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Old May 19, 2012, 12:44 PM
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United States, VA, Winchester
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Quote:
Originally Posted by bobly View Post
I'd try rubber band replacement for starters. Don't completely understand what you are describing, but the Apprentice is actually quite aerobatic and will do plenty of tricks. I have 3d planes also, but for sure have not developed my skill beyond the capabilities of the Apprentice. We have some really good pilots that still fly the apprentice and really like it. And just in case it hasn't been mentioned, do not leave the rubber bands on it between uses, they get stretched out much worse, much quicker if you do. If changing the rubber bands don't fix it, you might get someone with more experience to check it out.
Yeah I will definately check the rubber bands. I leave the bands on for the afternoon while I am at the flying field, but I take them off when I prepare to leave the field and leave them off when the plane is stored at my house in between outings to the field. I did have a seasoned flyer take a look at it, but he was not real sure what the issue could be being caused from. He said he has never owned an apprentice so that is why I figured this would be a good place to start.

As far as what the plane is doing its kinda hard to put into words. I wish I had a video camera so I could post a video for you all to see for yourself. But basically at the bottom/end of the loop after I have let off the back elevator on my transmitter the plane will start back into a loop on its on by pointing the nose of the plane vertically straight up. I have checked and double checked the elevator while on the ground so I know the servo is not getting stuck or anything. Just before I flew the apprentice I had flown our club training which is a Mentor 82" wingspan trainer and it preformed beautifully.
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Old May 21, 2012, 10:17 PM
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Norcross, GA
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These are the best rubber bands for the Apprectice.

http://www.advantagehobby.com/58785/HBZ7127/
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Old May 21, 2012, 10:50 PM
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Quote:
Originally Posted by lawguy14 View Post
...The last couple flights I have noticed that when I do a backwards loop and then roll out of the loop, the Apprentice will still pitch straight up as if I had not let off the back elevator. I am really kind of irritated with it right now and hoping someone has heard of this before and can offer some help...

...Any ideas?
Coming out of the back side of a loop will increase speed as the plane dives. The Apprentice has a lifting airfoil, not symmetric (as is found in most true aerobatic planes), and it also has a positive incidence angle molded into the wing saddle area on the fuselage (i.e. holding the fuselage up, you'll see the height of the wing saddle's leading edge is higher than the trailing edge when using the stabilizer as a reference line)

Lifting airfoil + positive incidence angle + speed == what you're seeing.

Backing off the throttle as you come around the top of the loop will help reduce this ballooning tendency by reducing the speed of the dive.

There are some ways to mitigate this behavior and make the plane more acrobatically oriented and less trainer'ish. You can shim up the trailing edge of the wing and mute some of that positive angle that contributes to the ballooning. Experiment in small increments of say...1/16" here. Some tapered balsa shims the length of the wing saddle area will keep the rubber bands from bending the foam.

You can add "reflex" to the ailerons. This is where at neutral, BOTH ailerons will have their clevises adjusted so they're kicked UP a bit. This will kill some of the lifting tendency of the wing. It'll also help to control ballooning on landing if you flare a bit too early. Again, experiment in small increments. Say with about 1/8" initially.
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Old May 22, 2012, 04:13 AM
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Thank you NACA, that does make sense. I will experiment with that a little. I love how visible this plane is in the sky, but sometimes wish Eflite made more of there other planes this size or bigger, but most seem to be smaller.

I was beginning to think I'd just sell it and go with something more aerobatic, but maybe i'll try a couple of those option.....Thanks again.
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Old May 22, 2012, 06:44 PM
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If you know someone who has a foam cutting bow, it wouldn't be too hard to make a new wing for the apprentice with an airfoil that's more symmetric. There'd be a bit of fiddling around the wing saddle to get the new airfoil profile to mate up with the wing saddle, but that's about it. Nothing that can't be accomplished with a bread knife to cut the foam.

With a close to symmetric airfoil, and a bit larger ailerons the Apprentice's performance should be something akin to an Ugly Stick's. Its got plenty of elevator and rudder area to be fairly aerobatic.
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Old May 22, 2012, 07:48 PM
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With enough throws dialed in the apprentice is pretty aerobatic on it's own. In stock trim, mine takes almost no down elevator to fly level inverted where a stock t28 takes almost all it can get. Rolls are fairly straight and true, but it don't knife edge worth a hoot, guess high wing trainers just aren't cut out to do knife edge.
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Old May 22, 2012, 08:40 PM
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Well I've got a day off tomorrow and with any hope it won't be raining in the morning so I am going to give her a try with some new rubber bands and see if that changes anything. I'll keep you all posted as to how that goes
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Old May 22, 2012, 08:46 PM
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Someone recently gave me a foam T-28 wing to repair, and looking at it, I'm seeing a pretty healthy dose of washout was molded in. I've never looked at the incidence angle on one of them, but I'm guessing it probably has some positive molded in.

If you've got a junker you're willing to experiment with, changing the incidence angle should make a difference on the T-28's inverted flight.
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Old May 22, 2012, 10:00 PM
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Your correct .... no more molding .... glad we can now flip a switch and get similar characteristics ....
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Last edited by immelguy; May 22, 2012 at 10:39 PM.
Old May 23, 2012, 12:07 AM
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Yep, with a dedicated channel per aileron servo, all sorts of different performance configurations are possible and programmable to the various switches.

Mapping some reflex trim to a switch designated as "landing mode" would be a big help for a lot the T-28 folks.
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Old May 23, 2012, 02:03 AM
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United States, OR, The Dalles
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As far as high wing aerobats go, you might consider the Rascal. I bummed a flight on a friend's .40 size, and it is really an excellent flier. I now have the 110" one on my build table.
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Old May 23, 2012, 03:41 PM
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Well it must have been the rubber bands. I took some #64 Hobbico bands out there with me today and the plane flew perfectly. I was amazed at how much tighter the Hobbico bands were than the stock ones were that came with the plane. I had to really put some effort in getting the #64's to stretch the needed length. Thanks for all the input guys.
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Old May 23, 2012, 05:40 PM
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I don't know what vintage your Apprentice is, but earlier one's I've seen had issues with the plastic thingamabobs the bands attach to pulling out when stouter bands were used. Apparently they didn't go all the way through like a long dowel would. I don't know if this was rectified with any manufacturing revision.

I just tugged pretty hard on the ones that are in one I'm assembling for a friend and they seemed fairly solid (for the moment). His was bought a few days ago though, not a few years ago.
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Old May 23, 2012, 09:12 PM
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I purchased mine a month ago and I also used some CA around the edges to reinforce them
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Old May 24, 2012, 01:56 AM
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I think mine has CF tubes across the fuse for the knobs. They have been solid.
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