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Old 19-12-2017, 10:39   #46
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Re: International Micron 66

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Originally Posted by Kenomac View Post
On post #37 you calculated 10.9 knots, and now we’re up to 11.4kts... on our way back up to 12-13 knots like Comanche as in post #3.

Maybe it’s the Micron 66.
Ken, 10.9 over ground and 11.4 through the water. That is pretty simple math and was clear from the very first post on the subject for anyone who thought about it even for a couple of seconds.

As to Comanche -- I think you used this as an example of a boat which can go 13 knots. But Comanche goes 40 knots -- triple her hull speed -- and can average 20+ for days at a time. Beowulf -- with a hull form quite like mine, but much lighter -- goes 27 knots. You experience hull speed as a hard limit on your very heavy boat and you don't want to believe that it's different on other boats ("laws of physics"). Well, it is not like that on lighter boats, and it's not like that on boats with finer hulls, like catamarans. You can believe it or not as you like, of course, but it's a fact.

I believe your mind is closed about it, but for the benefit of anyone else who is curious about it -- hull speed is nothing other than a steepening of the curve which represents power versus speed. There is no one point on that curve -- like the sound barrier, for example -- where you just suddenly can't accelerate any more -- it just takes more and more power. So hull speed is not really a point, but could be better thought of as a band of speed during which power required to go faster increases disproportionately.

On heavy and tubby boats, that steepening is very sharp. On lighter or finer boats, the steepening is shallower and is not experienced as much. Very fine and very light hulls experience it almost not at all, and planing hulls of course are something different again. In general, by the time you get to about 200 D/L, on cruising boats of average beam etc., one knot above theoretical hull speed becomes reasonably achievable in a brisk wind. A very heavy boat, on the contrary, will find it hard to get even to theoretical hull speed -- by one knot below theoretical hull speed, there is already a serious increase in power required going on.

Over long distances, it is hard to average more than theoretical hull speed minus one knot, even in very good conditions, on just about any boat other than the very light (something like a Pogo, or TJ's Rocket Science) and very fine (performance catamaran). And over about 100 Channel crossings, one knot below theoretical hull speed is in fact my average -- 8.3 knots. Prevailing winds make that often a beam reach, so those are really good conditions compared to average passage making around here. In more normal conditions including some running, sailing hard on the wind, sailing in light winds, the average speed is much less than that.
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Old 19-12-2017, 12:03   #47
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Re: International Micron 66

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Originally Posted by Dockhead View Post
Ken, 10.9 over ground and 11.4 through the water. That is pretty simple math and was clear from the very first post on the subject for anyone who thought about it even for a couple of seconds.

As to Comanche -- I think you used this as an example of a boat which can go 13 knots. But Comanche goes 40 knots -- triple her hull speed -- and can average 20+ for days at a time. Beowulf -- with a hull form quite like mine, but much lighter -- goes 27 knots. You experience hull speed as a hard limit on your very heavy boat and you don't want to believe that it's different on other boats ("laws of physics"). Well, it is not like that on lighter boats, and it's not like that on boats with finer hulls, like catamarans. You can believe it or not as you like, of course, but it's a fact.

I believe your mind is closed about it, but for the benefit of anyone else who is curious about it -- hull speed is nothing other than a steepening of the curve which represents power versus speed. There is no one point on that curve -- like the sound barrier, for example -- where you just suddenly can't accelerate any more -- it just takes more and more power. So hull speed is not really a point, but could be better thought of as a band of speed during which power required to go faster increases disproportionately.

On heavy and tubby boats, that steepening is very sharp. On lighter or finer boats, the steepening is shallower and is not experienced as much. Very fine and very light hulls experience it almost not at all, and planing hulls of course are something different again. In general, by the time you get to about 200 D/L, on cruising boats of average beam etc., one knot above theoretical hull speed becomes reasonably achievable in a brisk wind. A very heavy boat, on the contrary, will find it hard to get even to theoretical hull speed -- by one knot below theoretical hull speed, there is already a serious increase in power required going on.

