Marcelo,
Glad to see you here on RCU. if you can give us the specs. and weight of the Pass-Port
with the YS and Hacker.
Thanks

Has a price tag for this bird been established yet and when will it be available? I like the design outlook better than the Osmose,..speeking of the Osmose have they been shipped to the US yet,...I have one on order? (perhaps I should wait if it will be soon!)

No T-cantlizer I see,...any input as to why or why not?

Bill H.
"Kick the tires and lite the fires and away we go!"

The Cannabalizer is a device that changes the trim of the model at various attitudes. When yaw command is applied, the device will tend to add or subtract (depending on its trim set up) some pitch trim and hence fix the model's attitude under the circumstance. An example is the general trend of certain designs to pitch to belly in knife edge. The Canna will take care of most if not all of the unwanted pitch without having to make an electronic trim condition in the radio. In other words, the Canna fixes a fundamental aerodynamic issue.

On the other hand, such "external" strakes or extended surfaces can be used to enhance certain flight characteristics or control response. For example, consider the role of the dorsal fin of a shark. The fish uses the fin as a pivot to turn on a dime on its prey as it propels itself with the tail. Without the dorsal fin, a shark wouldn't be able to turn as quickly. Such a device on an aircraft has similar effectiveness when rudder is applied....it essentially improves yaw response compared to the same exact design without such a device installed.

The grandfather of the use of such a device on models is Nat Penton. He pioneered such devices about 25 years ago in his VooDooXpress design, a model way ahead of the schedules flown at that time. Fast forward 25 years and here we are.

These devices are not necessary for some designs due to the designer having taken the necessary time and effort to perfect his design before offering it to the public. Bryan Hebert's design are most noted for their neutral flight envelope regarding this feature. Chip's also

MattK

Hi Arch,
Don't you know about the Jim Martin school of thought? "Paint it all pale metallic blue with slightly darker stripes on the wing leading edge, and hide everything!"
Fortunately for Jim, he had unusually acute distance vision and he used it to that effect.

later,
Dean

Hello MTK,

I understand the theory of the cannablizer and the common uses for them,..having an aeronautical engineering degree. However, that was some good info. for those who may not. I was simply curious, as the the Pass Port is very similar in airfoil shape, thickness and design from looking at the provided photo,... with very similar fuse lines. I know the Osmose was designed for the cannablize,..so I was told anyway?

I was trying to find a distinct reason between the two "visual" designs, one with and one without, being similar in these areas. I would rather wait for a Pass Port, unless it will be into the late summer. And if not, the Osmose it is! I need a new bird to put my new 170 DZ into,...sooooon!

Bill H.
"Kick the tires and lite the fires and away we go!"

Although it doesn´t use a T-canalizer, the Passport isn´t free of aerodynamic devices, at least the original model was not. I believe this particular model was the one that crashed before the US Nats.
If you look closely at pic of the plane with Marcelo, you can see the separation lines on the wingtip, so these devices must be removable.

BrunoCH,
You are right, the SFG's are removable. The tip has 2 screws that hold them on so you can fly with or without them

Hi Guys,

Is that the split-rudder equipped Passport? If so how was the split rudder used in flight? Did the rudders swing in unison for normal flight and split just for downlines?
Thanks,
Jim W.

I would like to know that too.
Check out this photo. Crazy!

Bill,

I don't think any airplanes are designed specifically for a canalizer. It is a band-aid to mask some performance deficiency. I didn't know you were an aeronautical engineer. I'd love to pick your brain sometime. I really liked the Pass Port when I saw it at the WC in Argentina. The one that I saw down there did not have a split rudder, I'm not sure if that's going to be an option or not.

Hey Ryan,

I have several degree's a major\minor and a masters. We've had several conversations about fluid airfoil designs, etc,...look forward to many more. I'm sure you have some great ideas!

In the Osmose blog page 9, I asked the question about flying the Osmose without the T-canter? The answer I was given was,....the Osmose was designed to incorporate the use of the "T-thing" and without it,.. it changes the characteristics alot! I don't know if this was an after thought or not for the Osmose, but it's an answer? Perhaps CPLR did his homework on the pre-runner to the Osmose and incorporated the aero bennefit of the T-canter into the Osmose's general design character,..who knows?

I received my 170 DZ today,..what a nice machine!

Bill H
"Kick the tires and lite the fires and away we go!"

There is many a reference or statement to the canalizer or dorsal fin being used to correct, or in effect become a bandaid for some airplane's deficiency. Other people would say, "my plane don't need a T-canalizer." If CPLR is using it, there is something valuable going on. If Akiba saw fit mount one to a Proline which already has lower strakes on the belly pan, there must be some value. If a Brio flies well without one, and better with, there must be some value. It if helped Dave's Prestige or my Agressor, etc....

