joe_weisman

Just in case there's somebody here who doesn't prowl around spadworld too, I'm re-posting a set of plans that I made for a SPAD CoroZag flying wing. It uses an OS .25LA engine.

I've built the plane twice, and although I have no previous experience with flying wings I'm really surprised at how much fun this thing is to fly. Energetic, highly responsive and stable. Good roll rate and great inverse performance.

Wing Span: 52�
Weight: <3 lb
Wing Loading: ~10 oz/sq.ft
Sweep of Leading Edge : 30º

A short video I made with my son: http://www.zippyvideos.com/3187948355434396/zagi/

The plan: http://www.wm-designs.com/corozag_1.0.pdf

Enjoy!
Joe

Stubshaft

Looks great. I was thinking of scaling it down slightly and using a OS FP.10 engine.

joe_weisman

Thanks.

If you go down to a .10 engine and use all HS81 micro servos you'll loose about 10% of the total fly away weight, but will have just about half the power.

Some weight could be shaved off by building the spar & engine mount a little lighter. This should be possible because you're carrying a smaller engine, flying slower and lifting a lighter weight. Also use smaller wing tips, maybe half size. Mine look cool but are probably bigger than needed.

Other than that you'll have to downscale. If you reduce everything to 75% size and build lighter as mentioned, you should be able to come in at about half weight, with your wing area about 56% of the plan. My guess is that it'll fly nicely.

Good luck, and please report on how it goes.

Joe

Stubshaft

Thanks for the tip. I'll let you know what happens.

Turbobeaver

Well I thought this one deserved to be bounced back to the top again for discussion.First off,let me congradulate Joe Weisman on designing such a cool SPAD.I'm definitely a bit of a critic when it comes to model aircraft and I don't candy coat what I conceive to be poor design and flight performance of a model.I think a well designed model should be able to stand on its own merit and this is one such model IMHO.

After two weeks of on again,off again construction and frequent intervals of b**l scratching trying to figure out how to stuff gear inside the wing,I finally got it finished up and decided to take it out to the field to see if it would actually fly.After building two SPA3DT's that gave very poor performance,I wasn't about to waste any more vtime on things like graphics until I was assured that this wing could actually fly.Not just fly but actually fly well.A plastic bag caught in a summer time thermal can fly to but that's not my idea of flying and I don't expect my planes to perform that poorly either.

Well after arriving at the field and setting up,I checked over all the controls and throws one last time,range checked it and fired her up.Engine is a Thunder Tiger .25 Pro swinging a el-cheapo MAS 9x4(yup,I was expecting the worst despite my best guess at where the Cof G should be).With engine screaming and a light slightly nose high release,she flew out of my hand and started a quick bank to the left into rather tall grass about 4 feet off the ground and the engine started sagging and down she went.Chock up one broken 9x4 prop.Replace the 9x4 with another el-cheapo special and re-tune carb and check running nose up and down and throttle transition.Fire it back up again and this time I had a friend hand launch it for me so I could keep my hands on the sticks at all times until I got it trimmed out.Up and away she went and I took her to altitude where I trimmed her out and started to get the feel for this thing.After a 12 minute flight,I decided to bring it in while I still had power.I chopped it back to idle and tried to bring it in a bit on the fast side not knowing what would happen tip stall wise if I slowed it down too much.About 2 feet off the deck and almost a touch down,sure enough,she started to tip stall to the left despite mt best efforts to prevent it.It seems to be a plane that has to be flown a bit on the fast side all the time or else the controls feel sloppy and you can see signs of a snap or tip stalling about to happen.A third flight and further experimentation confirmed this finding again.It doesn't like to be flown slowly at all and will stall and spin if your not ready for it.What I need to find out now is why is the plane tip stalling at these slower speeds?It seems to fly just fine at the higher speed levels.Other than this problem,the plane is a real joy to throw around the air.It's different and looks cool in the air and for the same reason Joe originally built this for,I've always wanted to try my hand at a flying wing to.Way to go Joe!

Gringo Flyer

My Feedback: (18)

Joe, those are fantastic plans. Very detailed and lots of color pics, thxs. I would have paid double what you are charging for them.

joe_weisman

Thanks guys!

Great report Turbobeaver! Really makes writing those plans all worth while.

