Re: [PSUBS-MAILIST] Electric, Radio, Hull

[Marc de Piolenc <piolenc@archivale.com>]

Actually, speed and power required follow a cube law: doubling the speed 
requires eight times the power (two cubed). That is based on the 
assumption that the main drag component is viscous (skin friction drag 
plus form drag), which is a pretty safe assumption for a fully submerged 
body. On and near the surface, there is also wave drag which follows a 
more complicated law.

Other scaling laws belong to the domain of dimensional analysis, and 
have been well studied and documented. My guess is that any post-1930s 
text on naval architecture would cover the scaling laws for deriving 
full-scale parameters from model tests.

Best,
Marc

On 3/1/2012 4:06 AM, Alan James wrote:

> Double the speed underwater & you quadruple your power output.
> I believe I've heard of people making scale models of their sub &
> pulling them through the water at their
> intended maximum speed with a line attached to something like fishing
> scales.
> I am not sure whether there is a direct correlation to the scaling up of
> the model & the force required to
> pull it at a given speed. i.e.. if your model has a 1 liter displacement
> & takes 100 grams force to pull it at
> 3 knots does this mean that if your sub is 1000 liters displacement it
> will take 100 kilos of force to push
> it at the same speed. Someone smarter than me might want to comment.



************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003.  Your email address appears in our database
because either you, or someone you know, requested you receive messages
from our organization.

If you want to be removed from this mailing list simply click on the
link below or send a blank email message to:
	removeme-personal_submersibles@psubs.org

Removal of your email address from this mailing list occurs by an
automated process and should be complete within five minutes of
our server receiving your request.

PSUBS.ORG
PO Box 53
Weare, NH  03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************