The Homebuilt Submarine

By Ron Wanttaja (

This is a photo of me with the sub, taken around spring 1976.  Everything painted orange or yellow is part of the sub (with the exception of the fireplug in the foreground, of course :-).  The yellow box contains the battery, the skids are 4x4s, the trusswork is welded steel tube, and one of the white trolling motors used for propulsion can be seen next to the black-painted aft stabilizer.   The long tube running horizontally just under the hull connected the joysticks in the two cockpits.  The "Notch" on top of the hull between the cockpits carried the scuba tank used for blowing the ballast tanks.  The forward dive plane can be seen (edge-on) in front of my right hand.

Before I start this story, I should mention that the title isn't a play on words. This isn't a tale about a float-equipped homebuilt that takes the "Z minus 1000" route.

It's the story how, for one summer, I was the skipper of the only submarine in North Dakota.

I realize the subject matter is a bit of a reach for rec.aviation.homebuilt. There's a lot of aviation in this story...and a few lessons, I hope, for the airplane builders in this forum. This is the story of two pilots who literally get out of their depth...trying to base the design of a submarine using only their knowledge of aeronautics.

The story starts over twenty years ago, in a Civil Air Patrol cadet squadron in Fargo, North Dakota. Our commander, who I'll refer to as the Major, made life in the squadron...umm, "interesting." We were the top squadron in the wing, a position we held for the last five years I was with the unit.

The squadron stayed on top by offering a wide variety of unusual activities...only a few which had anything directly to do with the mission of Civil Air Patrol. These activities tracked the interests of the Major. The Major gets interested in target shooting...and the squadron soon has an NRA-affiliated rifle team. The Major wants to learn to scuba dive...and the squadron soon is taking lessons at the YMCA. The Major wants to learn martial arts...and soon we've got a karate instructor teaching us how to break boards (ouch!). The Major wants to water ski...and the squadron soon has an 18-foot speedboat with a big herking motor.

It wasn't as selfish as it sounds. The Major was a born salesman; the kind of guy who can talk anyone out of anything. When equipment or instructors were necessary, he either talked the owner into a donation or paid for it himself. For the rifle team, for instance, he discovered a little-known civilian marksmanship program run by the US Army, and was able to get free ammunition and rifles. He got his fun...but the whole squadron, forty kids, got to join in as well.

The submarine grew out of the Scuba phase, of course. We had about fifteen cadets take the course. The Major wasn't especially physically fit, and having a batch of youngsters outswimming him was hard on his ego. He found the plans for a hand-held Scuba tow in Popular Mechanics. He built a pair of them and it apparently got his mind working on higher things.

Otherwise, I don't know quite how he got the urge to build a submarine. Inspiration probably struck when he stopped by the local Air National Guard squadron on one his occasional "What do you have that I can talk you out of" visits.

The Major struck pay dirt. The next time I visited his home, I found him cutting a pair of cockpits into a T-33 tip tank. The Sea Wasp project was underway.

The basic concept was a tandem open-cockpit two-seater, where the occupants would wear full scuba gear. Two electric trolling motors were installed in the rear. Switches installed in the exterior of the tank in front of the forward cockpit ran the motors individually forward and back. Waterproofing came from tube after tube of silicon RTV.

The tip tank included baffles in the extreme front and rear. These became the sub's ballast tanks. A set of valves (with garden-hose handles) in the "instrument panel" sent compressed air into or allowed air out either tank. Compressed air was provided by a small Scuba tank located between the two cockpits, using the first stage of a two-stage Scuba regulator to limit pressure to 150 PSI. There was an indentation in the jet fuel tank where the wing stuck in; this indentation provided a perfect cradle for the Scuba tank. The cockpit were cut so this notch would be on top. The tank sat between the two cockpits.

The tip-tank was mounted atop a cradle of steel tubes, with a pair of 4x4 wood skids at the bottom. Skid installation was similar to the way a pair of floats are installed on aircraft. The tank itself sat about three feet above the ground. On the cross-braces on the bottom rested a fiberglassed wooden box holding the 12-volt bus battery that powered the motors. The low position of the battery ensured that the center of lift (buoyancy) was always above the CG.

