Ballerina by the Old School Model Aeroplane Factory. - Page 3 - RC Groups
 May 31, 2012, 02:40 AM Registered User Ian, Sorry to read about continuing woes with this model.The original design comes from a very good stable and many have been successfuly built and flown over the years, so the isuue is "what's wrong with yours?" As George rightly points out this is a simple design and provided that you observe a few simple rules it should fly without any problems. Leaving the fin area aside for the moment assumuing that you have checked that there are no warps in the wing then it seems to me that the basic issue is the position of the CG. This should be checked very carefully to ensure that the CG on your model is at the position shown on the plan. As a double check I always calculate my own position of the CG as follows: 1) Calculate the wing area in square inches. 2) Divide the calculated wing area by the measured wingspan to give the average wing chord (in inches) 3) Calculate 75% of this average wing chord and measure this resulting distance forwards from the TE at the center of the wingspan to give the position of the CG. (Note; in the case of a simple rectangular wing like this one this is the same as measuring 25% backwards from the LE) If all is well this calulated position should more or less coincide with the position shown on the plan. This calculated position will enable you to fly a simple model like this safely and allow you to fine tune the model to your own liking without incuring any major truamas. I cannot emphasize too much how important it is to take your time when checking the position of the CG in the workshop before you venture out . I would also suggest that it is well worth checking the lateral balance of the assembled model to ensure that one wing is not heavier than the other. Last edited by Stan Rose; May 31, 2012 at 03:40 AM.
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Jun 06, 2012, 12:29 PM
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# Ballerina Centre Section

Hi Ian,

I'm new to this forum but have been watching your post with interest as I'm building a Ballerina myself.

I've read about your problems with dutch roll and the effect that dihedral and fin area and rudder movement may have upon it.

Looking at your photos of your wings I notice that the leading and trailing edges continue to slope down towards the centre, but my interpretation of the plan took the centre section to be flat. So although the main spar penetrates the centre section, the leading and trailing edges, plus the drag spar stop where the wing meets the centre section. The effect of this would be that your wing will sit slightly higher on the fusalge and need packing.

Building the wings the way I saw them on the plan with 2.75 inches at each tip, the dihedral brace was a better fit to the spars than shown in your photos although it did seem still to be at a slightly steeper angle.

So, I'm wondering if the wings are sitting too high this must have an effect on the handling. I also wonder what effect running the aerial under the port wing has on the symmetry of lift.

All being said, mine still is not finished but I thought I'd share my observations with you.

Hope you are not offended by my impudence

Regards,

Paul
Aug 23, 2012, 06:38 PM
Registered User

# ballerina

Hi Paul,just came across your thread on the Ballerina and wondered if you finished the model and how well it flew? I ask because im in the process of building the same one and starting to feel quite negative now i've read Ian's woes! I noticed on his he fitted a servo near the tail..my plan shows both in the centre section,where did you fit yours? Just joined RCG today and this is my first entry so if it doesn't make any sense i apologize. Regards karl
 Aug 24, 2012, 04:26 PM Registered User Not offended in the least Paul.............. I do think you have a point about the c/s of the wing, and mine is clearly wrong!, however, the aerial lead is not a problem(I have that working on at least two other models)............... I have flown it reasonably well with an own design wing with ailerons...............so the rest of the airframe is ok. No doubt about it, the dihedral is not as great as shown on the plan, but I think that is not the issue. Let us know how your build is going. Ian
Mar 15, 2013, 04:14 PM
Registered User

# OSMAF Ballerina First Flight

Hi Ian,

Very sorry for my outrageously slow reply to your post on this forum but I have been working away. At the time I posted to the forum I was in the process of building my fuselage and had covered my wings.

Then all stopped until after Christmas, and the Ballerina languished half built at home.

However, in the New Year, knowing that I was going to be at home, I was determined to pick up the Ballerina again and complete it.

Well, last night saw its maiden flight, and I'm happy to report that it flew showing no signs of the Dutch Roll that had been discussed in this thread.

I will say though that the flight perhaps could have ended better. I got low and slow on landing and stalled it about two feet above the runway, dropped in on its nose pushing the motor bulkhead back into the fuselage. Though mercifully it appears without other damage but I need to look at it properly.

