Carbon u/c for Lysander

[John Laverick]

Allan,

 

the aluminium undercarriage weighs in at 400 grams inclusive of spats, wheels, nuts and bolts etc.

 

I decided to get access to the batteries by going cutting the front of the cockpit off and boxing it with a bit of balsa to make it solid. I added a hatch clip on top to keep it in place and it all looks pretty solid.

I've just competed the U/C in ali as stated and the wings are complete but yet to be covered. the next job is the struts. the power train is pretty much the same, 600w with a 70 amp controller on 11 x 9 and 4s. or maybe if i can away with it a 10 x 8 three blader. I built from the cnc pack.

 

regards

 

John

[Allan Bennett]

That's looking good, John.  But have you been able to check the balance yet with the battery in the cockpit? 

 

One thing I saw when I visited OW was that the engine cowl has many lift-off panels, so putting one in the top for battery access is not going to spoil the scale-ish looks.

 

I found some litho plate in my bitsa box today, and some thin clear plastic, so I made up the inspection panels and windows at the rear, as per the photo in my 28/11 posting.  Next time I get some building time it'll be the wing struts -- wings were fitted yesterday, though they still need flaps and ailerons adding, and leading edges rounding off.

 

I'll be doing the all-black paint scheme as per the Old Warden plane.  Very simple

[John Laverick]

Not checked the balance yet Allan,

 just  finished painting the undercarriage spats and waiting for them to dry so I can stick them on. Must admit that they were the trickiest part of the build, the cut lines on one set are much deeper than the other which has meant one set is thinner than the other at the top. don't think you can notice it much without really looking though.

 Will post some photos when I've got them on.

 

Regards

 

John

[Terry Whiting]

Allan,  Yes there is only one exhaust pipe on the right hand side, quite a chunky affair about level with the undercarriage leg.  

[John Laverick]

Her you go,

 

a few pics of the undercarriage attached. I've added the wings and put her on the scales as you can see she comes in at just under four and half pounds, yet to add the flaps, ailerons, covering and the battery, so I should imagine she will be well within in the weight limit of six and a half pounds. As I said the spats were a pain but if you take your time and use plenty filler they do have a good look about them.

The cowl looks ugly with that big gap around the motor, I think I read somewhere on this thread that someone got a dummy engine cover for 4 pound odds, perhaps someone could tell me where they bought it from.

 

many thanks

 

John

[Terry Whiting]

John.

 

Looking very nice,

In answer to your question,  I puchased my dummy motor from=

PodiumRC   it's a Dhc Beaver, part No.  EFL 4539, price £4.39,  + P&P.

requires no reducing to fit.

 

I read you are using a 600W motor, would you mind telling me what KV and  it's weight ?

 

 

   

[John Laverick]

thanks for the info Terry,

 

the specs on the motor are 960kv, 69A, 220g. recommended model weight 2000-3900g a 12 x 6 gives 680w so for The lysander that's roundabout 110w per lb. I have read reviews on the motor and some people are saying that they can get a 5.5lb model vertical with it so i'm  assuming it's more than enough for the Lysander. I, of course will use a larger prop to make it a bit more sedate than that!!

 

John

[Terry Whiting]

John,

 Have you tried balancing yet, reason for asking, Tony N, had 420g of I/C motor + a flight pack under the bonnet, so we could be looking at a total of 500-550g, and your battery position is only marginally  forward of the recommended balance point .  

 

 

[John Laverick]

Not yet Terry,

 

but if I do struggle to get it to balance the motor mount is easly removable and I have the option of going down the same route as Allan. I'm using a ubec so I've no RX battery to add weight up there. One thing that doesn't bother me though is adding some lead. If the motor can lift the extra weight then the electric modellers sin of adding lead is always the easy option.

 

regards

 

John

[Allan Bennett]

Ready for maiden ... but the weather isn't

 

I've just finished everything but the spats and final decoration, so I'm going to maiden her without spats and decoration as soon as we get a good Sunday afternoon.  All-up weight including spats and 5S A123 battery and 4oz of lead in the cowl is 5lb 13oz.

 

I'm a little disappointed at having to use nose ballast, for I thought I'd built the tail a little lighter than the plan, using a hollow vertical stab, and covering the tail feathers with Solite instead of Solarfilm.  I doubt that installing the spats is going to change matters, for they're just about on the c.of g.

 

I'm using a 12x6 APC E prop, and it's drawing 31A at full throttle.  I have experience of a couple of other models using this power train and similar weight, so I'm pretty confident it's going to fly okay.

[Terry Whiting]

Allan,

 

Remember, ........patience is a virtue.   I do not think we will be seeing much

 maiden flight weather for a while, this damnable wind and rain is relentless.

 

A shame it required 4oz of ballast, but I think most will come out at about 6lb + mark. 

My dural undercarriage is 3.5oz  heavier than your home made carbon fibre job, which I must add you made a really good job of.

I'm using Tex which has a slight weight penalty of about 5g per squ ft. but it all adds up

 

TW 

Edited By Terry Whiting on 28/02/2010 09:56:27

[Allan Bennett]

Don't worry, I'm too old to be allowed out in the rain!  So, maybe I'll get the decoration finished, and even the spats, before the weather is good enough for the maiden flight.

 

I assembled the spats off the model, but the fit is so poor they needed quite a bit of body filler along the seam -- especially the port one, I think it was.  Anyway, now they're nice and smooth I'm making a mould of them so that I can replicate them in fibreglass.  I think I'll be able to save a bit of weight there.

[Allan Bennett]

Successful maiden

 

It was slightly breezy today, and very cold, but otherwise ideal for a maiden flight.  So, no more excuses.

