What about a joint-effort design?

[Pij]

There's a bit of discussion around about members designing their own flying wing. Perhaps joining forces might be the way to go. Perhaps if we come up with a design that we (sort of) agree on, a batch of cores could be cut for those interested.

I was about to reply to Sean and Felix in the Who's Flying Where thread, but thought it was worth a thread of its own. So here's my reply:

I've thought about doing one from scratch, before I bought the Duck. But of course it was best for me to get the Duck first. The Duck has some ideas which were along the same lines as I was planning: Good use of washout, blended elevons, somewhat symmetrical airfoil (far from flat bottomed, with reflex starting well forward) etc.

My sketchy plans have a stubbier trailing edge for durability (yes, I know there'll be a drag cost). I was thinking of having the cut core including the elevons, but with 1mm thickness taken off the top and bottom of the rear 50mm to add 1mm balsa skin for rigidity. Hinge-line would be later cut in at 40mm, so there would be balsa skin even in front of the hingeline. I would end up with a fixed trailing edge between the elevons and at the tips, like the Duck, but it would be part of the core, not stuck on.

May 7, 2008 7:56:16 GMT 10 felix said:

hey PIJ,can't argue those points sean made about the duck! although a couple of other points are arguable but like all things any wing is a compromise.i was not aware that the ailerons were really part of the wing on this model......they are on the bee and zagis too but a very half a*rsed part lol.
hey sean you know i'm gunna have to get a duck now and chop it up too to prove you wrong mate.....oh and then i'll show you how to DS ;D.have to get up that way again soon for some more ds pointers i reckon.

May 7, 2008 8:57:46 GMT 10 sean said:

It'd be good to catch up again Felix, just waiting for some decent wind!

Yeah the Duck is unusual in the way the elevons are setup, I think that's part of the reason it flies so nicely.

Have you considered designing a wing from scratch? You've got a lot of good ideas, and that way you can build the planform you're after while maintaining the aerofoil section. There's a few guys around who can cut cores.

[Pij]

Here's a rough idea of what I had in mind. I drew the TE not as stubby as I was first thinking. Also, I made the balsa 60mm on the hinge side, 40mm on the non-hinge side.

[Pij]

Sweep and tip profile:

[ding]

If it was a combat plane you could call it the Joint Strike Fighter

[Pij]

I was thinking the same thing! Then I thought, JSF... Joint Slope Fighter.



Coreflute fin.

[felix]

JSF? so it's gunna go way over budget,be outclassed when it's released and potentially be a dud lol.......sounds pretty good to me ;D
PIJ problem with joint designs unfortunately is one blokes ideal plane and ideas never coincide with the next (look at rc groups etc and you'll see).problem now is there is so many great designs (especially with wings!) out there that half the time you're redesigning the wheel.
sure would be satisfying though so i'll tag along and offer advice where i can for sure mate.

[Pij]

I know for sure that no 2 people would finish it the same way. But it would be a real achievement if we could agree on the cores to be cut, so we could get a small batch done.

Then we could all go and ruin them in our own special way!

So, yes please, give all the advice and ideas you can!

[felix]

ok well my idea would be a low thickness (6% ish) aerofoil with a roundish leading edge,low aspect ratio wing with minimum sweep.also a radiused (?) cutout for the elevon fitment......oh and then angelina jolie to deliver it to my door with a 6pack under her arm ;D
lucky for you i am not greedy lol

[Pij]

May 7, 2008 20:59:05 GMT 10 felix said:

PIJ problem with joint designs unfortunately is one blokes ideal plane and ideas never coincide with the next

OK, point taken. My idea for a joint design was a robust all-rounder. You are after a ... what? High speed DS'er? Lightweight floater?

Maybe we can do 2 designs in parallel, because certainly your needs are far from mine.

A few questions about your concept:

How do you stiffen a wing that has thickness only 6% of a short chord? Oops, you said LOW aspect ratio. OK, 6% of a large chord can have reasonable thickness then, so could be stiffened with spars.

Round leading edge - did you mean in profile or in plan? Perhaps both?

Cutout for elevons I understand, but radiused? Do you mean a rounded recess to fit a rounded LE'd elevon into snugly without the big ugly gap that 45 degree hinge cuts leave? I like that idea. Would need some kind of hinge-pin rather than tape, then.

Are you thinking one central fin?

Yes, I like a low-aspect ratio design too. Do you want to draw up some roughs?

Here's my first impression, if I understood your description properly. It looked eye-catching with even lower aspect ratio, but the name B00by is already taken

[sean]

Looks cool .

