Hi,
I'm new to this board but not new to r/c. I have several planes, and I'm an experienced flyer, but I have one plane that just won't fly right, my Great Planes Slow Poke.
I tried a bunch of things with this plane, changing the cg, moving the engine forward, etc...but it still flies terrible.
The way it flies is as if it wants to tip about its' cg and either dive or stall...very strange.

I'm thinking that it is something about the wing. Maybe the covering on the wing top ends? Maybe the leading edge of the wing should be sharper? Maybe something else?

I'm including links to some pics I took of the wing. If anyone can see anything drastically wrong, please point out the problem for me. I was really hoping to have a nice slow park flier with this plane but it won't fly well at all.

Could the big foam wheels be causing too much drag? They are recommended in the plans.

Thanks in advance,
John C.

http://home.comcast.net/~jcchaplain/wing1.jpg

http://home.comcast.net/~jcchaplain/wing2.jpg

http://home.comcast.net/~jcchaplain/wing3.jpg

http://home.comcast.net/~jcchaplain/wing4.jpg



P.S. I hope this was ok to post in the aerodynamics group. I figure it is an aerodynamic problem?

Oh, another point to make about this kit. It says the the plane may require 8-10 oz of noseweight!!!!!! Does it make any sense that a correctly designed plane should require that much nose weight? If I had thought about it I probably wouldn't have bought a plane that is designed like that in the first place. Not sure if I should just leave it hanging on the ceiling of my workshop for decoration or try to do anything more with it.

John C.

I do not know to much about this plane and it's wing,it looks to be a flat bottom one,if it is it would have a lot of lift. Have you tried to change the thrust angle? Just a thought.

Please realize that the amount of ballast needed to bring a plane into balance is not relevant as long as the model's gross weight is not out of line. The Great Planes Slow Poke has a very short nose. That means that it WILL take quite a bit of weight to balance it. OK, you do what's necessary. The .25-size Slow Poke should max out at about 3.5 pounds, and the .40-size at 6.5 pounds. Stay within those parameters and you'll be OK.

A "correctly-designed" airframe may or may not need a certain amount of weight to balance. Many people have the mistaken idea that a "correctly-designed" model should need no weight or very little. That's not so. It all depends upon what the model is designed to do. I had a large glider that required several POUNDS of weight in the nose to get it to balance properly. The gross weight of the glider was below the designed gross weight, so I had no concerns at all about adding weight to balance it. The Slow Poke's design is intended to be a fun model with a very large wing...it's a floater-type, and the intended "look" of the airplane gave it a rather short nose. It's not at all surprising that it may need more weight than some people may think it "should" have. Just balance it where suggested and be done with it. Again, as long as it's within the design parameters for total all-up weight, what you have to add is not relevant.

Hi All.....

Another new B. Just joined today. Well I picked up a used Slow Poke from a local hobby Shop. It is the smaller 3 channel one. The first thing I did was strip off the covering and CA everything again. Then cut the wing making the ship a 4 channel machine. When I removed the covering, I also removed a bunch of Lead from the front end. The origional owner used a 25 two stroke. I am going to use a 52, 4-stroke. I had to rebuild the front end to get it in. The bigger motor should balance the bird OK. I am about 60% complete. I will discuss it further after I fly it. Jim Toth

No, I never did try to adjust the thrust angle. I don't think that should have a dramatic effect. The plane flies REALLY bad. I'm thinking maybe the wing tip form or the leading edge of the wing is too blunt. I thought this plane was supposed to fly slow and easy...but it doesn't.

I dismissed the idea of a bad thrust angle but I think I should reconsider that. Also, does anyone think that the height of the cg on a below wing plane is critical?

John C

I'll be very interested to hear how your Slow Poke flies. I have a little .15 OS engine on mine. It has plenty of power to get right in the air, but it just flies like crap and I don't know why.

What is the recommended CG location? Where have you had it when it was flown?

What engine is recommended and what are you using? what prop?

I wouldn't worry about the leading edge shape. One of our regular fliers at the club field builds his own planes. On his last one, he didn't shape the LE pieces. They came as 1/2" square sticks in the kit and that's how they were when he covered them. It's a Butterfly. They have a very large glider like, polyhedral wing with a LOT of LE. It flies way better than anyone would imagine.

I'm not sure what your question is about the covering on the top ends. You've got a couple of pictures that seem to show some wrinkling in the covering in the last open bay. That can be removed with heat. It shouldn't be significant from what I can tell from your photos.

