My attempt at a SebArt Mytho S 50E

[MattyB]

How are you powering the RC in this model? I really do not trust the inbuilt BECs for models of this size or anything over 4S TBH. If you do not have one already I would fit a separate BEC or RX pack; I have also added an Optipower Ultraguard to my Miss Wind as a belt and braces solution, and it saved the model on it's first flight!

[Colin Carpenter]

Looks good ! Well done ! Got 50 up on my 30 now . Looks great in the air. Colin

[Adrian Smith 1]

Matty, I went with the recommended ESC, the Hacker X -70 SB Pro as a start. I did look at the X-70 Opto Pro which would have required a separate RX pack. Not knowing at the start if I was going to have weight issue I decided to go with the lightest option. Part of the learning curve I guess, but something to think about.

[Adrian Smith 1]

Well Colin if I get to 50 flights I will be well pleased!

[Rich too]

Excellent Adrian well done I am always nervous in maiden flights.

Is that where you take off from? How do you dim the surface on those small wheels?

[Adrian Smith 1]

Rich, where the photos are taken from is my "pits"' the take off grass strip is like a bowling green which can just be seen towards the left of the last photo. And yes I am the one who mows it! The hard stuff is the old runway from WWll base where B17s used to take off from.

[Rich too]

Ah, I see now. How did you get it so flat? I cut the grass really short in the farmers field I use, but it remains quite rough and I have to use 5" wheels on my models...

[Adrian Smith 1]

Well it is the grass flying strip for a full size two seater a/c that was created some years ago by the farmer to go along the side of the old broken up WWII runway. The deal is the flying syndicate gets the grass cut by me with a ride-on mower and we coexist that way.

[MattyB]

Posted by Adrian Smith 1 on 29/10/2016 14:47:37:

Matty, I went with the recommended ESC, the Hacker X -70 SB Pro as a start. I did look at the X-70 Opto Pro which would have required a separate RX pack. Not knowing at the start if I was going to have weight issue I decided to go with the lightest option. Part of the learning curve I guess, but something to think about.

Personally I would still recommend a separate power supply of some sort. I know people are running that ESC as the sole power source, but above 4S I just don't think it is worth the risk - there are no specs as to what the max current that ESC can supply to your radio setup, and ESC BEC failures are a fact of life and do happen, especially when using higher voltage packs. Fit a separate 2S LiFe / 4S NiMH pack or a separate UBEC (the CC 10A one has a good rep) with an Ultraguard and your airframe is well protected from a power supply failure.

Edited By MattyB on 31/10/2016 13:22:32

[Peter Jenkins]

Well done Adrian! What I said in my post was elevator and aileron to 10 deg and did not mention the rudder. I should have said about 25 deg for the rudder for starters but the only way to sort out the aircraft is to fly it and see how it handles. Adjust from there. The rudder needs to be sufficiently powerful to perform stall turns. For spinning, you will need as much elevator as necessary firstly to stall the aircraft and secondly to keep it stalled while in the spin. I usually go for max rudder throw for spinning as well.

I agree with MattyB re using the ESC as a power source. I also have a 50 size electric and use a 2S Lipo through a Powerbox Digiswitch to provide 5.9 V output. This does not add much weight and you can probably site it on the CG or use it to move the CG around.

Do experiment with different CG positions as this is the single most important trimming tool available. Obviously be careful when moving the CG rearwards but provided you do it in small stages it is all very safe - you don't suddenly get a very twitchy aircraft.

As regards landing speed, these aircraft can slow up quite a lot. Try it at height at first and you'll find that it will fly quite slowly without a problem. I have no difficulty landing my 2 mtr electric even in a flat calm provided I get the approach speed right.

[Adrian Smith 1]

Peter & Matty, good advice all round thank you. What you suggest is all part of the electric learning curve for me. In my defence as this was a new leccy venture I did not want to load up the plane with "stuff" I wasn't sure about. However, this will change as I am already thinking about my next leccy project which will probably be something from the Extreme Flight stable at 60" plus. I will get a few for flights in with the Sebart using a bigger Lipo say 4500 mah as recommended. Funnily enough the Extreme Flight planes I am looking at suggest Lipos up to 4000 mah 6s which will fit the bill with what I already have (3800). I am still flying my petrols which is my first love, but I must admit leccys are growing on me!

[Adrian Smith 1]

This may seem a obvious question Peter, but what would the wiring connections be with a Powerbox digiswitch? Obviously at the moment I am using just the lipo connected to the motor via the ESC with the rx lead plugged into the throttle channel. With a separate power source for the rx how would the connections all work. Thanks. By the way I increased the rudder throw to 20 degs which seems OK for now.

[MattyB]

First remove the red wire from the ESC plug and heatshrink the exposed connector (don't cut it off in case you want to use the ESC BEC in future). Reconnect the ESC to the throttle channel on the RX. Then connect the battery to the digitswitch and that in turn to a spare channel on the RX - job done.

Edited By MattyB on 01/11/2016 19:41:13

[Peter Jenkins]

Hi Adrian - Matty's beaten me to it!

BTW, if you are in the market for another leccy bird, you might want to take a look at the Bondaero site. They offer a range of aircraft from full F3A to 120/70 sizes plus some IMAC stuff.

