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Kreigsmarine Explosive R/C boat

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Old 02-02-2013, 09:15 PM
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Default Kreigsmarine Explosive R/C boat

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 Peenemünde 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.




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Old 02-03-2013, 10:21 AM
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Default RE: Kreigsmarine Explosive R/C boat

That's a very interesting looking craft. I think you did a great job of building it.

Would like to see some video of it in operation.
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Old 02-03-2013, 02:49 PM
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Default RE: Kreigsmarine Explosive R/C boat

So would I. On the maiden voyage my buddy discovered that he had not charged his video camera. When I do get some video I will certainly post it!



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Old 02-07-2013, 05:26 AM
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Default RE: Kreigsmarine Explosive R/C boat

I should be able to post a video of my model this weekend, but in the mean time here is some vintage footage of other explosive boats. Sadly, none survive of the Tornado.

http://www.criticalpast.com/video/65...ed-on-trailers

http://www.criticalpast.com/video/65..._demonstration




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Old 02-10-2013, 01:54 PM
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Default RE: Kreigsmarine Explosive R/C boat

Finally got some video of the Tornado running on smooth water. The videos are short and not great as I shot them while driving the model. I propped down to slow the model, but after some adjustment of the CG it now runs stably at full throttle. I will prop back up later to see how the model handles a higher speed.

Right now the model's top speed is well over the original's scale speed of 48 knots. It is quite stable at scale speeds and even at almost twice scale speeds it is not in trouble. I can fully believe that the original Tornado may have performed as most sources noted, although clearly it is a smooth water only craft. I also wonder if it would have achieved 48 knots with a single Argus engine. Some sources state that the Tornado used two jets and given the low static thrust of the Argus engines at that time (500 pounds static) that makes more sense to me. Regardless my model proves that the basic idea was sound. Still, I would not like to have been the in-cockpit driver!





http://youtu.be/C65C7CPGcrc

http://youtu.be/QxzdlF5GPN0



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Old 02-10-2013, 10:03 PM
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Default RE: Kreigsmarine Explosive R/C boat

Well, you sure had it scootin' along pretty well there!
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Old 02-11-2013, 12:13 PM
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Default RE: Kreigsmarine Explosive R/C boat

Could u post motor kv atteries and prop size plz
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Old 02-11-2013, 01:26 PM
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Default RE: Kreigsmarine Explosive R/C boat

Sure.

Motor - Scorpion SII-3026/1190
Pack - Hyperion 4S1P/4200 mAh
Prop - ABC 8x4

The prop is plenty conservative, I propped down to reduce the model's speed while I tuned the CG. I will prop up to at least an ABC 9x4.5 (which I used in the initial testing) and perhaps to an ABC 9x6 if the hull will handle the speed. Remember this model was not built for top performance, but rather to prove a concept.



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