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TheOldGuy
2 Posts |
 Posted - 10/13/2006 : 12:41:40 PM
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> I've been flying fuel models for 40 years, but just recently got interested
> in sailplanes as a result of the incredibly poor construction of the ARF's
> out of China and realizing what the beauty of flight is all about (I've seen
> the light, so to speak).
> I'm starting with a UpStar from GP and strangly enough, it went together
> perfectly...first ARF in 10 that was complete and didn't need revisions!!
> The problem is in the balancing.
> The wing is 7" wide and they call for a 2.5" CG which required 5-1/4oz
> weights to balance. When I tried the recommended no power glide,
> it went out about 5' in an arch and nosed down (nothing broke). I tried a couple more times with the same results, it's very noise heavy.
I went back and attempted the 40-50% CG point recommended by Gordy and this time I would have had to add another 3-4 more weights. I can't move the battery or receiver back any further because they have a servo tray mounted in the back and there's no more room. The worry is, how much can you hang on the tail before it won't fly at all?
>
> Thanks for your help,
>
> Charlie
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Edited by - TheOldGuy on 10/13/2006 12:58:15 PM |
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aeajr
477 Posts |
Posted - 10/13/2006 : 1:52:50 PM
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quote:
Originally posted by TheOldGuy
> > The problem is in the balancing.
> The wing is 7" wide and they call for a 2.5" CG which required 5-1/4oz
> weights to balance. When I tried the recommended no power glide,
> it went out about 5' in an arch and nosed down (nothing broke). I tried a couple more times with the same results, it's very noise heavy.
I went back and attempted the 40-50% CG point recommended by Gordy and this time I would have had to add another 3-4 more weights. I can't move the battery or receiver back any further because they have a servo tray mounted in the back and there's no more room. The worry is, how much can you hang on the tail before it won't fly at all?
>
> Thanks for your help,
>
> Charlie
Charlie,
Let me see if i can help.
The key point I pick up in your post is that the plane went out in a arch, then dropped. A no power hand throw should not be in an arch, or it will induce an almost immediate stall. A hand throw should be out flat, or even slightly down so that the plane can pick up speed and the wing can attain good lift.
When I work with new glider pilots, glow pilots or parkflyer pilots who have never done hand launches, there is a tendancy to throw the plane up, but this is wrong. Since you have been flying gas and glow, perhaps you have not done many hand throws so you may be doing the same thing.
You need a firm thow, straight out or slightly down, directly into the wind. Don't think javaline, think darts. And don't think you have to strain to do this. I can toss my 60 ounce 3M Thermal Dancer for a stand with just an arm throw and it will go out a good 150 feet. It leaves my hand flat and just floats away from me. Firm, solid, but don't throw a fast ball. ;)
The plane should leave your hand and glide away in a fairly flat glide. It can not climb as it has no power source, so if it does pick up the nose you have to immediatly push it to level, or slightly down, then to level or it will stall and crash.
If it tends to pop the nose up, chances are you have too much up elevator trimmed into it. This can be due to a miss allignment or it could be because the h-stab is slightly up in the back. I had this on my 2M Spirit at one time. After getting it to glide nice, I noticed that I had down elevator trimmed in. The stab was up. I removed it, sanded the fuse and put it back. No more down elevator trim and it glided much further.
The other point I will make is that plans normally recommend an inital nose heavy condition. Typically I will use their forward balance point, then move it back over a period of 10-20 flights till the plane gets "twitchy" then try to move it forward just a hair.
Over time, as I get used to it, I may start to push back again and find that I can now handle the plane with a more rearward CG.
As to how much you can put on the tail. I would recommend you test the glide approach I sugget above and see if you get better results. Don't pull any up elevator during the hand glide. I always do my early glides over tall grass if I can.
If you added 5 1/4 oz of weight to the nose, you have plenty of opportunity to take out weight before you need to add to the tail. I would suggest pulling weight about 1/2 oz at a time. However, even if you have a nose heavy condition, and your stab is right, you should be able to get a 50-100 foot glide with no problems. That may be too nose heavy for optimum flight but it should not be too nose heavy for an inital test glide.
I had a friend who brought his 2M Cirrus glider to the field for trimming. We did a test glide. Looked a little nose heavy but it flew. But when we put it on the hi-start the plane launched too flat. So we pulled weight. After pulling .5 oz 3 times we had 150 foot hand glides and 60 degree launches. The plane flew well and he could handle it.
Chances are we could have pulled another .5 to one ounce but that was enough movement for one day. He was happy and caught some nice thermals that day.
Let me know if I have hit some possible points that could be helpful.
Best regards,
Ed Anderson
ESL Content Editor
aeajr on the forums
Long Island Silent Flyers |
Edited by - aeajr on 10/13/2006 1:56:45 PM |
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aeajr
477 Posts |
Posted - 10/13/2006 : 2:03:02 PM
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Charlie,
Since you have been a power pilot, perhaps this will help. It is written for electric parkflyer pilots but maybe it will ring a familiar note. Of course you glider is not going to gain altitude so the up elevator should only be used if YOU made a mistake and trew the plane at too much of a down angle. Then all you are trying to do is minimize the crash.
