yel914

This adjustable stabilizer idea is looking better and better!

ChrisMH

Turn the incidence meter around. Then positive is up.

The meter reads according to how you use it. Positive is up regardless.

Capt Jim

My Feedback: (168)

Geee, I always thought positive wing incidence was...leading edge UP!, and it has always worked for me.
I'll bet that if you attach that incidence meter to the wing on the opposite side of the fuse....looking at the same meter from the other side...then it would read toward the positive side of the Robart meter.

bart5495

With regard to Incidence on the Stablizer. The stablizer is treated the same as the wing. Leading edge up then you positve incidence.http://www.robart.com/how_to/incidence_meter.aspx

Doug
WACO Brotherhood #11

Hughes500E

My Feedback: (16)

OK, this has been a test, everyone is alright and we can resume normal building.
You all passed

flyguy888

My Feedback: (63)

At first I felt kinda stupid when I first brought up this incidence thing because I did not understand it that well. You have all made me feel a whole lot better about not being sure about this matter. After all I have read it seems that the incidence of the stab is proper if it is a degree or so in the direction that causes the plane to pitch down in flight.

flyguy888

My Feedback: (63)

Changing my incidence is not that tough, even with my plane built. I have access to my tail feathers
A long time back in the thread I described bolt on tail feathers. This might be good to revisit for new members. I added 4 hardwood blocks under the stab seat in the fuse and inserted 4-40 brass screw-in inserts. The fin is glued to a base. (4) 4-40 SHCS through this base holds the stab down solid.
As my planes get bigger I want to be able to take them apart for service, just like real airplanes. All my control surfaces and hinges are removable also. I try to avoid making a permenant assembly of something I may want to take apart down the road.
Note that my servos are also in the rear. This makes for very good control response by getting rid of long rods. You can also see your entire linkage layout at a glance. No hidden mysteries. Added very little weight, and this plane can be nose heavy anyway depending on your choice of engine.

skylarkmk1

Hughes500E,

I would not get all paranoid about the incidence. This plane, when built according to plan, has flown and flies well (look how many stickbuilder has built). If it did not fly well, I don't think stickbuilder would have repeatedly built more.

Lets try to define things so that we are all on the same page. I am not an aeronautical engineer, but that was my major in college and the following definitions are my own.

Incidence - A method of determining the angle, measured in degrees, of the wings, stabilizer and thrust line in relation to a reference (or datum) line through the fuselage. Wings and stabilizers are measure through the cord of the wing, thrust line is measured through the center of the crank shaft. Positive incidence is having the forward end (or leading edge) of the cord further (or a positive amount) from the reference line than the aft end (or trailing edge).

Cord - A straight line through the leading and trailing edges. On a flat bottom wing, it may give the illusion that the leading edge is down. Do not confuse the cord line with the bottom of the wing, they are not the same.

Stabilizer Incidence - Use to trim the aircraft to neutral elevator, no up or down elevator deflection in level flight. It also affects how the fuselage "flies". In other words, whether the fuselage flies tail low or tail high. Positive stabilizer incidence will "lift" the tail of the fuselage

The Robart Incidence meter, when clamped to the wing will measure the cord angle in referenced to the fuselage centerline. This next will sound elementary to some, but is not inttended to insult anyones experience.

Level the fuselage and block it to prevent movement. Measure the incidences on both side of the wing and stabilizer, they should match. Adjust them until they are equal on both sides. On the Pica WACO YMF, the plans call for 0° on both the top and bottom wing and 2° positive on the stabilizer. This will look like the leading edges of the wings are lower than they should be with the fuselage level. The Robart directions supplied by bart5495 spells out the "how to" and definitions.

As Hughes500E said, enough talk and lets get back to building.

khodges

My Feedback: (1)

Tailplane incidence does affect how the fuse "flies", but more importantly, fine tunes the main wing's angle of attack in level flight to maintain straight and level at a given power setting, hence why it is adjustable, for "trim". Any airfoil has an optimum "neutral" angle, where it makes enough lift to maintain flight at a certain airspeed. As airspeed increases or decreases, the angle must be adjusted to keep the plane in proper pitch trim. Wing incidence is set on the aircraft so that at a "design speed' the fuselage is at an optimum orientation to the relative wind to minimize drag. When all this is tallied, in aircraft specs, the most efficient cruise speed in terms of fuel consumption occurs when the plane is at its optimum trim.

