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View Poll Results: Add Another Option: BMN (Bare Minimum Necessities)
no batteries, no charger, and no tx! $59.99(BMN) 712 85.99%
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Old Jul 13, 2012, 05:09 PM
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shastamike's Avatar
United States, CA, Mt Shasta
Joined Jun 2010
2,449 Posts
Quote:
Originally Posted by msdumo View Post
Your going the wrong way. It's not tail heavy but nose heavy.
A nose heavy plane needs a lot of up elevator to fly level and then becomes very pitch sensitive as the throttle is changed.
The plane will pitch up when the throttle is increased.
Pitch coupled with throttle is the sign of a nose heavy plane.
A tail heavy plane is not stable and nearly impossible to fly.
A lot of people misdiagnose a nose heavy problem for a tail heavy one.

Measure the CG with the plane upside down.

I use 240 hyperion flat packs about 1/4 inch from the rear of the battery tray.
I have yet to see a T28 that required weight in nose.
Quote:
Originally Posted by mclarkson View Post
I haven't flown my little T-28 in months, either, so I decided yesterday was the time. Winds were down to 7MPH or so, which counts as dead calm where I live, and the temps were only in the mid-90's.

I'm flying with a 160mAh pushed all the way back in the stock battery slot and it feels a bit nose-heavy to me still.

https://vimeo.com/45675903
With mine if I pushed the battery back all the way it would fly more like a helicopter, no way I could control it. I wonder if my T-28 is set up oddly. I notice that with the Champ the propeller shaft is set down and to the right to counteract the torque of the motor i suppose. Is the T-28 like that? Mine's set straight and square coming out of the nose. Only way mine's flying like in this video is with lead shot in the nose and the battery all the way forward and elevator trim forward (down elevator).
Any thoughts. Thanks.
Mike
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Old Jul 13, 2012, 05:34 PM
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shastamike's Avatar
United States, CA, Mt Shasta
Joined Jun 2010
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yep...I checked my propeller shaft and it is set to the right slightly (from the pilots perspective) but not downward. It is in line with the fuse half line so not downward at all. Could someone check theirs? I think this would explain why I have to add to much weight forward and down elevator to fly. Does anyone else have to weight their nose? I'm really enjoying flying the T-28 but the CG thing really bugs me. I suppose I just need to get the plane to fly the way I'd like and relax.
Mike
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Old Jul 13, 2012, 07:45 PM
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Canada, ON, Calabogie
Joined May 2011
261 Posts
Quote:
Originally Posted by shastamike View Post
yep...I checked my propeller shaft and it is set to the right slightly (from the pilots perspective) but not downward. It is in line with the fuse half line so not downward at all. Could someone check theirs? I think this would explain why I have to add to much weight forward and down elevator to fly. Does anyone else have to weight their nose? I'm really enjoying flying the T-28 but the CG thing really bugs me. I suppose I just need to get the plane to fly the way I'd like and relax.
Mike
The only UM that often comes tail heavy is the Corsair. Most flyers use a penny just under the cowling of the Corsair to remove the tail heavy situation. I've never seen anyone add nose weight to a T28.

I can't understand why the plane flies like it does but from what you've told me about severe pitch with throttle it still sounds like you have a nose heavy plane.

The only suggestion I can come with is to check the CG again and you must be fairly accurate. The plane must be upside down. The CG for the T28 should be 30-32mm from leading edge.

I fly mine with CG between 32-36mm depending on the wind. I move the battery a little more forward as the wind increases. For most of my flying, the back of the battery is between 1/8 and 1/4 of an inch from the back of the battery tray.

I use 2 wooden skewers stuck in the foam in the box the plane came in to measure the CG on my UMs.

Good luck
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Old Jul 14, 2012, 10:38 AM
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shastamike's Avatar
United States, CA, Mt Shasta
Joined Jun 2010
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Quote:
Originally Posted by msdumo View Post
The only UM that often comes tail heavy is the Corsair. Most flyers use a penny just under the cowling of the Corsair to remove the tail heavy situation. I've never seen anyone add nose weight to a T28.

I can't understand why the plane flies like it does but from what you've told me about severe pitch with throttle it still sounds like you have a nose heavy plane.

