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Chilli Breeze from Sarik Plan, Electric Conversion.


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Re cutting identical fuselage sides etc. Cut 1 side and then use small bits of double sided tape to tape them togther and then cut the 2nd side using the ist as a template. But only use small bits of tape -perhaps half inch square. Otherwise it's very difficult to separate the parts! Don't leave the tape on longer than needed as it might be difficult to remove after many days.

Re torsion rod U/c      Make sure the slots in mounts are staggered by exactly the width of the wire to ensure the wires pass each other and a double u/c clamp will go over both wires.

Edited By kc on 29/03/2019 19:39:32

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Hi KC, Thanks - that sounds like the sort of thing I need to be doing. I will do it on my next build ( which will be starting soon, I think)

I did exactly as you described with the UC wires and now have an aeroplane with an undercart, and covering.

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All the hinges are made from covering film, giving easy movement and a good seal around them.

The hatch is finished too - the magnets are currently waiting for their epoxy to cure. All that remains is mounting the motor - using the Chinese mount I got from ebay for a couple of quid: and putting together a cowling for it, slapping on a propeller, hooking up the controls and programming the radio.

img_20190404_175256.jpg

It won't be ready for tomorrow though. ( But probably will by Sunday )

Oh and I made some transfers for the trim scheme:

img_20190404_175210.jpg

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  • 2 weeks later...

I really should have spent more time thinking about the cowl, rather than deciding "Oh I'll sort that when I get to it: I'll just make one up and slap it on." I'll be mucking about with it this evening then..

I mean I have started one but it's a bag of pants, frankly, so I shall start from scratch.

Anyway, as you can see, the motor has been test fitted, and fits nicely, giving an initial balance point in the right ballpark with a 4s 2200. I will be running an 11x5 which according to ecalc gives a current draw of 49amps at 640w - that should do I think.

 

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I have to say, Mr Delacole really knows how to make a good looking aeroplane. This thing looks like she is screeching along at 150 mph just sitting on the bench.

 

Edited By Stuart Quinn-Harvie 1 on 12/04/2019 18:48:04

Edited By Stuart Quinn-Harvie 1 on 12/04/2019 18:48:46

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Hi Nigel, I am using a PROPDRIVE v2 3542 1000KV with 4s and a 60 amp ESC.

I am still deeply baffled by prop pitches and current draw and motor balance - the 11x5.5 according to ecalc gives a slightly higher power output and power/weight ratio for a very slightly reduced flight time - I am ok with that but would be interested to hear other views and more info ( still learning and always will be and you very clearly know your stuff )

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With the exception of a cowling, here she is.

Yes the covering job is terrible ( I've never been any good at covering and it's the first time I've picked up a covering iron since 2006 ) but everything moves in the right direction, nothing is going to fall off and it's been for it's first flight. Which didn't happen, because the weather at the field was filthy so we mowed it instead, BUT she got some admiring comments, which was nice.

I am hoping to video the first flight either tomorrow or on Friday, so stay tuned if you like ropy flying.

 

The build was largely trouble free - the only cock ups being of my own creation. I will reiterate though that I really do hate the Sandwich method for creating tapered wing ribs. I suppose i could get used to it but it really does seem more gyp than actually cutting each rib individually, if less gyp to draw out.

Thanks to the advice I have received here I am learning a lot about electric power systems and have learned about plan building too. I have really enjoyed the whole thing, and along with the cardinal I built at the same time, I have gone straight on to my next plan build.

So yes, thanks all for all the help - you rock  

I am very much looking forward to actually getting her in the air...

 

 

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Edited By Stuart Quinn-Harvie 1 on 16/04/2019 15:35:27

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Nice effort Stuart. Looking forward to seeing and hearing how she flies.

If I am honest I don't fully understand the reason for moving the U/C arrangement. I have built and flown various versions of Chilli Wind & Chilli Breeze and have used the recommended position on the wings with U/C blocks set into the wings. I just think is it aesthetically more pleasing and of course faithful to Mike Delacole's design. I know it's a matter of taste and hope all goes well on the maiden. Here is one of my versions before I sold it last year.

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Hi Adrian: do you know looking back I have not really much of an idea why I changed the undercart. Should I build another ( highly likely ) I will go with the proper arrangement. That's a lovely example you have there - what other versions have you built?

And thanks for the kind words, and I will let you know how it goes.

Hoping for an improvement in the weather here...

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Hi Stuart. My first Chilli Wind, a long while ago now, had an old OS 40FP in it. Then I decided to build the Chilli Breeze and put equivalent to the now OS 35AX in it. The last two Chilli Winds were built for OS 46s. The Chilli Breeze had built up wings, although all the Chilli Winds had foam cores only because a mate of mine offered to make them for me. All flew extremely well and were a lot of fun - a long time before the reliability of electric flight equipment were freely available. I still have the plans for both somewhere ........ thinking

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Ah, a Chilli Veteran! If this one flies to expectations I shall probably build another - it's one of the best looking aero-planes around for my money. it got as far as the field before I had trouble with the radio not binding / dropping the binding so first flight ( weather looking good ) will be Friday. ( RX problem fixed thanks to youtube. I think )

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It'll be good at 3-3/4lb. From memory it's what my old IC powered version weighed in at, and that had to cart around 6oz of fuel at take off, and was perfectly well mannered come landing time.

