Flair Cub Kit.

[Colin Anderson]

Thanks Steve,

I guess I'll move the tank back then, as that will be the easier and neater solution. The only drawback as far as I can see is that the filler and vent pipes will have to come up through the upper decking, rather than the engine bay. Fitting my engine inverted would have been a neater solution, but as the bulkheads and lower sheeting are already in place it's a little late without major surgery - so, upright it'll be and I'll live with the removal of the front sheeting.

Regarding the pushrods for the throttle; I can quite easily see how difficult this will be. I'm thinking that it might have been wiser to put the holes in before assembly! Nevermind, I'll work it out. I'll try to put some pictures up at some point or perhaps I could send them to you. Did you get the email I sent you?

Concerning a previous post regarding joining a club: I tied contacting my local club (Slough) which can only be contacted via their forum, so I registered. I got an email back to say this would have to be confirmed and then they'd send me a further email. So far this hasn't happened, so I guess I'll have to wait for a sunny day and go to their flying site and talk to them. I did have a look at Maidenhead, which looked impressive, but at over £100 to join I can't really justify it at present.

[fly-navy]

Posted by Stevo on 20/11/2013 19:14:03:

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

Don't forget the important bit either eh Stevie!!!!, I'm back to frighten you

[Stevo]

I'm glad you didnt change your mind and invert it.. The thrustline would have been out by 12mm, and that's why I raised both engine bearers up by that amount, remaking all the forward bulkheads!

Having a very long drill around 4mm diameter certainly helps when doing the linkages. If it's not straight forward, i get a straight a rod from the throttle lever as I can into the servo bay, and mount the servo there.On my blackhorse Canter, it was around 200mm between carb and servo arm, and after four attempts and TWO hours, it was perfect and when correctly set up with the Tx, paid dividends - dont compromise here.

[Colin Anderson]

Thanks Steve,

I've just downloaded an viewed the images that you sent me, so I can see how you fitted your engine and the mods you made to the bulkheads. If I'm not mistaken you tank appears to be as far back as I'm proposing to site mine ( with the rear close to the servo tray) - am I right? Also, the filler, vent and fuel pipes all appear to exit at the underside of the model - so these pipes don't need to be upright then?

Your undercarriage is a work of art! How I wish that I had the skills and the equipment to achieve such a neat piece of engineering. That's some set up you have. I noticed numerous improvements that you made to your model and all beautifully executed - and yes, I saw the stitching too. I also noticed the cat (yours?) performing guard duty!

I'm still non wiser as to whether you got my email, but regardless I thank you for the images that you sent; they are excellent , very helpful and have given me much food for thought.

[Stevo]

Oh sorry yes I did get the email...! Been a long day.. apologies..

As long as the route from the clink to the carb as not kinked and does not give rise to airlocks to me that's all that matters. The tank can be filled from anywhere, and the vent from tank to exhaust to maintain a head pressure again not to fussy.

The milling machine has since been sold on unfortunately but I've a host of other things that get me by. You may want to look here

Yes that was Podge, one of our cats.

Steve

[Colin Anderson]

Thanks Steve,

I enjoyed that! Excellent work!

[Ernie]

Hi Steve, Sorry about that. I reckon you've got your answers above.

Anything else?

ernie

[Colin Anderson]

This is how the tank is supposed to be fitted.

[Colin Anderson]

Another view.

[Colin Anderson]

This is what I'm proposing to do.

[Colin Anderson]

As you can see; if I put the tank in the position that the instructions say then I can't get the engine in! Moving the tank back and routing the fuel pipe through the original hole seems the best solution without major surgery. The engine bearers had to be relieved on the inside edge in order for the engine to fit! Had I known this prior to the build I could have placed them further apart! However, as this kit is designed to take an engine of this size (an ali plate is supplied for smaller engines) I hadn't thought it necessary. Getting the engine bolts in is going to be interesting! Should have done this before also!

The filler and vent pipes will now need to come out of the top decking, but I'm open to suggestions if anyone has a better idea.

According to the kit instructions the receiver and battery should go under the tank. However, once they're in there they are going to be pretty fiddly to get out again. suggestions? Course if I crash it they'll be easy to retrieve!

[Colin Anderson]

It's been pointed out to me (thanks Steve) that I'd fitted the tubes into the tank wrong! Anyone viewing these images please don't copy my mistake; the curved tubes should be inside the tank! I've already been in the corner with my pointy hat with the big D on it! I've now remedied this, ahem, over site. Please feel free to comment - I deserve it

[GrahamWh]

I didn't spot that as I was looking through - until I read where you typed it! At least you have somewhere you can stick the batteries now without having to go under the tank - a little hatch on top would give good access for a battery change on a long flying day.

