Should we still use electric props only?

[Erfolg]

Simon

I will look at your suggestion, a little closer.

It is not necessarily going to be dead easy to come to any real conclusion. I have noted that Master props, sold as electric/IC seem the same as Master IC and pretty much the same as my fine collection (I see from various forums as judged to be indestructible) of vintage Tornado props. For some reason APC electric do seem different, but not obvious to me why. In some respects they seem to be of the same style of my early low powered electric props, which I would not trust anything to, beyond a 480.

I think it could quite well be yourselve who noted that the root area of the blades tend not to be very effective. in any event.

The trouble is that the plan shape of APC seems so different to other blades, that it can appear that you become fixated in either justifying or denigrating the difference. Where in reality it may not be of any great importance, other than structurally.

Edited By Erfolg on 21/05/2013 16:26:54

[Chris Bott - Moderator]

The difference between the two as I see it because electric motors don't produce the pulsed propulsion.

This means that the props can be designed for efficiency. Hence the thin and shaped tips for minimum drag, at the tips because this is where speed is highest.

I/C props on the other hand have to have the bulk, to take the regular shocks.

[Erfolg]

I have found one major discrepancy, but it could be a typo on the HK site.

That discrepancy is TGS Sport electric propellers which seem to be 55g for one, not two as I thought they must be. Yet reading the reviews, a contributor suggests that weigh 18g, which would make the TGS the lightest.

You could well be correct Chris that the tips can be thinner with electric specific propellers.

Although the more I have looked at the props themselves and I am less convinced than ever that there is any material difference between the JXF, JM and Master Electric and my old Tornado propellers. There is a visual difference with the APC props, although again I do not know if it matters. I am going to mic up the props at different stations to see if the thickness variations are material, rather than slight.

I must admit, I am totally surprised that all seem to weight much the same, size for size.

[Chris Bott - Moderator]

Just done a quick comparison Erf, on the APC website (comparing some sort of like for like by using the same manufacturer) there's a spreadsheet of prop data.

A Sport 12x6 weighs 1.62 oz whereas an Electric 12x6 weighs 0.99 oz.

A Sport 18x10 weighs 4.69 oz whereas an Electric 18x10 weighs 3.03 oz

[Simon B]

I'd say those are fairly substantial weight differences...

[Erfolg]

Chris

Which props are you comparing

I have had a look at APC @ 47g , JM @ 60g and JXF @ 80g. Master do not seem to make a 12 *6 in the electric/IC range, although they do make electric only @ 41g. Strangly TGS electric 12 * 10 @ 85g

Unless HK are over stating the weight of TGS props, they appear to be heavier than any.

The size you have chosen is pretty large, the JM is 27% heavier than the APC, yet the TGS electric appears to be 80% heavier than the APC.

Yet these figures are very different to your + 189%

It is this lack of consitancy which puzzles me. Although I would preffer to stick to the commonly used sizes, which I think are probably more representaive of usage than what could be specialist type niche models, or maybe not. That is partially why I have looked at 9 * 6 and it is what I am using.

[Allan Bennett]

Perhaps it would be helpful to see some real-life comparisons: Here's four of my collection of 14" props (all x7, I think) -- three glow props and an APC E at the bottom. The weights, from top to bottom, are 53g, 58g, 78g, and 28g. I hope you can see what I meant in my earlier post about the tips of the E prop being more tapered than the glow ones.

[Erfolg]

I have just done my own weight comparison

my JXF 11*7 is 32g and the APC (style) is also 32g

Could it be that JXF and JM are actually intended for electric models? There weights are substantially lower than that, that some are coming up with?

Unfortunately the only large Tornado I had was just recently thrown out, as I had used it to ease GF mouldings from moulds.

Edited By Erfolg on 21/05/2013 20:05:59

Edited By Erfolg on 21/05/2013 20:11:00

[Erfolg]

I have just found a Tornado 12* 5 which comes in at 37g which is 1.3 oz.

Allen I also have been weighing real propellers as well as looking at the published data. To date all the data seems correct, wher I have the item.