Many people with various platforms have gone from without, to with and felt the plane flew better. Do all these plane have the same design deficiency? What is the design deficiency?

For my own experiments on my Abbra and Aggressor I installed a dorsal fin of approxiamtely the same area as a playing-card, behind the canopy of each plane - did so after a discussion with Dave L. The planes are totally different: Mid-wing mid-fuse thin stab versus mid-low-wing, wide-body thick stab, etc - totally different designs in every possible way. The addition of this small fin had the EXACT SAME EFFECT on each plane. The longitudinal position of the fin doesn't seem to matter much as the one on the Aggressor is mounted to the removable canopy, and the one on the Abbra is mounted a little further back.

The predominate flying quality change to each plane was that it counteracts negative pitch with rudder application - dramatically. After setting the pitch mix to zero and still recognizing a pull to the canopy for knife-edge, I trimmed the height of the fin until it was zero on say left rudder and maybe 1-2% on right. There was left a very tiny difference between left and right rudder.

Did it only fix knife edge? No. Some planes may have a low knife-edge mix but still react with a lot of negative pitch in level flight rudder turns. The dorsal fin seemed to not only fix knife edge, but also really help flat rudder turns. You can hammer the rudder pretty hard now and get mostly yaw without funny business. At some point the plane gets upset, but that is way beyond the normal inputs for rolling circles, rolling loops and such.

The other mild improvement was that overal tracking: inverted, upright, power-on, power-off, all seemed to just lock on better - both planes. I could not detect a change to the roll mix of the planes either. So at this point, I see no negative flight quality change, and a bunch of positivie changes going on. It flew so well that I abandoned the next step in the experiment of adding the top piece (.... maybe I should try though??)

So back to the main question or critism - what is the single thread of plane deficiency between all these designs? Could it be rotational prop thrust? If its rotational prop thrust is the design flaw that the platform is not straightening out the flow before it hits the tail?

For me, I'm going with a simple explanation that given such a small addition of fuselage side area and the aspect ratio of the fin, that it is basically straightening out some of the prop flow before it hits the tail and that is helping the plane. It would be great to wind tunnel test it to know for sure, but I'm just as happy to be ignorant of the exact cause and be happy with the measureable, noticeable effect.
Thanks,
Jim W.
- yes I have an aerospace engineering degree, ERAU 1996 Prescott, AZ

For me, I'm going with a simple explanation that given such a small addition of fuselage side area and the aspect ratio of the fin, that it is basically straightening out some of the prop flow before it hits the tail and that is helping the plane. It would be great to wind tunnel test it to know for sure, but I'm just as happy to be ignorant of the exact cause and be happy with the measureable, noticeable effect.
Thanks,
Jim W.
- yes I have an aerospace engineering degree, ERAU 1996 Prescott, AZ


Great explaination Jim,...I have yet to experiment with it myself. Pehaps thats why those guys (CPLR, Akiaba, QQ, etc) are the pioneers that continue to refine and evolve these machines and the sport. Thank you very much for your input!

Bill H.
"Kick the tires and lite the fires and away we go!"

By the way CPLR made a comment and said to a friend of mine, he did not understand how is it everybody was not using the canalizer.

I think it was originated to correct a flaw, but this result was so good it was incorporated in all his models.

Regards

Bingo, you got it Jim.

One other thing on the comment that it doesn't seem to matter where the thing is placed....be careful. Too far forward and the model becomes really weird. Stall turns and snap rolls will suffer. BUT the model will do fantastic tail slides.

As a rule of thumb, you may want to place the dorsal from the CG to as much as 1 MAC aft for improvement in several areas. If pitch to belly is all you want to fix, then anywhere from the CG to the fin works well.

MattK

Jim,

I certainly don't mean to undermine your knowledge, however at the WC, Christophe had his canalizer in a different position on his Osmose than he had initially, and said that the longitudinal placement made a big difference. I also have heard Don Szczur talk somewhat along the lines of noting the difference in the performance of his Brio with the canalizer, and he said, interestingly enough, that stall turns required more rudder. Also, when you refer to a dorsal fin, I'm assuming that you're referring to literally a fin, and not a 'T' canalizer. Similar to what I saw on Dave Lockhart's Prestiges at the Nats this past year. Does the addition of the wing on top of the canalizer fin change anything?

