Hi all
Looks like the real experts are using 750 squares wing size
but a 660 Legacy is the biggest my car will take,
so I am looking for a starting point suggestions to convert a
Broadak Legacy to electric power

Motor, battery, ESC,timer,Prop etc
also the ESC and timer settings
if its not asking too much

thanks as always

Vincent

Hi Vincent,
How heavy is this airplane minus motor and batteries? If it will come out at 60 ounces or less with a bit less than 13 ounces of battery and about 7 ounces of motor and another ounce for ESC/timer then you are looking at a 4-cell 4200 mAH plane turning a 12-1/2 " diameter prop. If the motor has a Kv of around 900 then the pitch will be around 6".  Alternatively, you are looking at a pound of battery 5S) approximately 3 more ounces of motor.  Both ways work, but if I have a choice between two setups with the same Watts/ounce and one weighs less then you know which setup I will go for.

keep us informed,
Dean

Vincent,

Glad to see that you are moving forward in your electric PA program. I love to see people moving forward in most anything as it is a lot better than moving backward. I'm going somewhere ! Can you sense it? Yes, wait a minute, wait a minute, yes how right you are! I am going to beat the idea of converting models to electric power to death. You can't get there from here. I don't care what other people want to tell you about how they flew a converted whatever-u-callit stunter and are happy with the results. Phooey!!      

Lets for the sake of the discussion assume that your are the perfect builder. (You are aren't you?) All alignments are within .02 of a degree. All flying surfaces are straight and accurate to within .005 per lineal foot. You use nothing but the best hardware money can buy. No, wait again, you have everything custom CNC machined to your exact specifications. So we agree that you are a very. very good builder. Nothing you do personally to your model will in any way impede the ultimate result of your efforts.

The very first issue that I want to take exception to is the idea that WEIGHT does not matter. Assuming the above about your building skills, IT MATTERS MORE THAN JUST ABOUT ANYTHING ELSE ON THE PLANET!!!

Power to weight ratio is not just an abstract concept it is an absolute. Pull the nose up smartly and the angle of attack of the wing increases abruptly, the amount of lift skyrockets and, and, wait for it......... The amount of drag goes through the roof!!! Without a high enough P/W ratio you will begin to slow down fairly rapidly, your controls become sluggish. You turn again and more of the same thing happens, your controls now almost unresponsive. Gravity is catching up with you and soon you will be approaching a stalled condition. This isn't good!! This is not precision aerobatics. Am I guessing about this? No, not at all. Like some other C/L pilots I am also a full size pilot and have an aerobatic endorsement as well as being an instructor.

Little planes fly just like bigger planes. They must obey and are controlled by the same rules of physics as any other flying body. It is even harder for them as their size poses unique aerodynamic problems.

While weight itself is not the defining issue in flight, power to weight in an aerobatic plane most definitely comes pretty close. A plane (and I am not picking on Vincent) that weighs 76 ounces and has 660 square inches of wing and is powered by a .61 is GROSSLY!!! underpowered and the wing is over loaded. Again, I do not care if uncle Fred or some guy at your field has a lead-sled and tells everyone how well it flies. It doesn't.

You can not make a silk purse out of a sow's ear. Vincent is correct, both Paul's and my plane have approx 750 square inches of area. Why? because they need the lift to keep the wing loading in the correct range. They also both have gobs of power on reserve that the governor can tap into to keep the plane moving at close to the original entry speed of each manoeuvre.

Both Paul and myself use very light (really light) building techniques. There is little or no plywood, thin balsa dimensions, all molded pieces etc. Paul's plane weighs 68.5 ounces and mine weighs 70. They have the power of MORE than a ninety!! This is the place to be in the power to weight ratio discussion.

It seems clear that there are NO kits currently available that convert properly to electric. I am not talking about whether you CAN put an electric motor in one and make it fly, I am talking about if the result would be better than using a piped PA .61.  If the result is not better than you should be putting a PA into your plane and not an electric motor because no matter how hard you want to try to tell me that it flies OK I know that in the reality of top level C/L competition it does not. So why put yourself behind the eight ball and create a handicap that you do not need to carry?

