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Old Nov 24, 2012, 10:11 AM
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Windsor, Canada, near Detroit
Joined Jul 2007
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Discussion
spoilers: what do you get?

1.-if anything has been posted about spoilers, please bring links.
2.-whoever is using them, or has used them, please tell us what happens when you deploy them.
3.-their size (or % of wing area), location regarding the % of the chord and the span, how many degrees they turn, if above or below or both, anything.
4.- the way any1 builds them.
5.-if there is another forum or thread that could be more suitable to learn about them.

am beginning to experiment with them, and finding interesting things, hence trying to meet fellows who have something to contribute.
thanks.
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Old Nov 24, 2012, 01:13 PM
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Joined May 2005
241 Posts
Skybench spoiler page

This page gives some helpful installation details.
It is just one way of doing it though. There are many details on RCG.
Use Advanced search for spoiler in the titles only.


http://www.skybench.com/spoilers.html
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Old Nov 24, 2012, 01:36 PM
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Windsor, Canada, near Detroit
Joined Jul 2007
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no-go

Quote:
Originally Posted by Alard View Post
This page gives some helpful installation details.
It is just one way of doing it though. There are many details on RCG.
Use Advanced search for spoiler in the titles only.


http://www.skybench.com/spoilers.html
thank you.
but the link does not work, and the advanced search sends me back here.
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Old Nov 24, 2012, 05:00 PM
If it flies - I want one!
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Werribee, Victoria, Australia
Joined Jul 2008
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Spoilers - what happens?

Phil,
The link works fine here.
To address some of your issues:
What happens? When conventional 'letterbox' spoilers are deployed the sailplane typically pitches nose-down - how much depends on where the spoilers are placed relative to the tail, what sort of tail design is used, how big the spoilers are, and possibly other factors.
The nose-down pitch is handled by holding some up-elevator on a simple radio, or by mixing some up elevator with spoiler deployment on a modern computer radio.
The spoilers increase drag, thus steepening the glide path for an easier approach to restricted areas.
They also destroy much of the lift generated by that portion of the wing affected by them, and this raises the stall speed.
Location? Conventional wisdom says just outside the span of the tailplane, but some designs use a central, one-piece spoiler for simplicity and it seems to work fine.
Above and/or below? Most commonly on top only (in models); I have modified one electric soarer to have them below only, and they work fine (but with pitch-up instead of down).
Size? Typically three or four rib bays on each side?
Width? Typically 30 to 50 mm, depending on aircraft size?
Structure? From a piece of trailing edge balsa stock to ply or carbon fibre - hinged at the front edge, usually on the mainspar or just behind.
Actuation? From string pulling on horn, back to servo in the fuselage, to direct pushrod link from servos in wing, to some really elegant sliding drive arrangements (a search should really help here).
Hope that is enough to get you started.
Cheers,
PeteM
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Old Nov 24, 2012, 05:17 PM
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United States, MA, Waltham
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On the older Ava, the single spoiler caused a LOT of pitch down. I split them in three parts, used the outer two, and got better results. If the pitch down isn't too severe, I may not bother with the radio mix.

I like to use a torque rod to retract the spoilers
http://www.rcgroups.com/forums/showt...7#post10917820
description of the non-linkage and stop screws I like to use:
http://www.rcgroups.com/forums/showt...2#post17914870
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Old Nov 24, 2012, 07:02 PM
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On my Aquila , I get a slight nose down effect . I hold off on deploying untill I turn final . That leaves any weirdness out of downwind or base left turns . Just my preference ,but normally sticks the landing nicely.
The deal here is to leave them deployed untill you're on the ground , work the elevator , keep it simple .
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Old Nov 24, 2012, 08:28 PM
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On my crimson it pitches down a reasonable amount.I could mix in elevator, but I just hold in a little up elevator.It is completely controllable.
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Old Nov 24, 2012, 08:29 PM
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Suggest deploying spoilers half way, so you can adjust if you are ending up too high or too low (aka too long and too short).

It's my understanding that if you move the spoilers back a bit, you get less pitch response but you need to make them a bit larger. The boundary layer gets thicker as you move back, so it seems possible that well fitted spoilers will have much less drag when mounted further back. However, you can only go so far back and still be legal for RES.
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Old Nov 24, 2012, 11:42 PM
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post 4

Petem: thank you for the detailed answers and suggestions. it sure answers all my questions.
and now that i tried it again, the link works! mysteries of electronics.

my plane sinks deep if i just flip the spoilers instantly. maybe they are too large-therefore too effective? they go 90 degrees. as lincoln says, maybe reducing the total angle to fit my needs.
see my blog for pics of the plane to give a better idea of where they are located.

and all you guys, terrific input too. thanks a zillion.
so much to learn!
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Old Nov 25, 2012, 12:43 AM
If it flies - I want one!
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Werribee, Victoria, Australia
Joined Jul 2008
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Spoiler effectiveness

Phil,
Nice looking soarer; should go very nicely!
If you have a modern radio, I would avoid decreasing your spoiler throw or effectiveness - you can sometimes use all the help you can get coming down from strong lift. Lincoln's half-spoiler for a planned approach is a sound suggestion to give you options on finals.
Mix throttle to elevator (if you are using throttle stick to drive the spoilers) at around 10% up for starters, and adjust as needed till the aircraft just pitches gently down into the approach attitude without changing airspeed.
For interest, my old Sagitta XC would pitch down so strongly that it needed nearly all the up elevator to hold it on approach. The remaining little bit was just/almost enough for the flare if you timed it just right, otherwise all 5kg of her would arrive with a thump and a cloud of dust!
Cheers,
Pete
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Old Nov 25, 2012, 05:07 AM
Skye Malcolm
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Upper Arlington, OH
Joined Mar 2009
644 Posts
It sounds like you're working this out on your own. So I'm wondering if you use the Left Stick (conventionally the throttle stick for power planes) to control spoilers? You mention a switch, when would not be that common a way to set up a rudder-elevator-spoiler sailplane. If you use a stick then you have the ability to progressively add in or take a away spoilers (moderation can be a good thing).

