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Boat Pulls Hard to the Right !
January Tech Notes
A Supplement to The Engine Analysis Software
and
The Prop Duplicator
How many times, have I had a new boat at the pond for the first time,
and it pulled to the right on the straight-a-way. I had to hold almost full left rudder to
keep it straight? Had my boat building slipped? Was the boat
set-up completely wrong? Was the rudder servo to weak? What
the heck was wrong with the boat !!!!!
For Model Boaters, THIS IS THE MOST IMPORTANT TECH ARTICLE I HAVE WRITTEN SO FAR .....!!!!
I have finally found the answer to these questions!!
About a month ago I was helping a friend set up his boat. He
asked me to drive it and see what I thought. I drove it, and it
pulled into the course VERY BADLY! I had to hold full left to
keep it straight down the straight-away. I brought the boat in
and thought about my experience with a prop I had bought from
Tidewater Engineering. I had been running their 4 blade prop
on an experimental Roadrunner. I was using a prop
which I sharpened and balanced. I found that this prop ran with
no pull at all. I put on a backup 4 blade prop and it pulled
into the course BADLY. What was the reason?
I studied the two props and found that like any retailer,
Tidewater had done a BEAUTIFUL job of polishing and balancing
this prop, BUT had not sharpened the leading edge to a razor edge. I wouldn't
have either, and taken a chance of rolling an edge. But, this
lack of a razor edge made the first part of the blade that came
in contact with the water present a DULL EDGE to the water. Not
only 1 dull edge but 4 dull edges. This made the prop try to
climb out of the water and "walk the transom of the boat"
to the left, making the boat pull into the course badly. I had
finally solved one of the mysteries I had been unable to solve
over 25 years of racing. It was so simple that I felt stupid!
The boat I was asked to set up for my friend was
brought to shore, he sharpened the entering edge of the prop,
and it ran without any pulling to the right.
I am happy to share this with everyone, and hope that
it helps you solve what has been a mystery to me for a LONG time.
To be specific about where to sharpen the prop to
eliminate this pull: The edge of the prop which enters the water
first and is attached to the hub is the most important, with the
remainder of the edge of the prop all along the "tongue"
and sides of the blade. It is EQUALLY important to not only sharpen
the edges, but to blend them in at least 3/16" into the blade so the water
sees a VERY GRADUAL ENTRY of the blade thickness.
Always sharpen the back side of the
prop only and be sure to de-burr the edge of the prop with 600
grit sandpaper. It will be very sharp with only the edge burrs
removed.
Until next time ………..
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