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Old Jan 12, 2009, 10:28 PM
Registered User
Texas
Joined Nov 2005
60 Posts
Wing loading

Dag, you are getting a lot of suggestions, and most are sound. But just to give something else to think about which i'm sure you don't need. At 28-31oz wing loading on a plane this size will be like trying to fly a beach ball. I know you want to keep the weight down but you are going to bounce around like crazy. So if you aren't worried about weight I would put the motors where ever they work the best. I have been around some very large model and they fly better with a heavy wing load. You should be able to fly and take off in a couple hunders feet with a wing load of 125 oz. I know you won't be that heavy but the plane will have no problem.
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Old Jan 12, 2009, 10:29 PM
Registered User
USA, VA, Alexandria
Joined Oct 2004
351 Posts
Use green 620 loctite for bearing retaining if you are going to attach the bearing to the shaft. The red and blue are for threads. Permatex make a similar product. Why make things difficult machining the shafting. Cut to length and use a shaft coupling with set screws to attach the motor and use a collet for the prop. Everything is in compression so it shouldn't go anywhere. What kind of aluminum did you use? Some aluminum is very soft and I would expect damage if there is vibration. Was it damaged during your unbalanced runs? I would go with two middle bearings to make sure there is no flex or whipping. I would also use a steel stub shaft for the props running in a double bearings at the output to support the load. A slightly out of balance prop will give you a nice fatigue cycle on the shaft and aluminum isn't so great in that situation. Good luck.
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Old Jan 12, 2009, 11:34 PM
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Hepdog's Avatar
Stonewall, MB, Can
Joined Jul 2004
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Quote:
Originally Posted by lrb75
Use green 620 loctite for bearing retaining if you are going to attach the bearing to the shaft. .....A slightly out of balance prop will give you a nice fatigue cycle on the shaft and aluminum isn't so great in that situation. Good luck.

Those two comments I understand. Green 620 is pretty good stuff - more or less permanent.

I read somewhere that CF has a fatigue cycle very similar to aluminum - if not shorter and tends to fail more abruptly. I see if I can find the link to the article again. The right kind of steel (alloy) is of course is heavier but will take much more abuse.
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Old Jan 13, 2009, 06:05 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
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Well it was a late night.
After taking everything I have to date and weighing it, then adding what I think things will weigh built up and finished here are my 2 options.

Shafting with a plane that will be about 65 pounds.
Direct drive with a plane that will be about 77 pounds.


Just buy moving all my flight packs to the front will help me off-set a ton of ballast.

These calcs are right down the center, I could be better or worse.

Tonight I will make my new shaft, if this one works and I believe it will, then I will go shafting. Last night I cut up my first shaft and when I machined it I had more problems than I thought, one thing I noticed was the hole in my Zinger is for a 8mm shaft, like what is on my Hacker, the 8mm threaded rod I have has a true OD of 7.87mm. After looking closely I see that the prop was out of balance just from that. After taking a small piece of clear packing tape and wrapping it very tight on the thread and then putting it on my #2 shaft that vibration went down a ton. My #2 shaft is the one that showed where the bearing spun. Tonight I will make shaft #3. If all goes well this will be the one.

But I have to be able to bench run this shafting for a total of 10 4 minute runs, that is what I am setting up my testing around. If I have no wear of the shafting or bearings after that then I should be good to go.

And all the Aluminum I am using is 6061 T-6 .5" thick walled tubing.
Thanks all.

