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Why is it (not) so...?


Marty_d
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I'm not a trike enthusiast (despite having flown a hang glider in the distant past), but just curious.

 

Why hasn't someone built a trike wing out of aluminium?

 

Yes, you'd lose the ability to pack it away - but from what I've seen, many trikes seem to spend their non-flying time in a hangar anyway.

 

Weight - would it be much more? Spars and ribs made of 0.025" 6061-T6, skinned with 0.016"... how would that compare with rag and tube?

 

And being made from aluminium, no more need to worry about mice/moths/fading/brittleness/battens deforming / whatever else worries fabric.

 

Now tell me why it's a bad idea... 052_no_way.gif.ab8ffebe253e71283aa356aade003836.gif

 

 

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How do you suggest control would be effected on such a device ?

Do current trikes alter the wing geometry for control? I assumed that they were purely weight shift, the same as hang gliders. Nothing changes there.

 

 

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Billow shift, leach, lufflines / reflex and floating crosstubes all play a part in controlling a trike (which wouldn't be feasible with your suggestion).

 

There are rigid-wing hangliders but they use control surfaces

 

 

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Do current trikes alter the wing geometry for control? I assumed that they were purely weight shift, the same as hang gliders. Nothing changes there.

So did I, but yes, apparently the wing geometry changes with weight change. A bit more complicated than it seems.

 

 

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There you go then... this is why I love this site! Always learning.

 

I guess control surfaces would be needed then, which adds to weight & complexity. Still doable but maybe not enough reason to do it.

 

 

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There you go then... this is why I love this site! Always learning.I guess control surfaces would be needed then, which adds to weight & complexity. Still doable but maybe not enough reason to do it.

How could al sheet be anywhere near as light as dacron?

 

 

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It wouldn't be. But then again I've always wondered why they need a 100hp engine.

The short answer is...they don't need that much power. I had a trike with an 80hp Rotax and they're grotesquely overpowered. I used to cruise at about 3,900 RPM because anything higher than that and you were climbing, even with full fuel and 2 on board. There are faster wings than the Cruze wing I had, which require a bit more push, but still 80hp is waaay more than they can use.

I guess the reason is that people want the reliability and fuel economy that a 4 stroke engine gives and the Rotax 912 is the smallest (HP wise) most reliable engine. I know there are trikes that have the 912S 100HP and IMHO, that's just ridiculous. I think if you had a trike with that engine and that would cruise at 85-90Kt, it wouldn't be very comfortable having your arms out in that kind of slipstream, on the bar for very long.

 

Also, I've heard it said many times that the Rotax engines are happiest if they're worked reasonably hard. The reccommendations seem to go along the lines of cruising at 5,000RPM or more. At 3,900 the enging is just stooging along and is unlikely to ever get the oil temp to 100 Deg C as Rotax reccommend.

 

 

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Why would it need control surfaces? If you were just substituting the dacron for ali it is still a weight shift wing.

 

Other than ease of transport for the dacron wing cost of construction materials and time to build not to mention increased weight. No doubt someone somewhere has tried this in the past.

 

 

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The short answer is...they don't need that much power. I had a trike with an 80hp Rotax and they're grotesquely overpowered. I used to cruise at about 3,900 RPM because anything higher than that and you were climbing, even with full fuel and 2 on board. There are faster wings than the Cruze wing I had, which require a bit more push, but still 80hp is waaay more than they can use.I guess the reason is that people want the reliability and fuel economy that a 4 stroke engine gives and the Rotax 912 is the smallest (HP wise) most reliable engine. I know there are trikes that have the 912S 100HP and IMHO, that's just ridiculous. I think if you had a trike with that engine and that would cruise at 85-90Kt, it wouldn't be very comfortable having your arms out in that kind of slipstream, on the bar for very long.

 

.

Scott,

I'm sure that is the case at sea level, but up in the mountains on a hot day could be different.

 

I know of one case in the U.S where a Reflex wing ( not sure which one, either the Sport or Competition, but both are quite slippery) was fitted to an 80hp equipped Tanarg. Apparently it crashed due to its inability to climb out of a down draft.