As I have said before, if you want to get familiar with the electric environment then by all means do so with a converted ship. Paul did. And then just as quickly built a new purpose built plane for electric power. It is quite different from a standard IMPACT. He is now building his third electric plane in the space of just over a year. Why? because we keep learning things as we go and want to incorporate them into our planes. You should consider doing the same.

I can absolutely guarantee you the following:You will have much more success in flying C/L precision aerobatics with a tuned pipe/PA powered model if it was not designed for electric power. Don't forget Mr. Cav E. Atemptor!

OK so much for my rant. If you want to fly a 660 square inch model this is where I would start with respect to defining the weights and equipment to use. (you can not fly a 5S setup on 660 sq/in of wing)

You will not want anything more than about 60 ounces all up weight. I would suggest that to achieve this you will need to build a model completely finished except for power train weighing no more than 35 ounces. This is the power train I would try:

Motor

Plettenberg Orbit 25-10 Kv=930 weight=8.8 ounces

Battery

Thunder Power ProLite TP 4200 4S2PL 14.8v weight = 13.4 ounces

Esc

Schulze 18.46k - F2B  weight= 1.6 ounces 

Connectors / Wiring / Timer

weight = two ounces


Hold on a minute, I think I am not quite finished my rant.

Powering a model designed and built for legacy IC power with electric is like installing a wind turbine and photo voltaic cells to power your new "green" earth berm house and keeping your old energy inefficient appliances your mom gave you when you first got married 30 years ago. Just doesn't make sense. (IMHO)

Kim.

To All,

Hi KIM,
You said: " ..... The very first issue that I want to take exception to is the idea that WEIGHT does not matter. Assuming the above about your building skills, IT MATTERS MORE THAN JUST ABOUT ANYTHING ELSE ON THE PLANET!!! ....."

I wish you would show some passion in your posts, your just way too blase about this topic. 

I'm not sure if it matters THAT much, but it is important. I think what you meant is that the P/W RATIO is the most important thing. (as you alluded to in the rest of your post). This I agree with 100%. I just feel that we need to make sure we put as much importance on the POWER side of the equation as we do on the weight side.

I think the supreme hang up on weight comes from the decades of flying CLPA with Fox .35s (very little power) so the only way to make this critical equation work was to lower the weight at all costs. To make matters worse, these weak engines could not pull a high lift airfoil so we had thin airfoils (lower drag) that made the wing loading (more accurately the weight to lift ratio) even more of a problem.

Now we have more than enough power (ECL or Piped IC) to carry a little more weight and STILL have enough power left over to drag a thick, high lift, airfoil through the air. The higher lift airfoils and relatively large wings (660 sq. in. is LARGE compared to the "Classic" size planes) take care of the weight to lift ratio problem, even with a few extra oz from a modern well made ARC plane. .... Your's and Paul's 750 size planes are even better! (BTW, what do you think the top limit will be for wing area? And weight?)

I agree that a "Purpose built" ECL plane is the optimum set up, especially for the highest levels of CLPA. But I am not convinced that a straight, modern IC Kit or ARC conversion with a few lightening holes and modified front end is not far behind. AND they are as good as "MOST" CLPA flyers can build. Many good ARC ECL setups will get someone to the top of ADVANCED and well into Expert. We will soon see some EXCELLENT, higher priced, light weight, quality ARCs come on the market. Look for Moon's new products, and others. These new ARCs will be a very good match for an ECL conversion.  (not perfect, but still very good) and they will be lighter than most average modelers could build on their own.

In the Dark Arts, IMAC, and other areas, our ARC/ARFs are as good (straight, light and beautifully finished) as the very BEST builders can make and much better than ANY normal modeler can ever hope to build. We in CLPA may not be a big enough market to ever get to this level, but our CL ARC/ARFs will continue to improve.