Thinking about how the aircraft behaved, and what the reviewer in Q&EF said about his experiences, I think the C of G was a tad two far back. Certainly the Ballerina flies like a homesick angel with the throttle more than one third open, but did not want to come down with it shut. And I think that it was this in combination of me misjudging the roundout height that caused it to stall in.

This was actually my first self built RC model, having cut my flying teeth on Parkzone foamies, though I did build a couple of Keil Kraft free flight models in the 80's.

From my perspective building the Ballerina was challenging, though not impossible. But what really caused me the headaches were the lack of detailed instructions that came with the kit. Okay, building the airframe was straight forward, but the most critical part, installing and setting up the controls was not really covered at all and caused me to go through quite a few iterations before I settled on a scheme that I was most happy with. There wern't even advice on what the control deflections should be.

Worse still, I thought the photos of the control setup that were provided actually contradicted with what the plans suggested for servo placement etc, looking at the control they would not work.

So again I agree with the reviewer from Q&FE, that although this is a beginners kit, its not really pitched at the beginner, which is an opportunity lost.

In the end, mine flew far better than I expected, and now needs a repair and a little TLC. But I'm not going to blame that on the kit, and it will fly again, so I'm not unhappy with the end result.

I'll post some photos when all is back together and we have a decent day.

Many thanks,

Paul
Last edited by PaulHaliday; Mar 15, 2013 at 04:23 PM.
Apr 11, 2013, 11:40 AM
Registered User
Paul, I'm pleased to read that you have finished your model, and have flown her!...

That motor bulkhead seems to collapse easily..........maybe a good thing?
I re-glued mine with Gorilla glue, this foams up nicely for jobs like this , but don't use too much.

With an 8.5x6 Aeronaut prop, and a 3 cell 800Mh Lipo, E.Max cf2822 outrunner, and with a weight of 14 oz, I gave it another chance to" redeem its self".

First hand launch, and it behaved very much like the previous flights, however this was calmed down on the second flight by rating down the elevator and rudder inputs.
There was plenty of power, with about 50% throttle holding altitude.............On pushing the left stick, she would pitch up alarmingly,( so I have shimmed the motor mount for down thrust),
But even so I had a good 8-10 mins. of nice flying ,with good some good slow and low fly bys.
No doubt a 9, or 10 inch slowfly prop may be even better.?
Now, all this was performed with an old and cheap white foam wing, not the wood built up wing from the kit .
I had this around, and thought I would give it a go, as I had nothing to lose. I even cut some shape to it. See photos.
The dihedral was nowhere near as steep as the plan/kit, which surprised me somewhat.

Ian

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May 15, 2013, 04:08 PM
Registered User

# Ballerina Wing Mod

Hi Ian,

I quite like the shape of your wing, it kind of reminds me of a friends Slingsby Motor Tutor

When I built my Ballerina I wanted to use the stock motor kit as supplied by OSMAF but it was not available so used a 4-Max motor that Derek Foxwell suggested instead along with a 1340mAh 2s Lipo.

When it first flew I hardly had to touch the elevator and actually it flew very well 'hands off', which I guess is the free flight qualities of the design showing through. After it's undignified return to Earth the motor was sticking up at about 20 deg, so I confer with your thoughts about the motor bulkhead, and my fix was also with Gorilla glue.

Stupidly, I'd attached the nose weights to the outside as I'd not left a way to get into the nose to fit them, so the repair gave the opportunity gave me the chance to do this and restore the looks of the model.

I'm flying mine using a Spektrum dx6i and found the rudder, despite its small size very sensitive, so reduced the expo down from the default 60% to about 40%.

My Ballerina weighs in at a very porky 18.5 ounces and this did make me worry, but it handles it with ease. Being my first build I probably was a bit too generous with glue etc so this probably accounts for its weight issues. However, despite this and my general lack of skill in other places I think it's a tribute to the model that it's taken this all in its stride and was still a success.

I still wonder about the issue with your wings, wonder how it would fly with my wings attached instead?

Will try to attach some pictures so can see how mine turned out and appreciate my general lack of skill at building.