 

Regards Bill

 

 

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Why would it need control surfaces? If you were just substituting the dacron for ali it is still a weight shift wing.Other than ease of transport for the dacron wing cost of construction materials and time to build not to mention increased weight. No doubt someone somewhere has tried this in the past.

See posts #5 and #6, apparently it's not that simple.

 

 

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Billow shift, leach, lufflines / reflex and floating crosstubes all play a part in controlling a trike (which wouldn't be feasible with your suggestion).There are rigid-wing hangliders but they use control surfaces

Billow shift, leach control are performance based designs, less billow faster wing less stable, more billow slower wing more stable.

 

luff lines are added to help stop sail inversion when CP moves in steep dives. Same with reflex built into the sail causes wing to want to pitch up with speed. Moyes kites were notorious for inverted sail back in the late seventies. Known as luff dives and killed quite a few pilots back then. Floating cross tubes are like power steering take a lot of load off the bar during steep turns.

 

I cannot remember any ragallo based HG flex wings having control surfaces. The only types with any type of control surfaces are the traditional type wings like the Icarus series and Easy Riser that are still weight shift in pitch but use tip rudders for roll and yaw. the Pfledge was a semi flex wing high aspect ratio with tip rudders but weight shift for pitch. The Mitchell B10 non powered version again high aspect wing with tip rudders and elevons and was a tin wing.

 

if you took a trike wing and built it from alloy it would still be weight shift. any CG difference would mean hanging from a different point on the keel.

 

And if you made it with control surfaces you cant fly it under HGFA rules.

 

 

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Billow shift also helps the roll the wing by allowing the trailing edge to raise on the down going wing and lower on the upper wing - luff lines can also promote this effect.

 

Therefore less billow shift would make the wing more stable rather than less - without any billowshift a purely weightshift wing would be impossible to turn.

 

These are the type of rigid wing hanglider I was referring to http://www.aerola.com.ua/index.php?page=hang_gliders&id=35&type=general

 

I'm pretty sure that they would come under HGFA jurisdiction

 

Cheers

 

John

 

 

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Still weight shift for pitch. Still under HGFA, must be foot launch as well. weight limit too from memory. Looks like a very modern Fledge.

 

The early variable billow HGs that I flew adjusted the cross bars fore and aft along the keel. Used mainly for speed control. eg tighten up the wing (less billow) and speed up in between thermals for instance. Loosen off (more billow) and fly slower and tighter flatter turns in thermals. Easier to handle and used for landing as well.

 

 

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  • 2 weeks later...
Still weight shift for pitch. Still under HGFA, must be foot launch as well. weight limit too from memory. Looks like a very modern Fledge.The early variable billow HGs that I flew adjusted the cross bars fore and aft along the keel. Used mainly for speed control. eg tighten up the wing (less billow) and speed up in between thermals for instance. Loosen off (more billow) and fly slower and tighter flatter turns in thermals. Easier to handle and used for landing as well.

No change today Ozzie.... the higher performance wings (single surface adn novie intermediate wings don't bother generally) still use VB or as it is called now VG 'Variable Geometry'. The cross bar which joins in the middle via ball joint or plates is pulled back, pushing out (forward) at the leading edge/x bar junction, changing nose angle and tightening the wings, More stable in roll (and harder to turn or correct non-pilot induced turns) but less pitch stable due to reduced washout and nose angle. Less drag means better glide and at higher speeds.

 

 

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....... without any billowshift a purely weightshift wing would be impossible to turn.......Cheers

John

That more than anything else is the reason. If the wing was rigid the only way to turn would be to use pitch when the wing is on an angle and for the most part the majority of the pitch will result in altitude change not direction change......

 

The comment around Hp.....my trike is an older 582 so 65Hp and it with the fastest wing available at the time still climbs very handily......with a 100hp motor I wonder is someone foolishly climbed at full power if the angle of climb would be so much that the pilots ability to pitch the nose down in the event of an EFATO would be compromised and the trike could then end up back sliding and tumbling.....A tumbling trike is no fun at all...google trike and tumble on youtube (first result) to see what I mean......Its not that trikes are dangerous, any aircraft can be put into a situation where it can kill you...you have to try damn hard with trikes but it can be done!

 

 

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