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Thread: Skipjack update

  1. #1
    Join Date
    Jun 2007
    7 miles north of Phelan, CA

    Default Skipjack update

    Last month at the pond, I have issues.
    Put Skipjack in the water and went out on the surface.
    Was planning to come in close to shore to do a Static dive to test things.
    Well, on the way out at about 20 feet, I noticed the stern was dropping.
    Added power and brought the boat back in.
    Stopped near the shore and the stern when down.
    Recovered the boat and when I opened it up, there was lots of water in the cylinder.
    After getting home, I started looking in to this problem.
    Well, I think I found it.
    Before putting on the Schrader valve cap, I am suppose to turn on the ballast water pump and empty the ballast balloon completely.
    Then put the Schrader valve cap on.
    I did not do this.
    So, in the water when I turn the ballast pump on to empty the ballast balloon, the balloon deflated and created a negative pressure in the cylinder.
    This sucked water in past the propeller shaft.

    So, the problem was me not following the check list before launch.

    Now the boat has been on my kitchen table since then with the cylinder completely disassembled.
    Figured I would look for a water pump that produce more volume.
    3 minutes to dive is too long for me.

    Found a pump to try.
    Ordered it and waiting for it to arrive.

    I have been looking at my tech rack and I am thinking of building another one.
    When I built this one, I also made 2 other duplicates for another project to be started in the future.

    Anyway, I think I can move some things around, if the dimensions of the new pump are correct, and get more room in front of the tech rack.

    What I have now is a safety tank for the ballast balloon that sits over the battery pack.
    The tank looks like a C with the C opening facing down to slide the battery underneath.
    If I move things around, I think I can get the battery under the tech rack leaving the front half the cylinder complete empty.

    Today, I was in the shop and thought I would make a couple of bulkheads with O-ring grooves that I can slip in to the cylinder.
    I can make rods that will keep the 2 bulkheads a specific distance apart. (volume of ballast tank needed. About 430ml)
    This will eliminate the Safety tank completely.
    Making this section between the bulkheads the safety section.

    Here is a photo of the safety tank in the cylinder.
    The battery you see, fits under the tank.

    By replacing the tank with 2 bulkheads, I can make the section shorter by 1/2" to 3/4".
    Maybe up to 1".

    Depending on the size of the new water pump, I can mount it on the front end of the tech rack behind the ballast tank section.
    Or I can mount it in front of the ballast tank section and run 3 wires through the ballast tank section using the spacer rods.

    I will also move the power switch to the rear end cap leaving the space in front of the ballast section empty or just a water pump.

    Some may have noticed that my Skipjack, is my test boat.
    Make it work and then see if I can make changes to make it work better.

    So far, each up grade has improved the boats performance.
    SSBN 598 - blue/nuke trained IC/forward

  2. #2
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    Thought I would get photos before it get too far in to it.
    This is the original safety tank and parts.

    Here I have finished the 2 bulkheads with O-ring grooves and after test fitting, this is what I have.

    Here you can see the three small holes I drilled in to each bulkhead to allow the pressure to equalize in the full cylinder.

    After the water pump arrives, I will make a new inlet/outlet tube with plastic parts.
    The one in the photo is 1/8" brass and I think I will need at least 1/4" to handle the volume of the new pump.

    Won't know until I have the pump and do some bucket testing.

    There will be rods to hold the bulkheads in place so they do not move in or out with pressure.
    I think two 1/16" wheel collars at each bulkhead will do.
    3 rods, maybe 4.

    This will make them adjustable should I need more or less safety tank volume.
    SSBN 598 - blue/nuke trained IC/forward

  3. #3
    Join Date
    Apr 2006
    United States


    Nice, Ralph!!!


