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Old 09-16-2019, 11:13 PM
Marvan Maxwell is offline
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Toc

I found this the other day.


Van
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Old 09-17-2019, 05:59 PM
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Gettin better 1 [email protected] a time!
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Originally Posted by Model_Builder View Post
Hi Whipash,

I'm relieved to see you post this vital information. It is all true. Hal Debolt and his contemporaries (the pioneers) went for no coupling, or as little as possible in their search for aerodynamic predictability and stability.

There is no argument I can see in refuting your assertions. Some model owners may find themselves in position to do little about the set up they have. Anyone designing will take it under advisement.

Anyone who has read and understood the premise will be rolling it over in thought. This insight deserves a reply and due credence.

Thanks for bringing it up, or should I say putting it in perspective.
-Bill
Thanks for the replies, gents. I guess I'm still confused as to why most of the 3D monoplanes we can now buy, have the Hstab nearly, if not exactly, in line with wing/thrust line. I originally thought that was to minimize or eliminate coupling issues, but this discussion refutes that. Just a simpleton here trying to learn lol
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Old 09-17-2019, 06:50 PM
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A couple of things; there is no one right answer, certainly no wrong answer and many in between. Right, I know that helps!

The differences in Mono vs Biplane is the first hurtle. Although it is pretty easy to make a model biplane fly great for sport flying and can even do precision fairly well with a really great pilot, the TOC biplanes were pretty much purpose built for precision flying. Even in the hands of some of the best model flyers ever, there is a reason there was a bonus for using one. They are just more difficult to fly well through specific maneuvers; my opinion only from experience,

Tail Slides, any Snap maneuvers, regardless of line or type, POS or NEG and partial snaps are really interesting with large model biplanes. Even built very light and spans shortened they have a lot of momentum build up in rolling maneuvers.

Until Mr. Hyde started to use huge tail ratios and very large throws, flying 3D with the TOC biplanes was a LOT of skill mixed with even more luck.
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Old 09-17-2019, 08:54 PM
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Gotcha--I guess I'm muddying up the discussion with the monoplane questions. I can see more issues with biplanes, as you noted. Thanks for the replies!
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Old 09-17-2019, 11:35 PM
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Love the Artwork

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Originally Posted by Marvan Maxwell View Post
I found this the other day.


Van
Thanks Van!

That is a great piece of Promo Material, nice size. It's the only promotional literature I have seen on the model and I have tried to obtain every magazine that has a Cover photo, pic from a different perspective and/or an editorial to match. Never knew plans were available separately. I wonder who all had parts? If I could get a second set of parts I would be at the project quicker. Much rather build a second at same time.

Thanks again, Bill
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Old 09-18-2019, 03:58 AM
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Originally Posted by wyo69cowboy View Post
Thanks for the replies, gents. I guess I'm still confused as to why most of the 3D monoplanes we can now buy, have the Hstab nearly, if not exactly, in line with wing/thrust line. I originally thought that was to minimize or eliminate coupling issues, but this discussion refutes that. Just a simpleton here trying to learn lol
I agree. You are correct. In a monoplane they do want to line up the wing and stab with the thrust line. Please don't get confused by some of the misinformation given in this thread. If it doesn't make sense, then it probably isn't correct.

What makes sense is what Dave Patrick said in his book on "Radio Controlled Aerobatics for Everyone", 1994, by Air Age Inc., ISBN 0-911295-31-3. Refer to Chapter 2, page 16.

Dave explains some design related issues to try to get a plane to fly as close to neutral as possible.

On applying rudder, the amount of dihedral in the wing, or anhedral, is what generally affects roll coupling. Typically the closer the wing is to the thrust line, the less dihedral, or anhedral, is needed to achieve no coupling. In the past many aerobatic planes, such as the Extra, with low position wings, had some dihedral, even if it was just that the top of a tapered airfoil was flat. With two wings, or biplanes, there are other things that can come into play. (airfoil shapes, incidence of each, horizontal and vertical center of gravity, weight and downward eccentricity of landing gear, and size and vertical eccentricity of the rudder). It can get complex, if you note that in knife edge the landing gear hanging out to the opposite side of the fuse from the rudder is trying to roll the plane back upright, whereas the rudder, being eccentric on the opposite side from the landing gear is providing a force that preventing that very corrective rollout action by the gear.

On applying rudder, the vertical position of the stab is what generally affects pitch coupling. Although, some other things, like the shape of the cowl, or relative incidences of the wing and stab, can also affect this pitch coupling.
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Old 09-18-2019, 07:23 PM
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Rudder / Pitch coupling..... I don't think so. We will pursue this in real world experiment in the coming months.
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Old 09-18-2019, 10:26 PM
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Rudder / Pitch coupling..... I don't think so. We will pursue this in real world experiment in the coming months.
Well, there are two types of coupling with application of rudder: pitch and roll.

