I am considering converting a Hanger 9 62 1/2 in wingspan Cessna over to electric. It currently has an OS 46 Ax in it. I don't like the mess of glow fuel so I am considering the conversion. I purchased a Turnigy L5055B brushless outrunner rated at 600kv. The plane will weigh about 7 1/2 lbs with the big 6s 22.5v lipo. Since the rpm will be, 22.5v x 600kv=13200rpm swinging a 12-8 and using a 70A ESC do you thing this is the correct set up or should I go to the smaller 18v lipo which would reduce the rpm 10800 and lighten up things about 1lb? Is my prop size and plane weight about right, what would you recommend? Is there a conversion chart that a begginer can use that is fairly easy to understand? This coversion stuff can be a little confusing. Thanks for any info you can give.

Not really a chart, but possibly useful: http://www.horizonhobby.com/article/...ric-conversion

Left seat:

Note in the above link that there is a "chart" for power to weight considerations. This is pretty much duplicated in one of the sticky's at the top of the Beginners Forum.

When making the measurement for weight, you must consider everything, even though you may not have them in your posession. This means that you will have to select what power lever you want (based on performance), then find a motor, esc, battery pack combination - since you fly it already, you have servos and so on. Get the weight from the supplier for the products you are trying to use. Weigh the plane without the glow engine, fuel tank, and battery pack (the receiver and of course, the serovs, can be re-cycled so include them in your weight calculations). Add everything up and convert to pounds (if you have weights in ounces or grams) then compare that to the chart for watts per pound, using the total weight you found in your measuremets and the flying style you wish to use.

This will give you a pretty good ballpark figure for the conversion and if the selected electric products will work. If not, then get other figures on other electric combinations and re-calculate until you find what you need then head to the LHS or get your order in.

One thing I might mention here. Get more than one battery pack and a good balance charger. Consider that it could take you an hour at 1C charge rate to re-charge the used battery pack, this based on your flying style and throttle management, which will be really different for the electric than it was for the glow. This conversion could be costly so consider this as well as your flying time in your decision to make the conversion.

I prefer glow so I don't mind the clean-up. The reason is that the power level is constant throughout the flight, and I can land, refuel, then take off five minutes later with glow where with electric, if you have one battery pack, well, you will get one flight per hour.

There are a lot of advantages to electric as well as with glow. Weigh the differences before you make the choice to convert. If you like the electric conversion, well, knock yourself out and have fun.

CGr.

G'day

Given the numbers you have supplied and assuming that the motor pulls about 60 Amperes from a 22.2 Volt battery with that prop, it will be generating approximately 1320 watts of power. That is a bit less than 2HP. You will be getting approximately 175 Watts/pound of aircraft. This would put it in the 3D performance range and would be WAY more powerful than the setup you have with the OS 46.

I recently converted a similar 40 size Cessna using a Turnigy 46 motor (ie approximately the same power as a 46 Glow). It has a slightly lower Kv rating and I used a 4 cell 5000 MaH pack and a similar prop to the one you are considering. It flew with plenty of power drawing less than 30 Ampres peak but I did not like the way it flew generally and it is now in semi retirement.

I think you can easily fly the model either with a smaller prop and/or a battery with less cells. One of the advantages of electric motors is that you can simply use a smaller prop to get less power. The benefits are then less current draw and longer flights as a result. And you can easily go back up in power with more prop.

I generally set my electric setups to turn my desired prop size at about 10 to 11,000 rpm by selecting an appropriate number of cells to match the Kv rating. Then measure the current to make sure the limits of the motor and the ESC are not being passed.

I also agree that one battery is not very useful. I now try to have at least two of each size. I also sometimes use 2 x 3 cell packs wired in series to get a 6 cell setup that way I can use the 3 cell packs in smaller planes.

There is no simple answer to all of this. Some experimentation will get you there.

Cheers

Mike in Oz

A 12x8 at 13k rpm is about what a .90 size 2 stroke glow would give you, so that setup is way overpowered for your plane. At 10k that's about a .90 4 stroke, which is still overpowered. I'm guessing you're using an 11x5 on your .46, probably turning about 14k in the air? If you choose a power system that turns that prop (electric version of course) at that speed you'll replicate the performance of your .46. If that lets you keep the weight the same, you're good. If it gets a little heavier, you'll need to consider how happy you are with the power the plane currently has and consider is a little less performance is ok, or it you will want to go up a few Kv and draw a few more amps to compensate.

That motor works GREAT with a turnigy plush 60 esc. and 6 cell packs! You will probably find that a 13/8 prop is awesome on there.. I have some different planes with this setup and love em.. its a little more motor than you need, but its just light enough the plane will fly well. I have this setup in a four star 40, a Pica FW190, and a Sig senior
(Senior has a 400 kv version, swings a 16/8). I run a huge pack in the senior to balance it out and haul up payloads, It has a big Bomb Drop built in.

Senior 5000 6 cell
FW190 5000 6 cell
Four star 3000 6 cell

You have a small fortune tied up in batteries!!

It is a Cessna not a rocket!

With that prop the plane will have 10lbs of pull and will cruise flat out at 100mph... can you say FLUTTER!!!

Drop the prop to 11 inches for a 1:1 power to weight ratio and drop the pitch to about 5... e.g. an 11x5 or 11x4.5 E prop to increase your flight time and put the plane into the right speed range.

At worst use a 12x5 or 12x6 prop, but the plane will be speedy and you'll be sacrificing potential flight time for thrust...

You need NOT change anything else.

The same combo on a different plane could benefit from the 12x8 prop or even the 13x8, but not the Cessna.