outacontrol41

My Feedback: (9)

Okay, I just got my incidence meter out to see how my plane stood in this matter. I bought my plane mostly built and in bone stage. The wings were already built and set up (prebolted) to carbane struts, etc. My top wing reads 3.5 positive and bottom wing the same. According to Jack I must take the top wing off and somehow lower the front half about 2 degrees for a better flying airplane. This is more than a simple chore. Is it practical for me to do this after everything is alredy built and assembled?
I have flown it and had to add down trim. However, according to Cybertom, he seemed to fix his simular problem way back by adding some down thrust. At least according to him, his plane flew better. According to Jack, this makes the original problem worse....or "compounds the problem". I have added some down thrust with washers but have not had the plane in the air since then to find out the difference if any. At this point I'm a little confused. Who's right? Would more propwash against the top wing do more harm than good?
P.S. I'm not trying to pit you guys against each other again...just trying to find out if it's really worth the trouble to adjust my top wing.

stearman65

mmmmmmmm

chasrb

Hi Jack no problem waiting, the incidence you mentioned/recommend I will use, I am sure it'll work well.

From a still in construction standpoint...since you have drawn/built/flown your own design I wanted to see how you mounted the center section cabanes. As I mentioned in an earlier post I am replacing the original Flair bar cabanes with aero tube ones and I wanted to see how you did it.

I don't think I have flown 900 hours period, Jack your flight time is amazing!

jack1933

My Feedback: (2)

HI Chas This may help till I can get the details you wanted downsized. My cabanes are 2024 t4 aluminum, covered with balsa, shaped and covered with whatever covering you use. They are attached to plywood reinforced doublers at the front inside the fuse box with 2 ea. 10-24 bolts, into t nuts, the rear are the same, except 1 bolt, the tops of the cabanes are attached to the top center section, and recesed into the root with 10-32 flat head bolts into t nuts. The only reason for the difference in bolts is, they were what was on hand, actually one should use coarce threads in soft metals, and fine in steel, either will suffice in this application. As you can see from the picture, the wing slides onto a 2024 aluminum pipe with .049 wall, and the wings are held rigged, with flying/landing cables attached, then a jig was constructed, using the pipe holes, and the antirotation pins, as anchoring points while the wings are off the plane. Takes about 3 minutes to put the plane together at the field. Assumed that a similar system is used on the Flair model. Will get some copies of the info you requested today. the landing gear is also 2024-t4 aluminum, the reason is: 2024-4 is about 2 times stronger than 6061-t6. Later

jack1933

My Feedback: (2)

Greetings to all reading this thread My phone number is 580-276-5322 am usually up at 7 am and off to bed at 12 pm cst plese call if anyone has any questions about how my plane is rigged. Have the unlimited call plan, so i could call you back, with gas going up every week, this might help, because some of the data takes a little time to explain. Regards to all Jack Strickland

Cybertom

outacontrol41,

The down thrust was NOT to correct for the incidence of the upper wing but to account for the thrust of a 10HP Robart R780 swinging a 24x12 prop at slower speeds. The thrust angle changed the attitude of the airplane as it came in for landings (decidedly nose up). At slow speeds the wings are less efficient and engine thrust has a much greater effect. The thrust angle of my engine was causing my Stearman to come in nose up as you can clearly see in the video.

[link=http://rcuvideos.com/item/MW84D0D76TB37G71]Landing Video (Not Enough Down Thrust)[/link]

Cybertom

Everyone,
Before this gets out of control it would be a good idea to establish a base of understanding and terms that we all agree with. I pulled this information off of the web. In addition I have attached a PDF document with good fundamental explanations of the terms being used here.

WHY USE TWO WINGS?
When biplanes were first invented, two wings were used more for strength than for any aerodynamic reason. Even though a biplane has twice as much lift-generating surface as a monoplane of the same span, it carries with it a big increase in drag. Using two wings, however, gives aircraft designers an excellent format in which to produce very strong structures. This is because struts, rigging and flying wires support and tie the two wings together, much as girders and beams strengthen a truss bridge.

