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Old 10-25-2016, 02:35 PM   #68
Ski in NC
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City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
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What you are missing is that the engine at various rpms is responding to the boat's load curve, which varies with every boat.

The Cat curves are an approximation based on the exponential prop curve. An approximation at best. Sometimes a boat does follow along closely to the approximation, but that is not often.

So using a few data points your boat did come close to the Cat prop curve approximation. That's great, but if you had flow instrumentation and did an actual instrumented run and plotted the boat load curve, you would see how different it was from the theoretical prop curve.

Curves matching at a couple points does not mean much.
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