question on dihedral and leadouts

Keith

I think I kept the BC near inline with the engine thrust line for two reasons, 1) I retained the take apart/removable wing ala r/c, so there was no control hardware in the wings at all, other than aileron linkages. These were to be used for trim features and were adjustable. Just a small mod to the r/c servo linkages here. 2) with the near thrust line mounted BC in the fuselage I ran the leadouts over top of the wing to effect a straight sight-line from handle to BC with the aircraft in a "wings level" attitude. I've thought the need to keep the control lines level (in relation to "wings level"), between BC and the handle important, so as not to induce a wing-up or wing-down tendency due to any lines changing direction after the leadout guides. Given line tension concerns I thought the plane would fly Inboard-wing down as the lines found center while under tension during flight if this was not done.

I also have pondered the r/c airfoil on this model, thinking that it was not the right wing for the task at hand (Duh!). A rather thin asymmetrical section as I remember. Here are a couple of the only pictures I have of the HoB Stang. Never even got the gear doors on it, ..didn't want to "break them" on the first flights don't ya know, ha ha. My "Phoenix Twister" project was next off the board shortly after the Stang wreckage was bull-dozed over. Of course there was no need to call it "Phoenix" at that point it in time, it was brandy new.

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I kind da miss the ole' girl, sniffly sniffly.

1)The wing was too low.

2)The airfoil was too thin.

3)The wing loading was too high.

It was eventually compactified to a pile
of balsa splinters on an outside loop
where it just didn't want to turn at all.

I have the T-6 House of Balsa here now that I built as a 3-line CL'er. Fox 25 powered. I will send pictures if you want. It was a sharp plane. Flew great. It is easy to convert. Basically you will want to watch that you don't get the bellcrank mounted too low. You will need exposed leadouts but they really aren't that ugly. I put my bellcrank about equal to the top of the wingtip, or perhaps 1/4" higher. I'll have to look at it to get more information than that.

I covered mine with silver monokote. Then I painted it blue with lustrekote. A T-6 here has numerous places where the paint was worn off exposing metal. So I could scrape the paint off and make it look neat with the metal showing through!

This is not going to be a real stunter though, so don't expect it. Loops, yes. Perhaps inverted if you are really brave - inside recovery only. It is great fun. Set it up with plenty of elevator!

Play with the balance a lot. Don't let the "wing too low" stuff scare you. Mainly you need the bellcrank in the right place. It is easy, however, to build the plane first the position the bellcrank at about the cg, vertically. Chop holes then run the lines straight out horizontally. Don't forget to put 6 pennies in the outboard wingtip.

Inverted should be okay if all is set up right. It will take some down elevator, but since you'll probably have 30 degrees, it should be plenty enough. My T6 is very light.

2)The airfoil was too thin.

3)The wing loading was too high.

It was eventually compactified to a pile
of balsa splinters on an outside loop
where it just didn't want to turn at all.

I found this posting to be so interesting that I had to do a little research to make sure that we were in the same ballpark. This is HOB kit K-32 W/S 36" has 279 sq in wing area and is for a 061 to 12 RC. The wing is 1 and 3/8" thick and has no dihedral. It has to be thick the equipment goes in it. You obviously do not use the ailerons as they are on a severe taper. The wing sits in the fuselage no higher or lower then any other common profile model
and yes could go to 26 oz with equipment as an RC but probably would never get there if built by a knowledgable builder. Yes they have their share of good builders too. My kit has reasonable wood and not that much has to be replaced.
So a Brodak Jr Flight streak has a 31 inch W/S 230 Sq in wing area weight approx 14/19 oz built, thickness of wing is 1 and 7/16
wing sits exactly the same as the HOB kit. Wood is comparable but a little lighter.
Sig Akromaster 34 in W/S 250 Sq in Wing thickness is 1 and 1/8 wood is average Mine with Fox 15 is 15 oz no movable flaps
Sterling Jr Ringmaster 30" W/S approx 190 sq in area Box weighs a ton for a 15 fox might be 16/20 oz without work, obviously no flaps.
Now my reason for the comparison of all these plane is to see if there was any measerable difference in the standard profile ships to this poor maligned RC offering,which I forgot to say had a fully semetrical airfoil and has fairly decent stunt moments. It is not a short nosed fun fly freak but a nice profile scale plane. The bellcrank will fit in the wing exactly on the c.g the ribs are hollowed out for the leadouts. This is as nice a kit as you'll get with even a nice set of extremely light aluminum landing gear. I figured an OS 10FSR diesel or a fox 15 with a preference to the OS10,it's smoother, is lighter,more fuel efficient, quieter,more versatile prop selection.
So As I started this reply what's wrong with it. I never said that it would be the consumate stunt ship, neither are all the other ones that I mentioned, nor will it push the envelope in any way, but should be fun and certainly have a far better fate then the other plane, and believe me I'm sorry to hear that you
lost yours. But I am certain that this ship will at least be a decent sport plane capable of all the standard maneuvers and should be able to be built no more then 16 oz.
I apologise for getting off the origional intention of the author of this thread

