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Old Aug 05, 2012, 07:15 AM
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Iflyrc_vic's Avatar
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Quote:
Originally Posted by TTRotary View Post

I'd suggest getting the Cermark FR to practice. At $100 PNP, you can't go wrong.
The Cermark model may have a wing loading of 8 oz./ft2 and the GoldWing aircraft may have a wing loading of 35 oz./ft2. Both of these aircraft may perform nearly identically at substantially different wing loadings due to the difference in size. However, experience has it that models of different sizes tend to fly differently.

Here are some numbers for comparison of this model at different weights:
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Old Aug 06, 2012, 02:29 PM
Rangers Lead the Way
Joined Mar 2010
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You can run all those numbers on motorcalc (google Brantuas ezcalc dma1) or, better yet, get yourself an amp meter so you see exactly what your amps will be. Adding pitch generally does not increase amp draw that much, whereas diameter increases will significantly increase amps. You can assume that 2pts in pitch is equivalent to 1in diameter. E.g. a 16x12 prop will draw same current as a 15x14, and in this case, a 14x14 would draw less current and be faster in the air. Your chosen power setup gives you lots of flexibility. Good luck with your build and maiden.
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Old Aug 06, 2012, 09:24 PM
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Quote:
Originally Posted by TTRotary View Post
You can run all those numbers on motorcalc (google Brantuas ezcalc dma1) or, better yet, get yourself an amp meter so you see exactly what your amps will be. Adding pitch generally does not increase amp draw that much, whereas diameter increases will significantly increase amps. You can assume that 2pts in pitch is equivalent to 1in diameter. E.g. a 16x12 prop will draw same current as a 15x14, and in this case, a 14x14 would draw less current and be faster in the air. Your chosen power setup gives you lots of flexibility. Good luck with your build and maiden.
I have an E-meter that provides static power system information and I will be using a Castle Creations ICE 100 with data logging. I will know EXACTLY what my power system is doing on the ground and in the air. I only posted those numbers to give others relative parameters for various flight package weights associated with this plane. I picked a power system that is currently being used successfully by G-Forced. I rarely choose a power system based on calculated numbers - I only use calculations to get me in the ball park.

I am no expert but, I would think that in order to get good performance from a 4S system on this plane, you would draw very high amps. That will result in motor, battery and ESC heating issues AND give very short flight times. Even at 7 pounds, the wing loading and stall speed is fairly high, therefore you will have to keep the throttle up for the duration of the flight. Let us know how your 4S system works out with this plane.
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Old Aug 06, 2012, 10:08 PM
Rangers Lead the Way
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Quote:
Originally Posted by Iflyrc_vic View Post
The Cermark model may have a wing loading of 8 oz./ft2 and the GoldWing aircraft may have a wing loading of 35 oz./ft2. Both of these aircraft may perform nearly identically at substantially different wing loadings due to the difference in size. However, experience has it that models of different sizes tend to fly differently.

Here are some numbers for comparison of this model at different weights:
Of course. You can assume that wing loading can increase at 0.5x the delta of the increase in wing area. A 20oz WL plane with 2.5s/f of wing will fly and land with the same degree of difficulty as a 30oz plane with 5.0s/f wing area. In this case, the two are similar enough: the Cermark (at least mine) has 22oz wing loading in a 51in span plane and will fly about the same as a 26oz loaded R3 "59 which would be about 7lb AUW. The airframe geometry is almost exactly the same, so they will have very similar characteristics. I did not make my recommendation of training on the FR off the cuff Another good choice would be the 57" Wingspan Bendix Special ARF which builds a bit lighter but again as similar wing and fuse geometry.

