Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Guys,
Anybody flying this plane and had to put lots of down trim in it ??
Before i flew mine, i noticed that the engine firewall has 2+ degrees of up thrust. I notified great planes and they said it is "designed in the airplane"......BULL!!! When i flew the plane ,it required 24 clicks of down trim to get it to fly level. (I checked stab and wings prior, with incidence meters, they are right at zero, balance is right on the money too). when i landed the plane, you can see the elevator drooped down. Well, another guy shows up at the field with exact same plane, and when he turned on the radio, you guessed it! The elevator drooped just like mine. I looked at his prop from the side, sure enough, it has upthrust like mine. I asked him if he is going to fix it, he said, naw, it flies okay. I guess, he is satisfied with mediocre performance!. I have a friend in Texas, and he said his Giles 202 is okay, but his friend has one and it is like mine, he had to add a lot of down trim.
Well, i put some shims behind mount and got the engine to 1/2 degree down thrust. I flew the plane and it still needed 10 clicks of digital down trim, but it handled much better! I now put two degrees of down thrust in engine, and will fly it monday. I will report my results monday night on here.
I would like to hear from anyone who has had to put in a lot of down trim in their Giles 202......Thanks Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

My friend is flying his tomorrow'i'lltake alook and see if his is like that.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Wildthing,
Do you know if this is his maiden flight on the plane?
If it is ,and it has up thrust like mine did, tell him to be aware that when the plane leaves the ground it might pitch up nose high, and stall. Mine did just that, and i had to shove the stick down hard to get it level.I was Lucky, that the enginge was pulling really nice and strong, being a gasser, it had the power range up, if it would have been a methanol two stroke, i don't think i would have been able to save it, as it would not have been at full power level. Thanks for replying, Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

He has a gollon thrue it at least but i remember when he first flew it the elevater trim was way off,never checked the upthrust but will warn him today.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Wildthing,
thanks for the reply, this does not seem to be an isolated problem ,with just my giles, as now i know of four planes that have had this problem.......And, i wonder if any one has crashed on take-off , because of this problem, that was not aware of the upthrust! it will be interesting if i get more replies on this. Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Well, i flew the bird again today, and still had to put 10 clicks of down trim in elevator, to get it to fly level. Came home and put in 3-1/2 degrees of down thrust in engine! went back to the field, and flew the bird once more. NO CHANGE! still needed 10 clicks of down to fly level.
I came to the conclusion that MORE down thrust is not the answer to the problem. I turned both ailerons down a half turn,and it helped quite a bit! I figured there must be something way off, or out of line. But the plane is now flying very well .
When i got home, i put four incidence meters on the plane(one on each wing tip, one on each elevator half) every surface was at ZERO! This is a mystery to me.If any one has any answers to this one, i sure would appreciate their input. (it's not a balance issue, as i double checked it ,and it is right on the money)
I put the engine back to 1-1/2 degrees down thrust. Set the elevators at 1/2 degree down ,and ailerons1/2 degree down.
I will fly it wednesday to see how this setup is working.
Thanks for reading this , Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Hey Paul,
Sorry to hear about all the problems. How is it if you roll inverted? Need any down stick? How about if you roll 90 degrees and do a pylon style turn, Nose pitch up? I'm wondering about the CG placement. All planes will need to be properly trimmed and the manual specs aren't always the best....
Rick

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Rick,
Thats whats puzzling,when i roll inverted, the plane is almost perfect, i do have to hold a fraction of down elevator. But if i remember , i had to do that in all my birds when i go inverted.
Roll rate is perfect too, even slow rolls are outstanding.
When i hang it knife edge, its also perfect, half throtle she just hangs all the way across the flite line, if i go full throtle, she will knife edge loop. I also chop throtle from full, and she doesn't fall or climb, when i go back to full throtle. I have not checked it for 90 turn then pull pylon turn, i will try that tomorrow.
Thanks a lot for your input.........Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Sounds to me like there is an incidence problem.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Outcast,
Thats what i suspect, i have checked everything and it is at ZERO. Since it is an ARF, there are no plans, and Great Planes has nothing on their site to say what it is supposed to be.
Thanks , Paul

