Just been having a think about the prop size
In full size ski boats if you increase the pitch of a prop on a given engine then you change the "punch out of the hole" and the top speed.
The punch out of the hole i refer to is i guess the take off of the boat from a standing start. this usually gets better with a smaller pitch then a large pitched propeller until some point where it becomes counter productive.
This reduction in pitch however tends to create a lower topend speed, actually a lower speed across the whole rev range
That is to say that:
at 2000 rpm with a 21" prop the boat may be going 35 mph
but with a 19" prop pitch the boat will only be going 30mph at the same rpm but the 21" may tend to "bog down"
So you have to have a tradeoff between punch out of the hole (torque?????) and top end speed
Does the same thing occur on the much smaller scale of the RC boats?
For example the 98mm pitch prop i have at the moment might give more punch our of the hole but less top speed so if i retain the same diameter of 70 mm or there abouts and just increase the pitch i would get a faster boat assuming that its the same as my personal experience with full sized boats.
I guess i can only really confirm or deny this theory by actually testing different sized props but I'm interested to know your views on pitch
also Whit effect does increasing prop diameter have?
Thanks once again
Tim (feeling like i should stop asking so many questions
)