DAN HRYHORCOFF’S “PERSISTENCE”

Captain George Kitteredge (retired U.S. Navy sub commander) designed the K-250 and K-350 submersibles that many have built from plans in their own home shops. Dan Hryhorcoff’s K-350, PERSISTENCE, is a good example of this type of submarine. Dan incorporated numerous modifications to the design to produce this hybrid appropriately dubbed a KH-350. The boat is named PERSISTENCE, because that’s what it took to build it.

The submarine PERSISTENCE on its transport and launching trailer.

A K-350 begins with several basic parts: the main cylinder for the hull, tower, battery pods, and so on. Here are the major components of Dan’s sub, fresh from the metal fab shop.

This is Dan welding one of the two battery pods.

Here, the reinforcing ring is being fitted to the hull.  This heavy steel ring is an important reinforcement in a critical area. 

After the conning tower is completely welded the hatch ring needs to be machined flat to get a good seal when the hatch cover is mated to it.  This lathe is very old but does the job.

Machining the main viewport flange.

Here you can see the set of rollers Dan used for rotating the hull so most welds can be made in the horizontal position.   This was the final welding of the hull structure.  Only the end of the hull was left open to make it easier to put in plumbing and wiring. 

Here’s a shot of the sub in the shop about the time Dan was working on the front ballast tank assembly.

The K-350 calls for fiberglass main ballast tanks. Dan took his a step further by designing his own tank shape with an adaptation for a headlamp assembly. Here are the various parts that go into making one: the plug, the mold, and the finished casting.

In this picture, we see Dan’s pretty much got it all together.

Here’s another view of the sub under construction in Dan’s shop.

Casting lead drop-weights.

The view inside PERSISTENCE, facing forward. The circle in the center is the front main viewport; alongside that are the rudder pedals; and other components radiate out from there. The light area above with the microphone is the inside of the conning tower.

Facing aft, we see the twin SCUBA tanks (used to power the ballast system) astride a stack of lead ballast blocks that bring the vessel to the proper diving weight.

Looking inside one of PERSISTENCE’s two external battery pods, with the cover removed. The gray and red object to the lower left of the battery pod is a drop weight (not yet hung in place). The round red object is the Variable Ballast Tank, or VBT.

For you techs out there: here's a simple way of connecting / disconnecting electrical power, and the receptacles double as the battery charging ports.

A close-up detail of the inside portion of a through-hull wiring connector from the battery pod, with it’s white protective cover removed. The wiring runs alongside one of the internal T-bar hull reinforcements, and stays out of the way. The open hole in the foreground is one of two battery pod vents in each pod. They are capped during diving.

This is a view of the port and starboard thruster relay panel.

The forward main viewport, as seen from under the front ballast tank. Notice the three spotlights situated around the port.

A stern view reveals the main propulsion thruster and bellcrank assembly below the aft ballast tank.

Launch Day has arrived! The launching was in a Northeastern Pennsylvania lake, near Dan’s home. Posing for this picture is Captain Dan (topside) with his crew (in yellow event T-shirts) standing by.  Also, there are many of the friends and family that supported Dan through his three and a half year project.  Look at all that yellow!

Before taking to the deep for the first time, Dan pours some bubbly on the bow while christening his sub "Persistence." 

To launch the submarine, Dan uses a 19-foot steel interconnector between the truck and trailer to get the boat deep enough on the ramp to float, while still keeping the launch vehicle dry.

PERSISTENCE underway. Not trying to emulate the Beatle’s song, Yellow Submarine, but many small subs are painted yellow for the practical reason that this is the most visible color, and when you are operating something that sits this low in the water, you definitely want to be seen by other boat traffic.

A scene from inside PERSISTENCE looking upwards shows Dan at the controls of his KH-350.

This is the view Dan has looking through the forward conning tower viewport. Cruising the surface, it's easy to tell where he's going; but when submerged, the compass is the best way to keep on course.

PERSISTANCE underway during a shallow manned submergence test.

Dan checking his heading through the front tower viewport.

Lights on to compensate for the murk.

The large main viewport provides an excellent view of the underwater environment. The sub is rigged to be controlled from either the conning tower or the main viewport.

With safety diver Al Secor in the water, Dan begins preparing PERSISTENCE for the unmanned deep water test.

Towing PERSISTENCE out to the deep water test site.

In deep water, Al assists Dan while installing the external locking mechanism on the main hatch.

Rigging the tether to PERSISTENCE for the unmanned deep water test.

Dan rigs the remote drop-weight mechanism that will return the sub to the surface at the end of the test.

PERSISTENCE returns to the surface after a one-hour stay at a depth of 540 FSW. The KH-350, designed to operate at 350 FSW, has proven its ability to survive at much greater depths: a necessary test before manned operations at or near the design operating depth can be safely performed.

Dan Hryhorcoff aboard his submarine PERSISTENCE.

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