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Glider design - low aspect ratio wing

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Martin_K26/05/2020 16:44:07
169 forum posts

I think I recall a thread about a glider with a low aspect ratio wing. Inspired by a bird. There was also an enlarged version. I cannot remember the name of the model.

Assuming my memory is not playing tricks on me, can somebody remind me of this model / thread?

J Moyler26/05/2020 17:41:19
147 forum posts
56 photos

I believe the models in question are by Peter Miller the Easter Eagle and Easter Eagle Senior Link.

Thread

Hope this helps.

 

JM

Edited By J Moyler on 26/05/2020 17:45:34

Martin_K26/05/2020 17:50:46
169 forum posts

Thanks very much JM, I'm not losing my marbles!

A spelling typo in the second paragraph of the thread (ratio/ration) probably defeated searches.

Peter Miller26/05/2020 18:40:37
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I can tell you that they are great thermal flyers.The current owner loves them.Especially when other glider pilots say "There is no lift around" and go home while the Easter Eagle senior spends half an hour floating around at height.(Half an hour is the limit for his neck muscles.)

Peter Miller26/05/2020 18:59:44
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I see that Sarik Hobbies do not list the EE Senior so if you want plans Ican let you have PDF files. Just PM me

Martin_K26/05/2020 19:45:48
169 forum posts

Peter, thanks for chiming in.

I had forgotten just how big the Eagle Senior is, probably not practical for me currently.

One point of clarification please. Sarik appear to only show plans for the carbon tail boom Easter Eagle. Are plans available for the wood fuselage, 55inch span version?

Richard Clark 226/05/2020 19:53:51
223 forum posts
Posted by Peter Miller on 26/05/2020 18:40:37:

I can tell you that they are great thermal flyers.The current owner loves them.Especially when other glider pilots say "There is no lift around" and go home while the Easter Eagle senior spends half an hour floating around at height.(Half an hour is the limit for his neck muscles.)

The hawks (an eagle is merely a large hawk) and the closely related vultures (the falcons are not closely related) are probably the best soarers in the world. Why? - several million years of evolution. Gulls, which are high aspect radio, can glide fast but rarely, if ever, soar. Nor do albatrosses, also high aspect ratio.

From your chosen name of the models you obviously know this and were using the eagle/hawk aerodynamics, wingtip taper and all, but from their appearance NOT trying to make a convincing fake eagle.

I rather admire you for this.

Why do so many designers ignore such stuff? In another area of bird performance a peregrine falcon (peregrine mean wanderer - equals long distance traveller) can cruise at 100 mph for 100 miles on the energy from one mouse.

What model plane can do that?

john stones 126/05/2020 20:08:22
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A Pushy Cat. cat

Colin Leighfield26/05/2020 20:27:33
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Don’t tell the gulls in Calpe, Spain, where we are frequently, that they don’t soar. For some reason on every day in late afternoon they congregate in large numbers flying in circles above the bay and fly upwards. They arrive close to the slopes of the 332 metre high “Penon de Ifach” , a huge rock that protrudes into the sea for about half a kilometre. They seem then to be using rising air currents to continue to circle until they are above the peak, in old money more than a thousand feet up. They don’t stop there, although some seem to progressively hold altitude at different levels and circle until eventually at probably around 1,300 ft there is just one and at that point they scatter and disperse in all directions. It’s an astonishing sight that I have been observing for many years, aometimes from the top of the Penon. Besides that they frequently use air currents to soar for prolonged periods over the bay. It’s clearly not related to feeding because they do that at sea level. Also albatrosses most definitely soar, they spend huge periods, days and weeks, in the air, almost certainly sleeping on the wing. Probably the best soarers of all birds. Low aspect ratio wings such as seen on the famous “Leprechaun” glider definitely are good for floating, but when it comes to maximum soaring efficiency the top sailplane designers of the world certainly don’t consider low aspect ratios as even starting to compete. Gulls and related birds are among the best soarers in the bird kingdom.

 

Edited By Colin Leighfield on 26/05/2020 20:29:33

Peter Miller26/05/2020 21:13:51
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Posted by Martin_K on 26/05/2020 19:45:48:

Peter, thanks for chiming in.

I had forgotten just how big the Eagle Senior is, probably not practical for me currently.

One point of clarification please. Sarik appear to only show plans for the carbon tail boom Easter Eagle. Are plans available for the wood fuselage, 55inch span version?

I dif a versipn with a balsa fuselage to Sailplane and Electric in the uSA but do not have the plans for that.However if you simply used the Sarik plans but used the EE Sr plan scaled down for contruction details that would work fine.

THe balance on the smaller one would be correct as it used a Speed 600 size motor and a 6 cell Nicad

Richard Clark 226/05/2020 21:36:01
223 forum posts
Posted by Colin Leighfield on 26/05/2020 20:27:33:

Don’t tell the gulls in Calpe, Spain, where we are frequently, that they don’t soar. For some reason on every day in late afternoon they congregate in large numbers flying in circles above the bay and fly upwards. They arrive close to the slopes of the 332 metre high “Penon de Ifach” , a huge rock that protrudes into the sea for about half a kilometre. They seem then to be using rising air currents to continue to circle until they are above the peak, in old money more than a thousand feet up. They don’t stop there, although some seem to progressively hold altitude at different levels and circle until eventually at probably around 1,300 ft there is just one and at that point they scatter and disperse in all directions. It’s an astonishing sight that I have been observing for many years, aometimes from the top of the Penon. Besides that they frequently use air currents to soar for prolonged periods over the bay. It’s clearly not related to feeding because they do that at sea level. Also albatrosses most definitely soar, they spend huge periods, days and weeks, in the air, almost certainly sleeping on the wing. Probably the best soarers of all birds. Low aspect ratio wings such as seen on the famous “Leprechaun” glider definitely are good for floating, but when it comes to maximum soaring efficiency the top sailplane designers of the world certainly don’t consider low aspect ratios as even starting to compete. Gulls and related birds are among the best soarers in the bird kingdom.

