Wow...I can't believe how many ERAU grads there are on this forum.

With the Anhedral stab I don't belive that we can"resolve" the areas like a vector and add some in the vertical plane. The anhedral stab works differently from the standard because some of the surface is below the area of the wing downwash. We have to avoid trying to invent theory purpose built to rc aircraft, rather use fullscale design principles and methods to explain what some of our experiments tell us.

Anhedral stabs on full scale are usually because the designer is trying to avoid unfavorable downwash or jetwash and has no other choice structurally than to "lean" the stab away.

I really doubt if the tiny fin is actually impacting longitudinal airflow due to the spiral propwash as both Electrics (big mass of air being moved slowly) and Glow (small mass moved quickly) both seem effected similarly. Additionally, do the improvements go away when you trottle back (as in a downline)?

Someone should build a small smoke tunnel, say 2'x2'x2' and run some experiments to visualize the effects....any takers?

Colin.

Riddle grads??? there goes the neighborhood!

Prescott Class of '94

- I've been ID'd!!!!!!! I'm now glad that I caveated my previous post with the "kegs-of-beer" and "bad grades" statement.
Jim "Woody" Woodward
Prescott 96
- They doubled the lane width getting from campus to Wiskey Row too (after we left right?)

OHHHH??? Really!!! Explain then how a pencil thin fuse with low wing and ample dihedral will knife edge far better than a pencil thin fuse with zero dihedral, mid wing platform. All else being equal

Areas are indeed additive or subtractive. The higher dihedral indeed introduces a significant vertical component at mid-ships. Don't take my word for it...do the experiment

As far as the small wing and its impact, there's little doubt that it affects how the model behaves..... the fact that full scale aerobats are not using such devices yet, matters none at all. Well, according to friends who knew him, Leo Loudenslagger was experimenting with such on his aerobat before his untimely motorcycle accident.

The effect we seek from the small fin is small indeed. In my experiments with larger fins, I wasn't happy with the results for aerobatic purity but sure were fun to play with.

As far as theory invention, hogwash. All theory is invented....then one follows the scientific method and either proves or disproves it. That's basically what I do both in my vocation and avocation.

One final thought and I'll leave this subject, roll couples can be induced or removed by canting the dorsal fins. In other words, one could remove or add roll couple with applied rudder simply by placing dihedral or anhedral on the horizontal surface of the cannabalizer. The effect isn't great but is proportional to the area canted; for trim, it's another way to do some aerodynamic fine tuning rather than touching it with electronics. Just another little tidbit from my experiments

Best regards and happy holidays everybody

MattK

Don't worry about it Jim, being an Air Sci grad, I have no idea how the planes work... aerodynamically, electronically, mechanically... but I can sure break 'em!

As far as Willow Creek Rd goes... it's plenty wide enough if you use the divider as a centerline! Or so I hear.

Tom Messer
Fall 94 PRC

That's the whole key. We can discuss this for years, but unless you build it and fly it, you're guessing.

You start with a solid theory and then test it. Sometimes it works out, sometimes it doesn't. Just keep in mind that pattern planes are all about balance on a razor's edge. if you change one small thing, it affects everything else to some degree. Therefore blanket statements don't really apply, like the cannalizer. While it's been said "this or that plane doesn't need it" it just depends on who's flying it and what thier particular set up is. In a lot of cases especially with the latest wave of planes, you can do just fine without it, and adding one will have a small effect, and in some rare cases, an adverse effect especially if the shape/area/placement isn't quite right. But put one on a plane that is a few years old, and that's where you can REALLY feel the difference.

In my testing the newer extremely tall fuselages tend to have the same effect if the area distribution is right. Shape is everything, and smooth airflow is pretty important. On these planes I don't think the canalizer has nearly as much effect as it does on the older planes (generally speaking). A few of the newer planes MAY have crossed a line into "too big" in which certain other aspects of it's flight characteristics suffer.

Back to the main topic of this thread...I like the way Chip's new plane looks. It's very Osmose-ish, but it has some good lines and interesting features.