And, yep, by all means experiment. That's the best way to convince yourself. However, don't change more than one thing at a time, otherwise, you won't know which actually affected the results.
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Old 09-18-2019, 10:52 PM
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One note on biplanes. They always have an issue with compressibility of the air flowing though between the wings.

That's where they get quite a bit of drag. Typically, the fatter the wing the worse it is. That's why you often see Ultimates with thin airfoils. Also, the incidence of the top wing is often different than the bottom to help deal with the compressibility of the air flowing between the wings. It is not uncommon to have slight negative incidence on the top wing, and a slight positive incidence on the bottom wing, to help get better flow between the wings.

Another way to possibly deal with the compressibility issue is to have a semi-symmetrical airfoil with the flatter side down, and the same semi-symmetrical airfoil on the bottom with the flatter side up.

And, then the vertical position of the two wings, relative to the thrust line and stab affect the incidence of the stab and how it will affect coupling.

So, you may be able to see that biplanes are more complex to get no coupling. Good luck guys. I might try playing with a biplane in the future, but for simplicity, I will stick to monoplanes for now.
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Old 09-19-2019, 07:48 AM
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Thanks for the thoughts WINGWALL, lots of good solid model design in them. Most of my comments on the TOC biplanes topic are based on the TOC models I built or took a good close look at during the contest over the years. There are so many subtle changes that can make the difference between a winner and also flew.

The first built up Ultimates we did in '88 flew better than the '90 glass version, even though they were setup nearly identical and were very close in weight. The wood version was just a few ounces lighter. The super thin wing was the key, basically a NACA 0006.
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Old 09-19-2019, 06:20 PM
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Thanks for the thoughts WINGWALL, lots of good solid model design in them. Most of my comments on the TOC biplanes topic are based on the TOC models I built or took a good close look at during the contest over the years. There are so many subtle changes that can make the difference between a winner and also flew.

The first built up Ultimates we did in '88 flew better than the '90 glass version, even though they were setup nearly identical and were very close in weight. The wood version was just a few ounces lighter. The super thin wing was the key, basically a NACA 0006.
I would love to get plans of the Carden Ultimate that Carden was testing a number of years ago. There was a build thread on it, with final build pics. And, it looked so good.

I was seriously planning to order that kit. However, they had problems with it in flight tests. It ultimately (no pun intended) came apart in the air. They never indicated what may have been the cause. I don't know if they had even identified the problem. Whether it was just a structural issue, where a member was too weak, or if it had a high dynamic force issue from some part of the plane that went into flutter, they apparently decided to not continue with the design and kitting of it.

I really wish they would have solved the issue, and made a Carden Ultimate kit.

I am aware of one other Ultimate, of 40% to 42% design if I am not mistaken, and from a different manufacture, that a local IMAC pilot built, which had the top wing panel come off in flight. The aluminum cabane strut over the fuse failed.
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Old 09-20-2019, 05:30 PM
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Our '88 Ultimates used .060 6061 aluminum sheet bent with a 2" radius at the fuselage turn up. There was a left and a right. This was a bit wasteful from a material use standpoint but the alignment of the struts was perfect. Getting all of these angles correct was some fun! It also helped to have a very large hydraulic bending brake in the shop.

I like to use poster board patterns for the final shape and fit. These were in the days before CAD so the layout was drawn in pencil and a little cut and fit got you to the final shape. The Joiner block at the top wing was a 1"x1" aluminum block with a single 1/4"x20 steel bolt passed through from the top. I used this same method on the '84 Stearman and a Pre TOC- 10-200 build in 1987. We never had any trouble with this setup.

The wing at this attachment has got to be solid. We used a 3/4" maple dowel captured top and bottom with a .010 G10 wafer 2" in diameter, and then a layer of 4 oz glass cloth to capture and harden the whole thing in place.

Basically these become wood/glass eyelets embedded in the wing at the attach points.

The '88 Ultimate that crashed still had these attached to the struts solid even with the wings destroyed.
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Old 09-20-2019, 06:16 PM
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That looks great Whiplash. I like it. Triangulated in three dimension, with reasonably wide plates that are aligned so there is minimal wind resistance. It appears the only issue might be if the struts receive a high enough axial load to buckle in the weak direction, i.e. out of plane of the plates. The critical detail would be the thickness of the plates.

Yeah, and I like the way that you bent the plate assembly and bolted it to the frame. The critical bolts would be those just next to the bend. Great detail.
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