Wave-making drag for asymmetrical hulls

Discussion in 'Hydrodynamics and Aerodynamics' started by myszek, Jul 21, 2020.

1. Joined: Jan 2013
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myszekJunior Member

Hi

Do you know about any studies on wave-making drag for asymmetrical hulls? I mean not necessarily proas, but rather heeled monohulls.

A naive estimate is as follows:
Let's treat the halves of the hull independently.
The wave-making drag grows approximately as a square of the width, when other dimensions are constant. So, the heeled hull, with leeward side, say, twice as wide as the windward one, would produce 5.5% more drag than the symmetric one, which looks reasonable.

But a modern hull with wide transom can be much more asymmetrical. If all the displacement is placed on one side of the hull, which is close to reality in this case, then the crude estimation gives twice more drag than for the symmetrical hull. This seems too pessimistic, however.

I am sure that people tested this and there are some reliable experimental results...

regards

krzys

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gonzoSenior Member

I assume you are referring to sailboats. The path of the water is not fore and aft. It goes under the hull from one side to the other. This is particularly predominant at the edge of appendages, where a pressure differential exists.

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myszekJunior Member

Exactly. A typical sailboat hull with heel and some leeway is strongly asymmetrical:

How it affect the wave drag?

regards

krzys

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Mr EfficiencySenior Member

Use a model and conduct some tests, to satisfy yourself, weight one side with two pieces of lead, tow it by walking through some shallows with a string connected to a fish scale. Take note of the value, then place one of the two pieces of lead on the other side, and tow again, then note the reading on the scale for that. Use additional pieces of lead, to get greater angle of heel. That won't simulate what gonzo is talking about, the "crabbing" through the water, but it will tell you how the heel component alone affects drag, on that model at least.

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Doug HalseySenior Member

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myszekJunior Member

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