Bar Fly Legal Eagle

[Skymon]

John
I read that these cabin type models fly right hand circles.
My other indoor stick stuff flies left, so I was expecting that to continue.
My feeling with this one was just let it go and what ever way it goes, adjust that circle...
I wonder if precession effect has any bearing on the turn direction.... with such big indoor props there has to be a resultant from that torque up front.

Many thanks for the kind comments, I'm relatively new to indoor, having returned to aeromodelling after a long lay off.

I'm really enjoying the whole precision of it all.

Best regards
Si

[piecost]

Thanks for the compliment John. The model should really fly well at that weight. My 3g models were so much better performing than my 3.4g example. A positive snowball effect I suppose.

With regard to circuit direction; we found that with LH circuits Legal Eagle models struggled to take off or even landed again with high turns and torque. Circling with torque tended to keep the model Earthbound. RH circuits gave more consistent, steeper initial climbs.

The circuit direction for stick models is critical in that the stick twisting causes wing warp to aid trim after launch.

With these full fuselage models this effect is not present. But the RoG introduces different limitations. Lots of torque is needed to take off (more than for a hand launch) but if you give too much the model may stall, torque roll and crash as its stability cannot overcome the destabilising effect of the propeller.

[Skymon]

Interesting info - I'll soak my stab off and add a bit of RH to start the turn.
Does stab tilt work as effectively on this type of model too?

What torque are you launching at?
I measure in g/cm, but I can easily convert

Looking at my calendar I think the 6th March will be my next session indoors.
I'm hoping to have a go with this model then.

Best regards
S

[piecost]

I employed 1/3rd partial motors under a 25' ceiling to simulate the over 50' height of the Brabazon hanger. Post 7 and 8 gives the motor and turns. I do not use a torque meter,  though it is a good idea. Scaling the torque from data obtained from testing gives me a launch torque of 11g.cm. This would put my model through the roof of a low ceiling site. Perhaps you could try motors ranging from 1.6g/m to 2.0g/m in loops from 22 to 24 inches.

I must try a full motor under the low ceiling

[Skymon]

Piecost
Was your 8" loop a 1/3rd motor??
SO a full one would be 24"?


Regards
S

[piecost]

Yes

[Skymon]

So... I had a go with the bar fly...
Not a great success.

Winding.
Well, that was different. I need some sort of yoke to hold the rear peg when I wind.
I'd not really thought about that so I didn't have one.
This meant I sort of jammed the plane on the build box by the rear stab post.
That broke off. Hastily reglued

Then I asked another flier if I could borrow their nice little yoke plate with pin that went through the rear peg.
That did work.

I wound on a few turns - 500 and let it go.
It stalled massively again and again.
I tried to adjust the tail incidence and where I'd hastily repaired it earlier, the tissue tube was now attached to it quite firmly

I did manage to move it. I had a few turns left and let it go.
A floundering level flight followed by a power dive.
NO real indication that there would be any sort of turn either.

Some work to do I think 

Task list:
1 - Repair the stab rear post and tube.
2 - build a yoke and pin stooge to allow me to wind it up without breaking stuff
3 - decide on a motor size
4 - have another go.

I'll update when I get the chance to get it in the air again.
On the positive side there were a number of LE's flying beautifully around the Wickham community centre last night.
That sight really inspires me to get mine in the air.


Happy flying
S

[piecost]

Sorry to hear of your troubles. I used some fin offset to get a right turn. Also, a bit of fiddling with the thrustline. I recommend that you consider a blast tube to protect the delicate structure during winding. My first wind at the nats burst the motor on low turns.

[piecost]

Experiments with stability and tail sizing on the thread:

Re: How do WS planes with "aft CG" fly at all???

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=23088.0

[piecost]

The new fuselage of the bis 4 version has the wing mounted 20mm further forward and 4 longerons back to the peg tapering to 3 longerons at the back. I was happy to find that I could cover it in Esaki without huge wrinkles and that the fin/tailplane post was still attached rigidly enough.

[piecost]

I was disappointed that the Legal Eagle competition had been removed from the Nationals this year since I have a brace of sub 3g models. So, I entered my original Bar Fly in the 2018 Osprey class. There
were 5 entries, three being the re-purposed Legal Eagles
l installed a plate between the top fuselage longerons in the bay ahead of the wing trailing edge, with a slot to take Blue Tac to take the weight up to 4g and allow CG adjustment. The undercarriage was removed and I used a 44 degree pitched propeller.

I made up a number of motors to the 1.5g limit with mass/lengths varying from 1.65g/m up to 2.0g/m.I estimated that I'd need a 1.8 g/m motor, but ended up using the lightest of the rubber that I stripped. I
over-estimated the thickness of rubber required since the model did not need to RoG and was less draggy without the undercarriage.

Details of my best flight
1.65g/m x 18 Loop x 1.5g
Wind to 170 turns
back off
3m02s

This flight used nearly all of the cruise part of the rubber characteristic so is considered near optimum. I rushed this event after I finished flying NoCal. It was clear that the two bespoke Osprey models were a minute ahead of me and it was not worth spending more time on the class. A gain would have been made by winding harder and backing off, but this would not have made the difference. I gained bronze.

It seems that this competitive Legal Eagle was good for about 3 minutes under the 28 ceiling whilst.proper Osprey models could achieve 4 minutes. Obvious explanations for the disparity was the diftference in wing area, lack of span or fuselage length limit, smaller fuselage cross section and lack of undercamiage. One aspect that I was mentioned that had not considered was that the film covering on the.Osprey is not porous, unlike the undoped tissue on the Legal Eagle.

The next development is to construct a torque meter so I can better control the maximum altitude.

[Mefot]

Wind to 170 turns

I suspect you had a few more turns than quoted !!!

