thejetman

My Feedback: (1)

I have built a Great Planes Super Decathlon 40 Kit. So far four take off's and four roll over crashes. On take off it rolls to the right or left hard and cartwheels. It is kind of a tip stall. I can't recover from it. It all happens about five feet off the ground. The stab is set to 0 degrees relative to the thrust line of the plane. Wing is set to 1 degree leading edge up all the way across the wing. I have set the eng thrust to -2 degrees and then again at +1/2. It has the 2 degree right thrust. The cg has been set nose heavy and again just barely nose heavy. I am using a MDS 48 with a 11-5 APC prop. The last crash took off the tail. If I can't find any answers I am going to trash the plane and move on. I have rebuilt it two times so far. Please let me know if you might have some help on the planes flying habits.
Thanks.
Keven

LuvBipes

My Feedback: (4)

Lost mine years ago due to a similar problem. The plane is known for having bad tip stalling tendencies - a Cub it ain't!

More recent realese of the kit contain an addendum to the plans that call for 2 degrees of washout on the wing tips to try to tame the beast. If you can't add the washout, since the plane is already built, another trick to try is to RAISE BOTH AILERONS about 1.5 turns on the clevisis.

Yes, that's right - RAISING the ailreons is another way to create a washout effect, which reduces the plane's tendency to tip stall.

Another thing to try is to reduce the elevator throw, or to include 30 to 40% NEGATIVE expo on your radio setup.

Bruiser-RCU

My Feedback: (1)

I remember reading on RC Online (back when there was only them) that the CG is actually too far back. I think the person recommended moving the CG range an inch forward from where it was shown on the plans. He said that it actually made the airplane flyable.

Hope this helps,
-Bob George

heavy date-RCU

This is the first I have ever heard of this. Mine flys great. A bit bouncy on landing, but most of that is my fault. Never ever had a tip stall or any of the other problems you mention. 2 other guys in my club have them and they have never had trouble either.
I don't know what the trouble could be, unless the wing is really warped.
Like to know what you find out.
Hans

Edwin

My Feedback: (2)

Yep! Sounds like a GP Decathalon. Had all those problems too. My major problem was being my 4th plane, I wasnt ready for it. I thought, high wing, no problem, good trainer. WRONG!! Actually its been tamed and flys great, I love it. I had to take the control throws down to ail- ~1/4" u/d, elev- ~1/4" u/d, and rudder - ~3/16 l/r to tame it in the beginning. That made it controllable. All the incedences are setup per plans. The gear was my problem on ground handling. Over several flights, the gear would spread a bit. Thats when the ground looping got its worst. After just squeezing them back, it was fine. Toe-in helped too. The throws mentioned above get you going until you get comfortable with it. No radical aerobatics, just standard stuff, but still lots of fun. Once you loosen up the throws, this plane can give you a pretty high pucker factor. Mines about 8 yrs old with about 80 or so flights on it. Its down for a recovering job right now and replacing the nyrods with push rods. The nyrods developed some slop and dont center very good anymore. I would recomend using steel rod in tube.

Warning, it spins real good. If too much elev, it will snap at the top of a loop and go into an evil spin thats hard to handle if your not familiar with spins in general.

Start low throws, you'll love it once you've mastered it.
Edwin

thejetman

My Feedback: (1)

Hi all and thanks for all the input to my problem. I have decided to go ahead and repair the plane and try it again. I put all the parameters into the realflight program for the Decathalon. Moved the CG around and amazingly it did exactly what the real plane did with the CG moved back too far. I agree with the CG being incorrect on the plans. I contacted Great Planes about the problem and below is their responce...
Hello

Thank you for your recent e-mail.

Unfortunately, we are not aware of any poor handling characteristics with
this plane. If you could relay any more information on the building of the plane, we could try to analyze any possible problems.

I hope you find this information helpful. Should you have any further questions or concerns, please do not hesitate to contact us at this email address. (Please be sure to copy all previous emails into any future questions.) You can also reach our product support technical team at 217-398-8970, or via fax at 217-398-7721.

DID YOU KNOW that our web pages now all contain FAQs? (Frequently asked questions) Please drop by and take a look! We hope you'll find the information helpful and valuable to you.

Sincerely,
Tom
Product Support

Thanks again. I will post how the plane does on the next flight.
Keven

LuvBipes

My Feedback: (4)

They WOULD say that, wouldn't they.....?

thejetman

My Feedback: (1)

By making the CG about 1 inch further forward than the plans called for. The plane took of nice, I turned and started to gain alttitude, the engine died and I turned the nose into the wind and the plane winged over and started to spiral down I could not pull it out and it went in hard nose first. The plane is not worth fixing(for the fourth time). At least the Decathalon did not kick my butt. I did manage to fly it for a few seconds till the engine stopped.
I really do not think that I will ever build or fly another Decathalon. There are too many planes out there that fly great and are easier to build.
Thanks again for all your ideas on the plane.
Keven

Bruiser-RCU

My Feedback: (1)

Man, that really bites. Sorry to hear about the crash. I can picture what happened, cause I've had it happen to me. Engine die on take-off, an abrupt turn to get it back over the runway, then the tip stall, then the splinters followed.

