Re: [PSUBS-MAILIST] Need advice, new builder.

[MerlinSub@t-online.de (Carsten Standfuß)]

Hi Stan, 

you wrote your main cylinder is 24 x 75" ( 610 x 1905 mm) 
and your tower cylinder has a diameter of 21" ( 533 mm). 
If you want to sit upright - the tower should be at least 400 mm higher
at the top than the main cylinder. This indicates a volume
of 557 Liter plus 89 for the tower and some more for the ouside 
displacements like thruster, engines , lamps, keelweights, manipulator
etc. 

All together about 700-750 Liter equal to a displacement of 0,7 -0,75 t. 

There is no rule how much freeboard or reserve bouancy a midget 
sub should have - but a G.E.G - Rule (general estimate golden rule)
says that the reservebouancy should be between 10 -30 % of the ships
displacement for subs which want to travel also on the surface 
- especially with open hatch... 

Smaller boats and boats which needs more seaworthness should have the 
greater number, bigger boats and lake boats could have more in direction
to 
the smaller number. 

Sgt.Peppers ration is about 500 Liter to 90 Liter =  18 % reserve
bouancy. 
Sgt.Peppers is pretty stable in all directions with me standing upright
on the pressure hull short before climbing in. 
 
CSSX ratio is about 57 t to 10 t = 17 % reserve bouancy. 

Your figure is : 700 liter to 45 Liter = 6,4 %. Thats is very low. 
If you sit inside and a beautiful girl sitting for pictures on the 
hull - the sub started to dive.. You should maybe double the 
soft tank volume .. Your 16 inch (400 mm)high tower alone has 
about 80-90 liter volume - and will come out of the water just half
way.. 
(The pressure part volume of the sub which comes out of the water is
equal 
to the volume part of your tanks which stays under the waterline.) 

You have 12 x 3,8 = 45 Liter = V = displacement over the waterline 
You tower diameter is 21 inch or 0,533 m = D 
and with H = high of the tower comes out the water 

V = ( D x D x 0,785)  x H  or 
H = V / ( D x D x 0,785 ) 
  = 0,045 / 0,533 x 0533 x 0,785 
  = 0,2 m or 200 mm or 7,9 inch freeboard. 

You freeboard should at least so great that the complete tower
comes out the water (about 16 inch) - and for a better surface 
stability the main pressure hull in the hole longitudinal direction
 - to create a waterline .. 

The aluminium/epoxy combination is exotic - but why not.. 

Good look with the "Tauchende Ente" , 
regards Carsten
 

Stan Muller schrieb:
> 
> Hi All,
>    I have been visiting your web sites for the past six months, and now
> I'm trying to apply some of what I have learned. I am building my own
> dry submersible. (Diving Duck)
>    I have two aluminum cylinders (tanks) one is 24" by 75" and the other
> is 21" by 62" The larger is to be the hull and an end of the other is to
> be the conning tower. When assembled, the 1/8" aluminum will be covered
> with several layers of hand laid 6 oz. fiberglass epoxied on. There will
> be five, lexan 1/4" by 6" diameter portholes in the conning tower. two
> six gallon ballast tanks will be mounted on the exterior of the hull,
> and will be blown with CO2.
>    I have built a 6' articulated arm with a grabber that will be mounted
> on the port side of the hull along side and below the conning tower,
> where it can be seen from the inside. It is built with pivots at the
> wrist, elbow and shoulder, and will follow the movements of my arm
> inside the sub. There will be no through hull mechanical fittings, for
> the arm, as it operates with hydraulics.
>    Maximum depth of operation will be twenty feet, being at one
> atmosphere with a surface air supply through an umbilical from a tender.
> It will be sealed and pressure tested to thirty feet, before any trials.
> Emergency air will be onboard, as will drop ballast, and the other
> safety measures, that are outlined so well on your many web sites, will
> of course be included.
>    Now for the questions; Am I on the right track so far? Is there
> anything that I should be concerned with that I haven't mentioned? Do
> you think that 12 gallons of air ballast will be enough if everything
> else is properly engineered?
>   Any and all assistance will be appreciated.
> Thanks and best regards, Stan in Missouri.