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Grasshopper
10-25-2006, 10:56 PM
I finally finished my Wattage Stuka. After stripping off the shiny green covering, replacing it with Litespan and airbrushing it, she's ready for her maiden. That may take a while according to the weather forecasts.

I didn't like the shiny green so I airbrushed a desert camo scheme. Thanks to Skysharkster for all his help with the covering. Heres the specs:

AUW 26.4 oz.
ELE EC28P-L Brushless motor
ELE 20 amp ESC
GWS 9075 HD prop
3S 2100 15C Common Sense Lipo
16.9 amps
195 watts

Keep your fingers crossed. I'm a little nervous for this maiden because of all the time I have in it. The last picture (shiny green) is what it looked like out of the box.

DetroitHawk
10-26-2006, 12:29 AM
good looking plane, best of luck!

Cowboy
10-26-2006, 12:31 AM
Keep your fingers crossed. I'm a little nervouse for this maiden because of all the time I have in it.

That is the only thing I dislike about this hobby. The longer it takes me to build a plane the more likely I will crash. Don't get me wrong I love the building part, but then the trepidation sets in on the maiden and some of the fun is lost. Oh well still loving it all. Good luck........The plane looks great!

Don Sims
10-26-2006, 01:13 AM
Beautiful looking plane GH! Best of luck on the maiden!

Jagzilla
10-26-2006, 01:23 AM
The plane looks great!
I have one, and I'll warn you, it's a stall monster! Both takeoffs and landings are nerve racking. Easily the worst I've ever flown. Keep your speed way up on landings, don't try floating it down, or it'll suddenly just drop on you. Same on takeoffs, no aileron or too much elevator input till it gets up to a good airspeed.
I don't want to scare you, or sound really negative, but I figured knowledge is power in this case.
Best of luck in your maiden, she really is a beauty!
J

Sky Sharkster
10-26-2006, 01:29 AM
WOW!!! Hey Tom, That model looks GREAT!!! Man, that desert camo camo out perfect. Where's Rommel?
Did you use an airbrush? How many coats? Don't tell us you used rattle cans, painted one-handed while eating a sandwich, watching TV, weren't really trying...
You're killing me, here! Details, we want the full scoop!
Fine job on the finish, Tom. Hope it flys as good than it looks!
Ron

Grasshopper
10-26-2006, 03:03 AM
Thanks for all the nice comments guys.
Cowboy, you're right about the more time it takes the more nervous I am. My neighbor came over to look at it tonight and his first comment was "And you're going to fly it?" Not only am I nervous because of the time that went into it, but there are a few little things I didn't like about the way it finished. None of which I had any control over because it was already pretty much assembled at the factory.

Don S. thanks for the compliment. If you remember, you were the one that mentioned your P-47 that made me go look it up and found this on a Labor Day crash sale. Thanks, I'm really glad I got it (so far).

Jag, thanks for the flying tips. Don't worry about scaring me, I'm always open to suggestions and help. Especially on flying a new plane from someone who's been there. I didn't figure it would be a floater. They were built like a tank so I assume it will pretty much fly like one too.

Ron, I wish I did it while on the couch eating a sandwich but no. I mixed Testors enamels to get the colors I wanted.

The tan is one part flat light tan to one part flat brown and thined 25%. The blue is one part flat light blue, one part flat white and one part flat light gray also thinned 25%. I really wanted the blue to be even lighter and actually more of a blue gray but I ran out of white and the LHS didn't have any more either. The green camo is flat olive green.

I put on 3 light coats of the blue first then three light coats of tan. Each color set over night to dry. The green camo is one coat with less thinner. I used a Badger single action airbrush. The rust color on the exhaust is flat red, back and brown mixed till I got it looking like rust.

Now if Mother Nature would cooperate, I might get to fly it. Looks like wind and rain for the next few days.

firemanbill
10-26-2006, 03:09 AM
Very nice Tom!

Enjoy it, and keep 'er high!:D

Grasshopper
10-26-2006, 03:14 AM
Thanks Bill. I just hope it makes it up high.

Cowboy
10-26-2006, 03:18 AM
Tom, don't mind me, I'm just sweating bullets with you, sorry. Looked at all the pics, mannnnnn you did a nice job. That will look great on a flyby.:)

Grasshopper
10-26-2006, 03:24 AM
Didn't mind at all Cowboy. Thanks for the compliments.

Voyager2lcats
10-26-2006, 03:40 AM
That is a beautiful paint job. I hope it isn't too much of a beast in the air. I seem to recall the real Stuka was fairly maneuverable and handled well (though underpowered relative to Bf 109s- no surprise). Let us know how it takes off and handles. You shouldn't have any trouble rolling it with those ailerons! Good luck!

Bob

Grasshopper
10-26-2006, 04:20 AM
The plane looks great!
I have one, and I'll warn you, it's a stall monster! Both takeoffs and landings are nerve racking. Easily the worst I've ever flown. Keep your speed way up on landings, don't try floating it down, or it'll suddenly just drop on you. Same on takeoffs, no aileron or too much elevator input till it gets up to a good airspeed.
I don't want to scare you, or sound really negative, but I figured knowledge is power in this case.
Best of luck in your maiden, she really is a beauty!
J

Hey Jag, Did you set your CG 2 5/8" back from the leading edge like the instructions said?

Glacier Girl
10-26-2006, 11:00 AM
Ah Grashopper, nicely done!
Hope she flies as good as she looks.

