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lostagain
09-15-2006, 05:43 AM
hey thanks for the reply. c.g. is 2 3/4. servos fs3003, reciever r114f. 7cell.esc no name on it came in rtf kit.configuration came from factory as follows,motor, rec, esc batt, on/off, servos in rear.when launching nose is level into wind, motor on or off makes no diff.plane will not even glide six ft.iv'e already replaced esc ,wing connector.controls are not rev.this is like lauching a cinderblock! i have several park flyers and after only one year of moderate flying i have had preety good luck with dec,supercub areo extreme p51 must. i hope this rtf spectra is not just a exspencive wall hanger.any help with this would be great thanks

Sky Sharkster
09-15-2006, 12:02 PM
Hello Lostagain, Welcome to the Sailplane Forum! I have a question, hope it's not too stupid or insulting. Are you throwing the model hard enough? A 2 meter glider takes some "OOOMMPH" to get airspeed enough to fly. A "ParkFlyer" will achieve flying speed with a "hand" toss, that is, just an arm motion. A 1-1/2 to 2 lb glider won't.
Try this; Hold the model over your head, wings level, nose very slightly down. Take a few steps forward, bring your arm forward smoothly and throw the model towards a spot on the ground about 50 feet in front of you. You will be throwing it, not "tossing" it. If the nose is "up" even a little the model will pitch up and (usually) stall into the ground quickly. Don't be worried about pointing the nose a few degrees "down", that's why airplanes have wings!
If you do it correctly the model should rise up a little (excess airspeed/lift) but the nose-to-tail line should stay level, in other words the nose will keep pointing forward, not up or down. Then it should glide in a level path, at least 20-30 feet ahead. It may turn right or left slightly, be gentle with any rudder corrections, just "blip" the rudder to correct, don't "hold" any controls more than a second.
If that doesn't work there's two other possibilities; Extremely forward C.G. (nose heavy) or horizontal wing/stab alignment is incorrect. Is the bottom of the elevator flat and even with the stabilizer? Place a ruler flat along the bottom of the stabilizer, the elevator (in "netural" trim position) should be level with this.
Even an overly-heavy glider will glide flat if the C.G., wing/stab alignment (decalage) and airspeed are correct. Excess weight just makes it sink faster, not "dive".
Good Luck!
Ron

Warden
09-15-2006, 01:33 PM
Lostagain, when you reply, just click on the post reply button at the bottom left of this page. No need to start a new thread.

OK, the CG is 2 3/4 inches from the leading edge. That should work. You should be following Skysharkster's instructions for the hand launch. If the CG is right (and it appears it is) and the elevator is neutral at the launch, you should be getting some glide even WITHOUT the motor running.

A couple things to try: First, go to a small hill. Doesn't have to be a long, high hill, just a nice little hill or mound with a good landing area at the bottom. Put the motor battery in the plane, go to the top of the hill and launch the glider as SkySharkster described without starting the motor. You should get a nice, gentle glide out of the plane. If the plane won't glide without power, then there's something wrong with the wing/tail feather configuration somewhere. Either that or some jokester in China hid a big block of lead in the fuselage!

I'm betting you'll get a glide but if you don't, let us know and we'll check out the airframe set up.

Now the power system. What prop are you using? It should be an 8X4. The props that come with these planes aren't the best but they should fly the plane. You're using a 7 cell battery, that's good. Your battery fully charged should read 8.4 volts (or close to it). There could be a problem with the battery not giving up it's amps fast enough but that's not likely with a battery that was supplied with the plane. It wouldn't hurt to try a different battery. Just make sure the replacement battery can supply enough amps to run the motor. Your parkflyer batteries won't handle that load.

You say you've changed the ESC but you may want to check it out anyway by hooking up the motor directly to the battery to compare the thrust. If you get a lot more thrust with the motor hooked directly to the battery, then there's a problem with the speed control.

Now the motor. Did you break the motor in? Again, the motor should fly the plane even without a break-in period but it wouldn't hurt to run in the brushes so you're getting max power out of the unit. I think their recommended procedure is to hook up a single D cell alkaline battery to the motor and let it run until the battery is depleted. You may want to give that a try.

Do the glide test first. No sense in messing with the power system until we're sure the ship is airworthy.

By the way, my Spectra weighs 2lbs 14oz. AUW.

AEAJR
10-05-2006, 02:54 AM
I have flown several RTF Spectra. They glide fine, with the motor off, from a hand throw.

Questions

You mention the CG position. Is that where the plans/instrucitons say to set it? Sounds a bit forward.

Is the h-stab flat to the fuselage? If it is up a bit, it will effectively give you down elevator.

When you set the CG, do you have the battery in the plane?

You have a set-up problem. That plane should fly fine.

