Good High aspect UAV airfoils?

[Psionic001]

Can anyone recommend any good airfoils for high aspect UAVs?

Something pretty lifty, does not have to fly too fast, has a small amount of sweep, aspect about 1/10,

thanx

Matt

[GeeW]

Really need a bit more info to advise you.
Chord, projected cruise speed, projected cruise altitude or max likely altitude. Which will put us in the right ballpark Reynolds number wise.....

If we are talking typical 2 to 3m span on a 0.25m chord with moderate RC wing loading circa 50gms/sqdm then S3021 or Clark Y thinned to say 10% work surprisingly well and are both nice and docile at the stall. Both become less good if you lower the Cl too much <0.3 ish.
Recommend you take a look at Profili (free d/load) so you can then play about with numbers and airfoils.

[Psionic001]

Hi,

Here are some numbers. I do have profili but I'm unsure how to use it.

These numbers are approximate based on my initial rough plan view:

4 meter span
26cm Chord at the tip
33cm chord at the root
12cm sweep back
Cruise speed 40-60 km/h
Max speed 120 km/h

Thanks

[ThermalSeeker]

What method of building are you going to use ?

If you're going to use a built up balsa technique then you should strongly consider a flat bottomed airfoil. If it's not flat bottomed then you'll have to create a way to shim each rib individually as you build. Otherwise you can end up with a twist in your wing. A flat bottomed airfoil will eliminate that problem. The ClarkY that GeeW mentioned above is a flat bottomed airfoil.
Also with a wood spar and 4 Meters of span you're going to need a thick airfoil to keep the wing strong enough. It can ruin your day to pull on the elevator and see the wing fold. Again the Clark Y is almost 12% thick...thicker than most. It also has a lot of camber which will give you a slower stall speed, better climb and load carrying capability, and it's forgiving of less than accurate building. Just don't expect it to compete with present day airfoils on speed range, or efficiency.

Building with foam, fiberglass, and carbon fiber can change all of the above and allow you more choices.


Good Luck,
Mike


Hi,

Here are some numbers. I do have profili but I'm unsure how to use it.

These numbers are approximate based on my initial rough plan view:

4 meter span
26cm Chord at the tip
33cm chord at the root
12cm sweep back
Cruise speed 40-60 km/h
Max speed 120 km/h

Thanks

[Psionic001]

Hi,

I will be making the wing from composite materials with an eps or epp core.
The spar will be a combination of braided and unidirectional carbon fibre.

At the moment the Naca 4415 is the front runner that I have. Can anyone confirm whether this has been successful for them?

thanks

Matt



What method of building are you going to use ?

If you're going to use a built up balsa technique then you should strongly consider a flat bottomed airfoil. If it's not flat bottomed then you'll have to create a way to shim each rib individually as you build. Otherwise you can end up with a twist in your wing. A flat bottomed airfoil will eliminate that problem. The ClarkY that GeeW mentioned above is a flat bottomed airfoil.
Also with a wood spar and 4 Meters of span you're going to need a thick airfoil to keep the wing strong enough. It can ruin your day to pull on the elevator and see the wing fold. Again the Clark Y is almost 12% thick...thicker than most. It also has a lot of camber which will give you a slower stall speed, better climb and load carrying capability, and it's forgiving of less than accurate building. Just don't expect it to compete with present day airfoils on speed range, or efficiency.

Building with foam, fiberglass, and carbon fiber can change all of the above and allow you more choices.


Good Luck,
Mike

[ThermalSeeker]

A 4415 is 15% thick with 4% camber. That's like flying around with flaps deflected all the time. That's fine if you want to fly slow with lot's of power but you're not going to have much speed range. There will be slow and climb or slow and descend. The only models that I know of that use an airfoil that thick currently are control line stunt models. They want to go slow and up and then slow when coming down. If that's what you're after great.

Mike

Hi,

I will be making the wing from composite materials with an eps or epp core.
The spar will be a combination of braided and unidirectional carbon fibre.

At the moment the Naca 4415 is the front runner that I have. Can anyone confirm whether this has been successful for them?

thanks

Matt

[Psionic001]

OK, thanks...

Should I look at thinning the 4415 to say 12% or do you think Clarke Y @12% would still be better on a composite wing?



