The Nova is grounded while I figure out the APM troubles I'm having, see these posts for the details:
http://www.diydrones.com/profiles/blogs/auto-land-testing-and-a-sad-apm?xg_source=activity
In the meantime, I'd like to announce the Raptor! It's going to be a 48 inch wing span flying wing designed after the very successful Ritewing Zephyr. If it performs well it will get an APM as well and be tested alongside the other airframes for efficiency/flight resilience.
Should be a great entry into flying wings and help me consider it as an option for my USA trip airframe. I'll build it, maybe maiden it next week!
-Trent
Comments
Marko - thank you for the detailed information. Good design and good information.
Best Regards,
Bret C
Hi Bret,
I used MH45 for my flying wing, but I cannot remember how I arrived at this choice (I did it about 3 years ago). I suspect I saw someone else using it and followed their lead...
I am using 3 degrees washout - I arrived at this number after simulating the whole airframe XFLR5, and I think this was a good compromise with regards to pitch stability and drag. I was not overly scientific about choosing this particular number, I think I just tried a few numbers, and this just looked about right. I read up a little on how to design flying wings back then, and have forgotten a lot of it since then, so don't think of me as a real expert... That being said, the wing does fly rather nicely.
As for the fuselage: I quickly realized that I needed more space for electronics and the battery, so started building the center section out of plywood and balsa (covered in fiberglass). The profile is actually the same MH45 profile, enlarged by multiplying the thickness of the upper surface with a function that smoothly varies from ~1 at the leading edge to something larger (~1.5?) mid-cord and back to ~1 near the trailing edge. I used something of the form 1 + gauss-profile. There is no theoretical reasoning behind this, I just wanted something thicker in the center that is transition-less on the bottom, roughly looks like a reasonable airfoil and converges to the wing airfoil at leading/trailing edge.
Here is a picture of the mostly-finished center-box:
Marko
Great discussion here guys!
I have a few questions for this group.
1: Which is the best airfoil for a flying wing with about a 56" wing span that needs to haul some weight? MH45 or MH62?
2: I have the Porfili program and see two MH62 airfoils. There is an MH62 & a MH62 9,3%. Which one of these is the best to use?
3: How much washout (negative twist) should a flying wing have with a swept back wing angle similar to a Zephyr II?
4: If I make a flying wing like Marko Kleine Berkenbusch did with an enlarged fuselage area, what airfoil is the fuselage? Is there a general rule of thumb for this type of fuselage?
Thank you guys!
Bret C
very helpful . I'd like to choose MH45
Trent, I did something similar to what you are going to do. I took the planform of a Zypher used a hotwire cutter. Have you thought of putting Spars in? You might want to plan this ahead of time. You might want to consider Carbon rods, or even fliber glass. But if you have a 48" wing out of foam, you will need Spars. You might also want to consider using redundant control surfaces. Kinda like flaps but in this case it will just serve as a failsafe.
Good luck!
Hi Trent
I just crashed my second flying wing today (not beyond repairs). All done in EPS foam which is not perfect but ok for "short-lived projects". Bought a big EPP block which I will create my third generation wings from. I used Zagi10 profile and it flies *really* nice. Only bad thing is that it likes to go into a spin a very low speeds instead of just stall and fall forward. My C/G is probably a bit wrong after all those very hard crashes.
I will create my next EPP wing with the MH45 profile which I've seen works quite well. Well update you as soon as I know how it flies.
/Jesper
Greg: Awesome idea... I think that is what I'll do this week.. We'll see how it goes!
@Andrew, Marko, Greg: Thanks so much guys. Really appreciate your good guidance. I will definitely try this on my next wing build, soon.
While we're at it, there are few other things that i'd like to ask as well regarding flying wings.
1. How do i determine what sweep angle i should use for the two wing halves? What difference does sweep angle make to flight characteristics?
2. How do i decide on a number for the twist in the wing?
3. For the same wing area, what is better...a flyingwing with more span or one with more Chord length (and hence less wing span)?
Finally, is there a good, proper way to set about designing a flying wing? (basically deciding on all the different parameters)?
Thanks for your help
Regards,
Saad
@ Saad,
Adding a twist is easy. You must use a root and a tip template instead of the root and point method. Simply set the tip template a couple of degrees less AOA than the root. You must be very careful to get the left and right wings with the same amount of twist.
@Saad: Andrew's suggestion of twisting the foam stock in the opposite direction before cutting the wing is probably the best solution for producing twist.
I used a slightly different technique: my tip template it twisted against the root template, and I do not use a fixed pivot point for my hotwire, instead I do it by hand on both sides. This is a little tricky, and it took me a good 10 attempts or so to get something reasonably consistent (good thing foam is cheap... ;-) ). If I had to do it again, I would probably follow Andrew's route...
Marko
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