Great! Good luck!

regarding a ground handlig.. yes.. Decathlon is very ugly Especially with bigger engines. I gently crashed it in first flight with bigger engine.
Once airborne it was like a rocket. I loved a low, hi-speed passes then vertical climbout Landings are really easy.

Glad to help Jim

One more thing...

The wing tips are shaped balsa, which are only about 1/4" thick. This is a rather weak point where the ailerons begin, should you have a minor mishap. You might add some thin plywood at the rear of the tip to add strength. I had to repair mine at that point just from hangar rash.

Pilgrim

One more thing...

The wing tips are shaped balsa, which are only about 1/4" thick. This is a rather weak point where the ailerons begin, should you have a minor mishap. You might add some thin plywood at the rear of the tip to add strength. I had to repair mine at that point just from hangar rash.

Pilgrim

Thanks FlyingPilgrim and all of you guys for your assistance. I expect the kit to be here next Wednesday. I hope to get started right away. I would love to see pics of your Decathlon.

Jim V

nice thread, i am downloading the video now.

I have had my GP Decathlon completed for 2 years, but i have not flown it yet because i am afraid of it. I have only flown a Duraplane which i have pretty much mastered but i still won't fly the decathlon. I am sure it would be fine but i am going to build a fly a sig 4*40 for next summer and fly that first, maybe by the end of next summer i will try mine out.

Well, guys, it finally arrived today. GP Super Decathlon kit # DF40. It is in pristine shape. Had the original catalog of GP kits in the box dated 1991. I haven't taken all the stuff out of the box. I just briefly looked in it. I did see a ABS cowl and pants. The wood looks great, all the hardware is in the original unopened package. I am so proud of it. I want to contine to buy kits as I go along. I will look on E-Bay every day.

I need to build my work-surface. I think I am going to get a 36" solid core door and overlay it with 1/2 " sheet rock, and maybe a sheet of that 1/2" foam insul board they use on houses for exterior insulation. Mount that on some sturdy saw horses. I want a flat, straight surface.

I have read all of the posts in this thread, and I just glanced at the manual. I am going to read it thoroughly over the next few days. I have not unrolled the plans, but will soon. I am going to be asking you pro's questions,
please don't get impatient with me. I will posts pictures of my progress, when I begin. Gosh, a 60 year old so excited. I can't believe it.

Jim V

Hello; I have a Decathlon which I flew with a Surpass 70. We had a terrible time getting this plane flight ready, the local plane gurus proclaimed thatr the wing incidence was wrong, as it was so sqirrely in the air and couldn't be slowed down with out snapping. I tried and tried to fly it like the instructions say but it just wouldn't settle down. We moved the wing dowells down and increased teh wing incidence and shimmed up the gap between the wing and the fuselage and it calmed right down. Now I should say that by the time we did that teh fuse had ben rebuilt a few times and was starting to get a bit heavy, I had knocked the tips off the elevators and the rudder with various landing attempts. It was starting to look pretty ugly too as I had re-covered it after each repair. By the time I had it flying like I think it should fly, it looked terrible. I was embarrassed to bring it out. The landing gear had been straightened so many times it was breaking from metal fatigue. I decided to just hang it up and write it down to experience. Quite a dissappointment after many successes with other Great Planes Models. I just recently took the servos out of it for another project (a pizza box Spad)

Safebet, good luck with building the Decathlon. I think you will not have many problems. It was the first kit I built and I didn't. The instuctions are very good. The only thing that I want to add to all that is posted here is that, if you haven't already, read the following suggestion from GP:

http://www.greatplanes.com/techsuppo...a0185tech.html

I think they changed the manual sometime to include the washout, I don't know which one you have. I didn't built any washout because I had an old manual and by the time I read the note it was too late.

Now, about donkey doctor's post. I have read simmilar comments from many about this plane. I really cannot help you with that. I know that they are all telling the truth, but I really can't tell why it didn't happen to me. The only thing I know is that mine flew great. It was my first kit built, so I don't think I build very well. I know for I fact that I build heavy, because I use too much glue (I have not seen anyone build a kit, so I cannot tell how much is enough and I prefer too much than not enough). I had not flown for a few years and have never flown another tail dragger before, so trust me when I tell you that it is not my flying skills either. If you look at the video I posted, you'll see that I didn't have any serious problems, except bouncy landing, which I'm sure I'll get better, especially with the stonger landing gear I've ordered and still waiting for.

