CD 28 Hull Speed

[Neil Gordon]

That is why one can not accurately navigate in a fog using just a compass and a knot log.

No, but if you account for set and drift and refer to the chart, you can safely arrive at your destination. (I'd suggest using a lead line to gather additional data; no batteries required.)

Or is it that the destination safely arrives at you?

Question for the GPS wizards: Does GPS speed = speed over the ground (two dimensons) or the actual "air" speed (three dimensions)? A Cape Dory falling off a wave is not bound by waterline length.

[WaywardWind]

Darrell, John made no argument whatsoever. John -- fine writer though he is -- merely got desperate to maintain his belief is a very old "story" that has no basis in fact. John got desperate enough to state "displacement" hulls aren't displacement hulls if they "are lightweight enough". Nevermind that Cape Dory hulls, -- heavy displacement by any standard in the land -- regularly exceed the silly "max hull speed" dictate and do it for extended periods of time. Nevermind that square rigger ships of the 19th century regularly oversailed their "max hull speed" enough to drive the boats under water and sink 'em.

#2, you swallowed the fish hook whole on the "navigating in fog using a compass knot log" issue. Trust me, your statement to the contrary does not in any way "prove" the Theory of Relativity is wrong.

Regarding #2, I purposely made the (absolute fact) statement to make the point some people simply don't care what reality is if it varies from their "religious" beliefs. Darrell, my boy, you will never get that fish hook out of your mouth. You have convinced yourself it is not there. Therefore, there is no value in attempting to discuss science with you.

[WaywardWind]

Neil, in the days before LORAN and GPS, sailboats were frequently lost on the rocks due to sailors secure in their belief that "set and drift" was enough.

It wasn't, and it isn't.

A leadline was useful, as was the sounds of nav markers, seagull nesting sites, the smell of french fries from certain restaurant, the sounds of Interstate Highways, etc., BUT a just a compass and a knot log in fog was the "Hail Mary pass" of the day. Lots of boats went on the rocks. Lots.

To use an aviation example (to irritate Darrell's religious beliefs perhaps?), it is strictly forbidden to fly an aircraft in clouds using just a compass and airspeed indicator. In fact, such has been illegal for more than 80 years. It is also patently stupid.

Side note: Starting in 1920 (and up to the mid 1990's) and under international convention, ALL AM radio stations were required to announce their call letters and station frequency every ten minutes or less. This was specifically done to help ships at sea (later airplanes in the air) to locate their position when they could not see landmarks or the celestial sky.

[Neil Gordon]

Neil, in the days before LORAN and GPS, sailboats were frequently lost on the rocks due to sailors secure in their belief that "set and drift" was enough.

Actually, they were more often lost because they couldn't claw off lee shores in storms. They knew where they were; they just couldn't do much about where they were going.

Otherwise, they ran into difficulty (literally!) because of a lack of local knowledge. Eldridge gives a good example in its description of "the Graveyard," where both the flood and the ebb tide set you in the direction of the reef.

By the way, even with LORAN and GPS and with clear visibility, boats (sail and power) are lost on the rocks. That's a typical summer day at Woods Hole and it's all about set, drift and a lack of local knowledge.

[WaywardWind]

Most of the time, fog means no wind, so no lee shore to claw off of.

The belief that just a compass and a knot log is safe boating practices is commonly fostered by the old men in the US Power Squadron. Tain't so, however. It was, in fact, it is the "Hail Mary pass" in boating before LORAN and GPS.

Read some sailing mags printed before LORAN and see just how many, many boat went on the rocks. The accepted practice in fog was to toss an anchor overboard and wait for the fog to lift. Many people insisted THEY didn't have to, and their boats were lost.

Consider this. Your compass says you are heading 90* and your knot log says 1.75 knots. Where are you actually going?

Guaranteed, you're not going 90* if you are motoring, even in flat water (motorboats don't go where there are pointed). AND, if you are sailing, you're making leeway. AND, if the current is not EXACTLY as you guesstimate or is not EXACTLY the strength you estimate, you're going somewhere else.

In fact, it is not uncommon in a compass/knot log situation to be actually going sideways or even backwards.

The point is, you can NOT tell. Relatively, and all that stuff.

I'm going sailing.

[Dick Barthel]

Nice to have someone on the board who understands the theory of relativity. However, even Einstein ran aground more than once on the shoals at the mouth of the Ct river!

This seems more like a winter thread to me. It must be all the rain we're getting.

Dick

[mahalocd36]

Most of the time, fog means no wind, so no lee shore to claw off of.

You have apparently never sailed in Maine. (or most of New England for that matter). Very often it is surely windy enough to sail with fog all around. Sometimes sun shining directly overhead as well. It's strange, but shall we say, "fact". In that it happens, often, that we have wind and fog.

