Indoor electric duration record

[boffin]

Guys,

I can find no mention of an indoor FF electric 10m ceiling duration record and have therefore set myself the challenge of trying to beat 10min indoors.

If I have not searched well enough or if you have already done this, then I am sure someone will let me know. In the meantime, my first musings for model and power unit to do the job are:-

A coreless brushed pager motor driven from a single cell LiPo would be an obvious choice. The discharge curve of the LiPo is the issue to resolve as the energy input to the motor will decrease with time. So, a model trimmed for a very gentle climb will degrade to a gentle descent in a few minutes. The best that this system could manage would be about 3.5mins(I did try this). Help comes via the Zapper Infra Red controller from bobsworkshop.co.uk which splits the power to the motor into 8 steps (via pwm) and also offers multiple timed phases.  When the motor supply voltage degrades with time, the power can be ratcheted up one step. Alternatively, the motor can be switched off and restarted (in software)to keep the model off the floor and out of the ceiling.

The model will be a Michael Henriksen BUMP (B***** Ugly Model Plane) as I have flown this for 2 seasons and it is remarkably stable in pitch and yaw. It is a perverse choice with a wing loading just a little too high for comfort in a confined space. It bounces well, costs nothing to make, is done in 3hrs and is quite ugly.

The motor to power this will be a 6mm 4.5ohm Didel coreless, running an Xtwin propeller. If BUMP can be persuaded to fly on 250ma, then a 50mah battery (2.0gm) will run for 10mins (theoretical), so a 60 or 70mah will provide some headroom.

As above, The controller will be an Infra Red Zapper capable of load control and with custom software to slow the timebase to achieve 10mins. The flight schedule will contain both constant energy and on/off techniques.

Does anyone have any suggestions as to how this can be done or suggest improvements? I will be pleased to hear from you.

Regards Ian
Peterborough MFC

[boffin]

I tried  hard to reduce BUMP’s weight and discarded my usual 2mm Depron for mostly  0.05” Durobatic foam (Micron). The completed unfinished airframe came to 2.9gm but I rather messed this up using a printed tissue finish applied with Klear achieving a portly  3.5gm. Plain white Depron is an eyesore even for a record attempt and would be laziness on my part to leave it in this state.  A motor and prop pushed the weight out to 5.4gm.

LiPo and controller ordered and yet to arrive, will escalate this to close to 8gms which is IMO just a tad too much for indoors. I will see how far I can get with this setup but I feel a Mk2 model coming on with a geared 4mm pager and a 30mah LiPo.

All is not lost, I did however find that 1mm Depron is only 10% heavier than 0.05” Durobatic foam but less stiff. I cannot justify the higher cost of the Durobatic foam for this project, 1mm Depron is good enough.

Regards Ian
Peterborough MFC

[JefO]

Watching this with interest Ian.

One thought occurs, can you cut circular holes in the larger panels, particularly towards the wing tips?

As you cover top and bottom anyway this won't add drag.

Good Luck!

Jef

[PeeTee]

Great stuff Ian.

The suggestion made by Jef sounds good, and I've done this on outdoor FF tails, although in my case adding  tissue covering puts back most of the weight. If you are really serious about weight loss, because you are covering with tissue, you could sand down 3mm Depron to 1mm (ish). Much of the weight of the thinner gauges of Depron is in the skin, and if you sand both sides you'll end up with a lighter piece. However it may be floppier!

As an alternative to Klear, have you tried the waterbased quick dry urethane varnish? It can be thinned and may be lighter.

Good luck with your endeavours.

Peter

[boffin]

Pete, Jef,

Thanks for your words of wisdom. My preoccupation with my outdoor BUMPS have dulled the imagination and I have a heavy airframe AND a  heavy power unit. I have not sanded or drilled holes but have built a back up model (BUMP_Lite) in the Hanger Rat idiom using .025”(0.6mm) Durobatic foam and 0.7mm CF rod wing supports. Power unit is a GB05(Micron) 4mm pager motor with a 5:1 gearbox and a CF propeller. I much prefer my heavy BUMP600s but if needs must!
A weight comparison of the two approaches is as below showing with a bit of imagination and your help, the flying weight has been halved.

BUMP600s

Assembled wing 0.05” (1.2mm) Durobatic foam            1.4g
Tailplane  sanded 1.0mm Depron               0.3g
Fin sanded 1.0mm Depron                  0.2g
Fuselage 0.05” (1.2mm) Durobatic               0.9g

This gives a ‘white’ airframe of   2.8g or 3.5g tissued

Motor 6mm pager 4.5ohm Didel               1.7g
Propeller Xtwin                     0.4g
Battery 50mah LiPo                     1.8g
Connectors/conductors                  0.8g
Controller                        0.3g

Power unit weight of 5.0g

Ready to fly weight of completed model 8.5gm

BUMP_Lite

Wing 0.025”(0.6mm)  Durobatic foam               0.6g
Tail/fin/fuzstick                     0.7g

This gives a ‘white’ airframe of 1.3gm or 1.8gm tissued

Motor 4mm Plantraco GbO5 in 5:1 gearbox            0.8g
Propeller CF                     0.2g
Battery 30 mah LiPo                     0.8g
Connectors/conductors                  0.8g
Controller                        0.3g

Power unit weight of 2.9gm

Ready to fly weight of finished model 4.2gm   

This gives me 2 attempts per indoor meeting .....I can't break them both, can I?

Regards Ian
Peterborough MFC                     

[Bob Blackburn]

Well it has got me all fired up.

I downloaded and built a bump yesterday!