Grasshopper
10-26-2006, 02:10 PM
Thanks Brad

Jagzilla
10-26-2006, 10:51 PM
Grasshopper, mine is balanced at 70 mm back from leading edge.
J

Grasshopper
10-26-2006, 10:55 PM
Grasshopper, mine is balanced at 70 mm back from leading edge.
J

Thanks Jag. That's 2.75" So you're 1/8" further back than mine. I'm not sure my sophisticated CG machine (index fingers) can differentiate 1/8". Mine is set slightly nose heavy at 2.625"

Thanks again,

Tom

Jagzilla
10-27-2006, 12:52 AM
I use the index finger machine as well, Tom. Cost effective. I'm sure where you have yours balanced is ballpark enough.

I've just been learning the fine art of "vacuum forming". My first project, Stuka wheel spats. Mine that came with the kit are quickly disintegrating. The new one's I've created are much stronger.

Here's a couple of pics of my beasty.
J

Grasshopper
10-27-2006, 01:24 AM
Hopefully you'll post some pics and maybe even offer them as replacement parts.

Glacier Girl
10-27-2006, 12:49 PM
If you suffer from fat fingers, a pair of pencils will work in their place.
Use the eraser end to balance, the darn pointy end tends to leave marks or worse, holes.

Grasshopper
10-29-2006, 03:28 AM
The weather cleared up and I got to maiden the Stuka today. Unfortunately I was a little nervous after nosing in my Spitfire first. The Stuka took off beautiful and needed a little trim to get it straightened out. This is a totally different plane to fly. Ailerons on not real sensitive even for the length they are. Elevator is extremely sensitive. It actually flys pretty well but you do have to stay on top of it. Jagzilla said it is a stall monster and he was dead on. It actually floats in very well but right when you want to set her down, the wing just falls out from under it in a nasty tip stall. I did it a couple of times at a higher altitude to check it out but it even happend twice while landing it. Fortunately it just put a small scuff on the wingtip. A little paint and you'll never notice.

I have a question though. When I put in a lot of up elevator, it pulls up fast but immediately does a snap roll. What causes this? I can't make it roll that sharp with the ailerons but pulling full up elevator snaps it right over. Wierd.

This is not a very forgiving flyer and you do have to keep your eye on it at all times and come in hot to land. It seems like it wants to float with power on so you almost have to drive it down. It does look good in the air though. Here's a few pics.

Tom

firemanbill
10-29-2006, 03:37 AM
Glad to hear your day wasn't a total loss Tom.

I love the last pic. That head on shot is really cool. Makes you think what our fellas in WWII saw with that thing bearing down on them!:eek:

Grasshopper
10-29-2006, 03:46 AM
Thanks Bill. I agree, I wouldn't have wanted to be on this end of those cannons.

Crash Test Dummy
10-29-2006, 04:15 AM
Great job Tom!! Your camo looks 10X better than the stock version. I wonder if the way the ailerons and elevator are mounted [off the wing surface] has anything to do with this stall issue? I guy at my field had a 60 size [gas] Stuka that he crashed. I never got to see it fly, maybe he stalled his too. Just fly her all the way to the ground on landing and you will be fine. Anyway looks great.

CTD

max-nix
10-29-2006, 04:22 AM
Hi Tom
Very nice work!
The tip stalls & sensitive elevator may be caused by the CG being too far aft. Try moving the battery forward a little at a time to see if that helps. Also dial in some expo. on the elevator if you have a computer radio. The ailerons are small, try to get as much travel as possible.
Happy landings
Smasher Bob

Sky Sharkster
10-29-2006, 05:09 AM
Hey Tom, Congratulations! Man, you put a lot of work and effort into that plane, glad to hear it flys. The photos are excellent, it looks very realistic in the air.
Sorry to hear about the Spitfire, hope it's repairable.
That snap roll you're seeing is a tip stall. If left uncorrected it would turn into a spin. The Stuka has so much dihedral I doubt whether it would spin very far, and returning the controls to netural usually allows the plane to right itself, providing you have enough altitude. Normally a bit of washout in both wings and moving the C.G. forward as Bob suggested, would be the recomended "fixes". The best cure for it without changing anything is to keep the speed up.
I don't know if the washout will work on this particular design because of the way the ailerons are set. The other thing you might try is to raise both ailerons a small amount, maybe 1/32" when they're at "netural". This will lower the wing lift slightly but may return the stall to the center of the wing which is the lesser of 2 evils!
Anyway, good luck with future flights and nice job on the build and flying!
Ron

Jagzilla
10-29-2006, 05:32 PM
Just wanted to show the Stuka wheel pants that I managed to make. My first experience at "vacuum forming".

I'm very happy as to how they turned out. It has definitely been a learning experience for me. They were a lot more "labor intensive" than I first realized, but I think this part of the hobby has a lot of potential for me. The white one in the pics is actually the plaster of paris mold that I copied from an original. You can also see the remains of one of the originals in the pics as well.

Grasshopper, reading how your maiden went, reminded me totally of how my maiden went! I too thought mine was a floater, till it suddenly fell out of the sky. I'm glad to hear you only had a minor scuff on the wing tip. Best of luck with the plane in the future!
J

Grasshopper
10-29-2006, 06:40 PM
Those spats look really good. I just finished repairing some cracks in mine after only 3 landings. They should put about 6 extra pairs in the kit for spares.