Stickbuilder, here's a couple more pics of the ailerons, edge on. I trimmed the skins flush with the wood edges, and may fill the leading edges of the corrugations, but may leave the trailing edges open. I will finish the exposed wood parts of the ailerons with epoxy finishing resin.

I used 3M High Strength 90 spray adhesive to bond the plastic to the wood. Use it like any contact cement, but the adhesive carrier will soften the plastic, so once stuck down, let it sit until the glue is dry, or finger pressure will leave marred places in the finish. This glue is very aggressive, so not much is needed, but it is best to join the pieces fairly soon after spraying the adhesive (within 30-45 seconds) to allow any repositioning of the piece (and you'll not be able to reposition much, anyway). I have some waviness, but it looks like several planes I have seen with ribbed surfaces, none of them are perfectly smooth.

I guess I am doing more of the details from the Classic WACO, but those are the pics I have with the best resolution and detail. The ribbed ailerons just add something else to grab the eye, as does the counterbalance on the rudder. The Classic is the only YMF/UMF that I've seen with it, and not even all of them. I have also noticed that some planes have more metal skin on them than others. I am just doing what suits me to make my ARF look different from any other I might run into at the field; I am sharing my reconstruction pics for anyone who might be interested in any mods to their own, and to show that you can take a fairly plainJaneplane and make it fairly detailed with a little effort.

There's a quote from Bob Walker in this month's (March) issue of MAN that I feel I am fully in the spirit of showing to others. The question put to Mr. Walker (founder of Robart) was "What do you see as the future of our hobby? Do you have any concerns regarding the hobby and the r/c industry?"

His answer was "ARF models have spawned a new generation of talented fliers, but we need to turn these guys into MODELERS [my capitals] A way to do this is to show them how to first modify ARF's and then get them to build kits.........."

I think he is right on, and this is why: the novice r/c'er with talent but no building experience opens a big box of balsa and is daunted by the thought of making that box of wood into a flying machine. he worries that he'll spend a lot of time and effort and the result will be something that A) looks like s**t, and B) flies like s**t or not at all. Starting off with something that's pretty much put together for you, and then making minor changes that won't really affect how it flies can give you experience and encouragement to tackle more complex things. And this is the guy down the road that will love you guys for keeping a classic alive that he can build from scratch one day., because you've worked to make both plans and direction available.

Nightstalker

ronj10 - How do you do your removable hinges / control surfaces? Just curious as I've not seen or read about this before, or likely can't remember having seen or read about it

flyguy888

My Feedback: (63)

For removable hinges I use regular plastic flap hinges, and install them as usual into slots.
Then I drill a small .05 hole through the top of the entire control surface and through the hinge and install a single 2-56 wood screw into each side of the hinge. One on the elevator side and one on the stab side for each hinge, for example.
That platic is so tough it will not rip. A single screw is enough.
I do add a piece of reinforce wood behind the square wood edges the same thicknees as the control surface so that the entire hinge is encased. That way the screw has a solid seat at the surface and will not pucker the covering material.
Very easy to see, maybe hard to explain.

skylarkmk1

Hey stickbuilder,

Is the following anywhere near you?

2007 Sun'n Fun Fly-In in Lakeland, Florida, April 17 - 23, 2007
Lakeland Linder Regional Airport

From the WACO Classic Restoration Company, http://www.wacoclassic.com/

Stickbuilder

Yep, sure is close by. I'm about one hour north of Lakeland Linder (notice I said one hour, not stated in miles) In Florida, one does not dare state distance in miles, due to the overflowing of snowbirds, blue hairs, rednecks and others who clog the roadways. You may actually be 30 miles away from your destination, but you may need to state the distance as 2 hours away. See how it works? I get down to Linder quite often, since it is the site for Florida Jets, Top Gun, Sun'nfun, and quite a bit more. Lakeland is in Polk County, I'm in Lake County, and we adjoin Polk County on it's North border.

Bill, AMA 4720
WACO Brotherhood #1

Stickbuilder

I built my hinge plate and control horn for the adjustable stab last night. It should work extremely well. It is extremely rigid, and does not require a lot of monkey motion to make work. If you will recall, my original statement was that I wanted to make the model fly level at cruise without having to add elevator trim. I feel that the adjustable stab will allow this. It will require some testing to arrive at the correct amount of incidence for landings. I wish that there was a progressive linkage available for servos that would enable us to utilize actual trim tabs for the trimming of the model, and as control deflection was made, the linkage would pick up the control surface and move it. It would require some expotential being built into the linkage, somewhat like the old 3 deuce carburetor linkage that we used to use. One of you super engineers think about that one.

