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Help! How much thrust on my flying wing airplane?

#1
I bought supplies for my first plane, which is the flying wing design! It is carbon fibre and will weigh 403 grams. The tricky part is the motor i bought supplies only 285 grams of thrust. My aircraft will have just over 400mm squared of wing space not including aerons. Will it fly?
 

Tench745

Well-known member
#2
With the information you've given us, the only question we can answer is, "Will an airplane with a 1:1.4 thrust to weight ratio fly?" The answer is "Maybe." There are certainly aircraft that can and do fly this way, but chances are it won't be a ballistic aerobatic aircraft. You'll be flying a wing and you won't have a lot of extra power to fight a draggy airframe to do extreme climb-outs. But, if the aircraft is reasonably slippery through the air, has a good high-lift airfoil, and is flown conservatively it should fly, but maybe only just.
I don't have the experience to give you a better answer than that.
 

Hondo76251

Well-known member
#3
I've found, especially when you start getting smaller, a thrust to weight ratio of at least 1:1 is required for an aircraft to be fun for most to fly. It can be done with less but its seldom as enjoyable. I'm not really into wings. I've built several and I just can't seem to fall in love with them. One thing I've noticed for sure, they seem to do better with a little extra power. I've got a 200 gram foamy that is a blast with only 100 grams of thrust and I've got a 300 gram wing with about 400 grams of thrust that certainly doesn't feel overpowered...
 
#4
What are the particular dimensions and intended cruise speed of your wing, and the exact motors and props you're considering?

I've been working on a design for a 250 gram wing and I think it's the nature of electric propulsion that if you design for efficiency you wind up with tons of excess maximum power.
 

Piotrsko

Well-known member
#6
None of these are good answers , except @BATTLEAXE .
What do any of you do to explain the zero thrust requirement for my slopers?

Motor thrust equates only to acceleration up until thrust equals drag at some airspeed. If the craft can accelerate past the stall point, then thrust is sufficient to fly straight and level, no more no less. Climb requires more thrust than steady state flight, the rate up which is determined by the excess thrust, unless in lift (which can be considered extra thrust).

A typical calculation is motor thrust should be more than flying weight, but that's a really loose guideline.
 

Vimana89

Well-known member
#7
There is no such thing as excess power. It's better to have it and not need it then need it and not have it
Yep. Even a first plane or trainer, if you have poor elevator punch-out, poor low speed performance, or high landing speeds without stalling, it could all be due to not enough power. Those are all things that can make a plane actually fly less gentle, stable, and smooth as well as being less recoverable from mistakes. You definitely want some thrust to spare.
 

BATTLEAXE

Well-known member
#10
None of these are good answers , except @BATTLEAXE .
What do any of you do to explain the zero thrust requirement for my slopers?

Motor thrust equates only to acceleration up until thrust equals drag at some airspeed. If the craft can accelerate past the stall point, then thrust is sufficient to fly straight and level, no more no less. Climb requires more thrust than steady state flight, the rate up which is determined by the excess thrust, unless in lift (which can be considered extra thrust).

A typical calculation is motor thrust should be more than flying weight, but that's a really loose guideline.
The FT education model is based on the beginner, on all their airframes, whether they say this is an intermediate or advanced flyer, still is based on the beginner principles. These principles target keeping the airframe as light as possible, not to much glue, using the lightest possible motor, ESC, and battery requirements just to get it to fly. It gives you a base to start from. Every model is a blank canvas to get you started and you create what your needs are from there. These ideals will keep the plane as light as possible to slow the plane down and keep it slow in maintained flight.

These principles do tend to sacrifice other areas of stable flight, like weather such as wind. Not every flying day is perfect with absolutely still air. So I found that with a little extra weight and power where needed most of these simple designs fly better in various conditions. A flying wing by nature will create as much or if not more drag then a conventional fuselage design, it needs to for stability mostly on the yaw axis. But with the added weight and drag you need to compensate with more power. Jet airliners run a thrust to weight ratio well under 1:1, but then again they aren't beginner RC pilots that fly them, nor are they subject to heavy maneuvers from trying to recover nose dives or dodging obstacles.

