[PSUBS-MAILIST] RE: airfoils

[Alec Smyth <Asmyth@changepoint.com>]

Many years ago I built a simple metal frame with two moveable airfoils on
it. I used this thing to get towed behind a boat at only about 2 knots using
SCUBA, and it was serious fun! During construction, I remember standing on
the edge of a swimming pool and testing an airfoil by sweeping it through
the water by hand (like a broom). When you did the same with the bare shaft
instead, the difference in drag had to be felt to be believed. This might be
amplified by the passage of time, but I recall it feeling like a 10:1
difference. As far as I know the point of streamlining all hull apendages is
simply to reduce drag, and dive planes are pretty major appendages.

-Alec 


-----Original Message-----
From: Chris Horne [mailto:chris@chrishorne.com]
Sent: Monday, March 05, 2001 4:19 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Re:


I believe this is correct, as well. 

As a side note, 'Concepts in Submarine Design' refers to the tendancy of
the airfoiled sail (looking from the top) of larger subs causes them to
tilt when turning. Also, if there were no advantage to airfoil'd
designs, I'd make me wonder why so many dive planes on real subs are
built in a airfoil shape.

-chris

Nero Wolfe wrote:
> 
> And as a seccond note :)  Bernuoli's princapal is not dependant on
compressable fluids (aka gasses)  It works in all fluids.  airfoils aren't
about compressing a liquid.  they are about making the liquid on top of the
airfoil move a longer distance (read go faster) than the liquid on the
bottom.  Faster moving liquid on top = lower pressure = lift :)