GP Extra 300, 40 ARF expo settings
 

I'm just finishing a Great Planes Extra 300 40 sized ARF. I've setup the throws as described in the manual, but they didn't suggest any expo settings.

Does anyone that has this plane have any recommendations as to reasonable expo settings to start out with for both low and high rates?

Thanks,
Keith

GP Extra 300, 40 ARF expo settings
 

I don't use expo. Aileron response is slow on this plane. They're too small. Elevator is fine. I am now flying with the C.G. 4-3/4 back from L.E. I also added a little right thrust. I found this plane to be a little sloppy until I moved the C.G. back. Now it really rails. ;)

GP Extra 300, 40 ARF expo settings
 

Thanks ILikeplanes.

I flew it for the first time Monday. Flew pretty good but drifts to the left when coming over the top doing loops & Cuban eights. I'm working on adjustments now to try and straighten it out. First step was to adjust the right half of the elevator that had a slight warp in it making the two sides slightly uneven on the inner most portion of the elevator.

It's interesting to hear that you put right thrust in the plane, I may need to do the same. Were you seeing the same behavior of drifting left when going over the top of an inside loop? How much right thrust did you add?

You're right about the slow rolling. Also I had to add more elevator than is suggested in the manual. This probably indicates that I have the CG too far forward, I started at 4" as suggested in the manual.

Are you able to bring this plane in fairly slow without having it tip stall?

Thanks for the info, anything else that you can suggest would be appreciated.

Keith

GP Extra 300, 40 ARF expo settings
 

The right amount of Right thrust depends on what prop you use, and how fast you are typically moving. The idea is that air hitting the rudder doesn't come straight back from the prop it spirals so it tends to push the tail into a left turn. lower pitch props tend to need less right thrust.

Low speed is risky with this plane. There are some things you can do to help reduce tip stall problems. it is a good idea to program some spoileron. The ailerons should go slightly up when the elevator is up and slightly down when the elevator is down. it hardly makes any difference in normal flying charactoristics, but creates a little washout for you. nice thing is it does it for inside or outside loop conditions automatically. Radiusing the leading edge a bit more blunt is supposed to help a lot too, but i haven't tried it.

i have dumped mine into the ground twice letting the airspeed get to low (dead sticks) never try to float this plane in with the nose up even a tenth of a degree. it will put up with it for a second or two, then Wham! not even a millisecond warning.

enjoy,

GP Extra 300, 40 ARF expo settings
 

I agree with shmo46.

I had the max throws I could get and had 30% expo on the elevator and ailerons.

Don't slow it down too much or it will drop a wing quick!

It is a great fling plane with almost no coupling at all. knife edge was a piece of cake and you could add ruuder in level flight and the plane would still fly level.

A great third plane, maybe even second if you are careful.

Brian

GP Extra 300, 40 ARF expo settings
 

Thanks for the replies.

shmo46, how much spoileron coupling did you add? Also, have you seen the drifting left issue and did you also add in right thrust?

shmo46 and Skypilot_one, where do you have the CG?

FYI, I've got an OS 70 Surpass on it with a 13x6 prop.

I did have one dead-stick landing Monday, worried the begeepers out of me :). I'd just done a hammer head stall and killed the engine (low throttle trim was too low). I flew a quick circle around and landed on the runway, but the whole way I was worried about slowing it down to much and letting it fall out of the air.

So far all of my landings have been pretty hot and will probably stay that way until I get a feel for how slow I can come in.

Thanks for all the info!

Keith

GP Extra 300, 40 ARF expo settings
 

At first, I started to get very frustrated by this plane. It simply would not fly straight. My old under powered Big Stick flew better. It corkscrewed in loops, wouldn't fly a straight vertical line, landed like a missile, dropped when inverted, pulled out of down lines, etc. I looked at some links to trimming pattern planes and talked to a former IMAC flyer in my club. My problems boiled down to:

1) Improper thrust angle. This is difficult to separate from rudder trim. Your rudder should really be right down center. Engine thrust problem can be given away by testing differences on and off throttle. For example, yaw changes during up line due to throttle changes or hard right rudder required for take-off. I added #10 washers behind the left side of the engine mount. I calculated this to be 1.5° right and .75° down.

