Hey guys !
I was designing an aircraft in XFLR. I'll be putting up some sensors on this along with a gopro and will be using it for 3d mapping.
So while designing I came across this Lift distribution, I've never seen anything like this before ? Can some explain what exactly is happening near the wing tips ?
Replies
The reason why the lift line starts going behind the wing is because there is a non-zero moment from that airfoil but lift is approaching zero. To accurately express the moment caused by the very small lift, they have to place the lift far behind the wing. This is to be expected.
looks like classic wing tip lift loss and vortex generation to me. the ideal lift distribution would be elliptical, but i would not worry too much about it if i were you. concentrate on efficiency robbing effects that you can easily do something about first, then worry about refining your wing design later. like where will the prop be placed? and will it's accelerated airflow hit the fuselage, tail, etc? and flight dynamics too. these are more key to the success of the prototype. this is my project for that purpose, if it gives you any ideas.
https://www.youtube.com/watch?v=R8hpn7SDRpQ
Hey Spike,
I loved that video,
Do you have a build log or something of that sort for that plane ?
Mad crafting skills mate. I'd love to learn a few of those :D
Thanks for the comment. Also check out a few CAD designs of my initial prototype.
your airframe is very similar in many ways to mine. i have found some great benefits switching to 2 engines. no torque effect on power up, and easy to trim for any power setting, an it helped immensely to get the tail higher for rock solid spiral stability/tracking in a straight line. i would like to see a twin engine version of your design. what airfoil are you using? i'm looking for a good airfoil for long duration flight optimization for my version 2 of gemini.thanks for the interest in gemini.
Yeah two motors are always better, specially in push prop, because of suction effect the airflow is more uniform over the wing and prop wash is away from the tail. Ideally the best would be small propellers all over the wing but that isn't feasible in real life.
The airfoil I'm planning to use is a custom I made in profili, high lift, mild stall airfoil. It was made after over 200 iterations with different airfoils. Also the power factor and Cl/Cd are great. But I plan to use a combination of airfoils over the whole wing based on the reynolds number over that section and then optimize that part of the wing for that range of reynolds number.
What are your thoughts regarding this ?
looks like a great airfoil at a glance. do you have l/d for it, and optimum angle for l/d? I would be interested in a graph plot for the airfoil, if you don't mind me using /testing it. thanks.
use the carbon fiber sparingly on most of the wing. i like thin strips at the top, and bottom of the wing, one set fwd, and one set a bit aft, so there are essentially two spars. there must be some webbing, or other support for them to keep them from bulking. to make the wing portable, a tube is the best, as it provides strength i all directions, so that the wings don't fold back. and then there must be a good way to hold the wing sections together. as far as the tube, it should be as short as possible to reduce weight, but long enough to transfer the load to the strips. one large tube would prob. be best, if it can take the load. and the strips can be pretty thin. i used 1.5 mm by 5 mm by 1000mm strips on gemini. 4 per wing section.
That was really helpful Spike. Thanks for the help.
I have a few doubts though, shouldn't the tube length be equal to the wing span ?
And also what exactly do you mean by webbing ? And whats exactly do you mean by
4 strips at the top and bottom, won't it disturb the foil shape ?
the strength of the tube is for the joint only. after that, the load should be transferred to the carbon fiber strips. they weigh a lot less than the tube. a tube that long would be really heavy.
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