Since my last post I've built a corozag glider for slope soaring.
I haven't had any wind since that build, so I've been testing its durability by trying to launch it in various creative ways. Video of a failed tow attempt with a Spadet: [link]http://www.zippyvideos.com/2504534195827786/corozag_tow/[/link]

So that make three builds for me so far:


Turbobeaver, I've actually been looking pretty closely at low speed CoroZag flying lately, and I've found a pretty cool stable deep stall type of flight characteristic. Slowly pull back all the way on the elevator, and it'll sit in a stable stall condition, with elevons still responding to roll inputs! Add some power and it'll float around in a sort of a "Harrier". It's not really 3D, but it's interesting.

Here's a short video of CoroZag stalls that I took a few days ago: [link]http://www.zippyvideos.com/1408991835880316/zagi_stalls[/link]

I'm just guessing, but if it feels like you're running out of "up" too soon, you might try to move the CG backward. Just a wee bit at a time to stay out of trouble.

I'd love to hear if this changes anything.

Joe

Turbobeaver

Hi Joe.Can you tell me if you have experienced these stalls with any of your Corozag's and if so,when is it happening?I am seeing it show up at roughly about half to 1/3 throttle while flying just straight and level.I've been playing around with the airspeed to determine roughly what airspeed the stall occurs at and does the break always hapen in the same direction.If you try gliding it back dead stick it will continue to fly up to a certain airspeed and then all of a sudden,one wing tip will start to stall and tip.If your too high up off the field,this could result in a real bad cart wheel no doubt badly damaging the model.Seen this many times before with various other models over the years.Anyone thinking about building a Corozag,I highly recommend putting on the front skid wire and wing tip skids on this plane.It prevents breaking props and denting the hell out of the underside unneccessarily on those fast landings.Sure glad I put them on for sure.If I had it to do over again,I would wash out each wing tip by about 1/4" too improve slow speed handling.You may want to incorporate that idea into your glider design Joe for sure.I flew gliders for years and we always washed out the wing tips for this exact same reason and it made a significant difference in performance for sure.It would be interesting to find out if Zagi slope soaring gliders incorporate any type of washout in their wing design and how do they deal with any tip stalling issues.I don't how much the C of G range would affect this or not.It seems to be slightly forward on the CofG now so if I was to move the Cofg back,it should make the stall happen even sooner.That's my hunch anyways.......what do you guy's think?

joe_weisman

Turbobeaver, regarding your suggestion for wing washout, I beg to differ for several reasons:

1. I've built and flown three CoroZags so far, and haven't had special wingtip stall problems.
2. I'm not aware of a way to build washout in a SPAD wing. At least not a way that's simple and accurate.
3. I love the symmetric CoroZag wing and wouldn't want to degrade the inverse performance in favor of the upright. (Daddy loves both children the same.)
4. I think the design has already got it! I'm not an Aeronautic Engineer, but as I designed the CoroZag I developed a little theory. Here it is:

The Magical Zagi Washout

I believe that the Zagi design has an inherent washout function. I'm not totally sure about flying wings, but I assume that the wing chord is still measured from the front point to the trailing edge of the aileron, or in this case the elevon.

Now, in the Zagi design the wings are tapered and the elevons are wider at the wing tips. In a high Angle of Attack (AOA) situation, the elevons will both be UP. Here's the magic: The elevons position somewhat reduces the wing's effective AOA, and the reduction at the wing tips is greater than the reduction at the wing root! Look at the following drawing:



So there it is – built-in washout. I've worked out that with elevons pulled about 30 degrees up, the effective AOA at the wing tips is nearly 6 degrees lower than the AOA at the wing root! That's lots more than the 3-4 degrees washout you'd build into a classic aileron glider wing.

If this theory is correct, you gain a couple of major advantages:
- Washout is achieved with a simple symmetrical build
- Washout is applied as needed, only when you yank the stick! It's not interfering when you don't need it, and it's totally symmetrical! Meaning, it'll work exactly right when pushing the elevon too!

Incidentally, I designed the CoroZag with 14% wing thickness at both the root and the tips. I've built and flown over 15 HOR wings and have found 14% (28 mm spar on the HOR) to be the greatest! They're highly maneuverable and they don't tip stall.

