General Longer Flight Times

[Heliman450]

Hi all, this seems like a good place to start a chat about trying to get longer time in the air.

Compared to most here in the Forum I'm quite new to the hobby but picking up stuff very quickly. I've done some testing and here are my observations. Please feel free to develop as needed.........

I'm using 6S batteries on a T-Rex 550 and a T-Rex 700 (2 x 6S for the 700). I've had over 9 minutes for the 550 in my early days. This seems to have played a part in reducing the life of my first four batteries. After some feedback elsewhere, I'm currently flying for about 5 mins and consuming about 40% of the 5000mAh capacity.

Although I haven't flown the 700 very much it doesn't seem to be giving longer flight time despite having two batteries on board.

I've bought more batteries and can now expect a total of about 40mins in the air before re-charging them.

I would very much like to own a turbine-driven heli in the future when my skills improve but I don't seem to be able to find any evidence that the flight time would be much improved after investing the large amount of hard-earned needed to achieve it.

The way I see it I could stay with batteries and give up my turbine quest entirely unless someone here can show me the way to improve time in the air to over 10mins via the turbine route or any other come to that.

Over to you guys...................

 

[Boogs]

I think gas would give you the longest flight times of any power system. Turbines consume lots of fuel as do nitro engines. A negative side to gas (pre-mix) or nitro is the oil residue that gets all over everything, IMHO.

 

[Smoggie]

A wet fuel heli (glow, gas, turbine) will generally give you a longer flight time than electric, though gas probably has the potential for longest flight of all. This is purely because liquid fuels store much energy per unit of mass than batteries, plus combustion engines draw part of their fuel from the air (oxygen). But there is nothing stopping you from getting ten minutes out of a large electric heli if you are willing to sacrifice a shade of performance. Use large batteries and run low headspeed and ten mins is very easily achievable. The officially ratified FAI world record for a electric heli (a Modified Mikado Logo 600) is 2 hours 58 minutes, so ten minutes really is trivial.

If you are only using 40% of your battery then you can almost double your flight time instantly without making any change at all other than simply flying for longer!... As long as you leave about 25% in the battery all is good, in fact using more occasionally does no harm. There is no point at all in having a 5000mAh battery and only using 2000mAh out of it.

IMHO turbines are really more just for the engineering 'wow-factor' than for any practical advantage. They are very expensive to buy, run and maintain and need a shed load of field support equipment to operate. The turbine flyers I've seen spend far more time in the pits setting up and tweaking their turbines than they ever spend actually flying. They also dont really suit RC helis very well because they have very sluggish throttle response, they take ages to increase RPM so cant cope with the sudden load changes that aggressive RC flying demands. They are of course still awesome despite their practical shortcomings but if you really want to get maximum air time then turbines would be the very last thing you want.

For max airtime electric helis are hard to beat providing you have facilities for rapid charging at the field. Gas or glow might potentially seem to offer more flight time but they suffer the same increased downtime for tweaking and maintenance that turbines do, though not to the same extreme extent.

 

[Heliman450]

Hi guys, thanks for the feedback. I'm not sure where I picked it up but I've still got it in mind that the batteries won't last long when deeply discharged. I don't have a problem just flying longer but don't want to keep buying new batteries after only 40-50 flights.

I'm coming to the conclusion that I'm going to kiss good bye to my turbine dream.

 

[Smoggie]

Phil, You are right that deeply discharging LiPos is not good got longevity, but all that really means is that you should leave 20-25% in the battery.. Aim for 3.7-3.75V per cell measured after removing from the heli and you will be fine. This rule has served me well for years and I have batteries that are 3 or 4 years old with hundreds of cycles that are still doing ok.

I wouldn't want to put you off your dream of owning a turbine, they truly are awesome pieces of engineering and in many ways I'd love to own one for myself... But if your goal is maximum flight time with minimum hassle then from what I've seen of them it would be better to look elsewhere.

 

[Heliman450]

Hi Steve, I did some checks a little while back using my 550 and calculated some durations based upon mAh rather than cell volts. I don't do aggressive flying but even though got numbers varying from 8 to 12 mAh per second. Using your 20-25% of the battery capacity I work that out to a little above and below 8 minutes.

Yesterday, I did two flights to test my 700X, one 7mins and the other 8mins. I think my problem with battery life was not charging as close to the flight as possible and not using the fridge for early morning visits to the field.

I think that I've almost worked the turbine out of my system based upon feedback here. Not just the turbine heli itself, mainly the additional stuff to go with it like storing and transporting it etc. etc. The only one I'd really have liked to own is a Lama. Shame, but sometimes one needs to listen to common sense. Boring, hey?

 

[murankar]

Head speed and disk loading are going to be your key things to look at. A light weight 550 on 6s running at 2000 to 2200 rpm should net you some flight time. Now if you fly more than sport then no you may not see an increase.

At 2000 rpm on my goblin 570 on 3000 mah 12s packs I get about 6.5 to 7 minutes. I get closer to 6 minutes at 2300. I don't beat up the heli either. My flight weight is about 8 pounds.