Cheers,

Paul Haliday
May 15, 2013, 04:12 PM
Registered User

# Ballerina Photos

Here are some pictures of my Ballerina

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 May 16, 2013, 08:10 AM So I'M meant to be in control? Looks very nice indeed, and especially in those colours. I have had the Ballerina plan for quite some time now, and it has always been 'the model I will build after.....' Really should get a round tuit.......
May 16, 2013, 05:22 PM
Registered User
Hi Paul, Good to read of your satisfaction with your Ballerina.

I agree the rudder is very effective for its small(ish) size.
My version weighs just under 14oz with a 900mAh 3 cell battery.

I have added red Solafilm to the underside of the wing, and yes, I would agree the wing plan shape
is pleasing!! Sorry Vic!

I see your pics taken at Lasham............Ah memories, I used to live in Basingstoke in a previous life, and some summer Sundays I would drive over with my daughter (toddler) and enjoy watching the gliders..............In fact I had my first glider flight *side-by-side* in a Kirby Cadet(i think?) when I was a Scout, around the time this was filmed:http://www.britishpathe.com/video/gl...uery/airfields............
My model Club organised an evening at Lasham a few years back, that was aided by a Jodel via Aerotow......fantastic.

Ian

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May 21, 2013, 03:25 PM
Registered User
Hi Ian,

K-13 'H', I have fond memories of, as I did my first solo in it about 15 years ago

Looks like you flew with Pete Masson, who later became a world gliding champion so you were well looked after.

You talk about the Air Scouts, their training base, as they called it; is now Lasham Vintage Glider Club, which has become a very vibrant organisation other the last couple of years. Parts of my Ballerina were born in the Lasham VGC hut during a very wet gliding comp, when it rained almost every day

You mention about how you fitted your new wings and how the controls were still over sensitive, well I now have a feeling that excessive control deflections may have been the root of your problems. Could it be that so much rudder input was applied, that the into turn wing was almost stalling? Could this have been the cause of your handling woes? In this case, reducing the dihedral would bring the handling back into a manageable form.

Whilst building the Ballerina, I could not help myself, so I bought the Lola kit about a month into my build. You may recall that I bemoaned the fact that no control deflections where supplied with the Ballerina kit, so I turned to the next best available thing, which was the Lola kit instructions which actually included suggested deflections.

These are to quote 'Elevator movement on initial flight was 5/16" up and down. Later reduced to 1/4" up and down. Rudder 5/8" left and right'.

I seemed to get slightly less than this with my setup, but managed to increase it using the travel adjust function on the DX6i.

So I wonder if I was lucky in my choice? Of course being a lifting tailplane, I wonder what the effects would be if the incidence was wrong also?

Other than that, I have no more ideas as to what your problems may have been.

In any case, I'm glad that you managed to arrive at a flyable model, even if the process of getting there was a bit of a frustration.

Hope you have many more happy flights with your Ballerina.

Kindest regards,

Paul Haliday

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Last edited by PaulHaliday; May 21, 2013 at 03:38 PM.
May 21, 2013, 07:12 PM
Registered User
Hi Paul,
You will love your Lola.
Mine is a joy to fly.
Only issue is a slightly sudden stall (at very low speed).
The washout at the tips is 100% necessary!

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May 25, 2013, 09:19 AM
Registered User
I like the Lola Warren, I almost bought it instead of the Ballerina.

I would be interested in your build of the LOLA Paul.............

Funny that you think that I may have had the rudder movement too great..............I was thinking the very same.
The pics show the max. movement, and as you can see its almost 25mm...............I don't think
the elevator is a problem.
Next time out, I will take the balsa wing as a "what if".............

Thanks for the info about Lasham, If i recall, we were invited by the Air Scouts, as we were common or garden regular Scouts. It was a weekend trip with an overnight bunked up in a static
Avro YORK....................very exciting for a 15 year old.
Sadly the YORK (civilianised Lancaster)is long gone!!!.