Edited By Erfolg on 21/05/2013 20:12:42

[Allan Bennett]

Is your APC an APC E, or a APC glow (don't know what the series designation letter would be)? I've just weighed a "Super" 11x7.5 glow prop at 36g -- similar to your weight.

[Chris Bott - Moderator]

Erf, as I said, I was using data from the APC website.

I don't believe they are particularly big examples. Particularly the 12" example.

I think that all you are comparing is props from different manufacturers who use different density materials.

[John Miller 4]

I do not claim any knowledge on the design or even on the use of all types of props, but I advance the idea that the props designed for i.c. engines have a greater mass towards the tip of the blade. I suspect that this is to increase the flywheel effect of the propeller, without which I dont think any i.c.engine will run. This will of course smooth out the peaks and troughs of acceleration/deceleration which has already been spoken about. Just an idea!

[Erfolg]

My APC are electric types and are of type, not proper APC.

If you look at the picture previously posted with all my current electric props on the right and a batch of IC Tornado props on the left. The Tornado 12 * 5 is in that lot.

Many of my electric props are GF/Carbon composite blades. There are some very lightweight blades at the top, which I really should bin, as they were from the era where 80w from a 480 was only transient.

All the Tornados are Nylon.

As the trainer picture shows I have used APC after BEB suggested it would be fine and in practise it was fine dealing with 690w max.

This discussion comes about due to a cock up by me, and trying to establish what was the implication. I had expected to find a very different weight in the 9 * 6 size. I do accept that APC are lighter, yet it is only marginal in the range of propellers I have looked at and a comparison with a number of 9 * 6 Tornado propellers, which seem to have been breeding over the years.

I am a little curious why Nylon props seem to have gone out of favour, particularly as it is a tough, strong material, as a polymer. Where as materials such a HDPP (high density polypropylene) from memory was substantially poorer in all aspects other than being cheap. I do not know what APC is made from, but it does not have the look and feel of Nylon.

Trying to find data for Tornado propellers, only came up with they were made by the Grish Corporation, in the USA and still sought out by CL flyers as being exceptionally tough. No data though.

I feel that it is thought that I take the view it does not matter using an IC. The truth is I recognise I am looking at a selection of props, which I have and use and may not be typical. Yet the differences I am finding are not great, in the real world sense. But i do wonder if I am looking in the right place to find meaningful differences. I can say with some confidence, that when I switched from APC to JXF on the trainer, I cannot say I noticed any difference in performance, although at the time I was not looking for a difference. It was only yesterday I realised that I had made a change, which could have some significance.

[Erfolg]

You are probably correct in that the densities are different. Yet some do claim to be electric specific, yet are not a million miles away from IC examples, with respect to weight.

There has been one thing that has bothered me this afternoon and in the past. I have never know an IC propeller shed a blade. Yet I have lost a couple of folders and have been aware of a few conventional blades failing on electric jobies. I had thought, that the issue was down to reduced weight. Yet there does not appear to be a massive difference, to explain the occurrence.

The trouble is, it is not easy to get any data, as people do not loose a blade every week, perhaps 4 over a year, Yet this is not conclusive prove that blades are being shed. All I know, models have suddenly crashed, with motor some distance away, with a broken propeller. Again not very conclusive that it was a blade that was shed, even the 109 with the broken motor shaft, was it the prop, or the shaft or the pilot. So I am not even certain there is a problem, and if there is, what is the problem. To a large extent, that is why I have favoured composite propellers, endeavouring to remove a perceived potential risk. Which seems more real than the Rx arguments we have from time to time.

I do have a prejudice towards Nylon, in which I trust,although when I worked in the industry, was expensive and needed care in storage, but in its favour, a great material in many respects. I also do like wood, although the properties can be variable, does not fatigue. Although prone to damage from common usage.

[Allan Bennett]

In nearly 30 years of model flying I've never seen a blade shed, other than by contact with the ground. I've seen props thrown by 4-stroke engines, and blades damaged by contact with trees etc., but never one actually breaking off in flight. I'm not saying it doesn't happen, but I would speculate that, where it does happen, it's root cause is some damage that was caused previously.

