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Old 08-15-2007, 09:58 AM   #15
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I am not a physicist, but it strikes me that from the perspective of sailing, the air-tab proposal is regressive technology. An aeroplane wing is largely a rigid structure and the tabs are included to distort the character of the wing to provide a change in lift or drag.

A yacht's sail is not so restricted and with the application of sheets, a vang, outhaul, furling foils, etc, we can change the shape of the sail to suit the conditions, in an almost infinite variety of ways.

It seems to me that the addition of tabs to a wing, is a very inefficient way of attempting to copy the efficiency dynamics of a sail, albeit in a different plane.

Surely the appropriate way to address the shortcomings of aeroplane wings by comparison to a sail, would be to increase the flexibility and fluidity of the wing's covering in order that it could change its angle, volume, aerodynamicism and length such as is used in the swing wing, in a very limited manner.

Adding tabs to a sail would suggest that we are trying to make sails more rigid and less adaptable to sailing conditions.

But, as I said, I am not a physicist and it has to be said I was already wrong once this year. (Blasted South African RU team)

David.
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Old 08-17-2007, 09:36 AM   #16
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Hi KiwiAussie, I understand the principle of the whole affair, but it doesn't make sense to me to 'hobble' a sail in such a manner. I took a look many years ago at a boat designed by Cousteau when it visited Oz. It had rigid sails and, I seem to remember, one of the Club Med floating/sailing resorts was a huge ship also with computer controlled rigid sails.

One of the incarnations of the YellowPages Endeavour trimaran which broke the world speed sailing record also had a rigid wing/sail....I think. Perhaps I should not be so lazy, and have a look on the 'net.

Cheers

David.
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Old 08-17-2007, 11:10 AM   #17
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Thanks KiwiAussie,

Them's the ones...now I feel really small.

Ta

David.
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Old 10-08-2007, 05:21 AM   #18
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Quote:
Originally Posted by Auzzee View Post
Hi KiwiAussie, I understand the principle of the whole affair, but it doesn't make sense to me to 'hobble' a sail in such a manner. I took a look many years ago at a boat designed by Cousteau when it visited Oz. It had rigid sails and, I seem to remember, one of the Club Med floating/sailing resorts was a huge ship also with computer controlled rigid sails.

One of the incarnations of the YellowPages Endeavour trimaran which broke the world speed sailing record also had a rigid wing/sail....I think. Perhaps I should not be so lazy, and have a look on the 'net.

Cheers

David.
The air tabs would NOT be adde3d to the sail. They would be added to the vessal on the rear. This would cause the draft to come back intot he sail on onto the rear of the vessal. I just am not sure the speeds would be great to effect the air.

To get an idea. The tab effects the wind into a rolling aspect that come back at you instead of throwing it off to the sides.
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Old 10-08-2007, 05:42 AM   #19
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"One quick question to an aero-indstry expert...and this is way off topic but please indulge me. I have always wondered how a pilot can simply just turn his turbines off after landing? On turbine ships we used to engage turning gear after berthing. This gear (an electric motor) turned the turbines at very slow speed so that the blades cooled down at an even rate. Without engaging turning gear the blades would warp. It took about two days for the blades to cool down. As an indicator, the last turbine ship I was on had H.P. turbines operating at 750 C and 550 p.s.i. The L.P. turbine was, of course, operating at lower temperatures but was larger. The other difference was that these were steam turbines and not gas turbines as in aircraft where temperatures are even higher. How then do aircraft avoid turbine blade distortion?"

I am no expert.

Most do not just shut them off that I know of. Many are pre cooled during landing with back pressure (air brake) and on taxiing with cryogenic fluids. The Turbo fan is also lubricated with synthetic fluids that hold heat well. Turbine lube is VERY interesting. It handles VERY HIGH heat and cools very fast. It is one of the best insulating processes there is.

Many THINK they are air cooled. They are, but they are also lubricant cooled. The fan will cool on auto cycle in about 10-12 mins. My fans will fun on low rpm for 10-12 min AFTER shut down. To cool the turbines. Most of this is to send off the heat from the lubricants. Compressed oxygen is used as well to cool the lubricants.
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Old 10-08-2007, 09:49 AM   #20
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Thanks for the reply daytrader. One learns something new every day.

The oil cooling bit is interesting. For some reason most people think that oil is only for lubricating but even in diesel engines it is a very important part of the coling process.

Alow me to differ with you o one point though. From my point of view you are an expert!

Thanks a lot for explaining to me something which has bafled me for a long time. I will be making a couple of flights this afternoon, just by chance, and they will be that much more enjoyable now that I know more of what is going on.

Thanks again
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