DAG
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Old Jan 13, 2009, 09:15 AM
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Chicago, IL
Joined Nov 1999
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Quote:
Originally Posted by B Sickels
At 28-31oz wing loading on a plane this size will be like trying to fly a beach ball. I know you want to keep the weight down but you are going to bounce around like crazy. So if you aren't worried about weight I would put the motors where ever they work the best. I have been around some very large model and they fly better with a heavy wing load.
This is very true, has something to do with Reynolds numbers. Basically, the bigger the wing, the more efficient it becomes. Large planes fly easily at wing loadings that would never work at all on a smaller plane. As Sickels says, it might actually fly better with the extra weight.
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Old Jan 13, 2009, 10:44 AM
Awsome 2.5D Pilot.
bigbobed's Avatar
Foxfire Village, NC
Joined Nov 2003
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Cubic wing loading is your friend.
http://findarticles.com/p/articles/m...12/ai_n8772261
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Old Jan 13, 2009, 02:34 PM
Team 3DHS
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San Antonio, TX
Joined Sep 2004
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So ignore the advice for more weight. . Looks like a good wingloading / cubic loading for you. She'll land very gracefully that way.
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Old Jan 13, 2009, 03:26 PM
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Chicago, IL
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One thing's for sure, it's easier to build light, then add weight later, rather than try to lighten a plane after it's built.
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Old Jan 13, 2009, 05:24 PM
It only takes one good idea
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Fishers, Indiana
Joined Oct 2004
5,869 Posts
I love all this math. With the wing on this plane it would fly great at 150 pounds . I am not sure if I have already told this story but along time ago in a galaxy far, far, away I did some wing testing. To make a long story short I loaded a C/G cub with about a 75" wing up to about 15 pounds with a bunch of old D-cell batteries. It was powered by a 4 stroke something (did there used to be a Satio 75 or 77?) The plane took off like the Spirit of St. Louis. Very heavy and the climb rate was like nothing, but it flew and once i got up to a 100' she was flying like any other overloaded pig would. I also had a wing that day hot wired of the B-36 airfoil and it had a span of 78", this wing on the cub flew, and did just as well as the Clark-Y did. The next wing I rubber banded on was a fully symmetrical, this time the plane just hoped up and down and would not maintain flight with out stalling a wing and ground looping. After I got home and did some calcs I had wing loads as high as 55 ounces on that cub and it flew, not well but it did fly. I have seen all the calcs for cubic wing loading and it is all spot on, but an airplane really only knows the angle of attach that the wing is flying.

So that was enough about that, IMHO this plane will fly great at anything under 100 pounds.

Another cool thing happened today, I spoke with a great guy Jason Merkle at Thunder Power RC. It is really cool all the other things they do that is outside our RC world. This company really knows Lipo's. They have a standard 8 cell battery that may save me some weight and make setting up my wing for the Lipo's a ton easier.

He is sending me a 8 cell pack to test. I will share how the pack works once I test it with my set-up.

Rock on all.

DAG
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Old Jan 13, 2009, 06:00 PM
War Eagle!
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United States, AL, Huntsville
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Sounds awesome. Looks like we will get to show some more vendor love
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Old Jan 13, 2009, 08:08 PM
HAL... Open the damn doors!
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Miramar, Florida
Joined Jul 2007
8,298 Posts
Quote:
Originally Posted by dag214
Another cool thing happened today, I spoke with a great guy Jason Merkle at Thunder Power RC. It is really cool all the other things they do that is outside our RC world. This company really knows Lipo's. They have a standard 8 cell battery that may save me some weight and make setting up my wing for the Lipo's a ton easier.

He is sending me a 8 cell pack to test. I will share how the pack works once I test it with my set-up.

Rock on all.

DAG
Dag,

Remember what I said on the phone, while they do make 8, 10 and 12S packs, your going to want to get more use out of these packs than this one configuration. Using 2 x 4S packs allows you to run 4S, 8S or even 12S by connecting in series. Obviously you can't look a gift horse in the mouth but I would try and go with 4S packs if possible...

Jack
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Old Jan 14, 2009, 04:38 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by jfetter
Dag,

Remember what I said on the phone, while they do make 8, 10 and 12S packs, your going to want to get more use out of these packs than this one configuration. Using 2 x 4S packs allows you to run 4S, 8S or even 12S by connecting in series. Obviously you can't look a gift horse in the mouth but I would try and go with 4S packs if possible...

Jack
Thanks Jack, But This plane will never fly on a 4S, or a 12S. And what I am gaining with how it will all fit into the wing may be worth it to me. Nothing is set in stone yet, I may still use 2 4S, but 6 flight packs verses 12 flight packs is something to think about. I am still only testing .

And about testing, I took 2 Hackers last night and set one in a firewall with my Zinger, and the other on the new shaft. The new shaft I think is good to go, BUT, when I ran the Hacker on the firewall it was like WOW, this set-up has just about ZERO vibration. It was un-real how smooth it ran. I am still not convinced that adding 9-14 pounds and just sticking these great Hackers on the rear on the nacelle is not the way to go.

And....
Just so everyone knows where I am at, I spent the last 2 weeks looking into how long these packs last and how fast they start to lose how much of a charge they will take. When I am going to have an investment in either 6 batteries or 12 I have to think about what happens after 30, or 50 charges. If I have 6 systems and 2 after 30 charges is down 10% then I will have motors running at all kinds of different rpm's. Now I know I am going to have some of this, but what I am looking at it what is going to be the best investment. I am not going to say who I think has the better packs and who does not, but so far the only 2 batteries that I have had anyone want to show me how well they work are the manufacturer of Thunder Power, and dealer Jim Spice wanting me to see what I thought of Air Thunder. But I do have to say after looking at the history that Thunder Power has with the UAV, and other government projects they do have the experience. No matter what these batteries are going to cost me a ton, but I want to make the investment for what is going to last the longest, and be the most stable. At this time that looks like it may be Thunder Power. I have to have a system I trust.

