[PSUBS-MAILIST] Dive report

Tue Jun 14 18:05:36 EDT 2016

Hank,am wondering if the instability has anything to do with the changein metacentric height.http://maritime.org/doc/fleetsub/chap5.htm   It is possible to design a ballast system where you are stable onthe surface & stable under the water, but during the transitions thecenter of buoyancy goes below the center of gravity & leaves the subvulnerable to flipping upside down.   It could be that at this point of transition if the center of buoyancy &center of gravity come close, then any slight weight imbalance from oneside to the other of the centerline of the sub is magnified. You could always use your vertical thrusters to help control things inthe mean time.Cheers Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Wednesday, June 15, 2016 8:20 AM
 Subject: [PSUBS-MAILIST] Dive report

First time ever ( I think)  that I was able to dive on the first test trip.  I had to pull the sub out of the water onto the ramp to remove my new  weight from the front.  Then add 4 big rocks from shore in the back end, and off I went.    The Perry thrusters work okay but one is making noise in reverse, it is the one that has the original spring seal.  I will put the new cartridge seal in it now.   Amazingly they only draw 14 amps at full speed and that is for both, maybe my amp meter is wrong.  The sub is very slow to react to coarse correction, when travelling strait ahead I can stop one motor and it keeps going strait for a long way, I have to reverse one motor while underway to turn.  I should have mounted them in the back on an angle, I did testing last year and the worked well.  Having them strait is less responsive.  When I launch the sub it sits nice and level and higher as expected, the sub is very stable.  BUTTTT  when I start to dive the sub lists bad to one side, once I am submerged it is fine and I can cruise around like always.  When I surface the sub has a bad list again????  I have to get out and shift my weight to the high side and wait for the sub to level out.  Once level it stays level and is stable again.  Weird!!!    I have a common vent for both front and common vent for both rear tanks.  I think the air is taking the path of least resistance to one side and when I surface the one side is high and the air spills out the bottom instead of filling the low side tanks.  I am not sure how to fix this easily, any ideas are welcome.  Worst case, I can add air lines to each side, yuk!  there has to be a simple fix.I guess lengthening the pipes under the tanks would help, the air would have to go deeper forcing it to the opposite side.I met some nice people and had a nice visit.  My trailer handles the weight okay but my truck feels it.  Might have to get a kick ASS truck like Tim has with a nice rattling diesel.  All and all a good first dive.Hank
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