The Major wanted to "fly" the sub like he did the CAP Arrow, so the cockpits got dead-stock joysticks. Instead of using conventional controls, though, he came up with a dead-simple system. The joystick in the forward cockpit ran out the bottom of the fuselage, where a flat plexiglass vane was installed. The joystick was pivoted a foot or so above the vane. When the stick was tilted back, the vane tilted as well. Move the stick to the side, and the vane tilted. There was no linkages...the vane merely mounted directly to the bottom of the joystick tube.

The Major managed to get just about everything donated...the tip tank, the motors, and the battery. He eventually talked a local auto shop into painting the thing...bright orange, yellow trim, with "Sea Wasp I" painted below the front cockpit and a big CAP decal on the nose.

As you might expect, a T-33 tip tank, two electric motors, and lead-acid bus battery makes a pretty heavy load. The Sea Wasp's draft was about four feet, which leaves out using ordinary boat ramps.

That's where having a CAP squadron comes in. By organizing scuba weekends, the Major could be assured of ten to twenty husky farm-country teenagers to haul the thing into and out of the water.

Anyway, the Sea Wasp was ready for its water trials. One drawback of North Dakota, of course, is the scarcity of open water...especially deeper water. Fargo, though, is right on the border with Minnesota (the "Land of 10,000 Lakes," if you believe the license plates). Many people in Eastern North Dakota own small lake cottages, and the Major talked someone into the use of a rather nice place.

Which brought up one weird bit of trivia: Although it was a North Dakota sub, the Sea Wasp never made a dive in its home state....

When taken into the water, one problem immediately arose. Or, to be more specific, DIDN'T arise: The Sea Wasp didn't have enough buoyancy. Released, it sank, even with the ballast tanks blown dry.

The Major was ready for that. He had brought sheets of styrofoam. These were cut out, curved, and glued to the inside of the hull.

With that, the Sea Wasp could be dived and surfaced. The motors drove it fairly fast, fast enough that the occupant's face masks would get ripped off if they turned their heads to the side.

Unfortunately, it couldn't be controlled worth a durn. The Major's steering vane had very little effect.

I watched a good example. I watched the sub skimming along on a slow descent. It approached a rise in the muddy bottom. The vane tilted back, with negligible results. The lower skids hit the rise. The front dipped, the stern rose. The occupants windmilled their arms in slow motion, trying to keep themselves from floating free of their cockpits while a huge muddy "smoke cloud" slowly expanded from the crash site.

A later test run yielded another big surprise. The Major had the sub in deeper water. He descended to about 35 feet.

Then a huge cloud of bubbles erupted from the cockpits, and the sub dived for the bottom. Both occupants bailed out.

What had happened? Well, remember the styrofoam the Major added? It had collapsed under the water pressure, forcing out all the trapped air.

They swam down, tied a rope to one of the struts, and hauled the sub ashore. The Major fixed the buoyancy problem and took the sub to the lakes a couple of times for more tests. But by the end of the summer, he'd managed to get the ski boat donated to the squadron and his attention was drawn away from the troublesome sub.

I'd been watching the events, and had my own ideas on how to fix the controls. I got permission to take over the submarine project.

I knew the control vane had to go. I replaced it with a pair of large dive planes mounted just forward of the cockpit...a canard, in other words. A steel tube running crosswise, with the planes themselves being pieces of plexiglass about 3 feet long and 2 feet in chord. I mounted the planes at about the 33% point of the chord.

How did I pick the 33% point? It looked cool. It's not like I knew what I was doing. It's tough to find submarine design assistance in North Dakota.

The linkages to the control stick consisted of a simple pushrod connected from the stick to a bellcrank on the canard's tube. Too simple and too light, as I soon found out.

Testing had shown the low CG gave the sub scads of roll stability, so I didn't worry about ailerons. The Major said the motor controls were sufficient for yaw...conventional DPDT switches had been entombed in RTV, and going forward on one motor and astern on the other gave a reasonable turn radius.

Finally, I added a pair of horizontal stabilizers. These were attached to the support rods for the motors, and were about two feet long and a foot wide.

Time to try it. It was my last summer in North Dakota; I had to fit a lake trip in between summer school and work.

