[PSUBS-MAILIST] Determining the size of a rudder

[Tim Curtis <navark@yahoo.com>]

Leifur,

You managed to hit the very thing I was working on
this morning!  I too have an AUV, about double your
size, and just finished all the calcs for control
surface sizing about half an hour ago.  Get yourself a
copy of the Det Norkse Veritas rules which can be
found in the 1983 SNAME Volume 91.  From there, follow
the guidelines for highly maneuverable ships.  Since
your control surfaces are probably in front of your
prop, increase the suggested area by 30%, and then
increase this whole area by an additional 50% to match
empirical data from other undersea vehicles (there is
a paper by Healey and Good about the NPS AUV 1992 that
describes this).  That should get you in the ball
park.

Another option, which is considerably more work and
still not particularly good, is to use torpedo dynamic
stability derivatives.  That gets real messy though -
I don't recommend it.

   -Tim





Hi.

My name is Leifur Thor Leifsson and I'm developing an
AUV. The AUV is
torpedo shaped and is around 1.3 m in length, 0.2 m in
diameter and weighs
around 34 kg.  

Now I'm trying to redesign my rudders and elevators
because I think they
are too large. Both the rudders and elevators are made
from a flat aluminum
plate which is 2 mm thick. 

I am thinking about using a "reverse" airplane wing
for the elevators of
the form NACA 4412. The elevator is supposed to
overcome the buoyancy of
the vehicle, enabling it to dive. I have determined
the neccessary size of
it by using information about lift for this specific
wing section.

For the rudders I am going to use a symmetrical wing
section of the form
NACA 0018. Now the question is; how do I determine the
size of the rudders
so they will work efficiently in all cases (giving
enough force to
manoeuvre the vehicle for various speeds, etc.)? 

Leifur Thor. 


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