completion, you may use the boat but you cannot transfer the ownership.

I am not sure whether you are aware of this exemption or not. Many
home-builders do CE mark the boat, however, in order to (a) keep options
open, (b) have the confidence of a professional to call through build and
(c) to have a third-party mark of approval for when they do come to sell-on.
This is entirely your choice.

The next point is to answer your question regarding materials of
constructions. One of the good and frustrating features of EU Directives is
that they are not prescriptive. This means that anything is acceptable if
you can justify it. So no materials of construction are outlawed but it is
true to say that there is no helpful European standard to pull off the shelf
for this type of construction. Some certifiers, who are not very clever at
structural engineering, may refuse to certify with such a construction as it
is beyond their capabilities but that does not make it an illegal
construction.

We can certainly come up with a means of assessment. There area number of possibilities depending upon whether this is a planing,
semi-displacement or displacement vessel. I am not familiar with your
suggested scantling method but I see no reason why a published method would not be acceptable for RCD. We can certainly advise on that and provide secondary calculations if necessary."

The method of construction is S & G, the Jacques Mertens way,

http://bateau2.com/content/view/46/28/

for a DE25.

http://www.bateau.com/studyplans/DE25Cabin_study.htm?prod=DE25Cabin

Pericles