Spoileron compensation

[Doc Data]

If the weather permits, I'll fly the Nike tomorrow. I have spoilerons programmed into the left stick. I want to program in some elevator compensation but I need to know which direction. I think I remember reading that the spoilerons cause a nose up attitude (although I would think it would be nose down) and therefore will need to program in some down elevator.

Anyone know for sure. The Nike is similar to the Bandit but with a larger wingspan.

Thanks,
dd.

[Andy W]

I never dial any in in advance, just test at altitude and get the feel of it, and be prepared with a finger on the elevator.
The amount of compensation required varies so much with airspeed, and as I use mine to not only control sink rate, but also to slow the model from cruising speed on downwind, the amount of compensation would vary significantly.
..a

[Doc Data]

Sounds like a plan!
Thanks Andy.

dd.

[DaleM]

I also didn't dial any in. One of the old-timers at the field said you can never really know what you're going to have to put in for elevator when mixing in either spoilers or spoilerons. It all depends on the plane.

I happen to prefer a little down elevator when I pop spoilerons because I like the feeling of having to "pull back" on landing, rather than forcing the nose down... Some planes won't need down, and will have the tendancy of just nosing over by themselves.

[green66]

One of the old-timers at the field said you can never really know what you're going to have to put in for elevator when mixing in either spoilers or spoilerons I never dial any in in advance, just test at altitude and get the feel of it, and be prepared with a finger on the elevator. Sage advice, I discovered after retrofitting my Organic with spoilers (conventional fence-type) to assist landing at tough slope sites >>> Yeah, I'm crazy enough to slope a featherweight relatively expensive thermal duration crunchie :p (but with clean lines and thin MH32, it moves almost like a dedicated sloper :))

It had been my understanding that "down" elevator compensation was a given for spoilers. Turns out that my Organic needs 25% "up" compensation and still wants to nose down some after popping the spoilers.

I like the feeling of having to "pull back" on landing, rather than forcing the nose down Ten-Four, I concluded same ==> would rather the hands-off mode be conservative (nose-down, faster) and pull-back to bleed off speed, rather than risk stall or dropping a tip at neutral stick, then attempting a panic recovery at low altitude :eek:

[Andy W]

and, as if to make a point..

http://www.rcgroups.com/forums/showthread.php?s=&threadid=47927

:o
..a

[davidleitch]

Nevertheless to answer the original question I believe mostplanes will require down elevator compensation when spoilerons are deployed.

Doing it automatically means one less thing to worry about on landing.

Elevator override is still available.

From theory you could test the change of attitutde at typical landing speed whilst at altitude and then put in the appropriate automatic compensation afterwards for future flights.

However it may well be the first couple of flights where you need it most.

[Doc Data]

Well, I did fly it and had nothing mixed in. I'm glad as it did not look like it needed any compensation. However, application of spoilerons did not seem to have much effect as far as 'spoiling' lift either. I've got about 25 degrees... add more?

dd.

[Andy W]

Go look at the pics I just uploaded to the gallery of the spoilers in my Falcon. They go up 60 degrees..
..a

[Bill Glover]

My Virage 1.6M warmliner (Endo) also pitches nose-down with spoilerons, so needs 'up' ele compensation. But I agree with trying zero compensation first.

[DaleM]

if nothing happened when you applied them, then yes you probably need more. I think mine come up almost 50 deg or so. I take them as high as I can yet not so high that they bind when I make stick compensation.

[green66]

However, application of spoilerons did not seem to have much effect as far as 'spoiling' lift either. I'm not a big fan of spoilerons compared to fence-type pop-up spoilers, as spoilerons seem to be more for the sake of extracting additional utility from control surfaces that already exist, i.e. the ailerons, rather than for a dedicated lift-killing purpose.

Problem is, by the time the air hits the spoileron, the lift has already taken place, so the spoileron isn't really a spoiler as much as just a drag producer, whereas pop-up spoilers kill lift and create drag. Granted, pop-ups require more servos and can be a real SOB :mad: to install, but combine them with flap, and you've got rate-of-descent control second to none.

I retrofitted spoilers (pic below) into my Organic 2.5m (a hassle, and painful to perform open surgery on such a nicely-crafted RTF) because, without the spoilers, landing this lightly-loaded thermal duration plane amidst strong lift and swirling air at slope sites with no real landing area was all but impossible w/o incurring high risk of damage. Now, with the spoilers, landing in tough conditions is almost "fun" ;)

[Andy W]

green,
no to argue, but spoilerons work a little differently. What they do is effectively alter the AOA of the aileron-width span section of the wing. They drop it considerably, allowing you to fly at a very aggresive AOA without risk of tip-stall. This effectively turns the inner wing section into flaps, and you end up with crow. So, you're correct, in that they do induce tons of drag, but the alter the way the model flies. You have to get them up above 30 degrees before you notice any change in sink, 45 and up and they really work well - they can slow my Sirius down from 100mph+ to a nice 30 or 40 for final in a heartbeat..
That said, it would be nice to have real spoilers in every model, but for one with ailerons, spoilerons work quite well..
..a

[DaleM]

green66 I can definitely understand what you're saying. Unfortunately in my case I'm dealing with a foam core wing covered in obeche (sp). Plus the wing is so thin I wouldn't know where or how to install the servos for the fence type spoilers. I definitely think the fence type look cool when flared up with dropped flaps!! With outward ailerons though I was able to create at least enough drag to slow me down for much shorter landings.

Has anyone ever installed fence type spoilers in a foam core wing? Just the thought of hacking at my wing makes me ill!!

BTW, nice looking plane!

[davidleitch]

By the way Doc how did the Nike fly?