The only suggestion I can come with is to check the CG again and you must be fairly accurate. The plane must be upside down. The CG for the T28 should be 30-32mm from leading edge.

I fly mine with CG between 32-36mm depending on the wind. I move the battery a little more forward as the wind increases. For most of my flying, the back of the battery is between 1/8 and 1/4 of an inch from the back of the battery tray.

I use 2 wooden skewers stuck in the foam in the box the plane came in to measure the CG on my UMs.

Good luck
I've checked the CG very carefully as you instructed and the CG is with the battery about where you said in the tray, yet if I fly like that the plane flys dragging it's tail (tail heavy?) and any increase in throttle makes it nose up and stall. Not porpoise, more like it's trying to hover. Only way I can make it fly is to put the battery all the way forward and trim the elevator downward all the way. I'm still wondering if it is because the propeller shaft is mounted incorrectly. I'm going to call Parkzone with my problem. Can someone check their T-28 and tell me if the prop shaft comes straight out of the fuse or are they set slightly down and to the right like the Champ?
Also, I'm wondering, instead of adding weight to the nose to correct this maybe I should do a elevator>throttle mix to correct the tendency to stall and hover with throttle increase? Thanks.
Mike
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Old Jul 14, 2012, 11:02 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
2,598 Posts
Quote:
Originally Posted by shastamike View Post
Can someone check their T-28 and tell me if the prop shaft comes straight out of the fuse or are they set slightly down and to the right like the Champ?
Mike
there is both Right and Down thrust in mine.

If you examine the box, you can see that the right thrust is accommodated by the packaging, which I thought was cool; and, by the angle of the front of the fuse, when viewed from above, which is also cool.

I appears that the front of the cowl is also angled to the down thrust.

Try shimming the motor so the shaft is perpendicular to a plane described byt the front of the cowling, vice the center axis of the fuselage. The prop arc then becomes parallel to the circle described by the LE of the cowl.

I used this "rule of thumb" to success at the last engine change.
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Old Jul 14, 2012, 11:34 AM
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United States, CA, Mt Shasta
Joined Jun 2010
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Thanks for the advice. I've now noticed that the front of the cowl is shaped to the right and my propeller follows that OK. It's also shaped a bit downward and my prop definitely doesn't follow that. So I have no downward thrust and thus the plane acts tail heavy and climbs uncontrollably at half or more throttle. Lucky me, and it was the second one they sent as the first got smashed by UPS. Made for an exciting first flight.
Really don't feel like opening the fuse to shim the motor though, but a good side project when I do.
I'm wondering still about the use of weight to correct my problem as opposed to a throttle to elevator mix?
Mike
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Old Jul 14, 2012, 12:11 PM
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United States, CA, Mt Shasta
Joined Jun 2010
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Can't get Horizon Hobby on the phone this morning. Got to looking at my T-28 and the problem is definitely the angle of the prop shaft. The shaft is correct on the right pitch, but no down pitch. I believe the correct action would be to solve this instead of adding weight or mix to elevator. davidterrell80 suggested opening the fuse and shimming the motor. I haven't opened a fuse yet, but having owned 7 Walkera helicopters I have plenty of experience repairing micros.
Questions Is the motor shimmable? Or is it glued in tight? Don't want to do surgery on my new UM T-28 unless I can adjust the pitch of the prop shaft.
Mike
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Old Jul 14, 2012, 01:07 PM
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rccessna's Avatar
USA, TN, Collierville
Joined Jan 2009
29 Posts
T-28 tail wheel?

I just did this for hoots and it actually flys great! It gets off the ground quicker too.
the tail wheel is one off of a j-3 micro, just remove the nose wheel and move the gear all the way out to the leading edge. Add the tail wheel and BOOM your done!
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Old Jul 14, 2012, 02:34 PM
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United States, PA, Butler
Joined Jun 2006
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Quote:
Originally Posted by shastamike View Post
Also, I'm wondering, instead of adding weight to the nose to correct this maybe I should do a elevator>throttle mix to correct the tendency to stall and hover with throttle increase? Thanks.
Mike
The throttle/elevator mix works great if you want to fly a balanced airframe at full throttle without climbing, I have it in my UM T-28 and switch it on/off as wanted. That isn't what you want to do with your problem. It is just a way of flying straight and level at full throttle when you want to. Airplanes climb with throttle naturally, just not to the extent you are describing.

