Reading the Roostertail

[Chilli]

Egneg brought up a point about the El Lobo IV he just splashed last weekend and I didn’t want to hijack any threads so I have started a new one. I have always been a little curious about the subject of rooster tails. Is a rooster tail one of the indicators of if the strut is properly adjusted? On my mono, my strut is neutral and level with the keel. I can see two distinct rooster tails. One is wispy and shoots up about 6-7 feet in the air. I assume this is the water getting thrown up off the face of the blade. My secondary rooster tail is much denser and is no more than two and half feet off the water. I assume this is thrust coming off the back of the prop. Now I have seen some very fast boats have a tremendously high and dense rooster tails coming straight off the back of the transom. I assume that is because they are using a prop with much more pitch. So the face of the blade is pushing much more water into the air. Is my theory sound??? Does a roostertail in fact tell us anything?

[Eodman]

I have no clue but they sure look pretty!

[Chilli]

I figured this post got moved to the stupid question section.:o Oh well. I guess you never know unless you ask. I do love a nice roostertail though.....

[raptor347]

The big pretty roostertails are the least efficient. Energy is being used to throw water in the air and not back as thrust.

The boat in the picture is my old N2/p spec boat. It's running an Sv27 motor, a full bladed 2047 with lots of extra pitch. In the pic it was running in the high 50's. The roostertail says that the prop isn't runing very efficiently.

My current boat runs a UL-1 motor and an H-10. The roostertail is only about half the density and a third as high. The boat runs in the mid 60's and runs a full race on about 15% less power.

All that said, the roostertail with all the prop passes in it looks cool.

[Fluid]

For years we have evaluated the roostertail of SAW boats to help tune them. As Brian stated, we look for a low, flat roost to indicate good efficiency. While many "fast" boats blow a lot of water into the air, they'd be faster if their 'tails were lower.

Below is a record pass for a P Mono. Note the roost is pretty flat, although there is probably a little foom for improvement.

http://i49.tinypic.com/14y4rhx.jpg

The T Mono below throws a big dense roost - but it isn't very efficient.

http://i46.tinypic.com/nls9qs.jpg

[Bill-SOCAL]

Isn't it fair to say that a larger boat, like a T mono above will have a larger roostertail than a smaller boat. Although I will agree the one above is pretty big.

[Chilli]

Good Stuff. Thanks Guys!!!