martijn10022
New member
Oh I got you wrong then, my English vocabulary in this area is somewhat moderate. This actually is a really good idea, some classic out of the box thinking.
I got so many notes from you guys, this helps alot.
Help! Best wing type for payload
- Thread starter martijn10022
- Start date
I got so many notes from you guys, this helps alot.
martijn10022
New member
Not yet. This week me and my project members will make a final decision for the airplane configuration, then upcoming weeks we will make sketches, CAD drawings and even calculations on the different load cases. I will let you know.
BATTLEAXE
Legendary member
I ask because you said your CG will be somewhere between the tail and the wing, this can't happen. It's the wing itself that decides where your CG is, it has to balance forces between lift and gravity, center of gravity needs to be directly under the center of pressure. Ultimately this is the same spot you want your the center of mass of your payload as well for balanced flight. Correct me if I am wrong but this is all simple aeronautical engineering stuff that I picked up on in these forums and by flying experimental stuff myself, whatever that is worth
Hai-Lee
Old and Bold RC PILOT
Landing Gear:
You could have the fuselage hang well below the wings and thereby fit the main wheel or wheels directly into the underside of the fuselage. This would keep the weight down and the strength up. It could even just have a centreline single wheel as found in some gliders.
CG/balance:
The idea of a lifting tail is not new! The lifting tail does not cause instability with varying airspeed but rather it generates a fixed portion of the total lift. As the speed increases the tail will generate more lift BUT so will the main wing/s. The ratio or percentage of total lift will remain the same. When lightly loaded the tail/elevator will be trimmed to alter the effective tail incidence and hence the main wing incidence as the nose is trimmed downwards. Thereby both the tail and main wing/s produce less lift but in the same proportions.
The CG should actually be considered as the lift balance point. Where it is is determined by the wings and other lifting surfaces. On a Canard which has a lifting tail the balance point is often either at the main wing LE or even between the wing/s and the canard/tail. The lifting canard does not cause the plane to climb automatically with an increase in speed as the lift forces are proportional to the lifting surface areas.
On a standard tractor design the tail is effectively without lift or provides a slightly negative lift component which is used to maintain balance. In such a design a tail heavy setup can be dangerous as the tail is not designed for efficient lift and so is subject to loading for which it is not designed. When the plane slows the "Non-Lifting" tail can stall before the main wing causing a loss of control in pitch followed by a stall and crash.
A lifting tail can be loaded such that the tail stalls last! So the main wings stall first and the plane tends to drop its nose, gain speed, and avoid stall completely.
Just a few thoughts on lifting horizontal tail!
Have fun!
You could have the fuselage hang well below the wings and thereby fit the main wheel or wheels directly into the underside of the fuselage. This would keep the weight down and the strength up. It could even just have a centreline single wheel as found in some gliders.
CG/balance:
The idea of a lifting tail is not new! The lifting tail does not cause instability with varying airspeed but rather it generates a fixed portion of the total lift. As the speed increases the tail will generate more lift BUT so will the main wing/s. The ratio or percentage of total lift will remain the same. When lightly loaded the tail/elevator will be trimmed to alter the effective tail incidence and hence the main wing incidence as the nose is trimmed downwards. Thereby both the tail and main wing/s produce less lift but in the same proportions.
The CG should actually be considered as the lift balance point. Where it is is determined by the wings and other lifting surfaces. On a Canard which has a lifting tail the balance point is often either at the main wing LE or even between the wing/s and the canard/tail. The lifting canard does not cause the plane to climb automatically with an increase in speed as the lift forces are proportional to the lifting surface areas.
On a standard tractor design the tail is effectively without lift or provides a slightly negative lift component which is used to maintain balance. In such a design a tail heavy setup can be dangerous as the tail is not designed for efficient lift and so is subject to loading for which it is not designed. When the plane slows the "Non-Lifting" tail can stall before the main wing causing a loss of control in pitch followed by a stall and crash.
A lifting tail can be loaded such that the tail stalls last! So the main wings stall first and the plane tends to drop its nose, gain speed, and avoid stall completely.
Just a few thoughts on lifting horizontal tail!