  4. #4
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    I had 2 issues I wanted to deal with.
    1. The water pump is too slow. (hoping new one is better)
    2. The safety tank split it's lower seam last time out.
    The safety tank vents in to the main cylinder through 6 small holes at the top of the tank to equalize inside pressure.
    If the balloon where to leak, the water would have to rise up to the top of the tank to get in to the rest of the cylinder.
    The tank was built to give me a place under the tank for the battery.
    I now see how to put the battery under the tech rack and I no longer will need the space under the safety tank.
    So, removing the safety tank and making 2 water tight bulkheads will make the safety section shorter giveng more room in the cylinder.

    I just checked on the new pump and it is still in transit. Delivery any time from Feb 10th to Feb 27.

    I think I am going to make space rods that will hold the bulkheads in place, adjustable.
    I want to have a have the boat about 1/4" above the design waterline and I want to be able to go slightly negative.
    Once I get this set, I can adjust the length of the safety tank to accomidate the ballast balloon without stressing it.
    Less work for the pump. (I hope)

    This should work but if it does not, I have a secondary backup plan.

    I have measured the piston system in my Engel's Akula II and it will fit in the SKipjack cylinder if it is a little shorter and I rearrange the tech rack equipment.
    The Akula piston is 750 ml and my Skipjack has been working on 415 ml.
    Engel's sells different volume pistons and they offer custom length pistons.

    I have also wondered if Engel sell just the motor and gear system for their piston.
    I could make my own piston to fit my main cylinder, which would shorten the length needed in the cylinder.

    All sorts of option. Yes, the Engel piston is expensive.....but I have spent enough for a piston system in modifications not to mention the time involved.
    A side note: since I built the Engel's Akula II, I have been putting my daily change in a tin cup.
    I have more than half the cost saved up already.

    The only reason I am going to try a new pump is because the pump is cheap. $8 delivered.
    I only need to move the parts I have around to make it work.
    The piston will require complete tech rack redesign and 2 limit switches and a double pole double through switch and another servo.
    If I want to control the motor proportionally then another ESC t replace the water pump esc.
    Or change the pump motor to brushless.

    Isn't this fun.!
    SSBN 598 - blue/nuke trained IC/forward

  5. #5
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    Still waiting on the motor.
    I checked the tracking and it says the pump is still at the shippers.
    Sent an e-mail to the seller and found out they are closed until Feb 24.

    I get it.
    They closed up and went to the Olympics.
    I would, if I could.

    Next gathering submarines is coming up. March 10th I think.

    Looks like I will not have the new pump in time.

    The Akula II is still on the bench with some sort of electronic issue I can not find.

    But...but, there is always a plan.
    The week before the gathering, I can modify 1 of the new bulkheads to accept the 1/8" through tube for the ballast balloon.
    This will allow me to use the existing pump which I have not removed from the electronics tray.
    I will need to modify the tray to get the battery under the tray.
    Looks like I can move 1 servo by raising it up 1/4" and the battery will slide under.
    Move the power switch to the back cylinder cap.
    There is room where I removed the 2 winch through hull seals.

    Then water test and re trim the boat.
    I think I can do that in a few days.

    I plan to go tot he gathering even if I do not have a running boat.
    I plan to take the Akula and see if I can get some help from anyone with electronics knowledge. (that is not me)
    Electric = yes, Electronics = no

    Building continues between windy days with lots of dust and cold days.
    Just keep putting off painting.
    But I am prepared for those days that start out without the wind.
    Got the deck clear coated on the LAMA.
    Currently sanding and taping off to paint the railings on the ALMA.
    Doing the inside railings first.
    My plan is to try and get 1 side done each day.
    This way, I can stand the hull up on it's side so I will be paint down on a flat surface.
    (note: I may even see if I can paint 1 outside rail at the same time.
    Hull on side, I will see if I can tape off and paint the lower insides rail and the top outside rail.
    Both being down and flat surfaces.

    Once I get that done, I can start installing all the little parts on the deck and railings.
    Cleats, deck eyes, belaying pins, winch handles, fire axe and other small parts. (Standing rig attach points)
    During the windy days last week, I even made a couple of parts t make my one and only semi auto California compliant.
    Years ago, I bought this pistol to be California compliant at 12 rounds.
    Last year the people votes to make it 10 rounds with no grandfathering.