A 4415 is 15% thick with 4% camber. That's like flying around with flaps deflected all the time. That's fine if you want to fly slow with lot's of power but you're not going to have much speed range. There will be slow and climb or slow and descend. The only models that I know of that use an airfoil that thick currently are control line stunt models. They want to go slow and up and then slow when coming down. If that's what you're after great.

Mike

[GeeW]

Psionic001
Perhaps the way forwards is to look at it from the other end....
What weight of payload do you require??

With the wing dimensions you have quoted it is certainly going to be a motor glider. Glider wings, although high in efficiency are not great load carriers....to get the strength they get very heavy. A lower aspect ratio wing will be significantly lighter.
re airfoil...I would probably go with the S7055 as it more efficient than the Clark Y and still has a flat bottom.
See http://www.gliders.dk/s_7055.htm

Gordon

[Psionic001]

Thanks Gordon et al, I'm learning as I go and appreciate the feedback...

I'd like to be able to carry a payload of up to about 8kg. Would that be an unusually large payload for a 4 meter UAV?

I guess I need a good hybrid between high efficiency and reasonable load capacity.
Endurance is slightly more important to me at this stage, so if I need to carry a greater load, I'll make a bigger plane.

I won't be flying any higher than 1500' (3000' AMSL)

Thanks for the link, I'll check it out.

regards

Matt


Psionic001
Perhaps the way forwards is to look at it from the other end....
What weight of payload do you require??

With the wing dimensions you have quoted it is certainly going to be a motor glider. Glider wings, although high in efficiency are not great load carriers....to get the strength they get very heavy. A lower aspect ratio wing will be significantly lighter.
re airfoil...I would probably go with the S7055 as it more efficient than the Clark Y and still has a flat bottom.
See http://www.gliders.dk/s_7055.htm

Gordon

[Mick Molloy]

Thanks Gordon et al, I'm learning as I go and appreciate the feedback...

I'd like to be able to carry a payload of up to about 8kg. Would that be an unusually large payload for a 4 meter UAV?

I guess I need a good hybrid between high efficiency and reasonable load capacity.
Endurance is slightly more important to me at this stage, so if I need to carry a greater load, I'll make a bigger plane.

I won't be flying any higher than 1500' (3000' AMSL)

Thanks for the link, I'll check it out.

regards

Matt

Matt when you say payload of 8kg, what total airframe + payload weight are you expecting?

[Psionic001]

Hi Mick,

Well I'm not limited to my 150kg limit now if you catch my drift.... :(

I'm not sure how heavy the UAV will be actually, probably about 8-10kg fueled, but that would just be guessing.

Am I asking too much of an airframe with a 4m span and a slightly tapered wing?

best

Matt

Matt when you say payload of 8kg, what total airframe + payload weight are you expecting?

[Mick Molloy]

Hi Mick,

Well I'm not limited to my 150kg limit now if you catch my drift.... :(

I'm not sure how heavy the UAV will be actually, probably about 8-10kg fueled, but that would just be guessing.

Am I asking too much of an airframe with a 4m span and a slightly tapered wing?

best

Matt

It’s a terminology thing you were saying 8kg payload when you meant 8kg Gross Weight

PAYLOAD - Anything that an aircraft carries beyond what is required for its operation during flight, theoretically that from which revenue is derived, such as cargo and passengers.

GROSS WEIGHT - The total weight of an aircraft when fully loaded, including fuel, cargo, and passengers; aka Takeoff Weight.

Hope this helps

Mick

[airmcn_3]

Hi Mick,

Well I'm not limited to my 150kg limit now if you catch my drift.... :(

I'm not sure how heavy the UAV will be actually, probably about 8-10kg fueled, but that would just be guessing.

Am I asking too much of an airframe with a 4m span and a slightly tapered wing?

best

Matt


Matt,

That is a rather hard one. We really need to know what your projected total aircraft weight is.

If you want to hear the basic answer to you question, don’t go over 18kg on a 4m wing. If you are going glider style with a higher AR then don’t go over 10kg on a 4m wing or you will find out the hard way....... Hell, a peice of plywood 4m with a 12" chord will fly 8kg at 40mph...... Good luck.

[Psionic001]

Hi Mick,

yes, I knew that :)

The UAV will be 8-10kg and I would like to achieve a payload of up to 8kg.

