Reducing or extending wingspan?

[Downunder]

What determines the wingspan of an aircraft?

 

For the sake of arguments, let's say a rectangular wing.

 

And what are the negative/positive aspects of lengthening and shortening it?

 

If shortening, the stall would be higher, the aircraft slightly lighter and cruise faster?

 

I have no idea about roll, stability and a few other things...

 

 

[rollerball]

The thing that immediately changes is wing loading. Messing around with wingspan may, for example, take you outside permitted limits and make you illegal.

 

But the lower the wing loading (higher the wing area) the less lift you need to generate to keep the aircraft in the air with knock-ons therefore affecting stall, climb and cruise speeds as well as engine suitability.

 

A pal here in France, where you can mess about with your ULM (ultralight) almost to your heart's content) stuck some extensions on the wings of his single-seat Weedhopper because he wanted to fly low and slow and burn less fuel. He had such problems floating on his 150 metre strip that he ended up taking them off again

 

This is where I hand over to someone who actually knows what they're talking about.

 

 

[Raytol]

Structurally speaking, reducing the wingspan is safer than lengthening it! The bending "moments" due to lift increase incredibly with extra length. Note that adding winglets to a wing is the same

 

structurally as increasing the span by the height of the winglet. A lot of the benefits of winglets is derived from the increase in aspect ratio of the wing.

 

Usually, the wing span, wing loading/ power loading defines the performance of an aircraft that is mostly chosen to fit into some bureaucratic system.

 

 

[facthunter]

I'm disregarding actually knowing much about it but, here goes..

 

You only need a large wing when you are going slow. As said, at the other end of the scale a very low wing loading( Wt/area) makes it float and be wind sensitive and rougher ride in turbulence but will lift more load, especially at lower speeds. Long wingspans have a better aspect ratio (span Over chord) and are generally more efficient. (better glide angle/ratio) but are harder to make strong, cost more, may have a lower roll rate and take up more hangar space. Nev

 

 

[marcov]

Hmmm, best study aeronautical engineering before messing with wings. Extending wings will significantly change spar loads, drag, stall speed, Vne, and importantly the pitching moment of the wing which can result in reduced or insufficient elevator authority at various speeds. Roll rate would reduce and rudder size may no longer be appropriate as differential aileron drag on outer wings is higher and requires greater rudder force to balance (note large rudders on gliders). So the risks are: damaging or breaking the spar, not having enough power from existing motor to have sufficient climb rate to safely depart(due to increased drag), structural damage from unknowingly exceeding a now reduced Vne, and not having elevator authority(usually as speed increases), yaw instability plus maybe more.

 

Shortening wings can have similar and unexpected side effects, surprisingly it can increase drag for a given airfoil as a higher angle of attack is required to generate sufficient lift. This will bring the wing further up the L/D curve into an unsafe zone- as you noted increased stall speed. Increased cruise speed would only occur if you have sufficient HP from the engine as power requirements increase exponentially with speed.

 

Do lots of study or hire a professional- I have studied this extensively as I am designing a similar change. I am not a qualified engineer and there may be additional issues not noted. Tread carefully.

 

 

[facthunter]

My post is very condensed. You need a large wing also at height.. You climb when you have available excess lift. there are two (basic ) climb situations. Best rate and best angle plus efficient cruise /climb combinations you might use operationally.. Engine cooling and less trip time etc.

 

If you cruise at low level and light weight your angle of attack will be less than most efficient unless you reduce speed to save fuel. (increase range or holding)

 

If you cruise at absolute ceiling you will be at max lift capability of the wing which is also "out of" the best efficiency range, for the airfoil shape. You also have little stall margin to speak of and any deviation from the critical angle of attack, air density or gust loading means an immediate height loss

 

Structurally and aerodynamically you are into complexity. Structurally the wing is the most engineered part of the plane. Nev

 

 

[fly_tornado]

The Tornado comes in 20', 23.5' and 26' wingspan, I'll have to ask the engineers if they changed the structure of the wing. So the weird thing is the wing won't need to be reinforced as it gets bigger because it reduces the wing loading if it's still carrying the same weight. Smaller wings are popular because it gives a higher cruise speed, larger wing higher MTOW.

 

 

[Head in the clouds]

... So the weird thing is the wing won't need to be reinforced as it gets bigger because it reduces the wing loading if it's still carrying the same weight.

