Colin Anderson

Hey! Now there's an idea. Snow skies on my Cub! :-D

Sorry Stevo. I guess I got myself all worked up for nothing! But, hey, it's all a learning process. I'd probably understand things better and maybe quicker, if I could get more flying time myself. But what with the weather either raining or blowing a gale (about 15 knots today) and a shortage of instructors I'm going to have to be patient. Back in the days of FF, rubber and C/L I nearly always knew what was going on and, if I didn't I could work it out by trial and error. Mostly error! But with R/C there is little room for error. Plenty of potential for error though!

Managed to get to our flying field today for some flying lessons. Got my instructor to take the Cub up just to recheck the trim. It flew well and, in actual fact, flew hands off. I was looking for the roll on take off and, to my surprise it was very slight! My instructor said not to worry too much. He reckons the roll is due to the narrow track, the bumpy field conditions and the wind. It would seem that maybe I was just worrying too much! Frustratingly, I was not able to fly myself today as it was far too windy. The Cub eventually broke its propeller when it tipped up. My instructor's plane also got tipped up and broke its canopy! We both came to the conclusion that it was better to give it up for the day. Today was not a total waste, however. CG was rechecked and found to be spot on. Lateral balance was also checked and again the balance was perfect. All flying surfaces were as they should be with no mis alinement. I've not been able to check the wing incidence yet, but based on what my instructor is telling me all is fine. All I need now is a wind free day. Ironically, that's exactly what we had yesterday; but yesterday there was no instructor! Oh well... Anyway guys thanks for your input and all your helpful suggestions. It is appreciated.

Thanks BEB, You might recall that previously I had problems with this wing. There was a very slight warp on this wing induced by either the leading edge sheeting or the covering. I'd removed this problem, but I think I'll need to recheck this to ensure it hasn't come back. It is for this reason that I've seriously considered rebuilding the wing; I believe that the airframe itself is as good as it can be. I received a call today from one of our instructors whose trying to organise a transmitter comparable with mine. Hopefully I might be able to sort things out within the week or at least know where the problem lays. As an aside, although my nickname is Lobo, some people, tongue in cheek call me Biggles on account of my motorcycle goggles and my white scarf flapping behind me. So that'd make you my elder brother, wouldn't it? ;-D

Hi Pete, Lateral balance is one of the items on my list to check. Because I left the wing in the clubs container I'm not able to check this for the present, but I will. The method you advocate for the Cubs take off is exactly what I do in the Sim RF7. I don't know what my instructor practices. However, he is a full size pilot flying commercial airliners and a Pitts Special, so I'm assuming he does as you advise. Never the less, as soon as I get an opportunity, I will ask. If it turns out to be something this simple I will be so relieved! Keeping my finges crossed!

Ah, that is most illuminating and quite different to what I was previously used to with F/F and C/L. I hadn't realised that trim had to be adjusted so many times! However, I'd ask this: how is it possible to adjust trim at the actual moment of take off? During the climb, yes; and then straight and level, followed by landing. But surely trim has to be correct for that initial split second as the wheels leave the ground.

That's encouraging to know, Martin. So, even were my wing warped it ought to still be possible to trim for level flight and not induce roll at take off? This being so then the remedy to the take off roll lays elsewhere?

Hi Martin, Yes, I did build the wings myself. Although I'm new to R/C I'm not new to building; although prior to this Cub it was a long time ago. The leading edges do have the correct and same profile. My wing does have ailerons and as you say I can use them to adjust the trim. However, (and this is where my knowledge is rusty) don't control surfaces have a greater effect as speed increases? If so trimming the ailerons for level flight might induce roll on take off? Please enlighten me on this.

I'd be inclined to agree with you, but I'm checking everything. I plan to go through the list of suggestions; it's a process of elimination. As soon as I can get down to the patch again and get the assistance of an instructor, I'll be checking the alinement of everything most carefully. If it does turn out to be the wings then maybe I'll bite the bullet and have a go at making another set! We'll see.

Checked some of the suggestions on the fusalarge today. The fusalarge is level on its undercarriage, which is tracking correctly and there is no binding on any of the wheels. The tail wheel is fine and is not bent or out of line. The tailplane was found to be 1/16" high on the left, which I've corrected ( and hopefully it'll stay that way). Possibly a very slight twist was induced at the covering stage. Whether this contributed to the symptoms and whether or not it has alleviated them I won't know until I can once again get down to the patch. Watch this space!

Wow guys, Been sitting down watch a film and all your replies came in. Sorry about that. OK, first, the rubber bands. There are 8 of them, so I don't believe the wing is lifting. Second. My pilot did mention that perhaps my Cub needed more rudder throw and it does fly with a very small amount of right rudder trim. Lastly, now that you mention it BEB, he did mention that the Cub's narrow track might be a contributory factor. I had forgotten that!

