Bristol F2B by Flair

[J D 8]

 I have in my possession a  Bristol Fighter from the Flair kit. It belongs to our club chairman who bought it as part of a large job lot some years ago. Most of the other aircraft have been sold on.  He says he would like to see it flying and recons I am the man to do so as it is my sort of thing.

       The model is well made but modified from original I think as it has fixed centre sections with the wing cells sliding on to carbon tubes. An ASP 80 is the power source which should be enough given the wing area and typical Flair section.

Points of concern. 

The old Futaba Challenger radio gear including TX to be swapped out for more modern gear.

The fuel tank is mounted back under the centre section decking with long pipes to the engine, not sure about this. Advice needed as not anything I have ever done.

 It is a pretty hefty build with the fuselage weighing in at over 9 lbs and near a couple of pounds for each wing cell and plenty of lead in the nose for balance [ my digital scale only goes to 10lb's] Nothing to do here except fit a larger engine if needed.

Anyone here had/have/flown one ?

[Dad_flyer]

It looks great. 

Edited June 13, 2021 by Dad_flyer
Spelling. There may be only three words, still room for me to make mistakes.

[Don Fry]

Servos, Futaba?,  good. I hear your fears re a backward mounted tank. If you reckon you will waft it about, OK.  
Now, I would get bored, I would have to see what you it does to provoke an engine stop, or even what it can do with the airframe, within structural reasons. Try it, a mistake high.

Always fancied one of these.

ps, I’m done with sort outs and ARTF. Virgin kit, hand bite.

[i12fly]

Had one but sold it before flying it as I changed my car and it was too big! Lots of people had difficulty with the CoG it needs to be well forward of the mark on the plan (or significantly 'pointing down'). Check out on the web, quite a few only flew once -because of CoG being too far back

[john stones 1 - Moderator]

Had it been flying on a pumped engine ?

Not be first time a kit/plan had a wrong C.G position given, having said that, can't see any reason it would be a pig if a adequately powered, or am I missing something ?

[J D 8]

     Thanks both, I will be checking C.G. It does have half the proverbial church roof in the cowling, something common to most WW1 types. I like to set biplane CG at a safe position of 1/3 chord of upper wing and go from there, ignoring the lower wing.  No problem getting into car with two piece wings but this mod has probably added a fair bit of weight.

   Engine is not pumped, just a standard ASP 80 4 stroke mounted upright.

[Jon H]

We always recommend laser 80's for these so your asp will be fine. As has already been pointed out, its hardly a high performance aircraft and you have plenty of wings. The only thing the weight might do with a small engine is limit climb performance and require a higher flying speed/nose up attitude when in the air. A big engine will fix the climb, but i wont fix the other issues if its porky. 

[J D 8]

Thanks for the reply Jon, What do you think of the tank issue with it being mounted far back under the decking between the cabane struts and long pipes to engine ?  

[Tony Packe]

I have one of these with a Laser 80 in it, exhaust exits downwards so no need for anything to show.  Bit a handful to fly actually, one the the club "experts" usually has to land it for me.  Needed a lot of rudder mix dialled in with aileron control as it just wallows in the turn with no general authority otherwise.  I will try and post a picture when I can find one.

[David Davis]

If it's of any relevance I have a Roy Scott BE2e of about the same size powered by an OS 70 FL. The CG on the plan is by the rear cabane strut. I have flown it in this configuration but my fingers were dancing on the transmitter! Someone with a superior knowledge of aerodynamics suggested that the CG should be at the mid point of the forward cockpit. I've had to add a substantial amount of lead to get it the CG to that position and now it's easier to fly.

 

I find that you have to keep the speed up on landing and the engine on otherwise you've no airspeed over the elevator and all control is lost. If you let the speed drop to much it will stall for a pastime. Don't ask!

 

With both this model and a Flair puppeteer I find that you have to use the rudder in the turns. I still use the rudder even though I have 50% mixed in with the ailerons on the Be2. 

[Jon H]

1 hour ago, J D 8 said:

Thanks for the reply Jon, What do you think of the tank issue with it being mounted far back under the decking between the cabane struts and long pipes to engine ?  

