Michael:
Please note, your email program must let you see this as html to see the formula below. If not, just follow the link to the source. I didn't write this, its cut-and-pasted.
rgds,
Alec
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In general, the force on a hydroplane can approximately be
calculated from the following equation:
| F = C A sin(a) 0.5 r v2 | F : Force on hydroplane (kg)
C : Friction coefficient (C = 0.1) A : Area of hydroplane (m2) v : Velocity of boat (m/s) r : density of water ( r = 1000 kg/m3) a : angle of hydroplane (deg) |
Equation 1: Force acting on a hydroplane.
For example, if we would have a model submarine with square
hydroplanes of dimension 5 x 5 cm, this leads to an area of the individual
hydroplane of A = 2.5 10-3 m2. With a boat traveling at a speed of 10 km/h (v =
2.78 m/s) and a hydroplane down angle of a = 30 degrees, the down force on the
hydroplane is about half a kilogram. Since the boat has two forward dive planes
the nett down force would be close to a kilogram. This means that the positive
buoyancy of the boat can also be allowed to be a kilogram. However, at lower
speeds than 10 km/h or at hydroplane angles less than 30 degrees, we will not
able to submerge such a boat! Equation 1 can be used to design the size of the
hydroplanes or the allowable positive buoyancy for a given hydroplane size.
Please note that the value of the friction coefficient C is dependent on the
design of the hydroplane, C=01 is the maximum value. In updates of this page
more accurate values of the friction coefficient C will be given. Generally, for
fully dynamic diving models one would want the boat rigged close to neutral
buoyancy. That is, the decks awash situation. In that case, the boat can be
submerged at low speeds with a realistic size of the dive planes. However if the
boat is already close to neutral buoyancy, the surface running is not very
realistic. To obtain realistic surface and submerged operation ballast tanks are
needed.
Source: http://www.heiszwolf.com/subs/tech/tech01.html#Dynamic
-----Original
Message-----
From: Michael B Holt [mailto:tlohm@juno.com]
Sent: Monday, March
03, 2003 4:05 PM
To: personal_submersibles@psubs.org
Subject:
[PSUBS-MAILIST] Positive bouyancy
How can I calculate what size
diving planes I need to keep
a sub submerged if it's positively
bouyant?
Mike
H.
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