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Hull Modifications

Posted: Fri Feb 27, 2009 1:39 pm
by tugboatlarry
I have a 19 ft Glastron day cruiser with a Mercruiser 150 hp I/O. It is about to go into drydock (the garage) for repairs to a leak. This hull is absolutely incapabable of steering a straight line at hull speed or anything less than about 20 kt. Does anyone have any thoughts about adding a fairly shallow keel/skeg to improve low speed steering/ Is there a better way?

Re: Hull Modifications

Posted: Sat Nov 28, 2009 3:13 pm
by jivins
My opinion would be that you have to much weight in the rear. Does the boat seem to be at an awkward angle during high speeds? If so then you have to much displacement in the stern either move the engine foreward or decrease the engines weight. Only my two cents I'm no expert.

Re: Hull Modifications

Posted: Sun Nov 29, 2009 10:10 am
by BillW
You are probably experiencing what is know as "deep-V wander". Sort of like a flag waving in the wind, the left and right sides of the deep-V bottom alternately produce low and higher pressure (only at displacement speeds) and the driver then overcorrects. Probably not a good idea to add a keel or skeg; it's just one characteristic of the deep-V hull. When it starts to do this try to hold the wheel still and correct very minimally.

Re: Hull Modifications

Posted: Sun Nov 29, 2009 2:11 pm
by billy c
i have fixed a similar problem and it had nothing to do with the hull. my guess is that the hull is fine.
what i did was secured the helm so it would not move. then went back to the outdrive and tried to move it. the drive moved about 1/2" each direction! checked the steering/tiller yoke where it bolts to the outdrive and the bolt was not tightened! FIXED... there are other components in the steering system that may also be causing the problem that should get checked before touching the hull.

Re: Hull Modifications

Posted: Sun Nov 29, 2009 4:47 pm
by BulldogBoater
Same thing in my deep v. Slower speeds it wanders. Power up and it is straight as an arrow. I just powered up and didn't worry about it.

KB

Re: Hull Modifications

Posted: Wed Sep 20, 2017 4:16 am
by Randeb74
Deep V Wander. Thank you as this is the first explanation that I have come across. I'm experiencing the same thing in a planing hull at hull speed. Don't like the fact that there isn't much you can do about it though.