8 Jul 01 - Better pictures added.
The left most picture is the original i.c. powered model. The other pictures are after conversion.
|No. of launches / Time||5||24 mins||
|Overall Length||32½ "||0.82 m|
|Beam||16½ "||0.42 m|
|Weight||5 lb. 0¾ oz.||2.3 kg|
|Motor||Graupner Speed 600 Race 8.4V|
|Gearbox||Modelair-Tech H-500 with ratio of 2.4:1|
|Batteries||8 Sanyo RC-2000|
|Speed Controller||Gordon Tarling Micro-Star 40BEC/B - 6 to 10 cells, 40A, BEC & Brake|
|Propeller||APC 11" x 10"|
|Receiver||Hitec HFS-03MC - PPM - 3 channel - 40MHz|
|Servo||Rudder - Futaba FP-S148|
|Motor performance||MA Electric Wood propeller with 3.6:1
ratio - 3800 RPM @ propeller, drawing 24.5A @ 8.2V after 1
minute. Estimated thrust is 38 oz. (10.6N)
APC 11" x 10" propeller with 2.4:1 ratio - 6000 RPM @ propeller, drawing 31A @ 8.2V after 1 minute. Estimated thrust is 30 oz (8.3N)
|Performance||Quite good, but could really do with more speed. Despite that, however, I managed to flip it upside down.|
This is a tunnel catamaran boat powered by an aircraft engine sitting on the pylon. The steering is by a conventional rudder assembly on the transom. The model is is fitted with my MDS 40 and set-up with new 40 MHz radio system. Due to being unable to use the boat at the moment due to club regulations (no i.c. powered models) I have removed all the RC equipment for use in another model.
12 Jun 99 - I am considering putting an electric power system in this model to allow it's use at my current boat club. As my deliberations continue I'll put up more information.
13 Mar 00 - I finally got around to converting the model to electric power. I selected my favourite Speed 600 Race 8.4V motor, a Modelair-Tech H-500 gearbox running on 8 RC-2000 cells. To complete the package, a ratio of 3.6:1 was chosen using a Master Airscrew Electric Wood (MAEW) 13" x 10" propeller. This draws a similar current to the motor in my EXP-1r, which uses a direct drive 6" x 5" propeller. The weight increase due to the conversion was only 3¼ oz., with a weight shift to the stern. I don't foresee this as a problem, but trials will tell. This is the largest diameter of propeller I can fit in this layout, but I can always decrease the reduction ration in steps to 2.4:1. I will experiment with the 13" x 8", 12" x 10" and 12" x 8" MAEW propellers I already have, and then maybe try some standard propellers at lower ratios.
14 Mar 00 - I managed to get down to the reservoir after work today for the first launch. The boat went well with a good turn of speed and appeared quite stable. The boat run a little to much stern low due to the weight of the batteries. Additionally, I "caught a crab" at the end and flipped the boat over, which would be assisted by lowering the batteries. I have decided to move the batteries into the rear of the radio bay. This means much longer cables, and therefore greater losses, but it should make the boat run much better. This moves the batteries forwards by about 14" (0.35m) and down by approximately 7½" (0.19m). I have already started work on the modifications & hope to complete before the weekend.
15 Apr 00 - I have now tried out the revised format and not flipped over yet. The boat rides more nose down as the weight has moved forward and it will be much more difficult to flip. The fifth picture above shows the revised format. I have also reduced the gear ratio to 2.4:1 and fitted an 11" x 10" APC propeller for the moment. I will be experimenting with different propellers to see which is quickest.
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