Split spoilers for the Ava

[ClayH]

I've heard of some folks converting their Super Ava to split spoilers to help with glide path control on landing. Has anyone tried it with an Ava? I'm considering do so to try and cut down on the turbulence going back to the tail. What do you Ava owners think?

Clay

[Ollie]

Back of the 1970's, I used a central spoiler about 36" long on a wing of 13' span. I had no problem with stab. control because of too much turbulence. Sure, the turbulence is there but it is not a problem.

On the AVA, the center spoiler is effective because it is long. Two shorter spoiler are ok but complex. I would not go to the trouble. KISS.

I go with Dr. Drela's designs but not myth about needing turbulence of the tail because spoilers split.

[Tim Wolff]

I read through the big Ava thread a week or two ago and it appears that you have to pay particular attention to ensure that there is sufficent up elevator throw available when the spoiler is raised. Like a ton of up. The spoiler "blanking" the elevator may have something to do with that. I'd be tempted to do two seperate spoilers on an Ava just to be different AND see if it made a real difference. There are a few in our club, but I can't say I've actually seen one fly and land like it was dialed-in. Saw one in paricular where the pitch control looked like it went to hell when the spoiler was raised. Looked like a giant leaf falling. Still, if they were available in transparent orange, I'd prob. already have one based on what I've read here.

[Andy W]

You need a ton of elevator because the spoiler is so huge it kills enough lift that the AVA will just drop out of the sky! :) I swear my approach is probably better than 60 degrees at full spoiler - and there's a ton of drag along with it, so it really slows it down (mine is <60oz, electric version). I have a LOT of up elevator with full spoiler - it's in the electric ava thread somewhere, but enough that I set up the mechanical linkage to allow 4 or 5 times more 'up' than down..

There's no reason to split the spoiler - there's ample control by just backing off the spoiler and with enough elevator compensation.
..a

[ClayH]

I use a six point curve for elevator compensation so I'll spend some more time making sure that it's dialed in before making any changes. I've never had a RES this big before, so I'm not used to the "rocking" back and forth it does sometimes. Much easier for me to land a full house ship.

Clay

[Tim Wolff]

The "rocking" sounds exactly like what I observed Clay. I don't know if that plane made the spot at all that day. Clouldn't have been any fun.

[IBWALT]

I love the large spoiler on my Super AVA and would not split it for anything. It not only acts as a spoiler but as a speed brake too. The recommended opening on the AVA spoiler is just shy of one inch which provides more than enough spoiler but I have mine opening up almost 90 degrees and this is enough drag to make some really rapid descents without an excessive increase in speed. Like CLAYH said, the AVA spoiler is not linear but requires a 6 point mix. Actually mine requires very little compensation up to point 4 and then massive amounts after that. If you were to try to compensate using one of the linear mixes on the Spoiler to Elev you could end with a mix that was inadequate on one end or the other. Giving you some very undesirable flight scholastics.

What I'm trying to say is, if it's not broken don't fix it. :D

[Andy W]

(yes, I didn't make it clear, mine is also able to open to full 90 degrees to get the airbrake effect)..
..a

[ClayH]

There's a video of Gordy landing his Super Ava with the split spoilers and it looks really nice that way. For contests you usually have your flight and landing planned prettty well to where you don't need to dive it from great heights and have the need for airbrake effect. I just want maximum control on final, and I'm thinking that since the spoiler is too effective as is, that there may be a compromise where I give up some airbrake affect for a smoother approach. Is my thought that there could be too much wash over the tailgroup valid?

Clay

[jrerickson]

Clay,

For what it's worth...Alex E. had the makers of the Topaz go to a split spoiler set up. Most of the guys flying them say that there is a little better control of the rudder and elevator with the split.

I've got a new one here waiting to be assembled (with center dihedral) so I'll give you a report when it's done. I've flown the full center spoiler for several years. It's fine, but I've never been able to leave it out on final; it cuts lift too much, even when only deployed 1". I end up "feathering" the spoiler as I come in.

John

[Wildewinds]

I'm happy with the curve I have with my regular Ava spoilers. I don't notice the elevator or rudder being blanked out by it.

[Andy W]

You're welcome to hack up your model however you choose, but there's no reduction in control authority on my AVA with even full spoiler, and I've landed in some pretty gusty situations - my attitude is, if it ain't broke, no need to "fix it".. :D
..a

[ClayH]

Andy,

Your Ava weighs 50% more than mine does.That would make it more stable on landing in both lightwind or gusty situations. I'm going to play with the elevator compensation the next couple of flying sessions and I've I'm not satisfied, I'll hack it up and report back to the group. You never know until you try!

[Andy W]

Good point..
..a

[rdwoebke]

Andy,

Your Ava weighs 50% more than mine does.That would make it more stable on landing in both lightwind or gusty situations. I'm going to play with the elevator compensation the next couple of flying sessions and I've I'm not satisfied, I'll hack it up and report back to the group. You never know until you try!

