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2nd 2021 2m F3-RES, F5-RES 14 day Duration Challenge


martynk
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Pete in Northiam
17 hours ago, Allan Griffiths said:

No strong thermals but i seemed to have a reliable trigger which seemed to work for most of the flight. It was tight and was fun  playing with bank angles to see which gave what was seen by the eye the best climb!

 

 

That's a fascinating learning point for me.  

I watched a full-size glider for ten minutes on Friday while hiking in the North Downs.  It was at about 3000 feet judging from the cumulus cloud base, climbing strongly under one cloud, sprinting to the next then climbing again.  I was struck by how large its (clearly very effective) circles were.  I would guess they were at least five wing spans diameter, so maybe 100m if not more.  

I would expect thermals to widen as they rise, but at our typical 60m startubg altitude, any thoughts on how wide we can assume lift to be?  Or what determines the size?  

Had a poor day yesterday in any case.  No significant lift found and bust an elevator with a heavy cross-wind landing after not realising it was shifting all over the place.  Back to the board for repairs today.  At least my rx antenna are fixed!

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1 hour ago, martynk said:

Updated table following Allan's score.

 

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Don’t forget me 😄

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martynk

:) Sorry Guy,  I knew there was one missing. The most I have ever had to do in the past was 3, now its like Piccadilly Circus...

 

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Now updated, hopefully correct and sorted by score.. Some truly remarkable flights and its only April...

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Brian Taylor

Finally finished my Slite V2 F3-RES and popped out yesterday early afternoon for a test fly and trimming session. I suddenly remembered I had an old surgical tube bungee from the days of the BARCS postals so I cut this down to the meet the F3-RES rules. The surgical tubing looked in a bit of a sorry state so I was expecting a spot of bother. Test and trim flight went well though even after playing with the hook position the best launch height I could get was 45m.
The weather was an almost cloudless sky with a very light 3 -4 mph SE wind. On the last flight I found lift  and managed to squeeze 5: 53min from a poor launch. I am looking forward to some good flights once the new bungee system is up and running. 

Monday 20 April 21

F3 - RES, Slite V2

5 min 53secs.

Cheers, Brian

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Brian Taylor

Just spotted my typo on the date, flight was on the 19th April .

Brian

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Whitmore
20 hours ago, Pete in Northiam said:

I would expect thermals to widen as they rise, but at our typical 60m startubg altitude, any thoughts on how wide we can assume lift to be?  Or what determines the size?  

It varies quite a bit depending on conditions and the site topography and triggers. Often they are smaller earlier on in the day but get bigger as the sun strengthens. It can depend on wind strength as light winds can allow bigger bubbles to form before triggering. Then you also get 'trouser legs' where smaller thermals join one big chimney. There's a lot going on. But low level tight thermal turns with minimal loss of height are certainly the skill to develop, centring on the core especially. Watching expects like Tony Beckett (sadly no longer with us) working bubbles at deck level was extremely humbling!

Turning radius of a model is largely dependent on wing loading (lighter = tighter) but extra dihedral helps and also more cambered sections.

 

Jon

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StraightEdge

Just posted a question in the other thread https://www.barcs.co.uk/forums/topic/6809-f3-res-uk-competition-interest/?do=findComment&comment=182895 about setting up the launch height/motor-run limits for an electric model for the postal.

Would welcome any feedback, especially from Graham who is the only one currently flying electric in the postal.

Jon

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martynk

Welcome to Brian Taylor, nice to see you here.

Updated table.. Now 8..

It would be wonderful if we could get into double figures... :)  (I have almost finished my repairs).

 

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1 hour ago, martynk said:

Welcome to Brian Taylor, nice to see you here.

Updated table.. Now 8..

It would be wonderful if we could get into double figures... :)  (I have almost finished my repairs).

 

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Great to see so many participants. My time of 21mins would have been right up at the top last year 🥴

question for you. It feels like my MadRES once in a thermal practically flies itself and at the start turns in of its own accord. I thought the strategy was to turn into which ever wing lifts but I have more success continuing the turn opposite to the lifted wing. What are your experiences?

 

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martynk

I am no expert but I always turn into the stall, usually one wing half stalls then drops which is how you describe it.. Others more experienced may have a better explanation

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Graham Lorimer

I watch this thread with interest..........

The big downside of allowing an electric to run unlimited altitude with just a motor run timer, is that it would not be difficult to set up a 2 meter RES model that may weigh about 750 - 800 grams, but could possibly climb to 130 meters in the time allowed (ie 20 seconds), and that, on a slightly breezy day would be a winner I have no doubt.

