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post #1 of 14 Old 05-24-2010 Thread Starter
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mast vs boom

I am looking for information as to why the mast is longer than the boom and reasons as to why it couldn't be shorter mast longer boom? any bites?
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post #2 of 14 Old 05-24-2010
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In the past there have certainly been boats with long booms vs high masts.

However, there is more air up *there* and rigs can now be made taller. Hence the modern design.

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post #3 of 14 Old 05-24-2010
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OK I'll bite. My boat is 44 ft so probably 28 foot behind the mast. It has a 55 foot mast. So to do it your way would mean that to have the same sail area, my mast would stick out the back of the boat by 27 feet. It would mean my slip in the marina would have to be 71 feet long. Ouch. :-)

And that's just one frivolous reason


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post #4 of 14 Old 05-24-2010
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Hmmmmm

Hmmmmm......
Lot's could be said.
Simple answer: Its a complex question. Lots of science, consideration, trial/error, etc. has resulted in modern sail, boat, rig design. Turns out, "Short boom/longer mast" is the best way to do it.

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post #5 of 14 Old 05-24-2010
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On a broad reach or run, a long boom could be so far out over the water that it risks submerging on a roll or passing swell.
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post #6 of 14 Old 05-24-2010
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tall mast/deep keel

For beating at least, you get the more lift from a thinner blade than the short stubby one. For that reason, many high performance boats have deep blade keels and tall masts, as the lift equations work in both fluids (air and water).

That said, there have been designs with exceptionally long booms, and gaffs that are very successful (and beautiful ). I believe many of these designs had their origins in places with bridge clearance issues, etc. Even today many modern designs stop at 65' for bridge clearance.

And of course, a really deep keel means you are restricted by draft.

So most boats are a compromise. For a good read on all this, try a book by Marchaj, I think called Sailing Theory and Practice.
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post #7 of 14 Old 05-24-2010
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Consider the advantages of a gaff rigged schooner: Lower masts means less rigging needed to keep a long pole up. Less heeling moment, so less draft needed. And they look really salty.

But, on the other hand wind velocity is lower near the surface, thus, the popularity of Marconi sloop rigs.
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post #8 of 14 Old 05-24-2010
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Translational physics would dictate that any force applied most directly to a true surface would result in a large shift of energy thusly translated to said surface. The surface thus acted upon, would incur a translation of energy proportional to the energy subjected to it...in keeping with the laws Conservation of Energy, resultant energy, of course, being of linear association. Say we have true surface AB...the surface from which energy shall be donated, and parallel surface CD, the surface whereupon said energy shall be translated to........



Actually I have NO idea, beyond that it just makes intuitive sense. But I just reminded myself how I always used to get an "A" on high school physics exams without having a CLUE what I was talking about! I would just write the answer in the above terms, and bore the examiner SO MUCH that he wouldn't even bother finishing reading the answer, and give me an automatic 'A'. Throw in a few Newton's Law's here and there, a few "thuses" and "shifts"...and you're good to go. Throw in a 'whereupon' or a 'therein', and then we're talking bonus points.

I've found this technique also applies well to 100 through 400 level college courses, as well....but falls most amazingly short in 600 level and above graduate courses!!! At which time, one must actually study.

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post #9 of 14 Old 05-24-2010
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Aside from the reasons above: requiring a longer slip, creating a less efficient sail form, not taking advantage of the stronger winds aloft, risk of breaking the boom in heavy seas, etc.

A longer boom also presents a greater danger to the crew as a general rule. If you've ever sailed a catboat and gotten hit by the boom, you'll know what I mean.

Also, having a longer boom shifts the center of effort aft, which gives the boat more weather helm. It would be very difficult to design a boat with a short mast and very long boom that didn't have massive weather helm issues.

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post #10 of 14 Old 05-24-2010
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Remember the sail acts a a vertical wing. A long thin wing provides more lift per square inch than a short fat wing. Another reason would point at windspeed as being lower at the water surface than at altitude, although 20 to 30 feet probably doesn't make that much difference. I would think the biggest issue would be the amount of boom to handle during a tack and jibe, think of the mass moving on a 50ft boom.
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