Grasshopper
10-29-2006, 06:56 PM
Hi Tom
Very nice work!
The tip stalls & sensitive elevator may be caused by the CG being too far aft. Try moving the battery forward a little at a time to see if that helps. Also dial in some expo. on the elevator if you have a computer radio. The ailerons are small, try to get as much travel as possible.
Happy landings
Smasher Bob

Thanks Bob. The battery is as far forward as it can go. It's up against the firewall with a little foam in front of it and the plane balances slightly nose heavy when using the recommended CG points. I'll move the aileron clevises in a notch to get more travel now that I have a few flights on it.

Grasshopper
10-29-2006, 07:01 PM
Hey Tom, Congratulations! Man, you put a lot of work and effort into that plane, glad to hear it flys. The photos are excellent, it looks very realistic in the air.
Sorry to hear about the Spitfire, hope it's repairable.
That snap roll you're seeing is a tip stall. If left uncorrected it would turn into a spin. The Stuka has so much dihedral I doubt whether it would spin very far, and returning the controls to netural usually allows the plane to right itself, providing you have enough altitude. Normally a bit of washout in both wings and moving the C.G. forward as Bob suggested, would be the recomended "fixes". The best cure for it without changing anything is to keep the speed up.
I don't know if the washout will work on this particular design because of the way the ailerons are set. The other thing you might try is to raise both ailerons a small amount, maybe 1/32" when they're at "netural". This will lower the wing lift slightly but may return the stall to the center of the wing which is the lesser of 2 evils!
Anyway, good luck with future flights and nice job on the build and flying!
Ron

Hi Ron,

What exactly is wash out? I've seen it discussed but never truly understood what it meant. As I mentioned earlier, the battery is as far forward as it can go and it balances slightly nose heavy.

The snap roll I'm experiencing is when the plane is flying at almost WOT and I pull up elevator. It immediately does a snap roll as it goes up. Very quickly I might add. As long as I gently pull up it's OK. I've just never had a plane do that before.

Jagzilla
10-29-2006, 07:16 PM
Doesn't a snap roll that results from sudden elevator input usually meant too much throw on the elevator? This especially seems correct here when Tom states if he pulls back gently, there is no problem.
J

ducatirdr
10-29-2006, 07:42 PM
Building a plane this time of year stinks. I have been waiting to maiden my Combat Corsair for a couple weeks. I've been traveling with work but this weekend I had free. The wind is the worst its been in a long time. Next week I travel as well. This stinks...


I too have seen the sensitive elevator and it was with my PZ FW190 and lipo. I think its snapping due to a tip stall as it only happens with full throw. I put the extra nose weight on but it still does it. I have to be careful not to hit full throw at the bottom of a loop. That's where it happens the most. I was thinking aileron flutter...???

watt_the?!
10-29-2006, 08:57 PM
great thread guys!

i got me one of these in my shed collecting dust....excellent work, fantastic pics, great subject!

max-nix
10-29-2006, 09:45 PM
You can better confirm the balance by flying.
First trim the aircraft for hands off full power level flight, then climb to a safe altitude and initiate a 45* dive, when you release the controls the aircraft will either nose down when tail-heavy or nose up when nose-heavy.
This may seem counter intuitive, but when the a/c is tail-heavy you must trim it with a small amount of down elevator trim, & when the airspeed increases in the dive the trim becomes more effective causeing a nose downward attitude.
(Converesly for a nose heavy condition & up trim).

Tip stalls, snap rolls,sensitive elevator & a floating approach when landing can all be caused by a tail-heavy setup. This is easily determined by the above flight test. If the balance checks out THEN go on to other corrections.
Also keep some power on when landing until you are ready to flare!

Happy Landings
Smasher Bob

Sky Sharkster
10-30-2006, 01:47 AM
Hello Tom, Washout is a twist or "warp" along each half-span that raises the trailing edge slightly at the tip, relative to the rest of the wing. If you were to lay a wing (say, a wing with no dihedral, for the sake of this illustration) on a flat surface, the center L.E. and T.E. would be flat on the surface, the tip leading edges would be flat on the surface, but each tip trailing edge would be above the surface a slight (and equal) amount. One or two degrees is usually enough.
The purpose is to make the tips stall after the center section, which means, in the event of a stall, the plane won't "fall off" on one wing or the other. The center stalls first, the tips are still lifting (lower angle of attack) so the center section drops, no tip stall, no spin, better chance to recover.
It's used in many full-sized aircraft and models, it is considered an important stability and safety feature. Here's a link with a drawing, also if you do a search for "Angle of Attack Wash out" you'll find many useful references.
http://www.aerospaceweb.org/question/dynamics/q0055.shtml
Many wings, especially moulded and vacuum-formed wings have the washout built into the forms and there is even a way to use different airfoils at the center and tip (progressive washout, aerodynamic washout) so the tips stall later than the center. This is considered better for maintaining the washout than "twisting" a flat wing.
Hope this helps!
Ron

jb48
10-30-2006, 11:13 AM
The sudden snap roll your Stuka is experiencing when applying fast high amplitude up elevator seems to be related to a high speed stall. Remember that it`s not the speed that makes an airplane stalls, but its angle of attack relative to the flight path of the aircraft. When the elevator has too much authority it can happen that it produces a sudden increase in the wing`s angle of attack exceeding the stall`s true angle of attack, which is usually around 17 or 18 degree relative to the airflow: the aircraft nose (and wing) go «up» quicker than flight path and abruptly stalls. Just add a characteristic of a wing stalling first at the tip and you have found the recipe for an unwanted snap roll. Not a problem at safe altitude but deadly when too low to recover. Program less travel in the elevator and be gentle when pulling down the right stick.

