Flair Cub Kit.

[Stevo]

You will have NO trouble with a Saito 56 - I had one in mine, it was built quite heavy, and loops and rolls were no problem at all. It pulled it round the sky like it was on rails!!!

Good luck,

Steve

[Richard V-D]

Thanks Steve.

Richard

[Colin Anderson]

Simon, can we see the rest of the build? Please.

The Flair Piper Cub will be my first build in over 30 years and my first R/C model. I've enjoyed your posts so far and your excellent photo's - you are obviously one fine builder! I've learnt a lot already. I've gleaned many good tips from your post so far, but I'd love to see the radio and servo installation - particularly the wing servos.

[Ernie]

Hi Colin, Theres a great book about cubs in WW2 called 'fighting grashoppers' well worth a look if your'e thinking about a wee bit of detail; Also, mine did float on and on when landing. What about flaps inboard of the ailerons?

ernie

[Stevo]

Here was my wing servo installation...

And this is how the Saito 56 went in - Inverted!!!

Hope this helps... Let me know if you need more

Steve

[Colin Anderson]

Thanks Ernie,

Me thinks that inboard flaps might be a tad ambitious for my first R/C model! I've never flown R/C before and I've just passed 60! As the ailerons are pretty much full length on this kit it would also mean shortening them.

Steve,

Thanks for images of the wing servo fitting; excellent imaging, it'll be really useful. I'm interested in all aspects of the build and fitting (for the above Stated reasons), so any images you might have and are willing to post I'd be most grateful.

I've made a few minor mods to mine so far:

Parts 2a that join the fusalarge halves together were missing from the laser cutting so I cut my own. It wasn't obvious whether or not they should be placed across the join or spliced in, so I spliced them. Subsequently I decided this might still be a weak point so I added some lite ply joiners over the top - belt and braces!

I didn't like the plastic nose so I carved my own and hollowed it out, but have not yet fitted it

I've added Flair's steerable tail wheel.

Substituted the Myler strip for proper hinges.

Fitted the undercarriage fairings between the two wires rather than on top as I think it's neater. For added strength I laced them at 6 points as well as apoxy.

I'll be adding two servos to the wing, as well as the fusalarge/underwing supports.

[Colin Anderson]

By the way, Steve, that's one nice engine! Wish I could afford one! I'm fitting an Ervine 40 glow.

[Stevo]

Yes a great saito 56 that was and still is.. enjoy these...

And, on the maiden...

[Stevo]

PM me your email address and I'll send all I have for you.

Steve

[Richard V-D]

That's a crying shame Stevo. Looked a lovely model. What caused the accident? Was it something on the kit that broke?

I've just re-started my Flair Cub after it has lain dormant all summer. I've got a Saito 56 as well, but vertically mounted. Lovely motor.

Are you re-building yours?

Richard

[Ernie]

Hi Colin, no doubt your right about the ailerons. It's a great trainer; Mine eventually broke around the cabin (after me learning to fly on it) I built another, and strengthened the cabon with a plethora of liteply gussets. It ended up as a float plane. Unfortunately the glue was not totally waterproof, and gradually it became the worlds first anhedral cub.

ernie

[Colin Anderson]

Ah, so your the one behind the first anhedral Cub! An idea that never quite took off? I remember that post; thanks Ernie

[Colin Anderson]

Spent a fruitless afternoon trying to cut hinge slots for the elevators and rudder. I managed to cut all the slots in the tailplane and the rudder post without too much difficulty; cutting the slots into the rudder also went ok - although the rudder moves far easier in one direction than the other. Cutting the hinges for the elevators also went well - the problems occurred when I attempted to fit the toque rod. I just couldn't seem to get the holes right for the toque rod go into and finally ended up splitting the wood! These holes are awfully close to the ends. I tried cutting the damaged area out and splicing in new wood, but this was not too successful; I managed the holes, but when I assembled the elevators (a real fiddle, trying to line up the three hinges and the toque rod) they didn't line up! Damn! Obviously one of the holes was off line! Eventually I got it all together and lined up, but I'm not that happy with it, as I think it might be weak. As I had some spare wood of the right size I've made two new elevators. Tomorrow I'll have another try.