2) C.G. I moved my C.G. back between 5/8 to 3/4 back from the recommended 4 inch mark. I may move it back more. This is easy to test. The plane should go straight down out of a hammer head stall turn. If it pulls out, even slightly, it is probably tail heavy. Another good test is to fly up at a 45° and do a half roll. The plane should hold the original line hands off. If it drops more than a little when inverted, it's nose heavy. The IMAC guy said that when you pull a hard turn, and you get a slight tail wiggle, your C.G. is close yo optimum for aerobatics.

3) Lateral balance. I added about 1/4 oz to the left wing. This is revealed when doing outside and inside loops. If you have a lateral balance problem, it will drop the same wing inside and out.

Now that I have it sorted out, I am really starting to get into the groove with this plane. :D Now, it's just a matter of practice. :eek:

I use a 12-8 prop on a Saito 72. It seems to fly better at part throttle than the 13-6. Landings with this prop are pretty fast. Remarkably, it lands much better with the aft C.G. It does stall abruptly though so fly not float it down. I take up more runway than the giant scalers. :rolleyes:

Keep after it. You'll be rewarded with a great little aerobatic plane.

Good Stuff!
 

That's great info ilikeplanes :thumbup: . I look forward to trying some of these things.

BTW, I have noticed that even though the elevator trim is good at full speed level flight, when I dive the plane it wants to drift up-wards. I assume this is what you meant by "pulled out of down lines". Also it takes a lot of right rudder on takeoff, so much that when it leaves the ground and I release the right rudder it yaws to the left significantly.

You mentioned that you used #10 washers on the left side, did you use just one washer on the top and bottom of the left side or multiple washers? If just one washer on each how did this result in any down thrust?

When you moved the CG back did you have to reduce your elevator throw?

Thanks for the excellent info, this is really going to save me a lot of frustration :D !

Keith

GP Extra 300, 40 ARF expo settings
 

Hey, when were you flying my plane? Everything you described is exactly what I had. Even the take-off thing.

You mentioned that you used #10 washers on the left side, did you use just one washer on the top and bottom of the left side or multiple washers? If just one washer on each how did this result in any down thrust? I used one top and one bottom (about .040 thick). Since the engine is mounted at a 30° angle, the washers will cause a little down thrust. Just do the trig.

When you moved the CG back did you have to reduce your elevator throw? Yes, I moved the linkage one hole out on the elevator. One hole in on the servo would have a similar effect. Be careful with a more aft C.G. If you go too far, it will become unstable. Only trial and error with reveal the true limits.

GP Extra 300, 40 ARF expo settings
 

Hi Keith,

I'm not a very precise flier, but i didn't think mine needed more right thrust. It even torque rolls with the stock thrust setting. I use a saito 100 and a APC 15x6 (?) i haven't flown it in a few months, but if memory serves i have about 1/8 spoileron deflection at max. don't know if it is the spoileron or the pilot is more cautious, but i haven't had tip stalls for a while - especially when it is sitting in the closet :D

GP Extra 300, 40 ARF expo settings
 

shmo46,

Are you sure you have the same plane, Great Planes Extra 300 40 size ARF?

I can't believe you have a Saito 100 on this plane!!! :eek:

Keith

GP Extra 300, 40 ARF expo settings
 

Affirmative Keith,

Great planes 40 sized Extra 300, Saito 100.
Unlimited vertical, 0-60 in a second (?).

The plane is pretty stout, has no problem holding the vibration.
i am sure i pay a small penalty in stall threshold for the extra weight, but it is a blast to fly. The best part is the take offs. :D I made a hatch 2/3 of the way down the fuse to hold the battery to keep the weight down as much as possible. It ballanced without lead.


Too much is just enough.

GP Extra 300, 40 ARF expo settings
 

I have just upgraded my Extra from an Enya 80 4C to an OS91 Surpass. What a difference. It has unlimited vertical and it can knife edge loop. Most of the flying is at half to three quarter throttle.

I land hot after it half snapped into the runway on landing on one of the first flights. I was so low there was no damage. I use a lot more aileron throw than the manual recommends. This greatly improved the roll rate. Elevator throw is around where the manual suggests.

I'm using 30% expo on the elevator. Nothing on the ailerons.

This planes does great spins using rudder and elevator only.

Have fun

GP Extra 300, 40 ARF expo settings
 

With an OS 70 Surpass mine seems like a missile, I can't believe you guys have that big of an engine on your planes :eek: .

I haven't tried to hover, but in a climb the plane seems to have unlimited vertical, but since I haven't tried it yet I'm not sure if it would pull out of a hover (not that I'll be doing that any time soon :) ).

