UL SAILPLANE - Footlaunchable, foldable

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renxxx1981

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Jan 5, 2013
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48
Location
italy
Hi Folks, in the continous research of the subject "ultralight glider , microlift glider, etc" I've found that a russian ultralight sailplane concept adopted a nice airfoil for an open structure , with almost straight lines from the "d-box" to the trailing edge: TSAGI R-3a
http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?num=1131735157/60
Additionally I've found a very cool article about open structure wings (ribs and dbox) https://coxengines.ca/cox/www.mh-aerotools.de/airfoils/ribs.htm
 

ultralajt

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May 9, 2009
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1,575
Location
Slovenia
Well... where we are?

It was a pretty long time of having no activity on this Sailplane project.
Meanwhile I got a job and almost one year I am working in SolidWorks there already. I am very much tempted to put my Sailplane project in SW as this way I can easily change so many parameters without redoing all all over and again. For instance, If I change the wing airfoil, with little luck, all ribs will automatically changes accordingly, and off course all the shop drawings. It works fine most of the time if you don't "push the envelope" (changes of some design parameters) too drastically. :)

I believe, that my project need to be refined while designing parts in SW a little more in direction to be easily manufactured at home workshop. As laser cutting and waterjet are more accessible as ever, I will certainly use more parts done this way (waterjet service is practically in my neighborhood..I use it a lot in my daily job).

What I should keep as it was?

- Easy fold-able and transport on top of the car
- Lightweight and relatively short wingspan

I will add a possibility for electric propulsion.

So much for now... at my morning coffee... ;)
 

ultralajt

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May 9, 2009
Messages
1,575
Location
Slovenia
Hi Folks, in the continous research of the subject "ultralight glider , microlift glider, etc" I've found that a russian ultralight sailplane concept adopted a nice airfoil for an open structure , with almost straight lines from the "d-box" to the trailing edge: TSAGI R-3a
http://www.reaa.ru/cgi-bin/yabb/YaBB.pl?num=1131735157/60
Airfoil R-III was and it still is widely used on Russian planes, both motor and gliders, mostly of vintage origin and these-days home-built and ultralights.
 

b7gwap

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Joined
Sep 1, 2014
Messages
334
Location
UT
Ultralajt- can you give us a quick overview of what your design looks like at this stage? Are you still planning to do a Dacron sail with battens draped over a single Aluminum tube spar à la HG? Or did you decide to go Composites?
 

ultralajt

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May 9, 2009
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1,575
Location
Slovenia
Ultralajt- can you give us a quick overview of what your design looks like at this stage? Are you still planning to do a Dacron sail with battens draped over a single Aluminum tube spar à la HG? Or did you decide to go Composites?
Composite D box , collapsible internal structure with Dacron sleeve for covering, and detachable flaperons.
 

ultralajt

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May 9, 2009
Messages
1,575
Location
Slovenia
When I saw this "Flyer" electric car, I liked instantly the shape of cockpit they made. It has narrow width at lower half and widen "sidewall channels" at upper part, so shoulders and hands can have enough space. I can use such cross section shape on my glider cockpit.
Hutter 28 uses wing roots carman for making space for pilot shoulders and hands, so the rest of fuselage section can be narrow. As fuselage must slice the air, the lower the cross section, the less drag it produced by doing that.... This is what I am aiming for.

105254230-Flyer-by-Kitty-Hawk.1910x1000.jpg
 
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SMORGAN

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Joined
Dec 9, 2016
Messages
22
Location
Sydney Australia
Mitja

Glad you are back on the project, I have been following it since the start..

Im would like to understand more about the airfoil selection, there seems to be two approaches.

The Kanja airfoil is similar to that of the Impact and Atos flying wing hang gliders, you have a sketch on your website showing the comparison.

These have the maximum depth well forward and I presume have positive pitching moments for use on the flying wings.

I would like to know why you chose such an airfoil since you will have a tail. I see that the Archaeoptryx uses a similar section so there must be a reason.