You'll not be underpowered with 640w - quite the opposite I'd say, that's easily 150W/lb. With that 1000kv motor (it's a touch above the usual for 4 cells in a sport model) you could drop down to 10x6, maybe come down to around 500 or 550w, have a bit more flight duration (disclaimer - depends on how much you like bending the stick forward!), and quite likely a tickle more speed on tap.

11x5.5 vs 11x5 - The 11x5.5 shows more power than the 11x5, for sure. Electric motors can be thought of (very approximately) as a constant speed device. You give it 16V and it will attempt to turn at a particular rpm, regardless of the prop fitted. However, bigger prop = more power required to turn at that rpm. It's just the nature of the beast. Yes, there are more details to it, but that's the general gist.

Which is of course a complete different kettle of shrimp to an IC, which would spin faster on a lighter prop, often allowing the engine to ultimately put out more power.

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Very nice build and great colour scheme Stuart. The only thing I would suggest is using a larger liPo, perhaps a 4s 4000Ah. It would add about 180g (6oz.) to the all up weight but I think the flight times will be very short if you discharge down to 20% remaining using only a 2200Ah battery. I also think you will get more power from a larger capacity battery as you won't get so much of a voltage drop under load. It will be kinder to the battery too as it shouldn't get so hot. Good luck with the maiden today by the way.

Just my 2p worth.

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Well, that could have been better...

First though, thanks Nigel and Piers - Good info I will certainly take on board - both prop and battery wise. And thanks for the kinds words.

She flew - very well, at first. A friend shot some video which as soon as I get I will post as it shows the take off and, loosely put, the landing. Off she went like a bat out of hell and she certainly likes rudder input in turns so a proper pilot's model in that she does as she is told, no more, no less - very neutral but very responsive. I love her.

Sadly she started dropping apparent power and the motor got noisier, and something clearly wasn't right, so I called Landing and got her into wind and shut the throttle ALMOST completely, wanting to fly her in rather than cut and glide. This resulted in the propeller standing still. I was so surprised by this I lost concentration and orientation and steered her into the ground.

Damage to the motor, motor mount, and fuselage cracked where it meets the wing root. None of this is terminal, but I was baffled by the motor actually stopping dead, or rather the prop doing so. Off to the car to take stock and I noticed that the motor was actually entirely unsupported by the mount, all four screws being missing.

Now then, being no fule, as Molesworth would say, I had secured the mounting bolts into the motor's threads with threadlock, so this is baffling. as for why the motor was noisy and losing power then stopping I can only conclude that it was rattling around inside the mount - observe the damage to the motor at the front and the point where the can and , er, front bit almost join. More tellingly have a look at the root of the prop shaft: it's got melted alloy on it. Then have a look at the front of the mount: the motor has clearly filed a slot in it because the mounting screws were gone, and the finish of the mount is severely heat damaged near the hole for the shaft.

No wonder she started staggering. On the video you can hear a sound on take off that sounds a lot like a prop strike - although the prop is fine, strangely, so I am not sure at the moment whether that is significant. 

The only reason I can thing of for the screws coming out is that they were of the countersunk variety, where no countersink exists on the mount - could this prove a problem? The threads in the motor are all fine, so the screws very very definitely left the mount before the aeroplane dumped itself on the grass.

Oh all electronics are fine and battery looks ok too.

 

Anyway : here's the plan: fix fuselage and install 1/64 doublers over cracks, new mount ( but I will make it from ply and buy new mounting bolts with no countersink ) and recover.

 

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Motor mount - note the jigsawing from the propshaft hole up and to starboard.

 

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Port fuse side cracking and breakage - it'll go back together fine and I will be adding a 1/64th doubler on the outside from just forward of the wing root back to about halfway down the moment arm ( added wight, but not much )

 

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The motor - note the swarf from the mount around the base of the propshaft - it seems to be welded there.

 

 

So, onward and upwards.

Edited By Stuart Quinn-Harvie 1 on 19/04/2019 19:44:16

Edited By Stuart Quinn-Harvie 1 on 19/04/2019 19:46:01

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Well at least she flew, just a shame the naughty motor made such a mess of the nice new motor mount sad. Presumably the melted aluminium will clean off the motor shaft but is it still usable, will it rotate or have any magnets become detached? Have the windings been damaged by overheating? It sounds pretty extreme for the mounting bolts to let go in this way. To ask a silly question, the bolts were the correct size and thread for the holes? The countersunk screws supplied with the motor are usually used to attach a dural crusiform mount, so I would usually use cap head machine screws with a washer to secure the motor to your type of mount. At risk of stating the obvious, be careful to use bolts of the correct length or they will foul the windings.

