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Old Jul 08, 2012, 10:54 AM
Power Wheels Guru
UNGN's Avatar
Southlake, TX
Joined Jan 2008
7,327 Posts
Using 2.2 or even 1.7g Servos and an R415 RX would save about 6g... A 60g plane doesn't need 4g servos.

Removing the bellcrank and connecting direct to the servo arms would save another gram.

Doing it that way is good if that what you have on hand, but if you are are going to have to order stuff anyway....
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Old Jul 09, 2012, 07:09 AM
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United States, PA, Butler
Joined Jun 2006
1,000 Posts
Quote:
Originally Posted by KCinNC View Post
i just did a second BL conversion....didn't use any of the stock electrics..
Is that carbon spar on the wing continuous through the fuse? I want to flatten out my wings and strengthen them. The strengthening isn't as important as I don't fly that way, but beings one wing is nearly straight from a complete rip and reglue at the root and the other non-ripped wing is at a larger than stock angle, I want to flatten mine. I imagine it would fly nice with a flattened wing, or would it not bank with ailerons? (I can't get mine to bank to the left, but the left wing is the one bent at a larger dihedral angle than stock through wear.)
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Old Jul 09, 2012, 11:15 AM
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Chile, Araucanía, Angol
Joined Jan 2012
367 Posts
Without rudder you lost 50% of fun. With it you can do more than taxi the plane.

Regards!
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Old Jul 09, 2012, 02:15 PM
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United States, CA, Mt Shasta
Joined Jun 2010
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My T-28 flys very tail heavy. My battery is all the way forwards. I thought maybe that it was because of me not using the landing gear. I added the nose and wing wheels, it helped a bit but I still have to trim the elevator almost all the way forward. Some say to add weight to the nose, but I wonder if I shouldn't mechanically trim it with the wire loop at the elevator horn. I just can't see adding weight to the plane. The elevator surface is flat and so are the ailerons. any ideas?
Mike
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Old Jul 09, 2012, 03:28 PM
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McCarthy, Alaska
Joined Jun 2004
1,133 Posts
It sounds like your plane may actually be tail-heavy. If so, then the proper cure is to balance it, using weight on the nose or a heavier battery. The control surfaces should be flat with zero trim. Only bend the wire hoops to obtain that characteristic (as a general rule, not an absolute one)

search for CG or balance in this thread and you should find some posts of how others have made simple testers to check the balance.
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Old Jul 09, 2012, 03:35 PM
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McCarthy, Alaska
Joined Jun 2004
1,133 Posts
Quote:
Originally Posted by KCinNC View Post
i just did a second BL conversion....didn't use any of the stock electrics..
I think my (second, this one a solo-pro) motor is going. I am thinking of a similar conversion. Can you point me toward some detail on your motor mount?

Thanks
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Old Jul 10, 2012, 07:06 AM
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United States, NY, CENTRAL VLY
Joined May 2011
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On a whim I bought a T-28 airframe from Phils. My T went to my son last year to train, so it's hurting right now.

I forgot how much I love this plane. I had about an hour and half of pure fun last night. Ran through all my batteries and it was getting too dark to see. I think I'll add some nav lights today and bring more batteries tonight.

I set it up with a 5043 prop on a SP motor, Hyperion 240s and it really shines.
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Old Jul 10, 2012, 09:47 AM
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Horsham, PA
Joined Aug 2007
126 Posts
I have had my T-28 since late last fall and have not made any modifications. However, I have recently noticed that I have matching creases on each wing. Several people in this thread have recommended strengthing the wings with a carbon spar. I taped a 2mm carbon rod the underside of each wing and tested the plane this morning. Wow, If you have not done this, do it now. Rolls are much crisper and consistent. An easy and needed modification.
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Old Jul 10, 2012, 10:12 AM
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Canada, ON, Calabogie
Joined May 2011
261 Posts
Quote:
Originally Posted by impmotor View Post
I have had my T-28 since late last fall and have not made any modifications. However, I have recently noticed that I have matching creases on each wing. Several people in this thread have recommended strengthing the wings with a carbon spar. I taped a 2mm carbon rod the underside of each wing and tested the plane this morning. Wow, If you have not done this, do it now. Rolls are much crisper and consistent. An easy and needed modification.
My T28 wings collapsed on 2S BL power
I reinforced my wing with carbon fiber and got a new plane.
Wow! It's a must do!!!!
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Old Jul 10, 2012, 10:57 AM
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United States, NY, CENTRAL VLY
Joined May 2011
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I third that.

When I assembled the new airframe, first thing I did was tape Cf rod along both leading edges. I do it with all my UMs right out of the box, even the F4U.

Besides stability, it saves the wing. I flew it into a set of bleachers and a chain link fence (twice) last night, no damage whatsoever. Cartwheeled it too getting fancy, again, no issues. Before the mod, I would have had a mess of tape on it by the end of the night.
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Old Jul 10, 2012, 11:28 AM
RC pilots do it in the air
marke14's Avatar
Joined Dec 2011
114 Posts
msdumo, and others who use a CF spar on the main wing:

Do you use one long piece of CF and "poke" it through the main fuse? If so, do you put a slight bend in it or is this how you straighten the wing out? Any tips on getting it to poke through straight?

