Trig Help

[El Pinguino]

Originally Posted by CruiseN

They look beautiful.
You an artist or something?
Eye herd sailing an art.



At which tide is clearance?
We get 2 metre tides down this way, I don't know where clearance is measured. Low Mark? 2 metre mark?

I'd check to confirm that.

If from a higher mark then you might be getting pretty close to zero heel with no antenna but no room for error and not an often practiced skill.

Just pros and cons. Not advising such.
I'd want error margins too.

Clearance heights are normally 'worst case'.... HAT, Springs High Water, Higher High Water or what ever is the case in your part of the world. Its supposed to be standardised globally but probably isn't. It will tell you on the chart in the title block.

[ChrisJHC]

Originally Posted by Spot

The trig of the Lodesman is working mighy powerful on CF :

Not to derail the thread, but wouldn’t that be much easier in metric?

I assume you calculated the result as “decimal feet” then had to convert into feet and inches?

[CruiseN]

Originally Posted by ChrisJHC

Not to derail the thread, but wouldn’t that be much easier in metric?

I assume you calculated the result as “decimal feet” then had to convert into feet and inches?

Doesn't matter because it's a ratio of a quantitative unit that determines the wave strength of cosine.

Aslong as unit measured remains uniform.

Eg feet over feet.

Me ta over me ta.

Units cancel and ratio to determine strength remains.

Just a look at an angle.

[TrentePieds]

Quote: "No protractor? Just use the compass rose on one of your paper charts."

Indeed!

Why get all knotted in the face over something so simple as the OP's "problem"? You've already got the compasses out, so just halve, halve and halve again a single compass span ( = radius) on the periphery of the circle you've already drawn a segment of. That's Grade X geometry, IIRC. You are then down to a 7 1/2º segment. Pick that up in the compasses and step off the distance from the Vertical along the circle periphery. You can eyeball the number of degrees within each 7 1/2º segment. That's close enuff.

What is it with this propensity for spurious accuracy ;-)?

While we are at it - the SI system of measurements is just wunnerful. If you are a microbiologist or an astrophysicist. If you are a practical man concerned with "stuff" that the human body has to use - like boats and houses - the old imperial system beats metric hands down every time :-)!

TP

[Spot]

Originally Posted by ChrisJHC

Not to derail the thread, but wouldn’t that be much easier in metric?

I assume you calculated the result as “decimal feet” then had to convert into feet and inches?

I drew the figures 'full size' in inches, moved and rotated them to slip under the bridge, and then added the dimensions formatted as feet-inches rounded to the inch. I did not calculate anything, other than switching feet to inches to draw the mast and antenna and bridge. The program does all of the heavy lifting including the math for the rotations and the dimensions.

[Nicholson58]

Run a 54 foot line to the top of the mast and force the heel until the line is in the water.

[requiem]

Originally Posted by TrentePieds

Why get all knotted in the face over something so simple as the OP's "problem"? You've already got the compasses out, so just halve, halve and halve again a single compass span ( = radius) on the periphery of the circle you've already drawn a segment of.

Halving is good, but since you have dividers I would suggest trisecting to get the 15, 30, 45, 60, and 75 marks. (Those are a bit more useful than the 22.5 and 11.25 marks.)

Originally Posted by TrentePieds

While we are at it - the SI system of measurements is just wunnerful. If you are a microbiologist or an astrophysicist. If you are a practical man concerned with "stuff" that the human body has to use - like boats and houses - the old imperial system beats metric hands down every time :-)!

I have a reading idea, should you run across a copy: https://lostartpress.com/products/by-hand-eye-1

It makes an observation that pre-industrial design was not so much focused on specific measurements, but on relative proportions. Having ultra-precise measuring rules might be considered a more modern invention, a sort of stepping stone that temporarily elevated the old units into distractions from the underlying design.

[CruiseN]

Down our way..
Our minimal clearance is measured at astronomical high tide mark.

Hence with out antenna vertical if mounting allows temporary stance horizontally to go without issues of wiring harness..
Low tide lots more under 3 feet gained if draft allows.
To improve depth, could always fresh water bilge temporary and turn pump on after ducking overhead.
Or about 17-18 degrees clears 57 into 54 feet, width ain't much beyond beam but eyes can view approach unless pile ons are narrowly placed.

I'd use the tide bro..
Wait for no waves.

Wind on luff usual suspect of heel, square area of cloth just gets blamed by those innocent of a decent clue.

Metric feet. Whoops.
Imagine the first four mathematic dimensions.
Point, line, shape, time.

Then dimensions five and six, energy and mass are with a stable base.
Mass with energy, that's momentum.. safe passaging.

[Lodesman]

OP indicates location is Florida. On US charts vertical clearance is from Mean High Water (MHW).

[CruiseN]

Originally Posted by El Pinguino

Clearance heights are normally 'worst case'.... HAT, Springs High Water, Higher High Water or what ever is the case in your part of the world. Its supposed to be standardised globally but probably isn't. It will tell you on the chart in the title block.

That's what I thought too.

[MicHughV]

Yes, running a line, 54' in length...from the top of the mast ( after removing the antenna) and heeling the boat over until the bottom of the line touches the water, is likely the easiest and simplest method to determine bridge clearance.

Hanging a heavy weight from the top of the mast (eg. anchor chain and anchor) would apply the longest possible lever arm to use.

One can go online, and view any number of buoyancy, center of gravity, facts and figures, determinations. etc.

