Ballerina by EarlyBird

[EarlyBird]

Today was the day for a maiden!

Here we are before

and after

and as everyone says it flew well.

Cheers

Steve

[Peter Miller]

Great.News!!

[Bob Cotsford]

Never doubted it would Steve

[john stones 1 - Moderator]

Magic, wants some lettering on now and a dancing lady to make it perfect.

[EarlyBird]

Thanks Bob,

I had no doubts either because of Peter's excellent design and during the build I felt that I had not made any significant mistakes.

John thanks also what I wanted to ask you specifically was regarding the centre of gravity position you used in your build. I have it balanced on the main spar which for me is too far forward and in flight it did feel nose heavy. So I am going to remove some lead from up front and try again. Is this a good idea?

Peter the lack of down/up and side thrust caused absolutely no problem, as you said. On take off with the gradual throttle increase there was not tendency to turn left and in flight once trimmed at half throttle at full throttle there was no obvious change in attitude just an increase in speed. Just the way I like it, perfect for me.

I only did one five minute flight because the motor was behaving strange. At home after some research and testing it looks like the ESC is in Heli mode,

I am well impressed and very very happy.

Once again Peter thanks for your excellent design!

Next is a dancing lady, pilot and some lettering.

Cheers

Steve

[Trevor]

Great! Always nice to hear of a happy conclusion to a build project. Congratulations Steve.

Trevor

[Peter Miller]

Steve

You will find that all my designs balance at 25% of the chord. One reason is that I use a slightly smaller than avarage tailplane. My tailplanes are 15% of the wing area. It works!!!

We did have one member of the forum who tried flying another of my designs with the CG at 30%. He said it was terrible but once he move the CG forwards to where I put it the model was perfect.

I get my lettering done by fastsignuk on Ebay. Very quick and excellent service.

[john stones 1 - Moderator]

I can't remember the exact figure for the C.G on mine, started at 1/3 of chord and had no issues, still a pussy cat to fly, my own personal opinion is Ballerina Isn't likely to misbehave if you shift it back to suit you.

[EarlyBird]

Thanks Peter and John.

I have some thinking to do.

Cheers

Steve

[EarlyBird]

After a lot of thinking about this

the issue is the amount of up elevator required. I was told that is because it is nose heavy. However as I have the balance point at 30%-31% of the wing cord and it is sensitive to the elevator, which indicates tail heavy, plus to correct this amount of up elevator trim will require the removal of a large amount of nose weight and push the balance point too far back. In my mind this therefore has nothing to do with the balance point location.

I could fly like this as it flies perfectly but I would prefer to correct this up trim and make it perfect. That way I will add to my understanding of how to set up a model.

Obvious question then. If not the balance point what could it be? or to put it another way what have I done wrong?

Cheers

Steve

[Trevor]

Decalage!

Put simply, relative rigging angles of wing and tailplane. Personally, I'd leave it alone. Since the tail has to produce a downforce for stability, the bit of negative camber introduced by your trim could even be argued to be improving its efficiency!

Trevor

[Peter Miller]

Even full size aircraft have variations in trim,

One extreme example. When I first joined the RAF my first posting was to St Mawgan where the School of Maritime Reconnaissance was based which actually flew Lancasters.

I was lucky enough as an airframe Mechanic to fly on three air tests after servicing. One of the tests was to stall the aircraft. They would pull the nose up until it just dropped and once the speed picked up it would fly away normally.

On one air test the aircraft refused to stall. They pulled the nose up and it didn't drop. It just wallowed and sank down steadily until they let the nose drop and then it just carried on flying. I am told that they never did work out why kit did that.

An extreme example but it just shows that apparently identical aircraft can have very different characteristics

[john stones 1 - Moderator]

Mine was fine, have a look at motor mount, maybe tilt up slightly.

[EarlyBird]

Thanks for the input Trevor, Peter and John.

Once I have sorted out the YEP ESC, I did not like flying in Heli mode, then I will adjust the wing incidence by packing up the trailing edge with 1/16" ply plate ( or is that down as it is a low winger? Hmm I guess it is.)

It does fly fine as it is.

Anyway this is interesting and adds to the fun.

Cheers

Steve

[EarlyBird]

Flew this morning having reprogrammed the YEP ESC so that is not in Heli mode also added the 1/16" ply plate too increase the wing incidence.

A really good six minute flight leaving 80% in the battery which is a 4000mah 4S. I don't think the ply plate made any significant difference to the elevator trim.

It crossed my mind that if I increase the speed then I can reduce the elevator trim, which makes it fly faster. So am I trying to fly too slowly for the wing loading?

Hmmmmm

Interesting.

Cheers

Steve

[EarlyBird]

After some more thinking I have decided that the 4000mah 4S battery is too big, both weight and capacity. It will give me over 12 minutes flight time, way too long for me. I was originally going to use a 2200 4S, I have three and nothing to use them in, but I was running out of space in the battery bay for lead so I used the bigger battery, it seemed like a bright idea at the time. The 2200 should give me 8 minutes which is ample. So the next step is to use the 2200 and place lead in the cowl for balance.

