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Electric or not?

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Roger Dyke03/06/2020 18:04:58
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306 forum posts
14 photos

Hi All,

Newbie to electric flight question.

Is it okay to use the 'standard' (IC) APC props on electric models.

If so, what is the advantage of the electric props over the 'standard'?

Bruce Collinson03/06/2020 18:08:35
537 forum posts

I never have and wouldn’t, I think the weight is the issue but where there is a bespoke prop, why risk it? Doubtless the electrickery wizards will weigh in with the science very soon.

BTC

Roger Dyke03/06/2020 18:11:45
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306 forum posts
14 photos

Hi Bruce, It was the difference in weight that I was thinking about. But I wondered if it made that much difference if it's well balanced.

Frank Skilbeck03/06/2020 18:50:52
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4734 forum posts
101 photos

No reason why you can't use an IC prop, the downside is that they are thicker, to handle the power pulses from an IC engine, this means they generate more drag, so they need more power to generate the same thrust than a thin section electric prop.

Roger Dyke03/06/2020 18:53:47
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306 forum posts
14 photos

Hi Frank,

Thanks for the info.

Andy4803/06/2020 19:00:55
1545 forum posts
9 photos

Heavier props put more strain on the bearings of electric motors. Personally I found IC props gave a worse performance size for size.

leccyflyer03/06/2020 19:08:07
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1479 forum posts
324 photos

Back in the day, before electric flight props were available, we just used the props that were out there to be used on IC engines. However the lighter, thinner blade profile props that are available do seem to give better performance, size for size.

In some applications though I still use some glow props - and example would be the excellent bright orange bendy nylon props made by J/ Perkins. I'm sure that they are a lot less efficient than same size APC-E, but for belly landing my BC Bearcat they are indestructible. Horses for courses

Simon Chaddock03/06/2020 19:20:50
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5717 forum posts
3034 photos

Given that electric planes do not have to withstand the vibration of IC and may be built 'lighter' to achieve performance a breakable prop may be a better alternative than an indestructible one which might damage something more serious before it breaks.

RC Plane Flyer03/06/2020 19:33:16
733 forum posts
10 photos

Roger You will have to take a close look at the diam of a hole in IC prop compared with diam of the electric prop driver. Spacers are available and there is usually 8 with electric prop

Richard Clark 203/06/2020 19:43:15
292 forum posts

Having tested all sorts of props I find that Watt for Watt the standard black 'Master' props meant for IC are the most efficient, though not by much.

I'm pleased by that as they aren't bright coloured, not some weird 'marketing department' scimitar shape, and are strong. (Though it would be nice if they were a bit more bendy.)

The fine tips on most of the APC props tend to snap off in a 'bad landing' and anyway the Masters beat them on efficiency.

Roger Dyke03/06/2020 20:10:10
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306 forum posts
14 photos

Hi Andy, leccyflyer, Simon, RCPF, and Richard,

I thank you all for your very valued and informative replies. I think that I now have enough info to make a decision as to what props to use.

RCPF: I did notice that the hole in the IC props seemed to be bigger than the electric props. Fortunately I have a number of the special little spacers in my kit. Good tip though.

Thanks again,

Roger

Richard Clark 203/06/2020 21:30:33
292 forum posts
Posted by Roger Dyke on 03/06/2020 20:10:10:

Hi Andy, leccyflyer, Simon, RCPF, and Richard,

I thank you all for your very valued and informative replies. I think that I now have enough info to make a decision as to what props to use.

RCPF: I did notice that the hole in the IC props seemed to be bigger than the electric props. Fortunately I have a number of the special little spacers in my kit. Good tip though.

Thanks again,

Roger

We are all 'experts'

"For every expert there is an equal and opposite expert" - Arthur C Clarke

Martin McIntosh03/06/2020 21:51:05
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3422 forum posts
1215 photos

If you are talking about Master Airscrew props then on an i/c they are notoriously inefficient and noisy. I do have to use them occasionally on electric because they do useful three bladed ones. I have found that on an electric set up the APC E series are way better than the equivalent i/c ones. Balancing them is the key.

