I am trying to validate my Wyman power and resistance results from MAXSURF Resistance, however when following the very little information available from MAXSURF on the equations used for this analysis, I always get a lower HP value than MAXSURF predicts.
My question is, following the equations described on pg. 14 of this website: http://www.westlawn.edu/news/WestlawnMasthead06_June08.pdf, can I verify the power results using the SHP in that formula vs. the Wyman HP output in MAXSURF Resistance?
The equations used in the above website are:
SHP=(displacement/1000)*(speed(kts)/(Cw*(LWL^(1/2)))^3
Cw=(0.8+0.17*(SL))
SL=speed(kts)/(LWL^(1/2))
Where if I pick a speed to verify, using the LWL and displacement, I have been unable to match the HP calculated in MAXSURF Resistance.
I figure I am either misunderstanding the Wyman equations, or MAXSURF is including something I am not!
Hi Lauren,
Page 52 of the manual has a link to an updated version CW calculation for Wyman. Checking Resistance against an Excel calc using the updated CW gives me a very small but consistent error. (I think my error might be my seawater density in US units)
So it looks like the updated Cw is the one to use.
http://www.westlawn.edu/news/WestlawnMasthead06_June08.pdf
http://www.westlawn.edu/news/WestlawnMasthead07_Sept08.pdf
Regards,
James