Am I missing something?

[Moose]

I have noticed something odd in the test reports of the Beneteau 461 and 473. The 473 has a 75hp Volvo in it, flat out it managed a rather brisk 11kts!!! The 461 (2in shorter and 3in less beam) fitted with a 85hp Yanmar managed only 7kts flat out. Why is there such a big difference? They are both shaft driven. The sailing performance of both boats is nearly identical.

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Moose

 

[graham]

Could it be due to hull shape ? If the shapes are similar it sems a bit odd.

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[Moose]

The 473 keeps its beam further back but the difference is not dramatic.

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Moose

 

[longjohnsilver]

Different prop? Fouling? Engine not pushed to full revs?

No doesn't make sense.

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[Ships_Cat]

Inaccurate logs perhaps or if GPS used incorrectly applied. Seem to be alot of test reports with unrealistic results in the speed direction.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[jeanne]

I think Ships Cat has got it, its the log . Mine has a hole on the back for calibration, stick a screwdriver in, and set any speed you want. That would be tempting if you were trying to sell boats.
The only time I could use it was on an occasional trip on the Sharpness to Gloucester canal. They have mileposts, and non tidal water!

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[Moose]

Good point, obviously yacht testing peeps have no sensation of speed then/forums/images/icons/smile.gif

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Moose

 

[Robin]

The 11kt figure is above theoretical hull speed and 9kts is more likely . The 7kt figure is as low as the other was high, maybe there was weed on the log, log not calibrated properly or perhaps the boat had a wrongly sized prop. Which mag(s) did you get the test result figures from?

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[nicho]

Talking to a well known magazine boat tester not too long ago, it seems it is well known that manufacturers/importers send boats out for test purposes with "optimistic" logs....! Perhaps they went too far this time.

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[Twister_Ken]

Cobblers

11 knots is entirely unrealistic under power. I'd suspect a misprint or economy with the truth.

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[dwatson]

Re: Cobblers

11kts does seem on the high side but I have been onboard a 47.7 and managed around 10.5 under engine. The log was accurate but it was a boat in race mode on a flat calm day with around 10 crew standing on the bow to maximise its effective waterline!

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