    I checked wit the manufacturer and found out they discontinued this model.
    I checked around for third party 10 round magazines.
    No Luck.

    So to keep this pistol, I need to make the magazines hold a maximum of 10 rounds.
    I have had a disassembled magazine between my keyboard and monitor for over a year.
    I have made several parts (3 maybe) and tested them in the magazine.
    I made changes.
    The part I ended up with is very simple to make and install.
    The law says something about making the change permanent.
    Which turns out to mean "not easily removed without tools and effort"

    Well, my part is installed with a very good glue.
    If I try to remove it by brute force the part breaks.
    To remove the part, I will have to use a Dremel grinding wheel and heat to get it all off.
    I tested the part on a separate steel plate, not the magazine.

    Now the good news is the law is being challenged in the courts.
    Not sure which way the judgement will go.
    But I have 2 parts which are currently in the magazines but not glues in place.
    The follower spring holds them in place and they work as needed.
    Once the law is settled, I can remove the parts for good or add a drop of glue and reassemble.

    And yes, I have a second option should the Department of Justice say my alteration is not be acceptable.
    Lengthen the top follower piece with a piece of brass flat bar drilled in and pins with bonder and shaped.

    Again, it can be removed with Dremel.
    My hope is to move to another state before any of this becomes necessary.
    But I have been saying that for 6 years now.

    I guess, I would be closer to moving if I didn't spend so much time building subs and sailboats. ;^)
    SSBN 598 - blue/nuke trained IC/forward

  6. #6
    Join Date
    Apr 2006
    United States



    Out of curiosity, will your pushrod & shaft seals not function properly under a slight vacuum? I am reading from what you wrote above that was the cause for the water incursion into your cylinder?


  7. #7
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    Matt, I have not yet tested the cylinder in water to see exactly where the water came from.
    I decided to change the water pump first and then look for the leaks.

    However, looking at the cylinder when I first got home, the end cap o-rings show full contact around the cap.
    If they leak it is where the o-ring contacts the cap.

    The new bellows where easier to check when I removed the cap.
    There was no water in the bellow folds. A good thing.

    I have not looked at the rubber boot that covers the power switch which is in the front end cap.
    I have had to replace the rubber boot twice before because it has cracked where the switch tightens up on the rubber shoulder.

    This leaves the balloon inlet/expel tube and the propeller shaft seal.
    I did not see water around the balloon tube at any of the connections.

    Once I get and change out the water pump, I plan to test the cylinder out of the boat and I plan to draw a negative pressure on the cylinder.

    My thoughts are the propeller shaft seal might be the place where water came in.

    I did not regrease the cup seal before running the boat.
    Got lazy.

    I usually empty the ballast balloon before screwing the Schrader valve cap on, to make sure there is not water in the balloon and to make sure the balloon can not be deflated any more.
    Then the only pressure I could create during the running would be positive pressure as the balloon is filled.
    Even draining the balloon would only go down to neutral pressure.

    The amount of water was about 4 ounces in the cylinder.
    The good news is all my electronics are on the top side of the tech rack which is about 1/3 up from the bottom of the cylinder.
    The water could be seen and it never reached the electronics until I tilted the boat lifting it out of the water.
    Everything works after letting it dry out for few days.
    Then I dissembled it all.
    I did check the ballast balloon by suing the pump to inflate the balloon with air.
    The balloon past this air test.
    So, from the pump to the balloon held up.

    As I get farther in to this overhaul, I will post what I find.
    I will post the changes I make.

    It could have been much worse.
    I could have lost my boat.

    Now. I have the opportunity to search out the problem(s) and share.
    SSBN 598 - blue/nuke trained IC/forward

  8. #8
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    Good news.
    Today, Monday is my day to go to town for lunch and groceries.
    Stopped by my mail box out by the highway.
    DO that once a week or so.
    Wrapped in the sales newspapers was my package with the new pump in it.

