Prop Location

I just thought that moving the prop further aft, to approxiamately the same location that an outboard prop is that their might be some performance gains without making the drive significantly more complex. Its seems that moving the prop aft would allow you to raise everthing up and either reduce the drag and or run a larger prop. But you are correct about the rudder and that is something that I will have to workout.

I am not interested in surface drives but that seems to be only area of research.

 

As a note. A uncupped prop of 2 blades is still USUALLY the most efficient. Thinner blades raise eff. also. Keeping the rpms low for a given size raises eff., but usually is not able to also give high speeds with high horsepower. Trade off time. A well designed and balanced hull is always the faster boat. Not stabile at speed? To busy worring to go fast. Speed requires the best knowledge of all the specialties.-----------------As a proof positive. Nuclear subs have the most eff. props. + 80 mph & faster at depth. The seatbelts are no joke.

 

bsmit24, ask Volvo why the IPS drive is installed backwards under the stern.

 

I am not sure I understand the IPS question.

I had a buddy in the national quard that joined up after finishing in his tour in the navy sub fleet and he said that the speed was more like 30 to 35 knots. Was the 80+ mph a typo or did I miss something?

 

The Nautilus, 1st Nsub ran away from our WWII 40 knot destroyer and off the sonar computer at 50 and accelerating fast. All NATO sonar operators had similar readings. We were fitted with a light cruisers steam chests, thats why we could do +40k. That is when we knew we would be a joke in a war zone. Our KILLER torpedos did 12K in attack mode.----------------- Volvo Ips is a stern drive mounted about where a shaft prop would be. It looks like a stern drive shoved right thru the hull with the prop always facing fowards. I take it that it should only feed solid water into the prop and all the prop thrust has to blow around both sides of the support. Less steering stalls and prop cavitation in a turn. Should be a little better than a I/O.----------------Nauti also fired a torp at the carrier. Accelerated passed the torp pulled along side the carrier and was hit by her own torp. That really drove the the point home to everyone.

 

The "new" old woodies racing boats do sometimes have the rudder and prop at or 1' behind the transom. They are the 600-800hp powered 22' partial surface drives. It does make them more eff. and faster. 22' and + $120,000.