How do you trim a glider?

[Nev Haycox]

Being new to gliding has got me wondering. To trim for yaw and roll is pretty obvious but what’s the best way to trim for pitch. With a powered plane I set the throttle between half and two thirds in level flight and trim, but how do you do it with a glider? I’m thinking too much up and it will keep stalling too little and you lose unnecessary height, so is it trial and error or is there a particular way!

I do hope this isn't an idiots question

Thanks in advance,

Nev.

[Greybeard]

Trial and error for me.

[Phil Cooke]

Nev,

Are you talking slope soaring? Or flat field gliding (aerotow or winch)

On the slope, in practice, the elevator trim is altered specifically to suit the conditions on the day.

You are looking for level flight with a neutral elevator stick, but on windy days when the lift is 'booming' you will need to add more down trim than usual to enable penetration. When the wind is less than ideal, you may need a touch of up trim, but remember you are still only after level flight, you do not want it ballooning, so if the lift is insufficient, correctly trimmed it will sink down, but with its nose level! Remember that the elevator is actually controlling the speed, not the height.

On the flat field you are after a similar pitch such that the model neither balloons and stalls, nor dives and accelerates when the elevator is neutral.

Each day is different with gliding, you tend to launch, control immediately with the sticks then trim accordingly all in the first few seconds of any flight (and often many times during it if the conditions are variable)

Edited By Phil Cooke on 27/05/2013 17:17:35

[Nev Haycox]

Sorry Phil, I have just maidened my Phoenix 2000 which is a powered glider. I will be flying it mainly (at the moment) at the club field.

Cheers, Nev.

[Chris Bott - Moderator]

Nev I set mine up for the glide, then deal with what it does during the powered climb manually. If it's far off doing a steardy climb, then some mix from throttle to elevator can help.

Since I've had the DX8 glider software, I've moved on to flight modes, and have enabled different trims for each mode. So I can tim in climb mode, and separately trim in glide mode. (and again in landing mode)

[Nev Haycox]

Hi Chris, I have a DX8 and have recently added the glider software. I'm still learning what the tx can do, as for gliding software, well

I have the glider on the plane software at the moment but will look to change over just as soon as I can get my head round all this mixing business,

I have fitted flap servos so I'm hoping to get out again soon as I hadn't dialed in enough down elevator for the maiden so the landind was a bit of a rollercoaster

[Chris Bott - Moderator]

Send me a PM with your email address and I'll send you my P2K transmitter set up.

It may not be the best way to do it, I'm beginning to learn that glider setups can be many and varied, and very different for different pilots.

Mine does the following:-

Launch/Aero mode - Motor on throttle stick, full span ailerons (flaps as ailerons) and snap flap (down flap at extreme up elevator for tight turns/loops.

Landing mode - Proportional crow braking on throttle stick. (flaps down/ailerons up)

Gliding mode - Full span proportional camber change on the knob. All down increases lift and slows things down, all up adds speed and reduces drag to penetrate wind or get out of drag.

The only downside really, is that you have to go back to launch mode to use the motor. However I seem to now prefer landing in pure glider mode, with the challenge of trying to put it down on a spot.

[Nev Haycox]

I have just PM you Chris,

Cheers for that.

[Sandy Colquhoun]

RS I`m sure you`ll get all the advice you need here, and you do seem to have a pretty fancy radio to do magic tricks with, however I`ll put in my tuppenceworth as there will be others interested in the same subject. I have been known to programme in the bells and whistles, but now I just fly the things using the sticks with a bit of expo.

Most electric gliders I`ve tried tend to point their nose up under power, and I have in the past put in a mix of slight down elevator as slave to full throttle. Now I find it just as easy to apply a little right stick forward while the throttle is wide open, and trim only for the glide. Basically that`s just adding up trim till the model starts to porpoise a little, then take off a couple of clicks.

Then the real work starts to find the best trim for different conditions, because you`ll find that the slowest glide trim isn`t necessarily the same as for the least rate of descent.

You may find the Phoenix doesn`t really need any fancy mixing for aerobatics, though a small amount of spoileron often helps to get you down on the chosen spot.

Gliding can be as complicated as you want to make it, or not, as you wish, but the more you do it the easier it gets to "read the air" and that`s when the real fun begins.

Best of luck

[Frank Skilbeck]

One thing you need to do with a glider is adjust the c of g so the elevator trim isn't speed sensitive. Basically at height put the glider in a 45 degree dive and neutralise the elevator, if it climbs quickly it's too nose heavy, so move the c of g back, retrim and do the dive test again, when the glider only does a very shallow climb out then the c of g is about spot on. If on the dive test it has a tendency to tuck under then the c of g is too far back.

[Nev Haycox]

Thanks to all for all the advise, I have loads to work with and look forward to putting it to use.in the near future.

Regards Nev.

[Mart49]

Nev, I was out yesterday morning with my Phoenix - steady 15 mph gusting to 35 . I've trimmed her to fly straight and level into the wind with no power. Franks advice re cog is good - I've done this and find that using either a 1550 or 1800 lipo (both the same weight) towards the rear of the ply battery tray is about right. Yesterdays problem was not so much the flying (managed to fly inverted across the field, finishing with an inverted loop - a first for me!), but getting her down. Needed nearly 75yds approach, just 6-7 feet above the ground - with or without flaps . Best glider ever, though. Mart