Crouch's Calculator

Optimizing the performance of Boston Whaler boats
jimh
Posts: 8979
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Crouch's Calculator

Postby jimh » Sat Oct 17, 2015 9:52 am

The very useful Crouch's Calculator is at this moment no longer available due to the move of the website to a new host. I am particularly fond of this calculators and will be making an effort to it working again. While there are many alternative calculators available for the propeller calculations, the Crouch's Calculator was unique.

[Updated April 8, 2021]

jimh
Posts: 8979
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: Crouch's Calculator

Postby jimh » Sun Oct 23, 2016 8:36 am

Crouch's method came to my attention in a book, PROPELLER HANDBOOK, written by naval architect Dave Geer. The original speed predictions and hull constants were for boat speeds in nautical-miles-per-hour, but I preferred to use statute miles per hour, and emended the formulas to give the predictions in that speed unit. I created an on-line interactive calculator that was quite unusual and was the first known implementation of Crouch's method in an on-line calculator. Unfortunately, a change in the website hosting arrangement caused the calculator to go offline due to the particular underlying software used in its design.

An alternative to the Crouch's Calculator that was available here has been found at

http://www.go-fast.com/boat_speed_predictions.htm

Although the above linked page attributes this analysis to Mercury Marine, the method is identical to Crouch's analysis. The basis for Crouch's Calculator was the observation that boat speed is proportional to the power-to-weight ratio to the 0.5 exponent times a constant that was scaled for the type of moderate v-hull planing boat being analyzed. For a typical Boston Whaler hull the hull factor of 180 can be used to get a reasonable estimate of hull speed potential in MPH.