Grasshopper
10-30-2006, 02:14 PM
The sudden snap roll your Stuka is experiencing when applying fast high amplitude up elevator seems to be related to a high speed stall. Remember that it`s not the speed that makes an airplane stalls, but its angle of attack relative to the flight path of the aircraft. When the elevator has too much authority it can happen that it produces a sudden increase in the wing`s angle of attack exceeding the stall`s true angle of attack, which is usually around 17 or 18 degree relative to the airflow: the aircraft nose (and wing) go «up» quicker than flight path and abruptly stalls. Just add a characteristic of a wing stalling first at the tip and you have found the recipe for an unwanted snap roll. Not a problem at safe altitude but deadly when too low to recover. Program less travel in the elevator and be gentle when pulling down the right stick.

Thanks jb,

I took some of the travel out of the elevator last night. We'll see how it works next time. That is if the 40 mph winds die down.

Tom

Grasshopper
10-30-2006, 03:31 PM
Hello Tom, Washout is a twist or "warp" along each half-span that raises the trailing edge slightly at the tip, relative to the rest of the wing. If you were to lay a wing (say, a wing with no dihedral, for the sake of this illustration) on a flat surface, the center L.E. and T.E. would be flat on the surface, the tip leading edges would be flat on the surface, but each tip trailing edge would be above the surface a slight (and equal) amount. One or two degrees is usually enough.
The purpose is to make the tips stall after the center section, which means, in the event of a stall, the plane won't "fall off" on one wing or the other. The center stalls first, the tips are still lifting (lower angle of attack) so the center section drops, no tip stall, no spin, better chance to recover.
It's used in many full-sized aircraft and models, it is considered an important stability and safety feature. Here's a link with a drawing, also if you do a search for "Angle of Attack Wash out" you'll find many useful references.
http://www.aerospaceweb.org/question/dynamics/q0055.shtml
Many wings, especially moulded and vacuum-formed wings have the washout built into the forms and there is even a way to use different airfoils at the center and tip (progressive washout, aerodynamic washout) so the tips stall later than the center. This is considered better for maintaining the washout than "twisting" a flat wing.
Hope this helps!
Ron

Thanks Ron, That's kind of what I thought it was. I've built warps into wings before but it was never intentional or controlled. The Stuka actually flys very nice hands off at about half power. I think a lot of it is what jb mentioned with the elevator travel. It has a bunch. I don't usually set dual rates on my maidens (may be a bad practice) but I like to have full control and just go easy on it. I took some of the elevator travel out last night and will try it again.

Tom

Jagzilla
11-11-2006, 12:54 PM
Tom,
Hows the Stuka working out for you? I assume you've gotten a few flights in on it?
J

Grasshopper
11-11-2006, 04:06 PM
Hey J,

I haven't had a chance to get it out since its maiden. I have made some adjustments on the elevator throw and repaired the little cracks in the wheel pants. You may want to check the glue holding your firewall in. When I was checking mine over, I noticed the firewall had come loose. The glue they use on that kit isn't the best. I had to epoxy the servo tray in when I was building it and now I had to epoxy the firewall in. It's like they used a really cheap hot glue.

How's yours doing?

Tom

Jagzilla
11-11-2006, 05:05 PM
I did add glue on both the servo tray and firewall as I was building the kit. I'd read up on the problems associated there in the other build link. The last two outings with mine both resulted in a broken wing. One scew up on takeoff, another was on a bad landing. I have fixed the wing both times and I've put the wheel spats that I made on it. Between bad weather, and doubting that I can actually reliably fly the Stuka, I've not flown it since. As much as I love the look of this bird, I don't think I'm going to have much luck with flying it.
Jaggy

Grasshopper
11-11-2006, 05:28 PM
Sorry to hear about the crash. Yeah, this is a weird bird to fly. It is so cool looking though. We'll see how it goes.

cyclops2
11-11-2006, 08:58 PM
Floaters with LONG fuselages between wing and tail CAN be OK with problems.

Short rear bodies are touchy.

Everything I write about below is to be done ONLY in TALL grasses. Over 2' high.

Rudder,elevator and ailerons are first set to 0 degrees by the transmitter-- the the RECEIVER is FIRST shut off, then the transmitter. Do not change them until the glide is perfect.

I FIRST do everything with NO PROP and increasingly harder hand tosses till everything is great. I am 68 and easily toss 7' A-10's fast enough.



Wing load is only 1 to 1.5# / sq. ft.------Never had to toss a 2 to 4# brick fast enough.

If a plane is gliding and bleeding off speed slowly, then begins the slightest up and down, pitching, of the plane in a series of tiny stalls and self recoveries.

It is about ready to stall. Nose it down to build speed up.

Actually it needs to be adjusted in the wings A.O.A. and or, move the battery foward a small amount.

If the A.O.A. is to high, I find the plane is prone to pitching up and down slightly at about 2/ second. lower the front of the wing or raise the trailing edge SLIGHTLY. 1/64" at a time. YA, YA. it sounds like nothing. It WILL stop pitching and stalls. Now the plane is set up to ALWAYS go to a flat glide.

