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  • Im42nut2

    Hi fellow submariners. I guess it's 'bout time I shared my project with y'all. Been reading this forum since I decided to tackle it. Thanks for a lot of advice I've used from many of you.

    A little background:
    I was on the Nathan Hale (SSBN623) blue crew from Oct. '75 to July '78. Did 5 patrols (2 out of Charleston, SC and 3 out of Holy Loch, Scot.). We had to do a SPALT to 4 missle tubes that were carrying Goodyear missles during my fourth patrol. (No problem with the Uniroyal missles, but the Goodyears were blowing up in flight the exact same way the Challenger exploded...deteriorated second stage motor seals.)

    I was an FTB, was the roving troubleshooter during countdowns, and got to pull the trigger on one of the missles to shoot it. WEPS shot the first and last, Supv. shot the second, and I did the third. (Had to test to make sure all tubes worked after the SPALT.) Many boats had to do this. If any of y'all was on during this op, I'm sure you remember the sound and the great feeling of the sub the moment the missle an elevator bottoming out.

    Angles and dangles, hump night, trim parties, POKER...fond memories. But a couple of scary ones too. Was in upper level Missle compartment reaching test depth during sea trials...the metal creaking got so loud I RAN to the control room. And the rack is no place to be when blowing from test depth. The turbulence of the sub was so violent it felt like the sub was moving so fast it was going to fly up out of the water, roll over, and come crashing back to the surface. lol. I quickly jumped out of the rack and on my feet. It felt great then. It was surprising the difference between laying prone vice standing.

    The project I'm building is a submarine that will submerge to 200 feet, take live video and send it to my laptop on the surface. It's approx. 10 ft long and 12 in. diam....made from 12 in. sch. 40 PVC pipe...fiberglassed and painted when I'm done.

    Actually this is the second time I'm building it. I tried housing it all in a 5 foot, 12 inch sch. 40 PVC pipe first. The size of the electronics WTC had to be so small I rewired 7...count 'em...7 times before I could squeeze it all in enough to screw on the end cap. There were 72 connectors which I heat shrinked, cut off, re-heat shrinked...etc. 7 times because I was afraid my pushing on them would pull some of them apart...even in the long sub I used all 4mm connectors and heat shrunk them all...over 100 including those outside the WTCs.

    Also in the short sub the servo control arms had to be bent to get them by the aft DCT (which had to be installed first), rebent into shape behind and underneath it, working through a 3 inch gap that housed a battery. Also I only could fit in a one gal. air tank. Could only fit in 4 inch diameter DCTs...6 inchers in this one.

    I'm sort of a backyard mechanic and everything I build is from scratch. Some things in the sub I've welded. Some things braised, some things soldered, some things epoxyed, some things glued, some things bolted, some things screwed, some things tie-wrapped.

    The sail is an 8 in. piece of the tubing, warmed in an oven, and stretched into a teardrop shape. Same with the planes and rudder, but made from 4 in. PVC tubing. (I found couplers don't come out right...the center ring has to be cut out or it will bulge outward.) All metal surfaces are either stainless steel or primed and painted.

    For the nose dome, I bought a rubber kick ball and blew it up to the size it fit snugly in the end and fiberglassed a dome onto it. Outside the dome I mounted a 133 watt boatplug light under a camera which is inside the dome (looking out, of course) in its own WTC...there are 5, main electronics, engine compartment, and 2 individual dump solenoids in the sail (one is head valve, second is for DCTs...2 DCTs tied just behind the bow, the other just in front of the engine comp....designed to eliminate porpoising as read about in this forum).
    For the anti-porpoising I put a 3 gpm sump pump in each DCT, which their outputs will be properly metered to the other DCT for leveling. The leveling sensor is an inch and a half PVC tube curved slightly upward on both ends from the middle, with a steel ball sitting in the center of it. One inch from the ball on each end is an inductive probe/switch. Each probe picks up a relay, which in turn, runs the appropriate pump. Proper metering must be done to allow it to level off the sub and not overcompensate due to there is no proportional control.

    I'm using a 5 gal. 150psi air tank for ballast and depth control. The tank is mounted right behind the front DCT. My home compressor will pump to 120psi so I'm limited to that amount for this sub. (If I do another, I'll put a SCUBA tank and regulator in it.) Air will pass through a solenoid valve in the electronics WTC to the common line into both DCTs by use of the left joystick on my controller, pushing it to the right. (Pushing the stick to the left opens the dump DCT solenoid in the sail.) (The right stick controls the rudder and stern planes.) (The 5?...controls the sail planes.)

    The DCTs have a 1 in. hole in the bottom for exhaust and ingress. (I routed the DCTs sump pump electrical lines out these holes too.) To emergency surface, due to limited devices I can control (7) with my controller, I just do a continuous blow throught the DCTs which, when empty, will start filling the sub with air...pushing its water out the bottom.

    Right now I have a 50 lb. lead ballast bolted inside the bottom of the sub at the forward edge of the sail. I'll be taking it to the water (swimming pool) for the first time next weekend to find the proper weight and distribution I need to make the sub sink completely (with the head valve open) with just the sail sticking out of the water. It'll have to displace about 450 lbs. of water. I figure the empty space in the sub will hold 25 gal. of water and so I'll have to add another 25 to 50 lbs. By heft I think it weighs around 200 lbs. already. I know I'll have to build a boat trailer for it.

