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Old May 15, 2012, 06:46 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
2,879 Posts
Quote:
Originally Posted by leethetreeguy View Post
Man, mine was a handfull to fly. Even with a dx8! Untill I got the COG right. Good luck with that toy tx.
Lee
I know what you mean. Getting the CG and trim right is absolutely critical for this model, but once you do, it will literally fly hands-off in calm conditions. There was a day when I even regretted buying it, thinking it was all about good looks and not about being airworthy. Now I love it, and even used it on a buddy box one day to teach a beginner to fly.
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Old May 15, 2012, 08:08 PM
Registered User
Vrated's Avatar
United States, UT, Marysvale
Joined Aug 2004
1,113 Posts
I will be sure to get the C.G. set right, Triming may be a little touch and go because of the area I am flying in. Flying here is a constant dodging the trees which I have no problem doing so far. I just cant let her take a heading and adjust the trim for straight and level flight at a cruise. I may have to go into town and fly in the open spaces there for the maiden and get the trims set right. Also, if the stocker Tx may present some problems, I'll just wait till I get my DX7, No biggie there. I have an idea for making some custom wing servo covers too. Thanks for the tips guys. Preperation is the key for success!
~Vrated
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Old May 18, 2012, 01:46 AM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Had a successful maiden of my UM Corsair this evening in nice near-dead-air conditions, plus 4-5 more mostly smooth flights. But I gotta tell ya, that "dime mod" is not for everyone; it almost ruined may maiden (double entendre intended ).

I checked the C.G., and seemed pretty spot on, but so many posters here have advocated adding weight to the nose that I went ahead and taped a dime under the cowl as suggested before the maiden.

I hand-launched (flying off a grass field) at full throttle, kept the wings nice and flat... and watched her sink like a stone! I saved her from certain disaster with a goodly dose of up elevator, and then leveled out to see if it was just a lack of airspeed, but she started sinking again, so I started madly clicking the elevator trim with my left hand while driving with my right. By the time I could let the the stick back to neutral, I had nearly maxed out the trim, and she was just maintaining altitude at full throttle.

At that point, and after trimming in a few clicks of right rudder and aileron, she was actually handling surprising sweetly without my having to ride herd on the controls as I had expected. So I flew a full 5 minutes or so before setting her down in the grass as slow as possible with just a bit of a stall-and-plop at the end.

I immediately pulled the dime off, and took the trim back to neutral for the second flight (I counted 19 clicks!), but I still ended up with 8-9 clicks of up elevator to fly level at 60-70% throttle, and climb gradually above that. This one is definitely not tail-heavy. And it's not just that the pushrod needs adjusting to center the surface; there is a noticeable deflection of the elevator in flying trim.

Third flight started off with a bang, literally, when she did a super-quick full roll right out of my hand, and lawn-darted into the ground at full throttle not 6 feet away from me.

When I picked her up, I found that one aileron horn had worked its way around the the bend in the pushrod, and the aileron was at about a 45-degree angle. I think I must have hit it with my hand on the toss, because I was finding it a little awkward to have to hold the fuse so far behind the C.G. Fortunately, and somewhat surprisingly, the only damage was a ding to the cowl where the prop flex back and hit it, and after fixing the pushrod, I had three more uneventful flights.

She seems to fly well, and once trimmed was as stable as could be hoped, just needing the slightest nudge on the ailerons now and then to keep flying straight, and turning very smoothly and predictably. I even switched off the D/R and expo I had dialed in on all channels with a Combi switch, because I found her quite manageable and just nicely responsive without it.

One concern I have is that the motor/gearbox does not run smoothly at throttle settings below about 60%. It seems to have a little "hitch in its gitalong" every few seconds, like the gears are wandering back and forth with the end-play in the prop shaft, and getting a little misaligned at the limit. This is not due to the nose-in, because I noticed this right out of the box. I had hoped it would go away with a little break-in, but it doesn't really seem to be improving.

Anyone else see anything like this?
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Old May 18, 2012, 03:13 AM
Is it Friday yet?
DropTank's Avatar
United States, NC, Raleigh
Joined Jun 2008
690 Posts
Mine is one of the tail beavy ones. I cut a hole behind the cowl so I could slide the battery up farther. Flys really good like that.