I would think that the placement of it would be very critical. From what I understand, it is used to straighten the slipstream. Every diagram that I've seen in my entire life shows a slipstream as a very loose spiral that encircles the fuselage a few times and ends up hitting the side of the vertical fin. Is this a simplified depiction to show the general concept of what it is, or is the spiral really compact, almost like a spring? If that's the case, I can see where the placement wouldn't be as critical as you're hitting that spiraling mass several times, but something is making me think that the slipstream is in direct correlation to the RPMs the motor is turning. Am I correct, or is that something that is understood when talking about it? It's been a while since I really studied aerodynamics, so I'm more than likely quite rusty. Also, I would imagine that prop size has something to do with the performance of the canalizer or dorsal fin. Did you experiment with props to see the difference it made? Does a higher pitch prop cause the "spacing" of the P-factor to be greater?

I apologize if I'm completely off base here, or if I'm over analyzing anything. Any insight would be much appreciated. Take care.

According to BPLR (the brother of CPLR) the point of the canalizer is NOT the fin, but the small wing on top. The fin is there to get the horizontal wing in the wanted position and angle.
Ola

It's probably a combination of both elements. In high yaw the fin will generate a vortex that will re-energize a stalling rudder and generally increase control authority. (Vortex generators are comonly used in commercial avaition) The wignlet will work as an endplate making the fin more effeciant/increasing the effective area. The winglet itself is probably just outside the relative slipstream and may not be influenced in the same way the stabilizer is. As a result in level flight it can be set to 0 incidence and have no impact to overall trim while the wing incidence is at some small positive angle. In a downline we are trying to fly 0 incidence but wing incidence makes a neutral trim impossible, the winglet may add an element of trim to help as it is at negative incidence relative to the wing.

I didnt think it would be effective as our Reynolds numbers are so low. I suppose the aerodynamic forces on 2M planes are low enough to have this work.

There's lots more that can be discussed, theorized etc....but it looks this thing works so lets build Ts.

Colin.
BSc AE ERAU 1990

Nice post Colin - I think by definition of an RCU thread, we will not be able to reach theorhetical agreement , which makes the field tests quite satisfactory for me to stick with for me.

Ryan - I only performed the experiment as I noted above. Between each plane the longitudinal placement didn't seem to matter as the overall effect was the same. The fin on the Abbra happens to be about 6" further back than the Aggressor. From the tip of the spinner to the center of the fin is 38" for the Abbra and 32" for the Aggressor (just measured). I did not change the location of the fin on each plane to test the performance difference. Like I said, I was satisfied with the performance gain and did not add the top part to the fin. For me this is not a full blown testing program to try different combinations as I only have so much time to devote to this.

Spiral slipstream diagrams.... Reaching back through Program Management, US Army brainwashing, kegs of beer, and my share of bad grades, I offer this opinion: A typical text book diagram is used to illustrate the point of a lesson, or is a momentary snap-shot of the flow, and does not necessarily depict the actual flow. Prop diameter, pitch, RPMs, number of blades all affect the shape of this spiral flow (or the pulse of it not withstanding free stream affects on the plane and prop-generated spiral). Once the prop starts turning it generates a cointinuous spiral woosh down the plane. There are not little tiny individual sprials travelling down the plane (like some of the sprirals miss the fin and others hit it) - it is a continuous sprial air flow. How tight it starts (or finishes at the tail of the plane), and what if any frequency change takes place as it interacts with freestream air, is totally unknown for these planes (if someone has this information please post it).

I sort of liken the situation to winglets. A wing tip generates a vortex that spirals from the bottom of the wing tip up, around, over, and splashes back down on the top surface of the wing (adds drag?). If you wanted to completely stop this phenomina the winglet would be huge (something like 1/5 the wingspan (help here) - anyway the winglet gets incredibly large to completely stop this from occuring). But we see smaller versions of the winglet in service on all modern newly build airliners because perhaps in reduced size they still affect the whole equation. These small winglest are not stopping 100% of this phenomina, but they are adding some positive benefit beyond marketing.

So, I just think that the flow is interrupted, then straightened by free stream airflow, prior to going over the tail. I couldn't begin to tell you though where the optimum place to do it is. Also, I don't think you can fix it another way by integrating this very small fin area into the overall fuselage profile and say, "now the fuselage has the same area as with the fin therefore it flies just as if there was a fin like before." It doesn't work that way. A fin can be an efficient surface to do this. If you just made the fuselage a teeny bit bigger to account for the fin, nothing really changed.
Thanks - now ready for the practicing engineers, folks with good grades, and trial-&-errors to offer some insight.
Jim W.
PS - did CPLR move the fin to change the effect, or move it to get it off the removable canopy and better fixed to the plane? Its nice to have the WC stories come out.

Arrrggghhhh...ok why not.