And I thought that using a hinge slotting tool would make things so much easier! Probably it does, in the right hands!

[Stevo]

Colin!

When inlaying the torque rods, use a gouge.... I'll explain. One of the most useful tools my father made was a gouge. The difference was that it was made from an umbrella spoke - so that made it around 3mm across, and more than useful for channelling balsa for such things as torque rods. Anyway I though you were going to go for a servo in each wing? Or are you employing flaps? If you are going the flaps route, they will have to drop quite a bit - 45 degrees? to be effective and the hole for the torque rod does get a bit large, but doable.

Regards the hinges - I only ever used a manual hinge slotter ONCE. It was like performing dentistry with a jackhammer.

 

I then bought one of these...

 

When working on a wot4 I cut all the slots in 3 mins flat, all dead acccurate and dead centre!! Probably a builder's must have item. Beware they are from the USA and work on 110V - so will need a transformer but one from ebay will cost a tenner.

Edited By Stevo on 19/11/2013 09:28:08

[Biggles' Elder Brother - Moderator]

Hi Colin,

I notice you say that the cub is your first model and you haven't flown yet? Its easy to see the Cub as a great trainer, but I would not agree. I've flown many Cubs - some my own, some other peoples - and I have one in my fleet at present. They vary enormously! Its easy to assume that, because they have a high wing and superficially ressemble a trainer, they must be suitable as a trainer - I'm afraid it ain't necessarily so!

Obviously some folk have used them to sucessfully learn to fly on - Ernie being an example here. But I would suggest that had they learnt on an actual trainer they would have found it easier. Cubs generally present a number of problems, but three are particularly noteworthy:

They have a rather narrow track undercarriage which can make ground handling challenging. Keeping them straight on take-off requires a fair bit of deft rudder work. Similarly preventing them from ground looping on landing needs concentration right up to the point when they stop rolling - I've seen more than one Cub come to grief because the pilot mentally relaxed once the wheels touched down only to have the Cub develop a "mind of its own" in the roll-out!

They tend to suffer from an effect called "adverse yaw" - basically their down-going aileron generates so much more drag then the up-going one that it acts to pull the model's nose out of any turn. The degree to which this happens is very variable. I've known it to vary between Cubs from some on which it is hardly noticeable to ones on which any sort of turn without co-ordinated rudder is all but impossible.

The original Cub was one of the very few full size aircraft to have a Clark-Y aerofloil section - popular in modelling but not particularly so on full-size aircraft. It is a high-lift aerofoil - which has good points and bad. You have plenty of lift, even at low airspeeds - so you can fly Cubs sucessfully very slowly which is good for beginners. But (there is always a "but" in aerodynamics!) its also means that Cubs can be a bit of challenge to land with precission - as has been said above they tend to float on, and on, and on,..... not the easiest of situations when you are trying to learn landing skills! Secondly the aerofoil is dreadful inverted. OK I know that as a new pilot you are hoping not to get invereted - but the time will come when you either get disorientated and acidentally half roll it inverted or at least near inverted, or you might want to just start some gentle aerobatics as your confidence growns a bit. Because of its aerofoil Cubs generally drop like a stone inverted! If this happens to a beginner as a result of accidentally near inverting they invarably panic - the result is often the loss of the model.

So what to do? Well forewarned is hopefully forearmed - so knowing the above you can be better prepared and have a careful think about how you are going to handle this. I'd suggest three things:

1. Join a club which offers proper instruction.

2. Why not get yourself a cheap second-hand trainer so you can "get your hand in a bit" before tackling the Cub? You could be learning to fly whilst still building the Cub!