Sky Sharkster
10-05-2006, 01:34 PM
Hello Lostagain, have you checked the "Spectra" instruction manual? Here's the download link;
http://www.electrifly.com/manuals/gpma17-manual-v1_1.pdf
Scroll down to the "Balance The Model" section. A small drawing of the model balanced on a C.G. stand....Center of Gravity should be 3-1/8" inches behind the leading edge, plus or minus 3/8" maximum. You're flying it nose-heavy. Try moving the battery back (or whatever you have to do to obtain this C.G.) and give'er a toss!
The ARF manual shows the same C.G.
Good Luck!
Ron

AEAJR
10-05-2006, 05:02 PM
I have a Spirit, which is basically a Spectra without a motor, and that sounded WAY nose heavy.

cbatters
10-05-2006, 06:08 PM
Was helping launch some other folks planes at a field recently after watching them toss/stall thjeir planes repeatedly. Very common mistake is to toss gently - it will crash everytime. (And with a balsa fuse you will soon be repairing the plane.0.

If it hits the ground after 6-10' you didn't throw it nearly hard enough. (and cg forward of recommended will make it nose in even harder)

As per earlier posts, give it a very firm throw, not a toss. Spectra weights approximately 3 lb and it is more of a hurl than a toss.

NEXT TIP
Assuming you are successfuly hurling it into the air and it starts flying, the only adjustment you should do until you get to ~100' is to bump the rudder left/right to keep it flying straight and possibly push forward on the elevator trim to keep the nose down and the plane climbing at a moderate angle without stalling.

Unless the plane has a lot of extra airspeed, pulling back on the stick will cause the plane to stall - not gain altitude.

For your first couple flights, do very gentle / wide turns and use the trims on the elevator rather than the stick to make small adjustments to the attitude of the airplane.

Remember, pulling back on the stick is the fastest way to reduce airspeed, stall and hit the ground.



Clint

ragbag
10-05-2006, 08:09 PM
If you have ever played cowboy and indians you would know.
Launching a glider is like throwing a spear, pick a target and chuck it at the target with a lot of followthrough.

Before we did electrics, we hand tossed all gliders to check their trim before towing them up on a line. Save a lot of repairs, knowing the were going to fly before we tried to get them way up there!!!!!!!!!!!!!


.................................................. ...................................

AEAJR
10-05-2006, 08:19 PM
Was helping launch some other folks planes at a field recently after watching them toss/stall thjeir planes repeatedly. Very common mistake is to toss gently - it will crash everytime. (And with a balsa fuse you will soon be repairing the plane.0.

If it hits the ground after 6-10' you didn't throw it nearly hard enough. (and cg forward of recommended will make it nose in even harder)

As per earlier posts, give it a very firm throw, not a toss. Spectra weights approximately 3 lb and it is more of a hurl than a toss.

NEXT TIP
Assuming you are successfuly hurling it into the air and it starts flying, the only adjustment you should do until you get to ~100' is to bump the rudder left/right to keep it flying straight and possibly push forward on the elevator trim to keep the nose down and the plane climbing at a moderate angle without stalling.

Unless the plane has a lot of extra airspeed, pulling back on the stick will cause the plane to stall - not gain altitude.

For your first couple flights, do very gentle / wide turns and use the trims on the elevator rather than the stick to make small adjustments to the attitude of the airplane.

Remember, pulling back on the stick is the fastest way to reduce airspeed, stall and hit the ground.

Clint

I think you hit it all.

My gliders go between 100 and 200 feet on a good flat firm throw. I don't touch the elevator unless I accidentally throw throw it up, then I need to get the nose down fast or it will stall and crash. But if the plane is properly trimmed and balanced, I should get at 100 feet with only rudder input.

cbatters
10-05-2006, 08:57 PM
I think you hit it all.

My gliders go between 100 and 200 feet on a good flat firm throw. I don't touch the elevator unless I accidentally throw throw it up, then I need to get the nose down fast or it will stall and crash. But if the plane is properly trimmed and balanced, I should get at 100 feet with only rudder input.

No penalty for throwing too hard except that the plane climbs out a little faster and you may have to apply a little down elevator if the nose is too high. However, if you throw it too soft it WILL crash. And the less wind the harder you will have to throw.

After crashing my Electrosoar badly on the first two flights, I hand launched it a half dozen times without the motor running to prove to myself that it would indeed glide just fine if it had enough airspeed. (In hindsight, my problems flying the Electrosoar were: cg too far forward, flying in too much wind, attempting to climb too steeply / stalling and turning before getting up to 100+ feet. Come to think of it, I don't think I did anything right except the range check and the launch.)

I stopped flying the ElectraSoar after the second major crash and instead got some good flying experience on a 2m foam glider on a highstart. The only downside is that the sink-rate of any electric glider seems pretty awful compared to a straight glider.

Currently flying a couple Electric RTF's (SkyFly / Challenger) but spend most of the time with the motor off gliding after using the motor to get up to altitude. (I also picked up a Hobbico Swift Flyer that I still enjoy watching/flying - it floats so effortlessly the only thing I have to do is keep it from drifting out of range.)



clint

humphreysd@rica.net
10-06-2006, 06:16 PM
I have a spectra, and the C.G. is about 3 1/8 inch behind the leading edge of the wing. I have moved it back and forward a bit but this location is the one that works best for me. Have fun with it.

Durwood