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Author Topic: Micro help  (Read 1566 times)
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ibgp3
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« on: May 26, 2014, 11:03:20 AM »

I'm just getting back to modeling after 50+ years off.
Stick and paper FF and one C/L then; RC makes sense now.
First I built a few test parts to learn how to replace balsa with Depron.
Then I adapted a cheap p47 to a p26ish (Phillipine version). (picture attached; waiting for decals)
Since the computer will let me build a 60inch wingspan from peanut plans or vice-a-versa,
...micro should take up a lot less room.
Since the micro p47 comes to the door for less than $60 RTF
...adapting the electronics and hardware to peanut scale models should be cheap simplicity.
Is anyone doing this?
I'm doing a peanut scale A-12 workup now with the next step planned to be another P47 for a donor.

Recommendations would be appreciated;
...either: "yeah, that works!"
... or :"Whoa, better to _____________"
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mjmccarron
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« Reply #1 on: May 26, 2014, 12:36:36 PM »

In my experience, the smaller the model, the more difficult to fly. If you're just starting in RC it might be better to have one plane of a little larger size, 42"+ with good stability (a trainer). This way you can learn to fly with something a bit more stable. After you get comfortable flying a larger plane you can move into micro's or anything else that interests you. Agreed, micros take up much less room but I've heard it said "large planes fly, small planes flit" On the other hand, there are some amazing micro's out there. just watch the weight and wing loading. Your free flight experience will help a lot. Another factor to consider is visibility. No offense intended but if you're getting back into modeling after 50+ years, your eyes are older than mine. A micro model at 20 feet to my 50 year old eyes is pushing my limits as far as visibility and flight orientation. It's very easy to loose perspective and orientation. In any event, have fun! that's what it's all about.
Best regards,
Mike
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ibgp3
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« Reply #2 on: May 26, 2014, 02:28:44 PM »

Thanks for the input Mike.
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ibgp3
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« Reply #3 on: May 27, 2014, 02:15:11 PM »

I made an immediate conclusion as soon as I saw the work-up of the A12 fuselage:
...there is not enough room for rubber, much less electronics inside an A12 with a 16" WS.
It  looked like enough on paper, but not when I held it in my hand.
...Now, based on Mike's advice I start over on the whole thing.
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ibgp3
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« Reply #4 on: May 28, 2014, 11:53:31 AM »

Ooops, still learning.
"Micro" electronics are available without an aircraft.
In fact, a receiver
   w/ESC, 
     2 servos,
     and 2 more channels;
smaller than a postage stamp is pretty cheap.
So an A12 with a 16" WS could work.

....but, I have everything here to build one with 42+", so that will probably be first.
Thanks Mike.
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mjmccarron
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« Reply #5 on: May 28, 2014, 11:17:13 PM »

The hobby has come a long way recently in the area of micro and sub miniature electronics. I look forward to seeing your progress with small planes. My smallest is a 21" stik. It's not too hard to fly in calm air but not tolerant of any wind. Hopefully you have an indoor venue. Anyway, I really only meant that larger might be better for the initial learning. Micro planes interest me but I have very limited access to indoor flying areas. I particularly enjoyed the articles in Model Aviation by Dave Robelin prior to his passing. He did some amazing things with tiny planes. The main limitation to micro size planes is wing loading and power. Modern gear seems to be quickly overcoming these obstacles. If you're interested, the 21" stik plans are available on Outerzone. It's called "La Stick".  http://www.outerzone.co.uk/plan_details.asp?ID=2330   It built fast and flies pretty good on an e-flite 300 and 2 cells. I'll post my build log when time permits.
Best to ya!
Mike
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ibgp3
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« Reply #6 on: May 29, 2014, 06:03:52 AM »

No local indoor flight possibilities as far as I can tell, but!
...I live on a triple sized cul-de-sac.
Any time it is still I can walk out with a small flyer.
...I left that out of my motivations for mini's.

La Stick looks perfect.
Lots of room for experimenting and fearless flying.
...crack it up and rebuild or start over.
Did you build yours with ailerons?
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mjmccarron
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« Reply #7 on: May 29, 2014, 11:27:51 AM »

