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F3B Electric


clive Needham
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Is there still a movement towards electric F3B?

This thread is implying that there is a need for expensive launch systems no matter where they are situated (on the ground or in the model), perhaps that puts newcomers off.

I am presently working on a drive set up for for a Calypso Contest that will hopefully get it to 250m within 30seconds or so, ballasted up to 3.5kg, which I would hope is OK for competing in F3B.

Whilst I am experimenting with props, batteries, escs and motors, I am aiming at the low, to lower mid-priced, part of the market.

After having played with a few motor types, I consider the Turnigy GliderDrive system to be the cheapest way of achieving problem-free launches of relatively zippy performance. Don't underestimate the need to get some airflow over these well engineered motors though!

As I am already involved in electric gliding, flying F5J and take part in the Bartletts League whenever possible with a 2.5m Organic, and enjoy winch launching in Multi-Launch Gliding comps (if others are doing likewise), where my 17-20yr old models are still occasionally competitive, (and having a couple of grandchildren that I am trying to enthuse in the hobby), getting round to finishing my eF3B model is taking longer than I had hoped. But, if my calculations are correct. and if you shop around, and providing these things will fit in your fuselage, then less than £250 will buy everything that you need to fly your F3B type model in the electric format -
a charger £13 eg http://www.ebay.co.uk/itm/New-iMax-B6-Lipo-Li-Po-NiMh-Li-ion-LiFe-RC-Battery-Digital-LCD-Balance-Charger-/400511859522,
a wattmeter £13 eg http://www.ebay.co.uk/itm/WATT-METER-LCD-60V-100A-Voltage-DC-Power-Analyzer-Watt-Meter-solar-PV/111483996597?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D32956%26meid%3D249d70e6dc52430dac1e838e43cd91d7%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D271948179075,
an ESC and programming card £67 eg http://www.4-max.co.uk/pp-tesc100a.htm,

some LiPos and connectors, £60 eg http://www.ebay.co.uk/itm/Overlander-4x-LiPo-Battery-2200mAh-3S-11-1v-30C-Deans-RC-Flight-Pack-/331601133784?hash=item4d34f7c0d8

an 1120kv motor, £30 eg http://www.ebay.co.uk/itm/RC-Turnigy-GliderDrive-SK3-Competition-Series-3858-4-6-1120kv-/131509623110

a spinner, yoke and a small variety of props £50.  eg  https://www.electricwingman.com/power/propellers.aspx

Hope this helps people decide to try eF3B.

Jef



 

 

 

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Hi Jef

At the last few contests more people have been flying electric than winch, so yes it's still on going.  I think f3b pilots are as tight as any other type of pilot, so if you can find a way do get a reasonably priced set up, all power to you. 

 

Tom

 

 

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  • 1 month later...

Have some flight test data now, for the 3m Calypso Contest and an 1120kv Turnigy GliderDrive outrunner in a can motor, running on a 3S1P 2200mAh pack and turning a 13" x 6.5" Aeronaut CAM Carbon prop and a vented spinner (and fuselage).

My hopes for getting the fat old model to 250m ballasted to 3.5kg within 30 seconds were not achieved, although in reasonable air, my cheap set up managed a climb to 270m at 2.8kg.

It may be possible to get a greater climb rate with a smaller diameter, but coarser pitch propeller, but I am in unknown territory here.

Can anyone tell me what weights and measures others are achieving, and what time might be reasonable for the climb phase? 

 If electric models have been used in F3B comps, what did they weigh, what height did they achieve and what time did they take to get there?

All information very gratefully received. 

Jef

 

 

ECC3mBV ready for e-F3B.jpg

ECC3mBV Trimming session No3 F1.jpg

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Well Jeff a stock F3B model Empty of ballast would be circa 1900 - 2100g.

My Radical Pro has 1.4kgs of ballast to give a model weight fully ballasted at 3300g for speed and fast distance.

My Cyril weights a spec over 2000g and has 1.2kgs of ballast.

Obviously with an electric set-up your not going to get the weight down to 1900g what with the motor, prop, esc and battery combination that you need to fit.

I would have thought that a FOSA electric with no ballast would be around 2500g Possibly plus 200g.

The heavier the model is the higher the wing loading for duration and then you will have to rely on exceptional piloting skillz to fly out the 10 min duration slot.

For distance and speed its not as critical as you are able to still drag the ballast up eventually to the cut off launch height easier then a winch launched model.

 

When I practice duration for F3B I always half load and fully load with ballast to make me work harder to get the climbs (The model will go up regardless if flown right !)

I have spec'd out my ceres lift with full ballast in a thermal from a winch launch. (Made for a very interesting dive !)

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As far as I know the Fosas were about 2100 to 2150g before electrification. I think they are about 2450g now.  Maybe less, I know you can get smaller batteries now.

If you were setting out to build a specialist f3b-electric model it could be lighter, as you would not need the same strength for the launch. What f5j models are to f3j, although they would still need to be strong enough for the speed task.

3.5kg is a pretty heavy  model and not necessary for most flying conditions, especially if you are starting out. 

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Mid november a wednesday at the sutton valence field, you me and tom, bring model and you can use our winches.
Some thermal, distance and speed practice.

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OK

I am on shiftwork, my only available mid-November Wednesday is the 11th.

