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6th 2021 F3-RES F5-RES combined 14 day Duration Challenge


martynk
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martynk

A placeholder for the 6th combined 2M F3-RES, F5-RES  14 day duration Challenge for 2021.

This is an experimental event and the rules may be altered for subsequent challenges.

Please submit your score below. The clock will start when the first score is submitted and will restart if and when the current high score has been beaten.

This is a for fun challenge for UK based pilots, anyone may enter with EITHER 

1. a bungee-launched glider up to 2 metres wingspan and the standard Hi-Start can post a time. The standard Hi-Start bungee is a maximum of 10m of 6/4mm surgical tubing and 50m of static line (minimum 30lb breaking strain). Lighter/smaller bungee rubber may be used.

OR

2. an Electric motor launched glider up to 2 metre wingspan fitted with an Altitude Limiter set to 60m and a maximum motor run time of 20 seconds.

Object: Fly your 2 metre glider for as long as possible from a flat field, the person who's time is unbeaten for 14 days 'wins' and a new challenge starts.

Rules:

Flight times begin when line releases from the tow-hook or in the case of an electric motor powered glider, 20 seconds after the hand launch. The model must land in the launch field for times to count. While the object is to encourage F3/F5-RES types, any model up to 2 metre span may be flown (F3/F5-RES, foam, R/E mouldie) but please state the type of model with your time. Note that ailerons or other camber changing devices fitted are no longer permitted, even if disabled. 

No Flight information telemetry permitted except for Received signal strength and Receiver battery status.

Fly safely! No slope soaring

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  • martynk changed the title to 6th 2021 F3-RES F5-RES combined 14 day Duration Challenge
Graham Lorimer

Another fine day of thermal gliding at Fish Meadow, 2 meter not much good in the morning, but only one flight was needed at 15.00 to get a very nice start to the Postal Competition.

Today was the turn of the ARTF Circle Dancer, and now with a bigger prop fitted to the ADH300L / MM1914-1100 that I purchased from Hyperflight. Initially when using the recommended prop, it was only average at best, and on a 3S battery, it was not pulling the rated maximum amps.

Fitted a much larger than recommended prop (12" x 6" GM) and it now powers up perfectly, still only drawing 17 amps but giving 174 watts.

Todays best; 18 Minutes 25 Seconds

Circle Dancer Electric @ Fish Meadow.

 

June 30th.png

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Very light winds at Bracknell.  Bright overcast with strong lift at times.  Plot later but 24:25 from the Tx timer.

Purito-e 

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Two 'you're not down til it touches' moments (18 and 25m) and a peak altitude of 250m before I chickened out - look at the vertical descent with the brakes open.  24:45 airborne less 20 sec run allowance.

 

D11BCA1A-09E0-4015-A5E4-18FD0214929D.jpeg

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Graham Lorimer

Excellent recovery in the middle, well done.

You really do need at least two separate thermals to get a top time with a two meter. They are either too high for comfort or too far down wind to ride one all the way for 30 minutes plus.

 

Graham

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John Minchell

What is the expert opinion from the old hands at putting half brakes out and trying to stay in the same thermal but not losing too much altitude so you can still see the model?  Unless of course the wind is making you drift too far downwind as well.

John M

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cirrusRC

One option is as done here

The lift needs to be static and huge to dive down on full spoiler and then ride back up multiple times. It's actually good practice to descend and then try to find same lift, often it's just not there and it's all too easy to dive down too far.

At height with half spoiler it's very difficult to see what the model is doing in pitch.  Strong lift will easily override half spoiler and you will keep going up.

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StraightEdge
On 01/07/2021 at 18:29, Graham Lorimer said:

You really do need at least two separate thermals to get a top time with a two meter. They are either too high for comfort or too far down wind to ride one all the way for 30 minutes plus.

That's certainly the way it normally looks.

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martynk

Well done Mike. Great start to the challenge. Sorry for the delay responding

image.thumb.png.9768a793c6f465626e97dad3ea948b87.png

      

      

 

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Graham Lorimer

Hi Martyn

 

Please post this one in as well.

