Please see below From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of JimToddPsub@aol.com Gentlemen: A. When you are on the surface and ready for your ballast tanks to fill, what fill rate in gallons/liters per minute are you designing for or experiencing? In general, how long does it take for your tanks to fill to the level you want for initial dive? AS: I didn’t design this, I just started with the standard K250 design and flood valves. They were not full port valves, and the opening was only ¼”. They worked, but were sloooooow, probably a minute or so to flood MBT. I increased to half inch valves, and it sped up somewhat but still not as much as I’d like. So on the new saddle tanks, I’ve gone to 1” tubing and valves. That’s because I’m now riding a bubble in the saddle tanks, and want the ability to vent that bubble fast when its expanding during ascent. We’ll see tomorrow whether 1” is appropriate. B. How are you determining when you have reached any given percentage of fill? Are you aiming for neutral buoyancy, slightly negative, or even slightly positive? If so, how much? AS: I’m aiming for neutral buoyancy, and the way you know you’re there is by the waterline. When the surface touches the apex of a K250 dome, you shut off the valves. This is also a reason for the tiny viewports on the top of a steel hatch, they’re not just for looking out of but for knowing when to stop flooding your tanks. C. When you are submerged and ready to blow your tanks in order to surface, what blow rate in gallons/liters per minute (of water) are you designing for or experiencing at a given depth? AS: Again, I didn’t calculate this. The standard K250 had 3/8” tubing running 175 psi. It was more than enough, you could blow the tanks in a few seconds. When I went with HP, I reduced the tubing to ¼”, and you can still blow just as fast if, if not faster. Thanks, Jim |