Turbobeaver -
I've asked my son, who has also flown all of my CoroZags, about your tip stall issue. My son acknowledges tip stalls in extreme maneuvers, but he didn't notice anything special in toss or landing behavior. (He asked the obvious – is the build warped? I'm assuming you didn't go major wrong there.) With a standard battery pack and an FX engine your plane might be about 3 oz. heavier than mine, and we're not doing scientific comparisons, so we might just be missing something that you see better. Even though it seems counter to your analysis, I'd urge you to try moving the CG a little backwards if it isn't too much trouble. It's interesting to do in any case.

By the way, I've tumbled my CoroZags to the ground in various ways quite a few times, and so far they've been pretty survivable.

Above all – keep having fun!!!

Joe

PS: Here's another short video I shot today. Note that the plane pretty much flies out of the hand, flies around nicely at low speed with nothing more than some wing rocking, and lands without any special problems.
THE VIDEO: [link]http://www.zippyvideos.com/1512692305925116/corozag_slow_flying[/link]

joe_weisman

By the way, Turbobeaver, you said you're using a 9x4 prop. I think a 9x5 prop or even a 9x6 will give you some more zoom with a 0.25FX.

Joe

Turbobeaver

Well,I finally got a chance to toss around the Corozag some more and we are slowly starting to understand the flight characteristics of this plane.One thing I can tell you for sure and it is what I previously predicted and that is moving the C of G further backwards is not how you remedy a tip stalling issue.Man, that was one hairy hand launch and flight session(which I purposely cut short and landed hot while I still had a plane).That thing was so dang sensitive to control input it was almost uncontrollable.O.K,lets try moving it the other way and try again.Bingo!What a difference a 1/4"-1/2" of movement on the C of G makes in handling.It tracks much straighter,hand launches are easier and slow flight seems to have improved a bit as well.I'm keeping it at altitude and playing around a lot with the various power/stall settings and discovering some neat things that this plane will perform.It does a rather nice flat spin for one....inverted or upside down.The 9x5 APC prop gave a bit more speed to the plane but nothing too noticeable.I didn't have a 9x6 to try out unfortunately but that's on my "to do" list next time I'm at the LHS. A low pitch prop is better in sustained climb than a high pitch prop anyways as I've also been playing with the vertical climb rate to see how long it takes before it loses poop and falls back to earth again.I like doing real "BIG" loops with this thing as it seems to fly best when flown fast and the roll rate is pretty quick to.The guy's at the field wonder how I keep flight orientation on a all white, low profile flying wing on a overcast day with no discernible markings to tell up from down.That' what the vertical fins are for I reply.I'm planning on building another one sometime in the near future when time allows.Any idea Joe as to what wingspan I should shoot for for a Thunder Tiger .10 powered Corozag?How about a Thunder Tiger 1.20?Wouldn't that be fun to hand launch[:@].I've got two sheets of 2 mm Coro downstairs that are begging to be air born.Thanks Joe for the explanation on the Zagi washout theory.Makes total sense to me after I read your post.I always wondered why the Zagi ailerons were shaped the way they were and now I know why.Thanks a lot dude!

joe_weisman

I'm really happy that your CoroZag's working out and that my lame advise hasn't crashed it for you!

Last time out I tried to shoot a CoroZag "spins" video, like showing eight or so tumbles to earth in rapid sequence, but I discovered another interesting flight characteristic. It'll only do impressive looking spin type maneuvers when the camera is off.

In other words, I've yet to find a reliable way to spin this one, and I've still got stuff to work on.

I love the big loops too, including inverse onces. Another surprisingly cool looking one is a fairly slow roll (or even a sort of four point roll) at low altitude.

In my second post in this thread I worked out that a downscale to about 75% size should work well for a 0.10 engine. Please don't overbuild that one. It'll be carrying much less weight and I'd consider a 4mm coro only spar on that one. (Not that I've tried it, mind you.)

Joe

Turbobeaver

Well Joe I had a chance to go flying again on Sunday afternoon so I got my gear together and threw the Corozag in the back of the van and off to the field I went.It wasn't the best day for flying with the wind sock flying straight out but what the hay......no fair weather flyers living here.Besides that,I was very eager to find out how the Corozag handled in a stiff breeze situation.With fall here in Canada just around the corner,it's either raining or windy half the time or both whenever you want to go flying it seems.Us die hard RC pilots can't pick and choose weather conditions so you learn how to fly in just about anything short of a full scale hurricane.