So far, the motor seems fine on mine.
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Old May 18, 2012, 06:52 AM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
2,879 Posts
Quote:
Originally Posted by BrundleFlyBy View Post
She seems to fly well, and once trimmed was as stable as could be hoped, just needing the slightest nudge on the ailerons now and then to keep flying straight, and turning very smoothly and predictably. I even switched off the D/R and expo I had dialed in on all channels with a Combi switch, because I found her quite manageable and just nicely responsive without it.

One concern I have is that the motor/gearbox does not run smoothly at throttle settings below about 60%. It seems to have a little "hitch in its gitalong" every few seconds, like the gears are wandering back and forth with the end-play in the prop shaft, and getting a little misaligned at the limit. This is not due to the nose-in, because I noticed this right out of the box. I had hoped it would go away with a little break-in, but it doesn't really seem to be improving.

Anyone else see anything like this?
Yes it is a sweet flying plane but it has an achilles heel and that is the motor. If you read back on this thread there is lots of talk about it. Mine also sounds ok at maximum throttle but sort of varies in pitch at lower throttle settings. These motors are famous for their unreliability, and one of these days I am going to replace it with a Bravo motor, which is supposed to be better.
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Old May 18, 2012, 07:48 AM
Porro et Sursum
Flying V's Avatar
Australia, New South Wales, Lismore
Joined Oct 2010
173 Posts
2s it!

Mod it for 2s brushless. You won't regret it.
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Old May 18, 2012, 09:20 AM
Registered User
Vrated's Avatar
United States, UT, Marysvale
Joined Aug 2004
1,113 Posts
Flying V,
I like the skewer and magnets trick too.
Brundle,
Thanks for posting. I am hopeing my maiden will turn out as good as yours.
~Vrated
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Old May 18, 2012, 10:24 AM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Quote:
Originally Posted by Jovanx View Post
Yes it is a sweet flying plane but it has an achilles heel and that is the motor. If you read back on this thread there is lots of talk about it. Mine also sounds ok at maximum throttle but sort of varies in pitch at lower throttle settings. These motors are famous for their unreliability, and one of these days I am going to replace it with a Bravo motor, which is supposed to be better.
Thanks for the input. I remembered reading a number of posts about variability in power from one motor to another, and premature "squealing death syndrome", but nothing that really matched what I'm hearing, which sounds like there's an evil gnome sitting in the engine compartment, and throwing tiny stones into the gears at irregular intervals:

Hummmmmmmmmmmmmmmm-glitch-mmmmmmmmmmmmmm-glitch-mmm-glitch-mmmmmmmmmmmmmmmmmmm-glitch...

The more I listen to it, the more it seems like a gear drive problem, rather than a motor problem.

Hate to go cutting into a new plane right off the bat to see what's going on, but I might have to.
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Old May 18, 2012, 10:43 AM
Fly em if ya got em.
leethetreeguy's Avatar
Winder Ga
Joined Sep 2008
11,644 Posts
Just take the dang stones away from that evil bas****. hahaha
Lee
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Old May 18, 2012, 11:32 AM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
2,879 Posts
Quote:
Originally Posted by BrundleFlyBy View Post
...sounds like there's an evil gnome sitting in the engine compartment, and throwing tiny stones into the gears at irregular intervals
I guess you must have seen that classic episode of "The Twilight Zone" where the gnome was bashing on the engine with a hammer. It's not a big deal to open it up. You are only cutting scotch tape, not foam.
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Old May 18, 2012, 11:44 AM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Quote:
Originally Posted by Jovanx View Post
It's not a big deal to open it up. You are only cutting scotch tape, not foam.
Yeah, but it's pristine OEM tape.
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Old May 18, 2012, 12:48 PM
when down=up, up=expensive
whichwaysup's Avatar
United States, VA, Roanoke
Joined Apr 2012
2,647 Posts
I've had this happen with a brand new motor. What you are describing - to your point - could either be motor or gears. Easiest way to tell is to unscrew the nylon nut off the back of the gear and let the motor run without it. you'll know in about 5 seconds. On the other hand, if you do find a Gnome in there, he might look better in that empty cockpit. And he'll need those "stones" for an entirely different purpose.
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Old May 18, 2012, 01:01 PM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Thanks, whichway; that's kind of what I was thinking - remove the prop and gear to check the unloaded motor. If I can't tell what's going on just by watching it run, I'll do that.
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Old May 22, 2012, 04:56 AM
Flyin' low & slow T-28s!
MaladroitFL's Avatar
United States, FL, Vero Beach
Joined Feb 2011
3,324 Posts
Quote:
Originally Posted by BrundleFlyBy View Post
Had a successful maiden of my UM Corsair this evening in nice near-dead-air conditions, plus 4-5 more mostly smooth flights. But I gotta tell ya, that "dime mod" is not for everyone; it almost ruined may maiden (double entendre intended ).

