how do you keep your RES on its back?

[xtc]

many,many differant times now i have heard of guys that fly there RES gliders on there back as if this can be done quite easy but my sagitta 900 will not stay inverted without a ton of control input and i personally think that it would be nearly impossiable to keep it inverted especially if there was any turbulence around

so whats the trick ,im balanced out a 38 % ,,i got tons of throw ,strong servos etc but the best i can do is about 10 seconds before it rolls over up right


xtc

[OVSS Boss]

I have never tried it with a Sag, but my Grand Esprit does it quite easily, just some down and I start a spiral and down it comes. Your CG sounds dead on, but I guess when I had a Sag, I just popped the spoilers and let the nose drop straight through the vertical down line.

Marc

[fly1milehi]

could it be something to do with the balanced rudder of the Sagitta? I know it produces some unwanted effects in upright flight modes so Im guess that inverted it is even a bigger factor? Especially since you say it rolls over upright.
Greg

[daveosoar]

If you cannot hold it inverted its nose heavy. If it screws out you may be compensating for lateral weight by aileron (if you have it) subtrim. If not check the rudder centralisation. Its VERY important. Whatever your model check, and check again, the lateral balance. The lighter the loading the important it is..
Dave.

[markdrela]

many,many differant times now i have heard of guys that fly there RES gliders on there back as if this can be done quite easy but my sagitta 900 will not stay inverted without a ton of control input and i personally think that it would be nearly impossiable to keep it inverted especially if there was any turbulence around
so whats the trick ,im balanced out a 38 % ,,i got tons of throw ,strong servos etc but the best i can do is about 10 seconds before it rolls over up right
The main requirement is being sufficiently fast on the rudder to prevent it from rolling out. The larger and slower the glider, the easier this gets. If the lift is good enough, my 3m Bubble Dancer is pretty easy to fly upside down almost indefinitely. With the 2m Allegro-Lite it's also doable, but noticably more work. Having lots of rudder authority and low yaw inertia (light tips) also helps a lot.

[Jim_Marconnet]

Just curious why you'd want to fly it inverted?

[Ollie]

With dihedral or polyhedral, the inverted plane is not stable in roll. So, the flyer has to correct the control instantly and constantly for the inverted plane in roll. The flyer needs very short reaction time to correct the unstable inverted plane in roll. It is like balancing a pencil point on a finger tip and and no other support. You can improve your flying skills. Don't expect the inverted plane fly for more a few seconds with poor flying skills.

[flystoolow]

My sagitta 900 will not stay inverted without a ton of control input...so whats the trick?
xtc

Well, it is indeed very possible to fly the Sagitta inverted for as long as you like. In a large, strong, and smooth thermal, you can even gain altitude while circling inverted.

There are two tricks to it:

1) The first is as M. Drela has just stated, be on top of every little wiggle, and correct them immediately with small control movements. The worst action is to start overcontrolling the glider, sending it into wild oscillations.

2) The second is to fly faster (about 10 mph faster) than the stall speed. Mushing around inverted is a sure way to end your inverted flight. (I have a feeling you may be flying the Sagitta a touch too slowly inverted, necessitating "A ton of control input")

Good luck...break a wing!

[schrederman]

Check your wings for warps. If it's absolutely straight, it'll be easier to fly, inverted or ditry side down...

Jack Womack

[Frunobulax]

I remember in the mid 80's flying with Dan Rutherford, aka Dirty Dan, at 60 Acres. Actually, flying "with" is a bit of a misnomer. He had his Sagitta 900 inverted and CLIMBING while the rest of us mere mortals could only watch (and descend). A truly humbling experience!

[wrinkled]

My sensor 117 will do it as well... Usually FULL DOWN or nearly FULL to keep it from a dive. You have to ahead of the plane with the rudder. Otherwise she will roll right back up...

