Maritime mythbusters

[mattyboy]

seems our hobby is surrounded by myths and legends or are they facts????

can you tell the difference ???? go ahead answer a few i'll start off add in

if you call fact please give an explination


red sky in morning sailors take warning
red sky at night sailors delight fact

on sunrise if the sky is red that is moisture in the air reflecting like a prism and the sky turns red this moisture now heated thru the day by the sun leads to storms
if the same happens on sunset the moisture is not heated all day by the sun but has a chance to disipate durning the cooler night


size doesn't matter, it is the motion of the ocean myth ask any woman ;)


a left hand rotation prop is faster than a right hand rotation???


a x 18 is faster than an 18 2+3 with identical setups??

in salt water your faster than fresh???



;)

[Tony]

a left hand rotation prop is faster than a right hand rotation???

This is a fact in the northern hemisphere, but in the southern hemisphere it is the opposite.


a x 18 is faster than an 18 2+3 with identical setups??

Fact, because of the aerodynamic properties of the flared foredeck and hatch thereby providing bow and stern lift.


in salt water your faster than fresh???

Fact...more bouyancy in salt water.




:beer:

[Carl C]

Six foot sea........Let it be

[Morgan's Cloud]

How's about

'Never go fishing on Good Friday'

and

'Never ever take bananas aboard a boat'

(of course , don't forget ... never change the name of your boat while it's in the water)

[HOWARD O]

[QUOTE=Morgan's Cloud;498735]How's about
'Never go fishing on Good Friday'

MYTH

'Never ever take bananas aboard a boat'

FACT!

(of course , don't forget ... never change the name of your boat while it's in the water)

I thought you were to never change the name of a boat at all?


Disaster will follow if you step onto a boat with your left foot first.

A naked woman on board will calm the sea.

[BlownCrewCab]

A naked woman on my boat allways caused waves to exude from the boat:D

[hardcrab]

Aluminum 12oz. cans leave the dock full,


- but return EMPTY !

thats just WIERD.

[Morgan's Cloud]

Aluminum 12oz. cans leave the dock full,
- but return EMPTY !
thats just WIERD.

You do understand that remark is even more significant that you probably first thought ? ? :D

[VetteLT193]

We were skunked one fishing tournament. This particular one was big $$ and we had a big group go in on the total cost of the tournament + fuel.

Late in the day one of the guy found bananas on board and went ape shiat. He tossed those suckers overboard so fast it would make your head spin. I thought he might set them on fire before tossing them he was so mad, and raving about the bananas thing.

It didn't ever stop me from bringing them back on board again... or catching fish with them on board.

[VetteLT193]

Aluminum 12oz. cans leave the dock full,
- but return EMPTY !
thats just WIERD.

I actually found that the size of the aluminum container doesn't matter. I leave the dock with a big one filled with fuel and it's empty when we get back too :uzi:

[Ghost]

Aluminum 12oz. cans leave the dock full,


- but return EMPTY !

thats just WIERD.


I actually found that the size of the aluminum container doesn't matter. I leave the dock with a big one filled with fuel and it's empty when we get back too :uzi:

This is hilarious--I think you guys are really on to something. (Just like Navin R. Johnson. "He hates CANS!")

[BigGrizzly]

Hey tony on the salt water thing does the buoyancy thing over rule the higher drag of the denser water on the boat and lower unit.. As for the hemisphere look at a drain it swirls opposite in Australia, I have witnessed it myself. As for faster drives I really find it hard to believe, if that were true then in Australia the right hand drives would be faster and in Peru it would not matter. Then would higher Rpm right hand drives be slower. Just wondering. BTW Left hand TRS drives are stronger, but because of gear placement not speed and that is why most of thoe race boats had lefties.

[Ghost]

Griz took a bunch of words right out of my mouth. I'll forgo a bunch of thoughts I had about water density, surface tension, buoyancy of a motionless hull versus the hydrodynamics of a hull at speed, drive drag, prop bite, etc. (My only conclusion was I didn't know how the numbers all shook out, but buoyancy alone seemed too simple to fully explain the answer by itself, and I would expect the other factors would matter, even if buoyancy won out in the final answer, which it well may.)

(As a side note, if it is not true that boats are faster in salt water, I suppose the myth might have been fostered in some ways by the elevation difference. Most people who run in fresh run in thinner air, sometimes a little, sometimes a lot. But as I say, I don't even know the real answer about which is faster, fresh or salt. I wouldn't be surprised at all if salt actually is faster.)

As for the hemisphere thing with the props, I don't think I get that at all. Admittedly I'm trying to recall this from physics more than 20 years ago, but the whole northern/southern hemisphere thing, Coriolis effect, has to do with the difference in rotational acceleration of stuff at different latitudes. Stuff near the poles is accelerating, due to the Earth's rotation, in a tight little circle relative to the stuff nearer the equator, which is accelerating more slowly in a larger, broad circle.

The reason (amazing as it may be) that a sink of water will tend to drain counterclockwise in the northern hemisphere and clockwise in the southern, is that the water on one side of the sink is at a higher latitude, nearer the pole than the other half of the sink, and thus rotating in a tighter path around the Earth's axis. As miniscule as this difference is relative to the size of the Earth, the acceleration difference between the two is enough to tip the scales in a lot of cases, when nothing else significance is entering the equaton.