    I sure hope the thing doesn't leak. I'm sure I've done a good job in all areas. But if it does leak, there is a bilge system built into the bottom of the electronics WTC, and all WTCs drain into it. A capacitive probe/switch senses when water gets within a quarter inch of it, it picks up a relay, which in turn, starts a pump which pumps it out into the sub. I originally bought a pump for this expecting to overcome outside pressures of up to 90 psi differential.

    But as engineering kept changing as I went along (trial and error seems like everything) I ended up using a differential air flow switch which senses both the inside and outside pressures and switches when it feels 1 inch of water column pressure. It then pops open a small solenoid, dumping system air inside the electronics WTC, which will immediately start pressurizing it and reset the switch, closing the solenoid. It'll continue that process with little spurts all the way down. With all WTCs tied together through the bilge system, all WTCs stay slightly above outside pressure. On the way to the surface, as water pressures outside the WTCs decrease, a 1 psi backflow check valve will contiuously dump the air pressure from the WTCs.

    For the planes and rudder I used motorcycle throttle cables...6 of them...2 for each because the cables won't push...have to pull from both sides. They seemed to work real easy but the servos I used which were deemed 'high torque' (spares I had for my 600 series helicopter) did not have the power. They were 90 in./oz. So I used those for the switches and bought 270 in./oz. ones for the rudder and planes. They work great.

    Aligning the engine drive shaft, the rudder, and the stern planes was a nightmare...expecially having to disassemble and reassemble so many times to complete other things. If all were perfect, all three would meet at the exact point. So because both the rudder and the main shaft have to be exactly centered, I mounted the rudder as two pieces (top rudder,bottom rudder). Each are double bearinged, come to a quarter of an inch from the main shaft, and coupled together and bearinged with a U type bracket. The stern planes are not sub centered. I left them as one axle slightly below the main shaft and behind the lower rudder axle.

    The engine is a chopped down helicopter. I bought a 540KV RC motor, main gear, main shaft, side frames and mounting hardware, cut grooves in a 6 in. sch 40 PVC pipe, cut the side frames down, and it slides in and out. The gearing ratio is approx. 10 to1. (If I do another sub, I'm going to directly couple the propeller shaft to the engine and use programming to limit rotational speed...any reason I should not try this???)

    I'm using two 12vdc batteries hooked in series for 24vdc to the ESC. (One of the batteries also runs the rest of the electronics, head light, and camera.) The shaft runs about 350 rpm max. I'm hoping it'll run the sub at 2 to 3 mph. It's a 75mm propeller which runs inside of a 4 in. PVC coupler extended about 3 in. from the aft of the sub.

    The ESC is 40 amp although I doubt it'll draw 5 to run that little prop...even though it is water. As I bought parts, I did not realize they made ESCs which reverse. So I'm using a switch on my controller which rotates a servo arm which activates a switch which energizes 2 SPDT relays, swapping 2 of the 3 leads to the motor.

    Because I believe the ESC will draw so little amperage, I did not do the cooling method I've seen by creating a large hole in the WTC for it...did not want to contend with sealing it in. I did that with the 5 footer, but decided against it in this longer one. The new electronics WTC is 8 inches longer than the other one and the ESC is caged alone by itself.

    Since the submarine has to be tethered for both control and video transmission, I built a floating device out of 2 in. PVC which will tether closely to the boat. The dual RG-6 cable (one line for control and the other for video) figure 8s onto 4 holders around the outside with a box housing a 6vdc battery, a 2.4 Ghz amplifier/converter (RF to cable), antenna, and connections for underwater cable and laptop.

    I added one more device as a precautionary element in case I lose power to the BEC...i.e. the 5A fuse blows (there are 5 individually fused circuits which protect everything...except this device). This is a relay that remains energized as long as there is 12vdc feeding the circuit with the BEC. The normally closed contacts route power directly from the battery to the air dump solenoid which feeds the DCTs. So if power is lost the submarine will emergency blow to the surface.

    Because of that emergency relay, I had to install a ball valve in the main air line feeding the electronics WTC. That ball valve must remain closed until the 'ON' push button in the sail is depressed, energizing the relay. Otherwise the air tank will dump its air.

    Each battery has its own extended battery posts in the sail for charging. Ditto for the Schraeder valve for the air tank.

    I'm retired now, but the owner of the pump and water supply company I used to work for is letting me use space in his 'barn' to build the sub. I'm going down now to remove some items and complete the priming of the inside surfaces. Tomorrow I'll paint. Monday put it all back together. Tuesday test everything again and start fiberglassing. Wednesday finish fiberglassing. Thursday prime the sub. Friday paint the sub. Saturday take it to the pool for weight/buoyancy testing....well, that may all take 2 weeks. I'm a patient man. I've got 5 guys lined up to help me manhandle this thing.

    I'll add pics (camera's at the sub) soon...if I can figure out how to get them here.

  • #2
    Im42nut2, Welcome aboard! Looking forward to seeing and hearing more from you.


    • #3
      Here it is 8 months and a lot of modifying later...and it's finally floating...3rd weight test. Sub went to the bottom the first 2. Replaced the 5 gallon,150 psi air tank with 2 small scuba tanks...3000 psi & 26 cu ft at sea level. The dome had to be sealed to (made part of) the sub. The manual air shut-off valve was replaced by a relay and toggle switch


      • #4
        The first dunking the sub got filled the electronics package with water which ruined all of the switches and relays...while stuffing it all in I had originally broken off the sense line sensing outside pressure. Not only did I have to remove the 50 lb. lead weight...I had to glue-in 450 ping pong balls to the inside top to make it buoyant. That allowed a needed keel of 35 lbs. due to it being top heavy with the equipment in the sail.


        • #5
          Now THAT... is a serious submarine!