Ian

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 Feb 28, 2014, 08:32 AM Registered User Hi guys - I just spotted the Ballerina thread and, as the guilty party for the QEF&I review (!), though I might be able to add a little more background than there was space for in the review... I found the build quite straightforward, but found I did have to read the instructions a few times before finalising on my own sequence, basically following the suggested path, but relying a lot on previous building experience (suffice to say I have earned sufficient grey hair as a modeller!). I mentioned the lack of part-kit guidance in my comments at the end of the review. It's worth keeping in mind that the lightweight construction was for a freeflighter and very much of its time. For radio, we've become accustomed to heavier construction (particularly in the wing LE, TE & spars), to handle the 'control' abuse that we give our models (see the review comment about breaking the LE and the internal former and having to reinforce it with a cross support). A Ballerina builder, using the OSMAF partial kit, should keep this in mind when choosing their own materials - for example I laminated a (nasty modern, but lightweight) carbon strip into the spar (and arguably should have done similar with the leading edge, which snapped on a flipover). After release, sports freeflight models were designed to fly without disturbance from the pilot, so longitudinal and lateral stability were paramount design aims. The Ballerina has these in spades. These present as a strong angle of incidence difference between the wing and tailplane, plus the steep dihedral. Again, related to the era, smaller fins were tended to be used to eliminate spiral instability. The CoG could be rearward as a lifting tail was used, taking some of the flight loads. Modest power was used to maintain a gentle, steady state flight speed. Move forward 60 years and we add RADIO! The weight goes up (more with an electric motor and battery) and hence the speed has to rise to keep the beast flying. We also effectively muck up the original spec. tail incidence (+/- elevator control) and the tail trim (massively, with rudder control). What was a stable floating turn now becomes an over-done manoeuvre which throws one high dihedral angled wing forward into the breeze, initiating a vicious turn, requiring (over?) correction in the opposite direction, plus some elevator to maintain height. Sound familiar? The resultant flight pattern is not pretty and 'highly stimulating' to the pilot, but is really to be expected. During the first test flights, even with about half power, the Ballerina 'rocked' over into its turns and started a spiral downwards, classic symptoms of too much rudder movement, applied too quickly, at too high a flying speed, on a vintage style model with the main mass well below the wing (pendulum stability)! Subsequent flights used exponential control of rudder and elevator (control via personal thumbs, rather than electronics i.e. I learnt how to fly the thing appropriately!), to ease the model into the desired direction, without loss of height. I commented in the review that the electric motor was pushing out ~2x the power of the originally spec'd DC Merlin engine, even on 2 cells. I'd suspect a 3 cell LiPo would aggravate this. I felt the supplied 8 x 3.8 APC electric prop was too heavy. The 1000kV motor didn't spin up as fast as I would have preferred (but then I'm also used to indoor shockie flying with lightweight GWS props, which do respond quickly on similar kV motors). The supplied prop was rugged though, which may account for some of the extensive damage passed through the motor to the bulkhead/fuselage joint that previous folk have commented on. A 'prop saver' mounting would help this, but finding and replacing the rubber O rings will be a pain. A lighter weight 'consumable' slow fly propellor would help save the motor shaft and the bulkhead and, by reducing the rotating mass, also help reduce the torque induced climb (& potential stall) when turning left, or the torque induced dive when turning right (think WW1 Sopwith Camel torque/turn induced crashes). I've noted the same height maintenance/height loss situation during turns with my Ballerina. So, was the review fair and have all the folk on this forum bought into a duff aeroplane? Again, I think we have to accept the model for what it is (the aformentioned slower flying stable free flighter, from a very talented designer) and the pilots have to fly it accordingly. Yes, build it a little tougher to accomodate our current preferences regarding radio abuse, but try to fly it in the manner to which it was designed - i.e. soft & gentle. The model, pilot and ground(?) will all be much happier. My 2p worth. Roger T Last edited by RWT17; Mar 08, 2014 at 01:46 PM.
 Nov 09, 2014, 02:26 AM Registered User I purchased this kit some three years ago, and having built the fuselage I have now decided that having had this element hanging on a hook in the workshop for three years it's about time the model was finished. So I have returned to this thread to remind myself of the various issues raised. Having read the thread again It occurs to me that it would be helpful if Roger T, having flown the model successfully, could supply us with the final CG position and the Rudder and Elevator throws together with the dihedral that he found worked best. Are you there Roger? Last edited by Stan Rose; Nov 09, 2014 at 04:39 AM.

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