RSM says it was designed by Pat Johnston & Eric Rule, and that's not a bad thing (got a kick out of the big profile GeeBee)but the catalog shot does make the tail area look suspiciously small.

I just haven't seen any on the contest circuit in the South East, or one fly period for that matter, and was wondering why.
One would think it would be very popular...

Any experiences here?

>Mainly you need the bellcrank
>in the right place.
>It is easy, however, to
>build the plane first the
>position the bellcrank at about
>the cg, vertically.

Floyd:

Go back and read Posts # 3 and 11.

Yes, it is desirable to locate the bellcrank near the CG. But the location of the bellcrank will have no effect on the way the airplane orients itself at the end of the lines. The CG will align itself with the leadouts, regardless where the bellcrank is. The bellcrank can be anywhere on the airplane. So bury the bellcrank in the wing and run the leadouts out the tip. This also avoids the leadouts being located above the wing and disturbing the airflow over the inboard wing. (The "turbulator effect" might be OK except the same thing is not happening over the outboard wing.)

The vertical position of the leadouts needs to be close to the vertical CG. Otherwise, the model will fly with one wing high or low depending on the leadout position relative to the vertical CG position. This is why it works to put dihedral in the wing of a low wing model with the leadouts coming out the tip. The raised wing tip gets the leadouts closer to the vertical CG. Again, it makes no difference where the bellcrank is.

Keith

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The airplane as shown in A will fly at the end of the lines as shown in A. The airplane in B will fly at the end of the lines as shown in A. (The leadouts are in the same position.)

The airplane in C will fly with the inboard tip slightly lower than in A or B, assuming all else is exactly the same, particularly the vertical CG.

The airplane in D will fly with the inboard tip raised to an an extreme.

In any of the illustrations shown does it matter where the bellcrank is located. The airplane will align the CG with the leadout position.

Keith

Don't be so sure that you are completely right about the CG just perfectly aligning itself with the leadouts. That is true in theory but in the real world of something going round and round at a pretty fast speed with the leadouts always bearing down on one side of the guides because you routed it this way, I am not so sure. Make it straight through and you will be happier with the plane. I have converted enough RC kits to know better than to believe in these simple theories. FLOYD

You have no idea what you are talking about. Al Rabe, Keith Trostle, Jack Sheeks, Vic Macaluso and others have been doing the bent wing trick for decades with no problems at all. I recently built a civilian version of Darryl Greenamyer's N104RB Red Baron with anhedral in the wing. I listened to Al Rabe's advice and the plane flys perfectly with the leadouts coming out of the wingtip and the cables and bellcrank not in line with the vertical CG. Check out the following photo.

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I have flown this ship at the Brodak and Huntersville meets. Others have flown it and all are very impressed with its performance.

>Your simplistic physics lessons sound clever
>but then, I am not
>the guy moaning because his
>plane doesn't fly right, am
>I?
>
>Don't be so sure that you
>are completely right about the
>CG just perfectly aligning itself
>with the leadouts. That
>is true in theory but
>in the real world of
>something going round and round
>at a pretty fast speed
>with the leadouts always bearing
>down on one side of
>the guides because you routed
>it this way, I am
>not so sure. Make
>it straight through and you
>will be happier with the
>plane. I have converted
>enough RC kits to know
>better than to believe in
>these simple theories. FLOYD
>

Hi Floyd,

You even say above that you are "not so sure" about what you are talking about. Also, I do not know what the relevance is regarding converting RC kits to control line regarding this matter. I do know that I have successfully flown my stunt models with no small amount of wing dihedral in serious competition. I also know that others have as well. Our experience is that the bellcrank can be anywhere without affecting the manner of how the model aligns itself at the end of the lines. Speed of the model will have no affect on how the model aligns itself at the end of the lines relative to the bellcrank position. It is not theory regarding this matter. It is easy enough to make up a test fixture as described below to check out the concept.