Yes, I did build with Ailerons. It requires a very small servo, 4.5g class or smaller, and trimming was difficult. It required aileron differential to counter the adverse yaw. That's where the aileron moves more up than down, the down aileron creates high drag which yaws the plane in the opposite direction of the turn. Forgive me if you already know this. I bent the torque rods aft about 45 degrees and that was just about right. Here's a fair description of another method  http://www.rcgroups.com/forums/showthread.php?t=1115974  Without it, the plane required a lot of rudder input in turns but was manageable. It might be easier to learn without ailerons but I'd go full house. It's a fun little airplane to just throw in the car and take to the local schoolyard on a calm day. I also tried something new, I used small magnets to hold the wing on as opposed to sticks and rubber bands. So far I haven't had any unplanned disassemblies. The park 300 is a bit more power than it really needs. I'm sure it would fly fine with a park 250 or even smaller. I like a little extra "punch" on hand even if I never use it it's nice to be able to add throttle and go up when I get into trouble. In any event, let me know how it goes. As I said, I will post pictures and build log when I can sit down and put it into a logical order. I've been busier than usual lately.
Fly on!
Mike
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ibgp3
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« Reply #8 on: May 29, 2014, 12:33:29 PM »

Forgive me if you already know this.
Mike

If you assume I "just fell off a turnip truck"
...you will seldom be under-estimating me.
On any rare occasion where I might already know what you are talking about
...you won't hurt my feelings.

Thanks
  GP
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ibgp3
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« Reply #9 on: May 30, 2014, 06:35:19 AM »

Back to the micro help, while I work on my 42" A12.

Are pounds per square foot and watts per pound the predictors that they are cracked up to be?

For LaStick and some micro components I picked out
Based on catalog weights and builder reports I get:
prop 4g
servo 3 @ 2g  6g
power 3.3g
receiver .8g
airframe 35g  (less, I hope)
battery 4g
cruise 4g  (3 Axis Gyro Aircraft Flight Stabilizer)

AUW  57g

22" span = 97sq"

oz/sq'                                      watts/lb
97/144 = .673sq'                       3 watts
57g = 2.01oz                            2.01oz = .12565lb
2.01/.673 = 3oz/sq'                    3/.12565 = 23.88 w/lb

From one article:
Q:  A rule of thumb is that a sport-type, advanced aerobatic trainer needs about 50 watts per pound
    and that 10-20 watts per pound is about right for intermediate arf electric rc airplanes.

    As a guide, for model rc airplanes, if the wing loading is under 10 ounces per square foot,
    they will be suitable for the slow flying, gentle handling that you need in arf electric rc airplanes
    used as basic trainers.

This would put watts per pound in a good range and wing loading suitable for reducing the W/S down to as little as 12"

Real?


Test data for the power system;
Prop: GWS 5030
Voltage: 3.3, 3.8, 4V
Current: 0.76, 0.89, 0.93A
Watts: 2.508, 3.382, 3.72W
Thrust: 31, 36, 38g
Efficiency (g/w): 12.36, 10.64, 10.22
« Last Edit: May 30, 2014, 06:51:07 AM by ibgp3 » Logged
mjmccarron
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« Reply #10 on: May 31, 2014, 09:22:12 PM »

Hi GP,
To answer your question, yes. Both oz/sq ft and Watts/pound are very good indicators of performance. I'm not sure about your equipment but mine weighs as follows:
Motor Park 300 - 24g
Battery TP 2s-700mAh - 61g
ESC E-Flite 10A - 10g
Receiver Spektrum 610 - 9g
Servos (3) cheap 4.5g  -  13.5g
Total equipment weight - 117.5g

Airframe - approx. 60g with covering

AUW - 186g (6.5oz)

My power setup is running about 35W. I'm admittedly overpowered but I can't imagine it performing with anything less than about 20 - 25W. Your Watt/pound info is a bit low. http://www.rc-airplane-world.com/watts-per-pound.html Run your numbers again. I think you will find that 50W/pound is more like it and 6 - 10oz/sq ft is where you want to be for a small, slow flying model.  https://www.commonsenserc.com/page.php?page=wing_loading.html  The La Stick is a fun little plane. It's my smallest model so far.
Best of luck,
Mike
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ibgp3
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« Reply #11 on: June 01, 2014, 08:34:30 AM »

OK Mike.
I ordered the hardware and electronics.
Now I have at least a month to practice on the airframe.
The plan is to keep the wing loading under 10oz/sq'
...and take the size down as far as I can.
Skeletonize the fuselage and maybe even the tail feathers.
Depron and paper as much as possible.
Heroic weight reduction probably won't get over 30w/lb,
...but if I can get that in a 10" w/s (or even less)  Grin
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ibgp3
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« Reply #12 on: June 01, 2014, 08:46:39 AM »

Oh, I forgot
Is there a CG on the plan?
What works for you?
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« Reply #13 on: June 01, 2014, 09:13:54 PM »

I suppose it's a long shot, but if you have any of your old ff models around, they might make good RC trainers if you add rudder and elevator control. (And throttle if powered.) May be best to make a much larger fin and rudder than a ff model would usually have. I'm guessing a Sparky, Pepper etc. with small gear in it would make a decent trainer. Ron Fikes designed a simple but cute model that flies quite slowly called the Moosquito. If it appeals to you, I have scans.
picture: http://www.rcgroups.com/articles/ezonemag/2000/nov/gallery/MOOsquito1.jpg
You can only fly this one, though, when it's quite calm. Once chased it as it got blown over a nearby school building, with no shoes, because I'd been flying off the back porch. I get bored with it unless flying over the barbeque, under the swing set, around that tree, just higher than a running child can reach, or at night with LED's. You can do the same kind of flying with a Night Vapor, except it must be absolutely calm. If it's 50 feet up, you may have trouble seeing that it's actually moving.

