Min Rudder Depth and shape

[anthony_marquart]

I'm looking at rudder depth. I think it might be overlooked at times when looking for speed. (lots o'drag)

What is the min rudder depth you guys have been able to run. Measured from prop centerline,..

On rudder shape,.. has anyone ever tried a rudder that has the shape of the tear drop, fat at the from and tapered to the rear?,.. This would have much less drag than the wedge.. We know the rudder drag does help with stability,.. this might make other changes needed also..

 

[Paul Traufler]

Hey Anthony, this has been worked on a good bit, but as always there is more info and new ideas that come along and can change things. The rudder depth will drive the turning "power" as well as the straight line stability so that is tied in this also. The rudder shape well that is a bit more clear, the "tear drop" you suggested is good for air flow but in water and the speed the boats are doing the wedge works better. I know does not sound right but recall water is about 750 times more dense than air so the flows around objects is very different. The real hard part about doing any hydrodynamic analysis is the fluid (water) and speed put the flow in a range that is not easy to predict flows for. (I did NOT stay at a Holiday Inn Express, but rather went to college and earned a Aerospace Engineering degree so I have some knowledge on this topic.)

There is another wrinkle in this also, rudder width, these all need to be studied to figure out the best solution for our application.

Paul

 

[Tom Foley]

http://rcboat.com/past.htm

 

[Terry Keeley]

I fought a high frequency hop in my 40 boat for years, turned out to be the tapered rudder blade I was using.

Put a straight blade on and it went away completely.

Only straight blades now for me on all my boats.