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Author Topic: Help with indoor duration helicopter  (Read 10784 times)
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PiperCub49
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« Reply #125 on: January 31, 2011, 09:52:18 AM »

Thanks, Bill. I'll check it out when I get home tonight. Have you been keeping up with Bill Carney's build on Yahoo Groups? Here is his video: http://www.youtube.com/watch?v=lqV_y-CSznM
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Olbill
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« Reply #126 on: January 31, 2011, 04:14:21 PM »

Yep I saw it. More salt in the wounds!
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PiperCub49
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« Reply #127 on: January 31, 2011, 04:33:14 PM »

Yep I saw it. More salt in the wounds!

I know! It's really starting to burn!

I'm trying to find my next step, so I've been on the hunt for some ideas and inspiration. We are not totally off the rocker with the flat pitch design. These two sites have given me a few ideas. http://gallery.scioly.org/categories.php?cat_id=68 http://www.youtube.com/watch?v=A6LHxF2hIWE&feature=related

I think that I'm going to try stiffer rotor blades, more area, and more power. I'll see where that takes me and go from there.

Kang and I were also talking about the "style" of flight. The helicopter is naturally more efficient in a hover because the thrust is just enough to keep the thing in the air. However, because of the change in motor torque and rules against VPPs, it is unlikely that a perfect hover possible, not to mention getting the thing stable enough laterally to stay in one place. A ceiling walker is probably easier (Sorry, Bill. I don't know why yours is being such a pain here.), but there is quite a bit of energy wasted in pushing against the roof.

Anyway, I'll see if I can get something to actually GO UP before I worry too much about that.
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PiperCub49
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« Reply #128 on: January 31, 2011, 05:05:35 PM »

Bill,

I have a couple questions for you, or anyone else that can help, for that matter.

1) Are you flying your helicopter at the full 6g? I'm flying mine at ~5.3g and I still can't get it to rise.
2) Here's the big question: What are you using for an airfoil? I placed the apex of my airfoil 1/3 back from the LE and that apex is 2.5mm above the lowest point on the rib (e.i. the imaginary line connecting the LE and TE of the rib).

I have to ask particularly about the airfoil because it sounds like it's the only unspecified difference between your successful helicopters and my, well, not so successful helicopter.
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Olbill
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« Reply #129 on: January 31, 2011, 05:57:17 PM »

If you're talking to me I think "successful" is a stretch!

Anyway I used an arc airfoil with 12" radius and a 3" chord. And yes I flew it with full 6g loading. I'm going to start a new one maybe tomorrow.
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PiperCub49
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« Reply #130 on: January 31, 2011, 07:45:05 PM »

Now that I have a plan, I'll start my new design tomorrow as well.

I'd say that your 85 seconds is more successful than my 5!
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Olbill
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« Reply #131 on: February 08, 2011, 03:57:07 PM »

News flash!!!! My helicopter flies!!!

I had several pretty successful flights today close to a minute in my 9' ceiling. Most flights ended when the copter hit too many times and got going sideways. When the torque dies off too much to climb it hovers and gradually sinks. Here are some of the specs:

Rotor blades taper from 2" to 3", 12" radius arc airfoil, no twist, all blades set at angle of 8 degrees.
Ballasted total weight 4.01 grams
Motor 2 grams 1/8" 7/02 Tan2, 1200 turns, .6 in-oz launch torque

The copter will climb or hover until the torque is down to .25 in-oz.
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Art356A
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« Reply #132 on: February 08, 2011, 06:20:27 PM »

I just finished a Carney Copter last night and took it out to the gym this morning. I'm sure it's not as light as the original, but it's a performer. It lacks the rocketship climb that Bill's has, but the stability and self-righting action is there. So far I've only run 500 turns, but the less time it spends playing in the trusses the happier I am.

Art.
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My arms are so weak, it's like that pushup I did last year was a total waste.
PiperCub49
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« Reply #133 on: February 12, 2011, 08:21:42 PM »

Hey Bill,

Any trick to cutting the progressively smaller ribs or do you just draw them all out?
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Olbill
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« Reply #134 on: February 12, 2011, 08:28:03 PM »

I cut all of them from a sheet of wood a little larger than the longest rib and then trim to the length needed. Tomorrow I'm helping a student build a copter from the Freedom Flight kit and we'll fly both to see how they do in the gym.
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PiperCub49
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« Reply #135 on: February 12, 2011, 08:36:52 PM »

I cut all of them from a sheet of wood a little larger than the longest rib and then trim to the length needed. Tomorrow I'm helping a student build a copter from the Freedom Flight kit and we'll fly both to see how they do in the gym.

Duh! [Hit myself on the forehead.] Thanks, Bill.

Please let us know how the Freedom Flight kit works out!

-Kody
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Olbill
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« Reply #136 on: February 13, 2011, 01:07:22 PM »

The kit looks really nice. The first hour or so is used building jigs for the rotors and the covering cradles. The helicopter is in progress.

On the down side I tried to demo my copter for the new builder and it would do nothing except crash.
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Olbill
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« Reply #137 on: February 13, 2011, 04:03:09 PM »

Sebastian outlasted me today. I had to call time after 4 1/2 hours. He completed the two rotors today. Hopefully in our next building session on Tuesday night he can finish the copter. The pics below show Sebastian trimming the mylar on one of the rotors and the 2 finished rotors.
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PiperCub49
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« Reply #138 on: February 13, 2011, 04:30:25 PM »

Bill,

Awesome shots! It looks like he's making more progress than I am. Roll Eyes

Last night I cranked out another set of blades. I used 1/16" balsa and the old #11, so the split ribs went far easier than before. Once all of the ribs were cut, it took about 15 minutes per blade. Tomorrow I should be able to cover them and possibly get the spars ready to go.

