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Indoor Free Flight Forum => Legal Eagle => Topic started by: piecost on April 28, 2014, 07:54:49 PM

Title: Bar Fly Legal Eagle
Post by: piecost on April 28, 2014, 07:54:49 PM
I intend to enter the UK BMFA Nationals with a Legal Eagle model and selected John Barker's Bar Fly to build.

I read from the HPA forum that 5lb/ft3 balsa was recommended for this model but wanted to experiment with lighter wood. I obtained some excellent balsa from Nick Aikin “Greenman Balsa”; requesting as light as possible for the wheel and some 4.5 lb/ft3 for the structure. I cut the wheel from 4.1 lb/ft3 and the wing and tail ribs. The fuselage structure was cut from 4.5 lb/ft3, I stripped some 4.1 lb/ft3 wood for this but it felt far too fragile and flexible. Wing spars were made from my best model shop wood of 6lb/ft3 balsa with Stiffness Coefficient of 100. The lighter wood felt far too flimsy. The tail spars may have been made from the same stuff as the fuselage.

I slightly regretted the very light wood employed for the fuselage longerons when I broke one of them in the nose during initial flights. Glue was added to the break and extra vertical and horizontal members were added.

I used thinned Ambroid throughout the construction.

I incorrectly positioned the dihedral breaks on one wing – one bay too far outboard - and decided to make the other to match rather than start again. So; only the outboard bay has dihedral, the wingtip raised the same amount as the plan. The starboard wing had 1/8” washin added as recommended elsewhere on this forum. The model flys well with this change.

The windscreen was made from the plastic wrapping round a box of chocolates attached with a thin strip of double sided tape. The tape being rather heavy. Canopy glue would have been better.

I may a few changes from the plan to suit my building style. In particular, I left out the wing and tail tip gussets/braces to save weight.

I added camber to the wing and tail tips for aesthetic reasons; negating the practical design of using wing ribs turned on their side. I sanded a sheet of ¼” to the rib camber and pinned the strips (wetted in boiling water) between camber templates and put in a hot oven.

The fin trailing edge was attached to the right side of the fuselage tail-post to give some right turn

The tissue for the fuselage was water-shrunk once on a frame with an airbrush, attached with thinned aliphatic glue and shrunk a second time with rubbing alcohol. The tissue for the flying surfaces was water-shrunk twice on a frame and attached with Spraymount. The covering on the leading edges of the flying surfaces was wrapped round the front and glued with thinned Ambroid. Some of the other edges were starting to peal off.

I don't like Spraymount for this application since it is difficult to apply enough to stop the tissue lifting without adding allot of weight.

The propeller blades were not sanded to section since I was getting short of time. The propeller was formed with their axis at 15º from vertical on a can of Spraymount (not put in an oven!).

3/32” square bass was used for the propeller spar, tapered and inset into the blades. I had not tried this before and it proved very neat. A strip of tissue was glued over the joints. A reverse Z-hook was bent into 1/32” wire. I found that the trailing edge of the blades clashed with the nose block so had to be cut away. I used a nylon bush to hold the propeller, not being able to find any thin tin plate. The nose block to hold this from soft balsa. I was worried about the nylon bush pulling through so glue 2 layers of the thin wood from cigar tubes cross grained onto the face of the block.

The tailplane was built as per plan except that the single central tailplane rib was used rather than two matching the fuselage taper. The tip braces/gussets were ommitted.

The upper surface of the leading edges of the flying surfaces were sanded to a radius.

Weights were as follows:

                              Uncovered     covered
Fuselage                    0.61g           1.26g
Wing                           0.27g           0.68g
Tailplane                    0.15g           0.20g
Fin                              0.10g           0.20g
Undercarrage             0.13g              ---           
Propeller                    0.65g             ---           
Propeller Block           0.12g             --- 
Peg                             0.11g

Rubber                  0.082” Tan Super-Sport 0.89g
Stint                       1.13g

AUW                      5.65g

Airframe without Rubber 3.45g

My model has CG 8mm forward compared to plan (with rubber)


The model flew straight off the board and the adjustable tail incidence proved very convenient. The tailplane was set to give a nose-up climb. I added some more fin offset, moving the leading edge about 1mm to the right and 1/64” right thrust added to tighten the turn. I plan to enter this model in the nationals in June and generally fly in 24’/25’ ceilings so use a stint to trim with a shorter motor.