It will be a while before I get to the r3 build. I'm having too much fun with my warbirds right now. Talk about high wing loadings...
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Old Aug 06, 2012, 10:11 PM
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Australia, NSW, Sydney
Joined Nov 2006
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4s ! I would like to see that work but I can see how it could fly the R3 well. Your going to need some power here to fly it well. Mine flys great and from memory... was in the 170 Watters per pound region... I can get numbers for you guys if it will help. I would like to start expierimenting with prop in the future. This set up seems great to me and to be honest, I tend to get a bit lazy if it fly right... and Im happy I tend not to mess with it and I get this one right from the get go ! Not saying it could not be improved... But why mess with a winning formula !
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Old Aug 06, 2012, 10:29 PM
Rangers Lead the Way
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I agree G, you have a great setup. I should be clear and qualify mine as an experiment with a light R3 build to see if I can do it at 6lb AUW - the builder in me wants the challenge. And honestly, you are the first to post an actual flight on here. I acquired the plane long ago, saw how the airframe was constructed (light), and read all the disaster stories, so I swore I'd do a light build. At this point, I have an AXI 4120 ready to go in and I have 4S 5000s lying around, so I'll give it a shot. I also have 5S 5000s and can always up the cell count if necessary. If it is disappointing, I have a Turnigy 5065-320 lying around that I can swap in for 6S. So I am flexible, but want to try the featherweight approach first.

As far as props - I gotta say I'm totally jazzed with the square props. They fly awesome. Give them a try - you'll love them.
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Old Aug 07, 2012, 12:32 AM
Team Park Pilot - Airborne
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I too read all the tip stall, and low airspeed in the circut stories that ended in un recoverable spins and there seem to be a fair few on youtube showing exactly that.

I built mine as light as I could get it bar a carbon fibre spinner ( i had one but it looked wrong ) and the servos I have are mini servos but MG and digital so provided I dont yank n bank to hard they should continue to hold up well. I have the same servos in two 60` 3D planes that I thrash on a weekenkly basis and they hold up just great so Im confident they are an appropreate servo here.

As I said from the start... Fly the R3 like you would a heavy WW2 plane and apart from its ability to perform nice KE flight it flys very similar to my H9 Jug... Just much more pretty !

PS: Square props ?
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Old Aug 07, 2012, 02:07 AM
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Pitch to diameter ratio of 1:1, e.g. a 12x12 or 16x16.
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Old Aug 07, 2012, 02:16 AM
Team Park Pilot - Airborne
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Agh got you sorry !
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Old Aug 07, 2012, 05:32 AM
Chillaxin dude!
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Newcastle, NSW, Australia
Joined Apr 2003
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I thought you had fitted the sound system to your R3... hope you do and get some video when you do please.

Mine's still in it's box...
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Old Aug 07, 2012, 06:45 AM
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TTrotary, I am excited about your experiment and challenge to build and fly this model at 6-7 lbs. I certainly hope it works out well. I am just in love with the looks of this plane and choose a proven power system. Now it will be a matter of flying skills and.following advise from G-Forced.
Glad to see this much activity on this thread about a beautiful model.
Due to high demands, my vendor, General Hobbies, will not ship my model until today. I will not get it for a week - UPS ground shipment.
We may see.some more replies from folks who just purchased this model.
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Old Aug 07, 2012, 07:00 AM
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Ifly...Im sure yours will be a winner ! Also very keen to see TTs build a 4s version. I think it can be done but it would not fly the R3 with the same authority I believe it deserves. But this is only my opinion... I like em quick and although my R3 is far from a weekend flyer it gets flown and is ALWAYS fun !!
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Old Aug 07, 2012, 07:04 AM
Team Park Pilot - Airborne
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Quote:
Originally Posted by BulletMaster View Post
I thought you had fitted the sound system to your R3... hope you do and get some video when you do please.

Mine's still in it's box...
I have but not hard wired... Its a review project on has been earmarked for a 190 that just arrived.... or a beaver on floats that arrives tomorrow.....But I have a feeling it may end up in the R3 but the issue I see is mounting it in the side of the fuse. Could do it but it would need some redesigning and the obvious place in the cowling did not quite fit.
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Old Aug 07, 2012, 10:14 AM
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United States, WI, Delavan
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Do you have a link for your sound system?
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Old Aug 07, 2012, 01:10 PM
Rangers Lead the Way
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I'll let you guys know how it turns out. Maybe I'd better get cracking on this plane...
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