The minimum payload will be FPV cam (weighs nothing), gyrostabilised gimbal cam (2kg), then the excess will be for anything else we need, whether it's more hardware, more fuel, or things we need to drop.

Achieveable???

thanks

Matt


It’s a terminology thing you were saying 8kg payload when you meant 8kg Gross Weight

PAYLOAD - Anything that an aircraft carries beyond what is required for its operation during flight, theoretically that from which revenue is derived, such as cargo and passengers.

GROSS WEIGHT - The total weight of an aircraft when fully loaded, including fuel, cargo, and passengers; aka Takeoff Weight.

Hope this helps

Mick

[Psionic001]

OK,

so I need to steer away from a glider wing and go for a constant cord wing, thick and robust. So as per my previous post, a projected Ramp Weight max of 18kg is what I need a wing for.

Matt



Matt,

That is a rather hard one. We really need to know what your projected total aircraft weight is.

If you want to hear the basic answer to you question, don’t go over 28kg on a 4m wing. If you are going glider style with a higher AR then don’t go over 10kg on a 4m wing or you will find out the hard way....... Hell, a peice of plywood 4m with a 12" chord will fly 8kg at 40mph...... Good luck.

[airmcn_3]

Achieveable???

thanks

Matt



Absolutely, although I think in order for you to build a 2kg airframe that will carry an 8kg payload you will find it will be rather hard to achieve......

Chris

[Psionic001]

Hmmmm,

missing my point. Probably me that's not being clear.

The MTOW I am aiming for would be 18kg.
That is 8-10 kg for the fueled UAV, PLUS capacity to carry a further 8kg payload.

Heh, I can't build a 2kg airframe. :) Further.... The Zenoah twin weighs 3.6kg by itself!!!


Absolutely, although I think in order for you to build a 2kg airframe that will carry an 8kg payload you will find it will be rather hard to achieve......

Chris

[GeeW]

Psionic
I think that a read of Andy Lennons 'Basics of model aircraft design' would help you enormously in your design. It is (I think) the best starter book for model design there is....it will also help you understand how good profili is!
If you want to delve deeper then Martin Simons book is better and is now one of the standard works of reference for commercial UAV/drone designers (my nephew had me source a copy for him as that's his trade)

Gordon

[Psionic001]

Thanks Gordon,

I was exploring my Pro Version of Profili last night. I don't know how to interpret Polars, so I will read up on them.

I modeled the Selig 7055 into my design and it looks similar to a Clark-Y.

best

Matt

Psionic
I think that a read of Andy Lennons 'Basics of model aircraft design' would help you enormously in your design. It is (I think) the best starter book for model design there is....it will also help you understand how good profili is!
If you want to delve deeper then Martin Simons book is better and is now one of the standard works of reference for commercial UAV/drone designers (my nephew had me source a copy for him as that's his trade)

Gordon

[keithskye]

Psionic001
Perhaps the way forwards is to look at it from the other end....
What weight of payload do you require??

With the wing dimensions you have quoted it is certainly going to be a motor glider. Glider wings, although high in efficiency are not great load carriers....to get the strength they get very heavy. A lower aspect ratio wing will be significantly lighter.
re airfoil...I would probably go with the S7055 as it more efficient than the Clark Y and still has a flat bottom.
See http://www.gliders.dk/s_7055.htm

Gordon

Gordon,

Just wondering what you mean by the statement "glider wings are not great load carriers"? And you also say that they get very heavy if you go for strength. I'm not an aeronautical engineer specializing in aerodynamics, but I do have a very basic knowledge and a fair amount of experience with things that fly, both models and full scale, and I must disagree with you, at least with respect to wings at this span. The wings on my all-hollow-molded gliders are not heavy at all, in my opinion. I do not know what you fly, but I fly F3J, F3B and F3F gliders, including RES designs, and I also DS many of those models. When DS'ing, we are putting loads of several hundred pounds on the wings in some cases and well into the 10's of G being pulled as we fly, with G spikes going off the scale. And these wings are very light considering their strength and size. Also, with 4 to 6 servo wing and full span camber changing capability, the handling characteristics are superb, going very fast or very slow! The same model with a 3.4m wingspan that I just flew at over 200mph (over 300kph) and pulling in excess of 20 G will then slow up enough to land in my hand after deploying flap and/or crow braking. There are successful UAVs out there flying with just such wings (look at the Aerosonde for instance). The quality and efficiency of most hollow-molded composite wings on such gliders are fantastic. The variety of airfoil sections used provide, in my very humble opinion, as wide a performance range as you can get in wings of this size range. After all, they are optimized for high lift, low drag thermal soaring, with the ability to change camber to suit conditions and to allow high speed flight to cover a lot ground between thermals or to simply go very fast without giving up much altitude. If you want to carry more payload, build such a wing and just increase the chord a bit for greater surface area. Look at the Selig airfoils, or the MH series or the HN series. To make effective use of them, though, you will have to have flap and aileron capability. The FX series of airfoils are also good, but work best at very high aspect ratios (see all the large scale glider models). The other advantage of hollow molded wings is the space you have inside to mount gear in (video transmitters, receivers, batteries, etc.), and if you know exactly what equipment you are installing in your model, you can actually mount a lot of things inside during the molding process, or mold in "equipment bays" for later installation of your hardware.

