Men in Sheds....

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Great Britain
JamesL
Posts: 397
Joined: Mon Dec 04, 2006 4:27 pm
Location: Warwickshire UK

Men in Sheds....

Postby JamesL » Sat Jan 13, 2018 2:22 pm

Just came across this, clearly black has a rival for the fastest colour. ..

https://m.youtube.com/watch?v=YajmqdW9dos

And happy new year!

James

England
SP250
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Joined: Mon Sep 09, 2013 2:01 pm
Location: North Shropshire

Re: Men in Sheds....

Postby SP250 » Sat Jan 13, 2018 3:22 pm

Yes, good eyesight needed, but unpowered RC gliders are even faster https://www.youtube.com/watch?v=hFPJ6DUAY10
John M

Great Britain
JamesL
Posts: 397
Joined: Mon Dec 04, 2006 4:27 pm
Location: Warwickshire UK

Re: Men in Sheds....

Postby JamesL » Sat Jan 13, 2018 4:53 pm

That Is insane... How do they do it and how do they make the glider strong enough?

England
SP250
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Re: Men in Sheds....

Postby SP250 » Sat Jan 13, 2018 7:43 pm

Its called Dynamic Soaring.
You fly the glider in the curl over behind a ridge and use the same physics as Albatros's (Albertri??) use to cover long distances without flapping their wings.
Basically you fly an elliptical shape loop from down below the curl over and as the model gains altitude it gets an energy boost from the up draught.
Keep on doing it and more energy is put into the model and it gets faster and faster.
The Albatross just dips a wing, gains the energy and flys a bit further and does it again to fly a bit further.

They make the glider strong enough because it has solid carbon upper and lower wing skins and a huge spar system in the wing.
They are around 2.5 to 3.0 metre wingspan and weigh 15kg to 30kg.
My slow, thermal soaring moulded gliders of that sort of size weigh around 3Kg.
John M

Scotland
Grip Fast
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Joined: Sat Jan 14, 2012 6:15 pm
Location: North Bucks

Re: Men in Sheds....

Postby Grip Fast » Sat Jan 13, 2018 10:13 pm

That's made my brain hurt - trying to understand dynamic soaring. SP250, you mention curl over in the lee of the slope, and I'd kinda convinced myself of how it works. But on further reading, the mechanics of DS seem to rely on two different air velocities, such as between the dead air in the shelter behind the hill, and the wind blowing horizontally (more or less) off the top of the hill. Identifying the boundary layer between said dead area and the wind seems key to successful DS, according to the article below. So I'm a bit confused by that.

The gliding club, where I fly, has a long ridge (about 300 to 350 feet high) that works well in a stiff westerly. In an easterly, we're in the lee of the hill, and that is usually proper rubbish. Occasionally, in an easterly, we do find a band of lift, parallel to the ridge, but a few hundred metres downwind of it. But I'm not aware of any hint of lift close to the ridge in an easterly - maybe we just can't get close enough. Having said that, some of the guys have found lift high above and inexplicably close to the lee of mountains.

Interesting that modern gliders have tanks in the wings and tail that can be filled with water to increase wing loading so we can fly faster cross country. So I get the bit about DS gliders needing to be very heavy.

https://www.rc-airplane-world.com/dynamic-soaring.html

England
SP250
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Location: North Shropshire

Re: Men in Sheds....

Postby SP250 » Sat Jan 13, 2018 10:31 pm

Grip Fast

The US explanation isn't quite complete in the link you posted.

There is a rotor behind the hill not show in the link diagram - approximating to the red dotted path for the glider and that is the rotor component of the wind curl over. i.e. it has a down and an up component, both of which add the energy to the glider.
Which is why in your full size glider you get lift in the lee of the slope but much further back.
Normal slope lift at point A, DS at place shown.

Hope that helps some, and its too late with a nice Belgian Trappist beer to engage brain any more on a Saturday night.

Cheers John
John M

Scotland
Grip Fast
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Joined: Sat Jan 14, 2012 6:15 pm
Location: North Bucks

Re: Men in Sheds....

Postby Grip Fast » Sun Jan 14, 2018 8:46 am

Thanks John. Yes, it only makes sense to me if there is rotor involved. I spoke to a fellow glider pilot who also flies r/c gliders. He too confirmed the need for rotor in the equation, when dynamic soaring.

[Edit] Sorry, got a bit carried away / over-excited by gliding and trampled on the original point of the thread, which I did find interesting, until I saw the fastest r/c glider video. :oops:
Last edited by Grip Fast on Sun Jan 14, 2018 10:03 am, edited 2 times in total.

Scotland
Grip Fast
Posts: 658
Joined: Sat Jan 14, 2012 6:15 pm
Location: North Bucks

Re: Men in Sheds....

Postby Grip Fast » Sun Jan 14, 2018 9:51 am

JamesL wrote:Just came across this, clearly black has a rival for the fastest colour. ..

https://m.youtube.com/watch?v=YajmqdW9dos

And happy new year!

James


Wow, that's impressive, probably because of the noise on top of the speed. I was interested to see it was launched by a catapult/bungee mechanism. I like the hollow moaning sound the engine was making just before takeoff.

Great Britain
dave the german
Member
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Location: North East

Re: Men in Sheds....

Postby dave the german » Sun Jan 14, 2018 6:29 pm

Grip Fast wrote:
JamesL wrote:Just came across this, clearly black has a rival for the fastest colour. ..

https://m.youtube.com/watch?v=YajmqdW9dos

And happy new year!

James


Wow, that's impressive, probably because of the noise on top of the speed. I was interested to see it was launched by a catapult/bungee mechanism. I like the hollow moaning sound the engine was making just before takeoff.


there's a guy having a pi$$ at about 1.25!! :lol:
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