A COG too far back causes a steady slowing down till the plane just falls out of the air with the nose dropping once to the ground.

This is why I only toss a new plane over DEEP grass.

Now move the battery SLOWLY rearward or foward until the plane starts the odd movements again.

If you keep slowly playing with the AOA & COG the plane will scare the tea leaves out of you on it's gliding abilities.
I saw a .40 size Ugly Stick glide over several hundred feet to land at the pilots feet. I have never seen ANY other plane milk out a glide like that.

You know the AOA & COG were right on. :)

alienx
11-11-2006, 11:13 PM
Grasshopper. Nice plane! I am really impressed with the finish you put on it. I llike that picture of theh plane coming at the camra. I just saw a show on the history channel yesterday of the Battle of Britain. Great planes.

Grasshopper
11-11-2006, 11:58 PM
Thanks for the info Cyclops. I think I've about got it straightened out but I'm going to bookmark this info for future reference.

Alien, thanks for the kind words. I just got back in from flying it again. Man is it a handful!!!! The main problem I have is the wheel pants are so flimsy they crack and snap off on the slightest bump. I was flying off really short grass this evening instead of the pavement I maidened it on. I may fasten the pants on with velcro this time so they can come loose without cracking.

I started laying out my P-38 last night. It is sooooooooo cool looking and so much bigger than any of my other planes. I'm really anxious to get it going.

Grasshopper
11-15-2006, 11:12 PM
Well I flew the Stuka again this past Sunday and man was it a handfull. The minute it took off, it seemed like it just wanted to have the tail hanging down and drag it around. For some reason, it was flying completely different this time. I brought it right back down and put it away.

Last night I started looking it over and re reading some of the pointers I've been given in this thread and they all seemed to be indicating it might be tail heavy. I checked the CG and it did balance out at the recommended CG points. I'm not reall knowledgeable on determining CG points if they aren't given to me in the instructions, but it seemed to me the CG should be moved forward a bit. (Please let me know if I'm wrong here). I measured out the recommended CG points and then moved it forward 1/4". The tail immediately dropped like I added a pound of lead to it. In order to get it balanced again, I had to add 3/4 of an ounce to the nose so it would balance just slightly nose heavy.

Does all this make sense? I would think this should make it more stable in flight but again, correct me if I'm wrong.

Thanks,

Tom

Jagzilla
11-15-2006, 11:42 PM
When I have a plane that suddenly flies far different than the last time I flew it, and I hadn't adjusted anything on the plane, I'd be looking for some sort of mechanical failure somewhere in the plane, or even possibly trim adjustments on the tx. It seems odd to me that the cog is suddenly wrong, after you have flown it a few times, and seem satisfied with it's first flights. Perhaps binding linkage, servo problem, trim etc. should be examined. Just my two bits,Tom
J

Grasshopper
11-16-2006, 03:52 AM
When I have a plane that suddenly flies far different than the last time I flew it, and I hadn't adjusted anything on the plane, I'd be looking for some sort of mechanical failure somewhere in the plane, or even possibly trim adjustments on the tx. It seems odd to me that the cog is suddenly wrong, after you have flown it a few times, and seem satisfied with it's first flights. Perhaps binding linkage, servo problem, trim etc. should be examined. Just my two bits,Tom
J

Good point Jag,

I'll give it a good looking over before it goes up again. Even the first few times I flew it, it seemed to always be on the edge of a stall but not near like this time. Now that you mention it, I did change props but it seemed to take off pretty quickly. Either way, I'll check it all over.

Thanks

pd1
12-01-2006, 02:11 PM
Tom, Here's the info you wanted.

My Stuka, E-flite 400 outrunner, 1500 mah 3 cell. Spektrum radio.
AUW: 25 ounces. Wing Area: 250 Sq. In. Wing loading: 14 oz./sq.ft.
CG: 2 3/4 inches from leading edge, measured at fuselage.
There is a short vertical line on the fuselage molded in at that point as well.
Distance from center of wing to elevator hinge line: 17 inches.

Reduced elevator throw, added drooped leading edge cuffs.

Comparison to E-Flite P-47. Dynam A2022L outrunner. 2100,mah 3 cell.
AUW: 26 ounces. Wing Area: 260 sq. in. Wing loading: 13.8 oz./sq. ft.
CG: 2 1/4 inches from leading edge, measured at fuselage side. Spots molded in wing.
Distance of center of wing to elevator hinge line: 19 inches.

Both planes have very similar dimentions.
They SHOULD fly similar, they don't.

pd1
12-01-2006, 02:38 PM
Tom, I'm going to make multiple posts. I typed up a long reply last night pushed some wrong button and it was all gone. I'll try short posts so I don't loose too much when I screw it up again.

I include a wing center measurement to elevator hinge to show you the Stuka is shorter coupled than the P-47.
Cyclops was right, short coupled can cause problems. The tail only has to move a little to get a lot of pitch up Angle of Attack change.
If you were flying in the Stuka you would have a very heavy stick feel.
Since you can't feel the stick forces, it's very easy to over pitch the plane.

JB48 was also correct, an airplane stalls by too much angle of attack to the relative airflow.
Your elevator has too much authority, you over pitch, you stall, you snap.
Reducing the elevator throw will give you the most relief.
I reduced my elevator throw drastically. This stopped the snap roll tendency while in normal flight.

