Velocity Vectors

[Brian Duff]

TomP,
Perhaps I misunderstand, but you are meaning that every bushing ( every pin, every everything) is subject to loads from different directions depending on how the boat is moving ?

It would be really great for you to share some of the formulas for figuring this stuff out. I understand moment arm, the basic physics, but I guess thinking about the velocity vectors of a boat in a sea state is much more complex. I have just been doing all this by rule of thumb , and looking at what has worked on previous boats. (an skenes of course)

That said- when building a new extended mount for something like a tricolor light to be above a masthead , I would really love to figure out the loads that the light base might see when the boat slams in to a wave. But wow ! There must be so many varialbles there ?

: )

[TomP]

Yes,

It is called classical mechanics or Newtonian Mechanics-which is the original theoretical treatise of motion (kinematics) and forces (dynamics). With respect to deformation of objects which is known as continuum mechanics.
Issue of the formula are translational motion, relative velocity and rectilinear motion.
Unfortunately, this forum does not lend itself well to the publishing of the actual formulae.

Instead, I forward you to:
Applied Mechanics Divsion of ASME
http://divisions.asme.org/amd/index.html

"Materials Selection in Design" by M.F. Ashby
"Mechanical Properties of Matter" by A.H. Cottrell
"Engineering Mechanics Vols 1 & 2" by Meriam and Kraige

[Brian Duff]

thanks Tom,
you so often see statments in yacht design books bout how the loads are so poorly understood, and I can see why after looking at those sorts of formulae !

Wild.

[TomP]

Originally Posted by Brian Duff

thanks Tom,
you so often see statments in yacht design books bout how the loads are so poorly understood, and I can see why after looking at those sorts of formulae !

Wild.

I do not know what books you have read, but I have never seen that statement in any of the texts I have.

It is not too terribly diffcult to discern. Simple application of variables and formulae will yield the result.

[Brian Duff]

Don't get me wrong, I understand the process, but as its been said



Those are from Rigger Apprentice and Skene's. I don't want to be obsessive, so I'll stop.

I suppose the testing process will never end and till then, we'll just keep making it 'too strong'.

: )

[TomP]

Let me finish your ill fated attempt at a quote:

"By observing and keeping track of enough successes and failures, designers have developed an empirical data base, and translated that into workable formulas."

Quotes of convienence I suspect.

[Brian Duff]

Tom,
Seems you might be getting riled, chill man

I appreciate the links and refernces you shot out earlier in this post, and value your opinions. This is not a competition, but a friendly learning site. I guess cause we have both been around here a while, I josh a bit with you. All in good fun and don't take offense.

and I didn't even flip the page in ' riggers apprentice', midnight games.. oops !

What I was getting at was that we seem to use a lot of 'safety' factors to get things strong enought to deal with the loads we don't know fully, like the force on a chainplate when the boat is going 6.7kts and hits a reef, or whatever. I guess the density of the reef, stiffness of the hull and so may other factors go in which is why it all just gets rounded up.

Good Fun man !