Mitchell Howard

I'm trying to work out whether my transmitter (which needs 7.4-15V input voltage) is better off on a LiFePo4 pack or an 8-cell stick-type NiMH. I'm thinking a sealed NiMH pack from Overlander with a more obvious discharge curve negates the possibly inaccurate/uncalibrated internal voltage measurement that would lead to a LiFe pack hitting that steep voltage drop-off point without realising it. There's better early warning from the NiMH pack I think. What I'm thinking is, if I'm able to get a 4 cell LiFe pack, I could run 14.6V peak voltage, which keeps the voltage up in the transmitter and even on a LiFe pack that does hit that 20% value, I'll still be above 12.8V - the Tx will carry on working and I can get the model down safely. On a NiMH pack, 12V will be my peak, fading to 9.6V for the majority of operation, but by the time the pack is dead, say 0.9V/cell, it'll be beneath the Tx's minimum 7.4V. Which is the lesser of two evils? - lower in-operation voltage levels (NiMH) or the voltage off-a-cliff behaviour of LiFe?

I don't think I've ever weighed my trainer, but I figured it would be heavier than the Wot4. I think my bigger picture is being distorted by learning on a powerful trainer - Seagull Boomerang, 12*8 prop, quantumii 40, 60A ESC, 3700 4S 60C. At the time I bought the trainer I really didn't have a clue. Would be clever I think to get it on the scales and buy a wattmeter.

Hi Dan, yes, very new! I have an A test booked for tomorrow (weather doesn't look great) so really looking forward to getting some independence at the field. I've got a technical background, so the electrics hasn't fazed me too much, although a lot of the 'in-practice' vs theory lessons are still being learnt! Is it not correct to say I can shift more air with a bigger prop (thereby negating the lower RPM of 4S), fit a bigger motor to deal with the amp draw of the bigger prop, run a bigger ESC, say 80A, then give it 4S to better exploit the amps it can deliver - my packs are 60C 3700mAh - they should be able to deliver 222A - what am I missing, why do people move to 5S?

That seems like a really nice balance - I feel like the move to 5S is often premature, given amp draw being somewhere around 30-40A on 4S - the C ratings of the lipos and ESCs aren't being exploited enough by bigger props and motors. What flight times do you get on that setup?

Thanks for all the remarks, but I did end up finding an ARTF at ModellbauUK. Earlier in the thread, the recommendation was to buy servos from a known source rather than eBay/Amazon. Does that extend to buying 4max branded servos from 4max? They're not Futaba, but they seem to have a good rep for getting power systems right, and they're in stock and well-priced.

Apologies if this is a topic done to death. Following on from previous threads (**LINK**), I've laid my hands on a Wot 4 ARTF balsa and need to buy the power system. Ripmax say ESC 60A, LiPo 4S1P 4500mAh, Motor QuantumII 40 800KV but no prop suggestion. Ripmax also say .40 2-Stroke Equivalent Setup, 4S 4500mAh, 60A ESC, 12x9W" Prop. 4-max say PO-5055-595 (595KV, 58A max 10s), 4S 4500mAh, 60A ESC, Prop APCE 13x8. Edit - I've just noticed this motor is what 4max consider their equivalent to the QuantumII 55, also suggesting it needs a 70A ESC and 14x7 prop on 4S. Chris Foss site says very little other than .30 for docile 'advanced trainer' and .60 for a vertical climbing animal. I've already got some 3700mAh 4S (Zeee) and 5000mAh 4S packs (Radient) that I'd like to re-use, preferably the Zeee ones as they're rather affordable. I'm sure I've got a 12x8 prop somewhere too. I've also got a ZTW Beatles 80A ESC unopened. Can anyone provide any useful recommendations before I commit?

Is that struggling as well? I would have thought it'd have an enduring popularity, low barriers to entry etc.