Edited By Colin Leighfield on 26/05/2020 20:29:33

I didn't know that. But hawks/vultures spend a huge amount of time soaring. It's vultures main way of finding food. Maybe their only way. So they are very good at it.

And if anyone believes glider designers are better at this stuff than millions of years of evolution I think they are wrong. Humans can be very conceited, despite we've not been around anywhere near a long enough time to show we are a 'successful' species. You of course may disagree.

Colin Leighfield26/05/2020 22:35:50
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I never said they were Richard. Of course Hawks and Vultures spend huge amounts of time soaring. However you suggested that gulls and albatrosses don’t. That is not correct, that’s all and the albatross is known as the best soaring bird in the world, able to travel 10,000 miles in one flight. Look it up.

Edited By Colin Leighfield on 26/05/2020 22:36:18

Robin Colbourne26/05/2020 23:26:14
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Who says Johnny don't soar?*

*Johnny = Jonathon Livingston Seagull

Edited By Robin Colbourne on 26/05/2020 23:27:02

iflylilplanes27/05/2020 02:32:53
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34 forum posts

I remember a glider called "LARS" (Low Aspect Ratio Soarer) old design from 1976.

Full size plans are available here for download **LINK**

I would change the section for a later/better version.

Cheers,

Dave

Richard Clark 227/05/2020 06:57:40
223 forum posts
Posted by Colin Leighfield on 26/05/2020 22:35:50:

I never said they were Richard. Of course Hawks and Vultures spend huge amounts of time soaring. However you suggested that gulls and albatrosses don’t. That is not correct, that’s all and the albatross is known as the best soaring bird in the world, able to travel 10,000 miles in one flight. Look it up.

Edited By Colin Leighfield on 26/05/2020 22:36:18

So I was wrong. Fine. This site is not a competition where we 'win' threads.

One further thought (just thinking aloud) about our gliders, both model and full size. Modern ones have quite a high sink rate but also high speed so they have a good glide angle. Great for covering distance. But for just 'staying up for a long time' the larger wing area/low wing loading given by low aspect ratio is probably better.

So there is no 'best soarer'.

It's all down to what (some of) us humans want for our 'play' or in which way evolution sent a group of birds food gathering behaviour in a variety of circumstances.

Peter Miller27/05/2020 07:22:05
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Posted by Richard Clark 2 on 27/05/2020 06:57:40:
Posted by Colin Leighfield on 26/05/2020 22:35:50:

I never said they were Richard. Of course Hawks and Vultures spend huge amounts of time soaring. However you suggested that gulls and albatrosses don’t. That is not correct, that’s all and the albatross is known as the best soaring bird in the world, able to travel 10,000 miles in one flight. Look it up.

Edited By Colin Leighfield on 26/05/2020 22:36:18

So I was wrong. Fine. This site is not a competition where we 'win' threads.

One further thought (just thinking aloud) about our gliders, both model and full size. Modern ones have quite a high sink rate but also high speed so they have a good glide angle. Great for covering distance. But for just 'staying up for a long time' the larger wing area/low wing loading given by low aspect ratio is probably better.

So there is no 'best soarer'.

It's all down to what (some of) us humans want for our 'play' or in which way evolution sent a group of birds food gathering behaviour in a variety of circumstances.

And that was the point of the Easter Eagles. THey are meant to go up on a gnats belch of lift and not fly round fast.They are based (as I have said many times) on the Vultures and Condors (I know, a type of vulture) and regardless of what anyone says they do the job that they were designed for very well.

Martin_K27/05/2020 07:22:42
169 forum posts
Posted by iflylilplanes on 27/05/2020 02:32:53:

I remember a glider called "LARS" ......

Thanks Dave. Coincidentally my starting point for researching a new build was a search on OuterZone. My criteria, rudder, elevator, throttle, 3 channel motor launch gliders, clearly excluded the LARS pure glider.

The plans I found that I liked are all variations on the same theme, which got me wondering about the contrarian view.

I now have enough study material to keep me busy!

Colin Leighfield27/05/2020 09:54:14
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This is the one I used to drool over as a kid, a long time ago! 103” span, aspect ratio 6:1. A legendary glider as they used to be, a proper “floater”! Designed by Dick Twomey and published by APS. Now in Outerzone.6d94fc5b-f64d-4779-a50d-58ef0e842c0a.jpeg

Andy.I27/05/2020 10:31:44
91 forum posts
1 photos

Speaking of birds' wings, glider design, albatrosses etc, some of you might find these interesting.

**LINK**

https://www.youtube.com/watch?v=bCwtcDNB15E&t=234s

There are a number of videos on Youtube featuring Al Bowers and Prandtl wings with some surprising revelations.

Edited By Andy.I on 27/05/2020 10:34:50

Simon Chaddock27/05/2020 11:52:40
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I have to agree with Peter you certainly don't need aspect ratio to thermal.

If you think about it a low sink rate and a low speed will allow you, if you have the skill, to keep near the centre of a thermal where the air is rising fastest.

If you can build light enough almost any shape will thermal but the down side is of course you can't then get anywhere else particularly fast or far but with efficient electric power this can be overcome.

My own version of this is my 40" Depron Super Cub which even power off I have had to "bail out" of a thermal on more than one occasion simply because it was getting too high and too far down wind.

242gB

Of course the fact it only weighs 242 g 'ready to go' certainly helps. wink 2

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