Thanks, DAG
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Old Jan 14, 2009, 06:30 AM
"NAVY CHIEFS"
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NAF Atsugi, Japan
Joined Jul 2005
628 Posts
Dag,
Here is my 2 cents. If you move the motors to the rear. And but your batteries in the Fuse towards the Nose you would not gain any weight. Like my OV-10 I had to move my batteries from the left and right pylon and move to the center fuse. Ya alot of the big eletric guys say don't make the wires to long. But if you use the correct gauge wire you should be good! Well it's only my two cents. Might be something to look at....

Mike
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Old Jan 14, 2009, 06:40 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,298 Posts
Quote:
Originally Posted by dag214
Thanks Jack, But This plane will never fly on a 4S, or 12S.
Not what I'm saying. I am saying if you get another electric plane (of course you will, if not 10 more!) it will likely NOT fly on 8S. Having packs you can use in other planes is what makes a good LiPo investment from a bad one. Remember, with $5,000+ invested, if I had but one or 2 planes I could use my packs in it would have been because I never thought it through well enough. Instead, my 6S packs can be used in 60 to 90 sized planes and run in series for the larger 2 meter planes, I can parallel them for 30%+ as well. Just a thought, being someone who has invested heavily in LiPo's I'm just trying to steer you away from some common pitfalls. You can't imagine the number of folks I see that buy various sizes and then later are limited with what they can do because of size and the fact they can't get matching packs anymore.

Quote:
Originally Posted by dag214
And about testing, I took 2 Hackers last night and set one in a firewall with my Zinger, and the other on the new shaft. The new shaft I think is good to go, BUT, when I ran the Hacker on the firewall it was like WOW, this set-up has just about ZERO vibration. It was un-real how smooth it ran.
Yep, outrunners are smooth as silk, some of my planes they don't even generate enough noise to hear them in the air unless no one else is flying.

Quote:
Originally Posted by dag214
...but I want to make the investment for what is going to last the longest, and be the most stable. At this time that looks like it may be Thunder Power. I have to have a system I trust.

Thanks, DAG
I totally agree with using proven name brands but the one thing you have going for you is a light setup, by "light" I mean the demands on the packs. You should be able to fly anything given your setup won't be drawing any more than 12C max at any time during flight (assuming you go 5000 mAh or more). I would never talk you out of Thunder Power, just remember that this setup won't be taxing on any pack.

You do what you feel is best Dag, from what I've seen you've got it under control and if rear mounting the motors means less maintenenace, I say go for it. You've got a kick-a$$ project here, the fact you've gone through the testing you have and initially tried to make the shafts is enough to impress most of us!

Jack
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Old Jan 14, 2009, 06:53 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by jfetter
Not what I'm saying. I am saying if you get another electric plane (of course you will, if not 10 more!) it will likely NOT fly on 8S. Having packs you can use in other planes is what makes a good LiPo investment from a bad one. Remember, with $5,000+ invested, if I had but one or 2 planes I could use my packs in it would have been because I never thought it through well enough. Instead, my 6S packs can be used in 60 to 90 sized planes and run in series for the larger 2 meter planes, I can parallel them for 30%+ as well. Just a thought, being someone who has invested heavily in LiPo's I'm just trying to steer you away from some common pitfalls. You can't imagine the number of folks I see that buy various sizes and then later are limited with what they can do because of size and the fact they can't get matching packs anymore.



Yep, outrunners are smooth as silk, some of my planes they don't even generate enough noise to hear them in the air unless no one else is flying.



I totally agree with using proven name brands but the one thing you have going for you is a light setup, by "light" I mean the demands on the packs. You should be able to fly anything given your setup won't be drawing any more than 12C max at any time during flight (assuming you go 5000 mAh or more). I would never talk you out of Thunder Power, just remember that this setup won't be taxing on any pack.

You do what you feel is best Dag, from what I've seen you've got it under control and if rear mounting the motors means less maintenenace, I say go for it. You've got a kick-a$$ project here, the fact you've gone through the testing you have and initially tried to make the shafts is enough to impress most of us!

Jack
But my next 257" plane will take 8C packs

DAG
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