RE: Flair 1/4 Scale PT-17 Stearman Review  
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    • All Forums >> RC Airplanes >> Giant Scale Aircraft - General >> RE: Flair 1/4 Scale PT-17 Stearman Review
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    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/13/2007 7:32:58 AM   
    outacontrol41


     

    Posts: 1268
    Joined: 11/27/2004
    From: Girdletree, MD, USA
    Status: offline     		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.

    (in reply to geoardsog5)
           Post #: 601

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/13/2007 1:21:07 PM   
    chasrb



    Posts: 953
    Joined: 1/12/2003
    From: Warrenton, VA, USA
    Status: offline     		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!

    _____________________________

    Chasman

    (in reply to jack1933)
           Post #: 602

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 2:31:12 PM   
    jack1933


     

    Posts: 182
    Joined: 1/31/2004
    From: marietta, OK, USA
    Status: offline     		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

    (in reply to chasrb)
           Post #: 603

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 2:56:36 PM   
    jack1933


     

    Posts: 182
    Joined: 1/31/2004
    From: marietta, OK, USA
    Status: offline     		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

    (in reply to jack1933)
           Post #: 604

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 4:08:09 PM   
    Cybertom



    Posts: 545
    Joined: 12/2/2002
    From: Streetsboro, OH, USA
    Status: offline     		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.

    Landing Video (Not Enough Down Thrust)

    < Message edited by Cybertom -- 4/15/2007 6:42:56 PM >

    _____________________________

    Real airplanes have 2-wings and round engines!

    (in reply to outacontrol41)
           Post #: 605

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 4:27:37 PM   
    Cybertom



    Posts: 545
    Joined: 12/2/2002
    From: Streetsboro, OH, USA
    Status: offline     		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.


    Attachments
    Click to see the file in new window.Attachment.pdf


    < Message edited by Cybertom -- 4/14/2007 10:39:15 PM >

    _____________________________

    Real airplanes have 2-wings and round engines!

    (in reply to Cybertom)
           Post #: 606

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 5:45:17 PM   
    outacontrol41


     

    Posts: 1268
    Joined: 11/27/2004
    From: Girdletree, MD, USA
    Status: offline     		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?

    Attachments
    Click to see fullsize image.
    Click for fullsize

    (in reply to Cybertom)
           Post #: 607

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 5:52:22 PM   
    Cybertom



    Posts: 545
    Joined: 12/2/2002
    From: Streetsboro, OH, USA
    Status: offline     		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.

    _____________________________

    Real airplanes have 2-wings and round engines!

    (in reply to outacontrol41)
           Post #: 608

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 5:56:31 PM   
    outacontrol41


     

    Posts: 1268
    Joined: 11/27/2004
    From: Girdletree, MD, USA
    Status: offline     		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.

    Attachments
    Click to see fullsize image.
    Click for fullsize


    < Message edited by outacontrol41 -- 4/14/2007 6:04:03 PM >

    (in reply to Cybertom)
           Post #: 609

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 5:57:40 PM   
    Cybertom



    Posts: 545
    Joined: 12/2/2002
    From: Streetsboro, OH, USA
    Status: offline     		Looks like 2-tanks?

    _____________________________

    Real airplanes have 2-wings and round engines!

    (in reply to outacontrol41)
           Post #: 610

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/14/2007 6:08:25 PM   
    outacontrol41


     

    Posts: 1268
    Joined: 11/27/2004
    From: Girdletree, MD, USA
    Status: offline     		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.

    (in reply to Cybertom)
           Post #: 611

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/15/2007 4:35:06 AM   
    geoardsog5


     

    Posts: 25
    Joined: 1/8/2005
    From: Tinley Park, IL, USA
    Status: offline     		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.

    (in reply to Cybertom)
           Post #: 612

    RE: Flair 1/4 Scale PT-17 Stearman Review - 4/15/2007 5:00:07 AM   
    Cybertom



    Posts: 545
    Joined: 12/2/2002
    From: Streetsboro, OH, USA
    Status: offline     		Geoardsog5,

    That's soun