Prototype Testing

This weekend, we conducted on-water empirical testing of the new staggered-blade propeller prototype. Weather conditions Sunday were near ideal. The lake surface was very calm—effectively mirror-smooth. I was the only vessel operating in the main section of the lake during the tests, so there was no wake interference from other boats.

Data collection method:
Boat speed data points were taken only after the vessel was fully up to speed and running consistently. Because the engine would occasionally rev slightly above or below the target range, speed readings were recorded only after the tachometer had held the target RPM steady for approximately 10 seconds. The C-Maps app was used for all speed measurements and updated rapidly in response to changes in velocity, indicating a consistently strong GPS signal throughout the testing period.

The test runs were conducted along a 1.3 mile buoy-to-buoy area in the central section of Upper Lake Mary, in waters ranging between 17–20 feet deep.

Initial performance observations:
After compiling and averaging the boat speed data for each propeller configuration, several clear trends emerged. The staggered-blade configuration was, on average, faster than the Mercury Spitfire four-blade propeller across all tested RPM ranges--which is pretty remarkable for an 8-blade prop. The propellers we intend to bring to the market first will likely have 3 pairs of blades instead of 4, and they should be considerably faster and more efficient than this prototype.

The differences were pronounced at 2,500 RPM, where the staggered configuration achieved average speeds approximately 21% higher than the Spitfire. At this range, the boat was planing under both configurations, though the staggered design showed a clear advantage in maintaining speed and stability.

Another notable observation was the earlier planing threshold with the staggered propeller. The boat consistently transitioned onto plane around 2,250 RPM with the staggered design, compared to approximately 2,450 RPM with the Spitfire. The difference was particularly striking: the staggered configuration was 43% faster, as it had just come over the hump of its own wake, while the Spitfire remained in displacement mode.

Given the fact that the design for the prototype with staggered blades was limited by the choice of using the Mercury Spitfire as the forward assembly, these results are striking. In a number of respects, they exceed what was predicted by the models.

The next steps are for the Teignbridge Propulsion Research Centre to adjust and validate the assumptions built into the CFD model. Using the revised model, they will create amended designs that are optimized for specific use cases--such as inboard propellers for leisure yachts and outboard propellers for saltwater fishing boats.