Spoilers on a Riser

[sheephunter]

I've read the posts about modifying a Sig Riser as an aerotow trainer, and with a 100" Riser kit sitting on my shelf I decided to move forward with the build. I have a question for those who've built a Riser and modified for towing. I'm planning to flatten out the wing and use the outboard trailing edge as ailerons. My question is for those who have put spoilers on their Riser. The plans show running a cable arrangement to a servo in the fuselage. This airplane was designed many years ago when all servos were full sized. I wonder if it would work best to install the spoiler setup as shown on the plans, or now with smaller servos available, mount servo spoilers in the wing to activate them.
Any thoughts?

[Steve P]

Servo in the wing. If you are able to orient just so, you can use the arm to raise the servo and a spring to close. No actual linkage.

Good luck with your project.

[mlachow]

Since you are putting aileron servos in there, it is probably best to put spoiler servos in the wing too.

If you want a linkage for driving the spoiler, look at the linkage for the Bubble Dancer.

http://www.charlesriverrc.org/articles/bubbledancer/PDFs/wing_plan_V2b.pdf

You end up with a small U-shaped wire driving the spoiler. That is what I have on my Bubble Dancer and I also used that on a Mirage that had spoilers added. I also covered the wing under the spoilers.

Smaller RES gliders often just use a long servo arm to push the spoiler up and magnets to keep it tight when they are down.

[sheephunter]

Thanks for the responses,,,I read a post recently about the servo arm/magnet method and that's what I was planning to use.

[jswain]

while your at this stage, consider aligning the spoiler servos to be oriented exactly the same way(flat) with each other
( i.e. when viewed from underneath the wing) and you can just a "Y" harness at the wing root and
only a single output channel on receiver.
john s.

[Mark9]

The method jswain recommends can work if your radio does not have at least 7 channels that can have the channels assigned to certain functions. If your radio is like most current 7+ channel radios I would recommend that you mount the servos flat with the tops pointing to the wing tip. This will allow you assign each servo to a different channel and through mixing or a wing configuration template then have independent adjustment of servo travels and end points. Also, the servo linkages will be more easily centered on the spoiler blades. For this particular installation I would use a template that has a two servo flapped wing configuration when setting up the radio. Then assign the spoiler servos to the flap function. Using a "Y" adapter will require manual adjustments and can be quite fiddley.

[sheephunter]

Thanks for the responses; to keep it simple I was going to use the Y harness method and orient the servos appropriate to that, but I see the wisdom in mixing 2 separate channels. I'm using a Futaba 7C, not the most powerful platform for mixing but it's capable enough, and has enough channels to mix for the spoilers.

[mlachow]

It would be almost impossible to get the spoiler down and full travel matched with a y harness.

[Mark9]

As you might expect from my previous post I agree with what mlachow says. Looking at the manual for the 7C, since it appears to have no wing template that will easily work, I would highly recommend that you investigate using the "PROG.MIX" functions to set up your spoilers on two separate channels. I would set up a test on the bench to see if this may work:

1. Plug the master into the channel that is assigned to throttle. Most people have up left stick as spoilers down in gliders.
2. Plug the slave into the channel you want the other spoiler on.
3. Then use a PROG.MIX to assign the throttle as the master and the slave as the control of the other spoiler/servo.
4. Set the rate to 100%.
5. With the tops of the servos pointing to the wing tips (away from each other) you will most likely need to reverse one of the channels.

This then may allow you to control each surface down position and travel from the radio settings.