-Kody
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Olbill
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« Reply #139 on: February 14, 2011, 04:53:28 PM »

Here's a pic of my latest copter. I made an 18" MS from 1/4" x 1/4" balsa. The hooks are 10" apart. For the bottom rotor I made a movable saddle that lets me locate the bottom rotor anywhere on the MS. Also, the saddle locates the center of the bottom rotor in line with the center of the upper rotor - at least it would have if I had put it together right.

With the bottom rotor near the bottom of the MS (and put on incorrectly) the copter did the following flight in my house:

http://www.youtube.com/watch?v=1WCB5_FoODc

Also changed for this flight was a move to a lighter motor. This one is 9" x 1.5g. It's a 4 strand motor because I had a piece of rubber already cut that worked that way.

The flight time was 1:00 until the crash into the wall, then 1:25 to the end of the second segment, then 1:40 at the final crash.
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Aeronut
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« Reply #140 on: February 14, 2011, 05:30:45 PM »

As a tribute to the many AJ Ceiling Walkers that I flew as a youth I made a little 6" micro version! It will fly in my living room or zoom up to the top of our local 40' gym and scarily dance among the lights and beams Smiley Best time is about 25 seconds. A sort of model of a model! Bill
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Olbill
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« Reply #141 on: February 18, 2011, 10:55:18 PM »

We flew the Freedom Flight copter and the one I made tonight. The FF copter flew great from the first flight. It would plant itself on the 30' ceiling and stay there until the power dropped then it would take 15 or 20 seconds to flounder down to the floor. Several flights were over 1:40 with the best at 1:53. It would take .8 in-oz of launch torque without a problem but a little more would make it unstable at launch.

Mine was very sensitive to launch torque and would only handle about .5 in-oz. It never made it all the way to the ceiling but still did a best of 1:52. Photos and video after I recover.
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Olbill
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« Reply #142 on: February 28, 2011, 03:37:07 AM »

On Saturday, Feb 26 Sebastian won his regional helicopter competition with a time of 1:45.

There have been some extremely high times (6 1/2 minutes in Indiana) done in other regionals by stopping the top rotor at the ceiling, hanging there while the bottom rotor winds down and then falling to the floor. Hopefully this strategy will be outlawed for the state competitions. In AMA competitions both rotors must remain turning for the whole flight.
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« Reply #143 on: March 01, 2011, 12:29:24 PM »

My photos and video from helicopter practice came out very bad so I never posted them. I'll try again when Sebastian starts practicing for the state competition.
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PiperCub49
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« Reply #144 on: March 14, 2011, 11:47:44 PM »

Well, after weeks of tinkering, I have nothing to show for it. I followed Bill's blade design and placement. I have the Teflon bearing. I finally made my torque meter so that I actually have an idea of what the heck I'm getting for power. In the entire range between .65 oz. and .2 oz. of torque, the thing will just slowly decent. From about .4 oz. down it is quite stable and will slowly descend straight down, but I CAN'T GO UUUUUP! With only a couple weeks left, I'm feeling very uneasy. I don't know where to go next. It's not like a can't reach my goal time here. I don't even have something that flies yet. -sigh-

-Kody
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« Reply #145 on: March 15, 2011, 12:02:41 AM »

Lousy luck Cody after all that experimentation. However you are close if its stable. Assuming your blades are holding their twist under power and the torque reading is accurate and comparable to OldBills then your heli is heavy.

My advice would be to check its weight and ensure the blades are not flattening out under power. The blade LE should be quite stiff to resist bending and twist. Perhaps a spiral tissue wrap on the LE may help.

Good luck
John
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PiperCub49
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« Reply #146 on: March 15, 2011, 12:34:37 AM »

John,

I think the blades are twisting. I'm only at 3.0g-3.5g, so weight isn't the problem. I'm using 1/16" 8lb. C-grain for the LE. It may not be enough.

By spiral wrap tissue, do you mean wrap the tissue around the LE or am I way off? That's a new term for me.

Thank you for the continued support!

-Kody
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« Reply #147 on: March 15, 2011, 01:05:56 AM »

Kody,

If you can post a video, perhaps some of us can detect the problem. Some picture of the model would be good -- especially if we can see the rotor clearly.

Tell us the motor you are now using. When you wind it to .65 in-oz, how many turns are you putting in?

Another issue is the pitch of your rotor -- perhaps it is too high, and the motor doesn't have enough torque to produce the needed thrust.

-Kang
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« Reply #148 on: March 15, 2011, 01:31:22 AM »

John,
By spiral wrap tissue, do you mean wrap the tissue around the LE or am I way off? That's a new term for me.

Yes that's right.
The idea is to wrap a narrow strip of tissue while rotating your LE stick , feeding the tissue on at an angle of around 30-45deg. apply a thin wipe of PVA to the stick before applying and add the tissue while the glue is still wet. Its a similar technique to rolling paper tubes around a mandrel.

It would need to be done before adding the ribs to build the blade - so you need to smooth the paper as much as possible.

Weight it down and allow to dry over night to avoid warps.

if you are using only 8lb balsa it may be better to just use a harder strip and taper it to the tip.

However I would follow Kang's advice first.

Cheers
John
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PiperCub49
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« Reply #149 on: March 15, 2011, 07:44:12 AM »

Pictures and video are no problem. I'll get some tonight and get posting.
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