Was vibration an issue? With the prop balanced some spinners can cause a lot of vibration, also, was the prop a close fit on the motor shaft (concentric)? Anyway, repairs seem well underway and I am sure you will get to the bottom of it.

I don't know whether you have a watt meter Stuart but they are a good investment particularly as you mentioned that according to Motor Calc your motor would pull 49Amps/640W (when it is rated at 47A in your OP!). The specs. of motors are often a bit optimistic too.

Finally, you also mentioned she 'likes rudder input in turns'. If you haven't done so already you could try dialling in some differential aileron (more up than down) to counteract adverse yaw and if that doesn't do it, some coupled aileron and rudder too.

Edited By Piers Bowlan on 20/04/2019 07:41:02

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Well Stuart I am so sad it came to grief after such a promising start crying. I won't add to the guessing game as to what went wrong as I sure you will get to the bottom of it yourself. Best thing is get on a repair it and have another go, as there is a lot to be said for the saying "if you fall off a horse, get back on as quickly a possible". Best of luck. Adrian

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Such a shame to get a nice plane damaged so early on. Getting the glue out & starting repairs straight away is the only thing to do.

Frankly i have never liked the idea of mounting a motor out on metal frame without any diagonals. Peoplle often mount on threaded rod and say it works well but there are no diagonals there either. Vibration is the problem no doubt. i much prefer to extend the ply bulkhead forward during the early stages - by extending the balsa sides and ply doubler. Once the model has been built its rather too late to extend the fus sides, but mounting the motor on a 6mm ply box and using the standard cross type motor back mount might be better than re-using the metal motor mount that caused trouble.

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Thanks everyone: I really appreciate the observations and encouragement. I have started the repairs - so far the fus is fixed, straight and strengthened, and I have begun a new engine mount from ply. New screws have been ordered from the rather good modelfixings.co.uk site along with a bunch of other stuff which will clearly become useful.

I think David's analysis seems to be the most accurate from the evidence before me - either way, I amticipate it being back in the air by the end of the week.

Cheers again folks.

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Nightmare!

Nothing to do but get her fixed and in the air again. At least the damage does not look too extensive. I suspect you're on to something with the countersunk bolt head point.

I have to disagree with Piers suggestion of a 4000mAh lipo (sorry Piers!) - I don't think the extra weight is worth carrying around. My dad flew the larger one on a 4S 4000mAh before offering me the airframe...

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Sorry Nigel you are absolutely right, reading some of the earlier posts I was thinking Stuart had built a Chilli WIND despite the thread's title - I should have gone to spec-savers. blush .

Still, 49A and 640W from a 2200mAh LiPo - Yikes!

All the mods sound good Stuart, looking forward to the forthcoming flight report and hope the weather Gods are obliging.

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No worries!

It's a high draw for that size lipo for sure. I start getting twitchy about going much over 10C, that only provides a nominal 6 minutes of full power and more like 5 minutes whenever I've measured a run. At near 25C that would be down around 2 minutes and I think battery resistance will start hampering performance too.

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I have to wonder If I was using ecalc properly ( or more likely reading the results correctly) : clearly a rethink was in order so I went back in and input the info again, here is what I got for 4s battery my motor esc and an 11x5.5:

Battery: 23.24c

Min Flight time 2.2min

Mixed flight time: 4.7 min

Motor Max Current 51.12A

Power 675 W

So yes, this is an issue

Recalculating at a 10x6 gives:

Battery: 19.13c

Min Flight Time: 2.7min

Mixed Flight Time: 5.3mins

Motor Max Current: 42.09

Power: 576w.

 

Looks like a re prop is in order Sincere thanks for the comments folks.

In other news, here is the fuselage repair: It's 1/64th ply either side on the outside of the fus. The repair was done in the jig to make sure everything stayed straight and the cracked sections knitted back together very well ( surprisingly so) before adding the doublers. dscf0014.jpg

 

A new mount has been fabricated from fly ( 6 and 3mm) and will be going in as soon as I can get the time to do it ( today, I hope ) and then the recovering job will finish it off.

 

 

 

 

Edited By Stuart Quinn-Harvie 1 on 24/04/2019 13:08:20

Edited By Stuart Quinn-Harvie 1 on 24/04/2019 13:09:58

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And we are back in business.

dscf0001 (2).jpg

 

Re covered, strengthened, new motor mount made of ply with cap head screws and threadlock.

Oh and I have dialled in some aileron differential.

All I need now is for Hurricane "Where do you think you are going with that model" to pack up and leave us with some nice weather.

Edited By Stuart Quinn-Harvie 1 on 27/04/2019 16:15:15

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