The design of the airplane uses a low aspect ratio wing. Their characteristic is that they are pitch sensitive in that when pitched a certain amount they create appreciably more drag than would be induced by a wing of higher aspect ratio of similar area. What that means to you and that Slow Poke, is that it will probably appear to be elevator sensitive. Much pitch change and the sucker is going to slow down.

A couple of us experimented with wings of about that aspect ratio back in the 60-70 in control line combat. The lower aspect ratio wings were lousy in fast combat because their speed was killed every time we tried to turn them. They felt and looked like they were stalling (they weren't) and the engines had a real problem getting them back to speed. The perception of what they were doing in flight could have been the same perception you're getting.

The parallel between those combat wings and your Slow Poke could be that the Slow Poke actually has marginal power for the design. The design is going to give huge drag at times. The engine isn't going to be a powerhouse. The power loading is going to be on the low side for the drag the airplane can throw at it. 15s are not big prop turners. They turn little props fast. That's a recipe that works well for little fast airplanes.

I'd lean toward trying to put as much fan in front of that plane as possible. Larger diameter prop with flatter pitch would be the idea. To swing that, you might look around for a bigger engine. Or simply try the largest diameter, flatter pitch props suggested for 15s.

Next thing to do, and it could be the most important, would be to limit your elevator throw. That wing is going to give you most of it's best performance in a fairly narrow range of Angle Of Attacks. You're not going to need an elevator with more throw than what's needed to get that range of AOA. It's possible that the available elevator movement is getting that little prop on a little engine on the front of a very pitch sensitive wing is the cause of your problems.

The pictures you've provided are helpful. On the other hand, you might take one from directly behind the wing. Line the TE up so that you see the least amount of wing ahead of it. Then study the picture looking for warps.

As for the wheels........ Square shouldered wheels do cause more drag than "normal" shaped ones. But wheels are never going to cause enough drag to be a significant problem.

I have a friend who built a Slow Poke. He too thought that it was going to be good slow flyer. He says it sucks and hasn't flown it as long as I've known him. He says he'd take it to a swap meet to unload it except for one thing. He knows it would only be bought by someone without too much experience, and he doesn't want to screw a beginner.

Some models have less than aerodynamic design criteria. There is one "design" out there whose major purpose is possibly a joke. It's made of what is literally nothing more than construction site junk. It's fuselage is drain pipe downspout. Another one's fuselage is a piece of lawn furniture. They fly pretty much like junk. I've seen a number of them fly. That's about all they do. I've seen one hardheaded "believer" of the concept who brings his out time and time again. I've never seen him take the junk home in one piece. They've accomplished what was probably the only design criteria. They can take off before they crash. So "they fly".

The Slow Poke is a cute looking thing isn't it. It appears that was the design criteria. Maybe all of it. But then, I've never built one. So take my advice with that understanding.

At least I offer a guarantee.........
If you're not entirely satisfied, there will be no additional charge.

If an airplane is not stable about the pitch axis, then the balance point is too far aft. Also, you may have just too much elevator movement. When properly set up, the Slow Poke series of airplanes should be able to nicely "putt-putt" about the sky with gentle, low-stress flight. If they won't hold pitch, then they're just too tail heavy, and you'll need a bit more weight to balance the model.

Please remember that the balance point (and balance range) shown in the plans are starting points. There is nothing wrong with your having to move it wherever it needs to be moved to get the flight characteristics you desire. To our mind, it sounds like your model still needs to balance farther forward. A way to check would be to put the model into a 45-degree dive. Hold it in that line for a few seconds and then release the sticks. You want the model to pull up smoothly. If it does not, then you'll want to add more weight to the nose. If it pulls up very abruptly, then there's too much weight in the nose, but it doesn't sound like that's the difficulty.

Other things that may make the model not hold a pitch setting would be stiff controls that do not properly return to center when you release the sticks, mis-aligned surfaces, something loose, flexing control linkages, and so on. Everything needs to be checked. After checking the balance, if the model's very sensitive around the pitch axis and still won't hold a pitch setting, we'd look for too much control throw and a lack of positive centering.

FWIW

I have seen RCKen's SlowPoke with an OS .52 fourstroke fly and it looks good. Low slow loops, touch and goes, all are very stable looking. Maybe Ken can chime in with some insight.

It would be good to hear from Ken. The fact that his will do slow loops suggests most strongly that his has enough power to fly that wing. Try to fly a low aspect ratio wing with too little power and you don't see many slow loops. There is a great difference between light wing loading and the adequate power to pull "extra" drag and weight.

Also, if his has a .52FS in the nose, there is a good chance that his balanced easier during construction, and no question that his wasn't tail heavy.