Have fun!
Vimana89
Legendary member
Not wider or longer than one meter, and the objective is to carry as heavy a payload as possible. I'm far from an expert, especially with larger planes, but I do know a thing or two about wing loading and lift efficient designs. The best recommendation that others have made so far is a multi wing plane, like a biplane or triplane. An option that could potentially work well that nobody has mentioned(at least that I noticed as I skimmed the thread), is a low aspect, high wing chord design, such as the Nutball (basically a round tailless saucer wing). If you were to use either a tailless circle or tailless square wing, and go just under or exactly one meter by one meter in both chord and span, you'd technically have the lowest wing loading possible, and a ton of lift.With a design like this, you could make the fuselage as minimal as necessary, with a box or compartment just big enough for payload, and then a spar or something reinforcing the rest of the wing.
. I'm far from an expert, especially with larger planes, but I do know a thing or two about wing loading and lift efficient designs. The best recommendation that others have made so far is a multi wing plane, like a biplane or triplane. An option that could potentially work well that nobody has mentioned(at least that I noticed as I skimmed the thread), is a low aspect, high wing chord design, such as the Nutball (basically a round tailless saucer wing). If you were to use either a tailless circle or tailless square wing, and go just under or exactly one meter by one meter in both chord and span, you'd technically have the lowest wing loading possible, and a ton of lift.With a design like this, you could make the fuselage as minimal as necessary, with a box or compartment just big enough for payload, and then a spar or something reinforcing the rest of the wing.
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martijn10022
New member
Single components may not exceed 1 m, thats due to the limited storage space. Together they may exceed this.Not wider or longer than one meter, and the objective is to carry as heavy a payload as possible
1 meter chord? Wouldn't that stall really quick? And the moment of inertia would be huge so I would need large operating surfaces, but I don't know if the electronics can handle that. Am I right?
But you're right, I should design the fuse based on the payload strips! Thank you
martijn10022
New member
Your explanation makes a lot of sense and you're right. So I will have to calculate or measure the ratio of lift between the main and tail wings, in manner of speaking.I ask because you said your CG will be somewhere between the tail and the wing, this can't happen. It's the wing itself that decides where your CG is, it has to balance forces between lift and gravity, center of gravity needs to be directly under the center of pressure. Ultimately this is the same spot you want your the center of mass of your payload as well for balanced flight. Correct me if I am wrong but this is all simple aeronautical engineering stuff that I picked up on in these forums and by flying experimental stuff myself, whatever that is worth
It's just that this can't be tested until in a few weeks. (Is that correct English)
BATTLEAXE
Legendary member
It's close enough English
Since you can't test it for yourself it would be a good idea to go with what you know works already. If lifting tail surfaces are unfamiliar territory then I would skip that and go with a simple design. I would, and only if I was you, and this is just my opinion, is a biplane design give a few rules of wing dynamics, prop in the front, balance with an extended tail that only stabilizes the pitch and yaw axis, no lifting. The wings will be your 1 meter on the diagonal in wingspan, with a 200mm wing chord, flat bottom with a 30mm maximum total height of the cross section of the wing, the last 100mm of each wing tip is under cambered. Two wings built like this which will be removable from the fuse from the top and bottom of the fuse in a biplane configuration spaced 160mm apart from the top of the bottom wing to the bottom of the top wing. The CG should sit somewhere between 50-65mm from the leading edge, which is where the spar will be located in the wing. The horizontal stabilizer should be 250mm in span and the vertical stabilizer at 125mm in height. The fuse length should be kept inside the 1 meter diagonal length with the tail feathers, motor and prop attached, in doing rough head math will have roughly a total length of 800-850mm.
Does this sound about right to you?
