Spoilers for roll control

[flailing]

Has anyone any experience using spoilers for roll control ? How far should they deflect up ? 45 deg?

[DaveSawers]

Do you mean spoilerons? By that I mean using the same control surface for both spoilers and ailerons. If so, any diferential movement should cause roll at any spoiler deflection.

Maximum deflection for spoilers needs to be found by experiment to achieve the sink rate you want. 45 degrees is a good starting point. Test and see.

[flailing]

Only for roll control that's what I am going to try for my B-52. Maybe I should have said maximum deflection.

[Sabrejock]

The roll control on the 52 was accomplished exclusively by spoilers, which were were less and less effective as speed decreased. Flying final approach was much more successful feeding in good quantities of rudder. If you plan spoilers, be sure to make your rudder operative.

As far as how much deflection, they didn't move all that much in normal flight, on final, you're busy enough and not watching the spoilers so I can't say. Tex.:eek:

[Steve Fehr]

Spoilerons (that is, spoilers used as ailerons, not ailerons used as spoilers) were very successful in several full size planes, like you said, and were supposed to be much better than conventional ailerons at ultra-slow speeds when flaps were fully deployed. As far as model planes go, I believe the Ziroli P-61 uses scale spoilerons for control to great success. :D You might be able to track down some of the details on that to get some tips 'n tricks for your B-52.

[Sparky Paul]

Full-scale spoilers for roll control are generally programmed to deflect according to the airspeed.
Slow, lots of spoiler, or spoilers.. fast, some won't come out at all.
Structural limits are the governing factor. And you don't need a lot of spoiler (or aileron) for high speeds, unless you're a fighter like an F4.
.

But the speed ranges of full-scales are much greater than those of models, so programming your spoilers to be effective at low speeds won't be a problem at high speeds.. you'll just need less stick deflection.

[David F. Plummer]

Hi!

Have you ever resolved your question about spoilers for your B-52 model? I'm considering building a 1/16th-scale model of the Martin P6M-2 flying boat, which used spoilers for roll/bank control. I've managed to build a rough version of the RH wing, and got the spoiler installed, but am not sure what the approach is for servo control of the two spoilers (RH and LH wings): do you need a radio that has 2 separate channels, one for each spoiler, somehow part of the 'airleron control circuit/channel'? If you know of any good threads/articles on this aspect of spoiler control, I'd appreciate any suggestion/guidance. How's the B-52 coming?

RSVP when you have time.

Regards,

Dave Plummer

[Thomas B]

David, almost any computer radio will allow you to mix aileron and flaps for flaperons.

Pretend your spoilers are flaperons. Put a separate servo in each wing for the spoilers. Program them so that you get the deflection you need when the aileron stick is deflected. Program each channel so that each servo moves in one direction only and opposite each other for roll control, only when the aileron (now spoiler) stick is deflected. Plus, should you need it for a very clean P6M Seamaster model, you would have the option for deploying both spoilers at once via the "flap" (now spoiler) channel, for approach path/glide path control.

If you don't have a computer radio, you can still do a separate servo in each wing panel, hooked to a Y harness for the aileron channel. Use a pull string to activate the spoiler. That way, when you give left roll, the left servo will pull the string to raise the left spoiler and the right servo will try to "push" the string on the right spoiler and nothing will happen with the right spoiler. Get it?

Personally, I'm not a huge fan of spoiler for roll control in models. They do not work well inverted, if at all. I'm sure you will have a nice large functional rudder on your Seamaster and that flailing will also have one on his B-52. I sure would.

[David F. Plummer]

Thomas B. - Many thanks for the feedback; I'll give option 2 a try as my radio system hasn't made it into the computerized century as yet. I was tempted to omit the spoilers is the P6M-2 model, but since it's (the model) a lot of work, I wanted to stay close to the aircraft's configuration. I don't think inverted flight was in the P6M-2's capabilities/requirements, so am not worried about that; the aircraft's/model's 'T-tail' has a good rudder, so yaw control (hopefully) won't be a problem. Adding flaps to the model is going to be another major problem, but I haven't made a decision on that yet. Again, thanks for the response.

[Thomas B]

One thing I forgot to mention is that you would want to install a small, lightly tensioned rubber band to keep the spoilers closed until you call on them, just as done in many, many sailplanes over the years. Some folks also like tiny rare earth magnets to keep those pull string spoilers nicely closed.

Somewhere I saw a neat spoiler design that used submicro servos right in the spoiler bay. They were installed and the long servo arm trimmed so that the servo arm would bump them up into the airflow over the wing when the servo was sent one direction. When the servo went the other way, the arm hit nothing and moved unimpeded in the spoiler bay. That would work as well.

One of those fine English E-modelers did a nice P6M a number of years ago. Not an EDF: he installed a pair of direct drive 480 can motors in the exhaust nozzle of the outboard turbojets. The props were hardly noticeable at all. This model was featured in a report in EFI about 3 years back.

Good luck on your project: please post some pics as it comes to fruition.

[flailing]

The B-52 was a great sucess flew like a 2 meter glider and the spoilers worked great, however the last time I saw it was at about 1000' sailing off into the sunset, flew out of range I guess, still looking for it. I used Spyder wire to each spoiler with a small rubber band to hold them closed, servo moved one way pulled on one line, other way other line.

[David F. Plummer]

Hi Thomas B!

Thanks for the additional info - I had concluded that a spring-return (hadn't thought of rubber bands) would be required, but the micro-servo approach may be adaptable for my construction. I'm trying to get a mock-up put together to make sure I know it will work in my model. I'll post some pics as soon as I get a little farther along. There were some photos of a XPM6 model in EFI in the August, 2001, issue (pg 24); very nice model; however, the nacelles bear no resemblance to the real aircraft - still, it looks like it flies great, so who cares!!! I'm trying to build a model of the production version of the aircraft (P6M-2), and plan to use 4 EDFs. The nacelles are very difficult for my meagar tallents, but I'm plodding ahead anyway.

[David F. Plummer]

Hello!

Thanks to Thomas B. I've managed to get a spoiler actuation (using small servos to deflect the spoilers, and rubber bands for return/hold-down) scheme operating in my P6M-2 model. At 1/16th scale, the model's wing span is about 75 inches, with about 7.5 sq. ft. of area. Any suggestions on the maximum deflection that ought to be provided for the spoilers?

[flailing]

I had mine set up to deflect 90 deg. but in flight I only needed maybe 20 deg. or so. I had mine set up with a mixer and could deploy both during landing hence the 90 deg.