|Topic Review (Newest First)|
|07-24-2009 03:35 PM|
|sailingdog||I would be curious to see the max STW from the sailing instruments from that run... I seriously doubt it is anywhere close to 21 knots.|
|07-23-2009 07:40 AM|
The explanations above make sense , thanks, over the ground speed , it is then; sort of like the theory of relativity ;when you shoot a bullet at an oncoming train.
I was sailing at 8 knots and the ocean god took me up to 21 , what a thrill !!!
|07-23-2009 12:20 AM|
I don't doubt that ramminjammin hit 21 knots OVER THE GROUND, he gave the impression that he sailed that fast. In B.C. there are several places such as Seymour Narrows where the currents can reach 14 knots and this is possible to achieve. Hardly an accurate description of the Tartan 30's capabilities though. Based on my looking at Tartans from that era I think they are a good solid boat that of course has the same issues any 25 year old fibreglass boat does- leaking chainplates, soft deck possibly. and outdated equipment. It usually comes down to price and how capable and willing the prospective owner is at repairs.
Currently refitting a CS27
|07-22-2009 10:18 PM|
You beat me. I was going to suggest a tidal bore or river current of eight or ten knots.
I have a Pearson 31-2 with a rig and hull similar to a 80's era Tartan 31. Though neither is a true displacement hull at about 18 knots through the water, say being towed by a missile frigate, the suction on the hull would be so great and the wave trough established so deep either would be sucked below the deck line and submerge.
|07-22-2009 04:30 PM|
You can take GPS readings to the bank. They are a measure of the boatspeed OVER the GROUND and given enough current, enough of a wave to surf down in a semi-displacement manner...any speed over the ground is possible.
The speed through the water in a displacement boat is another matter entirely and is limited to 1.34* the square root of the waterline length...in this case, about 6.7kts.
Given the tidal currents in Rammin's neck of the woods, I think the 15kts is quite possible as I've been in currents myself that took me from 5kts to 14kts in a matter of seconds and even Tartan 30's can surf a bit!
|07-22-2009 04:25 PM|
|bubb2||I have a Garmin 76 also. The one with the altimeter! I get as much of a chuckle when it reads that I am -43 feet under sea level as I do reading about your 19kts.|
|07-22-2009 02:01 PM|
Is it a coiencidence that when i saw the 19 kt, i just happened to be sliding down a 30 foot swell towing a dingy that was on plane and threatening to take out the stern.
I always thought you could take gps speedo readings to the bank
anyway , the mystery continues, also the 19 and 21 were recorded on the gps i borrowed from the guy who sold me the boat, a different one.
The reading of 19, I recall , i was actually loking at the gps screen continuous speed readout and not the readout where it records the max speed hit. I was sliding down the face of the wave thinking, " this has to be close to that 21 it recorded earlier" , and seeing 19 on the screen.I am wondering if any other coastal sailors have experienced the same type of numbers ?
This Tartan is a competition model , designed and fitted out for Marblehaed racing
I am not sure what is going on , we were in fantastic sailing conditions , mostly steady 20 knots of wind , then some higher gusts. We were crusing at 8 knots on the flat so i dont think it is too unrealistic to pick up 7 more coming down a swell in a gust of 20 knots ?
I hope we hit those speeds for real !
the avg speed for the trip , includes motoring out of the LaHave River and then out to the coast, also motoring through the Halifax harbor to Bedford
I was seeing a steady speed of 8 knots on the screen under the small spinaker ! so as i said before put in a gust and sliding down a swell ?
i'll make sure i turn on my back up gps next time
|07-22-2009 01:55 PM|
|07-22-2009 01:27 PM|
GPS speed jumps around quite a bit--I always assumed that this was because your absolute position is only known to within 10 meters, and the error varies. If your device grabs two measure that vary toward each other, voila, you just got a burst of speed. And if it captures that as your Max, there you go.
As T37 said, the average would be the better number.
|07-22-2009 12:39 PM|
|T37Chef||Isnt that mathematically impossible unless you were doing as the photo above...I am not calling you a lair, just saying that even if the boat did 14+ knots at one point the AVG is much more telling|
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