Hey guys!
I'm the kinda adrenalin filled, trigger happy numpty that runs outta gas far from home and well, I want to change my ways, ie: have all planes return from missions.
My goal is to get the Mule to 12km and back on a single 4500 mah 4S pack and this test proves I can do it in moderate winds (less than 10km).
What pack voltage would you have pushed it to?
Out of interest I put back in 3534 mah. Does this actually mean I used less than 1000mah's??? Something's off! Also the voltage tested on the fully recovered battery was 15.3v.
HK Skymule / MFT Hybrid Efficiency Testing (http://www.youtube.com/watch?v=inq08rXzdW0#ws)
You want to leave 20% of the capacity inside the lipo to leave it undamaged. So you need 900ma left still in it. You put 3534 from 4500 so you left 966ma in it so you were right on the edge of the safe limit.
You put 3534 back into it Rich, not 966 ;)
Heres the interesting bit, you said your mah calibration was perfect on the MFD AP, but your summary shows 2479mah used, you put back in 3534mah so your current reading was over 1000mah out over a 4500mah lipo. Not accurate then.
This means you can not ( in its current state ) rely on the mah reading to know how far you can go. Try a re-calibration on the MFD AP like in my video to get it more accurate, then you can use the mah reading accurately to know when to turn back.
Your efficiency though throughout the flight was pretty good, a good speed at +/- 5 amps
Can you perform close in tests and record say, mAh Used per Km then extrapolate from there? Surely better than testing then failing and landing 2km out? heh.
Seems to me then that if you have a 4500mAh pack, you need to get your mAh per Km down to about 150mAh.
MAX:
4500 / 150 = 30km / 2 = 15km each way...
SAFE:
3600 / 150 = 24km / 2 = 12km each way...
Of course this assumes no wind ... a tailwind on the way back means more distance out but you already know that. it also doesn't take into account the climb to altitude which doesn't happen on the way back either.
Not trying to teach you how to suck eggs here, just seems to me an expensive and frustrating way to test distance is to crash miles out lol
In theory wouldn't it be possible to use all your mAh and travel 30km out as long as you a) got enough altitude to glide on b) a nice big tail wind? Risky though!!
Its all a big guessing game really. All you can do is get your mah and voltage readings accurate.
On any day the winds are different, what mah got you X km yesterday will now require double / half the mah to do that same distance the very next day, so there is no magic mah/km to be found. All you can do is have an accurate mah and voltage reading, try on several different wind days and work out a best guess on what range you will have on the day you go for it. Then use those readings to work out of your going to make it or not.
Quote from: Steve W on April 03, 2015, 12:04:18 PM
Can you perform close in tests and record say, mAh Used per Km then extrapolate from there? Surely better than testing then failing and landing 2km out? heh.
Seems to me then that if you have a 4500mAh pack, you need to get your mAh per Km down to about 150mAh.
MAX:
4500 / 150 = 30km / 2 = 15km each way...
SAFE:
3600 / 150 = 24km / 2 = 12km each way...
Of course this assumes no wind ... a tailwind on the way back means more distance out but you already know that.
Not trying to teach you how to suck eggs here, just seems to me an expensive and frustrating way to test distance is to crash miles out lol
Spot on Steve! You're right, the Darwin tests are absolutely unnecessary :)
At MD I got sucked downwind while trying to break cloud, so used a ton of power and got caught up in the moment with little battery left and a lot of distance with winds in the region of 20-30-40 against me.
Your numbers look good and make sense, but first as Ian says, I'm going to redo the voltage calcs to get more accuracy - at the moment it's about 1000mah off.
Cheers!
I guess if you know your airframes efficiency (mAh per Km) you can calculate the max distance based on the current wind speed at a given altitude.
Someone should write an app for that :D
Quote from: Coyote on April 03, 2015, 12:12:00 PM
Its all a big guessing game really. All you can do is get your mah and voltage readings accurate.
On any day the winds are different, what mah got you X km yesterday will now require double / half the mah to do that same distance the very next day, so there is no magic mah/km to be found. All you can do is have an accurate mah and voltage reading, try on several different wind days and work out a best guess on what range you will have on the day you go for it. Then use those readings to work out of your going to make it or not.
Ian I found a good CG with two 4500mah's in the Mule - gonna try that today. If it works then that's the answer for me :)
20k on a single 4500 battery with a 20% safety margin is damn good going I reckon.
That should give you a 15-17k range with two batteries.
I'm never really sure on voltage readings as an indicator of remaining battery life. My Voltage seems to drop like mad initially in a battery, then settle for 70% of it, then really plummet down again in the final 10-20%.
I find the maH consumed more reliable than anything. Although, if a battery loses its capacity over time- you may be running a new battery down to 20% remaining but an older one that has lost some of its total capacity, you may be running it down to 10% without realising whilst still putting the same mah back in.
I think it's good to know a planes glide ratio too. That way, assuming no wind, you have a good idea of how far you can travel should something fail. Climb 200m high and see how far you can travel.