Maybe it's my relatively young age, but I just don't see the problem - the internet is awash with reviews of hardware, dimensions, specs, performance, longevity, even this forum can be considered a model shop replacement in its own right - possibly even a considerably more impartial one, not having any products/stock to sell. The likes of hobbyking etc won't have much of a market if they don't educate people, but even that's achieved via YouTube, club members, fora, technical websites. Would be interesting to know what business Ripmax and J Perkins might have in the future with their website instruction of "buy from a model shop in our network" - eventually they might all be online, but that doesn't mean there won't be technical bodies employed by those shops to talk to people on the phone. Plenty of the model shops I've used are simply dreadful online - the place I bought my trainer from a year ago had a barely active Facebook page and no online presence. They were struggling anyway but closed over Christmas. Perfectly knowledgeable and nice people who simply weren't competing with the convenience and reduced costs of online sales. There's not really any excuse for it anymore with the wide availability of e-commerce platforms - I think it might simply be a case of being anti-change.

A clubmate and I compared the Zeee and Overlander lipos. The Zeee can be bought from Amazon, the Overlander I'm not sure but I understand it's more expensive - the packs were identical bar the label, down to the location and amount of tape holding the cells together inside the shrink-wrap.

That's true of the Intel Xeon server chips too. Depending on the Xeon model, it's just an i7, i5 etc binned for low energy consumption / cooler running.

I don't have the answer Matt but I'm interested to see if anyone knows also. I've got a couple of ripmax models that are calling for Quantum 40 and 55. I suspect there's nothing special about the Quantums.

Thanks Phil, didn't know BMFA had that. Having a quick scroll and it looks like a mixed bag - there's a foamie wot 4 on there but the usual story with regards postage, they won't do it for fear of damage. For those of you that have flown any wot 4 - have you also flown an Evolution Models Fusion 2? They're called a funfly model and wondered if they were anything like the wot 4?

I had an extended conversation with Colin Bliss himself earlier today - a knowledgeable chap who obviously cares about the hobby/sport. He didn't have the ARTF but it sounds like shipping a container from wherever the Ripmax ARTFs are made went from £1800 to £8000. I would buy used if there were any available in a good condition. I'm a little more confident about the build of the Wot 4 classic kit now - Colin helped me understand the model is sold as an advanced trainer and build instructions are commensurate with that level. It is something I've wanted to do, building from pre-cut parts. He was saying the classic is most comparable to Ripmax's ARTF. the kit version sold as the mk3 is a larger wingspan but not as well-regarded as the classic's wing profile. Regards the Riot, I don't really know much about it. All I can say is it's not the model that others have recommended. I think I'm plumping for the kit and despite wanting two models at the field ASAP, this weather's preventing me from getting there anyway! Thanks for your comments, Colin Bliss repeated your remarks about the feel of the classic kit. I think we're looking at 2-3months for stock of ARTFs.

Thanks Phil but that's the kit version. While I fancy building something in the future, the artf one is slightly bigger and has the electric pack. This might be the only way forward though judging by the stock issue. Has anyone on here for experience building this kit? I gather converting to electric isn't as smooth as the artf makes it.

Thanks both, good to know. I've compared the model numbers you've both given with those on the 4-Max website suggestion - looks like the spec is standard size, ball raced, metal geared. I've got to find a Wot 4 ARTF balsa now, nowhere has the thing in stock... Is there something I don't know about, i.e. a replacement coming?

Thanks Phil. There's so many servos on the market it's hard to know what to pick. I'll be setting them up as electric, so 4 each. Is it pointless to buy servos with extra torque or speed? With cars it has a direct and noticeable effect, but with planes the speed a surface moves must affect the model and I presume also the size of the control surface dictate torque required?

Hi - I've got an Acrowot kit to build up and planning on getting a Wot 4 - I believe they need standard servos, 4-off each model. I've only used Radient servos before on a trainer and I've no idea what the price-performance-quality balance is like. I suspect price is the winner. Can anybody recommend servos for the above models? I'm relatively new to aeromodelling - I used to race cars and the general approach was for the servo to have a huge force and speed rating. Weight was almost irrelevant.

Hi Karl - I'm a rank beginner having only put together a single trainer from an ARTF set - I've longed to build the regular Bee and have managed to find the pattern off the web. Did you buy a pre-cut kit from Clancy's in the USA? Or did you follow a plan?