Now, having said all that, the total AUW that Matt wants to achieve with a 4m wingspan is ambitious, and at the very least is going to require more chord to increase wing area in order to get the wing loading down to something that is manageable. And a thicker section with a bit of camber will help with the lift, but you give up something in drag of course. Also, the wing planform plays a big role, as well as the configuration of the whole airframe, as total surface loading (and that can include the fuselage as a lifting surface) is a factor, not just wing loading.

Matt, I find your project very, very interesting, because I am already building a UAV with a 4m wing and we are going for the widest speed range possible, as well as lofting almost the same exact payload that you are shooting for, and that is only our proof of concept machine. The end product will be much larger and the payload will be much, much heavier and take up a fair amount of space as well. We hope to do first flight test of the airframe configuration proof of concept soon (within 60 days). Good luck with your project. I'd love to hear more about what you are trying to do (privately, of course). It's possible we may be able to join forces to accomplish our goals, if we happen to be on the same track more or less!

Keith

[GeeW]

Keith
Sorry :o , by "loaded" I was refering to wingloading (at 1g) and not (accelleration) loads. Your second paragraph goes where I'm coming from. A high wing loading on a (typical) sailplane wing is not normally a nice device to fly at near stall airspeeds without the addition of more compexity of design....
To be able to fully appreciate your airfoil suggestions (which I concur) I believe that Psionic may like to do a bit more reading on the subject. I am in no way demeaning Psionic here as I am only guessing his knowledgebase, aerodynamics is a huge and at times a pretty bewildering subject. :D

Now back to the scheduled program...........

Gordon :)

[Psionic001]

Correct, I'm just learning and have no formal training in aerodynamics, other than doing my CPL.

So you may have to bear with me while I get up to speed...

Keith
Sorry :o , by "loaded" I was refering to wingloading (at 1g) and not (accelleration) loads. Your second paragraph goes where I'm coming from. A high wing loading on a (typical) sailplane wing is not normally a nice device to fly at near stall airspeeds without the addition of more compexity of design....
To be able to fully appreciate your airfoil suggestions (which I concur) I believe that Psionic may like to do a bit more reading on the subject. I am in no way demeaning Psionic here as I am only guessing his knowledgebase, aerodynamics is a huge and at times a pretty bewildering subject. :D

Now back to the scheduled program...........

Gordon :)

[keithskye]

Keith
Sorry :o , by "loaded" I was refering to wingloading (at 1g) and not (accelleration) loads. Your second paragraph goes where I'm coming from. A high wing loading on a (typical) sailplane wing is not normally a nice device to fly at near stall airspeeds without the addition of more compexity of design....
To be able to fully appreciate your airfoil suggestions (which I concur) I believe that Psionic may like to do a bit more reading on the subject. I am in no way demeaning Psionic here as I am only guessing his knowledgebase, aerodynamics is a huge and at times a pretty bewildering subject. :D

Now back to the scheduled program...........

Gordon :)


Gordon,

I kind of thought that's what you meant, but wasn't sure. Hope I didn't sound too strident there in my post! :) It was 3am local time when I wrote it! You are so very correct about the poor handling/stall characteristics of a highly loaded wing, especially in the case of a high aspect glider wing. They take a long time to get back up to speed before they are flying again, and with the inertia of such a long wing, it takes a fair bit of time and a lot of altitude to recover from any unusual attitude that may occur in the stall, as I'm sure you are very well aware of.