Same question applies for the spar on the horizontal stab - poke it through? I'd imagine it would be easier as the fuselage is much narrower back at the tail.

msdumo, also one more question for you - on your 2S conversion post, I see that you mentioned that you used a diode. I don't know that much about electronics (but I'm learning!), but I looked up what a diode is and its function, and I read that a diode works like an electrical "check valve", i.e. it allows current to flow in only one direction.

Is a diode necessary for the 2S conversion, or are you just playing it safe?

Thanks in advance. I really love my UM T-28, like others have said, I have many planes (I am up to 5 now, holy smokes!) and I am most proficient with, and enjoy flying the UM T the most of my fleet.

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Old Jul 10, 2012, 12:50 PM
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Kokomo, Indiana
Joined Jun 2008
758 Posts
Quote:
Originally Posted by marke14 View Post
msdumo, and others who use a CF spar on the main wing:

Do you use one long piece of CF and "poke" it through the main fuse? If so, do you put a slight bend in it or is this how you straighten the wing out? Any tips on getting it to poke through straight?

Same question applies for the spar on the horizontal stab - poke it through? I'd imagine it would be easier as the fuselage is much narrower back at the tail.

msdumo, also one more question for you - on your 2S conversion post, I see that you mentioned that you used a diode. I don't know that much about electronics (but I'm learning!), but I looked up what a diode is and its function, and I read that a diode works like an electrical "check valve", i.e. it allows current to flow in only one direction.

Is a diode necessary for the 2S conversion, or are you just playing it safe?

Thanks in advance. I really love my UM T-28, like others have said, I have many planes (I am up to 5 now, holy smokes!) and I am most proficient with, and enjoy flying the UM T the most of my fleet.

Quick reply regarding the diode. Your definition is correct. In addition, when forward biased a diode has the characteristic of a fixed voltage drop across it. Anywhere from 0.3 to about 0.8v depending on which type of diode used. This is the characteristic being used to drop the 5v from the ESC regulator to about 4.3v to power the Brick. The Brick is not designed for voltages above about 4.2v, of course.
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Old Jul 10, 2012, 01:40 PM
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Horsham, PA
Joined Aug 2007
126 Posts
I did not put the rod through the fuse. Where the wings were flexing was about a third of the way to the wing tip. Since this was the problem I wanted to solve, I taped a carbon rod to each wing a bit back from the leading edge. The only reason I used tape was so that I could remove them easily if I did not like this modification.
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Old Jul 10, 2012, 03:15 PM
RC pilots do it in the air
marke14's Avatar
Joined Dec 2011
114 Posts
Quote:
Originally Posted by CorvetteC5 View Post
Quick reply regarding the diode. Your definition is correct. In addition, when forward biased a diode has the characteristic of a fixed voltage drop across it. Anywhere from 0.3 to about 0.8v depending on which type of diode used. This is the characteristic being used to drop the 5v from the ESC regulator to about 4.3v to power the Brick. The Brick is not designed for voltages above about 4.2v, of course.
Good reply, thank you! Is there a reason to use the diode for this purpose rather than a resistor? Sorry if I am thinking of another component (not a capacitor right, those store energy?).

Could you / is it advisable to do a 2S conversion without the diode?
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Old Jul 10, 2012, 04:06 PM
Registered User
Canada, ON, Calabogie
Joined May 2011
261 Posts
Quote:
Originally Posted by marke14 View Post
msdumo, and others who use a CF spar on the main wing:

Do you use one long piece of CF and "poke" it through the main fuse? If so, do you put a slight bend in it or is this how you straighten the wing out? Any tips on getting it to poke through straight?

Same question applies for the spar on the horizontal stab - poke it through? I'd imagine it would be easier as the fuselage is much narrower back at the tail.

msdumo, also one more question for you - on your 2S conversion post, I see that you mentioned that you used a diode. I don't know that much about electronics (but I'm learning!), but I looked up what a diode is and its function, and I read that a diode works like an electrical "check valve", i.e. it allows current to flow in only one direction.

Is a diode necessary for the 2S conversion, or are you just playing it safe?

Thanks in advance. I really love my UM T-28, like others have said, I have many planes (I am up to 5 now, holy smokes!) and I am most proficient with, and enjoy flying the UM T the most of my fleet.

I used a diode on my 2S BL to reduce the voltage to 4.3 volt for the brick. I have an AP05 motor and a Turnigy 6A Plush ESC in my T28 and a 5030 prop. Using a drop resistor would make this voltage vary as the current to the brick varies. Might work but a diode is easier and will provide a more constant voltage. It also protects the brick from a negative voltage.

I'm into kiting so I used a sliver from a broken carbon fibre tube. It would be around 1 x 4 x 400mm in size. Length is about 1/2 inch shy of each wing tip. I drew a line on the wing through CG point since this adds around 4 grams in weight.
I pushed the carbon through the fuselage and glued it to the bottom of the wing with gorilla glue on the CG line. It took out most of the dihedral in the wing and really flattened the wing out. It still has some dihedral (~ 1/2 inch).

It probably could have been less stiff and a little lighter but I like it. Looks awesome in the air.
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Last edited by msdumo; Jul 10, 2012 at 04:11 PM.
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