I started with 0.092” rubber, with a 60% stint, equivalent to 200% propeller to peg length. The model proved overpowered and 0.082” was substituted.

I was slightly concerned about the RoG ability of myself and the model. The model quickly established a nose low attitude on it’s wheel and took about 1/3 of a turn before lifting off into a steep climb. From a hand launch the model flys at low incidence for a second or two before settling into a nose high climb.

More trimming awaits...

Title: Re: Bar Fly Legal Eagle
Post by: piecost on April 28, 2014, 07:56:27 PM
Completed model

Title: Re: Bar Fly Legal Eagle
Post by: jhnwdwrd on November 23, 2014, 10:07:23 AM
Good looking plane. Where can one find plans for the "Bar Fly"

Title: Re: Bar Fly Legal Eagle
Post by: Indoorflyer on November 23, 2014, 11:34:23 AM
John Barker, aka "Hepcat" on this forum, designed the Bar Fly.  There is a .jpg of the plan in this thread:


Title: Re: Bar Fly Legal Eagle
Post by: jhnwdwrd on November 23, 2014, 12:12:30 PM
Thanks for the link.

Title: Re: Bar Fly Legal Eagle
Post by: Indoorflyer on November 23, 2014, 01:09:20 PM
Plan on one sheet, (.jpg again) here:


Title: Re: Bar Fly Legal Eagle
Post by: piecost on October 14, 2016, 09:58:23 AM
Bar Fly

I had only put in the occasional flight in with this model over that last few years and had not really tapped into its full potential. I entered it into the the 2016 nats, but not too seriously. I had not even build a spare mode (I have a habbit of hanging models in the roof). I had been very confident in my first nats (in 2014) the model was the lightest in its class. But my first flight landed the model on the centre boss of the roof structure! It only being retrieved at the end of the competition.

I had found that the best times were achieved with a 26.5" motor length. This had a potential duration of over 4 minutes, but was limited by the motor bunching at the rear hook and landing out of turns. The narrow rear fuselage being more akin to a Peanut scale model than to an indoor duration type. I started using a lightweight bobbin, akin to a Wobbly Peg,  made from  a drinking straw and with depron disks. Unfortunately, this tended to break rather than offering an improvement. So, I had to remove it.

For the competition; I had prepared a number of identical motors , but not did break them in. The idea being to perform lower powered trimming flights in quick succession and resting each for an hour before the competition flights.

I intended to spend the last day of the competition with this model. My first wind was a disaster when a new motor broke in the model. I was trying to break the motor in; not break the motor up!  It had gone at the knot, which was positioned under the wing to avoid bunching at the rear peg. But it left a mass of rubber at the rear peg just waiting to burst into flayling strands to mash the mashmellow-like 1/16th square balsa structure. So, I constructed an external blast tube of 2mm depron taped around the rear fuse. The idea being that this external splint would prevent the structure moving outwards and breaking when hit by the rubber. This worked and I extracted the motor without any further damage. The only repair being an unpright at the wing trailing edge. My third burst motor in this model! I had clearly used up all my luck.

With the model back together, I was going to progressively increasing my times and I was confident of eventually reaching the 4 minute mark.  A first competition time was 3m15s, only reaching 45'  (about 10' below the girders).  This was a solid start to build on, but then I noticed the nice yellow Cassutt Nocal flying which caused me to rush a final conservative Legal Eagle flight of 3m18s before breaking out my NoCal. This was good enough to put me in third place.

