economic submarine cruising

No long distance surface swimming animal exists because this is not energy efficient. Even whales that need surface for breathing (because they started as a surface animal similar to a nutria -ambulocetus-) swim now below surface - why ? because they cruise up to 12,000 miles each year and nature shapes all animals to be energy efficient. Here we are - if you are looking for a model for a energy efficient ocean crossing submarine yacht take this. A 200 ton whale with a length of 30m (cut some of the tail section for hydrodynamic efficient length - take some 25m) can come up to a speed of 30 knots and has been measured at those speeds. Biologists and Physiologists estimate its maximum power output at 400 horsepower. Whales are mammals so their energy physiology is similar to other mammals. Which means there is a big gap between the energy output you can get from the organism in a emergency situation for a few minutes of fast swim and the energy output you can get 24 hours a day. The most educated guess on that is a factor 10 you can run very fast for 1 minute but if you wander 24 hours a day you have to do it at a slower rithm. This means what you have on a whale tail 24 hours a day during wandering is maybe 40 horsepower possibly less. If you take into account that whales do not feed which means do not re-fuel 6-8 months during wandering - how is this possible ? - only if they use VERY VERY little energy for swimming over VERY VERY long distances. What is the efficient speed range ? Smaller whales cruise at some 3 knots bigger whales at up to 6 knots. Taking a stream speed of 3 knots in your favor as ben franklin did in its 30 day Golf Stream drift dive - you could have a whale economic ocean crossing at 9knots over ground in a submarine yacht - not bad ! Having this in mind i took my prototype concrete submarine to water back in 1996 it was whale shaped had 20 tons like a small whale and my most important question was not top speed with a big engine - this is quite clear anyhow - my question was the limbo - how low can you go... so what i did first was installing a ridiculously small electric engine of 200W into the sub and pushed the switch. - What happened? First nothing then after a couple of seconds the hull took up speed and kept taking up speed until it reached a speed of what would be in the range of a whale efficient cruising speed - some 3 knots. So i never came to the point to install the big combustion engine i had in mind in first place - it was not necessary. I later put a small generator in to reload the small battery pack and extend the range - that was all. In all my submarine yachting years i never saw a situation i would have had a need for a bigger engine. This ridiculously small engine pushed me trough storms had no problem to get nose into the wind... So i am well aware what engine size is recommended for surface yachts - BUT - based on my own experience i would be concerned that such a engine would have a short life in a yacht submarine yacht because it has to run all the time in under load during cruising . I also have no problem if somebody wants a 400hp engine in a 200 ton submarine yacht to run all the time at whale emergency speed of 30 knots - you could water ski behind it...
My personal preference is doing it like those gentle giants - cruise oceans energy efficient at moderate speed.

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