D

[xtc]

Just curious why you'd want to fly it inverted?

its been suggested as a ;get down NOW trick to get down from boomer thermals so i thought i would try this before the day comes when i may need to

i think i may try changing my rudder over the winter because i do have the original counterbalanced rudder also

thanks guys ,

xtc

[histarter]

Well, it is indeed very possible to fly the Sagitta inverted for as long as you like. In a large, strong, and smooth thermal, you can even gain altitude while circling inverted.

There are two tricks to it:

1) The first is as M. Drela has just stated, be on top of every little wiggle, and correct them immediately with small control movements. The worst action is to start overcontrolling the glider, sending it into wild oscillations.

2) The second is to fly faster (about 10 mph faster) than the stall speed. Mushing around inverted is a sure way to end your inverted flight. (I have a feeling you may be flying the Sagitta a touch too slowly inverted, necessitating "A ton of control input")

Good luck...break a wing!
Great advice. I tend to fly fast inverted (like racing home from far off), so it is not as critical. Doing an inverted spiral I find GLs simple just wack the stick to a corner and it will flip around continuously! Paragons, Legionairs, Mirage, Vikings, and Olys (larger machines) I can trim set the rudder for a large spiral, and just let her wind on down. :D

[BMatthews]

I've only flown my thermal planes upside down a few times but while it was do-able I found that I needed to have a good sight of it to see each little attempt to roll back upright. To try to use it as a get down from speck height method seems near impossible as the model's image at that distance is just way to small to see the subtle things that need to be seen to hold it inverted.

[Arecer]

Just a thought...maybe the problem is perception.

When you are flying inverted, rudder is perceptually reversed just like elevator. So to turn right flying straight away from yourself, you need to push left rudder. If you push right rudder expecting to turn right, you will just roll upright instead.

[flystoolow]

When you are flying inverted......to turn right.......you need to push left rudder.


(Elevator is reversed, but not rudder.....right rudder is still used for a right turn)

[Arecer]

Do this experiment:

Place a rudder/elevator type sailplane and the floor in front of you with the nose pointing away from you (as the plane would be if it were flying straight away from you). Now, push right rudder and note the the nose will go to your right thus initiating a right turn from this perspective.

Now turn the plane upside down with the nose pointing away form you. Push right rudder again...note that now the nose of the plane will turn to your left!

This was my point about perception of rudder being reversed.

[Norm Furutani]

Arecer-

I understand what you are saying, and in theory it seems the rudder should be reversed, BUT in practice, with a poly wing, I agree with Flystoolow. Right turn stays right! Try it!

- Norm

[Arecer]

Norm,
Point taken...sometimes our flying machines have a mind of their own (or so it would seem). The Top Flite Contender (a .60 powered low wing airplane) will exhibit this opposite response to rudder in upright flight. If you dive and get up some speed, pull the nose up slightly, and then apply full right rudder, it will roll to the left!

Interesting dicussion...when flying a poly wing inverted you create an aircraft with a low wing, exaggerated anhedral, a very high center of gravity, and a negative lifting airfoil that must be flown simultaneously fast and at a high angle of attack. Now why would an aircraft like that exhibit any odd control response? :eek:

[histarter]

Norm,
Point taken...sometimes our flying machines have a mind of their own (or so it would seem). The Top Flite Contender (a .60 powered low wing airplane) will exhibit this opposite response to rudder in upright flight. If you dive and get up some speed, pull the nose up slightly, and then apply full right rudder, it will roll to the left!

Interesting dicussion...when flying a poly wing inverted you create an aircraft with a low wing, exaggerated anhedral, a very high center of gravity, and a negative lifting airfoil that must be flown simultaneously fast and at a high angle of attack. Now why would an aircraft like that exhibit any odd control response? :eek:
It is easier to do then think about it.
Although I appeared to be (spitefully) thermalling inverted when in strong lift, I was really flying fast controlled open turns - with a small bit of resistance on the part of the model, just not enough that would interfere with the average pilot. Yes, my 20-15 vision at the time helped. :D

[fly1milehi]

Part of the whole picture here is that an inverted polyhedral rudder/elevator glider uses the rudder to not only control yaw but also to create roll. Once the wings roll to the right adding up elevator (or down input on the Tx when inverted) will in essence create a right hand turn....??? right! LOL

[flystoolow]

Elevator is reversed, but not rudder.....right rudder is still used for a right turn.