As a "worst case" example, take my totally STOCK ARF P-40, no attempt to lower the weight. ........... (You had better be sitting down to read the GTO weight ;-)....... 57 oz. on a 560 sq in wing. (I even flew it at 60 oz for 40 flights with the Eagle Tree data logger on it! Yikes ;-). This plane flys GREAT. This is just not my opinion, but several VG EXPERT pilots have flown it and were shocked at how well it flew. It pulls strong in the power grabbing hour glass, where P/W ratio is paramount. It's modern thick airfoil helps a lot in carrying the weight.  ..... Would a lighter plane fly better? Probably. In dead calm, Definitely, in wind, I'm not sure. But it still flys a very good pattern and is competitive. 

Please don't misunderstand me. I am not advocating heavy planes. I am only saying that we should make sure we are not letting any past ideas cloud our judgment on todays modern setups and too easily discard the possibility that a good ECL conversion can not be a competitive machine. There are MANY pilots flying in B,I, and AD. And they would be very pleased at the performance of an ECL plane converted from one of the present made for IC kits or ARC/ARFs.

Instead of always talking in terms of XX oz is good or bad, maybe we should talk more about P/W ratios and Lift/W ratios. As we go up in wing area and thicker airfoils our wing volume increases by the cube, not just the square. Lift goes up very fast. When we go up a little in size of our plane we get an increase in the all important Reynolds #.  (We fly our DA planes at 32 oz/sq ft and they FLOAT through the air and never feel "heavy", because we operate with thick airfoils, and higher R #s.) And as Dean has said before, speed has a large impact on lift. Our increased power with modern ECL allows us to use longer lines which allows higher speeds (more lift) to the limits of our 70' rule while still remaining at a comfortable 5 sec/lap.

Again, I agree with you 100% that P/W ratio is the most important element in our CLPA planes. This bodes well for ECLs future! 

Hi DEAN,
Have you looked at the new Hacker "40" series of motors. They cost the same as the AXI, and I think they are better. I have used them a lot in RC. Will uses Hackers in his beautiful Bomber and likes them a lot. This 40 series weigh a little more(9oz.), but they have more bearings, and a fan as standard, and because of their larger size, I am guessing they put out a little more power?  Here is the link:

http://www.hackerbrushless.com/motors_a40.shtml

Hi VINCENT,
Don't worry about the minor memory loss, your not alone. I missed a trophy at a contest this year because during the H-8s I could not remember if I had done one or completed two yet, so I did one more (3rd one). All this was in what, < 8 seconds? Now THAT is a bad memory! 
Getting older is the Pits sometimes!

I think you will really like your Legacy with the power system suggested by Kim and Mike. I'm looking forward to seeing how my Score ARC (same size) flys with the Hacker 40. ..... Please keep us posted with your results.

In the winter, do you fly between the raindrops there in Beautiful Ireland? I think my camouflaged P-40 would disappear flying at one of your lush green sites? Congratulations on being listed as the 5th best country in the world to live in! You ranked way ahead of us.

Regards, 

Hi DEAN,
Have you looked at the new Hacker "40" series of motors. They cost the same as the AXI, and I think they are better. I have used them a lot in RC. Will uses Hackers in his beautiful Bomber and likes them a lot. This 40 series weigh a little more(9oz.), but they have more bearings, and a fan as standard, and because of their larger size, I am guessing they put out a little more power?  Here is the link:

http://www.hackerbrushless.com/motors_a40.shtml

Regards, 

Hi Rudy,
Heck I've got a bunch of flight time on an A60 short 20-turn. Yeah, they are good too. Better? It's probably a wash. The big ones have the outer ring bearing, but I don't think the A40 does. I should check ... Anyway, I'm looking to get away from outrunners even if it means spending more money on something like a Neu 1900 series motor. Ohmigosh! It's domestically made

I'm no fan of fans, because i know that 55 MPH will provide plenty of cooling if I just direct a little air on the motor, and the wattage used to drive the fan should be flying my plane.

later,
Dean

something like a Neu 1900 series motor. Ohmigosh! It's domestically made

looks good, I would try one, but unfortunately they are NOT domestically made ... they are made on opposite side of globe  ... 

