I recently purchased a Garmin handheld GPS and have used it the last three times I was out. Haven't had any reallly windy days yet but on the one day was getting 18.2 MPH peak speed out of my Pindle 18 with inexperienced crew (crew wieght of about 390 lbs) with about 13 MPH sustained winds. Was curious about what peak speeds other type of boats are getting.
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Scott
ARC 21
Prindle 18
Annapolis, Maryland
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GPS speeds
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Posted: Jun 13, 2012 - 12:23 PM
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Posted: Jun 13, 2012 - 02:15 PM
Peak speeds are unreliable because the GPS can lose signal for a brief time and then recapture, basing your speed inclusive of the distance traveled but not the correct time lapsed. This is a common weak point of the currently available handhelds.
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Posted: Jun 13, 2012 - 05:47 PM
that sounds quite possible on an 18' cat
but to confirm gps speeds you really need to download the track to a computer and look closely at the speeds just before an after the peak speed to confirm it wasn't a random spike
ie 13, 14, 14.5, 15.2, 15, 14.8 13.9
is probably true your top speed was 15.2 knots
13, 14, 14.5, 18.9, 10, 14.8, 13.9
the 18.9 looks a little dodgy as the boat couldn't really accelerate and decelerate like in about 3sec
plus there are other complications i forget now about "top speed" shown usually being a doppler speed rather than a track speed calculation -
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Posted: Jun 14, 2012 - 09:40 AM
I was wathching the GPS and the speed did not jump. Was mainting speed in that area prior to the peak speed so I feel it was accurate. What I really wanted to get a handle on was not that my speed was accurate on not. I was interested in getting a feel for what type of speeds different cats max out at. In example are I-20s peaking at 25 MPH?
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Scott
ARC 21
Prindle 18
Annapolis, Maryland
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Posted: Jun 14, 2012 - 11:57 AM
i heard of a Dart 20 sucked up by a water spout. Was doing around 65 mph. -
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Posted: Jun 14, 2012 - 12:06 PM
Now the real answer:
Max beach cat speed are around 25 knots. You can go faster in puffs and storms, but at that speed you (typically) are in survival mode and not worried about going faster.
if you are good, and know how to capitalize and maximize your speed (to increase your vectors / apparent wind, etc ) you can probably get 20-30% increases in your speed over true wind (at 10-18mph range. it seems to me above that range you have lots of drag and cavitation working against you).
high performance race cats (f18's/f16/n20's, etc) typically can do even better
World Class America's Cup cats can do about 1.9 times the wind speed (this was true for the last America's Cup cat - Alinghi 5)
The next America's Cup AC72 is designed to be able to fly a hull in 5 to 6 knots true wind speed, with a maximum over-the-water speed expected to exceed 30 knots. (not bad for a cat that will displace approximately 15,500 pounds)
the BMW/Oracle (tri) published reports have put the trimaran (that carries a mainsail twice the size of a 747 wing) with a top speed of more than 40 knots.
Edited by MN3 on Jun 14, 2012 - 01:52 PM.
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