If I get round to building a new model I will consider the following changes:
   Widen the nose (to the same width as at rear peg) to fit a blast tube
   Spacer between leading edge of tailplane and bottom of fuselage to allow more nose up trim.
   Single attachment on leading edge of tail to save weight (to pay for the wieght of the previous change)
   lighter tissue
   more refined noseblock (had to trim propeller trailing edge to miss corners of noseblock!)
   Higher propeller pitch to use shorter/fatter motor to alleviate bunching
   3D printed bobbin/wobbly peg
   Extra upright/lateral spacers in first bay of nose to prevent buckling of longerons

I may try to beat 4 minutes in the next session. I will report here if I do

Title: Re: Bar Fly Legal Eagle
Post by: piecost on July 26, 2017, 03:52:14 PM
for HPA

I really like the Bar Fly design but was disappointed in that I had not wrung out its full potential. I decided to build another Bar Fly incorporating some improvements. These were mainly to save weight relative to my first model (which was already pretty light). The major change was the ability to accommodate a blast-tube. This entailed widening and deepening the nose to the same dimensions as at the rear peg.  The fuselage cross section at the peg was considered the minimum fuselage width around the motor as badly bunched motors had contacted the structure. I made a blast tube from 2 telescoping sections of a Selfie Stick that matched the fuselage cross section at the rear hook, 15mm diameter. The front fuselage was widened and deepened to accommodate it and the canopy almost disappeared, to be only 2mm deep.

I carefully examined the structure with an aim to removing redundant parts, to remove weight. The fuselage cross-member at the base of the windscreen was deleted it was so close to the member at the top of the canopy.  The  base of the Ultra-film windscreen  was joined to the tissue  on the top of the nose with canopy glue. I also removed the diagonals at the edges of the canopy and got away with folding the film onto the side of the fuselage before gluing. Not a neat solution, but very light. The root rib was removed from the fin, the tissue being kept taught by the  careful  spacing of the leading and trailing edges onto the  fuselage. The rear fuselage was tapered to 1/8 inch high and 1/6 inch wide saving structure and tissue weight. This created a potential weak point in that the trailing edge of the fin had a small gluing area onto the back of the fuselage. This has not proved to be a problem. The trailing edge of the fin was glued to the right side of the fuselage, with the leading edge central, to give a right turn. It was extended below the fuselage and rounded to form a post for mounting the tailplane trailing edge tube. This replaces the separate peg attached to the tailplane on the first model. The fuselage structure was built from 4.2 lb/ft3 balsa with Stiffness Coefficient of only 85. This felt very delicate, but was significantly better after covering. It withstands the load from the rubber, even with fairly slack tissue. Most care is needed in handling and not taking out cross members  when fitting the blast tube.

The model was covered with Gampi tissue, attached onto the flying surfaces with 3M77 sprayglue, with the edges  stuck down with thinned Ambroid. The tissue was attached to the fuselage with thinned PVA. The fusleage tissue was pre-shrunk with water and then re-shrunk with rubbing alochol when in place. It was held in a jig to prevent warps. The fuselage tissue was still slack after covering. Perhaps a second water shrinkage should be applied. The tissue for the flying surfaces was preshrunk with water twice and left to dry (not on a frame). It was ironed to get the worst of the wrinkles out. This did not work well and the flying surfaces had a bumpy texture. The ironing was done some hours prior to covering so that the tissue would be at ambient water absorption and not further slacken after covering. Tissue sagging often occurs in cold and damp hangers and must degrade the flying surfaces and increase the camber. I didn’t demonstrate any weight saving in employing Gampi tissue over Esaki, even though it should be 15% lighter IIRC. It seems that weight glue used to attach the tissue is more important than the difference in tissue weights.

The ribs were cut from my lightest balsa of 3.59 lb/ft3. This sheet was also used for the nose sheeting and that holding the motor peg (the hole was hardened with cyano). The peg was 1.5mm OD aluminium tube; a smaller diameter tube/rod would possible tear through the balsa.

On my first model 22% of the airframe weight of the first model was taken-up by the propeller and noseblock and it was clearly over-engineered at 0.77g. I had employed a relatively heavy nylon nose bush which, even worse, necessitated weighty 1/32 piano wire. So, on the new propeller I switched to using 0.022" piano wire (as per my LPP model) and 0.010" steel shim bearings in place of the nylon bush. This is the first time I have tried this, but they seem to work OK without incurring any slop. The fat nose necessitated a large nose block which would be far too heavy if made from sheet and so a space-frame construction was used rather than  a solid lamination. I did use a sheet for the baseplate, but cut lightening holes. It was tissue covered.

