- Robert Davidson's racing propeller has been tested on a 250w motor driving a 15 inch ducted fan and delivering 2500 C.F.M. at 0.45ins. w.g.
- Propeller testing was carried out on a 30 foot fishing trawler with a single cylinder, slow revving engine and a measured 4.5 hp at the tail shift. The propeller enabled this trawler to tow a 45 foot trawl net at about 4 knots and catch the same amount¸ type and size of fish to a similar sized boat and net with a four cylinder Ford engine rated at 66 B.H.P. Both craft had the same top speed when trawling (the test was carried out over a 4 hour period 12 miles off shore with a moderate Pacific swell).
- An experienced diver was placed about 20 foot under the test site. He reported that there was no noise from the Davidson Boat Propeller until it was directly overhead when a faint whistling noise was heard.
Seeing is believing
The propeller was tested on a single seater 25hp Hydra Sonic speedboat. The standard racing propeller was simply taken off and the Davidson Boat Propeller slipped on.
In the above photos the standard propeller had an output velocity of 15 m/s @3000RPM and the Davidson Propeller had an output velocity of 20m/s @3000RPM. Same boat, same driver and the same motor.
The standard propeller has 150 years of high-tech research, development and manufacturing behind it. The Davidson Propeller was made with sheet metal, a hammer, anvil and an electric arc welder. Using that method of construction it is not possible for the Davidson propeller to be better than the high tech standard propeller unless there has been a major breakthrough in propeller technology.
Static Thrust - added Feb 2008
A test rig was set up to measure static thrust in air. Amps could be measured to 0.005amps and thrust to 5grams, r.p.m. was 1380 and volts were constant. Tested were a commercial outboard propeller and a Davidson propeller, both were 280mm diameter with a pitch of 23 degrees. Thrust was the same for both propellers but the commercial propeller used 50% more power to do it than the Davidson. Results in kilos per H.P were- Commercial 12.7kg per H.P.
- Davidson 19.0kg per H.P.
Both tests were carried out at least six times and the same ratio showed up each time, 1.5 to 1.6.
This is quite significant as we know it efficiency peak lies at the top end not the bottom end.
We are currently seeking enquiries from companies wishing to license and manufacture the Davidson boat propeller.Please contact us for more information.