Over thirty years ago I saw a static model of this obscure Kriegsmarine 'sprengboot' in Scale Ship Modeler Magazine
. The sprengboot were small craft filled with explosives and driven to within 1/4 mile of anchored Allied shipping, when the pilot bailed out and the boat was steered into the target by a radio control operator in a nearby support boat. The pilot was (eventually) retrieved by the support boat. The smaller Linse
boats had some success in damaging Allied shipping on the Dutch coast, but they were small, relatively slow and only carried 300 pounds of high explosive, limiting the damage they could cause.
The solution to the Linse
shortcomings was the Tornado
, built with parts relatively cheap and easy to find in wartime. Floats from a Junker-52 transport were connected with a wooden deck. The Tornado
was powered by the plentiful Argus pulse jet from the V-1 (some sources say it had two jets). The Tornado
carried over 1500 pounds of Amatol making it a formidable weapon. No photos of the Tornado
survive and reliable references are hard to find, but apparently only one prototype was ever built and tested. Some reports state it made 48 knots on smooth water and that plans were made to go to production. On the other hand some sources called it a noisy under-performer that was a dismal failure. Regardless, when the Allies over-ran the testing facility near PeenemÃ¼nde the single prototype was destroyed to keep it out of enemy hands.
I had wanted to build a working model of the Tornado
since I first saw that photo of the model 30+ years ago. I wanted to know how well the concept would work, how fast it would run and how stable it would be (I have about 50 hours in full-scale float planes so I knew that aircraft floats are not a rough water design) and I wondered - could it have worked for its intended purpose?
I used two floats intended for an R/C airplane, scrap 3/16" ply and PVC piping, and an airplane motor. I knew that any ducted fan would have to be too large in diameter and produce too little thrust for the intended SOS concept, but when running the Tornado
the prop is invisible and the tubing 'looks like' an Argus jet. I used scale aircraft float rudders for control.
The maiden voyage was a success, and the boat behaved surprisingly well, easily surpassing the scale speed of the original. I learned that I needed to apply power like the original would have and build up speed rather slowly. If I was too ambitious on the throttle the model would begin wildly hopping and skipping - not at all acceptable for a full-scale boat. As long as I applied balanced throttle like the Argus jet would have done (it had just 500 pounds of static thrust afterall) the boat climbed out of the water and ran well with good control and directional stability - vital for the full-scale Tornado's
intended purpose. 48 knots in 1/13 scale is about 15 mph, and my Tornado
was very happy at this speed (about 1/3 throttle). I could run up to a 100 mph scale speed, but the original would never have been able to go nearly that fast.
Running the model Tornado
is a blast and a bit of a challenge as well. I get plenty of run time and derive lots of satisfaction from running one of the few (or perhaps the only) R/C model of this interesting historical craft.
Comments and/or discussion are welcome.