Moving the CG forward will have a similar effect.
If you thought of an airplane as a see saw, with the fulcrum at the center of lift, the cg as a force ahead of this center of lift pulling the nose down.
The stabiliser as another force on the other side of the fulcrum pulling the tail down to counteract the cg's force. The forces will ballance out to get level attitude.
If the CG is moved forward from it's position, that force times its distance will give you a moment.
That moment is greater than it was before you move the cg.
The stabiliser has to counter that force in order to change the airplanes angle, the force required is now greater than before.
The elevator is now less effective than before.
Less able to over pitch the airplane.

Should the CG move, or the elevator throw be reduced?

If the airplane flys level, and the elevator is in the neutral position, then the CG is correct, reduce the elevator throw.
If when the airplane flys level and the elevator is somewhat down, then the plane is tail heavy, move the cg forward.

You can also effect these changes by wing incidence changes.
Since the airplane was an ARF, and the incidence was preset, I'll assume they are correct from the factory.
Since they work on my Stuka, they should work on your's as well.

pd1
12-01-2006, 02:54 PM
Getting more lift. In post 49 I have some pictures of the drooped leading edge cuffs I added to my plane. I had made them for a demonstration, and I flew with them. They do add a lot of lift at the tip, and they do make the airplane float better.
They won't stop the plane from stalling on landing if your approach is wrong.

The Stuka has a lot of parrasite drag, It slows pretty fast. Lighter sport planes reduce speed more slowly, this lets lift bleed off more gradually.
The planes mush in without the sharp stall and wing drop the Stuka likes to do.

There are two courses available to get around the Stukas sharp stall characteristics.
We can cause part of the wing to loose lift earlier, letting the plane mush while retaining some good lift with the rest of the wing.
Or we can make some part of the wing lift more, accomplising the same thing.

Wash out: if you draw a line from leading edge to trailing edge we can call that our chord line.
That chord line is how we set wing incidence.

If the chord line of the wing tip is set at a lower angle that the chord line at the root we have washout.
Net result the root will reach it's critical angle of attack and stall before the wing tips.The loss of lift from the root stalling will cause the plane to settle, while the tips still lift, maintaining a stabile airplane.

Stall strips: triangular shaped strips on the leading edge of the wing to cause a disruption of the airflow in a localised section of the wing at high angles of attack.
Again cause the root to stall or just loose some lift while the tips are still flying. Stabile sinking.

Drooped leading edges: see pictures in post 49.

Other devices, there are many, but I'm staying with just these.

Since the plane is already finished, I think washout is harder to do than lift control devices.

Since the plane is not light, I opted for increasing lift.
I put the cuffs at the tip, this increases stability and allow the lift to drop off at the root as the speed drops.

The root does not stall. If the root stalls, the tips stall. The airfoils are the same, their incidence angles are the same, they will stall in the same pattern as other tapered wings.

pd1
12-01-2006, 03:34 PM
Stalls:
As an airfoil section goes throgh the air some air is forced over the wing, and some is forced under the wing.
For now lets just disscuss the air over the top.

At zero angle of attack the airflow is pretty much over the whole wing, front to rear.
As AOA(angle of attack) is increased, the airflow separates from the wing, starting at the trailing edge and moving forward. The more the AOA increases, the more the separation point moves forward,until the airflow seprates completely, this is the stall. It's also the airfoils critical angle of attack.
The critical angle of attack is independent of speed, weight, and aircraft attitude.
If the critical angle of attack is reached the wing stalls. Period.

As the wing gets close to stall angle, the airflow separation point has moved forward. The airflow over the trailing edge is minimal, there is a very low air pressure area over the ailerons. Raising the ailerons will have little to no effect in high angle of attack situations.

This reduced airpressure is a contributing factor in why we have adverse yaw. The aileron raise into this low pressure area does very little to nothing. While the aileron lowered into the smooth airflow below the wing experiences drag from the higher pressure.

I was on a flight in a small plane. the plane took off in rain, climbed to seven thousand feet, leveled off, accelerated to 250 mph and water was still on the wing in front of the ailerons.
It didn't blow off, because there was not enough airpressure to blow it off.

The point is if you raise the ailerons, you don't change the angle of attack, you lose lift and it doesn't help you solve the problem.

Lowering the ailerons: Lowering the ailerons will get more lift, but thats not the problem.
Aside from the sharp stall, the airplane flys fine.
You can lower the ailerons a little, to get more lift, but if you lower them too much you get a lot more drag as well.
If you get more drag the airplane slows even more rapidly, that will only compound the problem.

The airplane must be flown with a steep approach to landing, this keeps the speed up and the angle of attack down, a flair close to the ground then a landing. If the flair is right, the landing takes place before the plane drops far.

pd1
12-01-2006, 03:55 PM
Wing shape and stall propagation.
A rectagular wing(constant chord): the stall will start at the trailing edge of the wing at the root and radiate out to the leading edge and tip.

A tapered wing: the stall starting point moves from the root to a new position closer to the tip. The higher the taper the closer to the tip the stall starting point is. On mildly tapered wings there will be a lot of lift loss long before the tip stalls.

Eliptical wing: Stall starts fairly evenly from the trailing edge to the leading edge, along the entire span.

Sharply tapered wing: exagerated shape, wing tip is a point, like a delta. This shape has the stall start closest to the tip.