I hear not all Decathlons/Citabrias are bad--just the Great Planes and Sig. The DynaFlite Super Decathlon and the Midwest Citabria are reported to fly very nice.

I am finishing up a DynaFlite now and it should be ready to fly by the end of July. I hope I haven't heard wrong...

-Bob George

gr8tfly

Well, I don't have any experience with the scale version, but I've >600hrs in a 1:1 8KCAB Super Decathlon. I also don't have a feel for your r/c flying experience, but it sounded like your were trying to "pull" it out. If that means holding up elevator, that's going to just aggravate the stall. Then, if you add opposite aileron (while stalled or near stall), any adverse yaw from the low wing will cause it to yaw in that direction, slowing the wing and deepening the stall of that wing - re: start of a spin. Another note: if the model has a symmetrical or semi-symmetrical wing, it will stall at a higher speed.

So - if it's slow and a wing starts dropping, lower the nose FIRST, then try and correct the roll. Maybe this will help, if you decide to rebuild again.

My wife and I flew IAC intermediate catagory with our Decathlon - it's quite a capable plane! I'm looking fwd to building a scale version, someday, but right now, I'm practicing on my WM P-51 (40 size) and will be starting on a DP Extra 330, soon.

Edwin

My Feedback: (2)

gr8tfly,
Do you have a picture of your full scale decathalon? I'm about to recover mine and would like some ideas
Edwin

gr8tfly

I'll see if I can find some. It's the standard star-burst pattern, but using yellow-orange-red scheme. You can see the striped bottom of the wing and the colors in my avatar.

LuvBipes

My Feedback: (4)

If you like the look of the Decathlon, check out Midwest's Citabria. Mine has well over 100 trouble-free flights on it powered by a 91 four-stroke engine. It is IMAA legal, will perform all the stunts you'd like, and it is easy to take-off and land.

For a full review I wrote a couple of years ago, go to: http://webpages.charter.net/rcfu/Kit...WCitabria.html

Edwin

My Feedback: (2)

Mine is currently read and yellow starburst in moneycote. I'm switching to a frabric covering and was looking for some different ideas.
Edwin

hag

My Feedback: (2)

My GP Decathlon 40 behaves just like yours. I have had to reduce elevator throw and washout the wings to make it fly more or less to my liking. I would have expected an airplane this size to be a better flyer. My clipped wing Goldberg Cub was similar in size, weight and wing area, and didn't have any tip stall tendancy. I have flown a Sig Citabria, which likewise flew well.

You have to remember that just because a guy can work a CAD program and design model airplanes doesn't make him Sid Axelrod, Carl Goldberg or Ken Willard. Those guys never would have released a kit like this.

If you read the "Flying" portion of the Decathlon instruction book (pg 40) you can get an idea of how the test flights went. Reading between the lines, it seems as though they weren't quite happy with the flight characteristics either, especially the landing behavior.

Here's a quote from the book. See if you agree:

"LANDING: Because the Super Decathlon has a lot of aerodynamic drag, it will slow down more quickly than you might expect when you cut the throttle for landing. Therefore, try to maintain at least a high idle during the landing approach to avoid inadvertantly losing flying speed. Also, because of the high drag, it is not necessary to flare to a high angle of attack to reduce speed just before touchdown. If it starts to get mushy, get off that up-elevator! As a rule of thumb (for this type airplane only) if the airplane looks like it is level, it is probably flared about right for landing......."

It sounds as though they think they have invented the high wing aerobatic tail dragger. Notwithstanding their "standard corporate answer" ("...not aware of any poor handling characteristics...") it's rather obvious that they are being less than honest.

TH

MacAir

Jetman,

This is the first post I've done on this site, and I registered here just to respond to you.

I am interested in buying/building either a Great Planes or Dynaflite "Super Decathlon" and saw your post that you posted on 06-18-2002.

In response to your problem(s) taking off and crashing, my thought is this:
1) While I have no experience in flying R/C models, I do have years of experience scanning.

As I read through your post, I see that you changed the building (scale) size by scanning.

During my time scanning photographs, negatives and slides, I have also scanned artwork - as I am an artist by trade (commercial art/graphic design)...
I have not yet been able to scan (and copy), " a perfect circle".

By this I mean that while the circle is a circle, for my use of reproduction, it is not exact (due to the source) and measures slightly off, or oblong. Not enough to worry about in some cases, but as I think the building plans of your model Super Decathlon are layed out, I feel that this may be (in part or whole) the cause of your problem(s).

If the plans are drawn in both vertical and horizontal, then scanning them (together) would cause these effects:
(a): The fusalage would be stretched...
(b): The wings would be shortened (or in reverse order):
(a): The fusalage would be shorter...
(b): The wings would be stretched (longer).

