Yacht design the hard way. learning from Kav800 (most beautiful boat EVER...etc LOL!)

I think it is the Fn number. Sorry for not being specific

EDIT:: it just says it is the resistance curve It is the long curve that goes from stem to stern and way above the deck. In the center it says 0.27

 

There are a lot of numbers that pop up in FreeShip; please identify the name of the window that dispays them.

 

The picture I attached is of the profile view. The very top number is what I'm talking about. It is at the top in the center. above a long red curved line.

 

Here it is simply largest submerged area of section.
It has nothing to do with Froude number or resistance value.

 

Schoonner: I didn't see your post until I posted mine.

Some observations that may be useful:

The stations are spaced 1 foot apart, and if you add all those number up and multiply by the waterline length, then multiply by the weight of 1 cu ft of water you will get the displacement or very close to it. I noticed the metacentric height (FreeShip labels it KM *) isn't shown in your picture, I'm not sure why as FreeShip displays it at the time as the other hydrostatics are displayed (enabled/disabled under the Visibility menu). KM is a measure of primary stability; briefly, if the center of gravity of the loaded boat is below KM it will float upright, if not it will start to roll.

A measure of secondary stability or the righting moment of the hull when heeled is provided by the Crosscurves tool under the calculations menu of FreeShip.

* the "K" merely signifies that it is measured from the keel . . .

 

This is NOT metacentric height.
It is a vertical position of metacentre itself (from the base line of particular model).
To get metacentric height, vertical position of centre of gravity have to be considered: if CG is above the base line, it should be subtracted from KM, if below, - added to it.
Difference is really big even for heavily ballasted sailboats, and huge for motor ships without external ballast.
KM would be equal to metacentric height only if CG is exactly on the base line.
Had a discussion on the topic at work recently .

 

Maybe it is not showing up because something is wrong and it can't be calculated. Can I change the draft once it has already been acquired?

Also, I wish there were more reference points like this:

Stability characteristics:
Test stability coefficient : 2.008 if >= 0,8 then OK

I assume that this means that if the Test stability coefficient is higher than 0.8 it is fine. Not sure why there is a coma in there. For the rest of the stuff I have NO idea if any of it is good.

 

- correct, sorry, darn, done it again. I'm always getting that one wrong - in my (former) line of work height was always referenced to baseline and of course GM is the metacentric height!

 

Okay, I'm giving up for a while. I don't know what I did, but freeship has some floating point error and crashes when I load the boat. FAIL!

Since there is always another aspect of boats models and whatnot I'm working on sails for a while. =0)

Are sails with the maximum draft 25% efficient in a smaller range than sails with draft at 45% chord?

I'm guessing that a glider is a good example of what a sail lift will be like. A glider wing with draft at 25% will have close to the same glide ratio as one with 50 %, but the one with draft at 25% will stall at a the same speed unless it is in rough air. Rough air makes it sink faster and the range of airspeed is better with a 50% draft round camber wing of the same size and shape as one with 25%draft.

Therefore, if sails DO work like this then I think I want to cut sails with draft at the max draft % that I can with my program which is max draft at 46% with a gentle circular cross section.

 

FreeShip creates a backup file of the previous version when you save a new version. Rename it and change the extension to FTB and it should load; then you will only lose the last thing you changed.

 

Glider wing work at angle of attack between 2 and 4 degrees.
Sail work between 15 and 90 degrees.
Nothing really comparable here.

 

Also, at so small size, sails work at Reynolds numbers incomparable to those of full size sails, let alone the glider wings.

 

Okay, so with reynolds numbers in the 100 thousands instead of millions they have to be made differently?

 

What reynolds numbers do boats of my size have? It can't be much. I imagined that they would be like an RC airplane.

Oh, and what I posted earlier, was out of the file generated by Free!Ship under calculations and then design hydrostatics.

Is this correct?

"Moving your draft further forward allows you to generate more drive in the sails and tolerate a higher angle of attack, but at the expense of pointing."