Easy Glide C of G

[Peewhit]

Too much snow on the hills and no wind, so instead of my beloved slope soaring, I settled for taking out the old Easy Glider electric which I have not flown for about 12 months.

 

Being a bit more experienced in these things  than the last time I flew it, I noticed that it was swooping up coming out of tight turns and without a touch of down elevator would probably have stalled.

 

So, with the model trimmed out correctly I tried a dive test and with the C of G set at the recommended 70mm, it pulled out of the dive far too quickly.

 

This indicated that the C of G was too far forward so I taped a pound coin to the back of the fus (thankfully I was able to retrieve the pound coin later) and the Easy Glider behaved far, far better.

 

Back at the ranch, I measured the C of G with the pound coin in place and it was 72mm behind the leading edge, and I might try moving it back even further.

 

Note that my Easy Glider is electric with  the Mutiplex power upgrade therefore has more weight at the front than the standard powered or not powered version. I would not recommend sticking a pound coin on the back of a non powered version as this would move the C of G too far back.

 

Anyway, powered or not, when in glide mode with the power off, the C of G should be the same.

 

So, all you people with Easy Gliders, what C of G are you flying with?

Edited By Peewhit on 11/12/2010 15:23:10

[Pete B]

70mm seems OK for me - that's with a Rhino 2S 2350mah pushed to the back of the battery slot. Next time it's out I'll try moving the C of G a little further back and see what happens.

I've also reduced the 'down' aileron to almost nothing and that has improved the aileron response a lot.

 

Pete

[Peewhit]

Hi Pete,

 

Interesting about your down aileron reduction.

 

Mine is set up with with the recommended 20mm up / 8mm down and seems fine.

 

Like most planes, it does thermal turns far better with some rudder as well as aileron.

 

Try putting yours into about a 30 degree dive, let go of all the sticks, and see what happens.

 

Ideally, it should continue in a straight dive, or pull out very gradually.

[Tony Smith 7]

Posted by Peewhit on 11/12/2010 15:17:48:

Being a bit more experienced in these things  than the last time I flew it, I noticed that it was swooping up coming out of tight turns and without a touch of down elevator would probably have stalled.

 

I'm interested that you find that to be symptomatic of a fault.  I think everything that I've ever flown has needed a bit of down when rolling out of a turn, and I had assumed that this was just normal - the natural complement to the back pressure needed when in the turn.  

 

Not that "everything" is that much in my case, but includes a few models as well as weight shift hang gliders and also a bit of stick time in powered aircraft.

[Peewhit]

Tony,

 

I expect to have to give a bit of down coming out of a turn, but not so much that the plane would otherwise have stalled.

 

And that, combined with the dive test result did indicated a too forward C of G.

[Former Member]

[This posting has been removed]

[Pete B]

Posted by Peewhit on 11/12/2010 18:12:52:

Hi Pete,

 

Interesting about your down aileron reduction.

 

Mine is set up with with the recommended 20mm up / 8mm down and seems fine.

 

Like most planes, it does thermal turns far better with some rudder as well as aileron.

 

Try putting yours into about a 30 degree dive, let go of all the sticks, and see what happens.

 

Ideally, it should continue in a straight dive, or pull out very gradually.

 

 

I've reduced my down aileron to about 5mm so not that much difference, Peewhit. With the upswept tips, it has probably got some inherent dihedral effect which reduces the 'cleanness' of the aileron response anyway. I can switch in coupled Aileron/rudder when I'm thermalling but there aren't too many about at present.........

 

I tried the 30deg dive today and sure enough, it pulled out gently (ie it certainly didn't zoom) but when I get more time I'll move it back a bit more and see what happens.

 

It does fly nicely inverted, Eric but does need some down ele held in for level flight. Given the flat-bottom section, I'm not surprised!

 

Pete 

 

[Former Member]

[This posting has been removed]

[Terry Walters]

I maidened my old style EG (yes some people are still buying them!) last Sat at Pete Bs place.  It was a lovely blue sky day and the forecast was light winds but when it got away above the tree line it was not at all nice.  Very twitchy on all axes and prompted a swift return to earth and a quick wipe of the sweaty brow.

 

Had a good look at it on Sunday .  I have built mine without the 'ball' in the rear, added a carbon rod along the fuz and put both servos at the rear. 

 

The  2300 lipo sits in the excavated cockpit area with a hollowed out canopy above for better room to put all those magical things that make it work!   The rx sits in the original battery position near the wing roots,

 

Found the COG was a little fruther back than the last time I checked.  Personally I haven't read anything about random movement of the COG position so I assume it was my lack of precision when measuring it!  COG now altered to a proper 70mm.

 

So- yesterday -  further power off gliding checks in my garden - (I've only got a mere acre to play with unlike my land owning friend in the north who has more than 6 acres) - established that it could be a very nice docile lady who wouldn't hurt a fly.

 

So  - very nice here this am (log shifting/fire cleaning and Xmas tree to put in a bucket "by the time Madam gets back from shopping or else!!" ) and if the winds hold off I'll have another go this pm in the farmer's field out back and see what then!

 

 

[Peewhit]

It seems as though the "fingertip" method of measuring C of G for these light models is not precise enough.

 

Far better to set it up properly using a balancing jig (in my case, two nails in a piece of wood) as a couple of mm makes a lot of difference.

