Atkin's Happy Clam's propeller

[Dave G 9N]

The point of asking about this boat was to decide whether it could reasonably be expected to perform as advertised. From the answers I have gotten, it just might. 2 blades looks like the most efficient option. The optimum 2 bladed prop diameter and rpm is easily calculated. Thank you Adler. To figure out the pitch, build the boat, install an engine and prop and test it. Not as clean cut as I might have liked. It might be interesting to find the answer.

I went to the link. It has an estimate from someone that calculated with zero slip, and another from someone using 35% slip. There is no actual measured speed,

I indicated that the link to WBF was just to document the source of the quote. I'm pretty sure you realized that zero pitch was part of the rationale for discounting the test results and 35% slip was from a slip table, so you're having me on. No worries. You asked for data in post 39. Everything available is in post 40. You asked again in post 42, and it was in the attachment to post 43. Three data points. 2 calculations by the designer and one flawed test. 3 speeds, one real engine, two hypothetical, one rpm and an erroneous pitch. Insufficient data, understood.

 

[skaraborgcraft]

At least "Happy Clam" was tested. The issue I had with some of Atkins claims was that in some designs, including a boat he had built for his own use "we.re here", did not match the claims he made it should achieve. I was always left wondering what formulas he used to calculate his predictions, and how much was guesswork based on past experience. I was also doubtful about his claims for "Surprise", but it was later established accurate by a user.

 

[gonzo]

I really like Atkins designs. I also believe that he exagerated the performance to sell them.

 

[rangebowdrie]

I really like Atkins designs. I also believe that he exagerated the performance to sell them.

Me too, studied the drawings of every design of his I could find in print, starting ~60 years ago.
And yes, he probably did "bend the curve" a bit at times. I got a feeling that much of his data was more-or-less empirical.
Dave, you've probably already done several times as many calculations for that boat as Bill ever did, lol.