Re: DPV

[shawl@torchlake.com (Jonathan Shawl)]

Calos De Vit Gabriel wrote:

>  Hi Jon
>
> I’m a psuber reader only for two reason
>
>      1- My English is not so good
>
>      2- For unknown circumstance my messages are not send to the
>      discussion group
>
> I’m a scuba diver certified by the "Prefectura Naval Argentina"
>
> (Analog to Coast Guard)
>
> I’m live in Argentina , on the second city Cordoba
> (Mediterranean) but have some goods lakes whit deeps until 60 Mts.
> (170 ft)
>
> and visibility near by 5mts (14ft)
>
> I envy your greats stores where you can find anything
>
> Here is use the saying:
>
> "Argentina donde todo se arregla con alambre o aspirina"
>
> (Argentina where all is fix with metal wire and aspirin"
>
> I will build a DPV for a one person only ,with a old dynamo from a car
> built in the 60’s
>
> The hull for the DPV will be a disposable can of refrigerator gas
>
> My questions are :
>
> How much RPM must be in the shaft?
>
> How will be the shape , pitch, size , number of blades of the
> propeller (I unknown the power of the motor, but I can reach it)
>
> Thanks
>
> Gabriel CalosCÓRDOBA
> ARGENTINA
> TE-FAX 054-51-722-677
> e-mail: gdevit@argosmail.com.ar

  Hello,
Im glad you are reading the Psub e-mail I think a person can learn a lot
from the group.
I do not think I can help you much on your motor and propeller
questions.
Many things enter into what you are asking and it is hard to give an
exact or good answer with so little information to go on.
In general bigger props with more pitch need more power, but it also
depends on the load you are trying to move and how fast you are trying
to move it. If you are limited by the parts you have on hand you may
need to do some testing with your motor and prop to see if it works. On
my sub I found that a large 22" prop turning about 120 rpm works much
better than the 6" prop & 1800 rpm motor I first tried. That is about
all I can add at this time.
Since you are having trouble posting to Psubs I will pass this onto the
group to see if anyone can help you a little more, or give you some
other ideas.
Your letter and your comment (Argentina where all is fix with metal wire
and aspirin) got me thinking.
We psubbers that are lucky enough to be in the US and other industrial
nations, should think about how would we build our subs if we couldn't
just go to the local suppliers and buy what we need. And think of all
the countries you could be in that may take your sub,( if you managed to
build one) and then throw you in jail for building it?  I feel very
blessed to be here in the US!

Jon Shawl