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Old 20-11-2011, 11:08   #1
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New Revolutionary Rig ?

hei all,

i'm a big fan of Chris White's catamarans, but do not have so much sailing experience yet to comment on this new rig type for the A47

have a look here

MastFoil(tm) patent pending sailing rig by Chris White Designs High Performance Seaworthy Sailing Yachts

looks to me as a fantastic rig for cruising

Olli
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Old 20-11-2011, 11:49   #2
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Re: New revolutionary rig??

It will be interesting to follow this. One problem in the past with fixed wings is that even fully stalled, they still provide lift and the boat sails. It will also be interesting to find out how these perform at anchor with strong shifting winds - will they react and stall fast enough? Will they be noisy?

Mark
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Old 20-11-2011, 13:17   #3
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Re: New revolutionary rig??

I saw sails like that in aboat a week ago in La Gomera, two self tacking jibs in a "schooner" that is.
Foils with different set ups around the masts has been in various occasions for ages but can't name any just now..
Interesting thou
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Old 20-11-2011, 13:29   #4
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Re: New revolutionary rig??

I'm sure this has been though of by the designers, but how do you reef a foil?
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Old 20-11-2011, 13:37   #5
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Re: New revolutionary rig??

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Originally Posted by avb3 View Post
I'm sure this has been though of by the designers, but how do you reef a foil?

if i understood it right there is no reefing in a usual sense, the foil feathers into the wind and that's it

it will have the same (or as here stated) less windage then a mast, so no need of reefing
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Old 20-11-2011, 13:40   #6
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Re: New revolutionary rig??

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Originally Posted by colemj View Post
It will be interesting to follow this. One problem in the past with fixed wings is that even fully stalled, they still provide lift and the boat sails. It will also be interesting to find out how these perform at anchor with strong shifting winds - will they react and stall fast enough? Will they be noisy?

Mark
hei Mark,
do you think if the small foils feather into wind they still will produce some lift?

for the shifting winds, yes thats definitely something to look at!
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Old 20-11-2011, 13:44   #7
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Re: New revolutionary rig??

no lift is produced in a symmetrical foil at zero degrees angle of attack (dead into the wind)....
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Old 20-11-2011, 14:25   #8
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Re: New revolutionary rig??

I'm partial to a A mast, removes compression loading away from the weak, center of the hull, and gives furling to the mainsail, if you can still call it a mainsail.

SMG 50plus - innovative catamaran with A-frame-rig



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Old 20-11-2011, 15:08   #9
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Re: New Revolutionary Rig ?

A foil still has drag, even when it is not producing lift. Is the drag less, the same or greater than a bare single mast?

Just going by looks alone, it appears to have more drag than a bare mast. Could this be a problem in high winds?
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Old 20-11-2011, 17:15   #10
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Re: New Revolutionary Rig ?

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Originally Posted by David M View Post
A foil still has drag, even when it is not producing lift. Is the drag less, the same or greater than a bare single mast?

Just going by looks alone, it appears to have more drag than a bare mast. Could this be a problem in high winds?
The blurb claims less drag:

"Less aerodynamic windage (drag) than a conventional mast and rigging equals less strain on the anchor which reduces the risk of dragging. The MastFoil rig will reduce the wind drag at anchor by approximately a 20%."

Although later on it says this:

"What happens with the MastFoil rig offshore in a storm?
Nothing, if that is what you want! The foil will feather into the wind on any point of sail. When feathered, the drag of the mast and rigging is reduced by about 90% over a conventional mast. In severe weather having the least windage possible will make handling the boat safer and easier."

I'm not sure why at anchor the mast has 20% less drag and offshore, when feathered, it has 90% less drag?

The claims concerning being able to pull the boat off a dock or provide backward thrust while running are interesting as well. I look forward to seeing how this rig pans out. Unfortunately, it will no doubt be expensive.

Mike
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Old 20-11-2011, 17:54   #11
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Re: New Revolutionary Rig ?

Quote:
Originally Posted by David M View Post
A foil still has drag, even when it is not producing lift. Is the drag less, the same or greater than a bare single mast?

Just going by looks alone, it appears to have more drag than a bare mast. Could this be a problem in high winds?
I'd be concerned cresting large waves.
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Old 20-11-2011, 18:26   #12
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Re: New Revolutionary Rig ?

At zero angle of incidence the wing mast will have lower drag than a regular mast.

At anchor the question is how well does the mast weathercock to the wind? Unless it is on bearings it will have a little incidence.

Tied up in a marina you are going to have a problem. I doubt the mast is design to rotate 360deg. As the wind clocks around to come from behind, the mast is doing to hit a limit somewhere and start developing significant lift.
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Old 20-11-2011, 18:51   #13
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Re: New revolutionary rig??

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Originally Posted by H.S.Hemingway View Post
hei Mark,
do you think if the small foils feather into wind they still will produce some lift?

for the shifting winds, yes thats definitely something to look at!
I don't know. I don't have any experience with fixed wing sails, and the only knowledge I have is from reading about them and discussing them with a friend currently racing one of the AC45's.

Although a symmetric foil at zero degree of attack produces no lift, it is almost impossible to keep a symmetric foil at zero degree of attack (well, probably not impossible with near-frictionless bearings and other expensive and weighty stuff, but probably impossible for a cruising boat).

Being smaller foils, this problem is probably minimized. And White claims to have done a lot of research and experimentation.

Personally, I hope it all works perfectly because I want to see a sailing world where these are a good solution and are common place.

Mark
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Old 20-11-2011, 20:07   #14
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Re: New Revolutionary Rig ?

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Originally Posted by Adelie View Post
Tied up in a marina you are going to have a problem. I doubt the mast is design to rotate 360deg. As the wind clocks around to come from behind, the mast is doing to hit a limit somewhere and start developing significant lift.
The mast is cylindrical and fixed.
The foil-shaped part is an outer shell that can rotate around the mast. It can feather a full 360 degrees; as far as I can tell it has no limit stops.

The main technical objections I can see being raised are:
- Weight aloft (would have been a problem a while ago, but I would guess Chris expects these to be built in modern ultra-light composites).
- Cost (yup, this one'll be a doozy).
Quote:
Originally Posted by mikereed100
I'm not sure why at anchor the mast has 20% less drag and offshore, when feathered, it has 90% less drag?
Recall that much of the wind drag at anchor is due to the windage of the hulls and superstructure. The way I read Chris's marketing bit, he's saying that an A47 with these things will put about 20% less load on the anchor than an A47 with the standard rig, given the same wind storm for both boats.

90% less drag? This thing's Cd will be around 0.04 to 0.05 when feathered; a cylindrical mast has Cd = 0.47. So yes, 90% less wind drag on the mast sounds about right.
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Old 20-11-2011, 20:40   #15
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Re: New revolutionary rig??

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Originally Posted by pressuredrop View Post
no lift is produced in a symmetrical foil at zero degrees angle of attack (dead into the wind)....
True in theory . . . but the wind direction is not constant, and they found with USA 17 that even very small oscillations in the wind produced a lot of lift, even with the wing freely swinging. When I say a lot of lift I mean that needed a pair of big ribs with several hundred HP to hold against the lift!

The White foils are obviously smaller than USA17's wing, but in the 'real world' there will be rather more lift and more drag than you might expect from zero incidence theory.

There was a previous wing sail cat - walker wing sail - they also found this (more lift and drag when feathering than expected).
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