[Doc Data]

Not bad?... pretty good?... great?

I only had a few minutes flight time as we were shutting down for the day. I wanted to get in the air just so it would ready for SEFF so I have a few climbs, a few turns and a few passes accross the field. So far, so good. I'm using the Kontronik 501 system.

dd

[davidleitch]

Well I flew the Spiro again this weekend. Flaps and spoileron crow system.

Its fast by my standards. Moved the CG back making flaps more effective.

I have 40% down elevator in the mix and I'm glad I had it. Still pitched up and half stalled on landing when crow was deployed. Will program in more for the future.

Must say its hard coming in fast and low make a tight turn and then stop in a hurry. However everyone else is landing at their feet and the plane is still working.

What a great weekend.

[green66]

Andy,
Re spoilerons, makes sense, got it. My opinion of spoilerons was influenced by a previous plane (destroyed by an inconsiderate telephone pole that jumped in front of it) that had spoilerons which didn't seem very effective, but they also didn't travel above 30 deg as you suggest, so that might have been the problem. Unfortunately in my case I'm dealing with a foam core wing covered in obeche (sp). Plus the wing is so thin . . . Just the thought of hacking at my wing makes me ill!! DaleM - I hear you. It took me a while to muster the guts to chop into my built-up for retrofitting. I plan to use spoilers on sheeted foam cores in upcoming projects; might post results. I think any strength reduction can be compensated by an adequately strong spoiler frame. Fortunately, short spoilers are, IMO, better than tall - It doesn't take much spoiler height to totally disrupt the airflow. A tall spoiler won't kill more lift, and creates drag only in proportion to its height ==> but the required torque increases as the square of height. That's significant when having to use small low-torque servos (because of space limitations) for any control surface turning 90 deg to the airstream.

[DaleM]

green66 if you do get the urge to do the chopping, please post. Do they have servos that are thing enough to hide inside a wing thats like 3/4" thick at the root?? Some of these planes I've seen have REALLY thin airfoils. How are they getting servos in the wings to do spoilers?

[green66]

DaleM,
My wing is 3/4" at the thickest point. I used HS-81 servos (1.2 x 0.5 x 1.2). If not familar w/it, it's Hitec's std micro servo. There are smaller, but at lower torque. Hitec just came out with a wing servo that's 0.4" thick (HS-125 MG) http://www.hitecrcd.com/Servos/hs125.htm

The inset of the pic below shows the linkage scheme with the spoiler fully open (same model as my previous pic). Simple, but was a pain to get right. Some things to note:
1. Metal connecting rod (dark line) is at nearly a right angle to the ply spoiler horn; transfers max torque to spoiler when it counts, in the open position.
2. Spoiler horn is not at a right angle to the spoiler; it's canted forward about 45 deg so that the attachment point on the horn will end up (spoiler full open) well below the imaginary line between the attachment point on the servo arm (red) and the spoiler hinge line. If this condition isn't satisfied, the spoiler won't be able to fully open, regardless how much torque is available.
3. Clearance cut in spoiler horn - That's where the servo arm tucks under as the spoiler closes. I could have offset the arms, however wanted to avoid possible side loads and twisting.
4. A Tx with adjustable end points and throws is invaluable - makes it easy as dirt to get both spoilers hitting their close stops simultaneously, just before end of servo travel.

[DaleM]

green66, thanks for the pictures. Do you think in a foam core wing you'd just chop out enough space for the servo and connecting linkage? I'm assuming then you'd just cut the spoiler to fit the area of wood that you'd remove from the covering/wood.

eh?

[green66]

DaleM,

That's the basic idea. The spoiler should be as thin as possible, naturally, to minimize the required depth of the cutout in the wing. I used 1/8" balsa for the spoiler with some 1/4" sq stiffeners. For a foam core, where open bays don't exist to clear large stiffeners, I'd use thinner (1/16"x1/4") spruce for stiffeners.

Might consider making the cutout slightly deeper and sheet the foam internally to restore strength, although it might not be reduced much if the cutout is kept shallow and the spoiler narrow (chordwise). Depends on type of plane.

Another thing to keep in mind, if using a linkage similar to mine, is that the forward-swept control horn needs clearance in front of the spoiler hinge line when the spoiler is closed. So, for a foam wing with spar, keep the spoiler hinge line far enough behind the spar.

Another issue is how to route the servo wires. If a wiring conduit isn't already available, I'd cut a channel at some aft (>50% back) chord position, bury the wires, apply filler (HobbyLite (avail from Tower) works well for foam, very easy to sand), block-sand flush, finish.

Best way, IMO, to make precision cuts in foam? ==> Moto-Tool mounted in the Dremel #330 router attachment http://www.dremel.com/productdisplay/att_template.asp?SKU=330&Color=99CCFF The #565 Multipurpose Cutting Kit also works http://www.dremel.com/productdisplay/att_template.asp?SKU=565&Color=99CCFF Basically turns your MT into a vertical mill. The main benefit, of course, is being able to conveniently control the depth of cut. For foam, router bits aren't needed; can just use a carving bit like Dremel #115.

[Andy W]

Anyone here see my fly my Sirius @ SEFF? Particularly, the landing when I flew it for Aveox in their demo slot (after they broke their Tornado).. No compensation there, floated in at a nice attitude.. Remember, that thing has an F12 (10.5oz) and 12 2400's (25oz) in it, airframe is 15oz, add 8oz or so for radio gear, ESC and prop, and you're up to about 60oz on 440 sq" - not a real heavy loading, but if you saw it float in, you'd be surprised - looks more like a 10oz/sq' sailplane..
..a