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| Sailing Physics http://www.hobie.com/au/en/forums/viewtopic.php?f=14&t=56170 |
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| Author: | BboySlug [ Mon Oct 05, 2015 7:10 am ] |
| Post subject: | Sailing Physics |
I have a couple questions on the physics behind sailing. I really love the sport because there is so much physics that goes into it, and now being a boat owner I'm getting into the tiny details. 1) Mast Rake: I understand most of the physics, but I don't really see why its common knowledge to rake the mast back more in higher wind and less in lighter wind. I do understand that it would make the boat slightly more aerodynamic going forwards if the mast is raked back, but I don't think that that concept alone makes it noticable so much that people talk about it so much. Thus, why do we rake the mast back more in higher wind? 2) I used to sail FJs in collegiate sailing. When going completely downwind, we would go wing-on-wing in order to get more sail area. Wind comes off the main and gets funneled into the jib when doing this. Now, I'm talking for a hobie 16's scenario that you do this in incredibly light wind (like I when I was soloing last weekend). There's no way I would risk a pitch pole being an idiot in over 5mph wind going wing-on-wing in a hobie 16. Yet, I told my friend who owns a Nacra 5.7 that I went wing-on-wing in light winds and he said that that's not optimal for a catamaran because the jib somehow puts wind into the main when you're on a broad reach. I started thinking more and more, and couldn't wrap my brain around it. So, in very light winds (so no risk of pitch pole), why not go wing-on-wing? Thanks in advance, I wanted to ask more experienced Hobie sailors before I decided my friend was an idiot. He and I have about the same experience racing. -Evan |
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| Author: | John Lunn [ Mon Oct 05, 2015 11:20 am ] |
| Post subject: | Re: Sailing Physics |
Evan those are good questions, and don't be inhibited to ask - that's how all of us learn. For Christmas, ask someone to buy you HPS II (Higher Performance Sailing II) by Dr Frank Bethwaite. Warning - it is not cheap, nor is it a quick read, at over 1,000 pages. OR see if your local library has it. It is THE book which will teach you about apparent wind, and why skiffs and cats sail the way they do. Such as 'tacking downwind is faster than wing-on-wing'. Mast rake has to do with moving the C of E to the stern with higher apparent wind forces for better pointing ability and smoother downwind runs. If there is a cat fleet or a skiff fleet near you, (29'ers and 49'ers), go buy them beers, and they will share more information than any of us could write up on this Forum. Remember, mono slugs, skiffs and cats each have their own design parameters, which means that each of them will sail differently. When you've mastered all that, move up to a spinnaker, where there is a whole different level of learning that takes place. |
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| Author: | ASDASC [ Mon Oct 05, 2015 11:52 am ] |
| Post subject: | Re: Sailing Physics |
In the simplist terms: 1. When you rake the mast back, you move the center of effort back, reducing the chance to pitchpole in high wind. 2. In a cat, you go faster gybing downwind than you would just going wing-on-wing. |
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