I had missed the point earlier, that your props are APC-style, not genuine APC. From the weight of your 11x7 -- heavier than my APC E 14x7 -- it would seem that APC use a lighter "plastic" than some of the others.

[Erfolg]

It may not be apparent the reason I started this thread was to understand what the differences are between electric and IC propellers. This stems from inadvertently using a propeller which I think was a IC type and then reordering a replacement of the same type. Not initially thinking anything of it,probably as i had not noted any difference in use with a IC type.

I have also been using Master IC/electric propellers, these look just like any IC composite propeller, black and conventional in shape, at least to a casual examination.

I had thought that the principle difference between IC and electric props was weight. A comparison of the data of APS style props and JM and JFX did not reveal massive differences in weight. It was this observation which prompted the post.

It could be that APC style props are heavier than true APC, or that JM and JFX are lighter than std IC props.

It just happened that yesterday I was clearing my modelling stuff from my mums garage, when I came across my old Tornado IC props. Out of curiosity I decided to weigh some of these. Again the weight difference was not that great, not +50-100% which I might have just thought, yes, that is the difference.

I have tried to find additional information with respect to both JM and JXF props. I have found little other than JXF are classed as high speed props, what ever that actually means is yet another matter. From browsing some furoms, it does seem others have used JM propellers on electric models. Again there is no clue why, other than users seem pleased with them, whilst others write you should not use them as they are an IC prop. In a way I am a little surprised that there does appear to be quite a lot of usage of these props on electric models particularly in the USA, although that could be the forum.

Chris, could have highlighted how things are at the extremes, that true APC propellers are light, that there are some IC props which are heavy. Also the larger the prop, the greater the differences in weight appear, particularly as the % differences have only been calculated in a few instances.

It could be that JM/JFX and Tornado props are pretty much at the lighter end of the IC weight spectrum. If it is a given that APC style props are heavier, this could explain the lack of obvious weight differences.

I am a little reassured that the use of JM props on electric models is not the end of the world.

Like yourself Alan, I have never known, other than CL speed (modified) IC propellers shed blades. Yet it is not uncommon with Chinese folders, on direct drive, which I now think the Ripmax Me 109 was fitted with from a hazy memory. Yet I think a small number of conventional blades have in the fast failed on electric jobs. I am beginning to think that this could be in part, or wholly due to landing on rough pasture, and damage occurring, which has not been noted or perhaps visible.

It does surprise me on reflection, why Nylon props do not seem to be as widely available. Yet again, this could be down to where I shop and buy from, rather than a fact.

It is this lack of facts, common wisdom, which I find stands in the way of doing the right things for the right reasons, rather than the wrong things out of common practise etc.

[Erfolg]

Although it may seem that this thread and the question being asked has died, the basic issue has remained at the back of my mind.

To me the issue is "what makes a propeller better for electric applications than another".

To have some idea of what it is that matters, it seems that some testing must be done.

It seems simple, other than i have very little equipment, no access additional equipment that i would prefer to use (no longer working in industry, I do not have a budget, with no funds, to talk of).

My approach of necessity, also having a preference to limit the scope, I will confine my investigation to a very limited scope.

So that the investigation remains structured, it is my intention to investigate and produce a report in stages. I realise that what ever I do there will be criticism, some founded, some unfounded. Although I hope to remain focussed on producing a pebble of understanding to what matters.

Why bother some naturally will reasonably ask. I think that we in modelling, as well as in the world in general, are subjected to old wives tales that pass as facts, some are totally unfounded, others are half truths, others have no foundation in fact. Some of the misinformation originates from within the trade itself, for a variety of reasons, some honourable, others less so.

Anyway the planned structure at the moment, will have the following structure.

1. Background
2. Scope
3. Method
4. Investigation
5. Findings
6. Conclusion
7. Suggestions

It is some 9 years since retirement, so my report writing will be not as good as in the past, plus, time, seems shorter than I would like.

By the way the supposition is that "it is mass that matters"

Constructive feed back is welcome