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Simon's 'Petiterina'


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With the very calm weather about to end I took my Petiterina up early this morning (Monday) with its 1500 mAh 3s fully charged for an 'endurance' flight. The object is not really to find out how long it can fly but to get an accurate figure for its current consumption.

With the gyro off (to save power) and just very gentle 'cruising' the flight lasted 35 minutes 32 seconds until the LVC was just beginning to make the motor speed 'unstable' rather than actually slowing down or cutting out.

The battery took 948 mAh to recharge (so its not really a 1500!) but doing the sums shows it was taking an average of just 1.6A

Not bad for a 40" sport plane with a thick wing, an open cockpit and big wheel undercarriage.

Now if I used a slightly bigger battery that had a 'true' 1800 mAh capacity I wonder if it would reach an hour. wink 2

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I did construct a battery box extension to allow a bigger 1800 mAh 3 s battery to be used but I was concerned that the Petiterina's soft & springy undercarriage might struggle with the 45% increase in battery weight.so I decided to try my newest & best 1500 mAh 3s 40C battery (it was bought specifically for the smaller EDF A4b and is the exactly the same size and weight) to see if that would get closer to its nominal capacity.

The weather this morning was almost perfect so another Petiterina 'endurance' flight.

Launch at 11:19 and I remembered to start the Tx timer.

Glide in at 12.19 (the LVC had cut in so the prop was stationary) just as the Rx timer started beeping continuously to indicate it had reached its 60 minute limit. smile

The battery took 1285 mAh to fully recharge although I fear going to full LVC probably did not do it any favours.

Still it does mean the average current consumption was just 1.28 A,

Silly really but I now have another plane to add to my "i hour capable" collection! wink 2

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Here I go again!

The new spinner has at last arrived. It will be used with a 9x6 'e' prop rather than the 9x4.7 SF it is currently using.

9x6_9x4.7

The new prop and spinner are rather heavier - 32 g against 12 g - and to make things a bit more complicated the spinner is 3 mm larger diameter!

For appearance the nose has been 'cut back' by 5 mm so the fuselage matches the spinner and the motor bulkhead moved back appropriately.

Mod nose 1

Moving the motor back will in part compensate for the heavier prop & spinner although by accident I discovered it actually flies a bit better with the CofG just a bit further forward.

Make good the top decking, a bit of paint and it will be ready to go. wink 2

Edited By Simon Chaddock on 11/10/2016 23:22:48

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The nose fully rebuilt with the spinner and its 9x6 prop.

Mod nose 2

The prop has pushed up the power up to 175 W from 120 and the current to 15.3 A from 11.4 but even so it still only represents a drain of 10 C on the battery.

The weight has increased to 14.3 oz from 12.7 but the power to weight has risen to 195 W/lb from 151! smile p

If the new prop enables it to fly a lot faster a bigger windscreen and maybe even a cockpit canopy could be beneficial. wink 2

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With the new prop it still flies very nicely. With its increase weight and forward Cofg its ultimate slow speed is maybe increased just a touch but the handling is noticeably improved close to or at the stall.

Sorry no video but that is another story.

The biggest difference is it much quieter!

Unless absolutely flat out you can now hear the 'whooosh' of the air frame rather than the prop and with its extra power to weight it goes vertical just as well!

And just to corroborate BEB's statement it also bunts quite nicely either as an inverted loop or from a push over. wink 2

.

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I was never really happy with my original windscreen and with the added performance available from the 9x6 prop I decided to do something about it.

New canopy

I doubt it will really make much difference but it is possible that "every little helps".wink 2

I suppose the next step is to totally enclose it with a removable 'Malcolm' type hood as I still need access to the Rx.

I make no apologies for no pilot. It is not a scale model, I am the pilot and I am not in the plane!

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Managed to fly the Petiterina yesterday with the new windscreen and as I expected it made no discernible difference either to speed or trim so its all down to looks!

Just out of interest I later fitted a 9x6 SF prop in place of the 9x6 E prop.

two 9x6 A

The 9x6 E prop draws 175W whereas the 9x6 SF (and its actually 2mm bigger diameter!) only draws 149W.

This is a rather bigger difference than I was expecting given the blade areas look fairly similar so the next test will be to organise a thrust measurement. Will the E prop deliver nearly 20% more static thrust?

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As the rain is lashing down at the moment my mind started to wander. In truth it has been wandering in the same direction ever since I built the Petiterina!

Question

"Would same Depron building techniques actually work for a 'full size' Ballerina?"

or put another way what would have to be changed to account for its increased size & weight?

It would probably have to have a removable wing although come to think of it my Depron Cessna Skmaster is a similar size and in one piece but then it has no undercarriage so it takes up less space both for transport and storage.

Now if I fitted the Depron Ballerina with light weight electric retracts it would actually take up a bit less space than my twin boom Skymaster!

Maybe a bit of design 'doodling' will show me just how daft this whole concept really is! wink 2

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