My ruby osd shows time to get home (at current speed) and how long my battery will last (based on current draw and mah left)
It was quite reassuring to have a MD whilst 2km down wind looking for Rich's mule. When turning for home I had a 2 minute journey with 5 mins of battery. Obviously this only works if my batteries are in good health, and I wouldn't want to 100% rely on it.
The ezOSD gives live mah/km and an averaged readout to.
All the info is there, it just needs the osd manufacturers to implement it.
I use the "fingers crossed" method, works most of the time ;)
Or the tried and tested 'wet finger in the air'
Did I read you used to have a Twinstar? If so how does the Skymule compare?
Quote from: dp106 on April 03, 2015, 05:43:38 PM
Did I read you used to have a Twinstar? If so how does the Skymule compare?
Dp, it's a good plane, nicely designed and very robust - I reckon it will survive more abuse than a TS.
Having done a lot of testing now, I'm probably going to go for a MFT. The reason being this plane has a wider wingspan and designed from ground up to take a lot of MAH.
For a 1 battery plane (somewhere in the region of 5000mah 4S) I think it's very good, but with several caveats;
1. Ditch the horrible landing gear - it's heavy, non aero-dynamic, and very prone to digging in and just causing problems. Now that I've taken mine off I can take off on grass with the MFT power set very quickly.
2. The props and motors that come with it are useless - use the MFT power set up - $100 gets you two good 8000kv motors, contra rotating props, a very good UBEC with a 12v and 5v output which takes 4S.
3. Don't use exact CG for heavier plane on 4S - nose fwd by about 3mm does it.
4. Don'y fly slow and DON'T ever get into a spin :) Today I managed to save the plane while I was doing stall tests with 9000mah of 4S on board. It stalls at about 16km/h with a nose up attitude. Every single stall drops a wing and the spin develops very quickly after that. I took some video today and will analyse this a bit more - luckily I added full power and nose fwd and it recovered after about 5 - 6 jaw dropping seconds of absolute hell!
On the top side, it's better for FPV than the Twinstar (in my opinion only) because it has a very large inside. That's the only redeeming quality over and above the TS. The Twinstar probably has a better glide ratio and stalls at slower speeds, but not by much, they are prone to pretty much the same behaviour and bad tendencies if you get under speed.
All in all, it's a good plane but has a few negatives - one of my pet peeves of course is the split elevator which means it takes forever to get it straight and right. Slightly off and it counts as a small aileron on either side.
Will I keep it? Well, for now yes because I've got my best footage off it and as I said with 1 battery on board it flies well and theoretically can do a 12km return trip with throttle management.
I'll get te MFT next because it's entire fuse is basicaly a gear and battery bay and from what I see it looks like the wings have a tad dihedral.
Last thing that may save the Mule for me is the Multistar batteries - I'll try one for more capacity and low amp draw - this could be the ticket.
I've kinda wanted to make this the first decent Mule in existence anywhere in the world :) Just do a search of Skymule and all you see is LOS flights and some FPV very close in... Thought I'd change that, but... maybe not.
That's what's stopped me so far. It's been out for a while now and you don't really see any one flying far or doing fpv much for that matter. By contrast there are loads of Twinstar flights but I suppose it has been around a lot longer.
The Twinstar on the other hand needs a fair bit of modification and hacking about to get fpv ready. The MTD would be good if it weren't for the cost + shipping + potential import duty.
I ordered some Sunnysky 2212 1400kv motors that I was going to put on a Twinstar not sure they would fit a Mule though..
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Quote from: dp106 on April 03, 2015, 07:52:03 PM
That's what's stopped me so far. It's been out for a while now and you don't really see any one flying far or doing fpv much for that matter. By contrast there are loads of Twinstar flights but I suppose it has been around a lot longer.
The Twinstar on the other hand needs a fair bit of modification and hacking about to get fpv ready. The MTD would be good if it weren't for the cost + shipping + potential import duty.
I ordered some Sunnysky 2212 1400kv motors that I was going to put on a Twinstar not sure they would fit a Mule though..
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You have to get rid of the motor mounts that come with the Mule and make your own out of wood - I used about 4mm pine cut in a square to fit the nacelle and held on with Gorilla glue. It works well and there are no vibrations.
All things considered, the Mule is a great plane for FPV but it's comfy at 4500 Mah, no more (unless these Multistar batteries work out). That just means youre stuck in a 10km radius. Not half bad!
In terms of manners (at the right weight) and stability you can't beat this
Eclipse Flight 20 March 2015 (http://www.youtube.com/watch?v=gU_zNKxNjs0#ws)
Don't forget to re-glue both engine pods as mine both came off under power and ripped great lumps out of the fus' and wing. fixed now and is great apart from the above problem.
Using mine without u/c and hand launching.< I got big hands!! lol>
Cheers MIKE. ;D
Mike those hands must be huge!
I actually read your story before doing mine and I guess it's a poor design, however I think you bought the ready made kit if I remember?
I used gorilla glue for the nacelles and put them in using heavy duty skewer sticks (4 on each going right through and shaved off at the top of the wing) - mine aren't going anywhere!
Have you done any vids...? I'd love to see - as I said there is basically no evidence out there that the Mule was taken up by serious FPV'ers... Prove me wrong! :)