I like the high aspect ratio combat wing idea you were discussing in the 'Who's flying where this weekend thread' Felix, could work really well with some custom cut cores and the right aerofoil .

[sean]

Pij, I like the idea of the balsa sheeted TE and elevons. For a bit more crash resistance you could use thin ply (0.4mm). A bit of balsa (say 5mm) on the elevon LE would give the elevon a lot more torsional rigidity.

Not sure about modding the tip aerofoil camber line near the TE, could give unpredictable results. Have you tried an aerofoil analysis program such as Profili? It's very easy to use and good for comparing aerofoils. www.profili2.com

[lucky]

Hi pij, these things can take a lot of time to consider! Many was the time I designed something by some theory only to have an undesirable aspect revealed later.
The short fat elliptical wing and chord of the above glider may offer a degree of instability without a huge vert stabiliser, which could then create other issues but hey, like everything else in life there is more to the dynamics than theory, often some trial and error rules the form and function, which can get expensive.

The Bundy library may have a book called "Model Aircraft Aerodynamics, fourth edition" by Martin Simons. Its a helpful book when considering matching aerofoil sections to wing form and other stuff.

One thing I suspect just now with cutting the above wing form is that it could be very hard for the cutter to do without some kind of washout or washin being built into the wing, or some other kind of section irregularity- unless the cut is a rectangular sheet. Most all epp cuts seem a straighter tapered chord or section to more squarish tips, fror purely practical reasons.
Would the cut be a constant chord/section or tapered, and delivered as a rectangular sheet? if so I guess the builder could then cut out the ellipse wing form. I think it could get a bit tricky to do.

Mate whatever you end up with, and if it flies well and has manners, I will be interested in having one for sure! The epp gliders I like the most are the ones that ordinary fliers invent that are fun, like the Ozprey.

[Pij]

May 8, 2008 8:53:03 GMT 10 sean said:

Pij, I like the idea of the balsa sheeted TE and elevons. For a bit more crash resistance you could use thin ply (0.4mm). A bit of balsa (say 5mm) on the elevon LE would give the elevon a lot more torsional rigidity.

Not sure about modding the tip aerofoil camber line near the TE, could give unpredictable results. Have you tried an aerofoil analysis program such as Profili? It's very easy to use and good for comparing aerofoils. www.profili2.com

Yes, adding the third side of the triangle with balsa sheet would make it nice and rigid. I don't know if much thickness would be needed on that third piece - what about just more 1mm?

I tried importing raster images into Profili to check on this, but I'm a Profili Newbie, so after importing them I couldn't do anything with them. Anyway, the desired effect is decreased stall tendency at a given angle of attack, as compared to the root profile. How would I check that on Profili? Maybe Winfoil, whatever. But Profili seems to have raster import where Winfoil does not.

[Pij]

Lucky,

I see great difficulties with the elliptical planform too. I envisaged a large fin, but what undesirables could that bring in?

Yes, I was reading Model Aircraft Aerodynamics but I had to return it. The chapter on stability was fascinating, but it hurt my brain. And it didn't dwell enough on tail-less designs for my needs.

Making that funny shape with EPP: I have no idea how. I made wings with those kinds of shapes a couple of years ago, for tiny free-flight gliders. There was a brief flurry of FF'ers trying to base a wing on the shape of the Zanonia seed. I always did little tests, weighting and dropping the wings to see their performance alone, before attaching them to the intended fuselage'n'tail. The Zanonia shape makes a viable slow-glider, if you get the CG and wing-loading just right.

My youngest son got me to help him build one with a planform VERY much like the above picture. With a fuse, stab and fin, it made a great catapult glider - performed well in both the high-speed launch and the low-speed glide. (Tried to find the link at SFA forums, but it seems to be archived.) But without a stab hanging out the back - unknown territory for me.

[chamm37]

hi every1........
i have bilt my own flying wing and i am looking to go test it on Saturday it is is all good for the weather.....i was wondering if any1 knows where i can get it cut out of epp foam from like anywhere
i have built it out of a crashed plane that i had laying around out of the wing and have designed it to fly with just the wing. it glides really well with no wind. just throughing it in the backyard off the balkany. Is there going to be any1 down there at SC or woodypoint this saturday.......or is there any1 that could help with some other deisnging and help me make it better ;D ;D

if u would like me to send u some pics of the hammer (that is wat i called it) just pm me and i will be able to send u some via email ;D ;D ;D