Watts per pound is a good guide for models of a certain wing loading. For a plane like a Kaos 40, 100 or more watts per lb allows aerobatics. For a two meter glider, 40 to 60 watts per lb gives an adequate climb, depending on wing loading, efficiency of prop, etc. Of course you can use a lot more in some event that limits the motor run. I'm not so sure about the really small and light stuff.

I've heard that the Blu Baby design is nice for an outdoor trainer, and I know someone who likes it for that purpose. Found on RC Groups. There are many suitable trainers if you know what to look for. I suspect a scale A12 is not one of them unless designed and set up properly.

10 inch wingspan will be very hard to fly unless you build it so light that a sneeze will blow it off the table. (like, 5 grams?)
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« Reply #14 on: June 02, 2014, 12:25:50 AM »

Hi GP,
I have my La Stick balanced right on the spar. That seems to be about right. General rule of thumb, 25 - 30% of the chord to start.
Mike
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« Reply #15 on: June 02, 2014, 04:55:11 AM »

Thanks Mike

I suppose it's a long shot, but if you have any of your old ff models around...
Wow, no, never had that kind of continuity in my life.
...they might make good RC trainers if you add rudder and elevator control.
Long ago and far away I flew choppers; The aileron/elevator is very natural to me, but I just can't get the hang of rudder/elevator.
Looks good, I may look at that one next.
You can only fly this one, though, when it's quite calm. Once chased it as it got blown over a nearby school building, with no shoes, because I'd been flying off the back porch. I get bored with it unless flying over the barbeque, under the swing set, around that tree, just higher than a running child can reach, or at night with LED's. You can do the same kind of flying with a Night Vapor, except it must be absolutely calm. If it's 50 feet up, you may have trouble seeing that it's actually moving.
Sounds like fun.
Watts per pound is a good guide for models of a certain wing loading. For a plane like a Kaos 40, 100 or more watts per lb allows aerobatics. For a two meter glider, 40 to 60 watts per lb gives an adequate climb, depending on wing loading, efficiency of prop, etc. Of course you can use a lot more in some event that limits the motor run. I'm not so sure about the really small and light stuff.
I'm gonna do some experimenting.
I've heard that the Blu Baby design is nice for an outdoor trainer, and I know someone who likes it for that purpose. Found on RC Groups. There are many suitable trainers if you know what to look for. I suspect a scale A12 is not one of them unless designed and set up properly.
I've flown what I have enough to know that I can, and since I won't be riding in it I'm not afraid to fail.
...besides, the A12 is more than 1/2 done.
10 inch wingspan will be very hard to fly unless you build it so light that a sneeze will blow it off the table. (like, 5 grams?)
...actually the graph intersects at 8.5 inches. the oz/sq' gets up to 10 and the watt/lb gets to 48.
I'll be testing a glider tomorrow.
Thanks for all the input.
  GP
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ibgp3
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« Reply #16 on: June 02, 2014, 08:59:03 AM »

I applied what I learned here to my A12 in progress.
Should be about 30oz/sq' which is okay for an attack warplane.
Mike and Lincoln will approve of the 150w/lb.
...I will expect to go very light on the throttle.
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ibgp3
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« Reply #17 on: June 03, 2014, 11:03:53 AM »

An 8.5" LaStick built of depron and balanced with a penny glides like a FF rubber band model with no wind on the rubber.
...( Wow!! "balanced" on something this small is a tiny movement fore or aft.)
I built this with solid 3mm depron sides, etc; which seems very thick at this size.
I'll bet that opening up the frame and covering the holes with paper will reduce the weight by half.
Next step is to build a lightened version.
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« Reply #18 on: June 03, 2014, 11:13:41 AM »

Very nice! Sounds to me like you're having fun.  Keep up the good work.
Mike
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« Reply #19 on: June 03, 2014, 03:43:34 PM »

Very nice! Sounds to me like you're having fun.  Keep up the good work.
Mike
Thanks Mike
...having fun and learning at the same time;
...how good can  it get?
  GP
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« Reply #20 on: June 05, 2014, 12:37:41 AM »