WING STAGGER
Biplanes have three basic wing arrangements: unstaggered, positive stagger and negative stagger. Many early designs, such as the Wright Flyer and the Spad, have an unstaggered arrangement in which the wings' leading edges are directly over each other. As long as the gap between the two wings is wide enough, this arrangement is very acceptable aerodynamically. The more typical Stearman, WACO and Fleet biplanes have positive stagger: the top wing is positioned forward of the bottom wing. This produces a slightly milder stall characteristic than the unstaggered arrangement. In comparison, the unusual Beechcraft Staggerwing with its negatively staggered wings has a slightly more pronounced stall break.

INCIDENCE
Incidence is simply the angle between the airfoil (wing or tail) chord line and the longitudinal axis of the aircraft. So what does it buy us to increase wing incidence? It gives us more lift at a given speed. If I lower wing incidence I will need to fly faster to achieve the same lift. If you reduce the incidence on the upper wing know that you will be reducing your ability to fly at slower speeds. Also your airplane may now have a tendency to dive instead of climb unless you adjust the tail incidence to compensate. Remember it's a balancing act. In relation to the Flair Stearman I think this was a scale flight performance decision. The designer wanted the Flair Stearman to fly at slower scale speeds without falling out of the sky.

DECALAGE ANGLE (BIPLANE)
"Decalage" when refering to biplanes is the difference in the two wing incidences or their angles along the chord line relative to each other and to the fuselage centerline. A positive decalage gives the top wing more incidence than the bottom wing. Negative decalage occurs when the bottom wing has more incidence than the top. Most positive-stagger biplanes (top wing forward of the bottom wing) have positive decalage. In this arrangement, when the top wing stalls before the bottom wing, it causes the model's nose to drop for a natural recovery. If the bottom wing were to stall first, the effect would be to raise the nose, creating a more pronounced stall break.

Examples:
Full Scale Stearman (Charsb Manual)
4.0(upper wing) - 3.0(lower wing) = +1 degree decalage

Flair Stearman Kit
3.5(upper wing) - 3.5(lower wing) = 0 degrees decalage

Jack1933 Stearman (scratch built)
1.0(upper wing) - 3.0(lower wing) = -2 degrees decalage

DECALAGE (MONOPLANE)
"Decalage" when not refering to biplanes is the angle of difference between the chord lines of the wing and horizontal stabilizer. This is often cofused with the term incidence which is the angle between the wing and the stabilizer in reference to the fuselage.

outacontrol41

My Feedback: (9)

Thanks for explaining that Tom. I'm going to fly her first to see how she handles. Check out the review (portions of the first and last pages) below and note that the reviewer needed a lot of down trim to manage level flight. What's your opinion of this?

Cybertom

I am in the same boat as that reviewer. Both of us built the Flair Stearman according to the plans and not the updated information on the Flair website. If I would have checked the website and used 3.5 degrees of tail incidence I would not have needed all of that down elevator. It's pretty simple, most of us followed the instructions that came with the kit and didn't think to check the website first for updates.

outacontrol41

My Feedback: (9)

Oh, Good grief!! Look what I went and did. I went and bought another one of these kits only this time it's further along in the build. Both wings and tail section covered with yellow Solartex, the fuse only built. Not sure if this kit will come back to the market so I snatched one as soon as I could.
I'm working on a 1/4 scale Piper Pawnee cropduster now, then a scratch built Ag Cat biplane (90'' ws) then finally this new stearman. Should be more fun the second time around even if it will be gotten to at some point next year.

Cybertom

Looks like 2-tanks?

outacontrol41

My Feedback: (9)

Two tanks - correct. I could plumb both into one line to carb or make one an oil tank for smoke....haven't decided yet. Got some sheeting to do as well as all the other stuff like attach lg and wing supports. Payed a very, very reasonable price for it.

outacontrol41

My Feedback: (9)

I mispelled "sheeting" and almost made that word something else! [X(] I'd better watch what I say on here or I may cause a stir and lose my job! lol

geoardsog5

My Feedback: (31)

I think cybertom has pretty nailed it as far as defining the terms and rules that biplane riggers live by. Personally I will split jack1933's decalage numbers in half and and rig the bottom wing to +3 degrees and top wing to +2 degrees-test fly and see what happens. I'll let you all know the results. I realize it's a lot of extra work, but biplane builders might consider imbedding 4-40 threaded rod in the cabane and interplane struts and using Dubro # 302 threaded rod ends to attach them to the wings and fuse structure. By screwing the rod ends in or out, wing incidence can be set very accurately. I have used this method on a 1/4 scale Fleet biplane and Davis D1W with much success. Good luck to all with the Stearman projects.