But...lest one forget...the more the boat heels over, the more of a lever arm the keel will provide. Initial heeling will be easy to obtain...but it will get more and more difficult as the boat heels over.

Which, brings up another point. It doesn't matter by what method the heeling is induced, but it should be solidly fixed in place, as you do not want something falling off or breaking as you pass under the bridge, as the mast will spring up at a most inopportune moment.

For my money, I would push or pull the boat thru', and not use the main engine at all....come to think of it......I probably wouldn't even try this...

One last option....probably the smartest...is to have the mast pulled and laid flat on supports on the top of the boat. This is relatively simple to do with any mobile crane...and then re-install the mast after. Same crane can do both operations.

Were it me, that is what I would consider.

[Be Free]

Don't forget to check for horizontal clearance as well. Your boat is going to be a lot wider while it's heeled over like that.

[CruiseN]

Originally Posted by MicHughV

Yes, running a line, 54' in length...from the top of the mast ( after removing the antenna) and heeling the boat over until the bottom of the line touches the water, is likely the easiest and simplest method to determine bridge clearance.

Hanging a heavy weight from the top of the mast (eg. anchor chain and anchor) would apply the longest possible lever arm to use.

One can go online, and view any number of buoyancy, center of gravity, facts and figures, determinations. etc.

But...lest one forget...the more the boat heels over, the more of a lever arm the keel will provide. Initial heeling will be easy to obtain...but it will get more and more difficult as the boat heels over.

Which, brings up another point. It doesn't matter by what method the heeling is induced, but it should be solidly fixed in place, as you do not want something falling off or breaking as you pass under the bridge, as the mast will spring up at a most inopportune moment.

.

Were it me, that is what I would consider.

Plane stability.
Pic from Hurricane Nate.
Zombie Island.
Off of the 'net

Beyond plane angle is alot lot more effort.
Pre passage preparation could determine height on heel using mast head hanging measured line of 54 feet?

Nice looking boat. She a heeler? Do you know that angle? Blue arrow.

Because chine (orange arrow) will be working it's best to avoid anything further than a simple plane angle.

Nice looking boat sir. I know you know your vessel. I'm just guessing difficult to achieve pictured angle because of inability to lift keel. Beyond keelson to hard chine angle would be starting a much more adventurous rotational torque.

[TrentePieds]

Quote: "Having ultra-precise measuring rules might be considered a more modern invention,..."

Thanx, requiem :-)! That is precisely (ahem!) the point.

My father was an architect. HIS father was a builder of the old school. Grandad was able to make the pieces for, and set up, a winding stair using nothing but a plumb line and an old-fashioned carpenter's folding rule. Marked in Danish inches. No pencils, please! Use a marking knife :-) And being Danish, he disparaged the notion that the yard is a useful measurement. The PROPER measurement is the el - TWO feet, if you are Danish. Something else if you are German or Dutch. Let alone 'Murrican :-)!

On visits to my parents, I'd take time to go to a local lumberyard and find a "sales associate". I would ask: "How big is a sheet of plywood?" "Uh,, uhm.. It's 1,219 mm by 2,438 mm.", the brighter ones among them would answer. Others, not so bright, would look at the stamp at one corner of the sheet before answering. "What the hell is the use of a measurement like that?" I'd say. "How can you possibly use a queer measurement like that for a module?" I'd ask. "What do you mean, Sir?" would be their response.

"Never mind" I'd say. "Thanks for your time"

No need to tell them that what they sold in that distant land was fourbeeight sheets made in the mill just down the road a mile from my home in a Vancouver suburb :-)

I hadn't come across the book you suggest. I'll get one. Obviously grist to my mill :-)!

TP

[CruiseN]

Originally Posted by TrentePieds

Quote: "Having ultra-precise measuring rules might be considered a more modern invention,..."

Thanx, requiem :-)! That is precisely (ahem!) the point.

My father was an architect. HIS father was a builder of the old school. Grandad was able to make the pieces for, and set up, a winding stair using nothing but a plumb line and an old-fashioned carpenter's folding rule. Marked in Danish inches. No pencils, please! Use a marking knife :-) And being Danish, he disparaged the notion that the yard is a useful measurement. The PROPER measurement is the el - TWO feet, if you are Danish. Something else if you are German or Dutch. Let alone 'Murrican :-)!

On visits to my parents, I'd take time to go to a local lumberyard and find a "sales associate". I would ask: "How big is a sheet of plywood?" "Uh,, uhm.. It's 1,219 mm by 2,438 mm.", the brighter ones among them would answer. Others, not so bright, would look at the stamp at one corner of the sheet before answering. "What the hell is the use of a measurement like that?" I'd say. "How can you possibly use a queer measurement like that for a module?" I'd ask. "What do you mean, Sir?" would be their response.

"Never mind" I'd say. "Thanks for your time"

No need to tell them that what they sold in that distant land was fourbeeight sheets made in the mill just down the road a mile from my home in a Vancouver suburb :-)

I hadn't come across the book you suggest. I'll get one. Obviously grist to my mill :-)!

TP

Yeah exactly..
Hanging line or chain of known marked lengths heeling on stability of plane.
Any lower and you're forcing the gap.
You all sail. Heavy sheets are great, forced sheets suck bad.

Hence impression here is OP was mathematical model requesting to compare with plane.
Whereas practical trig. Hang a chain.
Hoping your deep keelson too bro. Sure looks like a beauty.