Roostertail

[Jay Hames..MN]

I have seen the fishing-boat went fast with roostertail, how do they do that? Jay..MN

[joe]

I think that in some situations your big horse power boats are able to trim the motor up so far that it actually sends the prop wash up at a angle towards the surface of the water and thats what you see when they go blasting by. Some day when I get big, I want one of those.

[High 5]

The rooster tail is caused by the prop piercing the surface of the water, wether through trimming or lifting in the case of a jack plate. The tail should never be much higher than the top of the outboard on most glass fishing boats or you are losing ultimate performance to throw water into the air.

[REW]

In order to impress other folks - some folks add a "rooster tail generator."

This is actually a stainless steel scoop that is mounted just at the water line on the transom of the boat. This scoop, actually scoops the water from the lake and throws it into the air. Actually quite effective - and doesn't hurt performance much.

If, on the other hand, you have your motor trimmed out so far - that you are using the prop to throw water into the air - you are losing performance big time.

A third way that rooster tails are formed is from improper depth finder transducer installations. If a transducer is installed to run so deep, or tilted at a certain angle, or if a gap is allowed to occur between the front edge of the transducer and the transom of the boat -- a "scoop" is formed that can generate a tremendous rooster tail.

I suspect that many of the rooster tails that you see on fishing boats are actually caused by this third item. i.e. improper transducer installation.

Bottom line --
If you are throwing water into the air, you are taking performance away from your boat. If you want maximum performance, you need to figure the best way to couple the hp of the engine to the water. You want the hp of the engine to be coupled in a straight line fashion - straight away from the motor. this will give maximum performance to the boat. If you are generating an upward force with the water, you are allowing the boat to be going slower. Because this upware force is actually trying to drive the stern of the boat down. If the stern of the boat is being driven down, you are not going forward as fast as you might otherwise be going.

This is basic physics 101. To maxamize a force -- you need to keep the forcing vector aligned with the object to be moved.

Take care

REW

[High 5]

Sorry REW you're all wet on this one. Progressive rake, cup and pitch are all terms for tweaking that are done to stainless steel props to provide higher performance in surface piercing conditions. I know what I'm talking about on this one. And anything dragging in the water affects performance. On a well set up rig that transducer or a on the fly water pickup can cost 2 to 3 mph.

[REW]

High 5
Actually, I think that we are both saying the same thing.
You indicate that prop changes - make boats go faster.
I agree.
You indicate that surface piercing props make boats go faster.
I agree.
You indicate that anything dragging in the water make boats go slower.
I agree.
You indicate that if spray is tossed higher than the top of the motor - you will be going slower.
I agree.

Take care

REW