GP,

You definitely have my interest. When I built my La Stick it was just a fun project as I was/am recovering from a motorcycle crash. I was surprised at how nice it flew with very little effort. I have always been intrigued by small/micro RC but always found it to be difficult. Please keep up the posts with your progress. Your use of Depron and micro gear may just be the right combination. I too come from a Helicopter background. I still have my excel 60. I have been into RC in one form or another for the majority of my life. You have inspired me to try micro again.
What radio gear are you using? There are a few power systems available using anything from small out runners to pager motors. Also, please post some pics when you get a chance. I'd like to see your 8.5" La Stick. I'll be posting my build this weekend if time permits. Thanks for your updates and posts.
Best to ya!
Mike
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« Reply #21 on: June 05, 2014, 05:47:27 AM »

One order from Hobby king:       
2.4Ghz SuperMicro Systems - Receiver and ESC All-in-one (5ch)        US$13.16        
HK-5330 Ultra-Micro Digital Servo 1.9g / 0.04sec / 0.17kg   3     US$3.64     
Micro Power system w/ Gearbox GPS-7   1     US$8.54     
GWS EP Propeller (DD-5030 127x76mm) green (6pcs/set)   1     US$3.29     

After I got the order in I realized that a 5" prop was gonna be too-o big.
...even if I use stilts for the landing gear.

I have a gyro that has been waiting for a project, and it's goin in
...even though I had to widen the fuse about 1/8" for it.

I cut some wing formers, and that size in 3mm depron
... look like they were cut out of 2x4's.

I figured out how to use coffee stir sticks
...( tiny straws.)
...for wing spars. Should save weight.

Oh yeah...I got to ride in the choppers I flew.
...never worked up the nerve to fly the models.
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« Reply #22 on: June 06, 2014, 09:49:24 PM »

A couple of days away from the workbench, but I did get to work on the spread sheet.
We have thousands of plans available, but what to do if the plan is for gas, or rubber, or for a 16" WS when you want 60".
...or 60" when you want 16".
This little calculator let's me (or you) estimate wing loading, watts per lb, and weight allowable for the airframe.
It takes into account that wing area and weight change as the square of the percent of change.
If it makes sense and you want a copy PM me and I'll send you one. 
...If there is a large response I'll ask Ratz to hang a copy up here.

Disclaimer: an estimate is a semi-educated SWAG.
               ...better than a shot in the dark, but not always more accurate.
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« Reply #23 on: June 08, 2014, 05:11:50 PM »

I've always wanted to be able to convert from gas to electric,
...and modify plan sizes up and down to suit my own ambitions.
There never seemed to be a place to go for a formula.
Now I seem to have put enough info together to have an estimate.
I'm putting it all up here for 2 reasons:
   1. If you see an error, please tell me.
   2. If you know a place that gives the capability I want,
         please tell me.

Basic conversion:
avg gas engines: 1250 watt/cu in.
    30 class = .30ci ; .3 x 1250 = 375 watt
    .049 = .049ci ; .049 x 1250 = 61.25 watt
Basic requirement
    Mild performance 50W/lb
    Mild aerobatics 75 W/lb
    Aggressive aerobatics 100W/lb
    3D or high Speed 125-150W/lb
    Competition 300+W/lb

applied to p51 models:
101" P51
From the plan:
  1720sq"
  18 to 35lbs  (8000 to 15,500 grams)
  2.5 to 7.4cu in (3125 to 9250 watts)
HIGH performance (largest engine, lowest weight)
   watts           9250            
   weight   8000                     
   Sq”           1720         
   oz/sq'    23.63         
   w/lb           524.47 (Doesn't need wings)

LOW performance (smallest engine, highest weight)
   watts             3125            
   weight   15500            
   Sq”            1720   
   oz/sq'           45.77         
   w/lb            91.45    (mild)

RFT 47"
From the web
   watts   200            
   weight   1100
calculated   
   Sq”   380   (1720 x .47 x .47)
   oz/sq'     14.70         
   w/lb     82.47 (milder)   

16" comet
   watts      30         
   weight   175g         
        hdw   30g         
   Sq”   44 (1720 x .16 x .16)
   oz/sq'    20.2      
   w/lb      77.76   (mildest)

Plus: Mike's LaStick
    watts   35   
    weight   186
    Sq”   97     
 oz/sq'   9.74   
   w/lb   85.35   (best)
« Last Edit: June 08, 2014, 05:24:36 PM by ibgp3 » Logged
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« Reply #24 on: June 08, 2014, 08:51:14 PM »

Most of my experience is with lightly loaded, low-powered, and small stuff, but I'll suggest anyway.

Doesn't weight scale with the cube, and not the square, of the linear dimension. Area should scale with the square of the linear dimension.

Fred Rash
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