[Stevo]

I would widen the gap behind the tank so it slides out - and make a piece of py that screws in behind it, holding the tank in...

[Colin Anderson]

Graham,

I don't know about long flying days! If my present progress is anything to go by my flights are likely to be short! That's if I get off the ground in the first place, as so far my local club has not got back to me.

I'm assuming that you're suggesting that I place the battery in front of the tank in its new location? There is actually more room under the tank. I'm new to R/C so do people change flight batteries on a long flying day or recharge while others fly? Or is this a silly question?

[Ernie]

Hi Colin, you shouldn't need to remove batteries very often (once every few months to check em out) Of course, you need a socket easily accessed to charge it. I sometimes make up an old credit card, with the on/off switch, fuel filler, battery charger, and battery monitor on it. I then fix the whole thing to the fuselage, well away from the exhaust

ernie

[Colin Anderson]

Thanks Ernie,

It makes sense to me not to keep removing the batteries unnecessarily and cutting hatches in this particular model could, potentially, compromise its integrity. For this model I'd probably leave the charge lead safely tucked inside the cabin. This shouldn't be too much of a pain ' cause I'd have to leave the wings off to store the aircraft anyway.

[Colin Anderson]

It's strange how things go sometimes. Going back over the kit instructions I read that the front bulkhead would need to be cut, along with the cowl, in order to provide clearance for front induction motors; I'd read this before, but hadn't taken too much notice, as the engine seemed to fit just fine. However, today I decided to trial fit the cowl. This is where I got a surprise; with the engine at its present position it wouldn't allow the propeller to be fitted! At this point it looked like I had two choices; either cut down the cowl to make it slimmer or cut away part of the front bulkhead and cut away a section of the cowl. With the engine at its present position the carburettor and throttle arm were hard up against the front bulkhead and potentially this could be a problem. I resolved, therefore, to relieve the bulkhead and cowl. The result: the engine is now further forward and easier to fit, there is room for the propeller, as well as more room behind the engine. This has allowed me to move the tank forward to nearer its original position, so it's now only 1 cm behind the bulkhead.

[Colin Anderson]

As an aside, the very kind people at Slough Radio Control Models let me try out their flight simulator. I have to say this was a serious wake up call. I managed to get the simulated aircraft of the ground each and every time, climbed and banked to the left. The first time I did this I was impressed; I'd got it of the ground and successfully made a turn - perhaps I had a natural talent? Er, no! No matter how hard I tried I couldn't complete a circuit! Every attempt culminated in a crash. Oh dear! Had this been the model I'm building I would have been taking home a jigsaw.

So, it looks like I'm going to have to invest in a copy of "Real Flight". It's not cheap, but not is my present build. The only question is whether to buy 6.5 or wait until 7 arrives here (I know it's available in America and that there's a free update - although this only seems to be available there). Do I buy now or wait and see if there will a sale? It's available locally for £135, which is some £15 cheaper than elsewhere, if anyone else is looking.

[Colin Anderson]

No building today; instead, hours of fun setting up the throttle linkage. The whole operation was like a Chinese puzzle! Eventually, I got it right; but I almost pulled my hair out! On my first attempt I had about the right length on the pushrod, but too much travel. Moving the servo clevis to the third hole in on the arm and gradually adjusting the pushrod length eventually got full travel forward and idle position rearward; pushing the engine cut completes the remaining rearward travel. Perfect!

Fitting this first servo has dictated a decision on whether to fix the tank in position or allow it to be removable. If the tank were made removable it could only be moved back far enough by removing the servos. This being the case I've decided to fix the tank in place.

[Colin Anderson]

I'll try and put some images up soon. Progress has slowed a little, as for some inexplicable reason I had problems with the second half of the wing; the first half went without a hitch. Everything seemed fine until I tried fitting the leading and trailing edges. Both were marked off from the central spars (as per the first half), but nothing would line up! Eventually I made sure all ribs were square and glued in both pieces. It's all correct now. Putting in the bottom sheeting again produced a small amount of washout. Having pinned it down I then weighted it for good measure while the glue set. The next day it was mercifully flat.

I spent ages setting up the elevator and rudder servos with their respective pushrods. I was not too happy with my first attempts. I set everything up as per the instructions (still think a plan would be better), but both rods were binding and couldn't move over their full travel. My solution was to cut some of the pushrod off at the tail end (to allow full travel range) and fix the servo linkages to opposite sides of their servos (which meant reversing the elevator servo).