 

[Heliman450]

Hi murankar, my head speeds are well down on both my helis. I haven't measured them but I'm running about 65% throttle and both are very stable in the hover when the wind is reasonable, although the 550 needs a bit more when the wind gets up.

I think that I've found the optimum combinations for now unless I put the flight time to the forefront of my next purchase and just look for up to ten minutes as the limit. Maybe a Goblin is the way forward, we'll see.

 

[Smoggie]

I've got a fair few 700 size helis and of them all the 700X seems to eek out the longest flight time on it's batteries. All setup for similar performance and using the very same batteries. There isn't a lot in it, but I think the 700X wth it's light weight and low drag all gear drivetrain does slightly better than some of the others.

 

[Heliman450]

Hi Steve, I think I got hold of the scale of the difference when my Excel sheet showed the results of my calculations 7mins 48secs to 8mins 20secs. Half a minute is nothing in the scheme of things. After my acceptance (almost) of no turbine-powered heli in future, I think I'll probably end up with the Velos Rotors 880 as my next heli unless anyone can persuade me otherwise. I just like to look at that gearbox and having two motors just seems soooooooo cool!

 

[Smoggie]

The Velos is an amazing heli for sure, I'd love to add one to my fleet sometime but I'd probably have to wait for one to show up second hand as i couldn't justify the new price.

If you want maximum flight time and minimum field equipment/hassle a gasser converted heli is maybe worth thinking about? They dont have quite the same power to weight as a glow (nitro) engine or electric but unless you are into very hard 3D they are more than powerful enough. They are unbeatable on run time and being a gas engine they should be a lot less temperamental than glow. They are kinda ugly though as the big gas engine and it's cooling fan and exhaust spoil the lines of the heli compared to electric, but maybe that's something that grows on you in time.

 

[Heliman450]

Could be................... only time will tell on that one. I'm still seriously considering the trailer as my best option. Vehicle ownership is very expensive here and rapidly becoming very anti-social, too. I just can't justify having a second car.

 

[Heliman450]

Hi all, unfortunately the weather's not helping much with the field time, however, I'm now up to 9 minutes flight time per battery using my 550 and a 48% throttle setting. This calculates at 1840 rpm for the head speed and 4380 rpm for the tail. I'm still able to do all the practicing I need at the moment and most important is that the tail authority is still good. This is probably a lot to do with the 600 tail boom conversion I did as per Steve's suggestion some time ago.

I'm waiting to see what the weather does today before charging the batteries from yesterday so don't know what the percentage is just yet.

 

[Smoggie]

The weather has been terrible here too Phil. Today actually looks good but of course I'm working. If the recent trend of the weekends being un-flyable due to wind and/or rain continues I'm going to have to change my habits and start flying after work.

 

[Smoggie]

.....I think I'll probably end up with the Velos Rotors 880 as my next heli unless anyone can persuade me otherwise. I just like to look at that gearbox and having two motors just seems soooooooo cool!

I've some bome bad news Phil. Velos Rotors have discontinued the 880, I guess the sales just werent good enough

The announcement I read said that they were focusing on the commercial/military UAV market for the moment. The announcement did say that they were "considering" a limited edition Velos 888 heli for the hobby market but it it happens at all it would be at least a year away. I guess it might be good to register interest in such a heli with Velos, the more people who show serious interest the better the chances of it happening.

 

[Heliman450]

Hi Steve,

I'm not surprised at all really. One needs to be a special kind of nutter to go for the 880. Hugo has made a reduction in his offerings but not enough to have made me jump for it. I decided to leave it until later this year anyway as I've got more than enough helis for now (if that's possible). My flying skills need to improve drastically in any event before considering a model that by my quick reckoning worked out at around 5,000 CHF RTF.

I'm hoping to order up my Soloshot 3 camera soon............ just need the final 'go for it' approval from the Chancellor of the Exchequer

 

[Heliman450]

Back to the original topic..............

I'm now getting 13 minutes from my T-Rex 700X during the cold weather instead of 18 minutes during the summer months. My 550 gets around 12 mins and my Goblin manages 9 minutes (haven't tried them during cold weather)

I expect all of them to reduce as my flying becomes more challenging and I need to step up the head speed to suit.

 

[Smoggie]

That's some very good flight times, roughly twice what i'm getting!

 

[Heliman450]

Yes, but my flying style is less than half yours from what I've seen LoL

 

[Smoggie]

I'm hoping to order up my Soloshot 3 camera soon............ just need the final 'go for it' approval from the Chancellor of the Exchequer

Phil,

You should probably check the user reviews before committing to the Soloshot 3. The initial reviews from other modellers who are trying to use them for tracking models in flight are less than great. The tracking speed and accuracy seems to struggle with the fast motion and rapid changes of direction of an RC model. The feedback i've seen was for planes but i'd expect helis to be similar unless you are just hovering/flying slowly.
It's possible that firmware updates will sort it out but buying one for videoing your helis might at this point be quite risky. Of the videos I've seen so far better quality can be achieved with a decent head mounted camera.

Here's an example:
It's a shame if it cant be made to work in this application because it' looked on face value really exciting.