The constant chord wing is the least likely shape to have the tip stall. The very highly tapered is the most likely shape to have the tip stall.

The word "tipstall" is not a good description of what is actually happening, but used in the context of the wing stalled and dropped.
It is generaly accepted in these forums as the word to describe this action.
Tip stall as used in my description refers to just the tip portion of the wing.

Grasshopper
12-02-2006, 02:38 AM
Wow! What a great write up pd1. :D Thanks for all the info. I've read through it several times now.

I appreciate all the help you've been on this. :)

Tom

Crash9
12-02-2006, 05:53 AM
I've been following this thread and pd1 post here is very helpful. Thanks

pd1
12-02-2006, 01:55 PM
Tom, the explanations are as short as I could make them. If there is anything that's not clear, I will be happy to give you a more detailed explanation on individual problem areas.
Paul

watt_the?!
12-02-2006, 07:58 PM
Wow! What a great write up pd1. :D Thanks for all the info. I've read through it several times now.

I appreciate all the help you've been on this. :)

Tom

be sure to give anyone who's post helps you out a reputation point as well as a compliment...its the gift that keeps on giving!..lol.

Tim

PS great stuff PD1.

I_Love_My_ABC
02-15-2007, 01:32 AM
Hi guys, I just wanted to say that your paint job of teriffic on the JU-87 Grasshopper. I have one of these too, actually it's my second Stuka after this ill-fated maiden...

http://www.youtube.com/watch?v=6O6gnVyojFk

The result was a total write-off as unfortunately, the crash survivability of the vac-formed Wattage fuselages is very poor. The fuse looked like it had been split and then torn open, the inner skeleton was smashed, bent prop shaft, smashed wing, elevator, one aileron broke off etc. What happened?? I just don't know...

Perhaps one of you guys can do an "Air Crash Investigation" on the video footage and come up with some answers for me. Just seemed to roll over and go nose in.

It wasn't a big deal though as I picked up a replacement AFR for $50.00AU (About $38.00US) from a friend who runs an RC store. We patched up the smashed on as best we could to use as his store display model. All the electronics were Ok so the re-build only took a couple of days, but 6 months down the track I am yet to maiden it!!

To say I'm a little nervous is an understatement, but I want to wait for dead calm conditions first and I've been kind of concentrating on other planes in the hangar recently. Sometime next week I'll video the new maiden and have a bit more luck this time!!

Mine is still totally stock, I just love Grasshopper's paint job. Looks teriffic!! Think I'll try a bit of a touch-up too!!

Grasshopper
02-15-2007, 01:47 AM
Hello I Love,

Thanks a lot for the compliments on the paint job. Thats too bad about your JU-87. The only thing I can think of after watching the video is that it might have stalled from too much up elevator. Mine was doing the exact same thing when I would give it very much UP at all. I had to really tame it down and be very gentle on the elevator movements. Mine did the same thing on its maiden but fortunately, I was high enough to recover when it happend.

I cut the elevator movement in half and it's much better but it still does it if I pull up too hard. It immediately stalls and rolls over just like your did.

I'm not sure if that's actually what caused yours but it sure looked familiar.

I_Love_My_ABC
02-15-2007, 04:59 AM
Yep, it all happened so fast too!! I took off and the next thing I knew I had a pile of twisted balsa, plastic, servos and various electronics scattered across the field!! What are the approximate throws (In millimeters) you have set for your elevator now??

It's funny, but warbirds always throw me, I know every thread I've ever read about it has always said that you need very little elevator throw but it always looks like there's not going to be enough!! I plan on using dual rates, that seems like the safest option as you can switch to full throws in the air...

By the way, how's you Stuka flying now?? Did you sort out the C.G. problem yet?? Have you had a chance to fly it again??

Todd

Airhead
02-15-2007, 05:57 AM
Super nice job Tom...:D
Good for you..Enjoy.

Grasshopper
02-15-2007, 03:04 PM
Yep, it all happened so fast too!! I took off and the next thing I knew I had a pile of twisted balsa, plastic, servos and various electronics scattered across the field!! What are the approximate throws (In millimeters) you have set for your elevator now??

It's funny, but warbirds always throw me, I know every thread I've ever read about it has always said that you need very little elevator throw but it always looks like there's not going to be enough!! I plan on using dual rates, that seems like the safest option as you can switch to full throws in the air...

By the way, how's you Stuka flying now?? Did you sort out the C.G. problem yet?? Have you had a chance to fly it again??

Todd

Hi Todd,

I did get the CG straightened out on the Stuka. I also reduced the amount of elevator throw by half but it still needs reduced further. It still stalls and rolls when pulling up very hard. I haven't had a chance to fly it at all lately because of the weather but as soon as it warms up, I plan on spending some "Quality time" with it and trim it all out. I do believe that no matter how you trim this thing, it is always going to be a Stall Monster. I don't have any problems with it in normal flight, but there is a fine line on landings where the wing just falls out if you slow it down much at all. My advice would be to always land it pretty hot.

Dual rates are always a good idea on maidens and the first few flights but you won't need them much on the ailerons. I've actually increased the throw on the ailerons and its rolls are still VERY slow. Although I don't think the Germans intended it to be an aerobatic plane.

Hope this helps a little.

Super nice job Tom...:D
Good for you..Enjoy.

