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Stern digging in

 
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Sugar Mountain



Joined: 28 Nov 2003
Posts: 13
Location: New Hampshire

PostPosted: Mon Aug 30, 2004 8:14 pm    Post subject: Stern digging in Reply with quote

Under power, my boat REALLY digs in the stern!

At >6 knots (verified by GPS) the cooling pipe is well below water. I'm getting a nice stain line nearly mid-way up my stern.

For other's info, I can get going about 6.9 knots if I push the engine.

Is this normal for the 31-2 or is my prop misaligned or something?
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dmurraymaine



Joined: 07 Jul 2003
Posts: 21

PostPosted: Tue Aug 31, 2004 7:53 pm    Post subject: stern digging in Reply with quote

The P-31-2 has a theoretical hull speed of around 6.75 kts as I recall. With displacement hulls thats the point at which large amounts of additional power add little addditional speed. The digging in is what happens naturally when a displacement hull hits its hull speed.
Your actual hull speed is probably somewhat less due to bottom paint build up, trim etc. .

I have the same effect at around 6.5 kts under power. I can go faster under sail, usually on a broad reach since the wind pushes the boat and moves the center of gravity forward.

You may be able to improve the situation a little by moving the center of gravity a bit toward the bow. Are you storing a lot of gear in the quarter berth and sleeping in the v berth? A half full fuel tank and a full holding tank have a surprising impact on trim (although I wouldn't suggest that as a way of improvig performance.
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