    Testing of this pump will start as soon as the weather stops messing around.
    Yesterday was 75 degrees. Today it is 39 degrees and 30 to 40 mph wind. (I looked at the gauge outside and it says 39. Not 45...okay, I am really cold now)

    I can now start measuring parts to re locate all my needed equipment on the tech rack.

    This pump is smaller than I thought it would be.
    The specs shows that this little pump will produce a volume of 1.3 liters/minute.
    We will see.
    Even if it produces only 1/2 of that, it will be twice that of the current pump.

    My main project right now is to get warm again after being outside for 45 minutes.
    SSBN 598 - blue/nuke trained IC/forward

  9. #9
    Join Date
    Jun 2007
    7 miles north of Phelan, CA


    Today, I worked on the Skipjack.
    My pan was to disconnect the rubber inlet/outlet tubes so I could remove the safety tank with the balloon inside.
    Required cutting 2 nylon zip ties.
    In a matter of seconds, the tank was disconnected.
    Next I would deflate the ballast balloon completely so it would pull through the opening in the end of the safety tank.

    Well, the balloon did not want to come out.
    Beings the clear plastic sheet around the tank was coming loose at the middle I decided to scrap the tank but try to keep the floor plate.
    Slowly peeled the clear plastic sheet off, exposing the ballast balloon.
    Pulled on the brass tube that goes inside the ballast balloon and noticed that the balloon would not move on the floor plate.

    Closer inspection revealed that the balloon was fixed in 2 places to the floor plate.
    My first thought was the balloon was wet from the last trip to the pond and had dried to the floor plate.
    Dripped some water on the floor plate and worked it under the balloon.
    Well, nothing happened.
    Next step is to pull on the balloon to see exactly where it was attached.
    So, blowing on the inlet tube, I inflated the balloon.
    Got the balloon to about 2" in diameter when I realized the balloon was not inflating any more.

    The inlet hose is about 14" long so I could blow in to the balloon and turn the safety tank floor over and around to look where the balloon was attached.
    This revealed that the balloon had come in to contact with the CA glue when I repaired a small 1/4" gap where the new clear plastic joined to the floor plate.
    The glue had fixed the gap but it also got on the balloon.
    The balloon was glued down in to the tight corner where the plastic cover met the floor plate.
    I could also see the the glue had burned a small hole in the ballast balloon.
    As I inflated the balloon the hole of course got bigger.
    Farther looking found a second place where the balloon was glued to the side of the safety tank.
    This did not have a hole burned through.

    The hole in the balloon would have let the full flow of the water pump run in to the safety tank which had come loose on the bottom seam.
    Almost 1 complete side of the safety tank had broken loose.
    So as water entered the safety tank, it drained straight in to the WTC and did not fill up the safety tank to the over flow holes where I could see the water in it.

    Running the water pump in the drain direction could not pick up the water as it was below the bottom of the safety tank floor plate.

    At this point, I think the ballast balloon hole was the cause of the flooding of my boat.
    I have checked the 3 new control rod boot seals and found no water int he boot folds.
    I still have to check the propeller shaft seal but I am thinking that for the amount of water in the WTC, the shaft seal could not have leaking that much that fast. (10 to 15 seconds)
    The new water pump(s) have arrived and I need to run tests on volume and whether when not running water passes the pump.
    If it does, then I will leave the roller pump in the boat for now.

    Next run is in 17 days.
    If I leave the roller pump and install the new bulkheads, I only need to relocate the battery, run the inlet/outlet tubing and re trim the boat.
    The Akula is still on the bench.
    Trouble shooting the electronic problem.
    Electrical, I can do, electronics has me scratching my head.
    Using a battery and jumper wires, I can get the ballast tank motor to run in both directions.
    When hooked to the electronics board, I can not get the correct setup light to come on.
    No power to the motor in either direction.

    Anyway, if I want a boat to run at the next gathering, it will have to be the Skipjack.
    SSBN 598 - blue/nuke trained IC/forward

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