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Old 15-07-2014, 13:59   #16
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Re: Just a few Photos...

Winglets on an aircraft capture something called wake vortices and redirect the airflow to make the overall wing more efficient... To have the same effect on a sail you'd need something approximately the size of an average closet door (on that size boat) at the top AND the bottom of the mast... The closed, or open sail is completely unrelated to vortex degenerators on an aircraft... Jsyk


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Old 15-07-2014, 18:17   #17
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Re: Just a few Photos...

Winglets are a barrier between the relative high pressure on one side of a wing and low pressure on the other. High pressure air wants to curl over the end of the wing to the low pressure air creating a vortex effect, drag, and loss of lift. Relating the aerodynamics of an aircraft wing to a triangular sail is difficult.
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Old 15-07-2014, 18:41   #18
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Re: Just a few Photos...

The vortex doesn't create a loss of lift. It creates more induced drag making the wing less efficient... So to further the point, a winglet (vortex degenerator) makes a wing more efficient. You are correct in your understanding of what creates the vortex ie the change in pressure as a result of accelerated air along one portion of a wing (or sail)... However the vortices created by an aircraft wing are a result of 'extremely' accelerated air... Point of fact, it's usually near the sound barrier... Which is why you'll only see winglets on jet aircraft or on helicopter rotor blades (and even then the addition to rotary wing aircraft is a miracle of composites and a much less apparent version of what you are calling "winglets")

If you notice you'll never see winglets on slower aircraft for that reason. At most some straight wing aircraft merely have bent tips (and that is more about aesthetics 99% of the time). The only exception would be a next gen king air 350 which had winglets added supposedly to assist with the range of the aircraft.. And even there, it's primary function is assumed due to the increased airspeed over the wing generated by the propellers.

There is no point in comparing what begins to approach psuedo advanced aerodynamics of a wing and high speed laminar airflow to a sail that will never exceed the low double digits in comparative "airspeed" over the foil beyond basic Bernoulli's principle. A sail acts like a wing and a wing acts like a sail... The comparison stops there...


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Old 15-07-2014, 18:56   #19
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Re: Just a few Photos...

Sorry for the geek out session... It's not all too often I have the opportunity to write about subjects I'm familiar with... Especially on this forum...




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Old 15-07-2014, 19:04   #20
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Re: Just a few Photos...

DDabs, Beautiful, Beautiful!


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Old 15-07-2014, 19:04   #21
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Re: Just a few Photos...

My mind was just blown.
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Old 15-07-2014, 19:13   #22
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Re: Just a few Photos...

Ddabs... You're boat is absolutely Beautiful... IMHO

Well done


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Old 15-07-2014, 19:58   #23
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Re: Just a few Photos...

Quote:
Originally Posted by seaturkey View Post
You are correct in your understanding of what creates the vortex ie the change in pressure as a result of accelerated air along one portion of a wing (or sail)... However the vortices created by an aircraft wing are a result of 'extremely' accelerated air... Point of fact, it's usually near the sound barrier... Which is why you'll only see winglets on jet aircraft or on helicopter rotor blades

If you notice you'll never see winglets on slower aircraft for that reason.

There is no point in comparing what begins to approach psuedo advanced aerodynamics of a wing and high speed laminar airflow to a sail that will never exceed the low double digits in comparative "airspeed" over the foil beyond basic Bernoulli's principle. A sail acts like a wing and a wing acts like a sail... The comparison stops there...


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While I agree completely that wing tip vortices are a result of the differential pressure the difference in pressure can be created by high speed or high alpha.

Wingtip vortices are quite high in the approach landing phase - the choice for winglets is a trade off on weight versus fuel burn predominantly. Boeing actually produced versions of some "heavies' with no winglets as there are operators who don't want the weight and spend less time in cruise (747-400 in Japan for example).

Newer gen heavies are utilizing advanced winglet design to actually increase lift with a marginal increase in span - creating more load carrying - This is needed as current world airport infrastructure can only accommodate so much wing span.