Other tailed ultralight gliders use sections which have slight undercamber, the ULF 1 uses the Wortmann FX63-137,in post 558 Ypsilon suggested the similar FX60126.
The team at Easy Composites have used a similar qabeck airfoil on their version of the Goat glider.

https://easycomposites.lv/

These airfoils visually have the maximum depth further back along the chord and have a slight undercamber towards the trailing edge, and I presume negative moment coefficients.

Regards
Stewart
 

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ultralajt

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May 9, 2009
Messages
1,575
Location
Slovenia
Mitja

Glad you are back on the project, I have been following it since the start..

Im would like to understand more about the airfoil selection, there seems to be two approaches.

The Kanja airfoil is similar to that of the Impact and Atos flying wing hang gliders, you have a sketch on your website showing the comparison.

These have the maximum depth well forward and I presume have positive pitching moments for use on the flying wings.

I would like to know why you chose such an airfoil since you will have a tail. I see that the Archaeoptryx uses a similar section so there must be a reason.


Other tailed ultralight gliders use sections which have slight undercamber, the ULF 1 uses the Wortmann FX63-137,in post 558 Ypsilon suggested the similar FX60126.
The team at Easy Composites have used a similar qabeck airfoil on their version of the Goat glider.

https://easycomposites.lv/

These airfoils visually have the maximum depth further back along the chord and have a slight undercamber towards the trailing edge, and I presume negative moment coefficients.

Regards
Stewart
Hi Stewart!
On my wing I want the torsion box (D-tube) to be as small as possible in chord, and as high as possible. This is only way that I get light and sturdy D box and spar. If I choose longer D box section (Chord-vise), then a D box shin became thinner. Thin skin is prone to damage caused by handling on the ground (local pressure when handling, some hidden rocks, stones, branches in the grass when assembling the wing..). So, to get narrow and high D box, my airfoil is subjected to this guideline. As I don't aim to super performances, this definitely turbulent airfoil will work just fine.
 
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pictsidhe

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Jul 15, 2014
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8,812
Location
North Carolina
Hi Stewart!
On my wing I want the torsion box (D-tube) to be as small as possible in chord, and as high as possible. This is only way that I get light and sturdy D box and spar. If I choose longer D box section (Chord-vise), then a D box shin became thinner. Thin skin is prone to damage caused by handling on the ground (local pressure when handling, some hidden rocks, stones, branches in the grass when assembling the wing..). So, to get narrow and high D box, my airfoil is subjected to this guideline. As I don't aim to super performances, this definitely turbulent airfoil will work just fine.
That scheme is to minimise weight?
 

ypsilon

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Mar 1, 2016
Messages
305
Location
Austria
Yes. This will hold Weight low.
As always there is an optimum size for the given loads. The torsional stiffness / strength is commensurate with the area of the spar's (D-Box') cross section area. So at some point the cross layer fiber will kill all the advantage you gain from reducing the D-Box depth. It's actually not very hard to calculate the optimum, based on a given set of loads. I am pretty sure Ultralajt, did the maths already :)
 

ultralajt

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Messages
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Slovenia
Something about my airfoil choice.
If we compare my airfoil with FX60-126, it is obviously at once, that FX is not suitable for the foldable wing structure. The rear part is curved strongly both on upper and lower surfaces. My simplified airfoil is pretty straight so flaps and flaperons design will be simple, and Dacron covering also.

As I will use Dacron covering which will never be so defined in terms of correct airfoil contour, using same covering on laminar airfoil will not brings benefits of laminar airfoils... so I am sticking with ordinary laminar airfoil, where all "magic" is done over the D box area of wing.. somethimes even less than complete D box chord...

Regarding airfoil itself at front portion, where a spar and torsion skin is located, my airfoil allow for high spar (hence smaller spar caps cross sections.. leads to lower weight of spar). Also the D box skin will be of lower surface area, so I can make it a bit thicker not exceeding goal mass...

D-box Kanja FL versus FX60-126.jpg

As my glider is not intend to gave great gliding ratio, and will not fly fast, I am sure my airfoil in connection to wing size internal structure design and its loading, is so far my best option.

Using more refined airfoil (such FX 60-126 and so on) could theoretically rise performances a bit, but then I will loose on design simplicity and folding ability, which is here my design goal.
 
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