That's not correct. The larger span results in an increased bending moment for the same all up weight, so if the spar is still the same thickness it needs to be stiffened, which increases the weight. Even at that increased weight the manoeuvring speed then has to be reduced because the lighter wing-loading would result in overloading the spar.

 

 

[fly_tornado]

I'm not talking 747s, I'm talking in the context of a 1000lb-1200lb plane

 

 

[Head in the clouds]

I'm not talking 747s, I'm talking in the context of a 1000lb-1200lb plane

It doesn't matter what size plane you're talking about - what you said was incorrect. If all else remains the same except you increase the span, it results in an increase of bending moment which means the spar has to be stiffened.

 

 

[facthunter]

I will go with strengthened. Happy to discuss the other. Bill Whitney had good stuff on all this written for most to easily understand. Stiff and flexible have different effects..Thin section wings are scary. The compression loads rather than tension.. Nev

 

 

[Yenn]

Increase the wing span and you increase the wing area. that changes the ratio of area wing to tailplane, making the tailplane less effective. To balance that you could increase the horizontal and vertical tailplane areas, resulting in a plane that has become short coupled, with different flying characteristics.

 

Give us some dimensions of what you are proposing Downunder, Wing span, area tailplane dimensions and location in relation to the wing

 

Normal speeds weight etc. Some of us may like to have a look at what is proposed.

 

 

[Downunder]

Thanks Yenn.

 

When you bring in a particular aircraft (like engines) personal likes and dislikes can railroad the thread away from the topic at hand.

 

Lets say I was day dreaming about how a stol type aircraft could be made into more of a "cruiser" type aircraft. A higher cruise speed.

 

Staying within the RAA 45 kt rule, the wings could be shortened, lowering drag. As there would be a higher stall, rudder and elevator would not need to be so large as there would be no need for such low speed authority? That would allow less drag again.

 

These are just thoughts of the top of my head, so bear that in mind.

 

I have no aviation engineering experience....

 

 

[facthunter]

I can't see that increasing the wingspan would require more horiz stab area. You are the same weight and the centre of lift would move fore and aft the same as before with AoA change. Some earlier designs had very small tail feathers. Don't load them inaccurately. Nev

 

 

[Kyle Communications]

Rans have the S20 Raven it is a rag wing but alu inside. They have just flown the S20 Outbound with a "141" wing it is all alu and a different profile. They test flew the 141 wing on the Raven first and it is smaller in wing area. The Raven actually flew faster but at the slow end seemed to be even better. The initial flights of the S21 seem to be similar in performance although the aircraft is a bit heavier as it is all alu

 

 

 

 

[Kyle Communications]

The S21 was test flown and is still being tested with a 912ULS to compare performance with the Raven

 

 

[Kyle Communications]

This is a first flight report of the S21 with the 912ULS

 

Beautiful day for flight testing the S-21 outbound. It's always fun to get to know a new airplane and this one is no exception. The aircraft shows excellent static margins, light control response, and very well harmonised. Initial performance Impressions: cruise speed is at least 10 faster than the Raven with the 141 wing. Stall is below 40 mph IAS, climb is impressive 1000', and take offs are short, well under 200'.

 

This is the preflight details

 

Outbound Progress Report 16

 

12/13/17

 

Weigh In

 

We have made rapid progress on completing the S-21 Rotax powered prototype. We expect flight testing to begin before the end of the year.

 

The empty weight came in at 783 pounds. That was with the 10 pound heavier fiberglass cowling, but minus paint, we estimate a common empty weight to be around 820. That will allow for AP and paint.

 

There has been significant interest in a SLSA version, using either the Rotax or Titan. We believe a Titan 340 version could be around 930 empty. The estimated price could be 180 to 195 K.

 

Flight Testing

 

We begin flight testing next week and will be sending progress reports as data accumulates.

 

Flush Rivets

 

We are working on this as an option. The structure is suitable for use of flush rivets in most locations.

 

Stay tuned! More to come soon. RJS

 

So rather than lengthen the wing they shortened it and also now the aircraft is +6 and _4 the Raven is +4 and _2

 

 

[facthunter]

It's more common to reduce wingspan to get extra speed and turbulence penetration. Just need longer runways. Nev

 

 

[Garfly]

Yes, that appears to have been the logic behind clipping the original Skyranger's wings.