 

Another fine day of thermal gliding at Fish Meadow, 2 meter not much good in the morning, but only one flight was needed at 15.00 to get a very nice start to the Postal Competition.

Today was the turn of the ARTF Circle Dancer, and now with a bigger prop fitted to the ADH300L / MM1914-1100 that I purchased from Hyperflight. Initially when using the recommended prop, it was only average at best, and on a 3S battery, it was not pulling the rated maximum amps.

Fitted a much larger than recommended prop (12" x 6" GM) and it now powers up perfectly, still only drawing 17 amps but giving 174 watts.

Todays best; 18 Minutes 25 Seconds

Circle Dancer Electric @ Fish Meadow.

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martynk

Hi Graham

 

Will do. Mike pmd me yo let me know I had missed your earlier post. 

 

All a bit hectic. Very sorry

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martynk

Updated table and apologies to Graham for missing his first post.

image.thumb.png.f9cec579d5a2ee0f767d939c84f596f6.png

PS. Thanks for the tip about the prop/motor.. combo Graham.

Is the 12x6 on a 2s or 3s?

Martyn

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Graham Lorimer

I am running it on a 3S Martyn.

I do recognise that this is a lot bigger than recommended prop, but the performance is now excellent, and it is still drawing less than the recommended maximum amps.

There is probably some confusion on the Hyperflight website, the front mounted and rear mounted versions appear to be identical apart from how they mount, however the recommendations for each are quite different.

I can only say, in real world experience, this motor is superb on a 12 x 6 GM prop. It should be noted however, the 12 x 6 GM prop has very narrow blades, so not all 12 x 6 props will be the same.

Graham

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martynk

Thanks Graham

 

Have to admit I was not overly impressed using a 9x6 prop.. I'll try a bigger one

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Graham Lorimer

The interesting thing, I started with a 8 x 5 which gave 134 Watts drawing 11.87 amps and very average performance when climbing, I put a slightly bigger prop on, 9 x 5 and it gave 123 Watts drawing 10.97 amps. That made no sense to me at all.  I did not try flying with that.

So I put a 12 x 7 on that I already had, and it was mega. It drew 16.2 amps and produced 174 watts. Thought I better not go quite so big, so ordered a 12 x 6 GM prop and it draws 15.93 amps and gives 176 watts. 

Can not explain why the 9 x 5 gave such misleading figures, it should have been a little better than the 8 x 5, might have been the make of prop, it was a Vitaprop and the blades are wider than the GM prop.

Powers the model very well now with the 12 x 6 GM, so I would recommend that with a 3S battery.

GL

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AnthonyB

I have taken the time to write this because I am concerned where this is going. It is also off topic - I will risk it !

 

My first alert came to me because I am using a 2208 – 1000kv motor.

On an 8 x 4 it draws less than 4A (2s) and climbs at 2m/sec...... Too slow.

On a 9 x 5 it draws 6.4A and climbs just quick enough.

A 10 x 6 was too fast and so I have settled on 10 x 5 which is enough for 130m in 30sec....... At 8A.

You will note that on 2S that 8A is enough to get to 130m.

I have a few 2m heavier planes that do 200m in 30sec, but on 3S and using up to 12A........ Too much for F5RES.

So to see 16A on 3S, seems wrong. 16A into a 19mm outrunner seems wrong – I am using 22mm motors. I could understand 16A into a 4000kv motor – not a 1000kv one.

A 1000kv motor wants to run (@10v) at 10,000rpm.

It takes 200W to turn a (Aeronaut) 12 x 6 prop at 6,600rpm. At 174W you have to be well below 6,600rpm.

The manufacturers cannot get a 10 x 4.7 prop over 4,750rpm at 10v.

My conclusion is that this motor is being run below 50% of its kv – so it is less than 50% efficient. That means that OVER 50% of the power is heat – 87W trying to make smoke.

Please study the manufacturers data sheet …...... A 10 x 4.7 does WORSE than a 9 x 4.7......... So it is way off on a 12 x 6.

