Figure out the Figures

I think it is a little absurd calculate the displacement of the boat if you do not know at what draft and trim must be calculated.
Speaking of ballast in the keel without knowing the total displacement of the boat, the length of the keel, sail area, heel should take the boat and wind speed, is a bit risky. We can work on that to give a totally incorrect data.

 

Thank you all, I think I learned something, the pieces are coming together.

Free Ship calculates from stern to bow, the original data was from bow to stern, seems there would be a standard acceptable practice?

I can't read the data sheets posted, so I could only follow the comments.

Fairing seems to be the interpolation process to make slight adjustments between points or several points, is that right or close? Seems to me if values were taken off from a design, they would represent that design accurately and no adjustment would be necessary unless the design were adjusted. If you begin by setting values to develop a design, numeric adjustments would be necessary to adjust the design for other requirements.

I didn't get to take design 101.

And not to take this further off topic, but...

TANSL, as to your ballast comment, how do you estimate wind speed at the design stage, is that a statistical value of historic wind speeds for a geographical area, +/- ?

Sorry to slow you guys down, just trying to learn the numbers side.

 

I have no idea how to estimate this parameter but I have no doubt that it is one of the factors that the designer of a sailboat must consider.

 

I don't want to kill this thread, but will say I'd think a sail plan and design consider the forces as a variable not so much as an initial design parameter and the ballast then required. Otherwise, To me that would be like designing a car from the tires to be used.

Anyone as to the lofting issue and standards?

 

@Wavewacker,
Let me try to answer you with my layman knowledge and experience.
" Free Ship calculates from stern to bow, the original data was from bow to stern, seems there would be a standard acceptable practice?"
I believe the standard, is the way that Freeship wants to calculate. The exception is the way that the designer of the boat went about his presentation.
"Fairing seems to be the interpolation process to make slight adjustments between points or several points, is that right or close?"
When designs were made on a table, there was a technique of fairing between points using a bendable material and weighted blocks. Today the computer software can calculate the fairing of a curve between reference points. Each station of a boat design providing a "slice" of the hull profile at that point. The idea is to lay a material such as wood planking over the hull sections, producing a smooth transition between stations. With todays computing power, the best way is to provide a design in 3D software, then have it transferred to a CNC Milling program and have a plug(male mold) made. From there a female mold can be made and then Hulls can be manufactured.
"TANSL, as to your ballast comment, how do you estimate wind speed at the design stage, is that a statistical value of historic wind speeds for a geographical area, +/- ?"
Within todays Boat Design Software there is the means to "plug-in" your desired boat sail parameters. You can dial the wind from 0 to 25 knots if you desire. For my purposes 1 to 12 knots would encompass the most extreme conditions.....most times the boat would be sailing in 2 to 8 knots of wind on a relatively flat surface of water.
This hull design was made using the Design Rules of this boat class. Here they are in complete form http://theamya.org/boats/us1m/
I probably didn't add much to your knowledge but I tried.

Best

 

This boats design was arrived by formula .Many designers use curves as simple as C2 equals A2 +B2 so accuracy is definite .An ellipse is just a circle that is modified . This boat uses conical development Most boats with radius chines will use this . Displacement is what you make it .Freeship is a little inflexible at times. Design draft on the 39.37ft model is 2.133 feet (2200profile)displacement 6.867 ton. So divide by 1728 Anwser 3.9739kg for the 1metre model

 

Your FreeShip modelling is very impressive. Beautiful work!

I am interested in the shape of the keel line (which seems close to a
parabola) and the cross-sections (which are close to elliptical).

My program Michlet can be used to find a mathematical approximation
to hulls like these. For example, it can find the closest Series 8 or
Series 9 parameters, ( for those who know how those series work.)

Is it possible to get the offsets of this hull in Michlet format, or
the input file that can be used in DelftShip? (I have never used
FreeShip.)

If so, I will run Godzilla to find the closest approximation and post
the results here.

Leo.

 

Than you Rumncoke, got it, and all, thank goodness for computers!

 

This is a design of my own, it maybe an improvement on the design we have been looking at. Major improvements or differences. Entrance angle of 11 degrees versus 18 cp of .58 better for close to displacement speed similar beam and displacement 5.3lbs versus 8.8lbs .Location centre of flotation 43% versus 50% What does everyone think?

 

hydrostatics

The hydrostatics for the above hull. Its sized at 9.975m for convenience as real world its a 1metre boat. View attachment stats.txt

 

@nzboy,
Amazing work. I like the fact that you actually put a hard keel line on it. It looks fast and very relevant compared to other current designs in this class. One consideration is the fact that the sail area and profiles used in these models tends to overwhelm the boat surface area downwind and plant the front section of the boat underwater to a stalled condition. Most of these boats still do this. My original design was very full up front and when other boats were planting their bows under, my boat would still be cutting water at the sheer line of the bow tip. I like your design work-up very much nzboy. If center of floatation is at 43% then we could move the Sail Rigging and Keel placement back in the boat as well which would help fight against the Submarining effect downwind. Very interesting. Any chance you could figure "Center of Lateral Effort" on the boat? I will send you a PM. Nevermind I figured CLE at 4.921 on your drawing. My interest is Piqued hehe.