Re: 1 ATM Sub Question

[shawl@torchlake.com (Jonathan Shawl)]

Jonathan Wallace wrote:

> I have a question regarding water displacement and the
> weight needed to effectively submerge a submersible.
> Does the total vehicle weight needed to become
> neutrally bouyant equal the weight of water displaced
> by the vehicle?  (I understand that a sub can penetrate
> the water when somewhat positively bouyant)
>
> So if I calculate that my sub displaces X cubic feet
> of water and then multiply X by the weight of 1 cubic
> foot of water, is that how much my sub needs to weigh
> to submerge?
>
> Jon

Hi Jon Wallace,Yes you are on track. If you have all the exact physical
dimensions of all the parts of your sub that displace water, and you
calculate the volume accurately you will be right on. But in real life
you come out just close enough to take to the lake then add the last
trim weights to get it real close. Remember you always need a trim tank
to get it just right when you start each dive and to compensate for any
small differences due to water temp hull shrinkage etc. I have a 40 lb
trim tank for my 4500 lb sub. It's plenty for my sub + or - 20 lbs will
do a lot. Remember if you are negative at all even an ounce, you will
just sink to the bottom, and if you are positive you will float to the
top.
I have the best results if I go a little negative at the start of a dive
then after you reach bottom blow out small amounts until you just start
to hover off the bottom, then use your motors once in a while to hold it
down. If you use motors to hold you up then you won't see anything but
mud.
Jon Shawl