Thread Tools
Jun 25, 2011, 09:41 PM
Jim C Patrick
jcpatrick's Avatar
Thread OP

Super-simple spoiler linkage

The sliding 'L' mechanism

Some time back there was a great thread on the “E/z Spoiler Linkage” using three EZ connectors and a steel rod. Although this uses the same principle, this linkage is simpler: two pieces of brass tube and one bent rod. One tube is attached to the servo arm, and the other to the spoiler flap. The long part of the ‘L’ slides in the servo end and the short leg rotates at the flap edge.

The first one I made took an hour; the second one took 12 minutes. I used CA instant glue (and accelerator), 1/16” ID brass tubing, 1/16” steel rod, some wrapping thread and a bit of thin fabric. Also a servo tester or controller of some sort.
  1. Fix the servo in place. Get the center of rotation (servo-arm screw) reasonably close to the spoiler hinge point.
  2. Measure and cut slider brass tube. It must clear all balsa in the rear and be approximately 1/8” short of the spoiler edge. Deburr and use #11 blade to chamfer the inside edges.
  3. Remove the servo arm and lightly tack the brass tube to it. Then wrap with thread and glue well. Don’t wrap over the hub or screw-hole!
  4. Cut the tube for the flap edge hinge; about ½” is shown, wrap once and glue on thin fabric.
  5. Measure the rod length from flap-edge when spoiler is closed to any balsa. Bend the rod there to 90°.
  6. Press the servo arm on, and mark where the slider tube is on the spoiler flap. Glue the hinge tube just inside the flap edge about ¼” from the slider tube. Make a tape of the thin fabric and glue over the tube to really secure it.
  7. Take the servo arm off, slide the long end of the bent rod into the hinge tube, then the servo-arm sliding tube onto the measured end of the rod.
  8. Press the servo-arm back on. Mark the excess steel rod, disassemble and cut it to length.
  9. Reassemble and operate. If the spoiler cannot close all the way, the slider tube may need trimming so it doesn’t bind on the bend in the rod.
  10. Screw on the servo arm.

Notes: I used cheap and dinky servos that fit vertically. Most servos will need a different mount position, but should always be set so the center of rotation is close to the spoiler hinge point. Make sure the steel rod is clean, has no burrs, and I highly recommend a dry moly or graphite lubricant.

Video of the mechanism in the video section.
Last edited by jcpatrick; Jun 26, 2011 at 01:07 AM. Reason: add diagram
Sign up now
to remove ads between posts
Jun 25, 2011, 09:48 PM
volare est vivere
ray foley's Avatar
hi there from Toledo

Hi Jim:

Very nice, super simple and effective. Well done.

ciao -rjf

ps: I notice that the servo arm is reversed in the sketches from where it is in the photo of the installation. -rjf
Last edited by ray foley; Jun 27, 2011 at 03:05 PM.
Jun 25, 2011, 09:58 PM
WINS - Winch In Nose Sailplane
jaizon's Avatar
Spoiler linkage has always been a PITA . Thanks for another way to try it. Much appreciated.
Jun 25, 2011, 10:25 PM
Registered User
ozmo01's Avatar
Nice job! Good one to file in the HOW TO file!
Last edited by ozmo01; Jun 25, 2011 at 10:26 PM. Reason: pour spelin
Jun 26, 2011, 12:58 PM
JP - I really like how you positioned the brass tube along side of the servo arm instead of on top of the arm. Also your tape idea is great. Check you PM.

Jun 26, 2011, 01:10 PM
Registered User
hornet_dave's Avatar
Make sure the servo is strong enough for the task. With that system, when aero loads are highest (spoiler fully extended) the lever arm on the servo is also the longest, which requires more torque from the servo. No prob if the servo is overkill, the spoiler is small, or both. However with a huge bubble dancer type monospoiler and small servo this would be an issue.
Jun 27, 2011, 10:16 AM
Registered User
craigrrr's Avatar

Why not make it simpler

On all my RES planes I have spoilers that are raised by servo arm directly contacting the under side of the spoiler to raise it.

I use a small common rubber band to retract.

A benefit of this is that the spoiler is under no strain (no buzzing sound) when retracted.

Sep 22, 2011, 09:24 AM

Making Split Spoilers

Recently one of our club members, TA, bought an older version of the popular Topaz RES ship. This plane was originally sold by Alberto at Hobby Club back in 2004. It's been sitting dormant for several years. This version of the Topaz came with a single long spoiler of built-up construction (carbon/balsa/Ultracoat covering). The spoiler was attached to a long carbon tube that ran the full width of the flat center section of the wing. A single servo mounted at the center drove the spoiler.

TA carefully cut the carbon tube for the two spoilers, made false ribs at the cut lines, installed two servos then found a problem trying to attach the spoiler end of the control horn. He solved this by bending a small diameter piece of music wire into a 'staple' shape. He cut away the bottom covering between the two ribs then CA'd the staple between the two ribs. He reinforced the top piece of Ultracoat with clear tape to act as a ramp for the single pushrod wire. On the servo arm he used the two EZ connectors and one set screw.

Not claiming to 'discover' this staple idea as it might have been used by someone else, TA just wanted to make his job of spoiler activation easier. The single pushrod wire is located between the staple and the taped covering. Another simple setup to a potentially difficult setup. The photos show the method.