One of the cadets volunteered to be my backseater. Fitz had two primary qualifications: He was sixteen, and hence believed himself immortal, and he was a cadet second lieutenant, and hence expendable.

Fitz's prior claim to fame was the Three-Mile Moon. On a CAP field trip, we'd had two buses. Fitz had ridden on the front bus, driven by the Major. I rode the second bus, driven by our Wing's Air Force Liaison Officer, a crusty old Lieutenant Colonel whose past assignments included flying unmarked AT-28s in Southeast Asia. The front bus had been extensively modified by the Major, and unfortunately included a large table just forward of the rear window, with a curtain across the bus unfortunately just forward of that.

I'd been chatting with the LO as we traveled along a quiet highway, when *it* appeared in the back window of the Squadron bus. Fitz's stern, to be exact, shining pinkly behind the dirty glass. He'd eased the curtain closed so the Major couldn't see him in the mirror, laid down on the table, and dropped trou.

It was an interesting performance. Fitz didn't believe in static displays. The full moon rose, set, crawled left, oozed right, bobbed and shook. We in the second bus roared as the show went on for minutes.

The Major *knew* something was going on, from the stifled laugher from Fitz's friends behind the curtain. No one answered his roars for information, and he eventually stopped the bus. This process took a finite amount of time, of course...enough for Fitz to resume an innocent seat and expression by the time the Major stormed through the curtain. The Major stomped back to our bus to ask us what had been going on.

"Ummm," I said. I was still a cadet myself at that time, and didn't want to turn Fitz in.

"Hell, Dave," said the LO. "All I saw was a fat old man with a cee-gar."

The Major didn't think to take "prints" from the inside of the window. It would have made for an interesting lineup.

Anyway, Fitz escaped punishment, but the Major never invited him to ride the back seat of the sub. He got his chance with me.

So with Fitz in the rear seat of the Sea Wasp, I motored the sub toward deep water. The sub was uncomfortable to ride in. The cockpits were set up for sitting at nearly a right-angle, which is really only comfortable when in full gravity. In the water, as in space, one's body wants to assume a "dead-man's float" attitude. That, combined with the resistance to bending of the wet suits we had to wear, made it hard to stay on the seat. One's hips kept floating upward, and one had to use the "sit-up" muscles continually to kept an erect attitude.

Plus, of course, the wet suits gave our bodies positive buoyancy. We wore our usual diving weight belts, which gave our bodies neutral buoyancy. Heavier belts would have kept us in the seat better, but our legs would have still kept trying to float up.

Far enough from the shore, I shut the motors down. "Get on your air, Fitz," I warned my backseater. I turned the valves to let the air out of the fore and aft ballast tanks. Water closed over my head, and I flipped both motor switches forward.

The Sea Wasp moved out. I shoved the stick forward to dive further...and the pushrod buckled. I'd hinged the thing at about the 1/3rd chord point by eyeball. With the water pressure, there still wasn't enough balance to relieve the pressure and allow my (admittedly flimsy) control system to work.

I switched to the manual backup mode...I reached out of the cockpit with my right hand and grabbed the trailing edge of the canard. Try THAT in your Long-EZ.

I held it steady, as we seemed to be moving along a few feet below the surface. The dappled bright surface flickered overhead, and the current fluttered on my face and mask.

I zipped along for a minute or so, then blew the ballast tanks and shoved down on the trailing edge. We bobbed to the surface.

I dropped my scuba mouthpiece. "How was that, Fitz?"

He spat out his own mouthpiece. "How was what? The back end stayed up, I didn't go under."

Hmmm. The sub had tilted enough to put me under, but the stern apparently kept its bubble and left Fitz on the surface.

Try it again. Open the vents and *leave* them open. We dropped. I lifted the trailing edge of the canard, and the nose dropped. Speed increased. It got darker. The nose continued to pitch down. I shoved down on the canard's trailing edge. No effect.

I reached into the cockpit and shot compressed air to both the fore and aft ballast tanks...and discovered the Sea Wasp's worst design flaw.

You see, the ballast tanks were vented wrong. The tanks were built into the extreme ends of the converted tip tank. That gave them an approximately triangular cross section. Here's the general configuration of the fore and aft ballast tanks.

