Frank Acampora
Supreme Mariner
- Joined
- Jan 19, 2007
- Messages
- 12,004
Re: Technical questions boating forces
Back again! As you can see,this hull has almost no drag with only about a foot of hull on the water. It is a flat bottom with a riding pad. Modifications are scheduled to lift the hull higher with more air entrained under the hull, and that will probably only result in a 5 MPH speed increase. additionally, with so little hull in the water I need to add a turn fin. As it stands now, the hull skids at speed and I need to slow down to make any kind of turn. To go further in speed, I would need to redesign the lower unit: put on a low water pick-up,a nose cone, get a surface running propeller and jack the engine so only the skeg is in the water. Too much money and work for what is basically a fun go-fast.
In fact, once you get the hull to the point where air resistance becomes important, lower unit design is critical to performance. The original lower unit for this engine would "blow-out" at speeds over 60 because of the nose shock wave. A factory redesign resulted in a 3 MPH increase in top speed on recreational boats. I know it will not blow out at 60, but I don't know what the top limit is.
Back again! As you can see,this hull has almost no drag with only about a foot of hull on the water. It is a flat bottom with a riding pad. Modifications are scheduled to lift the hull higher with more air entrained under the hull, and that will probably only result in a 5 MPH speed increase. additionally, with so little hull in the water I need to add a turn fin. As it stands now, the hull skids at speed and I need to slow down to make any kind of turn. To go further in speed, I would need to redesign the lower unit: put on a low water pick-up,a nose cone, get a surface running propeller and jack the engine so only the skeg is in the water. Too much money and work for what is basically a fun go-fast.
In fact, once you get the hull to the point where air resistance becomes important, lower unit design is critical to performance. The original lower unit for this engine would "blow-out" at speeds over 60 because of the nose shock wave. A factory redesign resulted in a 3 MPH increase in top speed on recreational boats. I know it will not blow out at 60, but I don't know what the top limit is.
If you raised the outboard so the thrust met the center of mass, it would end up pushing the bow down via the prop lifting force.