Marlin Submarines S102: 1989-90

Following the Whiskey on the Rocks incident in 1981, the Swedish government became increasingly paranoid about being the primary Soviet breakout point from the Baltic and the Russians expended a great deal of effort surveying the defences in and around Karlskrona Naval base. The Royal Swedish navy had discovered how difficult it was to find and track the small submarine vehicles they were using so started looking for a suitable training target.

In 1986 one appeared, S101, brought to their attention due to a Perkins Diesel advertising journal that ended up on a Swedish FMV desk. After an extensive set of trials in Plymouth by the navy’s contract diving company DYKAB, they expressed the desire to purchase S101 provided it could be Lloyds classed. We realised that would be hard and far better to build a new one under Lloyds survey. The price of £120,000 was agreed which, surprisingly, made us a small profit.

The design differed from S101 having a slightly larger hull and more closely spaced but lighter frames. The battery was more than twice as big and 120V this time to run standard high power underwater lights. The main 7.5kW electric motor was specially made for us to run as a motor or as a generator to re-charge the battery.

Bow planes were fitted this time for accurate depth control as it had to operate using an optronics mast (camera on stick technology).  Navigation was a Brooks and Gatehouse system of compass and log with a dead reckoning function. GPS was not fully functioning till 1994 so this was considered a useful add-on. Later manufacturers of navigation systems did not bother with dead reckoning as they felt that if your GPS sensor becomes completely submerged you had more pressing problems than a good nav fix.

The diesel, Perkins again as we felt we owed them that much, was a 2-litre 50 hp 4-cylinder automotive unit. In hindsight one half that size would have been more than adequate. The diesel drove through a one-way clutch which disengaged as soon as the diesel stopped. The electric motor was permanently coupled through a fiendishly cunning automatic transmission running at one speed whilst driving and another speed when being driven.

The build period was tight (as always) having just 12 months to design, build and launch. This was to become a familiar pattern in the years to come. We set on a certified welder and a skilled machinist and started work making the pressure hull ourselves under Lloyds survey. The GRP was entrusted to Pollypressions who are still the number one choice for high quality GRP moulds and components. In the final weeks we were assisted by Hans and Lassa, the two Swedish submarine pilots. Time was very tight but we managed it with just a week left for dock trials. It was April 1990.

We had just 4 days in the water in Plymouth before S102 was loaded onto a truck to Stockholm. Hans and Lassa drove through the night and arrived with the sub around midday just 5 hours before the contract with the Royal Swedish Navy commenced. They had snatched a few hours’ sleep while taking it in turns to drive but now faced working through another night. The sub was launched but of course had to be re-ballasted for the fresh water of the Baltic leaving just a few hours for preparation and troubleshooting before the Navy arrived and the mission commenced.

The Mission

The Sub Crew were given a basic plan that they were to go from A to B to C to D but the route they took through hundreds of islands in the Swedish Archipelago was entirely up to them. Hans and Lassa had planned it in secret just after the truck left. It was S102 vs the Royal Swedish Navy.

This was to be a night mission of some 40 miles so a proportion had to be on the surface. Just to make it a bit harder, the weather was closing in and the sea state mounting. Throughout the night they suffered various failures but the sub had sufficient redundancy for the mission to continue. They ran their course as planned and the navy had not a clue where they went, emphasising the urgent need for this program. After de-brief Hans said he went to bed and slept for 24 hours.

Over the next 6 years Hans and Lassa continued to run rings round the navy. They used to make the mast camera look like a bit of floating grass and drive right past a destroyer in daylight. It is the most difficult thing to track a small submarine in those waters. Recently Hans and I were reflecting about those years. He said “you know Paul, that was such a good business decision, that sub paid for itself over and over” 

DYKAB sold S102 to a treasure hunter destined for the Philippines. We have tracked it down to its current resting place on the property of the Philippines politician Chavit Singson. From the pictures, it looks in good condition but it is sadly not operational.