Re: [PSUBS-MAILIST] 200ton 18meter Live aboard submarine

[irox <irox@ix.netcom.com>]

Hi Cliff.

Correct, this is a 4:1 ratio hull.  The reason for using a 4:1 hull is that
is what Wil found successful for his 20ton prototype.  With the 4:1 hull you
get a deeper "belly" and store ballast lower down leading to better dive
stability.  So, the basic reason for using 4:1 is this is what Wil is most
comfortable with.  Although I would prefer a 6:1 hull, being 4:1 is not
going to be a deal breaker for me.

For dynamically trimming the boat, I was thinking of mounting two dive planes
one of either side of the sail.  Also I would like to consider trying
some thing like a V rudder mount on the bow.  An X tail would be fun as well,
but that's not going to happen for a few years down the line.

I want a tall sail/c-tower for surviving bad weather, which is going to
lead to the upward moment you are talking about.  Dive planes on the bow
or c-tower will help, but with added drag.  Actually, I'm hoping to see how
UC-3 hands underwater (nice sail Peter!) and get some ideas on how this is
best solved.

The sail/c-tower in the 3D image might be too much work for the first
rev, so I may go with something more traditional.

There is also more information on concretesubmarine.com.  Wil has put
up all our communications regarding the sub:
http://imulead.com/tolimared/concretesubmarine/anuncios/bd/

Cheers,
 Ian.

-----Original Message-----
>From: Cliff Redus <cliffordredus@sbcglobal.net>
>Sent: Dec 23, 2007 5:42 PM
>To: personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] 200ton 18meter Live aboard submarine
>
>Ian
> 
>Thanks for posting your boats design specs, 3-D rendering and profiles. This will be quite project.  
> 
> I concur with Carsten that you are probably underpowered.
>
>I have a couple of questions for you?
> 
>Looking at the boat shape, my guess is that the asymmetry of the hull caused by the sail will cause a significant pitching moment when the boat is fully submerged that will be more pronounced at higher speeds, i.e., as you go faster, the bow of the boat will want want to pitch up.   I do not see any stern horizontal control surfaces. How are you going to null out this moment to be able to dynamically trim the boat?  
> 
>It is obvious that you are trying to minimize drag by adopting a tear drop shaped hull.  Looking at the profile, it looks like the hull length to diameter ratio is around 4.  A length to diameter ratio around 6 yields the minimum total drag for a streamlined shape like this with values as high as 9 not increasing the drag significantly.  Why use 4 when you could get more speed for the same horsepower with a value of 6?   See "Some Aspects of Submarine Design Part 2. Shape of a Submarine 2026" By Prop. P.N. Joubert, Report # DSTO-TR-1920. Reference Figure 1, Drag components for constant volume form.  www.dsto.defence.gov.au/publications/4897/DSTO-TR-1920.pdf.   Look at the profile for the Soviet Lira ( Alfa Class ) boat www.fas.org/man/dod-101/sys/ship/row/rus/705.htm.  At the time of her sea trials in 1972, she was the fastest sub in the world at 44.7 knots and still is to my knowledge.  She was noisy but fast.  Her length to diameter ratio is closer to
> 8.5.
> 
>With the novelty of using a concrete pressure hull for such a large boat, this will be a very interesting boat to follow.  Please take lots of pics during the build.  Best wishes. 
> 
>Cliff




************************************************************************
************************************************************************
************************************************************************
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
************************************************************************
************************************************************************
************************************************************************