Frank Acampora
Supreme Mariner
- Joined
- Jan 19, 2007
- Messages
- 12,004
Re: Hswii or someone please help Prop
First, regarding your comment about factory installed foam: While it is true that that hull was Coast guard design approved for flotation, again, with that engine, I would bet that the hull would be only neutrally buoyant if flipped or immersed. It is just not enough. I used those foam cans and filled nooks and under the gunwales, using tubes for cables and controls. I also added a dozen 1/2 gallon bottles. All told, I probably added about 75 pounds of buoyancy with about 2 pounds of materials. Overkill? Hey, S**t happens and you never know when! You may never need that extra flotation, but if you do, it will be priceless.
Now: As you can see by reading Hswii posts, prop design is a bit esoteric. Simply speaking though Cupping has the same effect on RPM as an increase of two pitches. NOTE that it does not increase the pitch. So dropping down two pitches in a cupped prop may actually decrease speed. The trick is to experiment with engine height, prop diameter, blades, and pitch to find the best performance.
IF it is speed you want, you simply can not beat pitch and RPM. Without either, you can not go as fast as you may want. Do not be afraid to prop the engine with a smaller diameter prop with enough pitch that will allow the engine to rev to slightly over the rated RPM.
For example: on the 14 footer, the stock 13 inch prop in 21 pitch allows the engine to turn about 5500 and 55. The cleaver prop is 12 inch diameter, 21 pitch, has less blade area, and is cupped along the complete trailing edge. It allows the engine to turn 5900 (400 over rated) and 60 MPH. And, I am still experimenting. I have a 25 pitch 2 blade, but that engine simply does not have the B*lls to swing it.
Back to your GW: I'll bet dollars to donuts that there is an owners website and someone has a setup very similar to yours. They could probably save you a lot of time experimenting.
Someone is racing a 50 and they can probably tell you where to get a racing prop that is suitable.
First, regarding your comment about factory installed foam: While it is true that that hull was Coast guard design approved for flotation, again, with that engine, I would bet that the hull would be only neutrally buoyant if flipped or immersed. It is just not enough. I used those foam cans and filled nooks and under the gunwales, using tubes for cables and controls. I also added a dozen 1/2 gallon bottles. All told, I probably added about 75 pounds of buoyancy with about 2 pounds of materials. Overkill? Hey, S**t happens and you never know when! You may never need that extra flotation, but if you do, it will be priceless.
Now: As you can see by reading Hswii posts, prop design is a bit esoteric. Simply speaking though Cupping has the same effect on RPM as an increase of two pitches. NOTE that it does not increase the pitch. So dropping down two pitches in a cupped prop may actually decrease speed. The trick is to experiment with engine height, prop diameter, blades, and pitch to find the best performance.
IF it is speed you want, you simply can not beat pitch and RPM. Without either, you can not go as fast as you may want. Do not be afraid to prop the engine with a smaller diameter prop with enough pitch that will allow the engine to rev to slightly over the rated RPM.
For example: on the 14 footer, the stock 13 inch prop in 21 pitch allows the engine to turn about 5500 and 55. The cleaver prop is 12 inch diameter, 21 pitch, has less blade area, and is cupped along the complete trailing edge. It allows the engine to turn 5900 (400 over rated) and 60 MPH. And, I am still experimenting. I have a 25 pitch 2 blade, but that engine simply does not have the B*lls to swing it.
Back to your GW: I'll bet dollars to donuts that there is an owners website and someone has a setup very similar to yours. They could probably save you a lot of time experimenting.
Someone is racing a 50 and they can probably tell you where to get a racing prop that is suitable.