Thanks for all the feedback. I did try about 20 flight with this plane, changing nose weight from very little to way too much and everything in-between. It never flew well enough to be able to even say it flew with any stability. It crashed several times and I did manage to land it safely several times, but thats about it. Every time I flew it it seemed to rock around the cg terribly. Give it some throttle and it would nose up, cut the gas and it would nose down. That almost sounds like the cg is back too far doesn't it? But that is not the case. So...I don't know if it is worth any more time.
I was thinking of putting floats on it and a bigger engine. Maybe with the weight of floats underneath it would fly with more stability? ( like an above wing plane does due to the hanging weight?)

jchaplain, I've read your post and I think you might need more down thrust.
If the plane climbs under power and dives on glide that usually means downthrust is needed.

You might also have an incidence problem.The plane shouldn't dive on its own.
If you don't have an incidence guage,let me know, I'm not to far from you,you can borrow mine.
I would like to know where you fly. I'd like to see it for myself.
PM me if you would like some help.
Paul

I flew a buddy's SLow Poke that was built from the original RCM plan. I believe the Great Planes version is quite faithful to the original.

It's a HORRIBLE design. The model uses a thick, flat bottom and highly cambered airfoil to presumably enhance the slow speed side of the flight envelope. But while it uses a rather large stabilizer the tail moment is extremely short and the wing chord very wide. Combined with the high pitching torque of that thick highly cambered airfoil and you have a great recipe for very odd pitching problems despite the large stabilizer.

The model was fine as long as the speed was kept very low like in the climb or if you throttle way back and fly slow. But just try to throttle up or dive for a bit of speed to do some aerobatics and all heck breaks loose as the strong pitching moment of that airfoil overpowers the stabilizing force of the stabilizer (is that repititious or what? ) The result is a tucking of the nose and the need for a fast and judicious addition of up elevator to bring the nose back up.

The model is cute but that's where its appeal ends as far as I'm concerned. What it needs to make it into a successful design is a change in the airfoil to a pitch stable flying wing airfoil or at least a change to an airfoil that is more pitch neutral like some of the 5 digit NACA ones.

An option to try to salvage an otherwise unwanted Slo Poke would be to strip the wing and cut away the trailing edge about 15% in from the rear and angle it up by about 4 to 5% of the chord to add some reflex. This would greatly reduce the workload of the overpowered stabilizer and may make it a model that you suddenly become happy to own.

Also ensuring that the balance point is up somewhere around the 25% mark would help a lot as well. But no CG shift or thrust line adjustment will make up for the Big Basic Boo Boo of this design. It needs serious surgery. However as pointed out to me by a Slow Poke flier he got used to it and just expected to work the throttle and elevator a lot and be ready to catch it if the speed comes up.

But if I were to build one I'd just go for a better airfoil choice.

John C,

I know that this thread is seven months old now and hopefully, you haven't dropped your Slow Poke in a dumpster by now! Anyway, I'd like to add my two cents in an attempt to try to solve your Poke's problem. The first thing that comes to mind is the engine's thrust line because the first year's run of the model had some issues with that. This link addresses that problem:

http://www.greatplanes.com/techsuppo...a0491tech.html

The GP Slow Poke seems to (generally) be a well behaved plane. Many have been built and many builders have been happy with theirs. Great Planes has been offering this plane for several years now and it is still in production. It seems to me that if your plane's performance is representative of the Slow Poke design, it wouldn't be as popular as it is and Great Planes would have canned it by now. In my experience, it is not like GP to continue producing a plane that flies as poorly as yours. Therefore, the problem is likely to be with your particular plane and not the Slow Poke design as others have suggested. Check your motor mount to see if yours was constructed incorrectly and let us know what you find out.

I've had a 40 size Slow Poke ARF ever since they came out. I have an OS 52 on it. It has always flown great from the beginning with no changes.

I also had one exactly like W8ye did and it too flew beaufitully until another radio was turned on and killed it. Was pretty much my favorite relaxation plane! Had an old Enya.46 4-stroke then an OS.48 on it. Was a floater and a touch and go King!

The only thing not discussed here would be to go back and insure there is no flex or stifness in the elevator control. This would include everything from the servo centering to the control horn on the elevator. I have not owned one but have seen them fly.

I have this 25 size plane built from a kit. Go to Towerhobbies.com look up this kit then read the REVIEW. Just as I found out the hard way 1. A 15 engine IS NOT ENOUGH,a 25 is barely enough. 2. They and I and anyone else with recomended engine size has had to add a MINIMUM of 10 oz to balance. Plane flies even better with more weight(nose heavy) 3.I and another flyer in my club use 40 size engines,less lead to add,plane flys great and your left thumb will allow you to fly this plane as slow as you can walk backwards.