[Terry Walters]

Flew the EG this afternoon in fairly light conditions and it was improved but not perfect by a long way.  Allowing for my thumbs which have a combined age of 120 yrs the EG was very difficult to arrive at a trim that felt right and I think I need to check the geometry closely to make sure I'm not fighting a twist or misaligment.

 

The EG is seems much lighter than my Graupner Elektro which is more positive in the air and easier to place in the right bit of sky.

[Pete B]

I think it will take a few flights to sort out, Terry. It all looked pretty square to me. The EG feels much lighter and more floaty than the Elektro, which seems to fly as if it on rails! Putting the servos at the back on the EG, effectively lengthening the moment arm of the weight at the back, might have made it even more sensitive to pitch than the standard setup, with the servos in the front.

 

Of course, if you flew on a sensible mode, we could swap aircraft and try each other's out!! 

Pete

[Terry Walters]

Pete - thanks for that I think it's just dawning on me that with all my mucking about the COG may no longer be at the original design point of 70mm back from LE.  As it is set up at the moment there is a slight nose down at 70mm but I'm reluctant to push it further back as that will make it more unstable? 

 

More work to do but won't alter anything until I go through some trim tests whilst airborne.

 

Beautiful morning here only -7.5C but stunning.  BUT - bad news - Xmas present wrapping all morning!

 

Good news - Phoenix Rainbow on the way - might even get it tomorrow - 2 days to the UK is usual for Gliders - why can't the other suppliers do that - only £14 as well and you can have 2 or maybe 3 full size ARTF for the same carriage!

[Terry Walters]

Well wind wasn't perfect but after a morning of being very critical of the setup and following Peewhits entrepreneurial spirit I made a temp COG  rig by using 2 cork sanding block with a 'T' pin in each with the top turned to run parallel to the LE.  Managed to set it up fairly well I think.

 

Juggled things about and also noticed that the tail plane was slightly out of true with the main - sorted with heat generated by manual twisting!!!

 

Had about 6 flights with a little fettling in between and getting somewhere now.  I think COG is ok as I did the 60 degree dive into wind power off test and got a very gentle pull up on its own.

 

Still not how I want it yet.  I followed the instruction's concerning not glueing the engine in (so you can replace it!) but I think that the thrust line is all over the place as a result - anyone got views on this?  Tempted to secure it.

 

The general feeling I have is that it is a bit too susceptible to even light gusts. Would adding ballast inside the wing tube settle it down without too much cost in sink rate?

[Peewhit]

The EG without ballast is a "light wind floater" and in 10mph plus it is a bit like flying a kite.

 

Adding ballast should not change the glide angle but it will fly faster and therefore come down more quickly.

[Grasshopper]

My EGPro has had a good hammering over the past two years and is in the well dinged/mended class. It weighs 885 g and the CofG is 69 mm  back.

 

I fly off the cliffs in windy Brittany in anything from light breezes of 5-10 kph to 30+ kph.

 

In low/medium winds I find it completely stable and a joy to fly. Too nice-and-easy in fact and I have had to make a determined effort to move on to more challenging slopers.

 

In 30+ kph it handles well but I have been caught out when flying across the cliff face with inevitable results. Half a tube of POR and some carbon strip and it's back in the air in no time.

 

One change to the build I made was to put a carbon tube into the fuselage halves before I joined them so the fus. is very stiff indeed. Could this be making a (beneficial) difference?

 

[Pete B]

Both mine and Terry's have the CF tube mod, GH, but I've yet to experience the 'cartwheel' test to really try it out. The nearest I've got was when Dotty the Dalmatian got there before me and knocked off the vertical stab in her enthusiasm!

 

Why do dogs like R/C models so much???

 

Pete

 

 

[Peewhit]

At last have managed to battle through the snow and took the EG out again today.

 

C of G is at 72mm behind the leading edge and I was able to give it a good test before the prop came off! - now fixed back on.

 

For my style of flying it performs far better at 72mm.

In the dive test it now pulls out slowly as it should.

Thermal turns are much better with less up elevator needed to stop the nose dropping

and there is much less swooping up when coming out of a turn.

Loops are easier and it will loop more tightly.

 

Perhaps Multiplex are playing it safe when quoting 70mm as a slightly nose heavy model is easier to fly. and often recommended for beginners or maiden flights.

 

I do like to get the best performance possible from any model and this always seems to involve a more rearward C of G than the manufacturer recommends.

 

Now, if I can only get this beast to roll well! - any tips?

[Tim Mackey]

Chop 2 foot off each wing

[Peewhit]

Thanks Timbo - will try that

[Terry Walters]

2 days ago I had a really nice flying session with my EG.  Flew very well mannered and when the wind picked up a little it was possible to fly the ridge out the back which is quite gentle so I think the mix of setup and weather was just right.  Will still experiment a bit to see whether there is anymore to give but I was really chuffed that I had a good 45 mins of flying on 2 1800 mah batteries and neither was less than 7.4v when put on charge later.

 

 

[Tim Mackey]

In all seriousness, - not sure there's much you can do to improve the roll rate of this bird apart from the obvious maximum throws on aileron?

Would differential help??

[Peewhit]

Aileron throws are maxed with 20mm up and 8mm down so plenty of differential.

 

In all honesty, I do not expect an Easy Glider to roll well - will save the rolls for the Typhoon and Wizard slopers - if only I could get to the slope - too much white fluffy stuff

There is a nice southerly forecasted for Sunday/Monday so I might just have to get the huskies and sledge out