I have owned a Bubble Dancer (also with full spoiler) and currently fly an Allegro Lite (2 meter version of BD). The Allegro is very light (about 19-20 ounces) and I have good sucess with its full span spoiler. Yes, it does require quite a bit of elevator compensation. You can look at the BD or Allegro plans for an idea of how much is required. I have my spoiler setup so that at full spoiler the nose is slightly down. AKA, it is sort of "driving" towards the spot at full spoiler. If I hold a bit of up elevator on the approach, the plane will parachute in if there is any headwind (aka just drop and not make forward progress).

My 2 cents, from quite a bit of experience with full span spoilers.

Ryan

[rcko]

I have to double the opinion that the Ava has no issues with its central spoiler.

This past weeknd I de-thermallized my Ava numerous times by using 90 degrees of spoiler deflection in order to make a 1minute landing window from speck height. At no time did I expereince controllability issues. In fact, while decending the craft was maneuver into landing approach. The events were controllable steep decents but not a high velocity dive. I could compare it to free falling with a steerable drogue chute. However, I must say that it has taken quite a few flights to get the spoiler to elevator mix correctly setup to achieve trim at different spoiler deflections.

The key thing, in my opinion, is maintaining proper airspeed to achieve the desired control authority required to accomplish your task, the old energy management story. From what I have noticed, must folks are flying too slow when spoilers are deployed. The spoiler deployment further decreases airspeed and thus the model inherently suffers from a perceived lack of controllability. This might be a reason for the apparent belief that the spoiler is blanketing the control surfaces.

My opinion spoilers are usefull devices for controlling decent rate, attitude/glide slope with the benefit of airspeed controllability and Ava has a very nicely sized deviced to accomplish this goal.

[ClayH]

Your not going to notice any subtleties flying the Ava with full delpoyment at 500 feet in a full dive. My mission is to enhance the control of the plane the last 10 seconds of the flight. It's obvious that the Ava has way more spoiler area than is necessary - that's why so little deflection is recommended in the specs.

I want to have enough to slow the plane down to hit my target regularly, and no more.

I've already split the spolier, using 6 bays for each side for deployment. HS 65 servos fit nicely. A little more adjustment tonight and they'll be ready for testing.

Clay

[markdrela]

I want to have enough to slow the plane down to hit my target regularly, and no more.

Yeah, and my Maserati's brakes were far stronger than needed to coast to a gentle stop, so I dialed the brake pressure way down. :rolleyes:

I guess it depends on how you want to fly your Ava or BD. Like rcko, I want to do controlled vertical descents, and I want to be able to slow down from 40 mph to 10 mph in a few seconds. I can do that because my spoiler maxes out at something like 80 degrees. I couldn't to that if it maxed out at 20 or 30 degrees.

I've heard complaints about the "oversize" spoiler from people who use an on/off switch for the spoiler. OK, fine. But the Ava's spoiler is intended to be on a proportional throttle stick control, not on a switch. This allows you to deploy as little or as much spoiler as necessary in any given situation. If you want more precise control for small deflections, you can always add expo. If the TX doesn't have this capability, it's easy to set up via the linkage geometry -- just put the servo arm close to dead bottom center when the spoiler is closed. FWIW, I don't find such expo to be necessary.

[onethermal]

The big spoiler is great in fact I have gap seal on my spoiler witch gives me another 1/2 inch of spoiler surface, I had to put my elevator comp on my Stylus at 80 percent of down but my Super BD comes in on rails and will slow down to a great speed range.
I have put a picture of my Super BD for you to see what I am flying with, the wing is 150 inches with the extenions I put on it. The wing is a Drela BD and everything else is things I have added like full fuse rather than pod and boom also I added seven more degrees into each wing,my all up weight is about 69oz so it is around 7.3 to the square foot for loading, this thing flys like a big free flight glider and when it comes time to bring it back the spoiler responds so well I wouldn't want to change it in any way.

Clarence

[ClayH]

Using the Maseratti analogy, high performance cars today, as do motorcycles, use a smaller disc brakes in the rear (along with anti lock braking) to help maintain control under full pressure application. I have two programs on my 9303 for the Ava - one that gives about 30% spoiler and one that gives 80%. Both are on 6 point curves for elevator compensation and the curves are pretty close to just right. I'm certain that my feeling that the system can be improved comes from my relatively small flight time with this RES plane versus my time with full house ships. I know that the way that the two designs slow down is different. I'm kind of surprized that there isn't more support for investigating the split flap idea instead just going with the status quo. If people didn't try different ideas, that Maserati would still be using drum brakes.