THROWING UP WILL MAKE YOU SICK!
Many, perhaps most of the small electric planes can be hand launched. Many
don't even have landing gear. I take the landing gear off as it tends to
grab in the grass and flip the plane over on landing. I belly land all of mine.
Let's take a look at that hand launch as it can be troublesome for new
flyers.
Always launch into the wind. ALWAYS!!!! No exceptions! If the wind is not
blowing into your face, you are facing the wrong way.
Motor at FULL throttle. Remember, if you throw-UP, that will make you sick.
You want to send it straight out.
Your plane may actually lose some altitude as it gains speed. As long as the
wings are level and the plane is flat, that is fine. The plane should look
like it just flew past you, not like it is climbing, at least not right
away.
Don't pull back on the elevator till it is up to speed. Maybe a TINY bit. It
should start to regain that altitude all on its own as the lift of the wing
kicks in. Until that happens, a big pull back on the elevator is like
putting
on the brakes, and it will slow the plane down, the wings will lose lift and
it will stall and likely fall to one side or the other, especially if you
haven't thrown it with the wings level.
Stall?
Think of it this way, if you throw the plane up, it is like starting to ride
your bicycle up hill in high gear from a standing start. VERY HARD to do.
Better to start on level ground in a lower gear, get up some speed, then
attack the hill. Same for your plane.
If you throw up, the plane can not gain speed fast enough and the wing will
not get up to minimum flying speed. Getting a firm, flat, wings even throw
takes some work. Send it out like a big dart you are tossing at a board on
the
wall.
Try this visualization:
Stand under the goal post of a football or soccer field. With the motor at
full power, throw it straight out so it will fly under the cross bar of the
other goal post.
Under the other goal post? Yes under!
That should give you a nice flat throw! If you are trying to throw it OVER
the
goal post, you are tipped up too much. Strong firm, flat throw, not up, or
only slightly up. Those wings need to be flat to gain lift. ( Don't worry,
by time it reaches the other end of the field it will be much higher than
that cross bar, but don't try to throw it over the bar. Let the plane do
it.)
This tendency to throw up is a very common mistake that lots of new flyers
make. You will crash and crash and crash and that will just make you sick!
Remember: If you throw-up, it will make you sick!
I recently exchanged messages with a new pilot. He was having
terrible problems. Happens that he lives near me. Brought the plane to me.
After checking it out, I launched the plane. The plane flew perfectly. In
fact
I set it at full throttle, threw the plane and then stretched my arms out
wide
so he could see I was not touching the controls.
Turned out he was throwing UP at about a 45 degree angle. Now he does it
right, flies in 10+ mph winds and is teaching his brother how to fly. He
also
became a member of our club.
So, is your hand launch making you sick?
Best regards,
Ed Anderson
ESL Content Editor
aeajr on the forums
Long Island Silent Flyers |
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aeajr
477 Posts |
Posted - 10/13/2006 : 4:20:45 PM
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Charlie,
A couple more quick items.
1) make sure your ESC, electronic speed contorl has a break feature and that you have it set. If not, the propeller will not fold and will create a huge amount of drag if it keep spinning. The difference can be dramatic.
2) The recommendation is for 1800 mah NiMh batteries and that should be fine. You can probably get these in A size or 5/4A rather than Sub C. That will be ligher than an 8 cell Sub C pack.
3) If you don't mind going Lithium, you can get 3 cell 2100 mah lithium packs that can handle 25 amps which should be more than enough for that motor. This again can drop the weight. Just be sure that your ESC can handle 3 Lipo cells or 12 NiMh cells.
4) If you go with Lithium adn your ESC has an automatic LVC, low voltage cut-off, be sure it can be set for no no lower than 8.5V or you can damage the Lithium cells.
Good luck with your new plane. Let us know how it goes. ;)
Best regards,
Ed Anderson
ESL Content Editor
aeajr on the forums
Long Island Silent Flyers |
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aeajr
477 Posts |
Posted - 10/31/2006 : 8:17:16 PM
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Charlie,
How is the plane flying?
Best regards,
Ed Anderson
ESL Content Editor
aeajr on the forums |
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TheOldGuy
2 Posts |
Posted - 12/22/2006 : 6:06:35 PM
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I solved my problem with the Upstart glider, I'm replacing the motor, ESC, battery and prop assembly. The motors that come with these gliders, are cheap, very,very heavy and if you don't use a lipo battery, the orginal is far too heavy. I'll let you know how it goes.
Charlie |
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aeajr
477 Posts |
Posted - 12/22/2006 : 6:32:43 PM
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Thanks for the update.
I have read similar reports elsewhere. What are you going to put in?
Best regards,
Ed Anderson
ESL Content Editor
aeajr on the forums |
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Balancing Problem
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