3. Whatever you do - don't maiden the Cub yourself. You have put a lot of effort into building this - you do not want to take it home in a black bin bag! If you join a club the instructors will not only teach you to fly on a trainer they will do the maiden on the Cub for you as well. Once its trimmed out and all is well you can then take the controls on a buddy lead and so get the feel of it gradually.

I know this might sound a bit over fussy - but as I say this Cub has cost you significant money and probably a lot of time.

BEB

[Stevo]

There's some sound advice there...

I have to admit it did not handle like a trainer and yes definitely co-ordinated rudder on the turns, and as I had a servo per wing I did program in aileron differential as well.

Take off required immediate rudder (retrospective - fit a gyro....) but I cant say anthing about landings, as I didnt have to do one with mine

[Colin Anderson]

Hi again Stevo,

I am going to be using two servos in the wing for the ailerons, but I haven't got that far yet. Yesterday I was attempting to do the elevators and rudder - basically making a pigs ear of the job! The rudder seems ok; it's free both ways, although it only flops to one side under its own weight in one direction - so it's more free in one direction than the other. It was the elevators that gave me grief, especially with the torque rod. In the end I made such a mess of the job I decided to make two new elevators; I'll try and cut the slots today.

You're right about the gouge; I came to the same conclusion eventually, but a little to late! I'd tried to make the hole for the torque rod using a drill bit fitted into a handle; it just chews up the balsa. Regarding the hinges: the gauge only really seems to help align the tool centrally, it doesn't help keep the tool perpendicular! I'm going to try to solve this by adapting the technique shown in David Boddington's building and flying radio control aircraft. To be honest I wished I'd thought to cut the tailplane/elevator, fin/rudder slots before fitting them to the fusalarge; it seems to me that this would have been easier! In addition I should have marked out the slot positions on all parts before slotting, instead of marking the second set from the fitted hinges in the first set. Hind sight is a wonderful thing! Oh well, it's all learning.

Regarding the American slotting tool: looks like a good idea for a future investment; this or something similar. I don't use EBay, because I'm one of those Luddites that doesn't trust it! I know that millions use it the world over and they're fine, but still.....

[Colin Anderson]

Hi BEB,

Got the notification for your post after I'd already posted in reply to Stevo!

The Cub I'm building is by Flair and is sold as a trainer; I bought it following advice from Sussex Model Centre (local shops don't seem interested in selling kits!). Your advice on buying a second model (RTF?) I'd agree is very good advice indeed. However, as I only had funds for one plane I wanted to go the kit route. If I tried to buy a second plane at this point I'd probably end up divorced!

I have build models in the past (a long time ago). I used to build free flight and control line. Back in those days radio control was just a dream and out of reach. Working for the NHS (37 years) put paid to my modelling. Having taken early retirement last year I'm now determined to get back to it.

I fully intend, when the model is built, to join my local club (Slough); I've been to see them fly many times. I wouldn't attempt to fly alone, as I have no wish to take home a box of firewood! Apart from that I don't know anywhere around my area where it could be done. Back when I flew control line in the early 70's you used to be able to fly most anywhere, but things have changed.

I thank you for you advice; I will find it of great help. I'm glad that you guys are out there and so freely willing to offer help and advice - it's heartwarming.

Cheers guys!

[Ernie]

Oh come on BEB, mine was a great trainer, I was solo in only couple of years

ernie

Edited By Ernie on 19/11/2013 14:09:17

[Biggles' Elder Brother - Moderator]

LOL!

BEB

[Colin Anderson]

The build is now back on track. I cut hinge slots into the new elevators and made a much better job of it. As before I used the guide that comes with the Dobro tool to align the centres. To get around the problem of the cutter not going in perpendicularly I placed the tool flat on the bench, packed the elevator up to the correct height and worked the tool in. It worked! The slots were dead perpendicular and much neater. I got the idea from David Boddington's book. I used a very sharp nail to make the holes for the toque rod; this was much more successful than using a drill and straighter too. Next I filed down the ends of the torque rod a little to make them slightly slimmer - this will leave slightly more material around the rod within the elevator, without compromising its strength. The elevators now work properly, as does the rudder.