The reason for saying all that was to explain that what is key is the relative latitude of the components in motion. Unless the prop were on a torpedo traveling up from the center of the earth, or down toward, it, it already feels like the plane of rotation of a prop is already wrong for Coriolis effect to enter heavily into the equation, as boats travel basically across the surface. Further, if it did matter, I'd think the direction of the boat would matter. Last, unlike the still sink of water, even if theoretically predicted, I suspect any Coriolis Effect on a boat prop would be essentially unmeasurable, completely overwhelmed by other forces. So, for all practical purposes, I gotta vote myth on this one.

[VetteLT193]

I've never experienced the drain thing myself but I've read that it's more a matter of the way the bowl is than the earth. I'd have to see it on my own to appreciate it I guess.

http://www.snopes.com/science/coriolis.asp

[onesubdrvr]

Interesting points about a RH vs LH prop in different hemispheres,....


Guess I'll have to go with a duoprop on the 16 just in case I find myself in the southern hemi :D

Speaking of duoprops,..... would they be the same speed in the two different hemispheres, or would the larger prop carry more speed?

Does engine rotation matter?

All points to ponder :D

Wayne

[mjw930]

a left hand rotation prop is faster than a right hand rotation???

I say it depends on the application, on 2 Factory 1 boats I helped set up 1 was faster LH and the other RH. The non-aerated hull ran faster LH, the aerated hull was faster RH. The LH boat was a pain in the ass to handle (engine torque and prop torque conspire against you in a modern single turning left handed) so for everything but the kilo's or flat water we ran a RH prop

in salt water your faster than fresh???

Again, it seems to depend on the boat. My Velocity and a friends Fountain were almost 2 mph faster in the Intercoastal than on a local lake (roughly the same altitude) but my Donzi is exactly the same speed on both.

[Ghost]

I've never experienced the drain thing myself but I've read that it's more a matter of the way the bowl is than the earth. I'd have to see it on my own to appreciate it I guess.

http://www.snopes.com/science/coriolis.asp

I gotta agree with you and slightly disagree with snopes here, in the following way. I have not experienced it myself. My reaction was exactly what you say above, and I still believe that. A toilet, for instance, in particular, would tend to launch a bunch of water in whatever direction, based on the geometry of the porcelain, in particular, the jets.

When I was taught physics, the notion was that you needed a decent sized basin (probably circular), with a very small drain, right in the middle. Then, you needed to let it sit for a day or two, to get things totally still. Sinks, and toilets, I would think, would often create much larger force just from the mechanism of pulling the drain or starting the flush. The key being that the effect is there, and it is necessary to create conditions where nothing greater is exerting an influence. The snopes "debunk" seems to rely on little more than what I have seen in other texts pointing the other way, and their note about the "flow of water" is precisely what the physics I read suggested needed to be eliminated.

Another example, which I know about and have friends who've both tried and filmed, is the balancing of eggs at the equinox. Works for a couple of minutes, and then they all fell over together. Again, I didn't do it, but I know people who did, and saw the pictures. Not proof, but I tend to think such macro-micro things may be real under the right conditions.

[hardcrab]

the balancing of eggs

I've seen this done on the edge of a spatula at the Japanese steak house.

[lee]

i would rather be at the dock wishing i was as sea than at sea wishing i was at the dock but i really want to know is the glass half empty or half full

[BigGrizzly]

This is kind of fun. I did have this discussion with my dad and he had us time my 16 on the measured mile on the bay then took it up to the lake same day and did it there too and timed it in both directions. there was no speed change however it was about 3 and a half hours apart. I would think a jet drive on a planning hull could be faster due to the captured drive with no other lower unit drag.

[Ghost]

I've seen this done on the edge of a spatula at the Japanese steak house.

I don't doubt that a bit. And the whole equinox thing may well be hooey, I don't know. I didn't think the part that is supposed to be hard to do is necessarily the balancing, which I'd think could be done any day. What I thought was supposed to be different was that a whole sea of balanced ones would be knocked over nearly together, but I openly admit I never thought through it to even know exactly why, much less tried it. And a cursory attempt at picturing of what I know about the Earth's movements doesn't yet explain the theory to me either. (In fact, quite the reverse.) I just know some people who tried it and took pictures and said things all happened as predicted, but I can't speak for the rigor.

Edit: the more I think about it, the harder I think it would be for almost *anyone* to get the time right. You'd need to do some real math based on your precise location, not just time zone adjustments, to know *when* anything was supposed to happen, if a 5-30 minute window was critical. This has me more skeptical all the time...

[BlownCrewCab]

but i really want to know is the glass half empty or half full[/quote]



If you where filling the glass and stopped at half...it's half full, If you where emptying the glass and stopped at half it's half empty....

[BigGrizzly]

Here is the answer to the glass question. If you drank it is half empty if you received it that way it is half full and you need to call the manager.

[gcarter]

If I did the math correctly, seawater is 3% denser than fresh water, but 7% higher viscosity. So I would have to guess saltwater would be slower, but I doubt you could measure it. Numbers that small mixed in w/all the variables of running a boat would be virtually impossible.

[gcarter]

I spent some time at 16* South Latitude, and you would see no real difference in which direction water drained. It was always a coin toss.
One thing I did notice was all the stars in the sky were different.