Engine Thrust
 

I would check to see what the plane does when you go from full throttle to idle in flight. If the plane rises immediately after you remove throttle then you have too much down thrust. If the plane dives after you remove throttle then you have too much up thrust. This only applies after the plane has been trimmed for level flight.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Snothead
Thanks for your reply, i have done that several times. There is NO change, plane does not climb, or dive, when i chop power, then add full power. Thats why it is so hard to figure out what is wrong, and why i have to have down trim in it . It definitely was not right what great planes said, that plane requires 2degrees upthrust. I almost lost it when it left the ground , had to put lots of down trim in it

1 degree of upthrust
 

This may be a stupid question, but... did you build the wing upside down? i.e. Anhedral instead of diheadral?

I've been flying mine for a while. With the CG set at the rear of the specs and 1 degree of upthrust, it is totally neutral inverted or upright. But it is a real handful to land. Incidence is 0 degrees, right thrust is ~3-4 degrees (had to offset the engine to line up with the cowl). Weight is a touch under 12 lbs.

I moved the CG to the forward position. It is now a joy to fly. Takes a lot of expo to tame the elevator. Needs full rudder but with that it can do a knife edge loop. Tumbles like a leaf. Elevators, walls, et-al. no problem. Suprising stable for it's ability to tumble. I'm kind of diggin' it!

OS 160, Perry pump, 16x8
5ea 5925's
1ea 225
Jr1400
Futaba radio gear
YMMV.

Best of luck with yours,

Scott H.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Scott,
No, its an ARF so wing has angles already built in. Color is different on bottom of wing too.
The firewall has right thrust of about 3-4 degrees, which i'm not sure that it needs all that to begin with, as i had to put in a little left rudder trim , because it was turning right, just slightly.
CGis good, because it handles good,and lands like a ***** cat!
Thanks for your input, it is truly appreciated !

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Hey Scott,
How does yours run with the perry pump? I just bought one and a 24oz tank and I am undecided as to wether or not I should mount the tank at the CG or just leave it in the stock location. Also are you using a Pitts style muffler or the stock one? I have no Idea what all these changes are going to do to the fuel pressure....
RP

Paul,
If there is no change with chopping the power, then I don't think the thrust line is an issue. I know the 3D hotdoggers like a degree or two of upthrust actually for hanging on the prop. Not sure what the problem is with your plane. Maybe the wing incidence shouldn't be zero. If you do the long vertical dive does it belly in or out to the canopy, or is it straight down?
RP

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Rick,
I have not tried that test, but i will today.
What will that tell me?
lets say for example it pulls towards canopy, will that be a wing angle incidence problem?
Sorry i can't help on your tank question, as i have a MV VS gasser in my bird. Thanks for your input .......Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Hi Paul,
it's a way to check if the wing incidence is proper for a given model. Someone here gave me the link to the page with a nifty trim chart but I lost the link. It basically says that if the model pulls (in a straight dive - power off) to the canopy you should increase wing or stabe incidence. Pulls toward the belly then reduce wing or stab incidence.
I haven't tried this yet, but the rest of it seems logical enough.
Rick

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Rick,
Thanks for the info, i am anxious to see what it is going to do, in that test maneuver. Only problem will be if it pulls in either direction, how do you fix it since stab is now permanent, and wing saddle is not too easy to change because of its thick mass?
Guess i would have to set incidence in stab or ailerons slightly ,and be happy with that. like i said a little earlier,i have the stab and ailerons set a 1/2degree down , and i am going to see if that makes any difference today. Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Put a shim between the wing and fuse at the rear of the wing(start with 1/16 then 1/8)and see if this helpsThe link i think rick might be talking about is www.geistware.com(rc proving grounds)

Perry Pump
 

Paul,
I got mine from a guy who built the wing upsidedown. That was why I asked. It can be done. Wasn't trying to be a smart-alec or anything. Hope you didn't take it that way.
But I think Rick maybe right. The wing saddle area was pretty rough on mine. Like someone had to grind out the area to get the wing incidence correct. There is also a good setup sheet in the Futaba 8U manual. It is probably the same one Rick is refering to.

