Shoulder wing unpopularity

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delta

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I guess you could consider this a shoulder wing. Beauty is in the eye of the beholder and I'm totally biased but... I think it's a tad better looking than everything I've seen here so far except the cygnet and the one Cr brought up. I'd like to squeze the trigger on this one just 'cause I don't know if it'll work in all the ways I'd like it to....

last1.JPG last2.JPG last3.JPG last4.JPG last5.JPG
 

Aerowerx

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....Now, in an orthodox design with wing first and tail aft the wing spar is usually at where the CG resides too......
Usually? Which leads to the possibility of the spar not being at the CG.

Why not pick an airfoil such that the spar is just behind the design CG, so that the spar is just behind the seats (side-by-side) and the seats are at the design CG? And don't forget a straight leading edge tapered wing could be an advantage.

Sounds reasonable to me. Just because no one has done it is not evidence that it can't be done.
 

Speedboat100

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Why shoulder wing designs are «unpopular»?

Or why are shoulder wing designs rather less common than high and low wing light airplanes?

It is down to packaging, structure, weight and balance. In a light airplane the largest part of the load is the pilot and passengers. This load differs a lot depending on the actual persons. The easiest way to accommodate both a light and heavy load without a large shift in airplane CG is to place the load at the design CG.

Now, in an orthodox design with wing first and tail aft the wing spar is usually at where the CG resides too. Least frontal area and simple construction is to have a low wing with the passenger siting on or straight above the spar. Make the wing strutted and the carry through structure for a high wing is reasonable light and easy to design.

Shoulder wing gets more complicated, expensive and or heavy. My take is then that most airplane designs are specification driven and the virtues of a shoulder wing airplane do make it the chosen configuration that often.

Short Skyvan as a single seater with shoulder wing would be optimal as it has straight wing ( simple to make ) and twin engines bring the CG back. You can load some cargo in the CG. There may be need to trim it...but it has been designed to fly with large static margin.
 

Speedboat100

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I guess you could consider this a shoulder wing. Beauty is in the eye of the beholder and I'm totally biased but... I think it's a tad better looking than everything I've seen here so far except the cygnet and the one Cr brought up. I'd like to squeze the trigger on this one just 'cause I don't know if it'll work in all the ways I'd like it to....

View attachment 90454 View attachment 90455 View attachment 90456 View attachment 90457 View attachment 90458

Yes thick wing sorta becomes "shoulder wing" !

Cool design.
 

stanislavz

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three lifting surface is always an option..

Some of topic. (i got an tailwind virus, third day feel sick) Kind of taliwind in ul class. (450 mtow / 250 empty 65 km/h stall)

Nesmith cougar was build lighter to tailwing, to have ok. landing speed without flaps..

https://en.wikipedia.org/wiki/Nesmith_Cougar

567 kg kg mtow / 283 kg empty with 0-235 (108 kg dry)

The question - If 0-235 substituted by rotax-912 (60 kg dry 48 kg minus ? ) - makes empty weight of 235 kg ? And less fuel / tank - mtow limited to anyway 450kg. And new stall speed is equal to - 85* sqrroot(450/567) = 75.7 km/h. Flaps on Tailwind lowers stall speed from 63mph to 55mph - So in conservative approach - 66.08 km/h with flaps if we assume same CL increase. So add some anti-graviti stripes - and we are at 65 km/h

And - back to topic - with so lightened engine, fuel tank in wings and tricycle gear and with 4309/0006 airfoil - it will place spar after pilot seat.

Hard question - How our max speed will suffer ? sqrroot(450/567) ?

Small problems - here is stated Original tailwind (looks like w10 version) with 55 mph stall at 1300 lbs gw


So - do math com true or not ?
 
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Vigilant1

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Small problems - here is stated Original tailwind (looks like w10 version) with 55 mph stall at 1300 lbs gw
One problem: When the CAFE team tested the Tailwind, they found that it didn't actually stall at those speeds as listed in the POH (that's why they have the note with the asterisk*). They used a very well calibrated airspeed indicator and found that it stalled appreciably faster, and that the POH number's weren't accurate (at least for that plane). If you've got the whole CAFE report, take a look through it for more info.

Edited to add: The CAFE folks found that the Tailwind "clean" stall speed (at 1396 lb) was 61.4 kts. In landing configuration (and 1395 lbs) the stall speed they measured was 57.3 kts.

Here's a link to the CAFE reports, they are excellent.
 
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stanislavz

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One problem: When the CAFE team tested the Tailwind, they found that it didn't actually stall at those speeds as listed in the POH (that's why they have the note with the asterisk*). They used a very well calibrated airspeed indicator and found that it stalled appreciably faster, and that the POH number's weren't accurate (at least for that plane). If you've got the whole CAFE report, take a look through it for more info.
https://buildandfly.shop/wp-content/uploads/2019/03/WITTMAN-TAILWIND-PERFOMANCE-REPORT.pdf

This one part ?

 

stanislavz

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Digged deeper on tailwind stall. And no answer. CAFE report was done on kind of custom one, with even shorter wing...

And more stories on airfoil development from 4309 with flat bottom to 4309/0006 combo. And nice wing tips for better efficiency / low speed handling. Especially when converted from w8 to w8 with w10 wings.. Still briliantly low "frontal area", for such low tech..

Same on Nesmith..
 

Himat

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Usually? Which leads to the possibility of the spar not being at the CG.

Why not pick an airfoil such that the spar is just behind the design CG, so that the spar is just behind the seats (side-by-side) and the seats are at the design CG? And don't forget a straight leading edge tapered wing could be an advantage.

Sounds reasonable to me. Just because no one has done it is not evidence that it can't be done.
Yes, it is possible. The Bolkow Bo 209, MFI-9, MFI-15, SAAB Safari and Mushshak line show. Design a wing with the spar one third from the lading edge the par may be more work, but easier to integrate with the fuselage. The problem is not designing an airplane but selling it. The market for something different from low or high wing is probably pretty small.
 

Aerowerx

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Yes, it is possible. The Bolkow Bo 209, MFI-9, MFI-15, SAAB Safari and Mushshak line show. Design a wing with the spar one third from the lading edge the par may be more work, but easier to integrate with the fuselage. The problem is not designing an airplane but selling it. The market for something different from low or high wing is probably pretty small.
Maybe so, but the problem being discussed was the design, I thought, not marketing.
 

Lendo

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Himat,
For a Tandem configuration, we would like the rear passenger or Pilot to have his feet straddle the seat of the front pilot to keep their weight closer together for weight and balance. However the Carry Through Spar may need to go where the rear Pilot's feet are, so that makes the rear Passenger/Pilot more rearward, extending the Cockpit length.
Alternatively you may use a more heavier and more complex arrangement (forget the name of it) that ties the wing Spar to the fuselage walls. Some larger Passenger Planes have that arrangement.

For a pusher I've seen the Mid Wing Spar attached to the Engine Firewall.
George
 

Aerowerx

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... However the Carry Through Spar may need to go where the rear Pilot's feet are, so that makes the rear Passenger/Pilot more rearward, extending the Cockpit length....
Not really.

I thought we were talking about a shoulder wing. The spar carry through would be higher up between the front pilot seat and the rear pilot's instrument panel. The rear pilot's feet would then go under the spar carry through.
 
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