 

According to the Flylight UK blurb:

 

 

SkyRanger Classic

 

 

With the largest wing of the three models it is capable of flying on the least horsepower, so is the best choice for the smaller engine options. Having a low wing loading it has the best STOL performance too when flying with equal horsepower, and a slightly lower stalling speed.

 

The SkyRanger Classic is also the lowest cost SkyRanger model offering outstanding value for money. it can be customised later when funds permit, with the addition of a large range of retrofit options. (click here for options)

 

 

SkyRanger Swift

 

The SkyRanger Swift is a development from the best selling SkyRanger. Featuring a smaller wing, the Swift benefits from higher cruise speeds and a more comfortable ride in turbulence thanks to the increased wing loading.

 

With a combination of shorter wingspan, and greater torsional strength, the smaller ailerons result in reduced roll loads and increased roll rate, especially noticeable at high cruise speeds over 100mph.

 

Takeoff performance is still in the STOL category, and with the 100 hp 912ULS a max weight takeoff roll on grass is less than 65metres, and a spirited 1200fpm climb, rate rising to over 1500fpm solo. Stalling speed remains a comfortably low 33.5Knots at 450Kg loading, meaning short field landings are still a breeze.

 

Powerful control response right down to stall speed, makes for easy control, and superb crosswind capability.

 

The SkyRanger always did have the highest payload in class, and with the Swift gaining 3Kg from the smaller wing this is increased further. Basic spec aircraft can be built under 250Kg. The owner can then decide whether to benefit from increased payload, or add a full range of extras and avionics, without having to worry about exceeding the maximum weight limit.

 

The SkyRanger features a fast build kit with a level of completeness unbeaten in the industry. New additions for Swift kits are Aerofoil section jury struts as standard, reinforced windscreen, fuselage side batten curving brace, new door catches, pre cut, bent and powder-coated firewall, and a host of other small upgrade items down to details such as coloured rivets to match cowling and tinted screens. There are no hidden extras required to get our kits into the air!

 

New optional extras include a ‘flash dash’ upgrade, with large instrument panel with traditional curved upholstered top, allowing plenty of room for a full high spec avionics fit, and a complementary centre console to clean up the interior look. A 15 second repositional seat kit is also available to enable rapid adjustment . No more need for that pile of cushions when you are the shortest pilot in the syndicate! A thermal screen cabin rear wall is also available to increase the effectiveness of the heater system for those really cold winter days.

 

SkyRanger Information

 

 

[Garfly]

 

 

 

 

Short-Wing Pipers --

 



--back to the Chummy Concept

 



(side-by-side seating, and real speed):

 

Subsequent versions of side-by-side and stretched, 4-seat models models of the Cub were developed, using a shortened wing, trading low-speed lift for more strength and less drag, permitting faster flying.

 

Known, colloquially, as the "short-wing Piper" line, it included compact side-by-side 2-seaters like the PA-15/PA-17 Vagabond (right), and 4-seaters like the PA-16 Family Cruiser.

 

While the Cub, typically cruised at 60mph through the air, the Vagabond (on the same horsepower) could easily cut through the air at 75mph -- a notable advantage when battling the 20-40mph winds commonly encountered aloft. And the Family Cruiser claimed a 100-mph cruise.

 

Piper's short-wing "taildragger" line culminated in the tail-dragging 4-seat PA-20 Pacer (below, right). With engines ranging from 125 to 135 horsepower, the plane's cruise speeds ranged from 100 to 125 mph, while carrying up to four people or full fuel tanks (it couldn't lift both, so some trade-offs were required). The extra speed, and real 4-seat lifting ability, made lightplane flying much more practical for many travelers.

 

 

 

 

 

The short-wing Pipers used the inexpensive, proven, "tube-and-fabric" construction of the Cub, mated to bigger and bigger engines, and larger and larger cabins. But the shorter wings, and overall stubbiness of the planes, gave them rather demanding flying manners, compared to the delightful, forgiving Cub. In particular, the heavily-loaded four-seaters tended to sink rapidly when power was reduced, and bounced around a lot in turbulence. When slowing down or battling crosswinds on landing, most tailwheeled planes were susceptible to "ground-looping" -- the tail swinging around from the back while the plane was moving -- resulting in loss of control. But the stubby short-wing Pipers (many cursed with poor brakes, and all perched on narrow landing gear, guided on the ground by a rather ineffective, sometimes-steerable tailwheel) were especially susceptible to the problem.