Will you build a bespoke legal eagle or continue modifying the barfly ? 

[piecost]

Ah yes, i forgot. It was handle turns on a 10 to 1 winder. I don't think that I'll make a bespoke Osprey. I was delighted that my F1R model flew at all and may concentrate on that. 

[Skymon]

I have a dead Eagle...
The stooge came loose and the rest is history.
Moving on....

[Skymon]

The Eagle has landed!
Well, the Fly is hatching...

As a very small tribute to John Barker, I decided to make another of his Bar Fly Legal Eagles.
My last one got smashed up by an errant stooge during winding.
See above.

I got some very nice 1/16th contest quality wood from The Balsa Cabin (all below 5lb) recently and this was the final push I needed to make the new plane.

I had the stab, the prop and hub assembly and the wheel from my previous effort, so I had to build the rest.
I went with Johns stab as per plan, rather than my previous changed version with a single central rib.

Here's my progress across the weekend.
Happy with the mass so far - a little more covering to go.

Not happy with the tissue around the dihedral break.
I damped it to take out the slack and I don't like to stretched form that resulted.
I will probably recover this bay in a contrasting colour.

Skymon

[Skymon]

Build is complete.
Plane came out at 3.4g, so over 10% over weight, but finished.
Gide tests look nice and floaty.
Now to fly and trim.
I'll make sure my stooge is well secured this time.


Si

[OZPAF]

That looks nice SM. The covering is pretty good to my eyes but I do see the small crease at the dihedral break. have you tried the trick of running a small line of dope (diluted) along the crease. It should shrink that small patch of slack tissue.

John

[Skymon]

John
I made the mistake of shrinking that panel with water.
It's too tight for my eyes, but it ain't broke, so I am averting my eyes.
If I get it to fly well I might add a new contrasting panel in there.
But for now it's trimming time.

I struggled with the LE last time, hopefully it will all go OK this time.

Si

[OZPAF]

You need to imbibe a bit(nice bottle of wine there) till you forget what you were reflecting on
Happy trimming.

John

[piecost]

I am pleased to report that I won the Legal Eagle compettion at the North West BFMA indoor Gala
at the Manchester Velodrome on 16 March 2019. This is the first tirne that I have won in this class.

There were 5 entries with a wide spread of best flight times ranging from 1m28s to 3m30s. There was no limitation for the rubber motor and the models had to RoG as usual. The height of the net at 40'8" was not to be exceeded.. There was no limit to the number ot flights and the best single time won.

I had prepared a spacer (stint) to practice with shorter motors under a low celling but lost all my practice motors. I had previously recorded durations exceeding 2 minutes using a partial meter of 1.63gm of 8 inch length with a 67% spacer. So I ended up making various thickness motors of 24 inch length.

The Velodrome proved hotter than my typical practice sessions at 21 csoI selected a thinner motor
ot 1.54g/m. This was the first time that I had used a full motor in this model.

I used my Bar Fly bis 2 model fitted with a tailplane of 1 inch less span than shown on the plan. The model had proven to fly well with the smaller tail in sports centres and this saved some weight. After a couple of hand launched flights to get the tail setting correct i performed my first timed RoG competition flight. The. model stalled soon after take-off. I found that the air below about 5 was very turbulent, stirred up by the cyclists wizzing round the edge of the flying space. So, I swrapped back to the original sized tail which seemed to help. My second competition flight details are:

Bar Fy bis2 with 44 pitch propeller
Motor. June 2016 Super Sport 1.54g/m x 24" Loop, 1.88g
Wind to 2520 turns, 23g.cm
Zero back-off
RoG launch
3m30s (touched a light)

I had not backed-off as I considered the winding torque
too low to reach the celing and not worth further reducing. The model jumped into the air without the usual take off run and.climbed level with the top of the net. But, my luck was in and it hit the light, dived, recovered and stopped climbing. The collision stopped the model climbing too high and being disqualified. A steady decent without problems from turbulence resulted in a landing at 3m30s. This lucky flight had won the competition! I knew that it was a good performance but had no idea since we could not view.other competators scores.

The 2 place model only achieved 2m39s. I put this considerable lead down to the model being under 3g.

I only completed two further flights befoee concentrating on my LPP which was not going so well.

I reducedg the launch torque by 1gcm on my subsequent  flights but they both outclimbed the nets and were disqualified.  One went 10' above the neting and I was starting to worry in case it drifted over the cycle track Luckily, it hit a wire and spiralled into the floor. I was lucky not to break my somewhat delicate propeller. I wondered what was goingpil on and if i had forgotton to back off. A.modeller experienced in the venue mentioned that the conditions were not great and that an inversion layer.at the top of the nets.can sometimes suck the model up. Howevee, I did not see this behaviour on my mates F1M which was cruising consistantly at this height.

I had achicved a great fight in the first of the three rounds but was unable to reproduce my best flight or even any further times without being disqualified.

Examining the data for the flight against the rubber torque curve revealed that I had launched just at the top of the linear "cruise" range and landed above the drop off. The motor choice seemed optimal. I was very relieved that it exhibited no bunching when using a full motor.

[Skymon]

Another comprehensive report and a super result Tim.
Thanks for sharing your info.

Glad to see the Bar Fly flying.
As you can see above, I built another and I look forward to a duel at the Nats if not before.

I find enclosed motor planes a little tricky...

Regards
Si

[piecost]

My model flying at the start of the video of the April OFMAC session. It has slightly too nose up trim and stalls on the descent.

https://youtu.be/czfG5-vFG4Q

[Skymon]

That trim looks to be working well on the ascent though.
What is Ian flying at the end, looks like an A6...

Great video and good to see familiar faces flying.