[PSUBS-MAILIST] Hydrodynamic question

[james hughes via Personal_Submersibles]

 Thank you Alec for that reply!  I have a bit more hope now that I can do without those dive planes.  I should have also mentioned that I will be adding two trim tanks that should hold about 45 pounds of water each (for "fine tuning" the trim).
God bless, Jim
     On Monday, December 18, 2023 at 12:05:21 PM PST, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 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

_______________________________________________
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/20231218/58026825/attachment.html>