 

 

Given the non aerobatic nature of the model you will probably get away with it. I suggest you avoid full throttle steep climbs off takeoff though, at least until tested. I always use 75% throttle on maiden flight takeoff's anyway to give me a longer ground roll and reduce the chances of the engine going sick. 

 

As the other guys point out, rudder will be key on a model like this but i would not recommend mixing it. Its not uncommon for you to need ailerons and rudder in opposite directions and if they are mixed that will not work very well. You have 2 hands and 2 sticks so the mixing by hand is no hardship and a better way to go. 

 

My Flair Nieuport certainly requires a little porridge stirring on the sticks but its very rewarding to fly. 

[J D 8]

          Thanks all, I am not worrying about flying it so long as there is enough power. Have been flying my DB Major Mannock for many years and yes the primary steering control is the rudder, in fact it fly's well on just rudder elevator the barn door ailerons[ lower wing only ] are not very effective.

Bristol's weight is much the same as larger Mannock.

  It's tank is well buried in the structure but I could fit a new one in front as there is room if needed.

[Djay]

I have one I built many years ago and still fly. Powered by a Thunder Tiger 90 four stroke it is overpowered and flies around on less than half throttle all day.

So easy to fly and very stable. You do have to mix rudder in with the ailerons or use the rudder as the primary turn control, but this is normal for this type of machine.

Takes off and lands so easily and very controllable.

I balanced mine with quite a bit of nose down attitude and it flies fine.

Tank is under the front engine cowl just behind the engine, I use the rectangle SLEC tanks for convenience.

 

I did have the upper wing leading edge break one time as it is only soft round balsa, and one wing half decided to fold up in mid air one day, all I could do was cut the engine and wait patiently for the plane to slowly spiral down and collect the mainly intact plane to take home for repairs.

 

Darryl

 

[i12fly]

As it appears that the tank has been in place some time and no doubt with a bit of fuel in it, I wouldn't trust the plumbing inside the tank, flexible tube can soften and tubing oxidise, tank bung leaking, sludgy oil congealed etc. If you fit a new tank up front you know for sure you'll be ok. I once had an old fuel tank split, luckily always counted the number of turns on the manual fuel pump so noticed fairly quickly before filling too much of the tank compartment

[J D 8]

                Having had a look over the airframe I have found the top wing cabane struts to be loose in the fuzz, so will have to find a way in and sort it out. A wobbling cabane fore and aft would give a variable incidence top wing, not good.  Tank and radio are hidden in the same area so I recon tank is coming out. 

[Jon H]

2 hours ago, J D 8 said:

                Having had a look over the airframe I have found the top wing cabane struts to be loose in the fuzz, so will have to find a way in and sort it out. A wobbling cabane fore and aft would give a variable incidence top wing, not good.  Tank and radio are hidden in the same area so I recon tank is coming out. 

 

Sounds like you might as well gut it and start again. It might be a hassle but its likely to give you a much better shot at a reliable model

[J D 8]

             Yep, that's the plan.

[Ronaldo]

Don't know much about this apart from my own CG experience with other models, and agreeing with what others said about the CG being too far back, even if following the recommended location on the plan. One of our club members built one, it was gorgeous, he had spent a great deal of time detailing it. He had it on the recommended forwards CG location, but when it took off it was all over the place, no amount of years flying experience could tame it. It was tail heavy, nose up attitude, until it finally stalled and nosed into the ground. A sad ending to a lot of hard work. So I would go for a forwards nose heavy CG and take it from there. On a first flight it's far easier to hold the nose up with elevator with a chance of landing in one piece, than it is when pushing 'down' in to keep the tail up.

[Don Fry]

Sorry, but a rearward CG adds sensitivity to the elevator. 
You get a machine that goes from dive to stall at , to my unexpected fingers, no movement. Not nice. And landings to survive, is a rollercoaster. Been there.
 

old saying, forward CG, fly badly, rearward CG, fly once. 

