Jump to content

Some practical notes on an electric Ballerina


Geoff S
 Share

Recommended Posts

I know things got quite technical on the original electric Ballerina thread so, after 7 successful flights with mine I thought a few brief notes might help new builders of this delightful model.

First, I went along with BEB's suggestion and installed a Turnigy Aerodrive 4240 740 rpm/v and Turnigy Plush 60 amp esc. This has proved to be much more than adequate. In fact a lower power motor would be OK but really there's no point - you need the weight so why not have it do something useful? I'm using 4S 4000 mAH LiPos which give tremendous duration - a lot more than I usually need and an easy 10 minutes and more aerobatic flight (with some throttle management but probably even without).

To achieve the right CoG it has been necessary to push the battery as far forward as possible, though I think a CoG slightly rearward of that indicated on the plan would be OK and make the model more lively. I tried to get the weight down at the back by using built up surfaces for the tail but I still had difficulties getting it to 3" back from the L/E.

The maiden was done with a 13x6.5 APCe propeller which draws 40 amps from the battery for a power consumption of about 650 watts. This provided blistering performance with my 5lb Ballerina. Unfortunately I nosed over slightly on landing and damaged the tips slightly (OK the prop is now a 12x6.5). I've now angled the undercarriage forward a little more and that's helped the landing.

For the remaining 6 flights I've used a 12x6 APCe (not the trimmed 13x6.5 btw) which draws 30 amps for a power consumption of 450 watts and 8,750 rpm on the prop. Now that's roughly 90 watts/lb, below the accepted 100 watts/lb for aerobatic flight but OK for flying around. Think again! I get a very quick take off on less than full throttle and perfectly acceptable verticals, big loops, axial rolls, sometimes really nice stall turns (but that's me not the Ballerina) and generally excellent performance that satisfies me. The only thing I have a little difficulty with is spins. It tends to spiral dive before falling into the spin. It recovers instantly when the controls are centred. Perhaps moving CoG back may help - or more skillful flying.

I don't have any cooling for the esc and that's something to think about. But it's a 60 amp unit working at half capacity maximum and that only occasionally. It seems to keep quite cool at an estimated 35 deg after I land so it's not a serious problem.

I find I have almost 50% of the battery remaining after 7 or 8 minutes flying. Mostly mild aerobatics and a couple of touch and goes but a smaller battery would probably mean just less battery weight but some lead as well. So better stick with useful ballast.

I'm toying with the idea of making longer undercarriage legs to accommodate bigger diameter props and keep them clear of the Tarmac but it will wait for now. I'm having too much fun.

This is just to give a little information on how I find an electrically powered Ballerina using the motor esc combo suggested back in January. I hope it will give those hesitating to take the plunge a little confidence that it will work.

Geoff

Link to comment
Share on other sites

Hi Geoff,

Sounds excellent! I'm glad the system as proposed is delivering both good performance and endurance. I do know that I have a tendancy to "over-spec" electric systems and create set ups with more power than needed. But I always feel its far better to have a bit too much power and throttle back - than the struggle with not quite enough power! Also down prop-ing (or simply throttling back) just gives you even more endurance of course!

You certainly seem to be enjoying your Ballerina anyway! I need to return to mine very soon - as soon as a gap appears on the bench and flying stops being the number one choice while the weather is good. (Can't say that about today - rain and wind!)

BEB

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...