I checked the C.G., and seemed pretty spot on, but so many posters here have advocated adding weight to the nose that I went ahead and taped a dime under the cowl as suggested before the maiden.

I hand-launched (flying off a grass field) at full throttle, kept the wings nice and flat... and watched her sink like a stone! I saved her from certain disaster with a goodly dose of up elevator, and then leveled out to see if it was just a lack of airspeed, but she started sinking again, so I started madly clicking the elevator trim with my left hand while driving with my right. By the time I could let the the stick back to neutral, I had nearly maxed out the trim, and she was just maintaining altitude at full throttle.

At that point, and after trimming in a few clicks of right rudder and aileron, she was actually handling surprising sweetly without my having to ride herd on the controls as I had expected. So I flew a full 5 minutes or so before setting her down in the grass as slow as possible with just a bit of a stall-and-plop at the end.

I immediately pulled the dime off, and took the trim back to neutral for the second flight (I counted 19 clicks!), but I still ended up with 8-9 clicks of up elevator to fly level at 60-70% throttle, and climb gradually above that. This one is definitely not tail-heavy. And it's not just that the pushrod needs adjusting to center the surface; there is a noticeable deflection of the elevator in flying trim.

Third flight started off with a bang, literally, when she did a super-quick full roll right out of my hand, and lawn-darted into the ground at full throttle not 6 feet away from me.

When I picked her up, I found that one aileron horn had worked its way around the the bend in the pushrod, and the aileron was at about a 45-degree angle. I think I must have hit it with my hand on the toss, because I was finding it a little awkward to have to hold the fuse so far behind the C.G. Fortunately, and somewhat surprisingly, the only damage was a ding to the cowl where the prop flex back and hit it, and after fixing the pushrod, I had three more uneventful flights.

She seems to fly well, and once trimmed was as stable as could be hoped, just needing the slightest nudge on the ailerons now and then to keep flying straight, and turning very smoothly and predictably. I even switched off the D/R and expo I had dialed in on all channels with a Combi switch, because I found her quite manageable and just nicely responsive without it.

One concern I have is that the motor/gearbox does not run smoothly at throttle settings below about 60%. It seems to have a little "hitch in its gitalong" every few seconds, like the gears are wandering back and forth with the end-play in the prop shaft, and getting a little misaligned at the limit. This is not due to the nose-in, because I noticed this right out of the box. I had hoped it would go away with a little break-in, but it doesn't really seem to be improving.

Anyone else see anything like this?
The "Dime Mod" is only for tail-heavy models. It's not for a maiden flight. You have to fly it to determine whether or not you got a squirrely, tail-heavy, near unflyable model.
If you're lucky, you will fly straight and true right outa the box, if not, then try the dime, or cut the slot @ the front of the battery tray and slide the lipo far forward.

Mac
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Old May 22, 2012, 12:19 PM
Never stop being a kid.
BrundleFlyBy's Avatar
United States, CO, Manitou Springs
Joined Jan 2012
543 Posts
Quote:
Originally Posted by MaladroitFL View Post
The "Dime Mod" is only for tail-heavy models. It's not for a maiden flight. You have to fly it to determine whether or not you got a squirrely, tail-heavy, near unflyable model.
Got it. On re-reading your post #2, I see that you did emphasize flying without the mod first.

Although I realized it was a possibility I'd move the C.G. more forward than necessary, I figured that would be easier to handle than the severely tail-heavy behavior that some have described (as the saying goes: "a nose-heavy plane flies poorly; a tail-heavy plane flies once").

What I didn't expect, based on my reading of the thread, was that some UM Corsairs might actually be a little nose-heavy (or have inherent nose-down trim with surfaces centered) out of the box, which would make them fly really excessively nose-heavy with the dime mod as mine did.

As it stands, it looks like I might actually be needing to move my battery back a hair to eliminate the need for down [EDIT: Oops. make that "up"] elevator trim.

Soon I'll have servo covers on, and eventually plan to try it sans landing gear with a 5043 prop. Removing that gear drag may be what it really wants, and I think it'll look sweet in the air without it.
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