drive lines

[Guest]

driveline down the centreline or offset which is best and why

 

[Bob Morton]

driveline down the centreline or offset which is best and why

Center is best B) B)

Bob Morton

 

[Al Waters]

I think it depends on the hull.

I run a chisel nose and I offset............

Al Waters

Southern California Scale Thunderboat Association

NAMBA Scale Unlimited Chairman

 

[Mark Anderson]

I have never compaired in the same hull to see how much of a difference it makes. Theoretically putting the drive train toward the left will weight the left sponson and give the right more leverage against prop torque. I used to build boats with the engine to the left and the prop centered under the hull. My current boats have everything offset to the left. Besides the weight and leverage, It also changes the aerodynamic properties of my boat to put more lift on the right side due to cowl and belly pan location. Again I have no real data to prove any of this other than the fact the boat rides very well.

Mark

 

[Paul Pachmayer]

Hello Guys,

I've built several of the boat in my avatar and tried offset, angled and straight down the middle. All of them preformed about the same so now I just run it down the center with a "slight" angle to the left, about 1 degree only.

Paul.

 

[Advance_United]

Al, What handling dynamic changed when you rigged the boat with offset?

Concerning right sponson loading due to applied propeller torque: CMD's quoted specification for the MAC 67 is 6.0 bhp @ 27, 000 RPM. Torque calculates to 1.167 lb. ft. (224 oz. in.). The dimension from the center of the hull to the first point of contact on the right sponson running surface of my Bud T-5 is 0.72 ft (8.625 in). At maximum applied torque the sponson is loaded @ 1.62 lb. Assuming a 0.25 in. left offset for the strut, the loading decreases to 1.58 lb. The reduction of 0.04 lb seems relatively minor.

Is there any data regarding propeller thrust? In specific applications is there a force balance between thrust and the resultant of hydrodynamic / aerodynamic drag when the strut is fitted at a certain dimension relative to the hull centerline?

It looks like offsets have gone in and out of vogue with the full sized guys so who knows.

 

[Al Waters]

I can hear Mark Anderson laughing right now. I am a card table boater so you are way over my head.

The boat I run was designed by Ira Cotton in 1977. I built mine in 1993. If he tells me that the boat runs better keeping the front sponson down with an offset strut pointed towards the motor to counteract torque.............. I do it.

The answer to your question would be it rides flat and goes in a straight line at full speed. A centerline strut on this boat would not do that.

Al Waters

NAMBA Vice President

NAMBA Scale Unlimited Chairman

Southern California Scale Thunderboat Association