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Author Speed Log
Russ Hauser
Tavares, FL

Boat Name: Serenity Now!

Model/Year: 1982

Hull No. CTYH1337M82L

Hailing Port: Lake Harris
08/29/2006 1:41 AM Pacific Time

I'm a newbie asking for advice. Seems to me that if you're serious about racing and want the to know if you're getting the best performance from your boat, you need to know boat speed thru the water, and you need a thru hull speed log for that. Right? I've been told that all I need is a GPS. This would give me speed over the bottom, and would relate to navigation, but not necessalarily to speed thru the water.
rick
Waukesha, WI.

Boat Name: Gotta Fly

Model/Year: Cat-22/1987

Hull No.

Hailing Port: Milwaukee
08/30/2006 1:41 PM Pacific Time

Sounds like you are just looking for a baseline to determine what is effectively increasing your speed. In that case, it wouldn't really matter as long as you consistantly use that source for your speed. Personally, I am a traditionalist and prefer my knotmeter, although I would think a GPS would be more accurate.

This brings up another issue that I am sure has been debated over time.....a knotmeter reads relative movement through the water. If the boat was holding still in a 10 Knot current, a knowmeter would indicate 10 knots when you wouldn't actually be moving at all. A GPS doesn't have to worry about that. I am sure others will chime in.
Lynn Buchanan
Nevada City, CA

Boat Name: SAILYNN

Model/Year: SWING 1984

Hull No. 11994

Hailing Port: SCOTTS FLAT LAKE, CA
08/30/2006 6:08 PM Pacific Time

I've used both and as said earlier, it's all relative to the baseline. The kicker is how long of intervals do you get updates? On a GPS it's noticeably slower to get speed updates than if you have a knotlog. If your going to just cruise, the GPS is cheaper and will do what you need. If your going to seriously race, IMHO go with the knotlog.
David J. Pierce
Sunset, Louisiana

Boat Name: Little Miracles

Model/Year: 1985

Hull No. 12822

Hailing Port: Cypermort Point, Louisiana
08/31/2006 3:57 AM Pacific Time

Russ,

Your assumption is correct. While a GPS will indicate your speed over the ground, it does not indicate your speed through the water. A knotmeter indicates your speed through the water. To determine if you are making the best speed it is necessary to know your speed through the water.

If you are making 7 knots through the water against a 7 knot current, you speed over ground indicated by a GPS is zero. If you are making 0 knots through the water (hove-to) in a 7 knot current your speed over ground indicated by your GPS will be 7 knots.

Greg Baker
Charlotte, NC

Boat Name: Sea Sharp Minor

Model/Year: Catalina 22 - 1984 - Swing Keel

Hull No. 11823

Hailing Port: Lake Norman Sailing Club
09/01/2006 10:09 AM Pacific Time

I am having a hard time trying to figure out when I would care more about my speed through the water than my speed over ground. It seems like all that nasty correction stuff you have to go through with estimating currents, making velocity triangles etc. etc. and all the chance for error that goes with that is not what you would do given a choice. The GPS is like a navigator's dream come true because you don't have to do that stuff anymore unless you are really paranoid or are looking for intellectual challenges.
Chris Hadden
Newfane, Vermont, USA

Boat Name: no name

Model/Year: 1974 Catalina 22

Hull No. 3439

Hailing Port: Vermont
09/02/2006 6:42 AM Pacific Time

I have a GPS but no knotmeter. I have been thinking of getting a knot meter for the exact reason you were. The GPS does not react to speed increases very quickly. By the time you get the new reading your living in another moment. I don't see where the GPS is all that useful when you are trying to determine which sail tweak is correct for each puff or shift of wind.

Chris Hadden
Newfane, Vermont, USA

Boat Name: no name

Model/Year: 1974 Catalina 22

Hull No. 3439

Hailing Port: Vermont
09/02/2006 6:45 AM Pacific Time

Along this same line of though, does anyone use a transom mounted log? When I bought the boat I filled all the through holes. I don't like sailing boats with holes in them.
 
 
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Catalina Direct Discussion Topics / Catalina 22 Discussion Area / Racing / Speed Log