Clay

[onethermal]

Clay
Yes RES ships are diffrent to a full house with flaps, Just look at the way the air flow travels over the wing and you will see diffrent results. go for it try diffrent things it is quite fun to see how diffrent changes affect the flight of your plane.
One thing I would suggest is ask for input from those that fly RES planes and elvauate what they are telling you because it will help you in your search for performance.

Clarence

[onethermal]

Clay
One more thing on design look at Merrill Brady's Marauder at

http://www.mmglidertech.com/marauder.html

I have one and it has top and bottom spoilers and it will slow down real fast.
Clarence

[ClayH]

Clarence,

One of the reasons I'm trying the split elevator is that I've been flying regularly with Merril the last month. Don't know that I'll go to the trouble of adding bottom spoilers though. He's got $4 in landing bucks from me and I want them back ;)

One thing that I will be able to do with the marvel of mixing is to have the split spoilers be active thru the first 75% of throttle stick movement, to be joined by the center section for the last 25% of the stick. Maybe the best of both worlds!

CH

[ChuckA]

I have a Super Ava and an original about the same side with a 48 inch center panel and split spoilers. The Super Ava floats better but the original flies better when spoilers are deployed. I think split spoilers are better but not enough better to modify the Ava. The Ava is my backup RES because it's more fun to fly an original as long as the lift is good enough to offset the better sink rate of the Ava. Also, the original does not have the stealth fuselage of the Ava so it is easier to see at extreme range.

[onethermal]

Clarence,

One of the reasons I'm trying the split elevator is that I've been flying regularly with Merril the last month. Don't know that I'll go to the trouble of adding bottom spoilers though. He's got $4 in landing bucks from me and I want them back ;)


CH

I am Mr B's Timer for the FSF and I can tell you if you want your $4 back you will need to practice,practice, practice :)

Clarence

[rdwoebke]

Also, the original does not have the stealth fuselage of the Ava so it is easier to see at extreme range.

I'll bite. What is the original and what is the stealth fuselage?

[ChuckA]

I'll bite. What is the original and what is the stealth fuselage?

The original is a 132 inch span model with a 5 piece wing and an original fiberglass fuselage from my own mold. The current version uses the Bubble Dancer airfoil and is an updated version of the model that I folded the wing on at the 2001 Nats. I call it LilAn and if you can figure out the name, you know a lot about ancient languages. :) A stealth fuselage is the super skinny pod with a black carbon fiber fuselage as used on the Ava and is very difficult for me to see at long distances. I found out how difficult when I bought Brian Smith's COP that used a Compulsion wing on an Ava fuselage. I could not fly it near as far away as my stock Compulsion.

PS COP means Composed Of Parts (from a Compulsion and two different Avas).

[rdwoebke]

That is interesting.

So you had a model you designed that you also called the "Ava"?

I guess you could paint the CF/Kevlar boom on the Ava...

If you think the Ava pod is hard to see the actual BD's pod is even smaller.

Ryan

[ChuckA]

That is interesting.

So you had a model you designed that you also called the "Ava"?

I guess you could paint the CF/Kevlar boom on the Ava...

If you think the Ava pod is hard to see the actual BD's pod is even smaller.

Ryan

My original design is the LilAn. I bought the Super Ava just before the Nats because the LilAn was not ready to fly RES at the Nats.

[Mark Miller]

I do the same thing on my Soprano as the good Dr. does. I use 80 to 90 degrees of spoiler to dive from altitude and I do not care about elevator compensation there. It will not reach VNE. I use much smaller spoiler openings on landing and try not to use them at all. If I need 90 degrees on landing approach I did something very wrong earlier in the approach.

The Marauder type spoiler is nice but is not within the AMA rules for RES. See rule section 3.1.6.c. Of course a CD can waive any rule but don't expect it to happen all the time.

Mark Miller

[s2000]

Isn't having any kind of roll control on the wing against the spirit of an RES model? I fly the Perfect if I want roll control.

[Mark Miller]

AMA rules also state in the same section that they must rise and fall in unison. Of course if you don't fly contests using AMA rules then the world is your oyster.

Mark

[ClayH]

Flew the new split spoiler today and I have to say that I think it has promise. Using 6 bays on each side that deploy about 60 degrees, the feel is a very gentle slowing. I deployed them fully at about 15 feet high on my downwind on landing approach after getting the elevator compensation adjusted, and the plane settled into a slower, nose-level approach until touchdown.

I will work on the spoiler throw to try and get about 80 degrees, and then work on the coupling of the center section when I reach 75% of spolier deployment. So far , so good.

Clay

[ClayH]

Here's some pics of the setup. I have the split spoilers on the throttle stick and the center spoiler on the left slider. At full deployment the all meet up to make one big original size spoiler. Haven't flown it yet with the center spoiler active, but now I've got the best of both worlds - full spoiler to lose altitude quickly and the split spoilers for sublte control on landing.