I used a 1/16 bass propeller spar 0.063” round at the centre tapered to 0.020" and blades from 0.8mm A-grain balsa. They were PVA glued to the spars without being let into slots in the blades (I found that the slots tended to split the blades) The blades were made from 0.8mm A-grain sanded to 0.022" and proved too delicate; the blades broke off when the model hit a wall. I replaced the broken propellers with a 0.100" diameter bass spar tapering down to 0.022" and 0.8mm thick blades weighing about 0.100g each. They have withstood wall/floor impacts and are now just strong enough. I managed to sneak in an extra 3mm on propeller radius and used a 44º pitch at 75%. The plan had plenty of room for a longer blade radius, but was limited to an additional 3mm on the undercarriage length without encroaching to the 3mm margin around the wing on the plan.

The lighter propeller moved the CG aft, this was compensated by the larger tail area. with no loss of stability noticed. I managed to add 32mm to the span of the tailplane; 16mm added to each trailing edge with the leading edge and trailing edges projected outwards.  A single, central, leading edge attachment hook was used, wedges being added to the tailplane leading edge to prevent it sliding sideways.

The 1 inch diameter balsa disk was replaced by a light 1/16 stick bent around a hair curler into a  circle. A cross bar was added and glued to the wire. The first wheel I built does not rotate, subsequent wheels do at no real weight disadvantage. The gear leg is removable and on the original model about 10mm sticks into a box in the fuselage. On the latest model I reduced the length of the piano wire slotting into the fuselage to about 4mm and correspondingly reduced the height of the box in the fuselage. This proved too wobbly, the model barely stands on its gear, so perhaps 6mm of wire sticking into the fuselage would be better:

I was so pleased with the second model that I build a third. This proved slightly heavier as I had used up my lightest balsa. Weights came out as follows:
                                                  Bar Fly bis 2                      Bar Fly bis 3
                                          uncovered   covered        uncovered   covered
Fuselage                                 0.492            1.123            0.503      1.249
Undercarrage                       0.087               0.087            0.090      0.090
Propeller                              0.325               0.451             0.431
Nose block                            0.105              0.140            0.108       0.148
Fin                                        ?                    0.065             0.023       0.077     
Tailplane                              0.14                0.315             0.119       0.338
Wing                                    0.22                0.623            0.281        0.734
Peg                                      0.11               0.110            0.094         0.094
Total                                                          2.914                             3.161

I test flew the model under a 25' ceiling with a 1/3d motor and a 2/3 spacer  to match my high ceiling site. 

Apart from propeller breakages and the wobbly undercarriage; I was delighted with the model. It trimmed without any tedious thrust line adjustments, only the tailplane setting being changed.

The model needed a thinner motor than the previous plane (1.63g/m compared to 2.00g/m) of the same 8” length.

I flew the models in the high temperature of 24ºC during July. I recorded the following flights under a 25’ ceiling:

17 Jan 2014 Super Sport
1.59g/m by 0.65g (8” loop) 1/3 motor with 2/3 spacer
Wind to 930 & back-off 20
1m58s no touch
80 landing turns

June 2016 Super Sport
1.63g/m by 0.67g (8” loop) 1/3 motor with 2/3 spacer
Wind to 940 & back-off 35
2m02s no touch
30 landing turns

I also got the identical times from winding to 95 & backing off 45 and winding to 96 & backing off 55. There being no advantage to winding more and backing off to the same launch turns. But, from plotting the winds onto a curve of torque versus turns I notice that I am only employing the linear part of the rubber torque curve. Winding up the non linear part of the torque curve and backing off may yield improvements. Since I am not pushing the motor hard; perhaps a reduction in g/m could yield an increase in duration.

From comparison from a previous session at 17ºC where my best duration was 1m55s; it seems that the 7ºC increase in temperature was worth 3% duration and the switch to Jun 16 rubber worth another 3%.

It irked me that I had not achieved 4 minutes with the original model under a high ceiling and I am delighted that this new model looks like it would comfortably top 5 minutes on a full motor. I am supprised that it has achieved a 53% improvement in duration for a 12% reduction in airframe weight! This is astonishing considering that the propeller is the same and there are no other significant differences other than the increase in tail area.

