Sail power vs diesel

[Ross]

I have a very good pie receipe. But it can't be prepared in one

day. First buy a nice goose at the grocers and roast it with all of the things that should go with it and skim the fat as it cooks off. Invite four friends over and eat the goose. Save the fat in jars and store it in the refrigerator until the season for your favorite fruit pie comes around. Use some of that goose fat to make the pastry for the crust for that pie. I promice you that it will be the best pastry you have ever sunk your teeth into.

 

[sailaway78]

Old Guys

Ross,Only us old guys know how much flavor you get from things like goose grease, bacon grease and plain old lard. It may not be good for me, but damn it sure does taste good. There is no way on earth to make eggs taste better than to fry them in bacon grease.

 

[Timo42]

Pie are round,

cornbread is square!

 

[Ross]

TimO , Bad news !! ;D I make corn bread in a round iron

skillet. Fry some cut up bacon, heat the oven, mix the batter, pour it in on the bacon and the fat and pop it into the oven.

 

[Joseph Shirley]

Boy, It's been a long winter for everybody

and spring is late everywhere. When I graduated Engineering College 50 years ago pie was a squiggly picture on my slide rule somewhere between 3.1 and 3.2 and all i had to do was line it up with something. Do you really have to know all the numbers now?

 

[Ross]

Naw! They just pop up when you push the button on

your calculator that has that little squiggley thing on it. Just like the trig functions. three significant figures were good enough to build bridges but the calcumolater will give you eight or more.. ;D

 

[Jerry Clark H356 SV Persi]

In Tennessee

Pi are round and cornbread are square!

 

[ctalmage]

interesting....

Interesting calculations and great laughter. My first thought was where's Al from - he must be snowed in. But then again, I did read the entire thread so that puts me in the same boat. 40 dergrees here, raining, no way to work on the boat today.

 

[T37 Phil]

Winter pi

All wrong. A mathemagician would say that pi is the circumferance of a circle divided by its diameter. "Exact" numerical answers are for less pure folks. I once heard a rumour that the great state of Georgia tried to legislate the value of pi to be exactly 3.14. I wonder if that makes them mathematicians or engineers?

 

[Timo42]

I bet Georgians

don't try to put cornbread in round pans, some things are sacred.

 

[Paul Brinkley]

Pi did change over the years

or at least the value we use. When I was in high school, we used 22/7 until some of us smart***es got slide rules; then it was the little line described earlier. It stayed the mark on the slide rule while I was in college, even though we knew it was 3.14159blahblahblah. After I graduated, worked a few years, then went to teaching (instead of working ;D), pocket calculators came out that used 8 decimal places. With the advent of microcomputers, I can't even remember how many places are used. For most engineering today, 22/7, 3.14, or even 3.1416 would not be satisfactory. I used to have the occasional student who would argue that 3.14 should be good enough. My stock answer was (1) it was not good enough in my class because you were instructed at the beginnning of the class to use the value of pi from your calculator or computer; and (2) you can obtain a much more accurate value by pressing one key than by typing in 3.14, so why waste time and effort... *box -Paul

 

[Jim Kolstoe]

All Pi aside

I think the calcultion on sail force needs to account for the fact that the sail develops lift perpendicular to the sail's surface at all points. So if you are broad reaching (and she doesn't slap you) the sum of the forces will be mostly in the foward direction, propelling your boat that way. If you are close hauled, the forces, again perpendicular to the surface at all points, will be mostly to the side and slightly forward, forcing reliance on the underbody of the boat to resist those lateral forces and make going forward the easiest way to go. As of the value of Pi, make mine blackberry ala mode.Jim Kolstoe, h23 Kara's Boo

 

[sailortonyb Allied Mis]

Phil

Very Interesting. You didn't take one thing into account.Most of us use Pi to FIND the circumference. The circumference is much more difficult if not impossible to measure accurately without the use of specialized equipment. You can always use a cable and a marker to strike arcs and find the center of a circle. Once you have the center, you can easily measure the radius or diameter. Back in the old 20th century, when I was in high school we used a slide rule and the 1% accuracy of the slide rule was sufficient. Back then, most manufacturing processes couldnt do much better than 1%, or in fact, need to. The same holds true today for most processes unless really critical figures are required. In sailing, look up the specs for rope for example. There are the figures of minimum breaking strength and average breaking strength. The minimum is usually somewhere around 80% of the average. That is greatly less accurate than the 1% accuracy you can get from a slide rule.Take electricity as another example. How accurate must the gage of wire or the value of the electrical components in appliances be when your house voltage can vary between 110 and 120 volts. Thats also way more than a 1% variation. Engineers may be less pure folk, but we got the job done. Anyway, this is all tongue in cheek, so dont take it serious. I have way too much time on my hands today. Im waiting for someone to hoist me up the mast. regardsTony B

 

[GuyT]

No heeling force?

n.m.

 

[RichH]

heeling force is a 'reaction' and doesnt need to be defined ....

The boat is considered a 'free body' and only the force to 'move it' (against friction of the water) is considered.The nice thng about physics is that there is always TWO or more to arrive at the same answer. Another way to do this is simply define the mass (weight divided by the acceleration due to gravity) and put it into the *energy* equation of 1/2 (mass) times (velocity) squared. This assumes that the potential energy is zero. Pure and simple, and since the boat is a free body, the friction of the water is the sole reaction. The force to overcome friction can be backed-out to define horsepower, or killowatt-seconds or any other expression you want it to be.