Re: Stus-List Theoretical Hull Speed

[Bill Bina]

As I pointed out, hull speed CAN be exceeded. It just takes exponentially more power to do so. Hull speed is a threshold, not an absolute barrier. It is very possible that the figure you are using as your theoretical hull speed may not be 100% accurate either. If you observed this speed on a GPS, it may have been distorted by the boat veering direction, or riding up and dropping off of waves, all of which can be faster movements than your forward progress. I have a 27-5 which, under the right conditions, planes fairly easily and hits significantly above theoretical hull speed for prolonged periods. A GPS cannot be used for determining speed through the water, which is all that counts when talking about hull speed. Bill Bina On 5/19/2013 8:25 PM, sam.c.sal...@gmail.com wrote: I was on a lake so current wasn't a factor.  sam :-) 403-617-6280 From: Bill Bina Sent: Sunday, May 19, 2013 6:19 PM To: cnc-list@cnc-list.com Reply To: billb...@sbcglobal.net Subject: Re: Stus-List Theoretical Hull Speed Theoretical hull speed is rarely exactly calculated, as there are factors in play besides just length of waterline. Length of water line is just the most prominent factor. Beam relative to length, wetted surface, etc, all play minor roles. That said, hull speed is really just a "sweet spot" where the effiency of a displacement hull has reached it's maximum potential. To get any additional speed, you need a LOT more power. Dubling you power applied will not give you very much additional speed.  I can get my boat to it's hull speed under power at about 1/4 throttle. To go noticeably (a little) faster, I have to go almost to full throttle. That is in flat water with relatively no current. The place where a bigger engine, or more throttle, makes a difference in a displacement hull is the better acceleration (up  to hull speed) that gives you quicker recovery after being hit by waves head-on.  Also be aware that hull speed is speed through the water, not speed over ground. The direction of the current counts! Your GPS may say you are doing 8 knots, but 2 of that may be the outgoing tide that is adding to your speed over ground, but not your speed through the water. I'm using motoring in my examples because it is a little simpler to explain and understand without all the added information as to point of sail, windspeed, sails being flown, etc. Bill Bina On 5/19/2013 7:41 PM, sam.c.sal...@gmail.com wrote: My 26 has a theoretical hull speed around 61/4 knots. I've had 7.9 on a beam reach once with main and 135% genoa. So your not alone! I guess the optimum word is theoretical.  Sam Salter  C&C 26 Liquorice  Ghost Lake Alberta

_______________________________________________
This List is provided by the C&C Photo Album
http://www.cncphotoalbum.com
CnC-List@cnc-list.com