Title: Re: Bar Fly Legal Eagle
Post by: piecost on July 26, 2017, 03:57:52 PM
This post includes a graph of the June 2016 rubber (on-dimensional) torque versus turns with the turns for my best flight superemposed. I was supprised that I was not employing anywhere near the full energy potential of the motor. However, it gave a very gradual climb and descent and good duration. The descent started at 60% of the flight time, whereas my other models with non-flairing propellers top out after 25% of the duration. Maybe I am on to something here...

Title: Re: Bar Fly Legal Eagle
Post by: Hepcat on July 27, 2017, 01:53:38 PM
(sometime I hope I shall understand that sobriquet .  Being born in Grantham I know that Lincolnshire pork pies are luxuries beyond price but apart from that . . . ?)

I have followed your rapid rise to success in Indoor flying and am tickled pink that the ‘Bar Fly’ has played a part in it. Your success is well deserved. You note and record, think of improvements and then, unlike so many of us, you actually carry out the improvements. I think you found the faults in ‘Bar Fly’ before I did. The propeller blade, if shaped as the plan, did hit the noseblock, the cross section of the fuselage at the front hook and rear peg was far too small, a bit more room to put negative on the tail would have been better.

As well as saying the above I want to ask you if you have any thoughts about the new ‘Osprey’ class.  Some of this has already been mentioned on HPA, indoor free flight, Legal Eagle, Penthouse Lady.  Very briefly, I said the ‘Legal Eagle’ rules in the BMFA Indoor rule book were not suitable for our purpose and should be replaced with rules for a Duration model with a fuselage that was suitable for the small halls where we almost always have to fly.  Bob Bailey and I talked quite a lot about this some months ago and we thought the following rules were a start. Total surface area of wing and tail 60 sq in, minimum airframe weight 4 g. maximum rubber weight 1.5 g. Minimum area of maximum fuselage cross section 1.5 sq.in. Motor must be completely enclosed (this will require some rewording about access) .  Existing ‘Legal Eagle’ models eligible to fly for a period as long as the minimum airframe and maximum rubber weights were met.
I understand at the last Indoor Tech Committee meeting there were questions about limiting fuselage length, propeller diameter, wing span, materials and so on. My hopes are for as little restriction as possible; balsa, carbon, foam ,pushers, canards, tailless all permissible in the quest for high performance in a small hall.  Are you in touch with any ITC members because it would it would be good to get something settled before the Indoor season gets started next month.


Title: Re: Bar Fly Legal Eagle
Post by: piecost on July 31, 2017, 05:51:38 PM
Hi John, I tried sending you a PM. Let me know if you cannot see it and I'll resend


Title: Re: Bar Fly Legal Eagle
Post by: Skymon on August 14, 2017, 05:02:21 AM
One of the cool factors of the legal eagle class was the whole plan on a single piece of paper thing.
If there's a move to a class suitable to UK small halls perhaps it could be based on a sheet of A3?
Best regards

Title: Re: Bar Fly Legal Eagle
Post by: piecost on August 20, 2017, 09:36:06 PM

I consider the legal Eagle to be very suitable for small sports halls, apart from the tendancy for the undercarrage to get caught in the netting that often hangs in these buildings. A removable undercarrage helps as it can detach when the model is tapped and allow the model to release. Care is needed with all duration models to avoid the ceiling.

I enjoy the take off requirement as it offers unique (to indoor duration) trimming challenges. I use a partial motor with a spacer as an aid for practicing under low ceilings in preparation for competitions under a higher ceiling. There is nothing stopping you using a full motor in a small sports hall. The model can easily turn in tight enough circles for a small venue.  There are many plans to build, but is needed with printing or copying to get the correct scale.

Hepcat is proposing a new class, which will have a minimum weight and will allow more design freedom; see the "Penthouse Lady" topic in the Legal Eagle thread. It removes the take-off requirement and the minimum weight removes the advantage of very light and delicate balsa and special tissue. Foam models might proove competative. I you enjoy designing you own models then this is a good time to create the definative model, as the class is brand new.