You're all right, and you're all sort of right...by the best I can determine. It reminds me a lot of the anhedral stab question...."why, what does it do". Amazing how long it took to get any form of a semi-clear answer, and it's still just a guess at best. The biggest thing it does is lowers the effective centerline of the stab. Secondary it sort of affects the airflow over the rudder ONLY to the extent that the air is splitting higher on the rudder than the effective centerline of the stab. And to the question of why it seems to help some planes and hurts others? It depends on where the stab should have been in the first place

As to the canalizer. I think you're all close on this one. MOST modern designs with current force arrangements and the way we trim them pitch to the gear in KE, so putting it behind the canopy line (and hence CG) is why it affects all designs the same way. The question is how much...some planes are like night and day, and some...ehh a little maybe. Some just don't really like it all that much.

Jim asked what the design deficiency was: simple answer. Shape, from spinner to the back of the rudder, and everything in between, compounded by a spiral airflow. There is mainly a straightening effect that I can tell so far, and that's about it. But it depends on the shape of the plane as to how much difference it makes. I can tell you that the vertical fin like Jim and Dave are using seem to be the large majority of the benefit. What the horizontal piece does, well that's where the can of worms opens. it is my opinion that these should be used for infinitely fine tuning. Nothing wrong with that except they're ugly (LOL)

I have seen it used to excellent effect by Don Szczur and Cameron Smith. by adjusting the little wing they fine tuned the plane's behavior in uplines, downlines etc. Thier's are adjustable. Perhaps the one Cristophe uses is fixed and designed for a specific airframe? I'm just asking, I don't know.

What I do know is the community has made quantum leaps in design fine tuning over the last few years. A crapload of mix used to be the norm on many designs, now it seems if you have over 5% something is wrong. Obviously they're doing something right, but there will never be a perfect plane. However we as pattern geeks will never stop striving for it, and that's what sets us apart I think. Don't you?

-Mike

Oh and about the split rudder:

According to Chip it has nothing to do with downlines. he had his rigged where only one side moved. They met at center, than one side stayed locked, and the other swung out into the air stream. Now this is one I'd like to play with....

-Mike

With regards to the cannabilizer, and anhedral...my thoughts. The addition of the dorsal fin/s can and does generate a cleaner airflow over the fuse. The reduction of required right thrust was one of the big selling points for me. Among other benefits, there seems to be a noticable lack of pitching when applying rudder in level flight. Anybody notice how this generation of F3A planes generally uses less aft sweep on the wing? I think placing the fin/s near or just aft of the CG will generate the best force arrangement for rolling manuevers, however, as stated by Jim W., the further forward you go, the closer you can get to unfavorable tendencies.

As Mike has done, I have flown my design with and without anhedral stabs. At first, I thought there was a pitching tendency in the plane with the straight stabs. After some careful checking and CG adjustment (the straight stab plane was tailheavy), I found that the straight stab required zero trim with rudder in one direction and only a slight mix with the opposite rudder. The testbed with anhedral requires zero in both directions. This only means that with my "particular" fuse shape, there may be a very slight benefit with the anhedral stabs. I think we can all agree though, with or without strakes, fins, winglets, anhedral, etc., many of the F3A planes available today are very, very good (well, the ones that are tested before going to market [&:] ).

-mark
ERAU 93'

LOL exactly.

I got to have my first really CLOSE look at F-09 last weekend, as it was flown at Tangerine. I don't think any of the planes there were at a serious disadvantage, or HAD any real advantage, but some of those manuevers are REALLY demanding of proper airplane trimming. P-09, no big deal, nothing in there really demands anything but a straight airplane and a good sense of basic pattern. but some of the F manuevers are REALLY demanding of the pilot and the plane. The most notable and somewhat suprising was the outside loop with integrated 4 point. That third point will eat you for dinner if your plane is doing ANYTHING it isn't supposed to do. The KE loop isn't really all that bad, just hard to keep it round especially through the transition. When the side loads swap sides in that last quarter or second quarter, you had better be wired tight. These manuevers especially are where fine tuning is a must.

Mark I think your plane has plenty of airflow straightening already. But it does work extremely well.

-M

As I understand it there were issues with it being fixed to the canopy (I think vibration/flexing and such). If you will notice in various pics BPLR has his mounted to his canopy.

I have played with them myself and dont feel longitudinal position (within reason) has much of an effect.

The anhedral stab adds vertical area below the fin....ventral fin area. The vertical component it area terms is easily figured trigonometrically. That extra ventral area helps balance the effects of the spiralling air stream at the longest moment arm available and hence a small amount of area goes a long way

MattK