You've got me there, Martin. I must confess that I didn't get around to asking him this, as I was still on a high from actually flying something I'd built with my own hands. If this happens at my next opportunity I'll ask him. He didn't say it would be a problem for me, but looking at it I'm thinking myself that it might be. I'm wondering if, when it comes my turn to attempt a take off, whether my reactions will be fast enough. Flying a Cub in RF7, if the throttle is set right, it simply rises off the ground and only slight input from the elevator sees it climbing. This is what I expect my Cub to do, but currently it doesn't. However, in flight it's actually easier to fly for real than in the Sim!

OK guys, this is all very helpful and sage advice. However, as mentioned at the very beginning of this post, these were my very first flights with R/C - ever! So far I have not undertaken a take off nor landed this plane. As a full size pilot my instructor did not yank my Cub off the ground, he didnt even use full throttle; I'm quite sure he knows what he is doing.

So Tim, The opposite to how I was visualising it, but the same mechanism? On take off then, this would mean the left wing is low (assuming incorrect positioning), but as the Cub unsticks the left wing rises to equalise the dihedral and therefore induces roll to the right I until stability is achieved in level flight? Am I visualising it correctly, or am I showing my ignorance here? I'm willing to learn 'cause although I have a reasonable knowledge of aerodynamics, I'd be the first to admit its become rusty and has glaring holes.

Hi Tim, No, the wing is held on the old fashioned way. This being the case I guess it's quite possible for the wing to go on in a slightly different position each time or even incorrectly. I will have to look into this.

Thank you Tim, I will look into this as soon as I can get down to our patch again (as I left the wing in the container 'cause it only just fits in my car!). If I'm understanding this right; if one wing (the left) is high this changes the angle of attack and thus effects lift, causing that wing to rise further - that is, roll. Is this correct?

Yes, Stevo that's why I'm confused. And if it really was running backwards with a pusher prop I think I'd get my coat and join you! :-D

To answer your question first Will. The Cub is taking off directly into wind. My instructor is a qualified pilot (passenger jets and a Pitts special) so I have every faith in his abilities. Hello once again BEB! Viewed from behind the model the left wing rises, the Cub rolls to the right and begins to turn. It is definitely a roll, rather than yaw. Stevo has sent me a very informative email with enough information for me to get to the bottom of this. I'm sure between us all we'll solve the anomilly! Edited By Colin Anderson on 06/04/2014 18:38:10 Edited By Colin Anderson on 06/04/2014 18:39:26

Now that you mention it, Stevo, you're right the rails are set slightly downward, producing down thrust. I'm still sure about the right thrust, though. This is the problem with a kit with no plan; a plan would make things so much easier to see and refer to. I wouldn't say you're a million miles away, as I sometimes visit my sister in laws in Chislehurst, but I take your point. As for the email, I never got it. I did look in the usual suspect places and its not there either. Any chance you could resend it? Incidence gauge? Yes, that's a good idea. You can see why I'm confused though. In theory a problem showing up at take off out to affect the plane's flight characteristics to some degree. However, thanks to you guys I've got quite a few suggestions. The answer is in there somewhere. I'm sure I'll find it.

Interesting you mention the tail wheel, John. The tail wheel is connected to the rudder which, as I stated above, has slight right trim. However, at the point where the model rolls this would not be on the ground. Hi again Stevo, Are you coming to my resque again? Are you saying that the Flair Cub has built in down and right thrust? If so, I hadn't realised. My referral to the prop wash was concerning the right trim on the rudder. I was just wondering if a higher prop was on take off would give the control surfaces more "authority" and thus induce the roll. Regarding wing geometry, incidence or warp; I can understand how they would effect the plane. However, if problems effect the plane on take off why do they not manifest themselves during normal flight? By the email, do you mean previous ones or have you sent me one recently? I did send you one recently about my first flights, complete with the pilot you kindly sent me. Perhaps you never received it? Regarding your very kind offer: I'm in Langley, Berkshire. How far apart are we?

Thanks guys, I will check this out as you both suggest. If it turns out to be so simple I will be very happy!

Hi Ken, The undercarriage is something that never even crossed my mind! Could it really have that effect? I'll have a look at that. Thanks uncle, cousin, distant relative? :-D

Hi Budgie, There are no thrust wedges. I will check the CG as you suggest. It is correct fore and arft, but I never checked it laterally. I will also check the wing and see if its heavier on one side than the other. Thanks for that. If these issues turn out to be correct; why would it only effect the take offs and not the rest of the flight? Is it due to more prop wash on take off? Power is an Irvine 40 glow in a 73" Cub.

Hi Andrew, Yes, that makes sense. However, my thrust line is central; no left or right thrust and no down thrust. There is a very small amount of right trim dialled into the rudder, as it had a tendency to fly to the left. It is a very small amount, but could this be the reason? And, if so, why does it not effect the plane once airborne?

Hi Guys, I have a Futaba 6EX. When I put the model and TX on charge, via the supplied charger there are two LEDs that light up red. When fully charged the Red LED for the model changes to green, but the LED for the TX stays red! It has always done this from new. The TX appears fully charged, but I'm puzzled as to why I should only get one green LED and not two. Is this normal for this set? If it isn't then, what is the significance? Cheers