So this brings me to some questions: I thought that the elevator and rudder throws were small; so I changed the servo arms from the small round ones to ones with arms to get better throws. So, did I do the right thing? What should the throws be for a trainer? I've got about 25 mm each way; the instructions say 20 mm, so I figure I'm close enough.

Pushrods: the wire ends should be as short as possible. At the servo ends I've kept this to about 30 mm; however, as I've had to shorten the pushrods at the tail end the length of the wire ends is longer. So my question is, how long is too long?

CG: as I put in a 40 glow (which had to be moved forward to fit) the balance point is toward of where it ought to be (and I haven't put the battery in yet); it's at 60 mm instead of 85 mm - this in the uncovered model. How much will this effect the flight characteristics?

[Ernie]

Hi Colin, You don't want huge throws, after all, it's a cub and a trainer, I'd set up with dual rates. Small throws on low rates, big throws on high. 20mm on high rates should be enough. maybe 10 on low.

Wire ends depend on the wire used. Bicycle spokes are good if you can get steel ones that take solder. 50mm should be fine. Check when it's all working. There should be no bending.

Probably the most important thing of all is the CG A wee bit in front of what is shown on the plan is Ok, but not behind, or you will have a tiger by the tail. Can you move the battery around to achieve this? It always seems a shame to start to add bits of lead.

ernie

[Colin Anderson]

Thanks Ernie.

Pushrod ends: I've checked for bending ot the limits of travel and there is none. I'm guessing that the loading on the control surfaces of a trainer will be low, so there shouldn't be any bending under load.

Control surface throws: From what you're telling me, I've probably gone overdid things by changing the servo arms from the small round ones to ones with longer arms! When I first put the rods in I was surprised at how little the elevator and rudder moved! This was because I'd checked my hinges for freedom of movement by moving them through 45 degrees each way! Well I'm learning! Perhaps I'd be better off by refitting the original servo wheels and measuring the throws. I'm assuming the 20 mm you refer to is each way for both elevator and rudder? A total of 40 mm (high rate) and 20 mm (low rate)? I'm also guessing that the low rate is for training?

CG: As stated above; the CG is supposed to lay at 85 mm back from the leading edge, but at present it balances at 65 mm. The Irvine 40 had to be moved forward by about 3/8 of an inch, otherwise the prop wouldn't have cleared the nose piece! The combination of a heavier engine and slightly longer movement arm has brought the CG forward. I've fitted the throttle servo as per instructions to keep the pushrod (which has to dogleg around the tank) as short as possible. However, I moved the rudder and elevator servos behind the CG to redistribute the weight and keep these pushrods shorter. I'm fitting two aileron servos which, being in the wing, will be just behind the CG. As yet the model is uncovered; but solar film isn't that heavy, is it? To get the balance point exact at this point would mean putting the battery halfway down the fusalarge! Obviously not practical! The original instructions advised the battery to sit beneath the tank, along with the RX. My plan is to put both on or near to the CG, sitting behind the throttle servo. This placement will be the most convenient for access, but won't change the balance point. I'd rather not, as you say, resort to lead, but at this stage it's looking like the best option - I'm figuring that a tiny amount at the tail end might just do it.

[Stevo]

Hi again,

Dont get bogged down with rates at the moment - I set mine to the lower end, and it performed very well and there was no need to increase them at all. Suprised at it being nose-heavy - with my Saito 56FS up from it balanced right on the money. With the Cog at 65mm it will fly but will be a bit sluggish - are you doing this with the tank empty?

However double check all your CoG measurements! I never found that performing major surgery in relocating servos and batteries ever made that amount of difference, I use the LiFe batteries now which dont really make much odds where I put them as they are so light.

Visit your local tyre place and offer them a couple of quid-no-questions-asked for some of thier sticky weights that they put on Alloy wheels... That will do the trick should they be necassary.

Steve

[Colin Anderson]

Hi Steve,

The CG position is a mystery to me too; I'm sure your engine must weigh more than mine - but maybe not. The fuel tank is currently empty. You're right about the battery; it's so light that its position makes very little difference. I'll solve the mystery eventually, as while I don't want a tiger, I don't want a slug either!

I'm not worried about the control surface throws now that I know that they don't need to move as much as I initially thought they had to. Today I replaced the original servo wheels; I then moved the rear links two holes nearer to the hinge line and that sorted things out! I now have exactly 20 mm of movement. I set the lower rate to 50 % on the transmitter, so I now have the required 10 mm. I'm learning all the time here! It just needed someone to get me to look in the right direction.