Vimana89
Legendary member
This sounds reasonable for a big plane. To answer @martijn10022 's question, square and round planes with equal span and chord do tend to work better in smaller sizes mainly due to ease of construction, though giant square planes and Nutballs have been made and flown successfully. As far as stalling out, these planes are actually quite resistant to stalls and have gentle stall behavior if you get the CG and whatnot right. All these observations are from hands on experience withy smaller models, so I'm not entirely sure how everything scales up, I just know some pretty big low aspect planes have been built and flown.It's close enough English
The wings will be your 1 meter on the diagonal in wingspan, with a 200mm wing chord, flat bottom with a 30mm maximum total height of the cross section of the wing, the last 100mm of each wing tip is under cambered. Two wings built like this which will be removable from the fuse from the top and bottom of the fuse in a biplane configuration spaced 160mm apart from the top of the bottom wing to the bottom of the top wing. The CG should sit somewhere between 50-65mm from the leading edge, which is where the spar will be located in the wing. The horizontal stabilizer should be 250mm in span and the vertical stabilizer at 125mm in height. The fuse length should be kept inside the 1 meter diagonal length with the tail feathers, motor and prop attached, in doing rough head math will have roughly a total length of 800-850mm.
Does this sound about right to you?
martijn10022
New member
Even more reasons to use a lifting tail.
I think I get it now. You're right. So I will calculate this ratio, then use it to optimise CG.
Thanks!
martijn10022
New member
Alright I will keep him in mind. Thanks
martijn10022
New member
Well the competition day is in 15 weeks or so. So since I got the time, I will definitely look into a lifting tail, but a biplane also works. I will discuss this with my projectgroup on thursday.It's close enough English
The wings will be your 1 meter on the diagonal in wingspan, with a 200mm wing chord, flat bottom with a 30mm maximum total height of the cross section of the wing, the last 100mm of each wing tip is under cambered. Two wings built like this which will be removable from the fuse from the top and bottom of the fuse in a biplane configuration spaced 160mm apart from the top of the bottom wing to the bottom of the top wing. The CG should sit somewhere between 50-65mm from the leading edge, which is where the spar will be located in the wing. The horizontal stabilizer should be 250mm in span and the vertical stabilizer at 125mm in height. The fuse length should be kept inside the 1 meter diagonal length with the tail feathers, motor and prop attached, in doing rough head math will have roughly a total length of 800-850mm.
Does this sound about right to you?
This blueprint is alot of information, have you built this? It looks good, I will look into this tomorrow since it is almost midnight here in the Netherlands.
And do you think that a biplane will meet the highest payload rule more than a lifting tail?
Hai-Lee
Old and Bold RC PILOT
Any flying wing or tailless design by its very nature cannot be considered as capable of high lift. Sure you can have large wing area but the fitting of flaps and other high lift devices is normally outside of the design. The control surfaces actually provide NEGATIVE lift to allow the wing to balance its lift and remain stable.
For the same wing area a conventional plane with flaps will always have higher lifting capacity and the ability to actually be a STOL design.
The ratios given by some for tail Vs wing area and overall fuselage length are just basic guides or conventions for aircraft and many aircraft have flown successfully with ratios well outside of the oft quoted ratios.
Another aspect to the design of a wing is the thickness to cord ratio. A thin cord wing will not provide as much lift as a thicker cord wing of the same cord length. On undercambered wings the same applies but here the cord is measured as the distance between the LE and TE in a straight line. A thicker wing does produce more drag and flies slower but the lift is directly related to the difference in the path travelled by the air over the wing Vs the path travelled by the air under the wing.
If the contest storage size permits I would have gone with 5, (1 metre), wings. The first 4 setup as a pair of biplane wings, (with a dihedral joint for each pair), and the remaining wing section configured as the horizontal tail unit. The wings would have flaps as a matter of course and the wing struts would provide the lift fence function.
The fuselage would either have a deep cross-section around the wing mounting area or the upper wings would be secured using a pylon mount. Due to the large wing area the vertical stab would be effectively a fin or spine increasing in height as it got closer to the rudder. The Horizontal tail would be best mounted atop the vertical fin if structurally possible.
Starting incidence angles would be zero for the bottom wing and around 1 to 2 degrees for the top wing and the horizontal tail.
The largest diameter SF prop that can be used would be best as this would provide a degree of static lift at full throttle, (especially if flaps were deployed).
According to the "Contest" rules it appears that the competition is one of aircraft to payload capacity and so it is effectively not only a matter of plane design as in chosen type/layout but also one of structural strength Vs weight. Whatever you finally decide to proceed with you will need it to be light and strong. With the use of guy wires on a biplane design the loads can be better distributed on a lightweight design with a small weight penalty.