Bill, AMA 4720
WACO Brotherhood #1

Bill, AMA 4720
WACO Brotherhood #1

old git

I really wish I had a drawing to refer to. The norm for a free flight model is to have what is sometimes called LONGITUDINAL Dihedral. The LEADING edge of the wing is set UP relative to the stabiliser which has the TRAILING edge UP relative to the wing. Make a chuck glider, glue the wing direct to a stick and put +ve incidence (packing under the leading edge of the stabiliser) and try to fly it. I assure you it does not work. A pattern ship with symetrical wing and stab' will not remain in the air without up elevator if flying upright or down elevator if inverted.

N.B. A wing with a flat underside and convex top surface has +ve incidence relative to the surface it is mounted on. Sorry I can't upload pics to illustrate the situation but the flat underside has caused many to have a false idea of the incidence.

N.N.B. The measurement of incidence is usually made with reference to the DATUMN LINE, if there is no datumn on the drawing it becomes a problem using angles of incidence.




old git - - - - - - -aka John L.

WACO Brotherhood No. 14.

WacoOne

My Feedback: (3)

Positive incidence is with the leading edge up. If you turn your Robart incidece meter around 180 degrees you will find it is reading the same number in the + range. It's all in which way you position it on the wing/stab. The crutch is parallel to the thrust line. If it is level then the fuse is not nose down. When I set my YMF up, I leveled the crutch and found that the bottom wing had 2 degrees of positive in it. I had to raise the trailing edge up about 5/16" to get zero. This was quite a job since I had to chop away at the wing saddle to accomplish this. The stab had one degree of positive so I raised the leading edge up to attain 2 degrees positive. My firewall has 1/2 degree of negative but I will shim the engine mount a small bit to make it also parallel to the crutch line.

Bill Hogue
WACO Brotherhood #21

Sorry. I wrote this response before I had read page 61 of the thread. I see that this pos/neg issue has already been addressed satisfactually.

skylarkmk1

To all,

Too bad that this is not a bit cheaper (by a few thousand), lighter (5 lbs) and shorter (2-5/8�), it would be the ultimate scale engine for the 1/5th scale WACO YMF. Y= 225 hp. Jacobs engine.

http://www.robart.com/R780/r780tech.aspx

Oh well, my pockets are not that deep.

skylarkmk1

WacoOne,

Thanks for explaining what you had to do to your model to make the incidences conform to the plan. A lot of work cutting the saddle. Was your plane built from a kit?

Hughes500E

My Feedback: (16)

I'm looking at doing the same thing. With my stab at 2 degrees positive and my wings at 0; the fuse is nose down []

I'm going to have to remove the tail and adjust the saddle.

flyguy888

My Feedback: (63)

Explain why you are changing your plane. The 1/5 YMF plans show zero wing and 2 deg positive stab.
Are you saying that your tail and wing are in right relation to each other but not to the crutch?

WacoOne

My Feedback: (3)

Skylarkmk1

Yes, my plane is from the kit. It was built exactly per the plans and instructions but the incidences were off. I studied the situation for days trying to figure out what why it came out this way and could not determine any deviation from the plan by looking and making measurements. I even showed it to a couple of 'scale builder' buddies and they were also dismayed. So I decided to attack the wing saddle to make it right. Fortunately I didn't need to mess with the hardwood wing mounting blocks so it worked out okay. I am wondering why this problem has not cropped up before considering how many of these kits have been built.

Regarding the Robart radial, I saw Nick Ziroli at Top Gun a couple of years ago with this engine on his 77" Stearman. It ran and sounded great! Only way to build a Stearman.

Bill Hogue
WACO Brotherhood #21

Hughes500E

My Feedback: (16)

Yes, the stab the wings and the engine are all perfect but the fuse is not level, it is nose down!
Probably not what most would call real bad !

flyguy888

My Feedback: (63)

Well, it would appear your airplane will have a very humble posture.

WacoOne

My Feedback: (3)

If your fuse is nose down with the wings at zero incidence then you have positive incidence with the fuse level. That's the same problem I had. The fuse (crutch) should be level first and then check/set the wing incidence. That's why I had to raise the trailing edge of the wing to get zero. I'm sure the plane will fly like that but I wanted to get mine exactly right.

Bill Hogue
WACO Brotherhood #21

Hughes500E

My Feedback: (16)

Exactly, my wife says I'm nuts, it looks good.

It has to be exact!

7/8 of a degree is actually quite a bit [:-]