Basically if it pulls to the canopy on a verticle downline you need to sand the trailing edge of the wing saddles. If it pulls to the wheels, add a shim, but make it cover the full length of the root so that you don't stress the saddle in one spot.

Rick,
The OS runs very well with the pump. I used large line with medium line for clamps. the perry pump comes with small nipples. So the medium fuel tube clamps tightened up the seal. I also used the large style craptrap. The carb settings are very close to what you would have with a stock muffler pressure setting. Use some thin double side tape, or a dab of shoe-goo, on the pump if you use the stock clamp, or it will vibrate out.

I didn't make any adjustments on the pump. Of course there is no muffler pressure needed with a pump, so the fuel stays clean.

Unless you cut out the floor of the cockpit, the tank won't quite go back to CG, but far enough. I'm running a 20 oz. tank and am getting 12 minutes plus a bunch, flight time. Very rarely does it fly above 1/2 stick. Mucho Grande power! I used a Slimline Pitts muffler. If I could do it over I'd use the Bisson Pitts style w/70 degree pipes. That way the cowl could go on with no extra holes.
Since the 160 broke in I haven't touched the mixture screws. I could bolt the cowl on and forget it!

Happy Flying!

Scott H.

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Scott no offense taken, i did not think you were saying it to be a smart alleck.. Well i flew it yesterday with the 1/2 degree down ,in ailerons and stab, and it has definitely got to be an incidence problem, as i now had to add 6 clicks of UP digital trim,which is not all too bad, as the bird seems to be flying much better as i am getting it "dialed in". i did take it up high and dive it straight down,(no power) she is slightly pulling towards the wheels. (did it three consecutive times with same results.)
I took the 1-1/2 degrees down thrust out of engine, and i now have it at 1/2 degree UP thrust. i am going to see if that makes any difference, and will also shim the rear of the wing, (which might accomplish the same thing as lowering the ailerons)
Thanks again for your comments, and you too wildthing....
Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Just a small comment on my avatar, that is my pro dartar sloping with his seagull "buddy" in Morro bay California.
I was finally able to post my avatar, thanks to Marc, our moderator, and planeinsane.
Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Paul,

How did your Giles turn out? I maidened mine last weekend and needed 10 digital clicks of down trim... I have added a 3/32 shim for down thrust and will check next weekend...

Chris

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Chris,
Thanks for your post. I now have the Giles flying great!
Some one suggested that i put a 1/8"shim under the BACK of the wing.
THAT is WRONG! Don't do that, you need to drop the front of the wing down about a 1/2 degree, (since my stab was expoxied in already, and i could not change the incidence, without major surgery,breaking the stab loose, that is why i chose dropping the front of the wing) .I did this, and the plane flies great with out adding any trim! (I elongated the dowel holes down about 3/32", then made a new plywood plate, with new dowel holes, and epoxied it behind the existing bulkhead, then filled in the gap on the fuselage, where the wing sets, with epoxy and micro baloons) .
Strange, i was just at another flying site about a half hour ago, and a guy has the same plane sitting there, and you guessed it, the elevator is drooping just sitting there!! He said he has to fly it with all that down trim! That is the FIFTH Giles i have seen with my own eyes, with the exact same problem!
So GREAT PLANEs, Tell me you don't have a problem with incidence!! Speaking of Great Planes, i wrote them a long email, about the wrong upthrust, and wrong incidence, but Kraig, their tech guy never emailed me back!
I don't know why they don't put and addendum in each kit telling modelers, what they need to do, to make it fly right!
That would certainly be better than not saying anything about their problem. What if some poor unsuspecting modeler, that is un aware of the problems, goes out and has an accident with the plane,and possibly hurts someone! Is that the way to address the problem, by NOT ADDRESSING it at all, maybe hoping it will go away by it self????
They flat lied to me when i asked them about the up thrust of more than 2 degrees, they said the plane is designed with it !! I believed them, and on the first flight almost stuck it in the ground , because the plane shot straight up, and almost stalled! Hope this is of some help to you,good flying,and happy landings, Paul

Gp Giles 202 1/4 Scale, Upthrust Problem!!!!
 

Paul,

Thanks for the information...

When I built the plane I made the wing and tail incidence 0-0.. Are you saying this is not correct?

Chris