Again, good luck with building it. And ask as many questions as you want. I built it just a couple of months ago, so it's all fresh for me!

brschmid, good luck with yours too. Take your time, fly it when you feel ready, but don't be afraid of it. I know I was, but it turned out to be anything but.

Serafim

Thanks SERAFIM and donkey doctor for your comments. I will not be flying this plane for sometime because I haven't really got to fly my trainer's, yet due to the unfortunate mid-air on my first trip out. I read the manual and it does not mention "Washout" at all. There is, however some diehedral built into the wing. I am strongly tempted to forget about the "Washout" because it is just another step for opportunity for error. I have heard some say you need the "Washout" to build in stability, and others say they have had no problems without it.

The manual is very straight forward and the pictures are good. I have not yet unrolled the plans. I am going to take them to a print shop tomorrow and have two additional sets made. 1 for spare and 1 to send to another R/C'er in a foreign country who needs a set.

I did notice that the manual mentions sharpening a 1/8" dia. piece of brass to cut or gouge out grooves for the torque rod and tailgear wire. Know where I can buy the brass tubing?

You both mention the landing gear as being weak and bends easily. I looked at it and it looks strong, but it is aluminum and maybe is not a stiff enough grade. SERAFIM, you mention ordering a stronger one, where?

Also, I was wondering what you all thing of Evolution engines. Both of my trainers have .61's and they run nicely out of the box. I was thinking of ordering a .46 NT (12,500 RPM, dual bearing) running a 11 x 6 prop. What are your thoughts on this selection? I know I would have to replace the existing muffler with something that would adapt to the cowling. I guess I'll see if that's possible before I make a decision. I would appreciate your suggestions. I am not made of money, but I would spend a little extra for the right combination. The Evolution .46 is $90.00 at Horizion Hobby.

Safebet, this is what I ordered:

http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXNM65

I did it after a suggestion of Edwin on this thread. It has not arrived yet so I cannot tell you how well it fits or works. I will get back to you on that.

As far as brass tubing is concerned, I used an old brass tube from a fuel tank I had. The manual also suggests use a larder diameter brass tubing for the pushrod exits, but since I had none I used by drill. I think the brass tube would do a neater job. I hope somebody else will let you know where to get it, since I'm like 10 billion miles away

I have no experience with the particular engine you mention, I just know that after flying with the .46 LA I know it is on the weak end of the range for this plane. Others suggest even .60 engines.

Serafim

I'm not a fan of Evolution engines. They're ok as an entry level engine for beginners. I tell my students to go for better quality engines if they decide to get more serious about flying. I see them wear out and on a rare occasion fail. Once you have 4 or 5 tanks of fuel thru them I throw away the blue restrictors on the high and low speed needles and dial it in. Those are there mostly to keep beginners from getting out of control when adjusting. Use engines that are popular in your area. Here at home its Super Tiger, OS, Thunder Tiger for the higher end. Some Magnum engines are ok. You just have to look around for what works in your area and for people that know how to dial them in perfect.
Edwin

Thanks, guys, for the replies and the helpful suggestions and opinions. I will seriously consider them all. Edwin, you mentioned that a .60 might be better. More power if needed. From the threads I've read it might be nice to have it, especially on landings, especially if you caught yourself a little low or slow. I don't have a problem tuning these engines. I own a small engine repair shop and I am very familiar with 2 cycle engines. I, also, never tune one without a tach. I am a tach tuner, deluxe. Edwin, I live in Diana, north of Longview, Texas about 10 miles. Where is Leander, Texas?

Serafim, Thanks for the link and the tip on the larger brass tubing for the pushrods. I will locate some somewhere. I noticed neither of you touched on "Wash Out." I guess this is something I am just going to have to decide for myself. Tip stalling, I understand is a result of loss of lift, beginning first at the root of the wing, and continuing outward until the wing stalls. I would guess, (novice guess) that this is a result of a high angle of attack or loss of forward momentum, or a combination of both. To overcome, I would think, you just need to remember that it drops like a rock when you cut the throttle, come in somewhat hot, and use elevator in small increments. Oh well, I will learn some of this stuff somewhere down the pike. I will fly that trainer a long time before I risk trashing this GP. I will seek a qualified instructor to buddy box with me on it when the time comes. I hate failure. Most failure is caused by pride and stupidity.

Thanks, again, both of you.

Jim Vines Jr.
Diana, Texas

Hi Safebet,
Leander is just west of Austin. I fly and instruct in Georgetown (GAMA) and fly my big birds in East Austin at (ARCA).