Today I was doing touch and goes and I had to be very careful applying throttle when leaving the ground because the torque of my OS 70 wanted to roll the plane to the left, I had to pull it back level with right aileron.

BTW, I worked on my elevator warp and it didn't help the problem of the plane fading left at the top of loops (I didn't think it would but want to make one correction at a time, not to mention I wanted to fly today :D ).

My next change will probably be to shim the engine to add right thrust.

Another thing that bothers me about the current setup is that I hate the "Y" push-rod on the elevators. I don't think they're very accurate and I feel like there can be play between the elevator halves as the push rod wiggles left to right. I've ordered two HiTec HS-85 BB mini servos and I'm going to put them in the rear of the plane, one on each elevator half. They are the smaller servos and only weigh .70 oz. each, but still have 40+ oz. torque (with 6 volt battery) and should easily handle one half of the elevator. By doing this I can assure the elevator halves work together and the "Y" push-rod is not moving side to side. I've already checked the CG with the weight in the tail and it will be fine.

I'm also considering adding a pull-pull control to the elevator because my elevator control does not center very accurately with the lame push-rod that it currently has.

One more thing. I fly off of slightly bumpy grass and the first time I flew it wanted to keep tipping over. I changed the tail gear to a Sulivan tail gear with a spring and surprisingly it doesn't have the same tendency to tip over. I think this is because the tail wheel now absorbs some of the bumps and the stock wheel was so ridged that it just bounced the entire tail up in the air.

I'll let you guys know how it goes.

Keith

GP Extra 300, 40 ARF expo settings
 

Yea, those push rods suck. I replaced the wood dowel with some salvaged carbon kite rod. It still has a tendancy to move left-to-right though. I tinkered with the wire bend angles until I was satisfied.

Your dual servo set-up will be awesome. You might as well do a pull-pull on the rudder while your at it.

GP Extra 300, 40 ARF expo settings
 

I've heard some folks will mount a guide in the fuselage to keep the Y end of the pushrod from moving around. Might do the trick with less work.

My two cents, refunds available on request

GP Extra 300, 40 ARF expo settings
 

shmo46,

That certainly would help and may do the trick, but will still require me to cut open the fuse and there's no guarantee that the geometry of the "Y" push-rods will be accurate. With two servos I can use my radio to fine tune the throws and have precise control over them. It's probably overkill, but what the heck ;)

BTW, I saw on another thread last night a gadget that is supposedly used by pattern guys to keep the split elevator throw accurate. Looks cool, but since the plane is already built it would probably be even harder to install than two servos.
http://www.rcuniverse.com/showthread...6655#post18461

Keithh

Modification Complete!
 

Well, I went the whole nine yards and installed both rear elevator servos and a pull-pull system for my rudder.

The improved fine tuning accuracy I have is like night and day over using the "Y" push rod. Using two Great Planes deflection meters, one on each elevator half, I was able to get the elevators working perfectly together both at the end-points and at every point in between. And there is NO play or give in the elevators what so ever!

On the elevators I ended up using two HiTec HS-85 BB mini servos which weigh .70 oz. each and have a torque of 41 oz. with a 4.8 volt battery. This adds only 1.4 oz weight to the tail and gives me 82 oz torque on the elevator (Way Overkill for this plane :) ).

I used 5.5" 4-40 titanium push-rods (threaded on both ends) and and 4-40 clevises. This is also way overkill but my LHS didn't have the 2-56 versions. Initially I was going to use very short push-rods and mount the servos under the horizontal stab, but the guy at the hobby shop talked me into using the 5.5" rods to move the servos up the fuse to reduce the amount of weight I would be adding to the tail and it also allowed the servos to fit in the fuse directly across from each other since the fuse is thicker further up. I'm happy that I took this approach. The extra distance between the servos and control horns doesn't hurt the solid control in the least.

BTW, the entire modification only moved my CG back 3/16" to 1/4" from where it was initially.

On the rudder I added a 2-56 pull-pull system. This was my first pull-pull to install and I'm really happy with it. Now my rudder centers right on the money!

Doing this was somewhat a pain, but the truth is that now I can know with full confidence what my control surfaces are doing. By continuing to work out tracking issues without knowing what the surfaces are doing in the air I could have wasted a lot more time.