For me this is all very interesting.

Peter this has to be the easiest model that I have ever flown, to say I am impressed would be an understatement.

Thank you.

Cheers

Steve

[Peter Miller]

I flew mine on a 3S 3000 battery.

I don't think that I have had anyone fail to like the model and it was the mass build a couple of years ago.

Edited By Peter Miller on 29/09/2020 21:11:46

[EarlyBird]

You converted to electric?

How can anyone not like your brilliant design?

Cheers

Steve

[EarlyBird]

On 23/09/2020 at 19:39, EarlyBird said:

I will adjust the wing incidence by packing up the trailing edge with 1/16" ply plate ( or is that down as it is a low winger? Hmm I guess it is.)

It does fly fine as it is.

 

On 29/09/2020 at 22:08, EarlyBird said:

After some more thinking I have decided that the 4000mah 4S battery is too big, both weight and capacity. It will give me over 12 minutes flight time, way too long for me. I was originally going to use a 2200 4S, I have three and nothing to use them in, but I was running out of space in the battery bay for lead so I used the bigger battery, it seemed like a bright idea at the time. The 2200 should give me 8 minutes which is ample. So the next step is to use the 2200 and place lead in the cowl for balance.

 

Looking at the weather forecast on Tuesday it looked like Wednesday would not be ideal but the best for at least another week. I decided to fly the Ballerina, I had made some changes.

 

Wednesday charged a battery for the Ballerina and another for an MPX EasyStar, which I also wanted to test. For some reason I was late to the field and didn't get there before 08:00. There was a cold 13 MPH? NW wind giving a temperature of -2C with wind chill. Fortunately I had put multiple layers on. 

 

Flew the EasyStar twice without problems except I was finding it hard to fly when I shivering to the point that I could not hold the TX steady. I gave up and went home.

 

In the afternoon the wind was supposed to drop below 10 MPH so I tried again. Flew the EasyStar again while waiting for the wind to drop but gave up at 16:30. 

I was happy that I had achieved four good flights with the glider but a bit disappointed about The Ballerina.    

 

By 17:30 the wind dropped and back to the field by 18:00. 

 

Took off and immediately knew I had made a big mistake with the changes I had made, it was awful but managed to land and take it home in one piece. Nearly dumped it in the adjacent field twice but instinct saved me and the model, two years experience flying RC saved the day I started nearly three years ago but the last year doesn't count ?.

 

Now I need to work out why.

I tried the ply plate but did not like the look and it did not make a huge difference, I removed it. So I added some up thrust to the motor with one 3mm washer on both sides at the bottom.

This was the big mistake I think. With the added up thrust the motor was pulling the nose up which required less up trim on the elevator, which was the intention, however I found out that there is a downside in that when coming into land cutting the motor makes the model dive steeply and increase speed.

 

Remove the washers!   ?

 

I noticed something else when I was putting the model together the rudder was not in line which I adjusted. While flying I nearly ran out of up trim on the elevator and looking at the elevator afterwards there was very little up to see.

Zeroing the elevator trim gave obvious down on the elevator. ?

 

This is all very interesting to me as I do like a good puzzle. 

 

What is going on? ?

I will investigate further. ?

 

Cheers

 

 

[kc]

I would suggest checking everything BEFORE changing anything.   Obvious things like wrong model memory or CG altered might be the cause and need to be checked before changing anything.  

[Ron Gray]

And this is not a criticism but it does reinforce the need to check all flying surfaces before flying, I’ve been there!

 

Regarding changing the thrust line to overcome climb on throttle up, why not just add a mix to elevator to counter climbing? 

[kc]

Putting the model on a flat level surface and levelling the tailplane with a spirit level then checking whether the prop is vertical will check the thrustline.

Putting a pin in wing at LE and TE on chord line will help measure wing incidence by measuring down to flat surface whilst tailplane is level.

 

I notice that you fitted a smaller Lipo - I would check that it didnt move around and cause CG change in flight.

 

I noticed that your pic on 23 Sept showed  the rudder clevis which did not look fully clipped in - nothing to do with current problem but it might be a problem in future.  (It might just be an optical illusion but the clevis arms normally look parallel when fully clipped in )   Worth checking all clevis on this point. 

Edited April 8, 2021 by kc

[kc]

My rule is to not change anything until I have found the cause of the fault.   Once you start changing things the evidence is gone!

[EarlyBird]

Tomorrow looks promising which means I need to get on with putting it back the way it was to start with. ?

[EarlyBird]

Normal service has been resumed, I am pleased to say. ?

 

I removed the washers adding the up thrust. Removed some lead to reduce the 'nose heavy'. I am now back where I started and, all I need to do is fly it and get used to it's flight characteristics.

 

I don't think there was ever anything wrong. ?

 

Cheers