Anyway, the compressed air and cockpit-controlled venting for the tank led in at the top of each tank. There was a hole in the tank down low", this is where water exited the tank when air was blown into the tank and entered when the tank vents were open.

Now, take the above drawing and tilt it 45 degrees clockwise. Note that the tank opening effectively *rises* above most of the rest of the tank. When I tried to blow the forward tank with the nose down, the water would get shoved out of the tank until the air reached the hole at "B"... and it couldn't empty any more because the air would escape out the hole. And in the stern, the same problem existed in reverse... when trying to vent from the top hole, the water line would rise to the vent position, and a big bubble would be trapped in the back.

I realized there was a problem early, since forward tank's hole was at the bottom of the ballast tank inside the cockpit, and I could see the air bubbling out of the lower hole. I even put my foot over the hole, trying to stop it.

To no avail. We kept going down. I threw both motor switches in reverse.

With a surprisingly gentle thud, we hit the bottom. The stern dropped to the level position, and suddenly the tanks worked properly. The compressed air purged the water from the forward tank. The air bubble started to leave the stern tank. But of course, since the front tank was being purged using 150 PSI air, it emptied out much quicker.

The nose started to rise. I turned off the air to the forward tank and opened the vent.

Too late. We pitched up and headed for the surface, in a reverse of our plunge downward. We broached like the Seaview on chili night.

Alarmed by the lack of control, I shot air into both tanks to hold us on the surface.

"Hey, sir," called Fitz. "We got down to fifty feet." Fitz, with no controls and no way of asking me what was going on, had stuck with me the whole way.

Why we didn't both get embolisms and gawd knows what else, I'll never know. I'd had enough of trying to run that bucking bronco for a day...besides, with all the frantic vent blowing, I didn't know how much air I had left in the sub's tank. Back to shore for considerable head-scratching. We didn't have a spare small tank for the sub, so that was it for U-boating that weekend.

I took it out once or twice more that summer. By submerging carefully, slowly filling or venting both tanks, I could keep the thing level.

The trouble is, the canard didn't really work, either. The Major and I had both wanted an underwater "airplane". We weren't even close.

The summer ended with the Sea Wasp's problems still unsolved. I graduated from college that fall and entered the Air Force. The Sea Wasp sat abandoned under a tarp in the Major's yard.

If I'd had another winter to mull over the problem, I might have come up with a solution. Over the years, I've done a bit of thinking about how we might have achieved our goal.

The Major and I, in our goal to develop an underwater airplane, had forgot one major design attribute of airplanes: Wings.

I'd neared the solution with my addition of the small horizontal stabilizers. The canard didn't work, though, because pitching the sub up or down didn't increase or decrease the "lift" of the vehicle.

Take the sub moving along at 5 MPH. The canard commands nose-up. The thrust vector changes, giving a slight effect in the desired direction. But the only change in lift was the impact lift of the relative "water" against the rather narrow, round, belly of the tank.

If we'd had a pair of short, narrow-chord wings on the sides of the sub, I think we would have gained a lot of maneuverability. We needed some flat-plate area; a shape like a Stingray instead of a torpedo.

Alternatively, we could have gone with a more sub-like route by adding aft dive planes to go along with the forward ones. A set of large planes would have allowed us to change our depth without major changes in attitude.

Either way, the ballast tank system would have had to change. Adding a ballast tank at the CG of the sub would have been the best overall solution, eliminating the odd trim effects of the tanks in the extreme ends of the sub. A center ballast tank would have been simple to add, although it might have cramped the rear-seater's leg room.

Finally, speaking of leg room, the personnel accommodations could have been improved to allow more comfortable seating. Seat belts would have locked our bodies into the proper positions; however, I would have had a lot of misgivings over essentially tying myself into the vehicle. It was fun to play with, and we could ignore the danger by rationalizing that "ejecting" was easy...just a spring of the legs and we'd float away.

Still, it's probably fortunate that the Sea Wasp was abandoned after just two summers. Fitz and I were lucky to have avoided problems in our uncontrolled plummet and rise. About the only thing in our favor is that we spend next to no time at the lower depths, thus avoiding the bends. We didn't know what we were doing; a situation fraught with danger in both Scuba diving AND aviation.

But at the time...geeze, it was fun....

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