 

 

 

 

 

The antiquated stubby, tube-and-fabric construction of the short-wing Piper line was soon eclipsed by the competing 2-seat Cessna 120/140 and 4-seat Cessna 170 (right), whose long, sleek bodies were built with modern "stressed-skin" construction -- using streamlined, lightweight-but-strong aluminum skin for structural strength -- in place of the heavy steel-tube frame, and fabric skin, of the short-wing Pipers and other planes. The "tin-can" Cessnas' long wings and tails gave them greater stability and gentility in the air, along with superior takeoff, climbing and gliding performance. And their shiny, rounded aluminum sides shone with modern elegance. Piper soon noticed Pacer customers drifting away towards Cessna.

 

From: "Piper Aircraft - a quick history"

 

Piper Aircraft History - the Aviation Answer Man

 

 

[eightyknots]

Yes, that appears to have been the logic behind clipping the original Skyranger's wings.According to the Flylight UK blurb:

 

SkyRanger Classic

 

 

With the largest wing of the three models it is capable of flying on the least horsepower, so is the best choice for the smaller engine options. Having a low wing loading it has the best STOL performance too when flying with equal horsepower, and a slightly lower stalling speed.

 

The SkyRanger Classic is also the lowest cost SkyRanger model offering outstanding value for money. it can be customised later when funds permit, with the addition of a large range of retrofit options. (click here for options)

 

 

SkyRanger Swift

 

The SkyRanger Swift is a development from the best selling SkyRanger. Featuring a smaller wing, the Swift benefits from higher cruise speeds and a more comfortable ride in turbulence thanks to the increased wing loading.

 

With a combination of shorter wingspan, and greater torsional strength, the smaller ailerons result in reduced roll loads and increased roll rate, especially noticeable at high cruise speeds over 100mph.

 

Takeoff performance is still in the STOL category, and with the 100 hp 912ULS a max weight takeoff roll on grass is less than 65metres, and a spirited 1200fpm climb, rate rising to over 1500fpm solo. Stalling speed remains a comfortably low 33.5Knots at 450Kg loading, meaning short field landings are still a breeze.

 

Powerful control response right down to stall speed, makes for easy control, and superb crosswind capability.

 

The SkyRanger always did have the highest payload in class, and with the Swift gaining 3Kg from the smaller wing this is increased further. Basic spec aircraft can be built under 250Kg. The owner can then decide whether to benefit from increased payload, or add a full range of extras and avionics, without having to worry about exceeding the maximum weight limit.

 

The SkyRanger features a fast build kit with a level of completeness unbeaten in the industry. New additions for Swift kits are Aerofoil section jury struts as standard, reinforced windscreen, fuselage side batten curving brace, new door catches, pre cut, bent and powder-coated firewall, and a host of other small upgrade items down to details such as coloured rivets to match cowling and tinted screens. There are no hidden extras required to get our kits into the air!

 

New optional extras include a ‘flash dash’ upgrade, with large instrument panel with traditional curved upholstered top, allowing plenty of room for a full high spec avionics fit, and a complementary centre console to clean up the interior look. A 15 second repositional seat kit is also available to enable rapid adjustment . No more need for that pile of cushions when you are the shortest pilot in the syndicate! A thermal screen cabin rear wall is also available to increase the effectiveness of the heater system for those really cold winter days.

 

SkyRanger Information

It is interesting that the long wing version (with presumably the heaviest spar to cope with a larger bending moment) is also the least expensive Skyranger!

 

* I managed to edit -or rather move- my wayward post above. Thanks, Garfly, for alerting me to this before the edit time limit expired.

 

 

[Garfly]

The way the site software handles quotations can be a bit tricky. In this case eightyknots' comment:

 

"It is interesting that the long wing version (with presumably the heaviest spar to cope with a larger bending moment) is also the least expensive Skyranger!"

 

has managed to imbed itself, confusingly, into the original text.

 

Anyway, the long winged version is the original design. I've always presumed that the Swifts and Nynjas, were seen as improvements and the pricing set to reflect the additional design work rather than any savings on metal; and, in the case of the Nynja, probably the different materials used on the fuse. Also the short winged progeny were designed to accept the 100HP Rotax so might have needed beefing up in other departments.

 

Still and all, I did once read that the introduction of the Short Wing Pipers after WWII was partly to do with economising on raw materials. Seemed odd reasoning to me, though, given all else that goes into making planes.