 

Takeoff and climb-out were no problem at about 60% throttle, though I did then have to go to the limit of my trannie's up trim.  After a couple of circuits I felt the ailerons were too twitchy, so I switched to 70% rates and was happy with that -- I'll post the up/down deflections later in case it helps anyone.  The power-off glide was more of a dive, and putting the flaps down also caused her to lose height significantly.  A fellow pilot, an aircraft rigger in WW2, reckons all the symptons are of the c of g being too far forward, so maybe I can remove some of that ballast I put in the cowl.

 

Landing was reasonably uneventful.  I kept the power on just enough to produce a nice shallow glide without having to play with the elevator.  But she then nosed over and broke the prop -- maybe testament to the state of the rugby pitch I was landing on, or more evidence of it being nose heavy.  No other damage though so, all in all, a very successful first flight.

 

One worry is the wing servo connection plugs:  When I first rigged the model this afternoon one flap wasn't working until I wiggled the wing.  After landing, none of the ailerons or flaps were working -- presumably the plugs had been dislodged slightly during the landing.  The upward pressure on the wings during flight should keep them well seated, but I'm worried they might lose contact again during turbulence and, certainly, inverted flight is out of the question until I can resolve the issue.

 

I timed my flight for 4 minutes, and on charging the 5S A123 pack I find I've put back 1050mAh, so next flight will be timed at 6 minutes, and I might be able to stretch it to the 8 minutes that I normally get with the same setup in my Flair Magnatilla.  To save you having to read back through previous posts, the motor is an AXI 2826/12, the prop is an APC E 12x6, the speed controller a Jeti Spin 66, and the full-throttle current is 31A.

[Terry Whiting]

Congrats Allan,

 

I'm afraid even if I was ready for a maiden, this weather is a NO NO for me. My days

of playing the Brass Monkey are past .

 

After reading you ran out of up trim I wondered if it was an incidence problem, I must admit I had not checked the plan incidence.

In doing so I found it was 2.5 degree + on the wing, and zero on the tailplane. Can see no problem there, so as you suggested.could be a balance problem.

I think I will do some ballance point checks using the mean chord.

 

 

[Allan Bennett]

You're right, I mustn't rule out an incidence problem with the tail, though it was seated nicely in the curved cut-outs in the longitudinal members, and it looks okay.  Anyway, I'll only be taking out a small amount of lead at a time, to make sure I don't over-cook it.

 

I've just measured aileron movement, and it's 10mm up and down on my reduced rates, which gave a handling that I was happy with.  So now I'll be adjusting everything mechanically so that I can do without electronic rates and trim, and doing the roundels and lettering and, maybe, the spats, before the next flight.

[Allan Bennett]

Building was fun; flying not so ...

 

My Lysander has had five flights now, the last one yesterday ending in a severe crash.  I was always nervous flying it, first of all because I wasn't confident of the plug-in servo connectors I was using at the wing connections (they made intermittent contact if I waggled the wings), and secondly because of the tapered wing shape. 

 

Anyway, I changed the servo connections for the more-conventional plugs on leads hanging out from the cabin sides, which connected beneath hatches between the first and second wing ribs.  A bit fiddly to plug in, but all seemed well when I did my pre-flight checks.

 

So yesterday take-off was as per normal, if a bit exuberant (almost prop-hanging), and I poodled around the sky for about three minutes after throttling back.  There was a bit of heat-induced turbulence, but I was noticing one or other of the wings dropping significantly from time to time, so I decided to land.  On my turn to finals, the starboard wing dipped, nose went down, and I seemed to have no control whatsoever.

 

We found the model, nose down in a wheat field.  Not too much damage other than the front end, where my extension for the motor mount and battery bay seems to have acted like a crumple zone to save most of the rest of the structure.  Post-mortem checks before disassembling the model showed that all controls were still working normally, though I daren't check the motor until I've got all the muck out of it and turned it over by hand.  I did check out the battery though (5S A123) by flying it for a further 4 minutes in my Flair Magnatilla, after which it recharged as normal that evening.  My Magnatilla flights also confirmed the transmitter was not at fault, and that weather conditions were not sufficient to waggle the wings as much as I had experienced.

 

Thinking over the crash, all I can think of to explain it is that I was flying too slow, and was suffering the dreaded wing-tip stall.  Unfortunately, at the time that didn't occur to me, so I didn't try opening the throttle as soon as I experienced the wobbles.

 

The good new is that my carbon undercarriage has survived that crash, and my previous heavy landings, without any damage.

[Terry Whiting 1]

 

Allan,

 

So sorry to hear of your Lysander crash.

I fear you could well be right with your  theory. Many models are lost

in this manner. The sudden drop of a wing, usuall the left, and loss of

control is due to zero flying speed,  a stall.

 

Has the model behaved in a similar manner on previous flights?  or was

the almost prop hanging episode due  to excessive  elevator trim and flaps?.

Reason for asking I wondered if there was a possible balance problem!

 

[Allan Bennett]

Nothing changed from the previous 4 flights, other than the wing servo connectors.

 

Take off angle was due to exuberance, nothing sinister.  I had not noticed any wing-dropping on previous flights.  On this and previous flight I flew mainly with flaps fully up, though this time I did do a couple of tests at cruising height with them fully down (about 30 degrees) and experienced no problems -- some up elevator needed, and quite a quick loss of height, but nothing extreme.

 

Both wing tips dropped during the last flight (at different times), and the final one was definately the right one.

[Terry Whiting 1]

Allan

 

Your servo plug idea did give me concern, and pleased  to hear you change

the system before the crash or that would have been another uncertainty,

 

This wing waggle could well be the prelude to the terminal stall.

Although I added washout it still leaves me with doubts.

 

Terry