| Raingutter Boat Racing - |
Breathing Life Into Your Boat |
Boat Profiles
In order to calculate meaningful results from the models some reasonable
values must be assigned to the model variables. Below is an attempt to do
that. These values for a hydroplane, a catamaran and the raingutter arena
are used in various calculations in this manual as defaults.
Default values are used in those calculations when no other value has been
given.
A raingutter section is 10 feet (120 inches) long. Typically, this is
the full length of the regatta course. For a boat to fit into it and go the
distance, it actually travels the 10 feet minus its length. Rules require
the boats to be six inches long or less; this may be different in your
race. So the distance travelled is 114 inches.
Default Variable Values
| Symbol |
Value |
Units |
Why? |
| L |
114 |
in |
10 feet - 6 inches (boat length) = distance travelled |
| g |
386.088 |
in/s2 |
acceleration of gravity at sea level |
| p |
0.0014945 |
ozs2/in4 |
mass-density of water |
| pa |
0.000001878 |
ozs2/in4 |
mass-density of air at 60 deg F., sea level |
These are the default model values for a hydroplane. The coefficient of
sliding friction over water is included here since it at least depends on
the boat's shape.
Default Variable Values
| Symbol |
Value |
Units |
Why? |
| m |
0.002590 |
ozs2/in |
minimum mass allowed in race = 1 oz/g |
| S |
5 |
in2 |
sail profile = 2.5 in x 2 in |
| A |
7.5 |
in2 |
forward profile = 2.5 in x 3 in |
| n |
TBD |
scalar |
sliding friction coefficient (on water) |
| s |
1.3 |
scalar |
typical for a parachute |
| e |
0.7 |
scalar |
a little worse than a sphere |
| spS |
0.00001221 |
ozs2/in2 |
aerodynamic sail force per breath speed squared |
| epA |
0.00000986 |
ozs2/in2 |
aerodynamic resistance force per boat speed squared |
| B |
440 |
in/s |
Breath speed; measured |
| v |
? |
in/s |
Boat speed |
| a |
? |
in/s2 |
Boat acceleration |
These are the default model values for a catamaran. The coefficient of
pressure drag in water is included here since it at least depends on the
hull's shape.
Default Variable Values
| Symbol |
Value |
Units |
Why? |
| m |
0.002590 |
ozs2/in |
minimum mass allowed in race = 1 oz/g |
| S |
5 |
in2 |
sail profile = 2.5 in x 2 in |
| A |
0.3 |
in2 |
forward profile of hull below water line |
| s |
1.3 |
scalar |
typical for a parachute |
| q |
0.7 |
scalar |
a little worse than a sphere |
| e |
0.5 |
scalar |
coefficient of pressure drag in water |
| spaS |
0.00001221 |
ozs2/in2 |
aerodynamic sail force per breath speed squared |
| qpaS |
0.00000657 |
ozs2/in2 |
aerodynamic resistance force per boat speed squared |
| epA |
0.00022418 |
ozs2/in2 |
hydrodynamic resistance force per boat speed squared |
| b |
440 |
in/s |
Breath speed; measured |
| v |
? |
in/s |
Boat speed |
| a |
? |
in/s2 |
Boat acceleration |
| Raingutter Boat Racing - |
Breathing Life Into Your Boat |
| Copyright © 1997, 2000, 2002, 2004 by Michael Lastufka, All rights reserved worldwide. |