Mast Deflection Speeds (esp dinghies)

[BWD]

Amen. But that's just the macro scale.
It works on the shorter time frame/smaller impacts too, as I wrote above, with the boat/board running over chop/waves/ripples, 50 or 100 or 200 times a minute.

With good windsurf rig it really is like having a crew who can trim and tune your rig several times a second. I think anyone interested in speed who doesn't know this from experience should at least look at slow motion video of windsurfers in choppy water.

The spars are a bow the wind and sea are constantly bending to shoot the board and the sailor forward.
The board is an arrow that carries its own bow.
Unstayed carbon (on the windsurfer scale at least) allows the "bow" to unbend in a fraction of a second and shoot the board forward before the next gust or wave bends it again.
I eagerly await the genius who can succesfully scale this up to a 40 footer. Wylie is part of the way there at least... but there are power to weight problems and materials limits, so it may be a long wile.

[water addict]

Originally Posted by frosh

Water addict, If you read and absorb the material in my postings and also the stuff about the Finn dinghy masts, and the Fiberspar web site, it is all there for all the interpretation that is necessary to understand the concept. I don't get what the difficulty is with it all? Any way in summary, it goes something like this: A really efficient rig on a high performance dinghy or sailboard needs to be self adjusting and very rapidly so. This means than when the sail is temporarily in a higher than mean wind strength which potentially could produce heeling force that would overcome the human ballasted righting moment, heeling does not occur. You understand that there are gross gusts that can be detected easily by an experienced sailor by seeing cats paws on the water or feeling the higher wind velocity on your face, but also there is an unseen but measurable roughness to what might feel and look like a fairly constant wind. This could be graphed as a low amplitude reasonably high frequency sine wave, graphing actual wind velocity against time. When already fully powered up what then happens when we are on the upper section of the sine wave of wind strength? What needs to happen is that the upper sail twists off very momentarily flattening the upper sail section, and lowering both drag and drive in the upper third, which means that no noticable additional heeling occurs, and the boat accelerates. Possibly a second or two later the sine wave has moved to a point less than the mean wind strength. The mast starts to straighten out in the upper section rapidly, (and this is the entire crux of high speed reflex response), and the sail powers up in the upper third again and the sailor feels almost no change in the heeling force but boat speed barely drops as the rig is suddenly generating more power due to less twist and slightly more camber in the upper third of the sail. This needs to happen very quickly and in harmony with a fairly constant hiking force, i.e righting moment exerted by the sailor, who does not need to rapidly move his body further or less further to windward. I hope that this descriptive but non-mathematical explanation sort of clears up the mystery for you now.

I understand these concepts, and did before this thread. So perhaps I am up to speed on them? Is that all you have to offer? Sorry for the somewhat pointed diction, but since you seem to have no trouble trouncing on me, I'll give a little pissyness right back at ya.

The rate of deflection and how it relates to the boat speed is way more complicated than that dude. And it will be variable depending on a whole host of factors on a particular boat in given conditions. My original comment that weight aloft, mast dimensions, and static stiffness will have orders of magnitude more impact in the average boat speed still stands. I think I'm at least as up to speed on this as you are, buckwheat, at least from the subjective, very basic conceptual stuff you've offered up so far.

I also understand that none of these lesser effects are readily quantifiable as you say. They are often interpreted by the sailor and designer without strict controls, as that is the only reasonable way to address the issues without monstrous budgets. The pseudo engineering of deflection v. load on the fiberspar web site to a trained engineer is a big "so what". Yes 2+2=4. Been done before.

[frosh]

Hi Water Addict, lets call a truce on this issue. I concede you probably know your stuff pretty well, it's just that the message you convey is that so why is reflex response very important at all? You probably know a lot more about static and dynamic loads on rigs on larger yachts than me, and I have no wish to prove otherwise. After all, isn't boating your profession? For me it's a passion only, and I am really only into sailboards and high performance small dinghies and multis. I really have no wish to trounce anyone; OK?
Regards, Sam