Here is a reasonable explanation, based on the fact that no matter what attitude the Sagitta finds itself it, a right rudder control input will always induce a roll to the right:

1) When flying upright, a right rudder input induces a clockwise roll....add up elevator, and the glider turns right.

2) When flying inverted, a right rudder input still induces a clockwise roll, so, add a little down elevator, and the glider turns right.

If anyone is still confused, just turn around, bend down, and look through your legs next time you're flying inverted :D :D :D

[kostuk]

I can fly my Mirage inverted and it has only half an elevator. The wing tips are light and AUW is 31 oz. I do have to add rudder input but I'm surprized how well it does.
Ray

[Arecer]

Don't panic!...you will not have to wrap your head with duct tape (in case your brain explodes)...put down that bottle of Extra Strength Tylenol...flystoolow has nailed the answer!

Right rudder will speed up the left wing and slow down the right wing of an RES poly wing sailplane thus inducing a roll to the right (clockwise) whether the plane is upright or inverted.

Ahhh...now isn't your brain starting to feel better now!

[Peytr]

Right turn stays right!

This thread once started with the question how to keep an RE-glider on its back. The answer is simple: By flying it as if nothing ever changed.

With your first attempts (at safe altitude) try keeping overspeed and practice. In a short while you'll be flying inverted without any problem. At least when your brain doesn't interfere too much, that is. Now, as we all now there's only one remedy against an overactive brain and that's flying time.

(remember the impossible rudder inversion when flying towards yourself?)

[ZAPPA FAN]

which side of my mouth should i hold my tongue?

[schrederman]

which side of my mouth should i hold my tongue?

The inside... we don't want to look at that thang! :eek:

[nuevo]

which side of my mouth should i hold my tongue?

Hey ZAPPA FAN,

Welcome to rcgroups.

Now, how about you get your own avatar that is unique to you? Mine was made by my son and I, and took a lot of hours. I take a lot of pride in it. While I can't make you "play nice", I would appreciate it.

[Arecer]

Sorry for taking this thread off topic and into the silly zone earlier. Guess it is obvious that I allowed flying aerobatic airplanes to corrupt my reasoning when it comes to the aerodynamics of RES poly wing sailplanes. Anyway, seems we still need to address xtc’s original question.

If memory serves me correct, the Sagitta 900 had a flatter wing and shorter tail moment than many of the other RES sailplanes of its day and certainly more so than most of the modern RES designs.

As has been accurately noted, by the guys that really know, rudder on these RES birds is really a “spin” control rather than a pure “yaw” control (Thus answering the question about why right stays right).

I am curious about two things:

1) Would it be reasonable to conclude that the longer the tail moment, the more effective the rudder control would be? If this is true, then wouldn’t an RES sailplane with a longer tail moment be easier to control when inverted? What if everyone measures the distance from their sailplane’s center of gravity to the rudder hinge line and posts this along with the distance from the center of gravity to the tip of one wing.

2) Would it be reasonable to conclude that the greater the polyhedral, the more effective the rudder will act as a “spin” control rather than just purely a yaw control? If this is true, then wouldn’t an RES sailplane with a greater amount of polyhedral be easier to control when inverted? What if everyone measures the amount of polyhedral they have and post that as well. Also note the ease with which you think this particular sailplane will fly inverted.

Now…I realize that if you take any one design aspect to the extreme, it would result in a very ridiculous and undesirable aircraft. I also realize that skill plays a major role in the performance of any design. But, do these numbers taken from proven designs give us some insight into xtc’s difficulty with his Sagitta?

[xtc]

Hey ZAPPA FAN,

Welcome to rcgroups.

Now, how about you get your own avatar that is unique to you? Mine was made by my son and I, and took a lot of hours. I take a lot of pride in it. While I can't make you "play nice", I would appreciate it.