ADH300L.thumb.png.e2d87ab6f081b6e1fcd6d639b17ccf5d.png

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Graham Lorimer

Thanks for your thoughts on this Anthony, always appreciated.

The motor I use and refer to above, ADH300L is sold in two versions by Hyperflight, being front or rear mount.

There are two specifications on their website for what appears to be the same motor, and the rear mounted one, lists power at 170W with current of 17 amps.

Those specs / results are quite close to what I am running as detailed above, except I needed a bigger prop to achieve those figures. Figures quoting prop sizes can be very very misleading given the huge differences in prop performance, the 12 x 6 I am running on this motor is very thin in blade width compared to other similar props I have, photo attached that shows the 12 x 6 GM prop and a 12 x 7 Vitaprop also.

I have always been led to believe that the current draw in amps is the thing that must be kept within manufacturers spec, and I am under that with my 12 x 6 drawing 15.93 amps on a 3S battery. They have used a 9 x 5 to achieve those numbers, but it could well be that it was a very different prop.

The other thing I use as a guide, how does it go in the real world, and this goes very well. 

Maybe it will all end in smoke, but at £14 I can live with that, and I will report back.

Graham

IMG_3743.jpg

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AnthonyB

You are right Graham, it says that on the above chart – 15A or 170W.

It also shows lower down that a 9 x 4.7 at 10v gives 534g of thrust.

Then below that is says that the 10 x 4.7 prop at 10v gives 500g of thrust.

This lower thrust figure is because of the efficiency of the motor. The current has gone up from 9.7A to 12.4A – That is because the input power has gone up, the efficiency has gone down, and the final power to the prop is actually less.

Beyond that point, the larger the prop – the lower the efficiency.

As I said, you end up below 50% and you are using more power to warm up the motor than driving the prop.

So, on a 9 x 5 it takes 6.4A (at 7.2v =46W) and climbs at 3.37m/sec. The efficiency being >80%.

 

Climb3_37.thumb.jpg.2f531db92c025daa2f9424a379db414c.jpg

 

To climb a little faster, I have now gone to 10 x 5 which is 8A (at 7.2v = >57.6W) and got 4.26m/sec.

This is understandable because 3.37/46 x 57.6 = 4.219.

And it climbs at 4.26 on a fully charged battery.

Have you tried comparing the climb rate, with the various props, because you have a log of these.

Note I am talking about 6.4A (46W) and 8A (57.6W) …...... You are talking 150 – 160W. It just does not compute to me ? My motor cost more though £14.99, but the props were only £7.49.

Climb4_26.thumb.jpg.b820a2ab85ecd0a4db6b961f66d3d14d.jpg

 

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Graham Lorimer

Good morning

I can not explain the figures you quote above, I have seen that the larger prop gives less thrust, but I rely on real world performance, so I guess I simply do not believe the chart, as I also do not believe the figures on the Hyperflight website with the differences between the front and rear mounted versions of the same motor.  Is there a correlation between measured thrust as in the chart above, and Watts shown on a Watt meter? I find it interesting that the manufacturers testing only gets within 90% of their maximum Watts.

I have not spent the time required to compare climb rates with different props as I don't think climb rate is the winning factor I am looking for.

I find that with 2 Meter Gliders one of the advantages the bungee launched model has, is its likelihood of being lighter than a powered version, and in a slight breeze, the bungee launched model can climb higher on the bungee than a powered version can get, given that the height limiter on the powered version shuts down at 60 meters, no matter what.

But, with a model getting 170 Watts from its motor, in a breeze it is possible to cover a lot more ground upwind compared to the Bungee model during the first 15 seconds of the launch, giving the opportunity of finding lift and gaining height before ending up too far downwind, and facing the height sacrifice of returning to the field for landing or searching for further lift. So I look for a combination of speed and climb ability, the two combined give the best overall performance.

Graham

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I second the 'get upwind' comment.  My Purito-emf set-up can climb at more than 7m/s, if I point the nose up, so I can blast to 60m in under 10 seconds - but that's a waste.  My ideal climb would be at 3 m/s but at the best angle to cover as much ground as possible or to reach marked lift.

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