[Colin Anderson]

Wouldn't it be great if things were easy! Today I decided to trial fit my Ervine 40 so that I could work out where to bring the push rod through and where it would sit to allow the fuel pipes through, prior to fitting the top cowl sheet.

The first problem is that the engine doesn't physically fit between the bearers! This will only require some minor fettling of the inside top edges of the bearers to allow the crankcase to fit in and not enough to compromise their strength. However, with the engine moved forward to the front bulkhead there isn't sufficient room for the fuel pipes and tank cap to come through! This means that as the tank has to go in before the engine ( because its under the sheeting) I then won't be able to slide the engine in!

There appear to be 3 possible solutions to the problem: buy and fit the smallest allowable engine for this model; cut the front bulkhead and probably part of the nosepiece too; or make an additional bulkhead and move the tank back. I'm quite reluctant to start buturiing the front end as I'm worried about reducing strength, but my feeling is that this might be the only way forward.

As this model was designed to take glow engines up to the size I have I would have thought that suffient space would have been provided. I guess I was nieve!

[Ernie]

Hi Simon, It's never easy. Thats the fun of it. I think I understand the problem. A pic. would say many words

The bearers are easy. I'd avoid sharp corners where the chamfers begin. Is it not possible to move the tank back a bit? Around a centimeter wont make much difference. You can lengthen the feed pipes, and take them through the bulmkhead.

ernie

Hey, it's looking great

[Colin Anderson]

Hi Ernie,

Thanks for replying, but first, my name isn't Simon! Chamfering the bearers, as you say, will be quite straightforward. I understand your point about the sharp corners, so as not to introduce stress points. My thought is that rather than resort to buturery at the front end I'd prefer to move the tank back; this will necessitate adding a partial bulkhead behind the present one in order to support the tank neck. It will mean making 2 holes in the upper decking as well for the and vent pipes.

Now a couple of questions: if the fill pipe is blocked of during flight, does it have to be upright? Also, if the vent pipe is connected to the silencer, does this need to be upright? If the answer is no then I can bring tubing from these through the bulkhead, rather than up through the upper decking. Regarding the fuel tank: I figure I've got some leaway, as the bigger engine is heavier than the smallest engine for this model. How far could I get away with moving the tank back? By passing the fuel tubing through the left side of the bulkhead, rather than using the original centre hole I guess I could manage the centimetre, but it will be quite a fiddle. If I move it back about an inch it will be far easier. If I can get away with most or all of the above it will save me chopping great chunks out of the front end! As it is, most of the front decking will have to be cut away at the top to allow the engine in, access to the needle valve and access to the engine bolts. - because the engine hasn't been run in yet. I'll also have to provide some relief at the front bulkhead for the throttle linkage, because at the extent of its travel it just touches!

[Stevo]

Colin/Simon/Bert/George..

I'm of limited use here as I redesigned the whole front end to slide things in and out including re machining a complete set of bearers. I used SLEC orange tank. It never flew long enough to empty it!!

A few pictures would be of use here !! I really IMHO do not think that moving that tank back 1cm or so would make much of a difefrence, the plane is balanced tank empty and slightly nose heavy anyway. When fuelling up, it would make the nose heavier which is certainly on the side of safety.

The Irvines come up a tad larger than lets say the SC but that does not detract from thier reliability. Very trustworthy engines those.

I would guess that fitting an engine to this and preserving the scale font end is a) what you are trying to achieve and b) making it look less like a trainer, which lets face it has a bulkhead, engine mount and two side cheeks.

That's the main reason for making mine inverted, again not without its engineering challenges.

Talking of challenges, routing the throttle is always a challenge. I've used bellcranks and levers etc for my four strokes and even relocated the throttle servo or fitted a 9g servo as well in a very different location to get it to function straight and true. As long as it does not bind anywhere and is secure.

Steve