Have you recieved an email with the nationals entry form? If not, and you are interested then email Tony from the Indoordurationgb.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 18, 2018, 05:57:27 AM
I've been building a Bar Fly too...
I started with a plank of indoor weight 1/16th balsa from the Balsa cabin.
I ordered four and chose the mid range one, they were all between 4.5 and 5lb per cubic foot in density.
I held the plank up to the light and marked the grain, then trimmed along the edge to that angle, then stripped some strips!
I marked some very light areas for making the small 'plank' sections around the nose and some dark areas for the rear peg sections.

Building begins.
The use of 1/16th everywhere really helps. Just mark and chop.
Pre-glue then glue up.
I love the use of ribs for the wing tips, really cool.

Anyhow, I slapped everything together in my usual fashion.
I made a load of mistakes and I learnt a great deal.
I intend to build one of Dons Papagenos next and I'll apply all I learnt to that craft.

I'll post some pics and detail where I hit issues and what I did, or didn't do to fix them...


Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 18, 2018, 06:32:22 AM
The plan is nicely drawn and builds up easily.
I changed a few points just because I wanted to make my first 'cabin' build a bit easier.
I changed the very back end to use straight lines and to bring the very end to a point.
This would allow a little more room around the rear peg and a little more up elevator if needed.

My main problems were around the fuselage.

I built one side, then removed it form the plan and built the other....
Big mistake. I should of added some clingfilm and built one above the other.
All down the fuselage the uprights were misaligned, it's so easy to be 0.5mm out when building over a plan.
The thickness of the line can affect the position. When you get a few differences along the fuse it can all end up a bit scruffy.

So lesson learnt - built both sides, one above the other...

I also failed during fuselage construction. I just pinched the tail and glued it.
Of course one side was a tiny bit stronger than the other, so the bend was uneven.
It also twisted slightly along the length.
OK, I could of pulled it to pieces and started again, but I'm learning as I go and I can always build another :)

So lesson 2 learnt - pin the fuse down and use jig to align it as it's glued up.
Check alignment as you go and be patient... (tough job for me)

I had issues covering... Tissue is very different to mylar. I didn't pre-shrink first for the fuse. I do for the flying surfaces. I used a steam iron and just ironed it flat. It shrank a lot. Then I turned off the steam and flattened it out a bit. I really like the eggshell type surface finish.
Cutting tissue is hard - no nice clean hot iron, got to cut it.
It's surprisingly tough. Means the blade sometimes cut the wood too.

I built the wing flat and covered flat. Then used scarf joints to drop the dihedral.
I then used a mask (piece of card with a hole in it) to spray just the single section that had sagged when the tips were dropped.
This seemed to work quite well and despite being 'preshrunk' the tissue shrank a little more. tightening up my sag.

Lesson 3 - think about dihedral a bit earlier in the construction phase...

Handling lightweight 1/16th balsa in a 3D frame needs care, I snapped a longeron on the vary rear of the plane just by piking it up to roughly. I added a small sheet in between the top longerons for the last 20mm, it looks ok :)

I used some Polymicro for the window, held on with diluted UHU.
Wheel was a 1/16th balsa disc.

The prop is next but I've not go the photos today...


Title: Re: Bar Fly Legal Eagle
Post by: piecost on January 18, 2018, 06:33:17 AM

The model looks good and the covering is excellent. Did you shrink the tissue on the fuselage? The tissue on the wings looks really neat as well. Was that pre shrunk? Would you mind posting the weights? I look forward to a flight report.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 18, 2018, 07:34:19 AM
The tissue on the fuse is not pre-shrunk.
I didn't realise it was a good idea.
I did it on the flying surfaces and it looks a lot better and hopefully it will be less affected by humidity.

This is my first indoor tissue model...

I'm learning a lot :)

All up weight without prop was 2.7g

The prop is jigged up and setting. I feel it's a bit chunky.
I will probably have a go at another one.