Flying Results:

I've only had two flights on the plane since the change, but I can say for sure that it definitely tracks better. At this point I don't have enough flight time to be sure if I want to do any further modifications. It still fell off to the left coming over the top a little, but it was controllable with rudder. Honestly I'm not sure yet how much was me, the wind or the natural behavior of the plane. I need some more flight time to decide if I want to play with changing the thrust angle or CG. Also, I want to be careful not to effect the normal straight tracking of the plane if it is normal for this plane to fade left over the top. An IMAC pilot I spoke to this weekend said that he always has to apply some rudder corrections coming over the top to keep his plane perfectly straight. I'm not sure if this is normal or not.

BTW, after trimming and landing the plane all my controls, including rudder and ailerons were almost perfectly centered. I think it's pretty straight now.

Here are some pictures of my modifications, by the way I haven't cleaned up the old push-rod holes yet, didn't have the right shade of white covering ;) :

GP Extra 300, 40 ARF expo settings
 

Top shot:

GP Extra 300, 40 ARF expo settings
 

Pull-pull system:

GP Extra 300, 40 ARF expo settings
 

Keith,
It seems like you have it all figured out thanks to replies on this thread! I love the dual elevator and pull pull setup. I am rebuilding a used GP Extra 300 40 ARF. I am planning to do the following:

Saiti 100(weighs same as OS 70)
15 x 6 Prop
Hitec 605 pull pull on the rudder
2 HS 85BB on the elevators
CG 4 3/4"
HS 81 Throttle
Possibly larger tank is my flight times are short

Here are my questions:

What throws and expos did you end up using?

What thrust did you end up using?

Do you use spoilerons?

Do you leave the spoilerons on all the time or just when landing?

How much throw in the spoilerons?

How is your upline?

How is your knife edge?

What would you do differently, do you have anything else to suggest?

Are you using the supplied tank?

What are your flight times?

Thanks in advance

GP Extra 300, 40 ARF expo settings
 

Elevator: low: 3/8", high: 1/2" (never use high), no expo
Rudder: low: 1 1/4" low, high: 2", no expo
Aileron: low: 1/4", expo 15%, high: 3/8", expo 30% (normally fly on high)

Note: My CG is only 4 1/4" back (I suggest you start out there then work your way back). If you use 4 3/4" you may not need as much elevator throw as I have.

Still haven't changed the right thrust, that's the last change I plan on making. I've been experimenting with other things first.

Latest change was to remove an external wing weight on left wing tip and put in inside the wing. My concern was that it was causing drag on left wing tip and making things worse on the up-lines fading to the left by causing the left wing to slow more quickly. I've only flown it once with the weight inside the wing and it was really windy, but surprisingly I think it did help. Got do do more tests to know if I want to change the thrust. Changing the thrust may help the right side up up-line, but could cause other problems, especially the inverted up-line flight.

The issue I have is to determine how much of the fading left is due to P-factor vs. torque. If it is a P-Factor issue then right thrust will definitely make inverted up-line flight fade left even worse because P-factor will always make the plane go left, inverted or right side up, due to the pitch of the blades.

No.

Getting better, but want to fly some more with latest change to see if it's good enough. From what I hear it's normal to have to use some rudder to keep it straight going straight up. I really need an experienced IMAC or pattern guy to fly it and tell me if what I'm seeing is out of the norm. My gut feeling is that it still fades left too much. My further tests will determine whether or not I change the thrust.

It fades quite a bit to the belly. I finally mixed in some up elevator with my rudder (about 8% to 10%). It's not easy to do the knife edges without the computer mixing because of the large amount of elevator coupling that is needed.

It has plenty of rudder for knife edge flight and will even climb, not sure if it will do knife loops (certainly not with my 2" throws).

If you're wanting to work on/learn IMAC or pattern precision flying then you may not be happy with this plane unless the thrust change will solve the fading left. This is the boat I'm in. I'm hoping I can get it worked out. On the other hand if precision isn't important to you the plane flies really beautifully and lands fairly easily with the 4 1/4" CG.

I really can't think of anything else I'd change.

I bought the pane second hand and it didn't come with a tank. But I did use a GP 12 ounce tank (think it's shaped the same as the one in the kit). This helped because the shape fit nicely in the tank compartment.
I can fly 20 minutes or more, but usually limit my flights to 15-17 minutes so I don't take any chances. My OS 70 FS is a real fuel miser :) (at least for a glow engine).