Building a Wet Sub: Lessons Learned the Hard Way

1
Building a Wet Sub Lessons Learned the Hard Way

• Doug Farrow
• SeaLordOne_at_aol.com
• [phone]

2
The Undaunted

• 16 foot, 750 pound two-man wet sub
• Fiber-glassed one-inch marine plywood
• Two rear-mounted trolling motors
• Two rudders and one hydroplane operated by levers
  and pulleys
• Double keels for grounding
• Two bilge pumps
• Standard scuba tank with regulator
• 10 Portholes

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Why the Undaunted?

• I asked for suggestions from friends and family
• My sister suggested Undaunted. Other
  suggestions included
• The Blue Canoe
• The Blue-Boat U-Boat
• The Plywood Coffin

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Reference Library

• Photocopies from various encyclopedias
• WW II submarine books
• Articles from Popular Mechanics and Popular
  Science
• The plans from the Markham Boat
• Two man wet sub featured in Popular Mechanics and
  built from drop tank

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Why 1971?

• I was in the Air Force 1969-1973
• I had just returned from Vietnam
• I had time on my hands
• I was single
• I was in Florida near water
• I had wanted to build a submarine since seeing
  Walt Disneys 20,000 Leagues in 1954

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Design Philosophy

• Make it sturdy
• Stay above 33 feet
• Use existing skill-sets
• Use commercial components
• Minimize costs
• Two person crew
• Comfortable on the surface

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Construction Venues

• Drawings and scale model in barracks
• Initial construction in buddys front yard
• Continued construction in womans back yard
  (backs to a lake)
• Component assembly in friends garage
• Testing in St. Petersburg
• Operations in Tampa Bay

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My Biggest Mistake

• I envisioned cruising out and back from the dive
  site sitting atop the conning tower, using the
  sub as a boat.
• Because of the instability caused by the flat
  bottom, I had to seal the hatch and flood down at
  the dock. It was very stable under water.

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Because of the Flat Bottom

• I could not use the anchor, the paddle or the
  jump seat on the conning tower
• I did not need the hydroplane, because the huge
  flat bottom acted as a hydroplane when I trimmed
  backward

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I Failed to Account For System Interactions

• The rudder and hydroplane levers worked great
• Adjusting trim by rolling my seat forwards and
  backwards worked great
• But when I went to push forward on the levers, my
  seat went backwards, and my nose pitched up
• Solution Installed a handle to hang onto

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Electrical System

• Knowing nothing about electricity, I simply
  copied the Markham parts list
• Grossly underpowered 3 times as heavy
• Markham said nothing about out-gassing during
  battery charging or discharging
• Mounted controls on upper surface of conning
  tower, prevented diver egress

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Steering System

• Dual rudder system controlled by pulleys worked
  surprisingly well
• Between the rudders and hydroplanes 30 pulley
  wheels
• Steering was fine, but navigation was not. I was
  so low in the water I could barely see.

13
Ballast System

• Moved from bricks to re-bar
• My conning tower was my ballast tank, and the
  hatch seal leaked constantly. I could not
  maintain depth

14
Two Person Crew

• No one would dive with me, so it became a one man
  boat
• Very scary all alone in the middle of Tampa Bay
• In the end, the range of motion required by my
  trim system would have prevented a second
  crewmember anyway

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What I Did Right

• I actually built a PSUB
• It may have been clumsy, but it sure was fun
• I learned more about submarine building from that
  than from all the books I read
• I never dived in water deeper than 30 feet

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What I Learned

• A PSUB is an integrated system. One major design
  flaw (e.g. flat bottom) ripples throughout the
  rest of the design.
• Solicit advice from people who know more, not
  less, than you do.
• Re-read the books you read when you were first
  learning the business.

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What I Learned

• Get a workshop.
• A submarine is a boat.
• Do not implement systems you do not understand.
• Negotiate your submersible activities with your
  significant other.
• Be sure you assistants do the same.

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Think Trough The Entire Lifecycle During Planning

• Analysis
• Capabilities, Constraints
• Design
• Paper, Computer, Mockup
• Construction
• Hull, Components

• Testing
• Hull, Components
• Operations
• Normal, Emergency
• Maintenance
• Routine, Repairs
• Upgrade
• Hull, Components
• Disposition

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Questions?

• There are no stupid questions, only stupid
  people (joke).