See this confuses me even more - when I contrast this with what Frank said, you should be able to go to a 13x9, 13x10 prop and pull more amps on 4S and get the performance livened up? On paper, my 3700 60Cs can knock out over 200A. I guess flight time must suffer, but it seems very low to be pulling only 45A. How long a flight time do you get? Have you tried fitting a 5S pack at all? I've been told it's awkward and you have to buy a certain size pack. I wonder if that's old news and went out with the formal EP/GP mk2 ARTF. I guess technically I could fit the Quantum .55, the 80A ESC and the standard 12x8 prop, unless that would yield too little thrust? how much thrust is needed? I'm fully metric where I can be - how many Watts per kg is the right target for the Acrowot?

Thanks, that's interesting - wouldn't have expected so much of a change. I think I'm overdue buying a Watt meter and getting it checked. The club member who test flew my model did literally describe it as a rocket ship... The Boomerang default suggestion from the manual is "0.35-0.45 size, motor 35mm 835RPM/Volt, Prop 10x7, ESC 50A, LiPo 4S 3200mAh, so seems a lot less power than my LHS's suggestion. If I had a peak amp draw of 61A on my 60A ESC according to Ecalc, I'd expect the ESC to come off a flight excessively hot, which it doesn't. Does Ecalc suggest a run time expectation? I get a good 7mins. Reasonable then to assume the 5S setup doesn't experience the same losses as it tries to push the 12x8 prop, and it can push it harder at different revs. I found the same numbers Dick which made me panic - but the 80% figure must change based on sizing of other powertrain parts?

Hi all. I am trying to wrap my head around the differences in the power systems between my trainer and the recommended setup for an Acrowot I'm shopping for parts for. Seagull Boomerang trainer ~2kg AUW; APC thin electric 12x8E > Ripmax Quantum .40 800KV > ZTW Beatles 60A > LiPo 4S 3700mAh 60C. Acrowot ARTF; APC 12x8 > Ripmax Quantum .55 700KV > ZTW Beatles 80A > Lipo 5S 4500mAh 30C. I'm confused over the Acrowot recommendations; it has a larger motor albeit with lower revs, with a 5S LiPo, but the same prop - assuming both models are a similar weight, the Acrowot has only an extra 1300RPM. Is the trainer simply overpowered? Is the Acrowot recommendation underpowered?. My understanding is that the prop diameter and pitch creates the electrical load. If the 4S pack of the trainer can deliver enough power using a smaller motor on the same prop as the Acrowot recommendation, then in (my own) theory, that means the Acrowot should also run well on that system? Also, it seems my trainer (recommended by local model shop) exceeds the max revs recommendation of the thin electric prop by ~1000RPM. How much, if at all, of an issue is this? What am I missing? I've seen a recent electric Acrowot on YouTube with an inch larger diameter; Motor Turnigy Air L5055, 700kv Prop 13 x 8 APC Power set up 5s 4500mah nanotech batteries 35 -70C Receiver Futaba R3006SB T-FHSS, battery 6.6v LIFE 1600mah. Servos all Hitec HS430BH HV

Sounds like this should be in a 'tales from the flying field' ebook! For helping learners, collated for educational purposes by the BMFA of course!

Wonderful thanks Bob!

I may be clutching at straws here, but does anybody out there own a Radiolink AT10ii or AT9? I have the AT10ii but I gather the menus and functions are largely the same. I want to start using/trusting the external voltage monitor PRM-01. It connects to the balance connector of the LiPo and feeds back to the R12DS receiver, which passes the external voltage down to the radio. I've checked that this is reporting an accurate voltage and it does, certainly under resting conditions. Now, obviously when the model is in the air, the last thing I want to be doing is changing focus to the Tx screen looking at the model voltage. The manual (Chinese translation) suggests there is a customisable alarm that may extend to the transmitter vibrating to tell you the threshold voltage has been reached. I can't find this in the settings of the Tx anywhere. Perhaps I should just fly the model off the timer but set an artificially high voltage threshold to see what sort of alarm it gives.

Hi - I'm close to taking my A test following some tutelage at my club, enjoying it all very much! One thing (amongst others) I need to lay my hands on is these posts that the horizontal tailplane would run into to prevent the model from running away. The search terms I've tried aren't doing anything for me. I have an electric model, but it seems like the general school of thought is that they should ideally be used for both IC and electric models.