Bill Netzeband wrote in his October 1962 American Modeler column:

"....Next time a guy tells you to locate your CG forward of the BC or in front of the lead out, shun him. He don't know the facts. The CG comes first, all else is related to it."

The same thing applies to the vertical CG.

I do not think it is necessary to repeat all that was written before in a previous thread that started in this forum on 29 Apr 02. However, it seems that there are a few here that have not read that. I will provide some of the material that I and others posted.

Bill Netzeband wrote in his Control Line Capers column, American Modeler, October 1962:

"Misconception Blasted. Pictures illustrate that the bellcrank has NO effect on locating the CG. Rather, the bellcrank should be ON the CG to prevent binding (Pic #2). CG will always fall in line with the center of line lead-out spacing ... during flight. Locate your leadouts relative to the CG to produce desired yaw angle for proper tug. ... Next time a guy tells you to locate your CG forward of the BC or in front of the lead out, shun him. He don't know the facts. The CG comes first, all else is related to it."

There are three pictures in this column that show his test rig that represents a wing tip holding the leadout position relative to a fuselage where the bellcrank can be located in different locations. This test rig was suspended by the leadouts. Regardless where the bellcrank was located, the CG of the structure lined up with the leadout position at the tip.

There is another article in American Modeler, July/August 1966, by Walter Williamson. Photographs show an all wood model that appears to have about a 40 to 50 inch span with a 35 size motor. The fuselage looks like a horizontal flat plate based on a crutch assembly to hold the upright engine. The bellcrank was externally mounted on the bottom of the fuselage and could be located in various positions along the length of the fuselage. Williamson ran flight tests with the bellcrank mounted in nine different locations from six inches in front of the CG to ten inches behind the CG. His conclusion was that "It makes no difference where the bellcrank is located. What matters is where the leadouts exit through the guide plate."

In the first installment of Bill Netzeband's series of articles titled Control-Line Aerodynamics Made Painless, American Modeler, July/August 1966, he talks in great detail about leadout position, line rake and bellcrank positions. This installment provides the nomographs to determine the line rake relative to the CG of any control line model based on line diameter and length, model weight and model speed. Bill makes an interesting comment that "If it were possible to mount the bellcrank pivot exactly on the cg and the load of each line didn't change (it does) we could fly without a line guide." Bill also writes of an experiment similar to what he showed in his October 1962 column regarding bellcrank position and representative of the actual dynamics of what goes on when we hook lines onto a model.

The following is from Netzeband's 1966 article:

"For years we were fooled into believing that the position of the bellcrank in the airplane controlled its attitude. Not so. The bellcrank can be almost anywhere in the airplane.

"A simple cardboard outline of an airplane will show this relation. Place an eye (U-shaped bent pin) in one wing tip and tie a pin on the end of a thread. Run the thread through the eye and stick a pin anywhere in the cardboard. Observe how the thing hangs and then move the pin (string end) to some other location. Right! Anywhere you stick that pin, the airplane hangs the same. Now move the eye (line-guide). The airplane assumes some new position. The CG of the airplane will line up with the line-guide. (Note: It would be nice to mount the bellcrank on a line between the CG and the line-guide, because the control lines could lead straight through the line-guide, therefore operating with the least stiffness.)"

On that same thread from last spring, another engineer with no small amount of credibility explained a force diagram in great detail that shows the forces at play with the leadouts, the leadout guide, the position of the bellcrank and the position of the CG. It makes no difference how much tension is being generated on the lines due to the model's rotational speed around the circle. The CG will always align with the leadouts.

Force Diagrams show it. Test fixtures demonstrate it. Actual experience with models proove it. Weight of the model and speed of the model will not change the results here. And I am talking from the experience of successfully competing with stunt models as well as heavy scale models.

As in the previous thread a lot of words have been used to end up saying that it is still best to put the bellcrank as close as practicable to the CG. But the reason for doing so is not to avoid some force that will try to align the bellcrank with the leadout guide. The reason is to minimize the friction of the leadouts at the assumed optimally positioned leadout guides. This friction and wear is negligible. As I stated in an earlier post, the wear on the leadouts has not been a problem. This includes models I am familiar with that have significant wing dihedral and have the bellcrank buried in the wing with over 2000 flights.

