Hello all, I currently am running my Scharnhorst on a single screw with a BC gearbox 16 tooth pinion and a 40 mm, 4 bladed, 40 degree prop. The shape of the blades is not round like the ones at BC, but longer and thinner. Even though he ran excellently at CANNATS, I was not happy with the braking and reversing times. It took WAY too long to stop and then go in reverse. I was wondering if anyone can tell me how well the Scharny works (acceleration, braking and reversing) with the round bladed, low pitch prop on a single screw or if anyone has ever tried running a Scharnhorst with 3 drive props? If so, what did you use? Gears, prop sizes, blades and pitch? Thanks, J
The more blade area on the prop (round blades) and the lower the pitch of the prop (25 deg) and the more blades the better starting and stoping you'll have. Try out the 2" 4 blade from BC and snip the blades so the overall size is 1 3/4". This should help a lot. If Dumas still made the 4 blade cast props you could put these on backwards and get more thrust in reverse. But you sacrific some starting power. You can also run the outer props in reverse only. You'll only need small 1 1/4" 3 blade props and cruiser size motors. Running all 3 props forward destroys your turning.
Yeah, more blade area near the tips is the key, as that's where they're moving the fastest. Getting the 2" and cutting them to 1.75" will give pretty much the most blade area you can get at the outer edge.
Sounds good to me, I'll give it a try. Now, I don't understand why running 3 shafts will destroy my turning (which is phenominal by the way, I can turn in my own length). It seems to me that having prop wash from 3 props passing over the rudders as opposed to one would cause at least the same ability to turn if not better. Can someone explain it to me. Thanks, J
Easiest explanation is: The prop on the inside edge of the turn is opposing the turning force. It's too far away from the rudder to really get any appreciable wash over it.