Trevor Crook03/06/2020 23:25:04
968 forum posts
69 photos

I've used ic props on many electric models in the past, when I haven't had the correct size electric prop. They work fine, but I'd agree they are not as efficient as a decent ep prop. I've never had any problems with their long term use on the motor. The ic ones I used were mostly the Graupner grey ones, left over from my ic days.

I have found APC electric props to be very good, but as said above the tips are quite fragile. The Master Airscrew look better, but when I put a pair on my Mosquito to replace some APCs, there was slightly less thrust for the same current.

Roger Dyke04/06/2020 06:29:44
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306 forum posts
14 photos

Martin and Trevor,

All useful stuff. Many thanks for your experiences.

leccyflyer04/06/2020 07:25:36
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1479 forum posts
324 photos

For aesthetic appeal I love the Master Airscrew electric wooden props - they are beautiful, but they are not very forgiving in the case of a prop strike on landing. I also really like the Aeronaut white props, which in my testing have emerged as a very creditable alternative and they don't tend to break. The Graupner Cam props and Speed props are other favourites.

You can never have too many props in electric flight and some testing with a tacho and wattmeter/clamp meter often yields useful and sometimes surprising results.

As electric flyers tend to have lots of props - where do you store yours and do you take them to the field?

I keep my "ready use" props in a fishing tackle box, which usually goes in the car when I go to the field. It;s more of a big red and grey amulet against breaking a prop, TBH, because I find that the times that I do break a prop are the days when it is sat at home. It also houses all the prop reamers, a couple of balancers, prop adaptors and the tools needed to change a prop in the field. It comes in handy if someone else breaks a prop and you can get them back in the air as well.

The rest of the props - especially the multi-blade and folders sit in one of those sets of plastic drawer units on wheels. I'm sad enough that I have occaisional sessions where I sit on the floor and sort out all of my props, putting the same size props in plastic bags and writing their diameter and pitch on the bags in big letters - I struggle to see the tiny embossed numbers that are on the props.

Richard Clark 204/06/2020 08:04:02
292 forum posts

The carefully measured results I got using a wattmeter, tacho, and spring 'fishing' balance to measure thrust on a string tied around the tail with the various plane's wheels on the (smooth concrete) ground the black 'IC' Master props certainly surprised me.

Roger Dyke04/06/2020 08:21:43
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306 forum posts
14 photos

leccyflyer: In my flight box that I take to the field I have one of each for all the planes I have. They are in a plastic "pouch" and sit in a special compartment in my box. In the bottom drawer I have every tool you could think of (and more) for any unscheduled event at the field. At home I have about 20-30 more props that I have accumulated over the years and they are kept flat in a drawer in a dark garage. I have a length of round section cable threaded through them and are thread on by size. I will probably never ever have a use for most of them again as they are all IC and of the sizes and types that I don't tend to use nowadays.

Richard: Thanks for the info.

Cuban804/06/2020 10:07:31
2960 forum posts
1 photos
Posted by Richard Clark 2 on 04/06/2020 08:04:02:

The carefully measured results I got using a wattmeter, tacho, and spring 'fishing' balance to measure thrust on a string tied around the tail with the various plane's wheels on the (smooth concrete) ground the black 'IC' Master props certainly surprised me.

I did the same experiment some time ago comparing (IC props) a black Master Airscrew with the equivalent APC on a model with a .91 fourstroke. I don't recall the exact details, but it did put me off the Master Airscrews as IIRC, my test piece's static thrust was down by 10% compared to the same size APC. About a pound of static thrust lost. Master Airscrews are OK, but not the most efficient if you're looking for top performance, normally fine for sport flying and they tend not break so much in an 'arrival'.

I always choose the geniune APC electric props for 'leccy.

Edited By Cuban8 on 04/06/2020 10:09:04

Capt Kremen04/06/2020 10:39:18
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361 forum posts
144 photos

After years of using the readily available APC 'E' props, I re-discovered Aeronaut fixed props. (I had previously often used their folding props on E-gliders). Whilst such measurements as can be made with a watt meter and tacho, give a guide, I find actual performance in flight use more meaningful. Re-propping several different models from APC E prop to Aeronaut 'Black' of the same size and pitch has been interesting. My findings, born out by club mates comments, they are quieter. Throttle settings for like-for-like performance are slightly less giving a little extra flight duration. They balance very well, even the hubs are not far out which often seems an issue with APC E prop.

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