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Author Topic: Bar Fly Legal Eagle  (Read 8390 times)
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Skymon
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« Reply #25 on: January 23, 2018, 07:41:28 AM »

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
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piecost
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« Reply #26 on: January 23, 2018, 08:45:43 AM »

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.
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Skymon
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« Reply #27 on: January 23, 2018, 09:47:11 AM »

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 Smiley

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

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piecost
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« Reply #28 on: January 23, 2018, 01:13:37 PM »

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
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Skymon
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« Reply #29 on: January 24, 2018, 06:24:13 AM »

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


Regards
S
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piecost
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« Reply #30 on: January 24, 2018, 06:32:48 AM »

Yes
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Skymon
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« Reply #31 on: March 07, 2018, 03:54:05 AM »

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 Sad

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  Smiley

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

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piecost
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« Reply #32 on: March 07, 2018, 09:25:14 AM »

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.
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piecost
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« Reply #33 on: March 28, 2018, 04:12:08 PM »

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
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piecost
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« Reply #34 on: March 28, 2018, 04:19:25 PM »

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.
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piecost
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« Reply #35 on: September 24, 2018, 01:37:07 PM »

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.
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Mefot
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« Reply #36 on: September 24, 2018, 01:50:06 PM »


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 ?  Smiley
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piecost
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« Reply #37 on: September 24, 2018, 03:10:10 PM »

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. 
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Skymon
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« Reply #38 on: October 03, 2018, 11:04:30 AM »

I have a dead Eagle...
The stooge came loose and the rest is history.
Moving on....
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Skymon
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« Reply #39 on: February 19, 2019, 04:04:21 AM »

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
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Skymon
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« Reply #40 on: February 20, 2019, 04:07:12 AM »

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
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OZPAF
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« Reply #41 on: February 20, 2019, 05:12:25 AM »

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
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Skymon
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« Reply #42 on: February 20, 2019, 08:23:34 AM »

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
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« Reply #43 on: February 20, 2019, 11:22:35 PM »

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

John
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