For the record, I've had my Trojan for over a year now and have had a Canadian dime glued inside the nose since getting it. I couldn't control it, nor could I get level flight without the dime weight. Everyone told me the same, I don't need the weight in the nose, but my experience is, the airplane is all over the place uncontrollable without it and with the dime, I fly nice, stable, and slow at 3 inches of height above the ground every night through my yard.
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Old Jul 14, 2012, 02:43 PM
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United States, CA, Mt Shasta
Joined Jun 2010
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Quote:
Originally Posted by mrodgers View Post
The throttle/elevator mix works great if you want to fly a balanced airframe at full throttle without climbing, I have it in my UM T-28 and switch it on/off as wanted. That isn't what you want to do with your problem. It is just a way of flying straight and level at full throttle when you want to. Airplanes climb with throttle naturally, just not to the extent you are describing.

For the record, I've had my Trojan for over a year now and have had a Canadian dime glued inside the nose since getting it. I couldn't control it, nor could I get level flight without the dime weight. Everyone told me the same, I don't need the weight in the nose, but my experience is, the airplane is all over the place uncontrollable without it and with the dime, I fly nice, stable, and slow at 3 inches of height above the ground every night through my yard.
I believe I read your post about the dime. Have you looked at your prop shaft orientation? Once I heard that the cowl is not square on the front (the nose) and that the disk that the prop makes spinning should follow the angle of the nose it's easy to see. With my prop horizontal the distance from the nose to each blade is the same. With it vertical the prop is 2mm closer on top then the distance at the bottom. Nice to hear that I'm not the only one, sorry you had to modify.
Still the question: Is the motor glued in solid or is there a way I can shim the motor downward to get the proper shaft pitch?
Mike
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Old Jul 14, 2012, 03:25 PM
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United States, NE, Bennington
Joined Jan 2010
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The stock motor is glued in. You will need to open the fuselage, use a knife to cut the motor assembly loose, and then glue it back in with the correct angle.
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Old Jul 14, 2012, 05:12 PM
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Rcflyyer1's Avatar
United States, FL, Sarasota
Joined Dec 2010
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Just got one myself to fly up north in the summer. It's too hot in Florida. Does anyone know how to transport this on an airplane? I don't want to ship the plane there as I live in a condo.
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Old Jul 14, 2012, 06:04 PM
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United States, CA, Mt Shasta
Joined Jun 2010
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Originally Posted by Rcflyyer1 View Post
Just got one myself to fly up north in the summer. It's too hot in Florida. Does anyone know how to transport this on an airplane? I don't want to ship the plane there as I live in a condo.
What I know is that Li-Po batteries have to be carry on. If something happens to the batteries in flight they like to be able to take care of it as opposed to being locked up, Un-acessable in the luggage bay. The batteries should have tape over the connections to protect from shorting. The plane is up to you. They don't have any problems with the TX. I'd worry about having the plane smashed in baggage check. The airlines all have rules about battery transport on their website. I've transported RC helis on planes with no problems. Now just try to bring back a bag of sand from San Diego, good luck. That gets very special inspection, including a spectro analysis for bomb stuff.
\Mike
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Old Jul 14, 2012, 09:55 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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Re cutting the motor loose... I was replacing the whole assembly but, if you just need down thrust, I'd try partially cutting the motor away, from the aft end and stick in 3/8-inch tips, cut from wooden toothpicks and coated with some RTF Silicone. I've been using the silicone to great effect, when installing the motors in several planes, powered by the same motors.
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Old Jul 14, 2012, 10:15 PM
that's gonna leave a scar
KCinNC's Avatar
Marina Village, NC
Joined Aug 2007
3,289 Posts
Quote:
Originally Posted by davidterrell80 View Post
Re cutting the motor loose... I was replacing the whole assembly but, if you just need down thrust, I'd try partially cutting the motor away, from the aft end and stick in 3/8-inch tips, cut from wooden toothpicks and coated with some RTF Silicone. I've been using the silicone to great effect, when installing the motors in several planes, powered by the same motors.
i agree, no need to rip the whole motor & mount out ! just lift the back of the motor mount a tad
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