Dynamic Stability of planing hulls

Hi all,

Blount and Codega in their paper "Dynamic Stability of Planing Boats" mention various types of dynamic instabilities at different speeds. I want to know if there are any equations which can predict whether a boat will be subject to dynamic instabilities when underway.

As for porpoising if found the plot by Savitsky and and for transverse stability I found a paper by Lewandowski.

With regards to bow diving, you can analyse whether the craft will dive by looking at the trim-speed curve.

I need more formulas even for porpoising and transverse stability to ensure that when the craft is underway it will be stable.

Any papers or books which can help?

thanks

 

do a google search on "dynamic instability in planing craft" and you will get a lot (thousands) of hits. Blounts and Codegas study is probably the best one though. They were studying the problems with the USCG 30 foot surf rescue boat that had a bad habit of nose diving.

 

Don't forget 'chine walking': An 'under way' transverse stability matter that can range from a nuisance to deadly.

 

There are many different types of dynamic stability However these may assist you:

"Method for Regulatory % Design Assessment of Planing Craft Dynamic Stability", P.R. Werenskoid, Fast '93.

"The Hydrodynamic Lift Effect on the Stability and on the Banking Angle of the Fast Crafts", Prof. I.M. Simeone, Fast '91.

"Dynamic Stability Analysis for US Navy Small Craft", Navseadet Norfolk Report No 6660-99, 1982.

 

Needless to say, dynamic stability factors in a planing monohull will be quite different to, e.g, a catamaran. Might be easier to make an RC model and test it on the water under varying conditions, to satisfy yourself there are no quirks, rather than using a purely theoretical approach. The dynamic factors are presumably amplified in a scale model ( or maybe I presume too much). I am assuming that you are designing something, and worried it might not behave as you hope.

 

Do you know where I can get a copy of that particular Navseadet Norfolk report?

 

Use this link : http://www.google.es/url?sa=t&rct=j...93.pdf&usg=AFQjCNGiAqQmj07WXlzxTNt8HkLTIeoVIQ
But this is a very old study. Attached file are somewhat more modern and, sure, there are still more current studies.

 

I'm trying to find the Navseadet report from 1982 specifically. It seems the document in the link is something different, or am I mistaken? Thanks for the help.

 

http://www.dtic.mil/dtic/tr/fulltext/u2/b240994.pdf

 

Apparently there are many studies on dynamic stability (not only porpoising) so, if you search a little on Google, surely you find what you need. Now, try to get something that is less than 15 years, among other things because the calculation with computers has left other methods as obsolete.

 

Yes, the reference tells you, FAST '93 conference proceedings.

Noted here:
Fast '93 : Second International Conference on Fast Sea Transportation, Yokohama, Japan, December 13-16 1993 (Book, 1993) [WorldCat.org] http://www.worldcat.org/title/fast-93-second-international-conference-on-fast-sea-transportation-yokohama-japan-december-13-16-1993/oclc/33351220

It is on page 883.
(The % should read &)

 

So the paper by Blount published in 1992, is more up to date than the 1993 publication by Werenskiold..???!!!

 

I think the blunder blinds you (I know you love me) . I meant one of the files, not the two. But you are right, I said "attached file are"; "are" has been a mistake. It was really easy to understand, since the dates appear on each file, what I meant. Do you need me to explain to you something else? I will gladly do so.
And I totally agree, the file indicated by you, and one of the ones indicated by me, are totally outside of what we could call "current technology". It seems to me that both you and I are becoming obsolete. What are we going to do? Age does not forgive.

 

I have a copy of the FAST '93 proceedings. It does not have what I am looking for. I believe you were referring to another article, different from the one I am looking for.

Again, I am specifically looking for the following document: "Dynamic Stability Analysis for US Navy Small Craft", Navseadet Norfolk report No 6660-99, 1982.
Thanks for all the help, by the way.

 

http://www.dtic.mil/dtic/tr/fulltext/u2/a047493.pdf