  ... at least I have MVVS, MEGA, JETI, ROTON, MGM, AXI, PJS in range of 100 miles .. if nothing else, I see that there are also motors made also in another country than Czech 

BTW, I spoke with maker of MVVS motors (it will sound crazy, but it is the same person made several motors from that upper list). He did not tell me (he did not want to) internal resistance of MVVS motors, but I got one and foud that MVVS motor has usual (well may be little worse than usual) internal resistance which I can expect from such motor. For exmaple I got MVVS 4,6 840 (220g heavy with fan). Its Internal resistance is 33mohm, iddle current at 10V ~1.5A and rpm/v was little less than stated - ~820.

They really do not say all parameters, but fortunately they have table of measured data here: http://www.mvvs.cz/download/namerene%20hodnoty.xls

I can say that MVVS are typicaly with average internal resistance and better that usual iddle current and they are VERY well ballanced. I did not feel rotation keeping the runnning motor in nand. If I can compare with inrunner like for example neu 1905/2.5 then the internal resistance is aproximatly the same, but neu is better with iddle curret. It will allow better maximal efficiency, but question is if we can really use it without gear box. It will need unloaded prop but our 12" props will push the efficiency to the same number like we can get with MVVS - means somewhere at 82%.

BUT ... I feel that motor with such low I0 will work well at partial throttle. I think I will try such motor, I thnk there are chip motors available from Feigao with similar parameters. I think I will try one.

Hello Vincent,
I'll bet the Dalotel looks good in the air.

Igor,
Thanks yet again. The MVVS 4.6-840 is a very good alternative to almost all the outrunners at 33 milli-Ohms and 1.5 A idle current. It will not suffer an efficiency penalty that I can see. With a Kv of 840 or 820 I predict a useble propellor range of 12-6 to 13-7 on the governor. Now why isn't there an emoticon for someone staring into a crystal ball?
later,
Dean

Mike,
You don't have a Pletty in the Mustang? I just assumed so. Wow ... I took it for granted after all the good experience you had with the Pletty in the Silencer. Okay, how do you like it so far. You did get some flying in before the weather changed, right?

We don't live that far apart, we have to get together.
Dean

Hi Dean,
   No I didn't get any flights on the Mustang "yet". As long as the weather is reasonable I will try to get some flights after the holidays. Things are getting busy for me right now.
   I loved the Plettenberg, as does Kim and Paul, but I wanted more. I think we are on the same train of thought with a more efficient inrunner. I don't know how much there is to gain, but I (we) have to keep looking for more.

Rudy,
   The "it" motor is a Steve NEU ORK 19xx motor. I bought one last year and built the nose of my Mustang around the ORK, but I am yet to fly it.
   By the way, ORK stands for OutRunner Killer. It is a inrunner designed to develop the torque of an outrunner with the efficiency of an inrunner. The best of both worlds. I hope this is one little step closer to the perfect electric power plant. The BIG gains are yet to be found in power delivery control. 

Mike

Thanks Dean and Dennis for your supportive words.

I want people to realize that the advent of electric power for control line models is not just a shift in power plant options but rather a wholesale paradigm change in how we can approach this most beloved aspect of our lives. Sure you can sit on the fence or dig your heels in or stick your head in the sand with respect to what is happening all around you but you are missing something magical! Electric power is not just a different power source, it is more like the advent of flaps on control line stunters. To participate in this new opportunity at its inception is a rare treat!

Dennis you are so right! ----- Exciting times ahead!!!

Kim.

Hi Mike,

I like it: "ORK" 

I have converted all my ERC motors from inR to outR. The geared inR are more powerful and run larger props, BUT I got tired of the noise and unreliability of the gearboxes. I understand that your Neu-ORK's are to be run without gearboxes? Is this correct?

I hope you get a break in your WX so you can make some test flights. We are looking forward to hearing of your results.

BTW, do you guys fly CL on skies like the RC guys do back there? I would think that with our high ECL P/W ratios, it would be easy to do?



   

So did you buy the 2-turn motor, Mike?

Dean

Kim,

One question on the suggested motor the Plettenber Orbit 25-10, it wt 8.8oz. The AXI 2826-10 wt 6.4oz. Why the Orbit motor? Since P/W is important why not go with the lighter motor that is also a CL proven unit for this size ship?