HOWEVER my bump is very portly
Orange ss 7mm with gws 2.5x1
1mm depron
and the all important 
ZAPPER

13gms 

I am at a small hall tonight I will report tommorrow

[JefO]

Hi Ian

Your Bump Lite looks the business.

If the airframe will take the extra weight, you can achieve the straight line power delivery you want and <8g with a second LiPo and a 5v regulator of the PLD-BAC variety at <2g.

Hope that makes sense,

Jef

[Bob Blackburn]

Well my Fat 400mm ws 13gm Bump flew very well.

on a setting of 5 it climbs at 45 degrees in a 15 ft diameter turn cruises at 3 and descends on 2 with a slight widening of the turn on 2

I have a 30ma cell in it and flew it several times throughout the evening without needing to charge it.

I doubt it is a record breaker but the finesse the Zapper allows had quite a few people surprised when I programmed in a touch and go.

Finishing at my feet on two consecutive flights was another crowd pleaser.

[boffin]

Jef,

A step up dc-dc converter is a good idea, which I will pursue as I have a couple laying around bought for another project which I have not got around to. They are a touch heavy at 2g but I intend to bench test to determine how stable the output is, what the conversion efficiency is and if they can handle the current of a 6mm pager. If it looks good I can search around for a light version. I dimly remember that they have a typical efficiency of 80-85%, but I could be wrong on this.

BTW, the subject is not new, the 2003-2004 SFA posts  tell me that Graham Stabler and 'Dr Chris' used step up dc-dc converters before LiPo when the recommended indoor micro power source was a 1 or 2 cell 50mah Sanyo NiCad......just imagine 3.5 or 7gm just for the battery!! I cannot as yet find any layout schematics but will follow this up as yet another means of controlling a small brushed indoor power source.

Thanks again for the idea.

I have Bobs controllers in the 2 BUMPS and will give both an airing this Friday at Oundle if I can avoid the Embers,Vapours, Palm Z and Piccoo stuff.

Regards Ian

[Bob Blackburn]

http://www.indoornews.com/modules/news/

Ray Harlan seems to be slightly in front of this thread!!!!

[mike]

Thanks for the link.

The pictures are at http://picasaweb.google.com/jeffrey.hood/CatIRecordTrials#

I have extracted a couple below.  I haven't seen Ray Harlan in 30 years but I think this is him - it's certainly an electric model.  There are more pictures at the link.

Regards

Mike F

[Bob Blackburn]

I asked Bob Selman about the subject and got this back after he copied Jerry Combs in:


Back when the class rules called for 2 50mAh Ni-Cad batteries the following records were recognized by the AMA.
 
Cat 1
Jr none
Sr none
OP 20:54 Don Slusarczyk
 
Cat 2
Jr 10:14 Claire Leitgen
Sr none
OP 26:28 Ray Harlan
 
Cat 3
Jr none
Sr none
OP 31:00 Ray Harlan
 
Cat 4
Jr none
Sr none
OP 30:30 Ray Harlan
 
The current rules use a single 10mAh battery of any chemistry.  I believe that Ray Harlan is the only one who has set a record under the new rules but I don't remember what it is at this time.  I think it is around 22 minutes.
 
Jerry

[boffin]

Ray Harlan, in the US, has posted a record time of 25m 22s with his indoor electric model. This makes my 10 min target a bit of a non event. Nevertheless, I will be continuing my endeavour as a journey of a 1000 steps begins with the first .

The model spec was.............

27" span 5.5" chord biplane
Custom made double reduction 25:1 ballraced gearbox
Battery 1 cell LiPo 10mah capacity
Propeller 5.8" dia x 4" pitch
4mm pager motor
15ma current draw
5gms , yes 5gms all up weight

Ray does not use a motor timer or controller and does not have a low voltage cut off device. He flies the LiPo battery contents out to complete the flight. He reports that he has measured less than 1v at the battery terminals at the end of flight but the battery appears to  recuperate and  accepts a full charge. When I do this its a bin job !

Ray has achieved close to 40m whilst fun flying.

Regards Ian

[Bob Blackburn]

I have now built an even heavier bump

145ma lipo
orange ss
gws 2.5x1


http://www.youtube.com/watch?v=eAo1Si6XH2M

This is a flight with a landing and takeoff about two thirds of the way through the flight

[boffin]

The weather defeated me and I never got to Oundle School as the place was snowbound. I did however get to Nottingham Uni Sports Centre this Sunday for a first play with the duration models. BUMP_Lite did not fly well at all, I got the decalage wrong and eventually broke the propeller. BUMP600 was eventually trimmed as I expect a BUMP to fly but I ran out of time and batteries and could only manage a meagre 3m 20s before end of play. Way off my 10m target.

The graphic tells all. BUMP just climbs on a 3 taking 40s to get to the ceiling. On a 2, BUMP takes 20s  to get within 1m from the floor.  This P3-P2 ‘phase’ can be repeated to get to just over 100s. From there, as the battery voltage degrades, P4 is needed to reach the ceiling with a P3-P2 return to the floor. Clearly as the flight progresses, ever higher power will be required. This will be a job for another day.

The lessons learned so far are……

1. As expected BUMP is a perverse model choice to use for duration attempts, glide is poor. A 125 % version is contemplated.
2. The calibration method is ‘make haste slowly’. I did not find it possible to guess the complete calibration correctly and could only judge one or two ‘phases’ correctly (60-120s worth)
3. On current trim, BUMP needs a fairly big hall to complete this exercise. Drift as always is a major hassle.

A reasonable start with more to come, regards Ian