Sep 22, 2011, 09:50 PM
Registered User
I think those are the prettiest spoilers Ive seen yet
Oct 06, 2011, 11:26 PM
Registered User
Gordysoar's Avatar

Or no linkage at all

Everyone reinvents the wheel when it comes to spoilers....but they all put the servos in the wing and use a linkage or arm of some kind to actuate the spoilers.

Micro servos make it simple and efficient.
Mount the servos to the Spoiler! That way the servo is accessible when the spoiler is opened.

No linkage is needed since the weight of the servo holds the spoiler closed.

Use an extended arm (a piece of plastic glued or screwed to a standard servo arm) to push against a plate in the spoiler bay.

Two way tape would be sufficient to hold the servos in place since there is little or no force involved and if they fall loose they'd just fall into the spoiler bay.
Latest blog entry: Check out my YouTube Channel
Oct 07, 2011, 06:12 AM
winds light to variable
Kookaburra's Avatar
Elegant solution; show us a pic or two?
Oct 07, 2011, 07:01 AM
Registered User
Gordysoar's Avatar

Servo or lead weight?

Sorry no photos of the system described, its something I did on a Super AVA and a Marauder. The only RES ship I have at the moment with spoiler is a Legionair 140 and it operates its spoilers with strings routed into the fuse to a single servo :-). But the Legionair Shuttle seen in 'bones' will use the servo on the door system

I suppose I could hack into my Supra, or Perfects to illustrate what a chunk of lead on the bottom of the spoiler door would look like but.... :-)

What happens is when building models we don't think of what the part is supposed to do, we think in terms of what it is.

In the case of spoilers we think primarily about how to open them...then close them...

Okay so it doesn't take a rocket scientist to figure out that you could put the servo on a plate in the spoiler bay with a lengthened arm to open the door, but how do we get it to close?....really?

It closes on its own, but on launch if there is nothing to help it stay closed, they get sucked open...which I'm not sure why we care since there clearly is little or no drag caused by them opening on their own...or they'd stay shut.

I suppose it gives a good feeling to know they stayed shut :-)

(Most guys simply put a couple of tiny magets in the bays to lock them down)

The problem with mounting servos into the bays is access. So mounting them with some two way tape to the back of the doors allows you to flop the door all the way over to access the servo...with no linkage, screws or what ever to deal with or to get broken. The weight of the servo keeps the doors closed so you get double value from the cost of the servo.

So why create elaborate linkages? Because its fun! Building is part of the hobby, the linkage shown in this thread is a really good one! But if you have a very active contest circuit the last thing you want are parts that can be broken or hard to access.

Attached are photos of two similar linkage systems used before I realized to do the spoiler on the door system.

The system of putting a screw through the servo worked great for about three years. The other system is from John Luetke, he's a master builder, full size jet pilot and modeler extrodinare and the first LSF5 in Texas to my knowlege.

Latest blog entry: Check out my YouTube Channel
Oct 07, 2011, 09:32 AM
Mark LSF # 3792
Gordy your Super AVA spoiler system is very similar to a drive system I used on an original design poly ship I built back in the eighties. It uses the same articulated pivot arm driven by a torque rod. When the wings slide onto the carry through the torque rod engages a square drive system operated by one servo in the fuselage. All made with materials from your local hobby vendor. Also, once set up no hassel assembly at the field no wires no strings, plus positive up and positive down! It's still working as of last month when I flew it in the TNT warm up.
Oct 07, 2011, 10:16 AM
Registered User
jcpatrick; love how you came up with something different, good job!

here's one i just put in.
i usually just shrink wrap the servo and glue in, but this one i wanted to make it easier for the customer to remove the servo if need be.

i've done spoilers a bunch of diferent ways, but i do like this one, since there are no adjustments to be made. real simple to install.

dave hauch
Oct 07, 2011, 04:04 PM
Registered User
Originally Posted by Gordysoar
Mount the servos to the Spoiler! That way the servo is accessible when the spoiler is opened.
Hey, that's a great idea. Thanks. I'll have to admit that I wonder if there isn't some flight condition when the spoiler might flutter because of the extra weight, but then your actual experience with it seems to indicate this doesn't happen.
Originally Posted by Gordysoar
It closes on its own, but on launch if there is nothing to help it stay closed, they get sucked open...which I'm not sure why we care since there clearly is little or no drag caused by them opening on their own...or they'd stay shut.

The drag doesn't have to be local to the spoiler. I don't know how far spoilers get sucked open, and I bet it depends on where the inside of the wing, or at least of the spoiler bay, vents to, but there has to be at least a small induced drag penalty since it would mess with the lift distribution. So I think magnets and a weak torque wire are still justified. And, at least for me, I'm sure there are moments of negative g's on gusty days or at some point at the start or end of a zoom.

Quick Reply

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion A little EZ spoiler linkage review chipgibbs Sailplane Talk 27 Jun 11, 2016 08:47 PM
Discussion E/z Spoiler Linkage VegasRay Sailplane Talk 51 Jun 18, 2014 11:23 PM
Discussion Super Simple Cheapo Pink Foam Beauty! ilektron Foamies (Scratchbuilt) 0 May 21, 2011 01:58 AM
Build Log Oly III spoiler linkage fgroza Thermal 15 Apr 06, 2010 01:45 PM