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Up or Down Flaps


Harry Wilson
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Hi,

I've got myself a 2m powered glider (foam but it seems to work ) however I'm not sure how best to slow the thing down for an approach on a small field. Am I best to dial in down flaps on the flaperons or up flaps with corresponding elevator adjusments. Killing the speed is what I'm mainly after here - I think!

Its an ASW 17 if that helps and I've got an Optic 6 Tx so plenty of mixing options if I knew what I was doing.

Thought I'd ask before opting to experiment

Cheers,

Harry

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Harry,

I'm no expert, but I think that if you have seperate, inboard flaps (as well as ailerons), then they need to droop down.

However, if you're talking about using the ailerons alone to slow it down, then I'd suggest having them rise up as spoilerons. This will help prevent an tendency to tip-stall at low speeds.

tim

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I tend to use both ways depending on the type of glider.

If it's a floaty / draggy type airframe I will use up spoilerons to kill lift and act as brakes.

If it's a bit slippery I tend to use down flapperons which will slow it a bit and give more lift at slower speeds.

With both ways I tend to have aileron to rudder mixed in when the brakes are switched in, just to give a bit more directional authority and brake to elevator mixed in to compensate for any changes in pitch.

It's all a bit trial and error and as Tim says - beware of promoting tip stalls.

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The problem is an ASW17 is a pretty slippery shape so a steep descent into a small filed is always going to be a speed issue. To control the speed you need drag.

The problem is flaperons or spoilerons can only create a certain amount of drag without compromising their function as ailerons, This ultimately limits how steep your approach can be.

Remember a full size ASW17 is virtually impossible to land safely without using its air brakes and they stick out at right angles to the airflow!

The best solution for small field operation will be either true air brakes or flaps that drop to at least 70 degrees preferably with a proportional control. You will then be able to make steep, speed controlled approaches.

With just flaperons/spoilerons you either have to land faster than you would like (fly it into the ground with possible damage) or get good at low, slowish approaches (but serious consequences if you get it wrong!) or find a bigger field.

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Well I seem to have survived the first half a dozen flights but the challenges you all mentioned are very real with this model. For the money as a complete package it was pretty good value...you can't have everything. Thanks for all the informative responses. Much appreciated.

Harry

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  • 1 month later...

I have recently been looking at this (hence finding this thread). My understanding is that Flaps under-camber the wing but can leave the wing-tips effectively with wash-in which can lead to tip stalls. Spoilerons kill lift, the only problem can be that they increase the stall speed of the wing by introducing the opposite of undercamber.

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