Design Help - Power Boat Floor?

Hi

I’m trying to figure out what did DAVE GERR (The Elements of Boat Strength) means by Floor at the formula 5-7 of his mentioned book.

FORMULA 5-7
Fore-n-aft Thickness of floor core (foam or balsa):
In = 3.1 xSn0.3
Minimum height for Floor Cores = 2.5 x the Fore-n-aft Thickness

In the example for this calculation in his 40-foot Fish’n Squish:
Sn of 2.97, would require a foam or balsa core 4.3 inches thick, fore-n-aft and 10.75 inches hight.

I’m really lost here. Can anybody help me understand what exactly he meant by “floor”. Is it the transverse frame? If so the minimum height is in the center of the boat?
Thank you for your time.

 

Ricardo

It is an old shipping term and also (oddly) commonly used term in America.

A floor is a transverse vertical web plate inside a double bottom tank, i.e bottom transverse member only. Where the double bottom tank is longitudinally and transversely framed.

However it is also taken to mean a transverse frame (bottom/sides/ etc); which is not strictly correct.

I fools me at times too, since it is not a term I commonly come across, except when i read/interact with American vessel/rules. It is a term used in some big ship rules too (rather than frame), for some strange reason too, but i suspect its owing to many having double bottom tanks!

 

Hello Ricardo.

If I'm not mistaken, the floor that Dave Gerr is referring to is a transverse timber that ties the frames on either side of the keel to the keel and to each other. There is s picture of it somewhere in his book, quite early on under the wood construction chapter.

Good luck!

 

Completing Hampus information

 

Thank you very much for you all. It is absolutly clear to me now. Very kind of you.