Over long distances, it is hard to average more than theoretical hull speed minus one knot, even in very good conditions, on just about any boat other than the very light (something like a Pogo, or TJ's Rocket Science) and very fine (performance catamaran). And over about 100 Channel crossings, one knot below theoretical hull speed is in fact my average -- 8.3 knots. Prevailing winds make that often a beam reach, so those are really good conditions compared to average passage making around here. In more normal conditions including some running, sailing hard on the wind, sailing in light winds, the average speed is much less than that.
Like I said, now you’re back up to claiming an 11.4 knot average over 30 miles on a Moody 54, 45,000pound cruising boat. Can Maxi racers with a flat planing hull like Comanche do it... yes, catamarans... yes, powerboats... yes, Moody 54... no. Totally not possible without a following 2 knot current... you need to start using gps or get your speedo properly calibrated. IMHO

I await your performance video.
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Old 19-12-2017, 12:18   #48
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International Micron 66

I am 33’ at the waterline and averaged over most of a day 8.34 kts (GPS) speed off the coast of Tampa Bay headed South, that is I think about a half kt. over my hull speed, and conditions were ideal. It has only happened so far that once, but if an overweight loaded IP with 30 yr old sails can bust hull speed, anything can
Since then I have new sails, but if anything are even heavier.

My best 24 hour run was over 250 Nautical Miles (GPS)




But that was in the Gulfstream that averaged about 4 kts current
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Old 19-12-2017, 12:31   #49
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Re: International Micron 66

A64....I had my finger on the BS button until the post script...funny.
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Old 19-12-2017, 14:05   #50
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Re: International Micron 66

Our Kaufman 47 sailboat can and has hit and exceeded hull speed. We were on a lake with a squall line off the distance so we had a stiff breeze pushing us with our, now gone, 150 genoa and the bagged out main at 8-9 kt on our iPad Blue Chart mobile app. If you don't want my word, read about Quetzal, John Kretschmer's Kaufman 47. He has exceeded hull speed and surfed it doing 13knt, which he said it gets squirrelly at that point.

Our boats are 41' on the water line and roughly 34k loaded I would say. I can exceed hull speed with our 75hp Yanmar 4JH4-TE at 9.2 GPS on a fresh bottom, light displacement(30k, basically empty boat)

Just our experience...
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Old 19-12-2017, 14:08   #51
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Re: International Micron 66

Also, unless you know exactly what the current is doing(buoy or shore based data) SOG by GPS is not an accurate means of measuring speed. STW, when calibrated correctly which isnt hard, is your only means of correct speed of vessel.

I'm pretty sure I'm not alone on this..
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Old 19-12-2017, 14:24   #52
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Re: International Micron 66

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Originally Posted by SailRedemption View Post
Also, unless you know exactly what the current is doing(buoy or shore based data) SOG by GPS is not an accurate means of measuring speed. STW, when calibrated correctly which isnt hard, is your only means of correct speed of vessel.

I'm pretty sure I'm not alone on this..
Nope, not alone! We often see GPS speeds quoted and view them as only approximate AT BEST in terms of STW.

Another anecdotal data point for Ken: We have repeatedly exceeded our hull speed of ~8.8 knots, sailing on a reach in flat water. Have exceeded 10 knots STW towing our 3.5m RIB, beam reaching in a sudden headland wind of ~25 knots true. Downwind at sea we frequently hit 12-13 knots surfing, and have on three occasions exceeded 15 knots. Most of these events have been wing and wing with poled out genoa. This is with a full cruising load, so our displacement is around 12 tonnes. I'm confident that if we were near light ship weight there would be a significant increment in speed.

Ken, I dunno why you are so obdurate about this. At least one independent witness has verified DH's claims, and several of us have reported similar sorts of experiences. I guess we could all be stupid and misinterpreting our data, or we could all be lying, but I kinda doubt either of those ideas. Maybe you should rethink your position...

Jim
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Old 19-12-2017, 14:33   #53
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Re: International Micron 66

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Originally Posted by Jim Cate View Post
Nope, not alone! We often see GPS speeds quoted and view them as only approximate AT BEST in terms of STW.

Another anecdotal data point for Ken: We have repeatedly exceeded our hull speed of ~8.8 knots, sailing on a reach in flat water. Have exceeded 10 knots STW towing our 3.5m RIB, beam reaching in a sudden headland wind of ~25 knots true. Downwind at sea we frequently hit 12-13 knots surfing, and have on three occasions exceeded 15 knots. Most of these events have been wing and wing with poled out genoa. This is with a full cruising load, so our displacement is around 12 tonnes. I'm confident that if we were near light ship weight there would be a significant increment in speed.

