High Speed Boat Design Part 2-Wings
By Lohring Miller
NAMBA Safety Chairman
We discussed two things in the last section that greatly affect
the performance of fast boats, air lift and planing drag. This
article concentrates on wings. First, a brief explanation of the
forces on airfoils. The forces are calculated by the dynamic
pressure times an experimentally determined coefficient and the
surface area. The dynamic pressure is the density of the fluid (air
or water) times the speed squared. Because the speed is squared,
the force goes up very rapidly with an increase in speed. Note
also that water is 800 times as dense as air. That means that a
force on the same object in water is 800 times as strong as the
force on the same object at the same speed in air.
The coefficients mentioned above are the coefficient of lift,
drag, and moment. They are proportional to the lift, the force at
right angles to the flow direction; the drag, the force along the
flow; and the moment, the force rotating the airfoil. Multiplying
the coefficients by the surface area of the airfoil and the dynamic
pressure gives the actual force.
Understanding how to make air lift improve performance
requires understanding how airfoils work close to the ground.
Far from the surface, the low pressure created over the top of a
standard airfoil creates some of the lift. However, close to a
surface, the air compressed between the bottom of the airfoil and
the surface becomes more important. Let’s look at what happens
with a standard NACA 2412 airfoil. The pictures below are from
Martin Hepperle’s airfoil analysis tools for two dimensional flow
over the airfoil. Real flows are more complicated, but have
similar trends. The flow field pictures show the pressures over
the airfoil. Orange going to red shows increasing positive
pressure, and green going to blue shows increasing negative
pressure. I angled the airfoil so the bottom is close to parallel to
the ground. First the pictures show the airfoil well clear of any
surface.
Fast and Furious in District 3
By Ron Byrd
District 3
The 2017 season started off with the 3
rd
Annual Winter Nitro
Championships in Brandon, Florida held January 13 through 15.
This was a joint effort between the Brandon Model Boaters and
the Tampa Bay Model Boat Club. The total entries came to 55
contestants with 155 Boats in 16 nitro classes.
We were honored to have four friends from Germany make
the trip as well as two from Alaska. The racing was fast and
furious in the three qualifying rounds with one goal in mind. To
gain one of the coveted top six spots and race in a two round
finale in each class.
Please feel free to visit
to check out the
Video’s and Photos section in our gallery.
The results are as follows
PROPWASH
14
April 2017
Markus Schwab and Winfred Ott from Germany
Sport 21
Jerry Kelley
Phil Thomas
Warren Tremblay
A Stock Tunnel
Jeff Maturo
Greg Rowe
Andy Smith
A Mod Tunnel
Zack Junker
Jeff Maturo
Ron Byrd
A Mono
Marty Davis
Jerry Crowther
Phil Thomas
A Hydro
Markus Schwab
Zack Junker
Doug Murany
B Mod Tunnel
Jimmy Duncan
Andy Smith
Mic Halbrehder
B Mono
Jerry Crowther
Rick Bellinger
Mark Adams
B Hydro
Danny King
Graham Lathan
Doug Murany
Sport 40 II
Ron Byrd
Phil Thomas
Rick Bellinger
Scale Unlimited
Rick Bellinger
Jerry Crowther
Ron Byrd
C Mono
Jerry CrowtherT-
ommy Cardoso
Gene Mongar
C Hydro
Ralph Almirola
Mark Grannis
Thomas Elkins
X Mono
Joe Warren
Jerry Crowther
Gene Mongar
X Hydro – Single
Mark Adams
Mark Bullard
Dick Jones
X Hydro
Gary “Doc” Turner
Tom Foley
Joe Warren
Twin Nitro Rigger
Joe Warren
Thomas Elkins
Ralph Almirola
