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Old Mar 26, 2012, 05:31 AM
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Elevator Up or Level During Take Off?

When hand launching an rc plane (easystar), is it better to have the elevator slightly up to give the plane some lift, or is it better to have the elevator flush at initial take off and give up lift only after observing the direction of the plane?
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Old Mar 26, 2012, 06:08 AM
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eflightray's Avatar
South Wales U.K.
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It basically depends on the plane, and the launch method.

It doesn't normally hurt to have a little up trim on if you are doing a hand launch a plane that feels a little under powered, or a bit over weight.

Some planes with high lift wings even benefit from launching with less than full throttle. Otherwise they tend to stick their nose up too high and could power stall. Many trainer are more likely to start to drop slightly after a hand launch, so a little up trim, (couple of clicks), may help.

There are no general rules or recommendations, there are just too many factors to take into account as each type of model, and even a different power system in the same model type, can make them handle different. Even the CG location can make a difference.

For a hand launch, a nice straight, slightly nose up, 'push' is usually better than a hard throw.

For a ground take-off, again it can depend on the type of undercarriage, trike, tail dragger, power, ground surface etc.
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Old Mar 26, 2012, 06:30 AM
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Threshold's Avatar
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With most of my hand launch planes I put a little up elevator on a switch for the launch. The Easystar is a plane I would do that with.
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Old Mar 26, 2012, 06:48 AM
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Perth, Western Australia
Joined Sep 2004
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Unless its a real slow flyer, like a 3D foamy, I always launch with a bit of up elevator. On some of my heavier planes its the only way to avoid mowing the grass. The mistake a lot of novices (and untrained helpers) make is to throw too steeply upwards.
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Old Mar 26, 2012, 12:34 PM
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Canada, NS, Truro
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Quote:
Originally Posted by easystarfpv4 View Post
When hand launching an rc plane (easystar), is it better to have the elevator slightly up to give the plane some lift, or is it better to have the elevator flush at initial take off and give up lift only after observing the direction of the plane?
This doesn't answer your question but may help you get things straight. Up elevator does not give lift in fact the opposite. It destroys lift on the tail thus helping to point the nose upwards which causes the plane to climb if it has sufficient power and airspeed. The same with ailerons, if the left aileron goes up, the left wing falls, etc.
Charles.
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Old Mar 26, 2012, 02:04 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
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Originally Posted by mobird View Post
This doesn't answer your question but may help you get things straight. Up elevator does not give lift in fact the opposite. It destroys lift on the tail thus helping to point the nose upwards which causes the plane to climb if it has sufficient power and airspeed. The same with ailerons, if the left aileron goes up, the left wing falls, etc.
Charles.
Very true, and there are probably many beginners, (and a few others), who do not grasp what happens when a control surface moves.

Take a tail dragger taking-off. If you hold some up elevator for too long the tail will try to stay on the ground, (trying to move down).
This also means the wing incidence is now much more positive than when actually flying.
That extra incidence could try to lift the model off too early and too near the stall speed.
The result can be it pops off the floor, the wing stalls, the model generally cartwheels off to one side, sheding bits as it goes.
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Old Mar 26, 2012, 09:49 PM
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United States, CA, Bear Valley Springs
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Control surface in any position besides neutral = drag.

mw
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Old Mar 26, 2012, 10:21 PM
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Des Moines IA
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Quote:
Originally Posted by easystarfpv4 View Post
When hand launching an rc plane (easystar), is better to have the elevator flush at initial take off and give up lift only after observing the direction of the plane?
There ya go.
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Old Mar 26, 2012, 10:32 PM
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Its not needed and only gets you closer to a stall at ground level.

My EasyStar will glide for 100' from a hand launch with no up elevator.

Plenty of time to get the hand back on the controller and bring up the power.
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Old Mar 26, 2012, 10:47 PM
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Quote:
Originally Posted by eflightray View Post
.......This also means the wing incidence is now much more positive than when actually flying.
That extra incidence could try to lift the model off too early and too near the stall speed.......
Not saying your wrong but this is not exclusively true,depends on the aircraft. Standard take off proceedure for a B-17 is a three wheel take off for instance. Most light aircraft would however fit this condition.
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Old Mar 27, 2012, 01:37 AM
222 km/hr Parkjet flyer
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Quote:
Originally Posted by Mark Wood View Post
Control surface in any position besides neutral = drag.

mw
at last !!