Guy wires could even be braided fishing line.
Just a few thoughts!
Have fun!
For the same wing area a conventional plane with flaps will always have higher lifting capacity and the ability to actually be a STOL design.
The ratios given by some for tail Vs wing area and overall fuselage length are just basic guides or conventions for aircraft and many aircraft have flown successfully with ratios well outside of the oft quoted ratios.
Another aspect to the design of a wing is the thickness to cord ratio. A thin cord wing will not provide as much lift as a thicker cord wing of the same cord length. On undercambered wings the same applies but here the cord is measured as the distance between the LE and TE in a straight line. A thicker wing does produce more drag and flies slower but the lift is directly related to the difference in the path travelled by the air over the wing Vs the path travelled by the air under the wing.
If the contest storage size permits I would have gone with 5, (1 metre), wings. The first 4 setup as a pair of biplane wings, (with a dihedral joint for each pair), and the remaining wing section configured as the horizontal tail unit. The wings would have flaps as a matter of course and the wing struts would provide the lift fence function.
The fuselage would either have a deep cross-section around the wing mounting area or the upper wings would be secured using a pylon mount. Due to the large wing area the vertical stab would be effectively a fin or spine increasing in height as it got closer to the rudder. The Horizontal tail would be best mounted atop the vertical fin if structurally possible.
Starting incidence angles would be zero for the bottom wing and around 1 to 2 degrees for the top wing and the horizontal tail.
The largest diameter SF prop that can be used would be best as this would provide a degree of static lift at full throttle, (especially if flaps were deployed).
According to the "Contest" rules it appears that the competition is one of aircraft to payload capacity and so it is effectively not only a matter of plane design as in chosen type/layout but also one of structural strength Vs weight. Whatever you finally decide to proceed with you will need it to be light and strong. With the use of guy wires on a biplane design the loads can be better distributed on a lightweight design with a small weight penalty.
Guy wires could even be braided fishing line.
Just a few thoughts!
Have fun!
martijn10022
New member
Okay, I had never heard about Nutballs. I will look into this!
A problem will be the width and length since components may not exceed 0.30*0.35*1.00 in meters. Such a big wing would exceed 35 cm (14 inch) wouldn't it?
BATTLEAXE
Legendary member
You said you weren't able to test it for a couple of weeks so I assumed that's when you receive the electronics. Since you still have another couple months after that to test before the competition then you will have time to test a bunch of designs, which was the unknown. That's why I said to use something that is well proven.
That being said you could build downscale versions of different designs that are un-powered chuck gliders to figure out balance and stall characteristic's of each suggested design. In this you will be able to figure out what works best for you and your group within the parameters of the competition.
And yea I have built many of these in different variations of these wing design principles and parameters given that FliteTest uses these same base principles on many of their designs. I have done mono wing, high, mid and low mount, biplanes, flying wings and canard designs. All except the lifting tail, that's where i don't know enough about it on an experience standpoint.
You still have lots of time to figure it out, and be sure that the first one out of the gate won't be optimal, with any design there will be experimental tweak's and variables to explore. I would say given the advice you have gotten from any of us gives you have a step up advantage over any of the other competitors, Be sure to post what you guys come up with. I am definitely curious as to what you choose to do and the results of your testing, then of course how it works out in the competition. Good luck and have fun
Vimana89
Legendary member
Great post, this clarifies things a lot for me, and hopefully the OP as well...That's why I said, take my experience with high chord, low aspect designs with a grain of salt, because I'm not sure how they scale up, and I had a feeling that low wing loading and big wing area wasn't necessarily the only things to translate to a good heavy lifting design. I have built a tailed version of the Nutball, but the addition of the tail might not mitigate all those drawbacks. That being said, a more conventional design with a higher wing chord would work well, definitely no skinny chord wings for this one. I especially like the idea of a biplane, but a monoplane would be fine too if designed and purpose built for the job. I'm not the guy to ask about setting up flaps, but there are many people who use them all the time.