[Jon H]

generally an aft c/g should not be a cause for a crash and it should be controllable even if its very unpleasant. The issue tends to come from excessive elevator rate combined with the aft c/g. Add to that the startle factor, stress of a maiden flight and the eyes of onlookers, its not an easy situation to recover. I notice that often maiden flight takeoff's are done the same as the pilot would do a normal takeoff and this often means its hauled into circuit quite early. This is not a good idea in my view and only adds to the workload. I always aim to takeoff (at slightly reduced power, 70-80% to keep the engine on my side) and then just fly dead straight for at least 10 seconds. Gentle rising climb, wings level, touching nothing but the gear retract switch if its a warbird to clean up the airframe. This gives me a small amount of experience with the model before i do a turn and if i feel its needing forward push on the stick during my climb then that is very valuable information to have as i can gently lean it into a turn. I had this very experience with my sea fury maiden as it pitched up sharply right after takeoff. I needed considerable forward pressure to keep the nose down and while this was ultimately the result of an incidence issue, the result was the same. My high rate was over sensitive so i went for low, held the nose forward and off we went. 

 

This is why i always set my elevator rates just above and just below the recommended minimum. If its tail heavy and a bit of a bucking bronco, hitting low rate can help quite a bit. I am also used to flying with my sticks off centre as most of my models are scale and so are impossible to trim 'hands off' at all times. More than anything i think this is a big help and when teaching i always give students the model out of trim and expect perfect circuits, takeoff and landing. Why? because when they start doing their own maiden flights it wont be in trim, so learning how to fly a model out of trim is a valuable skill. Also if its miles out, you might not want to take your fingers away to hit the trimmers. Without an assistant to do it for you, landing with it all the sticks sideways might be the only choice. 

 

To be honest though, watching videos online of 'tail heavy' models spinning and crashing, most are elevator travel related and have less to do with the c/g than people think. this is often made clear when the pilot just stops touching the stick and the model nips along nice and straight.  Its like with overheating engines. If an engine overheats and stops, it must be lean...more often, the cooling is rubbish and the tank in the wrong place. The knee jerk diagnosis of these things often sends people down the wrong path. 

Edited June 16, 2021 by Jon - Laser Engines

[Engine Doctor]

John's right about excessive elevator movement when combined with a reward CG. There  have been a number of younger flyers  who ive helped over the years  who have learnt to fly and moved on to  fun fly type models and with max control movement .They then turn up with a scale model and often  won't listen when you advise reducing movement of control surfaces.

The words that echo most at the crash site are " I did say............."

[J D 8]

  Found a way into the Bristol the other evening, a hatch hidden under the lower centre section. Some odd things inside, along with some Futaba 3003 servos there were some "spare" formers and a heap of foam packing filling all spaces forward of the cockpit, much more than seen in the pic. No idea where RX or battery would have been fitted. 

A rather large tank also removed

[J D 8]

   This pic shows the engine bay with tank in original position, thing is with all the foam packed in every where the only cooling exits were the two round holes in the cowl. [ scale on some Brisfit's ] The forward one gives access to the needle valve. I intend to fit a new tank just behind engine at the right level. Hot air will then be able to exit past it  through the old tank bay and out at the cockpit. [ I hope ]

[J D 8]

Elevator link. The elevator of the Bristol is operated by pull pull wires . Servo operates the cross shaft much like the stick does on the full size.  As can been be seen in the pic the connection is one of those clamp screws often found in trainers, easy to adjust but on of my least liked model fixings in that they rely on only friction to secure the connection.   Just as well I checked this one as it was only just holding. Will be replaced with metal clevis or bolt through ball link.

   One can usually recover a flight where an aileron or rudder becomes disconnected but loss of elevator hardly ever has a good outcome.

I got away with it once when in hand launching a DB Rooky Major, my sleeve somehow caught the elevator horn and it snapped. Lucky it was well trimmed and continued in a shallow climb the pod mounted DC Sabre [ no throttle ] running well.  In straight flight it would gently climb and a gentle turn would loose height and when fuel ran out settled into a steady glide for a good landing. 

[J D 8]

Bristol update, new fuel tank now in usual position, extra cross brace rod's to stiffen cabane, elevator link now sorted and radio in place.

  Been working on the UC which was a solid job with no give or shock absorbing except for the tyres. With an aircraft of some 14lb I like to have some suspension.

  My soldering has never been that good, a bit hit and miss but having had some good info from Martin McIntosh has improved. 

However this time I decided to weld it up, after all as Daddy Pig would say  " I a bit of an expert at welding."

 Set up for bungy cord suspension much like full size.  Wheels are now on tube stub axle's [ I hate the look of wheel collets ] held on with cotter pins.