Rectangular boom

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BBSCFaithfull
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Joined: Mon Jun 19, 2006 5:15 pm
Location: Fordcombe, Tunbridge Wells, Kent

Rectangular boom

Post by BBSCFaithfull » Wed Jun 04, 2014 10:32 am

Hello,

What are the main benefits of Rectangular booms? Is it reduced bend along the length?

Are there any downsides opposed to a traditional round unit?

Best,
Alex
Upright not upside down!

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oliver1000
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Boat Number: K1282
Location: Perth and Helensburgh, UK

Re: Rectangular boom

Post by oliver1000 » Thu Jun 05, 2014 9:07 am

I'm sure someone will correct me on this but, I guess the flex would be decreased in the vertical plane if you made the boom taller, however, if you then made it thinner the flex would be increased in the horizontal plane, just like taking a rule and trying to flex it in both the vertical and horizontal planes (one way you'll get nothing and the other you'll get a lot).

A cylinder does not have the same issue as no matter how you orient it it will have the same flex. Due also to the lack of corners it is an inherently stronger shape, and the stress caused when sailing is distributed throughout the shape.

That said there may be more reasons, why you would want a rectangular boom, or why you wouldn't - possibly the way it affects the sail shape but I'm afraid I have never used one so cant really comment
Ollie Williams
K1282

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rand
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Re: Rectangular boom

Post by rand » Fri Jun 06, 2014 2:08 pm

Structurally the shapes are quite different. A square has strength in two dimensions, a circle and uniform strength in all dimensions.

So a rectangular boom will give you benefits, if the forces are consistently in line with the strong dimensions, but will fail sooner if stressed in an alternate dimension. Given that in 14's we rarely can guarantee that we will use our equipment in the manner designed (falling onto the boom in a capsize for instance), a round shape in generally safer.

I'm not a structural or materials engineer so I could tell you the weight savings between optimal shapes, but with carbon, I suspect that it wouldn't be much on a 14.
Rand Arnold
International 14 USA 1143
"A Bumblebee Called Kate"
(former US President, former US Measurer)

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Shu
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Re: Rectangular boom

Post by Shu » Fri Jun 06, 2014 8:47 pm

Good observations Rand. However, there seem to be some in the fleet who are so confident in their boat handling abilities that they don't worry (much) about loading their equipment in an unauthorized manner. I'm thinking of one boat on the US west coast that has adopted large aluminum handles on its trapezes that serve as both handle/puck and ring. This is very nice for clipping in on the fly, but if employed on my boat would likely result in missing teeth during one my less-than-stellar manouevers. So for these ultra-confident teams, consideration for what happens when one falls on the boom is inconsequential when compared to what is the most efficient shape.
Another thing that a rectangular boom provides is additional sail area. Hence the rule limiting its size. Granted it's not very efficient sail area, but like a plank held at an angle to the wind, it will provide some thrust in the desired direction.
Steve Shumaker
USA 1183

joe.bersch
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Re: Rectangular boom

Post by joe.bersch » Sat Jun 07, 2014 5:27 am

Steve:

Like Rand's your comments are very interesting. Unlike the one boat you mention, I see others have begun to put foam padding in the bottoms of their boats. I assume this is to make it safer when they fall down due to misuse of the equipment? Do you likewise think they might start to pad their booms? Me, I am mostly thinking about padding my crew's elbows!

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rand
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Re: Rectangular boom

Post by rand » Sat Jun 07, 2014 1:57 pm

Might be less weight (although less mobility) if we just pad ourselves extensively :)
Rand Arnold
International 14 USA 1143
"A Bumblebee Called Kate"
(former US President, former US Measurer)

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Shu
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Re: Rectangular boom

Post by Shu » Mon Jun 09, 2014 5:08 pm

Joe,
I not only pad my deck, I pad my knees. My backside already has plenty of padding. Having taken an elbow to the face myself during a douse at the Toronto Worlds, I'm a little more inclined to drag the transom during a light air douse, but the elbow padding sounds like a possible solution, or maybe I should just wear a motorcycle helmet :D
Steve Shumaker
USA 1183

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