Keeping your thrust to weight ration better then 1:1 is so much more beneficial to all skill levels of RC flying. If you cant change your motor then there are other areas to experiment with. Go to a 4 cell from a 3 cell to get more volts and in turn more throttle. Move up a prop size and/or pitch to get more static thrust and more top speed. All this will help close the gap to 1:1, mind you going beyond 1:1 is even better in my opinion. Just like a fighter jet doesn't need to have so much power just to fly and maintain flight, but it sure is nice to have when someone has a missile lock on you.
 

BATTLEAXE

Well-known member
#12
No, but there's such a thing as excess weight.
I have flown an airframe meant for the F pack where I put in a 3536 1200Kv on a 40amp ESC with a 2200 3s spinning a 8x8 and it still flew just fine. Even at over twice the weight of the recommended set up it still flew, and flew better. Even though it wouldn't fly as slow as having the F pack installed, the added power made up for the weight 5 times over. I could get the plane out of any stall situation just by throwing the coals to it. And even on zero throttle, it would still glide nice to a soft landing. Check out my FT-22 vids and you will see.
 

sprzout

Knower of useless information
Mentor
#13
So...I've got a Versa Wing that I fly in combat events. I run a RacerStar Br2830 1300kv motor, with a 30A esc and 2200mAh 35c 3S batteries. I run it with an 8x8 prop in a pusher configuration, and it's pretty quick. It's not the fastest wing out there, but it's got plenty of power to fly up and loop and roll with. I get approx. 1100g of static thrust with it, and it flies nicely.

Based on that, and how I've seen some of the other wings out there fly, I'd say that your 285g of thrust is going to be severely anemic and it won't fly very well - if, that is, it's based on the full size Versa Wing, which I think it might be - the average weight of the Versa Wing is approx. 300g w/o battery.
 

BATTLEAXE

Well-known member
#14
So...I've got a Versa Wing that I fly in combat events. I run a RacerStar Br2830 1300kv motor, with a 30A esc and 2200mAh 35c 3S batteries. I run it with an 8x8 prop in a pusher configuration, and it's pretty quick. It's not the fastest wing out there, but it's got plenty of power to fly up and loop and roll with. I get approx. 1100g of static thrust with it, and it flies nicely.

Based on that, and how I've seen some of the other wings out there fly, I'd say that your 285g of thrust is going to be severely anemic and it won't fly very well - if, that is, it's based on the full size Versa Wing, which I think it might be - the average weight of the Versa Wing is approx. 300g w/o battery.
That's like a 3.5:1 ratio, that's where I like to be as well. People say it is over kill but it is so much fun. Sure you don't need it, but you definitely want it
 

sprzout

Knower of useless information
Mentor
#15
That's like a 3.5:1 ratio, that's where I like to be as well. People say it is over kill but it is so much fun. Sure you don't need it, but you definitely want it
LOL more like 2.5:1 for me, but plenty of thrust for me to scoot around the skies. It doesn't feel as fast as my racing quads, but that's ok for me during combat - I feel like it can get crazy really quick.
 

Hondo76251

Well-known member
#17
Man, I'm lucky if I end up at 1:1 it seems like! A lot of my tinker projects are sub 250 fixed wing fpv, a lot of the weight is camera and battery and frankly, if i can get it in the air and cruise at decent speed it's all good!
 

Hondo76251

Well-known member
#18
But they still DON'T use thrust.
We add weight to fly faster.
Semantics... force=mass x acceleration we all play by the same rules to achieve flight! The energy comes from somewhere, be it motor or wind! I've dabbled in slope soaring, but my other hobby is sailing, harnessing the power of the wind is a most thrilling experience!