The question is, where does your interest lie? F3A, IMAC or 3D?

[Adrian Smith 1]

Thanks Matty you are a gent, appreciate that and all is clear now.

Peter, I am really a F3A man, not really into 3D though although some of my aeros get a bit improvised sometimes. I will look at the website you suggest though. Thanks.

[Peter Jenkins]

Adrian, I asked as you said you were looking at Extreme Flight aircraft and the only F3A aircraft they produce are the Vanquish in either 50 size or the 2 mtr full F3A bird, with which I started flying F3A competitions. Talking of which, are you intending to enter any precision aerobatic competitions? I competed against someone flying an Angel 50 at Masters level and he flew well enough to win the league that year so a well flown 50 size machine can do the biz - you just need a pilot to keep up with it!

[Adrian Smith 1]

Well Peter, I am not really into competitions as such. I had enough of that during my working life so I just like to set my self a few goals at the start of the year as see what I can achieve and of course have fun!

[Peter Jenkins]

Agreed that comps do not float everyone's boat but you do learn so much from flying in one. You can enter a GBR/CAA comp without joining the Association for your first comp - just pay the entry fee which is £5 for a Clubman schedule.

Failing that, assuming you already have a B cert, why not try for the C Aerobatic? With the Mythos properly trimmed out it should be both good fun and improve your flying. Mind you, as it's flown like the B, i,e, not a schedule with every manoeuvre flown in front of the pilot (no end manoeuvres) it is easier than flying even the Clubman schedule where there is a manoeuvre in the centre and at each turnaround end. If you exit one manoeuvre wrongly, you compromise the next manoeuvre. With the C, you have time to sort yourself out while you fly a reversal to come back to the centre. You'll find the details of the C here.

[Adrian Smith 1]

Well I have some basic analysis of my first two flights from the other day. I have recharged the lipos (balanced charge) ready for tomorrow's session. Bearing in mind the batteries are both 3800mAh and both original flights were TX timed for 4minutes with landing at around 4 1/2 minutes, these are the numbers after recharge.

The first lipo took I hour (at 1C) and put back 2838 mAh which suggests capacity was depleted by 74pc with 26pc left in. The second lipo put back 2482 mAh on a balanced charge, but took 74 minutes at 1C which suggests more residual capacity left at 34pc with 66pc used. Clearly, throttle management was different, but I am not really sure what this all means other than a larger Lipo is required to increase duration. I am sure you experts will put me right!

 

 

Edited By Adrian Smith 1 on 03/11/2016 19:25:31

[Adrian Smith 1]

One other question for you experts - for a separate battery rx power source using say a 2s lipo what mAh capacity would suggest?

[Peter Jenkins]

Adrian

Firstly, the Rx battery. I used an 800 mah 2S Lipo for my Rx in a Monolog 70 (50 size really). That would be fine for 4 flights of around 10 mins duration.

I initially used a 5S 5000 pack, as I had lots of these from my 2 mtr birds, but that didn't provide sufficient oomph as the motor had a lowish kv of 465. I changed to a 6S 4000 mah pack and that did have bags of oomph and gave about 10 mins as well. In both cases, I was down to around 20% remaining.

I forget if you are using 5S or 6S but using a higher voltage allows the current draw to be reduced for the same power and keeps things cooler as well. 3800 mah on a 5S would be marginal in my view. From my experience with the Monolog, a 6S 4000 mah pack should give you between 10 and 12 minutes which is enough to fly any of the aerobatic schedules up to P17 with time to spare. You do need to pay attention to the power setting you are using as otherwise you will burn through the pack. It's easily done - as I have proved to myself on several occasions.

On my 2 mtr birds, the main batteries, 2 x 5S 5000 mah connected in series take between 3000 and 3500 mah per flight when flying the FAI P17 schedule but only after I'd got control of throttle management!

As regards charging time. Set your charger to stop at 95% capacity and it will almost invariably complete in less than an hour. Taking it to 100% takes much longer especially if there is a lot of cell balancing going on at the end. You really don't need the extra 5% with the right sized packs.

[Adrian Smith 1]

Thanks for that Peter. I am using 6S 3800s. The recommended lipo in the manual is 4500 6S, so I guess I am a bit short. The information on the RX battery capacity is very helpful as I will be putting my RX on a separate power source in future which is good advice.

[Rich too]

Perhaps, consider a 1450 capacity LiFe battery for the rx?  as they are much lighter than lipos. I just bought 2 x 2s 3,000mah LiFe batteries for my (petrol) Yak and I was amazed at how light they are.

just a thought

 

Edited By Rich2 on 04/11/2016 07:16:14

Edited By Rich2 on 04/11/2016 07:16:33

[Former Member]

[This posting has been removed]

[Adrian Smith 1]

Good thought Steve.

Rich, I had not thought about a LiFe battery. I will seriously consider these points. One thing for sure I am going to change the way I equipped the Mythos 50 and apply it to the next leccy project too. By the way I squeezed in two more flights today inbetween showers and did a few basic aeros to see how things went. The only thing to look at is the rudder sticks a bit on one of the linkages so back in the work shop tomorrow. Everything else seemed fine.