| Need help explaining something #106690 05/11/07 02:15 AM 05/11/07 02:15 AM |
Joined: Oct 2006 Posts: 902 Norman,OK gree2056 OP
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Posts: 902 Norman,OK | An older friend of mine has started a debate with me about the physics of masts.
He thinks that if you had a mast that was perfectly stiff the boat would be faster than a boat with a semi flexible mast.
I started to debate back but I had nothing, all I could tihnk of was the ability to spill aire in big wind and not over power the boat.
Is there any other advantage to a flexible mast over a very stiff one?
Once you go cat you never go back!
Nacra 5.2 (Elsies)#1499, running an inter17 spin!
| | | Re: Need help explaining something
[Re: mbounds]
#106694 05/11/07 06:29 AM 05/11/07 06:29 AM |
Joined: Jun 2001 Posts: 1,449 phill
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Posts: 1,449 | Jake, There are times when I think what a bugger it is that I was born in such a warm Climate.
That looks just so cool!
I would really enjoy that.
Regards, Phill
I know that the voices in my head aint real, but they have some pretty good ideas. There is no such thing as a quick fix and I've never had free lunch!
| | | Re: Need help explaining something
[Re: Rolf_Nilsen]
#106697 05/11/07 07:05 AM 05/11/07 07:05 AM |
Joined: Jun 2001 Posts: 1,449 phill
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Posts: 1,449 | Rolf, Some of the pics you have sent me of your homeland appear to be really spectacular. Having never experienced that type of cold I can only imagine in a fuzzy kind of way and admire the beauty.
Just like imagining the type of speed that I could get out of an Ice boat in a good breeze.
You know what they say- "No sense, no feeling"
'Go flying in an Ice boat."
One of the 10 things That I must do.
Regards, Phill
Last edited by phill; 05/11/07 07:06 AM.
I know that the voices in my head aint real, but they have some pretty good ideas. There is no such thing as a quick fix and I've never had free lunch!
| | | Re: Need help explaining something
[Re: gree2056]
#106698 05/11/07 08:33 AM 05/11/07 08:33 AM |
Joined: Oct 2002 Posts: 1,226 Atlanta bvining
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Posts: 1,226 Atlanta | The biggest thing most modern catamaran masts do is allow you to flatten the sail to control the amount of power you have as the breeze increases. Most sails are built with some luff curve, and most mast a built straight. So you add diamond wires and add some prebend into the mast, but its still straighter than the sail (if the sailmaker has done his job) This causes the sail to be full and the sail in this shape produces lots of lift (power)
So, without any downhaul, you have a very full sail shape, which is good up until the boat begins to heel to much in puffs. Adding more downhaul bends the mast back and gets the mast closer to the prebuilt luff curve of the sail, and flattens the sail. This allows you to go faster in higher winds. So if you are sailing in higher winds and the boat feels sticky or overpowered in gusts, add more downhaul. Modern wing masts like the Acat masts are really good at this. You can actually play the downhaul instead of the main on the HT, which has a modern wing mast. This is really fast by the way.
A really good example is an airplane wing. When you are taking off, and landing you need full power with lower wind, so the pilot has uses lots of flaps (think full sail shape) When the plane is crusing along the flaps are retracted and the wing is less full, (think flat sail shape)
Fore and aft bends helps with flattening the sail and works with downhaul. You also want some sideways bend, which needs to bend differiently than the fore and aft. Most masts (modern wing masts) are more stiff fore and aft than sideways. This sideways bend helps with the mast twisting off in a gust. Diamond wires keep the mast in column depending on your weight, so the top can bend off, but the middle stays straighter side to side.
The Acat masts a built with two bend numbers in mind. The first is the sail makers luff curve and sail charactoristics and the second is the weight of the sailor - which influences the side bend of the mast.
The net is that a mast needs to bend, but in a very specific, very calculated way and bend differiently fore and aft vs side to side. Rotating wing mast on catamarans are actually some of the most advanced masts and sail combinations on the water, not counting a CClass type rigid wing sail. Cat rigs are way more efficient than monohull masts/sails and its one of the reasons modern cats are so fast. | | | Re: Need help explaining something
[Re: bvining]
#106700 05/11/07 02:20 PM 05/11/07 02:20 PM |
Joined: Oct 2006 Posts: 902 Norman,OK gree2056 OP
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Posts: 902 Norman,OK | Thanks guys this was the kind of info I was looking for. I knew it needed to be flexible but I couldn't put it into words\
Once you go cat you never go back!
Nacra 5.2 (Elsies)#1499, running an inter17 spin!
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