Electric or not?

[Roger Dyke]

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 Collinson]

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 Dyke]

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 Skilbeck]

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 Dyke]

Hi Frank,

Thanks for the info.

[Andy48]

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

[leccyflyer]

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 Chaddock]

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.

[Keith Berriman]

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 2]

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 Dyke]

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 2]

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 McIntosh]

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 Crook]

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 Dyke]

Martin and Trevor,

All useful stuff. Many thanks for your experiences.

[leccyflyer]

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 2]

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 Dyke]

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.

[Cuban8]

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 Kremen]

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.

[Roger Dyke]

Cuban8 and Capt Kremen,

All good stuff this. Thanks for your replies. Contents noted.

[Nigel R]

I have a fair sized pile of old IC props in the 7 to 11 inch range. Most of them are the grey Graupner Super Nylon type. They seem to work perfectly well for my needs.

They were reasonably good back in the day, the wide tip is a bit noisy - less issue on electics - and that seems the main difference to the APC shaped props common now.

[Former Member]

[This posting has been removed]

[Richard Clark 2]

Posted by Cuban8 on 04/06/2020 10:07:31:

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

I suspect but do not know that most of it is down to the varying efficiency of different brushless motors over their acceptable load, rpm range, number of cells and radiated heat.

This it very important on EDFs but few bother to check it all out on prop planes - if the motor remains 'not too hot' on an extended full power test we tend to leave it at that. We have no way of determining the actual shaft power absorbed by the prop as compared to the input wattage.

Nevertheless I will buy and try a few of the APC electric props when my local model shop reopens.

[Bruce Collinson]

Agree with Capt. K re hubs on electric APC props, perhaps more so than their IC props. V. interesting re Aeronaut, never tried one. 4Max wooden electric seem good but only on a rather unscientific basis, and they are more fragile than APC.

BTC