The AMA rules state that split spoilers must move together - supposedly to prevent any roll control. I wonder if this setup violates that rule even though there is no contribution to roll authority? :confused:

Clay

[rdwoebke]

Actually, split flaps are something very different than what you have there... That is on the lower surface.

My take if I were a CD for a RES contest. You can fly it that way, but whatever portion of the spoiler you plan to use you need to decide before the flight. AKA, if you just want to use the split spoilers, fine, just use them and disable the center. If you want to use the full width, fine, but it needs to move all at once.

3.1.6c.:

Two or more spoiler/air brakes may be used, but they must all act in unison and extend above the surface of the wing by the same amount when deployed.

Ryan

[asat]

If two or more can be used in unison why can't you either deploy the two outer or all three - as long as they all move in unison and you are not trying to affect the roll axis?

[rdwoebke]

If two or more can be used in unison why can't you either deploy the two outer or all three - as long as they all move in unison and you are not trying to affect the roll axis?

My read is that that is OK, so long as you don't have the ability to go with 2 or 3 within the same flight. If you could, then you would have a situation where there are 3 spoilers but 1 did not move in unison.

That is just my take as a CD. Please nobody press this issue at a contest I ever CD, this hobby is fun and does not have a lot of rules or "rules skirters".

Ryan

[ClayH]

Since I feel obliged to compete within the rules, I wrote the AMA about my setup, noting that I interpreted their rule as being one that is there to prevent roll control. The reponse that I got back was that my setup would be against the rules if the 3 spoilers didn't work in unison. They didn't address the reason for the rule. I think that if they did think it thru, they would allow my setup, but I don't expect a rule change considering how few people have RES planes configured this way.

I currently have the center portion slaved to the split spoilers and have it set so it only deploys on the last 15% movement of the spoiler stick. I have excellent control with the split spoilers the other 85% of the stick movement and disabling the center spoiler for AMA contests won't be an issue. For general flying though it does look cool and really dumps the plane over the landing zone :D

Clay

[IBWALT]

Clay, I would interpret the rule this way. If all three spoilers reached full open at the same time then they operate in unison. I think that if you made this argument that no reasonable CD running a contest would rule against you.

Walt

[ClayH]

Walt says"If all three spoilers reached full open at the same time then they operate in unison. I think that if you made this argument that no reasonable CD running a contest would rule against you.


In that case, you can be my CD anytime! Thanks for the support. Now I've got to go improve my landing scores by 50% to make the project worthwhile.

Clay

[emersunn]

"must all act in unison"

They all must travel the same from full close to full open. A CD would make you choose between the outer two only, the center only, or all three only - all acting in unison. Other RES pilots would be disadvantaged by your setup otherwise.

[IBWALT]

"must all act in unison"

They all must travel the same from full close to full open. A CD would make you choose between the outer two only, the center only, or all three only - all acting in unison. Other RES pilots would be disadvantaged by your setup otherwise.

emersunn, if you use that reasoning then half (probably more like 100%) of the res ships flying would be disqualified. Next time you go to the field see if you can find a res ship that has the spoilers up the same amount. No matter how small the difference there would be one. So they could not have risen in unison if one was up more than another.

Granted it's splitting hairs but "must all act in unison" is a very subjective term open to interpretation in many ways. It is my feeling that the rule was written to prevent the use of spoilers to control roll. The way Clayh has his spoilers set up does not give any extra advantage that I can see.

Walt

[onethermal]

emersunn, if you use that reasoning then half (probably more like 100%) of the res ships flying would be disqualified. Next time you go to the field see if you can find a res ship that has the spoilers up the same amount. No matter how small the difference there would be one. Walt

I know that my spoilers match movement to the hair, I use two servos and a Stylus radio so I can trim and adjust my spoilers to the same.

The main reason for keeping people useing spoilers in unison is to stop people from making it a sterring surface and getting away from the true spirt of RES :)

Clarence

[rcko]

Why is this setup an issue as long as the outboard spoilers move in unison and deflect ~equally? There is no "yaw or roll" control. The center unit is a redundant spoiler that would again, not alter yaw or roll control.

Now, if the rules state that the RES plane spoilers must be operated/controlled by one channel then I would think the setup would be in violation since it appears to use 4ch...

[onethermal]

It all comes down to what a CD will allow, if they want to follow AMA rules to the letter or if they want to go by the spirt of the rule.

[emersunn]

"must all act in unison"

They all must travel the same from full close to full open. A CD would make you choose between the outer two only, the center only, or all three only - all acting in unison. Other RES pilots would be disadvantaged by your setup otherwise.

Follow up:
My perception as to how a CD would react. No I am not a CD.
Follow up to follow up:
I'll bet you dollars to donuts that the other competitors will pressure the CD to uphold the "act in unison" rule, ending in the conclusion I stated above.