My Purito struggles to get to 60 meters in less than 15 seconds, and if you want to get some distance to go with the launch height at 20 seconds, the climb needs to be very accurate. I notice some of the Bungy launches are getting over 70 - 75 meters, I would say that things should stay as they are, the big advantage of the electric, I can probably get more launches in a given period of time, so that increases my chances of finding the elusive lift.

The Altis Nano is not much more money than a Bungee, and if looked after probably retains its value over a season or three, whilst the bungee degrades and probably devalues with time. The Nano is very simple to set up, weighs only a few grams, so I think yer pays yer money and makes yer choice.

That's just my thoughts.

 

Graham

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42 minutes ago, martynk said:

I am no expert but I always turn into the stall, usually one wing half stalls then drops which is how you describe it.. Others more experienced may have a better explanation

So if the left wing drops you turn right on the basis that the thermal has pushed up the right wing abs turning right should take you into the lift?

whereas I do the opposite but probably circle round into it 

 

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Whitmore

Good point Graham - I hadn't thought of the over weight/overthrust option. What motor/battery do you have in your Purito?

 

15 minutes ago, GuyB said:

So if the left wing drops you turn right on the basis that the thermal has pushed up the right wing abs turning right should take you into the lift?

whereas I do the opposite but probably circle round into it 

In theory the wing nearest the thermal will be experiencing greater angle of attack and so roll away from the lift. I think Martyn is describing where that AOA is so extreme as to cause asymmetric stall then wing drop - which would have the model to appearing to roll towards the thermal.

A well designed wing should roll away in most circumstances. Either way you're seeing an indication of where the lift is and you need to get into it. If the roll is extreme I tend to stick with it and circle back rather than lose height by fighting the roll. Possibly worth fighting it if the lift is small and low - it just depends :)

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StraightEdge
2 hours ago, GuyB said:

question for you. It feels like my MadRES once in a thermal practically flies itself and at the start turns in of its own accord. I thought the strategy was to turn into which ever wing lifts but I have more success continuing the turn opposite to the lifted wing. What are your experiences?

 

Not hugely experienced yet but have so far found the following:  by following the turn started by the thermal kicking one wing up, speed and smooth flying is maintained and one gets quickly round back into the thermal, with the whole model then lifting nicely as you enter it squarely on.  Cranking the model the other way - ostensibly the shortest route - seems draggier and risks a slower-speed stall just when you don't want it.

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Graham Lorimer
1 hour ago, Whitmore said:

Good point Graham - I hadn't thought of the over weight/overthrust option. What motor/battery do you have in your Purito?

 

In theory the wing nearest the thermal will be experiencing greater angle of attack and so roll away from the lift. I think Martyn is describing where that AOA is so extreme as to cause asymmetric stall then wing drop - which would have the model to appearing to roll towards the thermal.

A well designed wing should roll away in most circumstances. Either way you're seeing an indication of where the lift is and you need to get into it. If the roll is extreme I tend to stick with it and circle back rather than lose height by fighting the roll. Possibly worth fighting it if the lift is small and low - it just depends :)

I have a Hacker A10-7L motor / gearbox combination. Very lightweight.

On a 3S battery it draws 9.5 amps.

 

Graham

 

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57 minutes ago, StraightEdge said:

Not hugely experienced yet but have so far found the following:  by following the turn started by the thermal kicking one wing up, speed and smooth flying is maintained and one gets quickly round back into the thermal, with the whole model then lifting nicely as you enter it squarely on.  Cranking the model the other way - ostensibly the shortest route - seems draggier and risks a slower-speed stall just when you don't want it.

Sounds logical. I definitely lose more height trying to turn into it than going round 

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martynk

Regarding thermalling, my experience is with F1A glider which normally have the inboard wing flying at a slightly higher angle of attack. In a thermal or up current, the inboard wing will stall sooner, drop and the model will turn sharply into the stall.  Mined ewes, free flight gliders have much smaller vertical stabilisers and therefore less yaw control/damping.   I really need to get out and fly more.. 

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martynk
4 hours ago, GuyB said:

So if the left wing drops you turn right on the basis that the thermal has pushed up the right wing abs turning right should take you into the lift?

whereas I do the opposite but probably circle round into it 

 

No, the other way round, if one wing stalls and drops I turn into it rather than away as the model is trying to turn in that direction anyway 

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Graham Lorimer

I will always try to circle out of the indicated lift, and to complete the circle back into where I think the center of the thermal may be, potentially that reduces the energy and forward momentum loss, something you really do not want with a lightweight model.

Just my thoughts.

 

Graham

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StraightEdge
On 18/04/2021 at 16:56, GuyB said:

...came out of the thermal only when I glanced down at my timer and looked back up and took what seemed like seconds to find the model again. So bottled it...

Guy, I meant to reply to this earlier:  why not set your TX timer to give a voice-readout every minute?

Jon

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