Keith

For some time now I have been a little more quiet, but then lately I've realized that when CL, already on its deathbed, is being ruined by the competitive thinker too muchers, the smartsy wannabees, well, somebody must try to make the truths known before we scare off all of the beginners!

That's why I try to make comments to encourage the sport flyer and the common sense flyer. As far as I am concerned, most CL "events" are contrivances, especially that idiotic carrier. Combat is pretty stupid too. Then there is the "pattern," "perfected" by that obsessed man who pretty much was a leader in ruining the true fun of the hobby. Sheesh, that was 40 years ago, and it's still not reached the complete depths of obscurity. With the way things are going, it won't be long now.

With all due repsect, how many of your "RC conversions" have you flown in competition and with what success? Have you scored over 500 points in any expert event with your models? Al and Keith have both excelled at the national and world level with their dihedral aircraft. IMHO, they know what they're talking about.

But...the...same...principles...apply...to...both!

>That is true in theory but in the real world...

Generaly Relativity is true in theory,
and it also works in the real world.

Quantum Electrodynamics is true in theory
and also works to the real world.

Get my drift?

These are much more complex theories than the
"theory" of leadout placement, and they work.

So trust Al, Keith, et al. on leadout placement.

As to anyone who doubts the success of Al, Keith and Vic on leadout position... there are certainly some sited people who are blind!

And don't forget that we can add Paul's B-17 and Windy's B-25 to the group.

While I have to admit that I have always been reluctant to use dihedral, it certainly doesn't hurt and I have a airplane in mind for the future that would be in that category.

Tom N.

I am not trying to beat a dead horse here, but this is for those that just read the above statment by Floyd and did not bother to read the more detailed explanation earlier in this thread.

Floyd, please explain what kind of "trouble" anybody would be "asking for" by not doing what you say.

I am not a "disbeliver". I just know for a fact that the bellcrank location is not critical on a control line airplane. I have examined the force diagrams that even a college student could understand. (So maybe Virgil could help you out here.) I have set up test fixtures that demonstrate this to the satisfaction of myself and others I have shown it to. (Needless to say, it is surprising, so I would suggest you try the same thing before you continue to berate the facts here.) I have researched the model press that shows photographic proof of this. I and others have years of experience of successfully flying a wide array of model airplanes including carrier, scale and stunt that demonstrate this.

There is theory, there are text fixtures, there have been actual flight tests documented where the bellcrank was located in different positions, and there has been years of experience by qualified flyers at the highest levels of competition that prove that the bellcrank can be located anywhere on the model without changing the orientation of the model at the end of the lines. No matter how much the airplane weighs or how fast it flies, the CG will align itself with the leadout position regardless of the bellcrank position. It is a matter of physics which will be the same in Pennsylvania or anywhere else.

So, for a low wing airplane as has been discussed in this thread, unless a builder just wants to lacate the bellcrank in the fuselage, have the leadouts come out the side of the fuselage and over the inboard wing through a leadout guide at the wing tip, he can do so. But he does not need to do so to make sure the airplane does not fly wing tip high or low in flight.

Floyd, if you are so correct, please enlighten us with a force diagram, or an experiment, or some understandable logic, or a demonstration that proves otherwise. Otherwise, you are showing your own ineptitude by claiming all the above is wrong.

Keith

Sometimes we disagree with one another. Sometimes we debate issues (which is the best engine, prop, plane--2-stroke, 4-stroke, pipe or muffler, size, weight, etc.) but we still try to use logic and build upon each other's knowledge and experience. In a lot of areas there is choice, and that is what makes this hobby so enjoyable. You like scale like planes. So do it. Others take a different direction. That's fine.

But when someone refuses to accept proven dynamics and then claims to be the only one with "smarts" and then promotes totally false concepts and ideas, some of which are even dangerous, that's it. He doesn't like the hobby the way that it is. We will enjoy it without him.

Leonard Neumann

I'm sorry these topics end up the way the do sometimes. But I gotta' say thanks to those that put the time in, repeat old news, and try to hammer some new knowledge into the available gray matter I've got left. I'm just a little nervous about what might be being pushed out the other side as the new stuff is going in is all. As I see it, these little revelations do nothing but expand on the knowledge base we all have to play on. With what has been explained here this week I'm thinking a whole new area of c/l may have opened up. More room to try something different perhaps. I can be a little slow on the up take sometimes, so thanks for using a bigger hammer. The light does finally go on for some of us. Maybe later then sooner, but it does go on. Mucho grassya'ss gents.