[PSUBS-MAILIST] Hydrodynamic question

[Alec Smyth via Personal_Submersibles]

Hi Jim,

That is quite the addition to the fleet, I can't wait to see it in the
water! I recall one PSUBBER with a large sub, though not quite as large as
yours, who keeps a largish weight inside the cabin. I'm guessing it was
maybe 30 lbs, but it was years ago. The weight had a handle on top and
carpet glued underneath. He simply slid it forward or aft to trim the boat.
Longitudinal trim is very sensitive to weight displacement. For example, a
K250 changes trim visibly just when you open the hatch (the weight of the
hatch is further aft when open.) With that sort of length to move things
around in, I would not expect you to need dive planes.

Best,
Alec

On Mon, Dec 18, 2023 at 2:43 PM james hughes via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hello Gang,
> My sub is nearing completion after many years of work.  I based the design
> primarily on the K-250 blueprints I have but instead of having thrusters on
> the sides I have a 16 inch propeller under the aft ballast tank (linked to
> a 10 horsepower motor on the inside) and a 108 pound thrust trolling motor
> mounted under the forward ballast tank to help me turn port or starboard at
> low speeds.  My question is: Do I need to add dive planes in order to keep
> the thing level as I cruise along above the sea floor at about 2 to 3
> knots?  The boat is 25 feet long, 5 feet in diameter and will weigh in at
> about 8 tons (with about the bottom 12 inches of the sub filled with lead
> ingots).  Attached is an *old* picture to give you a visual of what it
> looks like (I'll post some new ones soon).  *Any* input would be very
> much appreciated  but I would really like to hear from anyone who has
> operated something like a K-350 using just the aft motor when submerged.  I
> don't mind making changes / additions at this point but really want to get
> this thing done and in the water so I'm hoping I can go without the need
> for dive planes.  Please let me know what you think!
>
> God bless and Merry Christmas to all!  Jim
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20231218/6412b4eb/attachment.html>