Thanks alot Bruce. I wish they flew as good as they look.

pd1
02-15-2007, 09:59 PM
I Love my ABC, I watched your video, sorry about the ending.

I have more questions than answers though.

I saw the plane roll a small amount one way then a larger amount the other way, all the way to inverted.
The roll seemed to stop there, while the plane just dropped it's nose and lawn darted.

1, Was the ailerons overly sensitive?
2, Were you useing rudder with the ailerons?
3, When the plane went inverted did you try to roll out?
4, Any possibility of a radio glitch?
5, While inverted do you recall making any control inputs?
6, There had been a few reports of the servo tray in the fuselage moving or coming loose.
If it did would that movement give you left rudder and up elevator?
7, Can you check the wreckage to see if the servo tray is still attached or loose?

Sorry for all the questions, but your crash is perplexing.
I would like to know what happened.

I_Love_My_ABC
02-18-2007, 09:25 PM
...
1, Was the ailerons overly sensitive?
2, Were you useing rudder with the ailerons?
3, When the plane went inverted did you try to roll out?
4, Any possibility of a radio glitch?
5, While inverted do you recall making any control inputs?
6, There had been a few reports of the servo tray in the fuselage moving or coming loose.
If it did would that movement give you left rudder and up elevator?
7, Can you check the wreckage to see if the servo tray is still attached or loose?...

PD1,

I don't remember much about the inputs but I'll try to answer each one...

1, Yes, the ailerons were set to full throw
2, I don't think there was any rudder input at the time
3, Yes, I definately tried to roll out of it
4, Always a chance of a radio glitch (They don't tend to discriminate!!)
5, Probably tried to pull back on the elevator stick, wouldn't have helped
6, The servo tray was disconnected, but so was everything else!!
7, See 6

Tom,

I'll back the elevator dual rate throws down to around 20% / 50% and see how that goes. Currently seet to around 40% / 80% so this could be the problem. I will have the video camera rolling during the maiden, no matter what, so it'll either be another boring maiden or another event of total carnage.

Cheers!!

Todd

Grasshopper
02-18-2007, 09:47 PM
Good luck with the maiden. I hope it is boring. You can always make it more exciting a few flights later.

pd1
02-20-2007, 09:47 PM
ABC, If your ailerons were indeed working and you tried to roll it out, I think we should have seen some roll movement in your video.

I don't think your plane stalled. From your discription I do think there was a controll malfunction.

My guess is that either the radio failed or the servos broke free.

I would suggest checking the radio out on a known working airplane first, just to be sure.

I_Love_My_ABC
02-21-2007, 10:56 AM
I use the same radio, a JR Propo Max66, with a brushless Art-Tech Cessna 182, brushless GWS Pico Tiger Moth, brushless GWS Slow Stick, stock Great Planes Flatout Turmoil, stock Multiplex Easy Glider Electric the ill-fated JU-87 Stuka Mk I and it's yet to be maidened JU-87 Stuka Mk II.

I can say with a certain degree of certainty that it was probably not a radio glitch. As for the servo tray coming loose, well anything is possible I guess... I'd be more inclined to believe that it was either pilot error, too heavy on the elevator during take-off or an act of God!!

Grasshopper
02-21-2007, 03:10 PM
ABC,

You might want to double check all the glue joints in the fuselage. Now that pd1 mentioned that, I remember my servo tray and firewall came loose during the assembly. They were just barely glued with a cheap sort of hot melt. I epoxied mine in place before the maiden.

I_Love_My_ABC
03-08-2007, 01:29 PM
Hi all,

Just thought I'd post the link to today's long awaited maiden of my MK II Wattage Stuka. Myself and a friend, decided to maiden out planes today (JU-87 Stuka & C.A.C. Boomarang) with differing levels of success. Luckily I escaped any damage to the Stuka from a rough landing caused by too low airspeed and a minor tip-stall.

Jon was not so lucky, he broke off a motor mount on launch, but the damage was not fatal like my first Stuka maiden!! A great morning out flying so have a look and tell me what you think...

Early Morning Maidens

Large Broadband Version
http://www.youtube.com/watch?v=tgO04cPkpb0 (http://www.youtube.com/watch?v=tgO04cPkpb0)

Small Dial-Up Version
http://www.youtube.com/watch?v=6doa9AEm5dE (http://www.youtube.com/watch?v=6doa9AEm5dE)

Be warned, there is a close-up of my melon-head so watch this video with caution!!

Enjoy!!

pd1
03-08-2007, 02:08 PM
Nice test flight. Plane looked good.
Way to go.

Grasshopper
03-08-2007, 02:19 PM
Good job ABC. Makes me want to get mine out again.

DetroitHawk
03-08-2007, 03:39 PM
nice job on the maiden.

You guys have some brass balls launching from such a narrow pad.

Jagzilla
03-08-2007, 03:47 PM
Really, really happy for you!!! Great vid, and fantastic to see you having some fun finally with your Stuka! Sorry to see your friends 2 second maiden, part of the hobby I guess. The Stuka just looks great up in air.

Mine has been sitting in the hangar all winter, just daring me to try and fly it again. Seems most outings result in me coming home with something on it broken. I've broken the wing twice, and wheels quite a few times. The Stuka is my one plane I just can't seem to get it together with. Your vid is inspiring, but my Stuka gives me the freakin' willies!!!
Jag

fezz
03-08-2007, 04:03 PM
great video
loved the intro.
had to pass it along