Ken, I dunno why you are so obdurate about this. At least one independent witness has verified DH's claims, and several of us have reported similar sorts of experiences. I guess we could all be stupid and misinterpreting our data, or we could all be lying, but I kinda doubt either of those ideas. Maybe you should rethink your position...

Jim
And maybe you should show us a video to back up your claim as well... Otherwise...I guess anything's possible on an internet forum.

But golly Jim..."Obdurate," that's a new word, I had to look that one up.
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Old 19-12-2017, 15:16   #54
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Re: International Micron 66

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Originally Posted by Kenomac View Post
And maybe you should show us a video to back up your claim as well... Otherwise...I guess anything's possible on an internet forum.

But golly Jim..."Obdurate," that's a new word, I had to look that one up.
Ken, not everyone shares your obsession with videos. I don't own a video camera and have no desire for such. But, if I did, what would it prove? A picture of an instrument showing some figure or other can easily be faked, as I suspect you would point out if such evidence refuted your beliefs.

Meanwhile, numerous folks seem to have experiences that differ from yours...

And "Golly, Ken" I'm not responsible for your vocabulary's lackings!

Jim
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Old 19-12-2017, 15:19   #55
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Re: International Micron 66

None of us "know" stuff that's outside our own experience. Sorry, Kenomac, we don't do videos. But if you're trying to call my Jim a liar in a polite way, it is not amusing, nor is it true. One of those 15 kn. through the water times, we were sort of out of control, but for others, this boat is a performance boat, not very heavy for her size for a cruising boat. Of course she surfs downwind, too. Our averages, still are below the 8.8 theoretical hull speed, but we do routinely see more in a breeze--9's, 10's, and 11's, mostly. Ymmv. Your boat is very different from ours. Dockhead's boat has been set up continually to improve its windward performance, and he's spent bunches to optimize his sails for his conditions. He's not misleading you, he's made his boat faster by spending $$ on it.

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Old 19-12-2017, 15:30   #56
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Re: International Micron 66

Nice review of the 66. Was wondering how it fared.

Sorry you have to deal with senseless barking from a pitbull.
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Old 19-12-2017, 16:01   #57
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Re: International Micron 66

I use Micron 66, up in a good harbor on Casco Bay. The Haraseeket(sp?) is fed by a river, but with eight feet of tide it gets flushed thoroughly twice a day.

Yes, this stuff is expensive. However, I used to get a biology experiment every time I hauled in the fall. Now, I've got a clean boat, and I seem to get almost two seasons from a gallon on my Bristol 32, which will exceed fifty knots with the new flux-gate capacitor and mechanically extending waterline that I have installed.
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Old 19-12-2017, 16:06   #58
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Re: International Micron 66

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my Bristol 32, which will exceed fifty knots with the new flux-gate capacitor and mechanically extending waterline that I have installed.
Is your mechanical waterline the new one with the ball screw, or the old style rack and pinion?
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Old 19-12-2017, 16:16   #59
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Re: International Micron 66

Ive been using Micron 66 for about 5 years now. I've repainted once (2 coats) and I need a new bottom this winter. I have an aggressive cleaning schedule - a diver does it for me about every other month. What can I say, I like a clean bottom!!

A few comments about boat speed. Yes, theoretical boat speed is significant, but there are other factors. Pretty much any sailboat will surf. I sometimes take my Catalina 400 out just to ride a few waves. It really cranks up the speed. Just like on a surfboard, you can work the wave to get more energy out of it. Also, if you look at a vector picture of the water motion on a wave you will see that it is a circle, net water movement =0. However, the water at the surface is showing a significant vector (movement) along the direction of the swell. A sailboat is in the moving portion of the water column. ( I remember a well written section of the text "Physical Oceanography by Ingorsoll which discusses this sort of thing). Surface foam can also add a forward vector, as well as lift. Bottom line: Sailboats can haul *ss downwind.
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Old 19-12-2017, 16:34   #60
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Re: International Micron 66

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Is your mechanical waterline the new one with the ball screw, or the old style rack and pinion?
Rack and pinion. The boat was built in '76, and has a ton (literally) of extra fiberglass. my little Yanmar just can't support the hydraulics required for the the new ball screw...
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