Title: Re: Bar Fly Legal Eagle
Post by: piecost on January 18, 2018, 07:58:11 AM
That is a good weight. It is worth the effort developing the prop as this is perhaps the easiest component to save weight. They also get damaged easily so a chunky prop is a good idea as a spare.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 22, 2018, 05:42:22 AM
I found building up a nose for this plane tricky. Bearing in mind I started my indoor career in June last year, I don't have a great deal of experience :(
I made up the nose bit as per the plan and drilled a little hole through it. The prop shaft was pretty wobbly, but I wasn't too concerned and ploughed on.
The front end needed to provide a bearing surface and I needed to prevent the prop shaft crushing and binding.
So I grabbed a pop can and made a disc from the thick end and a wrap for the prop spar from the thin side.
I drilled a hole in the disc and used a pin to line it up to the nose block and cyano'd it in place.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 22, 2018, 08:22:27 AM
I cut the thin stuff in a rectangle, bent it up and stuck that to the prop spar, again with cyano.
Drilled a tiny hole in it for the prop shaft and added a couple of little ptfe washers I punch out of sheet.
Bent up the prop shaft and it's all finished...

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 22, 2018, 08:23:28 AM
the complete article.
I should weigh it...

Title: Re: Bar Fly Legal Eagle
Post by: piecost on January 22, 2018, 08:29:58 AM
Looking good. Did you find that the prop blades clashed with the noseblock?

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 22, 2018, 08:56:53 AM
No, it was OK, although I didn't follow the plan exactly...
I made the prop slightly larger in diameter by placing the blades a little further down the spar.
I had read your clash comments and adjusted.
I also used a smaller spar, 1/8th seemed pretty excessive.
I used 2mm balsa and thinned that a lot towards the tips.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 23, 2018, 05:19:39 AM
Total weight of the finished item with no rubber was 3.05g
Hoping to fly it one day

Title: Re: Bar Fly Legal Eagle
Post by: Hepcat on January 23, 2018, 07:32:26 AM
Your workmanship is exceptional and I have never seen better tissue covering on an Indoor model of this type.  It is interesting that your nose block looks the same as mine but I have changed from using a disk of tinplate to a disk of 1/32nd. ply front and back. (Wood is a good bearing material for light loads).  If Piecost says your weights are good then they are good.  I know of no one more meticulous in bringing a 'run of the mill' model up to top competition standard than he.
I wish you good luck with the flying. A small point concerning that; most people fly in left hand circles indoors. I have never understood why so I fly against torque the same as I do outside and that is how I fly the 'Bar Fly'.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 23, 2018, 07:41:28 AM
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

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon 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 :)

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

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on January 24, 2018, 06:24:13 AM
Was your 8" loop a 1/3rd motor??
SO a full one would be 24"?


Title: Re: Bar Fly Legal Eagle
Post by: piecost on January 24, 2018, 06:32:48 AM

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on March 07, 2018, 03:54:05 AM
So... I had a go with the bar fly...
Not a great success.

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

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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.

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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???


Title: Re: Bar Fly Legal Eagle
Post by: piecost 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.

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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

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.

Title: Re: Bar Fly Legal Eagle
Post by: Mefot 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 ?  :)

Title: Re: Bar Fly Legal Eagle
Post by: piecost 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. 

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on October 03, 2018, 11:04:30 AM
I have a dead Eagle...
The stooge came loose and the rest is history.
Moving on....

Title: Re: Bar Fly Legal Eagle
Post by: Skymon 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.


Title: Re: Bar Fly Legal Eagle
Post by: Skymon 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.


Title: Re: Bar Fly Legal Eagle
Post by: OZPAF 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.


Title: Re: Bar Fly Legal Eagle
Post by: Skymon on February 20, 2019, 08:23:34 AM
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.


Title: Re: Bar Fly Legal Eagle
Post by: OZPAF 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 :)
Happy trimming.


Title: Re: Bar Fly Legal Eagle
Post by: piecost on March 20, 2019, 05:18:32 PM
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.

Title: Re: Bar Fly Legal Eagle
Post by: Skymon on March 21, 2019, 04:06:21 AM
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...


Title: Re: Bar Fly Legal Eagle
Post by: piecost on May 07, 2022, 02:18:40 PM
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.


Title: Re: Bar Fly Legal Eagle
Post by: Skymon on May 09, 2022, 05:45:53 AM
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.