Thanks,

Jon

looks like he`s trying to get down but the thermals to strong ;) maybe he should flip it on its back


xtc

[Arecer]

After a bitter cold day Friday, the temperatures here started to warm yesterday and today got down right nice! Good excuse to go flying and try out some things to see if this old dog could learn a few new tricks.

The two planes I picked for today were my ION from Hobby Lobby and my Reichert RAPID from NSP. Both have AXI motors in them (I know, I know, this is not really soaring…but I look at it this way, the planes are “self winching.”

The ION has a straight wing with only ¾” of dihedral under each wing tip; while the RAPID has a polyhedral wing with 4 ½” under each wing tip. The ratio of CG to tail/CG to wing tip is the same. Both of these planes have ailerons and rudder (I modified the fin on the ION to make a rudder when I built it last year).

Flying the RAPID inverted using only rudder for directional control was very easy with the plane banking right with right rudder and left with left rudder. It amazed me how much the rudder mimicked aileron function and how easily I could steer around the sky with just the rudder.

Flying the ION inverted using only rudder for directional control proved to be interesting. Sometimes it would just continue on in the same direction of flight but skidding slightly. Sometimes, it would do a very flat left turn with right rudder and a very flat right turn with left rudder. All of this seemed to depend on how I attempted to enter a turn in relation to the wind direction. The most interesting part was if I let the nose drop so as to pick up more speed, it would slowly and sluggishly skid and then bank right with right rudder and skid and then bank left with left rudder.

I would never have tried any of this if not for this forum, thanks for making me think guys! BTW - flying was great today, hope some of you got a little stick time too.

[Joe Minton]

Whoops -- I was responding to #15 and hadn't even gone to page two :o I guess I'd better go get that morning cup of coffee :D

Arecer:

Nope -- that ain't right. A plane with dihedral turns in the same direction in response to the same rudder input whether it is inverted or upright. Right stick rolls the plane to the right and left to the left. When inverted the model's yaw response to rudder input is also reversed. Think about it and you'll see ---

You may 'think' you're using reversed rudder stick input when you fly an RES ship inverted but you're not. It is a sign of your skill level if you do think so. An experienced pilot, like yourself, tends to watch the airplane and doesn't think too much about what he has to do with his fingers to make something happen; he just does it. He may be completely unaware that he is making the same stick movement to initiate a right or left turn when the ship is inverted as he must when it is upright.

How many of us know that one must turn the handlebar of a bicycle or motorcycle to the left in order to go right? We just do it. This reverse input requirement is the main reason new riders are so wobbly.

Joe

[Arecer]

Joe,
I spent the 1980's flying an Olympic II (twins actually) set up strictly stock. I have to admit that I never tried flying them inverted. My problem was thinking about straight wing aerobatic airplanes instead of poly wing sailplanes. You and the others are absolutely right about the control inputs on the Poly wing RES birds. I went out yesterday to prove it to myself.

Since the early 1990's, I have gotten off into mostly straight wing sailplanes with aerobatic potential. Specking them out in a thermal is fun too! As I found out yesterday, rudder on a flat straight wing bird versus rudder on a poly wing works very different. Somehow I should have known this, but maybe this whole discussion will help someone else to better understand how our toys work!

For some strange reason, I have this burning desire to buy a new Olympic and revisit those glory days of RES flying. Brings back the memory of one crisp morning on our mountain field when I hand launched my Oly II and got a twenty minute flight scratching for lift in a series of weak early morning thermals.

[bobby legue]

Arecer,
You will without a doubt like the new and improved Oly ll. Much stronger than the original and quick to build. Still very relaxing to fly and you dont have to change the poly angle to get it to turn.
My thoughts,
Bob

[Arecer]

Thanks Bob!

Maybe an Oly III to go with it too :D

I flew my Oly II's with Ace Bantam Midget servos and an ACE Silver Seven Radio that I built. Got to the point where I could turn out those servos pretty quick! Ahh, the good 'ol days.