This is just my thought and opinion. This amount of difference maybe small, but I think it would matter more depending on the layout of the plotted plan or blueprint.

---------- I have also read that: ----------

In order to prevent tip stalls, minor modifications must be made (depending on the size of engine used). Sorry, no link, but I'll try to find it if you haven't seen it or done it already.

Just my 2¢

BigSkyRCFlyer

My Feedback: (36)

Hello all!
I am new here, and Just finished a Great Planes Super Decathlon, boy I wish I would have found RCU, before I built this plane. I have set it up per the plans, and all your advise on this kit. I have an O.S. .50 up front, with pitts. The kit went together ok, but the decals were not too good, did any one else have the problem of the star burst white not matching the covering color? I still put them on, but will fix it later after I know it flies.....LOL I did not add the wheel pants, our field is rough.
I am going to be flying it in the next few days, I'll write about the first flights, and hope I don't post in the CRASH Section! I really like the looks of the Decathlon, and was looking at the Giant Dynaflite, hope all goes well! I better get with it, we have snow here already, but I fly year round. What a great hobby!!!
BTW this is a great Forum!!!

Here is a few pics:

BigSkyRCFlyer

My Feedback: (36)

Number 2

MacAir

BigSkyRC'er,

That looks great! I'm unsure which Super Decathlon or Citabria I want, I think ultimately I'll go with a Carl Goldberg or a Dynaflite, but there are so many versions to choose from it makes it a little hard to select.

I want mine as a third plane, one I know I won't crash. I really like the looks of them and want it more/less as an accurate "scale" model. THe more accurate in appearance, the better.

I hope more people post (upload) their images of this model airplane... they're classic, and schweeeet!

Thanks again for the pics.

MacAir

PeterH

If anyone reading this thread has an interest in obtaining a completely built and finished Sig Citabria (Koverall, painted in kit striped scheme, but cream/maroon) that needs only a receiver/switch/battery to fly, please contact me offline. I have no digital pictures, but can obtain some relatively easily. The airplane, as it sits, has 4 ballbearing-converted S-148 servos installed, a new, never run OS .61 4-stroke, fiberglass cowling, tru-turn spinner. I'll answer specific questions if they are asked.

Thanks very much.

BigSkyRCFlyer

My Feedback: (36)

The Great Planes Super Decathlon Flies Great! It is definitely not a good second plane, though. Mine does not exhibit any of the really bad characteristics some people have written about. I.E. Tip Stalling, etc. I set it up per the plans, and did build in some washout, about 2 degrees, control throws as plans said also, I did slow down the Elevator. That's about it. It balanced right on the money with the O.S. .50 SX , but I did add an extra oz in the nose.

Flying: The Ground handling is TERRIBLE! You have to advance the throttle slow and smooth and you can keep her straight. I did notice it does like to dip the right wing-tip a bit after you rotate, but not too bad, nothing out of control. It slows down quick on approach, and the controls get a bit mushy, but no tip stalling on mine, it actually is fun to land! It does like to spin nice, and put her through some smooth manuevers, she really does nice.


I am so happy, I love this Plane the looks are outstanding on low-bys! I am now looking forward to the Dynaflite!

EBHolmes

After reading all of the bad press about the poor flying qualities of the GP Super Decathlon 40, I was concerned about flying mine. I did not build in washout (though I think it's a good idea). However, set up per the instructions, mine flew great. It is a handful on the ground before the tail starts flying, and I think that leads a lot of pilots to rush to get the plane into the air. Insufficient airspeed, too much elevator and and aft CG are a deadly combination.
Mine is powered by an O.S. 70 Surpass and weighs about 7 lbs. I covered it with 20th century fabric and painted it with Nelson paints. Low fly-bys with the 4-stroke look and sound great. The handling qualities in flight are more docile than I expected. Landings are no problem.

adrian-RCU

ouch, we have a tt super decathlon,had similar problems for first 3 crashes then checked the cg moved as above , it started to behave and actually fly. not so good , took it back to the workshop and started to check everything ,discovered an unbalanced wing . fixed all now flies great and we enjoy its marvelous rolls and real plane looks,

scale buff

My Feedback: (24)

I feel that I have to add my two cents worth on this. I built the GP Super Decathlon several years ago, and it was probably the sweetest flying airplane I have built in 27 years of modeling. I sold it, wished I hadn't and just recently bought a kit on RCU. I really don't know what could have caused the other guys problems because I built it according to the plans and had absolutely no problems. Wish I could help, but wanted to write because I don't think the kit deserves a bad rap.

Frank T.

BigSkyRCFlyer

My Feedback: (36)

I have to Agree with Frank T. I was worried about flying my GP Super Decathlon, I now have over 30 + flights on it, and it is one of the best flying planes I have. I built and Set it up per plans. I am thinking about buying another kit to have around. I would say the ABS Cowl is Crap, Mine has already cracked bad. That's ok with me, now I can get a Fiberglass one!!
I hope more people have better luck with this Plane, She flies great for me!