[darmoose]

I am going to new drop a slow-breaking, hanging curve ball into the mix, and then whack it out of the park into the upper deck.

Ask a hundred thousand people -- including most people on the Cape Dory owners site, which some claim is the arbiter of all things scientific -- if it's a proven fact Earth goes around the sun, and nearly all will look at you like you have three heads. Push those hundred thou people for an answer and, again, nearly all will tell you, Of course!

Nearly all? Nearly? Who the heck wouldn't agree?

Well, no physicist would agree. Nor would anyone else with an even rudimentary knowledge of the Theory of Relativity.

Huh?

Yeah, huh. Plain and simple, if two or more objects SEEM to be moving RELATIVE TO EACH OTHER one simply has no possible way to know which is moving and which is not. Not if the speed of light is constant (and it is)..

Dear Windy (very appropriate moniker, by the way),

You fancy yourself as slippery as an eel covered in KY jelly, and it seems you may suffer from a form of ADD. Better have that checked out.

I definitely didn't mention a word about "navigating in a fog" as it was too silly to even comment on. I did however challenge your effort to impress the hell out of us with your assertion as to what physicists believe about whether the Earth moves around the Sun or vice versa. Seems you forgot there are several other planets within our view, making our observations and conclusions regarding your erroneous statement absolute and in no way in doubt, theories of relativity notwithstanding.

You never discussed that question with any physicists did you?? You just made that up to try to impress us wee little people on this little old board, didn't you. (shame on you)

I also love your continued effort to convince us that the answer to the propeller drag question lies in aeronautics. Nobody yet has challenged the results of the Strathclyde Ocean Engineering nor the M.I.T. studies, and you're no different. Seems AVOIDANCE is your best move, which I understand and don't blame you for.

You are definitely right about one thing, though, discussing science or reality with you does not seem to be in the stars. (astrology reference for your benefit), nor fruitful.

Darrell

[Dick Barthel]

Actually, I was expressing the scientific version, but that's okay.

There are people who feel if God intended man to sail fiberglass boats He would have made fiberglass trees.

George Carlin had a routine where he posited that mankind's only purpose is to produce plastic.

[M. R. Bober]

When I saw the Vigor was "performing" science I became interested, add in the mixed arenas of aero and fluid dynamics--to say nothing of the laws of physics--and ergo this post.

Forget everything you thought you knew about the parallels of flying a plane and sailing a boat. I have personally piloted my former Catalina 22 at a speed of more than 60mph (approximately 69 knots) while this was accomplished with the assistance of a vehicle and trailer, none-the-less, it equates to an approximate water line length of more than 2500 feet, which would be correct for the Catalina 2500, not the 22.

One more thing, where does the sun go at night?

Mitchell Bober
Sunny Lancaster (where if something has happened, it is possible,) VA

[WaywardWind]

I did that just to see what the self-ordained, self-proclaimed High Priest of The Seventh Pentecostal Church of Enlightened Superstition might say next. Last I heard he had proclaimed it a dogma of True Believers taken on faith that Hobie Cats are hydro-planing hulls, and anyone who didn't believe would suffer eternal flames and cold coffee from McDonald's drive-through.

[M. R. Bober]

I did that just to see what the self-ordained, self-proclaimed High Priest of The Seventh Pentecostal Church of Enlightened Superstition might say next. Last I heard he had proclaimed it a dogma of True Believers taken on faith that Hobie Cats are hydro-planing hulls, and anyone who didn't believe would suffer eternal flames and cold coffee from McDonald's drive-through.

Do you think--upon reflection--that your post could be edited or deleted?

Mitchell Bober
Sunny Lancaster (where we can depend upon the kindness of strangers,) VA

[Ldybg]

Dude, lighten up your beating up Kerrydeares granpa's dead horse

My 28 has occasionally gone faster than 6.3 kts, whatever that means, but it does make me happy, which is all I care about.

[WaywardWind]

Ldybg, I have no doubt your boat has exceeded "hull speed". Virtually all sailboats designed in the last 90 years can do so, and have done so. And 19th century cargo sailing ships regularly did it, and did it over well extended periods of time.

[WaywardWind]

Mitchell, the answer to your leading question is that the very existence of your question means YOU are saying Hobie cats are hydro-planes, "because of the Laws of Physics, a displacement hull Hobie is not capable of exceeding hull speed" i.e., going as fast as it clearly does.

Mitchell, science is science and superstitions are superstitions. If the Emperor has no clothes, the Emperor has no clothes. There is nothing to be learned by anyone by the insistence the Emperor's clothes are very fine grade of air. History shows the Emperor caught a very bad cold.

Science is science, superstitions are superstitions.