Online Resistance calculator

Hi all. I'm making my first attempt to what could be (at some remote future) a free VPP online, without using any sophisticated software tools.
Actually, I'm using GoogleDocs, wich has a lot of limitations, but allows realtime workgroups.
So, if anyone is interested in collaborating, please post here! I can do (and share) the googledocs part, but need someone with a better knowledge background.

This page should give you Heeled and Residuary Resistance, in a few minutes. There is place for 10 different boats and/or alternatives. Please try it!

http://klz-resistance.blogspot.com/

 

Looks good. Guess you have made it with formulae from Principles of Yacht Design?
I think it would be nice if you made a version in English too, for people who don't speak Spanish.
Cheers!

 

Thanks Daikiri! I've taken formulas from PYD, it's based on Gerritsma's Delft regretion series. I'll make it on english soon, anyway coefficients and measurements use the english acronyms so they are easy to understand.
The last improvement is Frictional Resistance (hull, keel and rudder), and Total Resistance (Rr + Rheeled + Rfric). I also added a Coeff. Table, to show the inputs. Next step will be to publish detailed data of Resistance, so you can copy and paste to your own spreadsheet.
Any verified data to check funcionality will be welcome, by the way...

 

Output data tables added ('Outcomes' page).
To paste data in excell is strightforward: select (paint) table data, copy and paste it on a Notebook text editor file (or any other ascii text editor), now select (paint) data from the Notebook file and paste it to a SINGLE cell in excell.

This concludes the Resistance part. I'll try something like this with the G. Hazen aerodynamic model, later...

 

Another set of resistance equations are in the ORC VPP documentation which can be downloaded for free.

 

Posted by DCockey:

Thanks David, I allready have the paper (ORC 2009), but think I'm not ready for it yet (unless you and/or someone else give me a hand to understand it ).

Hazen's model does not seem difficult (at first glance), but it has few angles for AWA, do you know some kind of "spline" formulae to interpolate between them?
Tks.

 

The 2011 version of the ORC VPP documentation can be downloaded: www.orc.org/rules/ORC VPP Documentation 2011.pdf

It has the various equations and coefficients for resistance, very similar to those in Principles of Yacht Design, though they are scattered in several different sections. My recollection is the tables with the coefficients are near the end.

 

Thanks for the paper David. As said, 79 pages plenty of formulae are still away from my time and knowledge, anyway I'll give it a glance.
By now, I finished the old 1980 Hazen aero model as seen in PYD, but I'm stuck with the heeling issue, may be you, or someone else, can help me:
How should the Effective AW Velocity and Effective AW Angle be used to correct the unheeled results for Driving and Side forces?. As the original model has just five preset AWA, what should be done with the modified angles?.
And how should the Heeling Arm Height be calculated? An average of all CE, related to their respective areas?
Regards

 

It has a lot fewer pages than PYD. Formulas are very similar. If you understand the formulas in PYD you can understand those in the ORC VPP documentation.

Upright residual resistance: p55, equation 70
Coefficients for equation 70: p79, Appendix B

Heeled residual resistance multiplier: p 61, equations 73 - 78

 

Understand, yes. Use, no.


How do you compute the various LSM for heel resistance, or transom drag ?

It is page 20 of VPP doc.

But where is x=0 , fore or aft ?

And what is x at the other side ? x = lwl (which unit, meter feet) or x=1

And what is s (what unit)

And last, how do you solve the circular reference for LSM0. You compute LSM0 with section area depth attenuated by LSM0.

Thanks for help.

 

It seams this formula is only for canoe body.
It should include all sort of hull.
Lister

 

"Canoe body" in this context means the hull without keel and rudder. It's a standard term in the sailboat design community.

 

This is the G.Hazen 1980 aero-model, as in PYD

http://klz-sailforces.blogspot.com/

To input data, use the DataInn Form from the left menu. It must show results in a few minutes. You'll see detailed output of Sailcoeff, Sailareas, Centers of Effort, Sideforce and Driveforce, for 0 to 15 m/s AWS, all for the unheeled condition.

Now I need help: Is the original Hazen paper public? I can't find it. I'm stuck with the heeled condition, don't know how to reduce side force by cos(heelangle). In fact, don't understand why can't you just multiply Sideforce*cos(heeling). PYD shows some formulas to recalculate AWS and AWA, but a new AWA should use different constants, isn't it?
Any help will be appreciated.
(David, if I succeed with this, then I'll face the ORC paper. These are my first steps )

 

Perhaps this http://www.hiper08.unina.it/cd hiper 08/HTML/Papers/2 - Fossati.pdf may interest you ?

 

The sail forces go with cosineSquared of the heel angle. Think about the first cosine as the diminishing projected sail area with heel. The second cosine can be thought as an effect on the AWA - at AWA(90), sail forces go to zero.

Anyhow, if you multiply the upright sail forces with cosineSquared of heel, you get a good representation of the forces at an angle of heel.