Cybertom

Geoardsog5,

That's sounds excellent. Basically you can perform a controlled experiment. If you can document the different configurations you try and evaluate the results and present them here that would be awesome!

I have a request. I am especially interested in the stall behavior in relation to the incidence of the upper wing. According to the information I found decreasing the incidence of the upper wing should make stalls more abrupt. Increasing the incidence of the upper wing should reduce the stall break effect. There also should be an increase in aerodynamic drag as incidence increases.

How do you plan to adjust the stabilizer incidence to compensate for the changes your making up front? You might need to adjust the elevator trim to make up for a fixed stabilizer.

This makes me wonder if the guys over in the Aerodynamics forum have done any testing like this. I'm sure they would have a few things to contribute. If this topic eventually starts to turn into a doctoral dissertation on aerodynamics, we should move this topic to a new thread over in the Aerodynamics forum. I don't think we are anywhere close to that yet but we have to keep in mind that if we go far outside the boundaries where this information will not help other Flair Stearman builders we start to do an injustice to the purpose of this thread.

waldo

Hi guys. I 've been following this thread with interest. I would advise caution in reducing top wing incidence below that of bottom wing value. I am currently flying a Brian Taylor Gladiator with positive decalage and it flies fine. A Tiger Moth model I once flew had a similiar setup. Many years ago I tried to improve the flying qualities of a Sterling Stearman which I recieved second hand. It was rather heavy and flew reasonably well but the top wing incidence was much greater than the lower. I reduced this to near the lower value, the model flew wll enough until near the stall where the break from the stall was much more abrupt and eventually led to the demise of the model stalling going downwind on a windy day. I have the Flair Stearman but have not yet started the build. The kit dates from spring 2004 by which time the tailplane incidence had been altered in response to queries regarding the amount of downtrim required.

jack1933

My Feedback: (2)

Hello all you Stearman nuts Im so sorry for coming on here and causing confusion, apperantly the positive upper wing, regardless of what has been tried and proven, at least in theory, is what most of you want to believe, which is certainly your right. Tom the term "out of control on this forum, is hardly what is happening. Thought we were getting along quite well. Guess I was wrong. Exchange of information is always a healthy thing when we are expermenting with MODEL AIRPLANES, which do not respond to the same size air molecules as full size planes do. Good luck and flying to all. Will not be responding to this forum any more. Regards to all. Jack

Cybertom

Jack1933,
I too thought everyone was getting along well on this topic so I was really caught off guard by your response? I didn't mean anything by using the term "out of control" other than I found all of the little pieces of information confusing so I tried to put them all together. I also figured that not everyone here is completely familiar with all of the terms being discussed. Personally I was astounded to find out that when referring to biplanes that decalage had an entirely different meaning than when discussing monoplanes. We were talking about decalage for quite a while but never used the correct term.

I am a computer guy by trade. I manage and maintain over 250 servers and 2,500 workstations worldwide. When confronted by lots of information in the course of my job I tend to break it down into understandable chunks. When I have my facts straight I can put the big picture together and figure out what's going on. That's all I was trying to do was figure things out as are many who participate in these forums.

Don't take the information I found on the web personally. If you disagree with it present your own sources that backup your opinion. Isn't that the way professionals work? Last I knew not all Scientists agree on everything. However, I think you would agree that it should be possible to pin down the truth when it comes to this subject because aerodynamics is nothing new. I will be more than happy to recant every piece of information I posted here if someone can prove it's wrong. I posted what I posted because those are the facts I'm finding. I even bought the book "Model Aircraft Aerodynamics" which I am currently pooring through to figure this out. I'd be a poor Scientist if all my research was based on opinion only. We need to make sure that we are backing up our opinions with facts for the sake of all who read this thread and are looking for answers don't you think?

I for one will be disappointed if you choose to stop contributing to this thread.

