Having trouble flying inverted

[paul devereux]

15 hours ago, Rich Griff said:

How I envy you Paul...

Is your site "private land" ?..

You do shout out LANDING even though no body is about don't you.

It's not actually that good, tbh, unlike a club there is no one to give advice or support, and it can get a tad boring. Because I ride (rarely now as I'm old) I own a field amongst grazing land, I'd don't actually shout "landing" as that would be too sophisticated for the local residents, Dinner!, Back up! and Off my foot! is about their limit, lol! Though I am very mindful of other riders on foot or mounted as horses are easily spooked, and don't take off if anyone is around.

One thing I have learned is, I wouldn't recommend anyone learn to fly at any place other than a club, even though the BMFA insurance allows us to do so, and that's the advice I always give if anyone shows an interest. Apart from the obvious that you are going to lose control and crash on your first flight, to learn to fly you have to keep plugging away doing the same thing over and over again. I used to try to do at least one flight every day, even if I didn't want to really (I remember reading about "prop up the low wing"- that only works at the early stages, you have to get past that so the orientation is instinctive). I only did it because I have the space, and have to visit daily to do chores.

[Martin McIntosh]

Not ploughed through the whole thread but as an ex aerobatic flyer, from what I have read about a neutral cg is simply rubbish. In the days of single channel, no elevators, this could be done to achieve some sort of inverted flight but no point in doing that now. Even with lots of expo it would make your elevator control very sensitive.

 Stick with the normal cg position as recommended, use about 40% expo and reduce the travel. You can then push quite a bit of down without the model jumping around.

I set up my models to spin with about +20% movement on high rate rudder and elevator so that the spin stops when the controls are neutralised 1/2 a turn before the desired exit; more than that and the cg is too far back and vice versa.

[Peter Jenkins]

Martin

 

Had you read the whole thread you would have found that the words were "more towards a neutral cg position" and this was further clarified to be you still need to push a little down elevator when inverted and not a neutral cg position.  You've now introduced the spin when the OP was about flying inverted.  I appreciate that you were a top aerobatic pilot but I think you have rather muddied this thread.  I currently fly the FAI(P) schedule in competition, not very well I have to say, and have done so for the past 5 years.  I think most of the advice given to the OP has been good and your post has probably managed to confuse the OP.

 

Just my view of course.

 

Peter

Edited June 28, 2023 by Peter Jenkins

[Martin McIntosh]

Peter, since the advice was tending towards neutral cg I was merely pointing out a simple way to check this. Should have explained that I suppose. No confusion intended.

[Peter Jenkins]

Hi Martin, as you know, there are 2 schools of thought on CG position.  Some, like Bryan Hebert, a successful F3A designer, advocate a forward CG and his Triangulation Trimming method is based on that, while others advocate a more rearward CG like Andrew Jesky (a World to 10 pilot) advocate a rearwards CG.  It all depends on the design of the aircraft which is likely to be best suited to achieving the aim of balancing the different aerodynamic forces and how they make the aircraft handling feel.  I followed Jesky's recommendation for CG position on my last F3A model and that needed an aft shift from the middle to the back edge of the wing tube.  Having followed that, there was no mixing needed for knife edge flight whereas there had been before.  I know that in your day, Knife Edge flight was not used and so slim fuselages were used until, Mike Birch (I think) introduced the dolphin look.  Today, most competition designs have deep fuselages to meet the requirement for KE loops and integrated rolling and pitching manoeuvres.

 

However, for the purposes of helping the OP, if the model dives towards the ground once inverted then moving the CG aft is a great help and can also make the aircraft much nicer to fly all round.  Ending up with a small amount of down elevator for level inverted flying is a good place for which to aim.  Indeed, with a forward CG there may be insufficient elevator power to stall the aircraft something that might be thought of as being a good thing when learning.  The Germans built an aircraft, Zaunkonig, that was almost impossible to stall or spin to cater for very low hours pilots learning to fly on their own!

[MattyB]

14 minutes ago, Peter Jenkins said:

Hi Martin, as you know, there are 2 schools of thought on CG position.  Some, like Bryan Hebert, a successful F3A designer, advocate a forward CG and his Triangulation Trimming method is based on that, while others advocate a more rearward CG like Andrew Jesky (a World to 10 pilot) advocate a rearwards CG. 

 

I have never heard of that triangulation trimming method, but it is interesting - thanks for sharing it. I've only scan read it so far, but I'm not sure that he is truly advocating for a forward CG as is suggested int he instructions of most sport models, just a more forward CG than Jesky and the 3D guys.  I may expereiment with some of this thinking on my Miss Wind once I finally get to fly it at a site where the cruddy indercarriage design can cope!

 

17 minutes ago, Peter Jenkins said:

The Germans built an aircraft, Zaunkonig, that was almost impossible to stall or spin to cater for very low hours pilots learning to fly on their own!

 

Never heard of that, it is pretty cool and quirky design. Looks ideal asthe format for an esoteric slow fly parkflyer!

[Graham Bowers]

15 minutes ago, MattyB said:

 

SNIP  I may expereiment with some of this thinking on my Miss Wind once I finally get to fly it at a site where the cruddy indercarriage design can cope!

A bought a CF undercarriage for my Mythos 50e following being told they were weak. Still being assembled, so unproven - it may be a panacea, or may just transfer the load so the mount breaks. Anyway, it was an easy transaction. No connection other than being a customer.

 

http://www.ralphschweizer.com/startseite.htm

[Colin Carpenter]

My Axiome 70 bipe had a cf u/c. It only took a few landings on our patch before the plate took the strain and twisted. Changed for a Sebart Wind 50 u/c and now 50 up with no further problems as u/c absorbs loads. Colin 

[MattyB]

4 hours ago, Graham Bowers said:

A bought a CF undercarriage for my Mythos 50e following being told they were weak. Still being assembled, so unproven - it may be a panacea, or may just transfer the load so the mount breaks. Anyway, it was an easy transaction. No connection other than being a customer.

 

http://www.ralphschweizer.com/startseite.htm

 

Unfortunately I don't think that will help - the issue is where the undercarriage attaches to the fuselage, there just isn't enough structure and access is super difficult to reinforce it. I was able to make some limited improvements from top of the fuselage, but it's always going to be a weak point; to address it fully I sheeting would have to be reomoved so that additional structure could be added, then the model patched back up and recovered.

Edited June 30, 2023 by MattyB