All fueled up and ranged checked so off to the races we go.With Thunder Tiger .25 Pro howling and a light toss into the wind,the Corozag was off and picking up altitude into the wild blue yonder.She was still trimmed out pretty good and no further trimming was required(amazing........I hadn't knocked the trims out of wack loading and off loading all my gear getting it to the field.Something to be said for digital trims at times like this).Flying straight into the wind,I was amazed at how well the Corozag penetrated the wind.After 4 flights in "wind sock stiffareeno straight out" wind conditions,I can tell you that this thing really impresses the hell out of me.It didn't bother it in the slightest and it flies equally as well as on a calm day.I'm having so much fun playing with this thing.......I haven't even got the graphics on it yet.That would take away from flying time and probably add weight anyways(ya........I'm lazy when it comes to the artsy colour scheme,graphics type stuff.I'm good at it but I just dread doing it........especially as I get older).

Joe,don't know if you have tried the flat spin move or not but this is how I'm doing it.It may vary from plane to plane depending on A.U.W,control throws and where the CofG is located but this is how I do it and it works every time.Fly straight and level and then pull back all the way on the sticks.My model comes to a complete stand still nose high.By moving the ailerons one way or the other,you can get it to start to flat spin or spiral slowly or quickly.By easing off on the elevator a bit,this will also vary the results as well(tight spin,widespin).It flies very "pizza box" like when it is flying in this mode.My throttle is wide open all the time when I am doing this.By letting go of the sticks or applying a little down elevator ,the Corozag should start to pick up speed and continue to fly as normal again.I haven't been able to pull off any flip flop type loops that you have described Joe previously but something close.I fly with the nose pointed straight up going vertical and then chop the throttle and continue to hold her nose high until she loses airspeed and just flops quickly forward or backwards(a little elevator can help here as well).If it flops backwards,I will throttle up and continue to fly a circuit in this inverted position.Looks cool when it is done integrated into part of a aerobatic routine.I'm still learning some neat stuff about this plane.Yes,this daddy is loving both his children equally as well too..........upside right and upside down.That's one of the things that i am enjoying the most about this plane.........she's a hoot in either party dress!!This is one SPAD I think I will always have in my hangar.Just too dang much fun.

joe_weisman

Sorry for the thread excavation, but the corozag plan has moved to: [link=http://www.combat-il.com/corozag_1.0.pdf]http://www.combat-il.com/corozag_1.0.pdf[/link].

mclina

Thanks for resurrecting this, the original thread was before my time. Definitely a nice set of plans and a cool looking plane. And I just happen to have a spare .25LA lying around.

joe_weisman

Thanks. The plane has survived the test of time - I'm still flying one. If you want to build one - my accumulated experience is to use sturdy material for the firewall. I use the thicker type of plastic cutting board these days, after a few firewalls cracked and broke up along the way.

Villa

Hi joe_weisman
Very nice looking plane and great ideas. Did you ever try to put landing gear on the flying wing?

joe_weisman

Since there's no rudder you can't really taxi, so landing gear would mostly just add some drag. (And it's not the fastest plane out there as it is.) The simple little skid does a fine job.

Joe

Villa

Hello joe_weisman
Thank's for your response. When I was building my SPAD Swept Wing Canard wing, I noticed that the main wing could be a flying wing. I can see your plane as a tricycle gear plane with a steering servo for the front wheel. I seem to do maybe 10 or more landings for every flight so landing gear is a big thing for me.

Team_Monkey

CPD over on SW has a delta (Crazy herb type) with tricycle gear. Flies pretty decent IIRC.

Oh and big-big thanks to Joe for his CoroZag instructions! Found that a few years ago and have used ideas on many planes including the 72" span Wakizashi wing now awaiting maiden.

rsieminski

Can someone check those links? I cannot access the videos or the pdf plans. Great lookin plane. I used to fly the E powered ones at night in the HD parking lot.

joe_weisman

Sorry for the hassle, but the links died. The plan is now hosted here: [link=http://www.combat-il.com/corozag_1.0.pdf]http://www.combat-il.com/corozag_1.0.pdf[/link].

The videos... I can't find those around any more. Sorry.

Joe

rsieminski

Great tutorial! Many thanks, it looks like a smokin' plane.