Many small aircraft are starting to incorporate winglets and many experimentals have had them for a long time (vari-eze). Although in the ligjht sport designs tend to be trailing edge and not full chord devices.

But this is a sailing forum and while it may be useful to stop the vortex that must exists as the air moves up and off the top of the sail the trade off is putting weight aloft - i.e. you could create a wing on top of the mast but the trade off is sticking something up there where you don't want it.
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Old 15-07-2014, 20:32   #24
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Re: Just a few Photos...

Quote:
Originally Posted by seaturkey View Post
Sorry for the geek out session... It's not all too often I have the opportunity to write about subjects I'm familiar with... Especially on this forum...




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No appologies needed. It's great to get bits of information from those with an expertise in other fields. Just you wait until someone brings up apomixis in the genus crepis. I'll jump all over that!
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Old 15-07-2014, 23:41   #25
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Re: Just a few Photos...

A few points:

1. Wingtip vortices are an issue during the approach and landing phase do to the fact that aircraft on approach are sequenced closer together and the higher angle of attack at the wing root along with all the high lift devices combine to create the issue.

2. Winglets are not lift adding devices. They are drag reducing devices which inexorably increases lift by comparison to aircraft that do not have them.

3. I completely agree on the point that 'large aircraft' are utilizing the advantages of aircraft equipped with winglets in part to accommodate airport restrictions... However historically if an aircraft is built that airlines want, airports will concede and adapt - As they always have as planes have gotten larger.. Most recently the 380 is the example of reference.

4. Agreed, this is a sailing forum... However even the notion of adding a winglet (or any vortex degenerating device) to the top of a sail is totally useless from an aerodynamics standpoint... Most simply explained for a winglet like device to be effective it has to be a certain percentage of the chord of the airfoil. Since sails come to a virtual point at the top of a mast it would reduce the width of the "winglet" to the width of the sail at its peak... Essentially making it useless... And yes, hard to get to, and an unnecessary waste of weight in the exact place you wouldn't want any extra...

5. Lastly, most of the light aircraft and experimental aircraft (note: I'm excluding the light sport category bc I know absolutely nothing about it) that had winglet-ish devices were added for stability along the vertical axis of most aircraft... While I'm completely open to the idea that by designing the aircraft this way there were invariably some drag/lift ratio benefits i would imagine it was a secondary benefit... Think SuperEZ in the way of experimental... Winglets.. Kinda. And no empennage or rudder to speak of... Er go stability

6. The only operator I know of that was operating the -400 without winglets was JAL... And that was just weird looking. I have colleagues that are in the -4 and the -8 now and even they're not crazy about the "weird" Japanese versions... Of course that's pure opinion..

Lastly... Since you are apparently dialed in... Why didn't they ever put winglets on the 777? That one always bothered me -

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Old 16-07-2014, 06:13   #26
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Re: Just a few Photos...

Seaturky, the 747-400s operated by JAL and ANA were high capacity domestic versions with greatly reduced range. The decision was made by Boeing not to install winglets on it to save weight. The 777 (and 787 and 767-400) all have raked wingtips. Which are more efficient than winglets.

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Old 16-07-2014, 06:20   #27
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Re: Just a few Photos...

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I find that statement odd seeing as how I'm currently flying the 777 and remember nothing about "raked wingtips."

Not do any of my colleagues currently flying the 767...

The 787... Yes - but on the others... Not so much.


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Old 16-07-2014, 06:21   #28
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Re: Just a few Photos...

That pic btw was taken about 10 minutes ago on the 777 I just landed -


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Old 16-07-2014, 07:00   #29
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Hey 'Dabs'.. nice one..
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Old 16-07-2014, 07:05   #30
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Re: Just a few Photos...

I stand corrected... The 777-300 series does have the raked tips... I'm currently on a -200 series aircraft and my airline doesn't possess any of the later model tri7's...

I remembered during the drive to the hotel...

Also the 747-800 has the blended tips as well...

I suppose my question should be why has Boeing not created a mod for the 777-200 series like they did with the full winglets for the 767's... But alas that is a question not for this forum

Just wanted to correct myself


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