Can someone check the names of the roads surrounding the field so that I can identify which one to go for... I have been caught out before trying to find "the sutton valence field"!

 

 

 

Edited by Guest
checked shift rota
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If the practice session is held on 11th November, following a short session in the workshop today, I will be able to ballast the electric Calypso Contest to 3.2kg.

It will be interesting (to me at least) to see the effect of the extra 400+g on the climb trace. Maybe Tuesday, weather permitting.

 

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I have a few questions, based on a limited knowlege of last century open class thermal soaring launched with a hand tow.

Q1: What sort of launch times are you getting from an F3B winch? 8 seconds maybe?

Q2: Do the current rules count the start of the flight from the moment the model comes off the line?

If the answer to these questions is yes then surely a 30 second F5J climb to altitude would be a disadvantage to the eF3B flier.

I'm asking the questions to see if I can figure out what sort of power system may be competitive, and at what cost.

Martin.

 

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Martin

a1) 8 seconds is a fair estimation. It depends on the conditions (windy less time on the line), but in that sort of order yes.

a2) yes in duration.  But no in speed and distance, where the time starts when you enter the course. 

 

Electric has an advantage in speed and distance in the entry to the course, as you don't loose the same amount of height as you drift back to the course compared to winching. If it's a low wind day you can end up virtually on top of the turn around on your launch, then you have to fly back 150m, turn around and then enter the course.  It can be even worse in a cross wind where you can end up near the turn around and away to the side, depending on where the course is. 

 

Edited by satinet
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I have a few questions, based on a limited knowlege of last century open class thermal soaring launched with a hand tow.

Q1: What sort of launch times are you getting from an F3B winch? 8 seconds maybe?

Q2: Do the current rules count the start of the flight from the moment the model comes off the line?

If the answer to these questions is yes then surely a 30 second F5J climb to altitude would be a disadvantage to the eF3B flier.

I'm asking the questions to see if I can figure out what sort of power system may be competitive, and at what cost.

Martin.

 

Good luck with that one Martin!

I have built my eF3B model, but still can't get the answers to the questions that one asks when trying to ascertain exactly what is required.

Nobody has been forthcoming with a target height, nor a time in which this is achieved. 

Model data is available in this thread for my set up, but until I have had a session on a field with a couple of F3b fliers, I won't know whether my system is of sufficient spec.

Jef 

 

 

 

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So, based on Tom's reply the eF3B may have a height advantage in the Speed and Distance tasks but anything up to 22 seconds disadvantage in the duration task when compared to a conventional F3B model.

From a position of ignorance I would have thought that in a mixed eF3B and F3B competition might that kind of balance out overall? 

Martin.

Edited by heli_bee
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There is no disadvantage for the climb, unless you cant get to altitude within the climb time.

For speed a distance, you have the drag of the prop at the front.

And thermal wise your model is slightly heavier so you have to work slightly harder in lighter lift !

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No - In f3b duration is flown in a 12 minute slot. Your flight time starts when your launch ends.

Electric flight time starts when motor cut off point is reached.

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 I have given up trying to attach a document to this post, which details the rules pertinent to electric F3B models, I am running Libre Office and have saved it as an Open Document Text.

If anyone wants the rules, PM me and I will email this file to them.

Alternatively, they can trawl the reams of rules in the BMFA website!

Basically, the CD will decide the height to which electric models may launch (and this my change throughout the event). 

This would explain why nobody was willing to provide me with the information that I required when trying to equip myself properly for the format.

The three pages of rules (which are ridiculously over complicated IMO) will probably prevent most people from wanting to take part.

Despite this, I am still willing to give it one go at a local taster session, if I my shifts allow me to get there, and directions are forthcoming.

Jef

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 I have given up trying to attach a document to this post, which details the rules pertinent to electric F3B models, I am running Libre Office and have saved it as an Open Document Text.

If anyone wants the rules, PM me and I will email this file to them.

Alternatively, they can trawl the reams of rules in the BMFA website!

Basically, the CD will decide the height to which electric models may launch (and this my change throughout the event). 

This would explain why nobody was willing to provide me with the information that I required when trying to equip myself properly for the format.

The three pages of rules (which are ridiculously over complicated IMO) will probably prevent most people from wanting to take part.

Despite this, I am still willing to give it one go at a local taster session, if I my shifts allow me to get there, and directions are forthcoming.

Jef

Here's a pdf and word document copy if it uploads OK!

E-F3B-rules (2).pdf

E-F3B-rules (2).doc

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 I have given up trying to attach a document to this post, which details the rules pertinent to electric F3B models, I am running Libre Office and have saved it as an Open Document Text.

Nicholls has already provided the files but all you needed to do in Libre Office was export as a PDF and then attach that. 

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Thanks Ian and Austin,

Had some urgent modelling tasks to do and I was running out of time, having just wasted half an hour looking through the BMFA website. 

It proved easier just to send it to my mate Ian ;), I can recommend that everyone should get a mate like that!

Jef

 

 

Edited by Guest
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The rules don't seem that complicated. Rules are always wordy - have to cover every angle.

Some of the rules are just clarifications of existing rules that apply to normal f3b (e.g one minute from launch in speed task)

Edited by satinet
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