Resistance Prediction Methods Help!!

I was just wondering if anyone could give me and idea of (in nutshell) the limitations and appropriate vessel types for the following resistance prediction algorithms, as i do not have access to the relevant references to find out these things
Gerritsma et al 1981

Gerritsma et al 1996

Savitsky AND Brown (already have a general idea about the standalone savitsky method..i think!!)

Many Thanks

 

Molland A. 'Ship Resistance and Propulsion: Practical Estimation of Ship Propulsive Power'

 

Quite expensive!

Is there anything worthwhile inside or is it just the usual boilerplate text found in any other book dealing with hull resistance?

Judging from the TOC on Amazon, only the last chapters seem they could contain some newer findings.

 

George, check the Appendix B of this document (Gerritsma = Delft Series): http://www.fdsfiles.com/releases/manuals/HSManual.pdf

 

Thanks for the book reference, but unfortunately i dont have access to a library or that kind of cash at the moment! Are there any internet links with reliable info on just the basics of these methods, or someone that can breifly state the limitations (Fr, Cb, LBT, etc) and hull forms appropriate.

Thanks

 

Thats excellent! Thanks so much, and just on the off chance do you know if savitsky and 'savitsky and brown' method are very similar?

Cheers

 

Here is the 1992 paper by Gerritsma et al.: http://www.hiswasymposium.com/asset...17th - 2002/Gerritsma@hiswasymposium-2002.pdf

 

Savitsky & Brown work is an extension of the original Savitsky's work (which was for prismatic hulls in calm water) to prismatic and warped hulls in seaway, together with a description of a Mercier-Savitsky method for evaluation of resistance in the pre-planing range. The paper can be found here: http://www.boatdesign.net/Forums/at...638152-savitskys-papers-savitsky_brown_76.pdf
Cheers

 

Thats fantastic thanks a bunch!

 

I did my thesis on methods of small craft resistance and their verification. Just to note - from what I recall (going from memory here, so give me some rope) of that Brown paper - one should be careful with those terms dealing with flaps, and right somewhere near the end - terms for vertical accelerations.

Don't remember what exactly was weird with the flap equations, but the acceleration terms were giving some weird values. Too big, if memory serves.

Has anyone else done any comparisons of the above, that they could put here to put me wrong?

 

Knowledge is not expensive... Book is quite good; it presents coefficients for many methods so is usable.

 

I'm sorry, can't help you there. Perhaps someone else will jump in and give an answer...

 

hello all!
The problems with the accelerations method were that it was derived from an statistical study, by Fridsma at the Davidson, long long LONG time ago. Fridsma had to do the study in two parts, I think it was because his first assumption regarding the test were wrong. Doesn’t really matter for this topic I believe.
Savitsky and Brown derived a set of easy to use formula’s for the prediction of acceleration, based upon the test results of Fridsma. So the limitations were that of the scope of the test characteristics of Fridsma. In the study of Savitsky and Brown, they claim a error margin of 0,2g, that is if the design was to lay within the set boundaries.
I hope this is a suitable answer for youre question regarding Accelerations, don’t know the weirdness of the flap predication.
l

 

Hi every body

Also it's noticeable that could find last method during ITTC2008 and 2011...in Rio..
BR