As for washout, mine doesnt have it. BUT, I would highly recomend it. About 3deg or so should do, I dont know what the addendum says but I would follow that.
Edwin

Safebet, I would also suggest the washout, even if I don't have it in mine. If I knew before I built it I whould build it with washout.

Also, just for you to know the theory, tip stalling is the opposite of what you described. The tip of the wing stalls first, and that is why it drops. That happens on takeoff because the middle section of the wing has air flowing around it from the prop, so even if the center of the wing has enough 'air speed' to fly, the tips don't. So if you take off too soon, one wind tip will drop because it is stalled. That is why most owners of this plane say that it ground loops immediately after takeoff.

Serafim

Thank you , both for your input and correcting me on the causes of Tip Stall. I will probably install after wing is completed, but before I cover.

Now I just have to find a place to build in. My wife says I can't use the spare bedroom. May just have to enclose HER carport, ha, ha.

Jim V.

Safebet:
I have this plane and have been flying it for over 2 years. I have heard a lot of discussion about washout and tip stall, and in fact, I was bit by the tip stall bug once. I ended up needing to rebuild.

With that said I don't have washout in mine and don't want it. You should evaluate what you want your plane to be and how you expect it to fly. Do you want a full-blown aerobatic machine that will knife edge and fly inverted? How about snap rolls? If the answer is yes, then leave out the washout. In order to snap roll you need to induce a tip stall and washout will fight that. It will also cause bias in inverted and knife edge flight. If on the contrary, you want a gentle airplane with a more predictable stall then add the washout.

It's really as simple as that. You gain some things with the washout and you loose others.

Thanks Ksechler:

I will take your comments under consideration. I really want this plane to fly as it was intended and designed. Although I will not be able to fly it until I get some time on the clock with my trainer and maybe a second plane, at some point, I want to know that I have a real aerobatic plane in my stall and it will be limited only by my ability as a pilot. If I crash and burn, having done my best, then that's ok. I will take note of my mistake(s) walk away and build another.

Thanks, again

Jim Vines Jr.

I noticed in reading the GP item, it mentioned "most problems occurred with those planes using a .70 4 stroke. So, for sure I won't use a .70 4 stroke.

What engines and servos are you guys using?

I used a OS.46FX with a 11x5 MA prop. Seemed ok to me.
Edwin

I used standard Futaba servos (3003?). Not to beat a dead horse, but make sure you look at Great Planes tech notice regarding the washout. I recommend it. Those that have not added washout seem to have more tip-stall problems, especially when they accidentally try to pull the plane up into the air before good speed is reached. Here it is:

http://www.greatplanes.com/techsuppo...a0185tech.html

Like I said, I was only able to achieve 1 degree of washout, not the recommended 2 degrees (only due to the wing being already built and quite rigid by design), but it worked fine. I was able to fly inverted and knife-edge without any problems. Since this is a high wing craft, it required full opposite aileron to hold knife-edge without rolling out. It has plenty of rudder authority.

You mentioned the effects of the 4-stroke in this plane, and I agree that it would probably be easier to handle with a 2-stroke just because they don't have the torque of a 4-stroke, which tends to want to twist the plane on take-off. I thought I could use a gentle touch on throttle and not have problems, but it is a handful. I don't think I would use a .60 engine due to weight. A good ball bearing .46 with a pitts muffler would be perfect.

Pilgrim

i have a TT pro 46 in my Decathlon and i had to tie it to the ground when i broke in my engine because at idle it wants to pull away, so it seems to be more than enough power for this plane.

I've seen so many posts over the years about tip stall problems with this plane and it is puzzling because the wing is not tapered and not high aspect ratio, and I'm sure it is a standard semi-symmetric airfoil. If you looked at the wing alone it is probably just like the wings of dozens of successful sport models. So it must be something else.

I think the something else is the stab. It looks extremely small. I suspect the stab actually stalls first, then quickly causes loss of control over the angle of attack and a wing tip stalls. I've been tempted to get one of these planes just to try to prove the point. I would measure the stab area and the tail moment and then use the standard formulas to see there is a problem. I bet there is. Then I would build a bigger stab according to the formula. Just as a guess, I suspect if the stab were increased 15 - 20% (increasing the area about 30 - 40%) the plane would be much nicer to fly.

Jim

Jim: I know nothing about aeordamics. Would you increase the size proportionally height and width

Well, I just stepped over aqnd looked at the plans. Height is out because the rudder extends over the top of the stabilizer.