Matt,

Great to see you working on your CPL! I have been a professional pilot for over 25 years now, and currently I am chief pilot and senior Captain for a private flight department based in the UK. I fly Challengers and Gulfstreams. I remember working on my CPL back in 1982. I actually got my CPL and my Instrument Rating all in the same check ride, in a Piper Arrow IV. What a workout that was, especially as it was nearly 40 deg C and quite windy that day. I was very green around the gills by the time I landed, but it felt great to have both ratings at the same time!

With regard to understanding aerodynamics, what you learn in achieving your PPL, CPL and even your ATPL is just enough to get the job done, as they say. If you really want to have a better understanding, then you must do some additional reading and study. I have read many texts on the subject, and it never ceases to fascinate me. Most commercial pilots do not have the in-depth understanding of aerodynamics necessary to really understand performance in the way an aeronautical engineer would. I am always amazed by how much my fellow pilots do NOT know! As a consultant in my off time, I teach other pilots in private flight departments about better operating practices and flying techniques to improve the way they fly their aircraft in order to increase efficiency and thus be more cost effective. One of the fringe benefits is that I am also able to increase their level of safety because they have a better understanding of what their aircraft can do and why, and it gives them more options than they ever learn in even the best of simulator training environments. The bottom line here is that the more you study and learn on your own, outside of the required material to get your licenses, the better, and SAFER a pilot you'll be.

Good luck in your ambitions and aviation pursuits!

Keith

[Psionic001]

Heh,

when I said "other than doing my CPL" the doing part was past tense. I completed my CPL in 1989 but never followed a professional career in Aviation.

best

Matt

Gordon,

I kind of thought that's what you meant, but wasn't sure. Hope I didn't sound too strident there in my post! :) It was 3am local time when I wrote it! You are so very correct about the poor handling/stall characteristics of a highly loaded wing, especially in the case of a high aspect glider wing. They take a long time to get back up to speed before they are flying again, and with the inertia of such a long wing, it takes a fair bit of time and a lot of altitude to recover from any unusual attitude that may occur in the stall, as I'm sure you are very well aware of.

Matt,

Great to see you working on your CPL! I have been a professional pilot for over 25 years now, and currently I am chief pilot and senior Captain for a private flight department based in the UK. I fly Challengers and Gulfstreams. I remember working on my CPL back in 1982. I actually got my CPL and my Instrument Rating all in the same check ride, in a Piper Arrow IV. What a workout that was, especially as it was nearly 40 deg C and quite windy that day. I was very green around the gills by the time I landed, but it felt great to have both ratings at the same time!

With regard to understanding aerodynamics, what you learn in achieving your PPL, CPL and even your ATPL is just enough to get the job done, as they say. If you really want to have a better understanding, then you must do some additional reading and study. I have read many texts on the subject, and it never ceases to fascinate me. Most commercial pilots do not have the in-depth understanding of aerodynamics necessary to really understand performance in the way an aeronautical engineer would. I am always amazed by how much my fellow pilots do NOT know! As a consultant in my off time, I teach other pilots in private flight departments about better operating practices and flying techniques to improve the way they fly their aircraft in order to increase efficiency and thus be more cost effective. One of the fringe benefits is that I am also able to increase their level of safety because they have a better understanding of what their aircraft can do and why, and it gives them more options than they ever learn in even the best of simulator training environments. The bottom line here is that the more you study and learn on your own, outside of the required material to get your licenses, the better, and SAFER a pilot you'll be.

Good luck in your ambitions and aviation pursuits!

Keith

[aitor_ol]

Dear guys,

Very interesting your comments, I add mine here.

If you are interested in an high CL capable and slightly thick airfoil take a look at Txx3017: http://personal.telefonica.terra.es/web/jatm/airfoil_data/Txx3017/Txx3017_e.html


On my approach to UAV instead, i would prefer a low drag airfoil, say AG25, to maximize the range of the ship.

best regards and good look,

aitor

[nmasters]

Thanks Gordon,

I was exploring my Pro Version of Profili last night. I don't know how to interpret Polars, so I will read up on them.

You can get "Understanding Polars Without Math" from B² Streamlines (http://www.b2streamlines.com/books/booktitles.html)

--Norm