Oh well I'm not an expert on this stuff, I've just tried a lot of things. And these are the things I've found thus far. Your results may vary

-Mike

OK chaps, an aerodynamics theory numpty here(and apologies if it's too far off the original topic) but:
I'm happy with my Leviosa for anything in PO9, and FO9,but myAbbra,by comparison, def lacks rudder authority for the rollers and the K/E loop.
I tried a canaliser, and, whilst the Rudder authority was certainly improved, the other effects on the model set-up threw everything out so much that I gave up with it.
Would it be worth trying just a dorsal fin, without the little wing?

That's what Jim W did, and it definitely seems to help according to him. Maybe he'll post a pic?

-M

Hey - give it a try! I was happy enough with the vertical fin alone to stop the experimentation. The using a DEPS system, and a YS 160 with short Hatori pipe, 2 cell lion mounted just ahead of the landing gear plate, the Abbra had 7% up elevator mix to rudder. These two pictures with the tape measure are the "cut" and final dimentions of the fin (for me anyway).

Also attached is a picture of the fin I installed on my Aggressor.
Thanks,
Jim W.

Ok, so to sum up: You're saying it "purifies" the rudder input on the Abbra? And the difference was about 6% or so, do you know how much the elevator was actually moving with the 6-7% mix?

Was the difference about the same on the Aggressor?

How much positive incidence are you running in the wings? I seem to find the sweet spot on my stuff to be between 1/4 and 1/2 degree, depending on personal taste. I would guess you MAY be able to get away with running the wing incidence slightly lower? That's just a guess, not sure.

Interesting. If you remember I had one of those made for the VF3 in the beginning and we never actually tried it on that plane. I still have it and the mounting points are still intact. I would be very interested to see if it made any difference, or rather how much. looks like I need to mail a small package to Florida, because I hate lingering questions.

-M

Is the T-Canaliser available separately? I would like to purchase one please.

This fin creates a positive pitching moment with rudder on my Abbra and Aggressor. Enough that is basically eliminates the up-elevator mix if you are willing to size it correctly over a couple flights. I use long control horns so 7% mix produced a miniscule movment of elevator - about 1/32". The Aggressor was closer to 1/16".

I remember the little fin you made for the VF3. What really shocked me was the day I flew the anhedral stab. That too made for a dead-ass straight knife edge. It made rollers a piece of cake, but screwed up a lot of other things.

You'll just have to have Ryan try it because there is just a bunch of ifs in the equation now. For instance, if you are already close to zero mix for knife edge, and you add something that creates a positive pitching moment (like on my Abbra and Aggressor) what will that do to the overall flyability?

I didn't think at the time (March/April 07) that just the fin would have a big effect.
Thanks,
Jim

Jim

You are flying the old canopy on your wood aggressor we found in testing that the old canopy was blanking the rudder making it less effective. My agressor (nomex) has so little up elevator mix that you have to put your hand on it to feel the thing move, definatly alot less than what you are getting with yours. As far as percentage goes 1.5% up w/ left at full rudder deflection approx 40 deg. of throw , right is 3% up same throw. Thats at the extreem, I use a point mix for the up and don't get to full rudder throw when flying a normal pattern (advanced) (LOL)! Maybe you should test the updated canopy it should drop right in I think..


gary

Yeah it's really close to zero now. Just tweaking the wing incidence one turn either way can take it from 4% to zero, but then you pick up a slight pull in a downline. I mean it's CLOSE....so close that unless I was flying F competetively I wouldn't even bother with it...and even then.... (you flew the plane, you know what I mean...and the new tail made it even better)

Yeah I'm gonna send it to Ryan to play with. It's just monokote and it's plug in so if it doesn't do anything, who cares. if it does, then cool too (I still have the laser cut pieces LOL)

I think on the anhedral stabs we simply had too much anhedral. I loved your report on the pitch mix, but the way it uncoupled the roll axis was nuts. As the plane is it's dead zero in roll. But it's December, time to play again!!!!

I would have loved to have flown the Abbra down there, but the weekend was sort of crazy flying all the way till dark (and after, damned kids, makes me jealous).

In case I haven't said it enough, thanks Jim for all your help on the VF3 project. You have no idea how much I appreciated it.

-Mike