If you have a flap to elevator mix in your radio set up the spoilers in the radio as flaps and add in elevator compensation. Or maybe set this up as a throttle to elevator compensation if that's the only thing available on your radio. The amount should be worked out through testing. You should do the testing with the plane high up so you have plenty of altitude to close the spoilers. As you already know you need to apply up elevator to compensate for the nose-down/speeding up you see.

The reason: You're killing the lift on a lot of the wing with many spoiler setups so you should expect the remaining wing to need to fly quite a bit faster to make up enough lift to keep the plane flying.
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Last edited by skye8070; Nov 25, 2012 at 05:29 AM. Reason: added throttle to elevator comment
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Old Nov 25, 2012, 05:13 AM
Skye Malcolm
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Upper Arlington, OH
Joined Mar 2009
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PS - There is a sailplane club across the river from you up near Romeo, Michigan called the Greater Detroit Hiking and Soaring Society. Their website is http://gdshs.org/ and if you had the luxury of travelling across the border and meeting up and flying with them I'm certain you'd reap the benefits. Not just of spoiler setups but all things related to building, setting up and flying sailplanes. This is one of the longest running AMA clubs dedicated to sailplanes and there are great bunch of fellows up there.

-Skye
Columbus, Ohio
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Old Nov 25, 2012, 05:27 AM
Skye Malcolm
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Upper Arlington, OH
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Quote:
Originally Posted by jetmaven View Post
On my Aquila , I get a slight nose down effect . I hold off on deploying untill I turn final . That leaves any weirdness out of downwind or base left turns . Just my preference ,but normally sticks the landing nicely.
The deal here is to leave them deployed untill you're on the ground , work the elevator , keep it simple .
I fly a composite-winged rudder-elevator-spoiler plane which turns slowly to begin with because of the inertia of the wings. However, when deploy the spoilers this slowness to turn increases, especially with the spoilers fully-deflected. They might be washing out the rudder somewhat, or it might be something else going on, but I too agree with jetmaven's advice. In fact for rudder elevator (no aileron or flaps) planes when we fly in competition and are trying to hit a precise landing spot the best advice is to line these planes up with a longer final leg and do very little turning and using the spoilers to control the glide path. It's best to orient the plane so it compensates for any cross wind and just comes right into your landing spot with the wings level for the last 10 seconds or so. Any turns with these planes ends up wobbling the plane and dipping a wing. And you don't want to catch a wing tip as you land if you're trying to bring a plane down and have the nose come to rest exactly where you want it. Again, I'm not sure if you've seen a sailplane contest but the goal is to get the nose within 1 to 3 inches of a spot in order to garner the most landing points (depending on the typical task).
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Old Nov 25, 2012, 07:00 AM
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Windsor, Canada, near Detroit
Joined Jul 2007
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details

1st of all, many thanks to all you guys! seems that am getting help from the major leagues fliers all over the place. wonders of the internet.
i better provide details of my radios:
1.-am using a dx6i in this plane.
2.- also have 1 turnigy 9x stock, and another with the smartie module installed (er9x), but have not been able to deal with both of them yet due to this designing/building spree. this means that with the 9x i could do anything needed (once i learn how to do it). but not so far.
i hope this provides the necessary background for you to figure out where am standing.
and am using a motor, so the left stick is busy with the throttle.
but seems that i still have to add something: on the dx6i am using the gear switch for spoilers, and the flaps switch for flaps, as the plane also has flaps-but not the conventional type: am trying split flaps-just like the dc3-on the bottom only, behind the spoilers (see pic on my blog).
now, to answer all the great posts.
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Last edited by phil alvirez; Nov 25, 2012 at 07:25 AM.
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Old Nov 25, 2012, 07:13 AM
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Windsor, Canada, near Detroit
Joined Jul 2007
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Quote:
Originally Posted by Petem View Post
Phil,
Nice looking soarer; should go very nicely!
If you have a modern radio, I would avoid decreasing your spoiler throw or effectiveness - you can sometimes use all the help you can get coming down from strong lift. Lincoln's half-spoiler for a planned approach is a sound suggestion to give you options on finals.
Mix throttle to elevator (if you are using throttle stick to drive the spoilers) at around 10% up for starters, and adjust as needed till the aircraft just pitches gently down into the approach attitude without changing airspeed.
For interest, my old Sagitta XC would pitch down so strongly that it needed nearly all the up elevator to hold it on approach. The remaining little bit was just/almost enough for the flare if you timed it just right, otherwise all 5kg of her would arrive with a thump and a cloud of dust!
Cheers,
Pete
thanks for your kind comments. the plane has been performing well, and i hope somehow i will be able to try all the things i need when the weather allows (i live in windsor, also called 'the city of winds-or storms').
the radio am using with this plane is the dx6i, that has its own limitations, as am learning, and am using the throttle for motor control, but i will try your suggestions, if i learn how to do it-and the radio allows for it. and, as i have a turnigy 9x that has more room for these ideas, i just need to learn to use it for that.
seems that the name of the game is a radio that can do all of this, and learning how to program it, so here i come. just give me some time to learn what it takes.
and seems that i need to give my plane lots of 'up' to compensate for the strong spoilers (sinking) effect.
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Last edited by phil alvirez; Nov 25, 2012 at 07:26 AM.
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