I always refer back to old C/L days when the guy would launch the model straight and level or even with a slight down angle ... me on other end of lins would not give any UP until the model was near ground or obviously flying.

Today when people launch my models or I launch myself - I tell myself ... NO NO NO wait wait wait ... before touching UP ...

All my models except the Parkjet .... that's EDF, Cessna, Ultimate etc. all dip slightly on launch, steady and then I EASE them up .... not bootfulls as you see some do and then they wonder why the model flips over and does the cartwheel impression.

I don't agree with a few clicks of UP unless the model is really well powered ... as the quote says .... = drag.

I know my first comment about slight down is horrifying to many - but believe me it can make all the difference as you are now not fighting Gravity !

So in answer to OP .... I do not use up elevator on launch until I have to in hand launch. On ROG (wheeled take-off) it depends on whether a tail-dragger or trike set-up.

Tail dragger - usually a touch of right rudder and a measure of UP to keep tail down initially for steering ... once she's rolling and I ease throttle up as she rolls ... take elevator / rudder of so tail can rise ... she takes of by herself literally ... With a trike ... its roll and ease in the UP to lift off.
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Old Mar 27, 2012, 03:31 AM
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On my tail draggers up elevator is needed to keep from nosing over in the grass, but i quickly go neutral as soon as the wheels lift off.
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Old Mar 27, 2012, 03:33 AM
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Letchworth, Great Britain (UK)
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For me, a slightly downward hand-launch with neutral elevator. The downward launch helps the model pick up speed and, when it's up to speed, I can then start controlling its flight.
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Old Mar 27, 2012, 03:41 AM
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Well I have to disagree with many posters here. When you hand launch especially when there is no wind you cannot get the model up to flying speed so with a neutral trim the model makes a dive for the ground. If you trim the plane for slow speed with some up elevator (say half throttle trim) you can launch level and have the plane cruise off with no dip and start climbing gently in a stable condition. Many of my planes do this and I can simply watch them making a steady climb without having to make a grab for the elevator stick. Many of my planes don't need any input at all after a hand launch.

Even full size planes before you take off you apply up trim. Then at cruise you take out the up trim.
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Old Mar 27, 2012, 05:11 AM
222 km/hr Parkjet flyer
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Latvia, Ventspils pilsēta, Ventspils
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Quote:
Originally Posted by Threshold View Post
Well I have to disagree with many posters here. When you hand launch especially when there is no wind you cannot get the model up to flying speed so with a neutral trim the model makes a dive for the ground. If you trim the plane for slow speed with some up elevator (say half throttle trim) you can launch level and have the plane cruise off with no dip and start climbing gently in a stable condition. Many of my planes do this and I can simply watch them making a steady climb without having to make a grab for the elevator stick. Many of my planes don't need any input at all after a hand launch.

Even full size planes before you take off you apply up trim. Then at cruise you take out the up trim.
I know what you're saying ... but if you read it as non-author - it actually says a plane without flying speed needs up elevator to cruise away gently !!

For me as say - I go back to C/L days and unless you have a well powered in fact over-powered machine - you needed a level or slight down launch with hands of to get that flying speed .. a model unless grossly overweight will get that speed in just a few feet ...

Reason model dips as you say is because its not at flying speed ... has insufficient airflow over wings to lift and is therefore a dead duck unless it speeds up ... giving it up elevator can in many cases aid the purchase of a new bottle of CA !!

Only model that I can think of in my stable that I would dare give up on launch from hand - is my parkjet - but thats pushing out over 500watts on a 500gr machine ... and is so grossly overpowered it's a beast.

My Cessna 182 without any flaps etc. will float away on a hand launch giving plenty time to get to sticks. My EDF T45 will dip as it goes of from hand but quickly picks up speed ... without input .. I can basically let her dip, then ease her up. If I tried to give UP and force her to stay up .. I think I'd be in for CA again !!
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