Cybertom

Waldo,

I want to party with you man! You fly a Gladiator!!!

PS,
My wife is Irish!

waldo

Brian Taylor Gladiator is 56in span, 10lbs, OS 65LA and 1lb of lead up front. Colour scheme is Irish Air Corps 1940.

Cybertom

Absolutely BEAUTIFUL!!!

I know the color scheme. I bought about every book on the Gladiator that exists. If you read some of the earlier threads my self imposed challenge for 2008 is to design my own 1/3rd scale Gloster Gladiator. Those BIG gas radial engines are all the rage and thier too big for anything smaller than 1/3rd scale. I have never built anything that big so I am looking for good 1/3rd scale design that I can adapt to create my Gloster Gladiator.

They are making good progress on the Gladiator the "Fighter Collection" is restoring at Duxford. Also a photo I took of the instruments by reaching my arm inside the cockpit:

waldo

1/3 scale Gladiator will be some aeroplane. Good luck with research and drawing. The Duxford build I am familiar with, I get over there about once a year. I have seen the Old Warden machine fly and it is a joy to behold. Anyway back to the thread subject. I mentioned some time ago here that I thought that the undercarriage legs on the Flair Stearman gave what I thought a high sit on the ground, suggesting perhaps that the legs may be too long. I recently discovered that I can get access to a Stearman to measure so I wondered what you guys think of these dimensions when scaled down by 4.3 for the Flair model. I haven't started my build yet so would appreciate any comments on leg length and wheel/ hub diameter. The 38ins is from the inside edge of the leg fairing to the centre of the axle. Has anyone changed the wheels for 6in and better thread pattern.

chasrb

Waldo, if you go back in this forum you'll see where I changed out the stock Flair mains for Robarts. I used the set for the Ziroli 87" Stearman, the Flair is only a couple inches different.. I can adjust the height should I want. They are lower then the stock Flair in my current setup. Post 376-377 to be exact.

Thanks for the drawing...

BTW Both Cybertom and I use the Glennis AT-6 wheels instead of the stock Flair wheels....the pics are in this forum

jack1933

My Feedback: (2)

Tom Thanks for your reply. As i stated in several posts " my experence with Stearmans and other biplane, models , the + 2 negative in the top wing worked best for me, and the stall is certainly not abrupt". If anyone wants to try other setups, by all means proceed, never said my set up was perfect, just that it works very well, and no down elevator trim is required at any flying speed, I think if you would stop trying to prove me wrong with full scale info, we could get along quite well, apples to apples so to speak. If you would just admit that you are having to have down trim in your elevator, and ask why, on this forum, you might come up with some answers. As I stated in the begining " I got on this forum to be of some help" with trim problems i felt certain you fellows were having. You on the other hand seem heck bent on getting your point across, regardless the outcome. I feel this kind of response is uncalled for. Please do not contact me again on this matter. Thanks Jack

geoardsog5

My Feedback: (31)

Cybertom,
Based on my studies and recollections of over 35 years ago, given a positive stagger biplane with positive decalage, the upper wing will almost always stall before the lower wing - resulting in a momentary rearward shift in the the center of lift, causing the aircraft to pitch down sharply. I'll have to see what current factual information I can find to support this theory. I haven't figured out yet what I'm going to do about horz. stab adjustments to compensate for less positive incidence in the upper wing. BD Stearman #1 is built and ready to fly- I can shim the cabanes and interplane struts to adjust top wing incidence but can't do much to change horz. stab. BD Stearman #2 is in the building stage and will have an adjustable horz. stab.
Cybertom, you may be correct in stating this discussion needs to move to the aerodynamics forum. If we can"t come to a factual and definite conclusion on the wing incidence dilemma, nobody will benefit.You would think aerodynamics is a fairly exact science by this point in time.There sure seems to be a lot of differing opinions out there, even from the scientific community.
Based on some of the posts in this thread, The Flair Stearman does seem to have some pitch trim issues I must say , I'm trying to gain knowledge here to head off similar problems with the BD stearmans. My problem is there are not too many BD Stearmans flying or being built, so I have to try to get information wherever I can.The Flair and BD Stearmans both appear to be very scale- flying characteristics should be similar.