Frank, I agree that the roominess of the hull may far outweigh the minor issues that might be encountered on the surface. I know that you have put a lot of thought and effort into this boat and really want you to succeed. Didn’t get to talk to you much at the past Conference, wanted to discuss further the issue of moveable ballast. Kittredge and others felt that one of the major negative points to the WWII British Weldon submersibles was the moveable ballast (this sub supposedly influenced George in the design of a 1-man PSUB). Didn’t find anything else that covered this issue in any real depth until wrapping up the research for my recent presentation on the Seehund. Seems the Germans in designing their ill-conceived Biber 1-man subs, copied the Brits Weldon captured after aborted attacks on the Tirpitz in Norway. The Germans found that the screw-advanced moveable trim weight couldn’t react quick enough to trim issues and that could not be operated at all when experiencing up or down angles (the weight jammed against the screw threads). Hopefully you can engineer out these issues in some manner for your moveable mass. R/Jay From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of ShellyDalg@aol.com In a message dated 10/23/2009 7:30:44 P.M. Pacific Daylight Time, bottomgun@mindspring.com writes:
Hi Jay. Skepticism is a VERY good thing. I agree there aren't many saucer shaped subs out there. I think some of the reasons may be that a saucer by itself isn't very stable. Nor is a full sphere stable. The shapes just don't travel through water well. There is however compelling reasons as it relates to pressure resistance. The biggest benefit (for me ) is the space inside. It really makes a big difference in the "feel" of the inside. The Aquarius sub we dove in......really nice.....but my sub is more comfortable. Now if I had that big dome window.......WOW! I'm pretty sure I have the stability problem solved. It's not as sleek as a tubular design, and I expect a little instability on the surface. Mostly side-to-side wobble. The scale model tests that I ran showed some flaws early on. My friend has one of those "swimming" pools that have a big pump making the water flow so you can swim laps without moving. I used it for flow testing with many modifications to fairing design, ballast tank shape and placement, dive plane size and location, etc. That's the reason I have that big "fin" on the back. The models as they progressed were weighted and balanced just as close to the full size as possible. By adding the big "fin" I eliminated the "wobble" that was driving me nuts. I had the model set for neutral buoyancy and tied it with a string in the water flow. We used many different "speeds" by adjusting the pump speed and it tracks real straight. Now remember, that's tied with a string which really equates more to being towed than moving under it's own power. We took it up to over 40 knots......still tracked straight. On the surface, it wobbles a bit side-to-side. The only way to change that is with saddle tanks. Still, with the large amount of lead ballast on center, I'm pretty sure it can't tip enough to get the hatch near the water even with 200 LBS hanging off one side. ( one man's weight standing on the dive plane.) Submerged, I tested the model with empty ballast tanks, held it underwater upside down, and let it go. It immediately rolled over before it floated up. I calculate that the surfaced water line will be 24 inches from the hatch. With the scale weight of the 200 pound man sitting on the dive plane, it tilted to about 18 degrees from level. Again, these are just models, so the "real deal" may be quite different. Front-to-back it's like a rock! I'm putting in a sliding weight under the floor to adjust balance because the rear bolt-on section ( frame, ballast tank, motors, rudders, scuba tank and finned fairing ) weigh more than the front bolt-on section. The rear ballast tank is larger to "float" the extra weight but submerged I'll need to add weight to the front so it balances. AS I said, the saucer shape is very roomy, and all the stuff inside is real easy to get at. I just hope I can get it to float level. Frank D. |