Myth busters

[Scott T-Bird]

The laws of physics!

http://m.imdb.com/title/tt0104952/quotes?qt=qt1653289

I love this part ...

 

[Daveinet]

Sustained speed in flat water???

This pegs my BS meter.

Pictures or it isn't true.

That boat has a ton of overhang on the stern, so the waterline is heeling dependent - looks like by several feet. There is at least one decent YouTube video of one under sail in a solid breeze. You can see the wave build up at the bow, so I don't think it will cheat hull speed by much.

In contrast, my boat, which planes easily, there is almost no bow wave at hull speed. Displacement to planing has no transition, the boat just goes faster.

 

[Jackdaw]

That boat has a ton of overhang on the stern, so the waterline is heeling dependent - looks like by several feet.

I agree with your other points. To this point, the square root function is the great humbler of numbers. Even if you were to use the LOD overall hull length and not the LWL, the speed difference is less than 1/2 a knot.

 

[Bob Cronin]

"One more tack should do it"

 

[All U Get]

"I'll be right over to give you a hand"

All U Get

 

[Daveinet]

I agree with your other points. To this point, the square root function is the great humbler of numbers. Even if you were to use the LOD overall hull length and not the LWL, the speed difference is less than 1/2 a knot.

Stupid math just kills the imagination LOL

 

[Jackdaw]

Stupid math just kills the imagination LOL

I know. I just hate it when reality intrudes! ;^)

 

[Joe]

You have to ask why it is THEORETICAL Hull Speed.... rather than the LAW of Hull Speed Theory?????

The myth is NOT the theory, which is a simple formula for determining optimal power application for a full displacement hull vessel.

The myth is that people think the theory is an absolute law of physics...

 

[Stu Jackson]

The myth is that people think the theory is an absolute law of physics...

Or......

The myth is that new-to-them skippers will NOT ask how fast their boat can go!

 

[Sandy Stone]

And really, the formula as given is an oversimplification, if you consider that a Hobie cat flying a hull going 12 knots is still in displacement mode. There should be a term in there for length/beam ratio, probably disp/length ratio, etc.

 

[walt]

No, theoretical hull speed is exact. You can neither go slower or faster without warping time.

 

[justsomeguy]

Cue "Twilight Zone" theme.

 

[Jackdaw]

 

[Jake N Eggs]

This is one of my favorites and I actually believed it, due to how credibly it was taught me, till my cousin Rick, who is ABYC in yacht electrical systems, asked me why on earth that should make any difference; and I had to think about it.

Still don't know why it's so important to take the negative lead off before the positive one, though. As long as you don't bump something against the wrong other something, you should be okay... right? (I acknowledge that's a big 'if'.)

In a negative ground system the chassis is ground, assuming of course that the chassis is metal. If the negative cable is removed first the chassis is no longer at negative potential. If you touch the chassis with the wrench, while removing the positive with the negative removed, there is no opportunity for a spark.

The spark is an issue for the wrench but more importantly, the spark can ignite the battery gasses causing the battery to explode. This is more likely when the battery is older or dead. Usually when you want to change the battery.

It is a best practices procedure.

 

[Bernd Minde]

Myth # Infinity...

"Don't worry about a thing!"

Sailing is just like fun... Only different!

 

[All U Get]

Re: Myth # Infinity...

And the one you'll never hear "I'm done with my rant"


I filled the spare tank

All U Get

 

[Tom J]

"This could get interesting …."

 

[Tom J]

In a negative ground system the chassis is ground, assuming of course that the chassis is metal. If the negative cable is removed first the chassis is no longer at negative potential. If you touch the chassis with the wrench, while removing the positive with the negative removed, there is no opportunity for a spark.

The spark is an issue for the wrench but more importantly, the spark can ignite the battery gasses causing the battery to explode. This is more likely when the battery is older or dead. Usually when you want to change the battery.

It is a best practices procedure.

Also taught by the U.S. Air Force.

 

[Kestle]

Flyin baby..

Did somebody lose a bet and shoot the chart table?

Jeff

 

[Kestle]

I've got all of you:

"OK, just one more beer..."

Jeff