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Thread: WACO YMF


  1. #15901

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    RE: WACO YMF

    Hi Barry,

    very nicely built. I would be also interested in the removable tail feathers, it looks like as if they are removable. Please let us know the solution how you manged this. Don't forget to add the rigging wires they are necessary for the static strength of the ship. Original tubes and surrounding structure will not carry the flight loads without rigging wires.

    Peter
    Waco brother #170

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    RE: WACO YMF

    Barry,.

    Awesome looking model!

    Did the vinyl graphics come with the thin black stripe around them? How did they go around the cowl blisters? They look very nice and sharp! About what did your graphics cost and do you have a link to their web page?



    Ihave one question for Peter Barth: Why did you go with a symmetrical airfoil when the full scale used a modified Clark-Y? Just curious.

    Joe

    "When you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."

    AMA # 8870, Member since 1978.
    Waco Brotherhood # 219.

  3. #15903
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    RE: WACO YMF

    Chuck-
    Balance – depends on where you want to balance it.Based on the description in the Waco kit’s documentation (nothing shown on the plans), it sounds like they’re saying to balance just in front of, or on, the rear cabane struts.To balance at that point would require about a pound of weight at the tailpost.However, that point seems a bit rearward to me (tailheavy).Based on the ‘old school’ method for figuring the CG of a bipe – well explained in this link http://www.modelairplanenews.com/blo...cing-biplanes/ that point calculates to a CG at about 38%.
    I checked at about 30% (using the method in the link) – that’s about 2” in front of the rear cabane mount.Balance just barely tail-down at that point.Compared that point to the CG noted on the Pica plans for both the 1/5th and 1/6th scale Wacos – their CG is in about that same relative location.Same with the GP ARF Waco…. And all of those fly fine.So for now, it’s balanced at that point… worst case it’s a little nose heavy (compared to the documented location), so I programmed in a 3rd flight mode with a little extra up-elevator – just in case.
    WacoNut –
    Thanks – I like the panels too!The new “glass panel” Waco’s are fine, but I wanted to model mine more like a 30’s-style Waco well taken care of and still flying today.So the panel design I came up with is kind of a composite of several different older Waco’s I found photos of.Scratch built.Instrument faces came off of Chief Aircraft’s ‘full scale’ side of the business – lots of nice HD photos of available instruments – everything from modern to classic – picked the ones I wanted, reduced to the size needed, and high-resolution printed on photo paper….. sure beats the “old days” of a few years ago when a Xerox was about the only tool we had to work with!The rest is sheet plastic, some plywood, and a bunch of ‘fiddly-bits’ from around the shop.Fun stuff!
    Peter –
    No, the tail feathers are not removable.Although I don’t think it would be that hard to make them removable.I did modify the attachment method some, and the means of setting the incidence….. basically I’d add/remove shims to adjust the incidence, but I figured once it’s set and ‘verified in the air’, there really shouldn’t be a need to change it.And instead of using 2 ply ‘retainers’ for the rear of the stab I madeup a single laminated retainer the full width of the fuselage at that point…. So make that ‘bolt-on’ instead of glue on, and the stab would be removable.As far as how to get it out from under the fin…. Fin and rudder would also need to be removable, but that wouldn’t be that difficult to do either.
    Dash7ATP –
    Vinyl graphics are from Kirby’s Kustom Vinyl - http://www.angelfire.com/oh2/kirbysgraphics/index.html - Been in the business quite a while and is awesome to work with.Pinstripe – yes and no – Kirby does his vinyls in layers, so there were black vinyls to apply first, then the slightly smaller red was applied over the black leaving the ‘pinstripe’.Color ‘bleed-through not a problem as Kirby had a “special Red” that basically has a white underside/base….. still thin enough to pick up some of the Solartex fabric look through the vinyl.
    Cowl blisters – not too bad to apply, patience and practice.14 needed, I ordered 20 to have a few spare to practice with….. not too bad at all once a ‘method’ was established.Graphics I got were $85 – wheel pants, side stripes, cowl blisters (plus spares), N-numbers, Waco logos, plus a few “No Push”, “No Step”, etc…. seemed very reasonable to me.Plus Kirby is great to work with as far as sending a ‘proof’ with all color and dimensions clearly laid out to look at before cutting anything.
    Guess that’s about it – Thanks guys!
    Barry
    No matter where you go, there you are.

  4. #15904
    WacoNut's Avatar
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    RE: WACO YMF

    Barry,
    We have the same taste I modeled my 33% After tail# NC 14132, it was shipped January 1935. My panels look very similar to your panels. I bought the instruments from InZpan.
    Due to a stupid mistake on my part last spring I am building a new fuselage. The plane will be refinished as NC 14132.
    Here is a pic of my panels.
    Later!!
    Anthony
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    WACO Brother #30 Cub Brother #17
    It's not the hours you put in It's what you put into the hours.

  5. #15905
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    RE: WACO YMF

    Anthony -
    Yup, definitely see some similarities there! Looked up some photos of # 14132.... yeah, I'd have to agree - similar tastes.

    Looks like you're well on the way - keep uip the good work!

    Barry
    No matter where you go, there you are.

  6. #15906
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    RE: WACO YMF


    ORIGINAL: bhall01

    Chuck-
    Balance – depends on where you want to balance it.*Based on the description in the Waco kit’s documentation (nothing shown on the plans), it sounds like they’re saying to balance just in front of, or on, the rear cabane struts.*To balance at that point would require about a pound of weight at the tailpost.*However, that point seems a bit rearward to me (tailheavy).*Based on the ‘old school’ method for figuring the CG of a bipe – well explained in this link *http://www.modelairplanenews.com/blo...cing-biplanes/ that point calculates to a CG at about 38%.
    *
    ** I checked at about 30% (using the method in the link) – that’s about 2” in front of the rear cabane mount.*Balance just barely tail-down at that point.*Compared that point to the CG noted on the Pica plans for both the 1/5th and 1/6th scale Wacos – their CG is in about that same relative location.*Same with the GP ARF Waco…. And all of those fly fine.*So for now, it’s balanced at that point… worst case it’s a little nose heavy (compared to the documented location), so I programmed in a 3rd flight mode with a little extra up-elevator – just in case.
    *
    *
    WacoNut –
    Thanks – I like the panels too!*The new “glass panel” Waco’s are fine, but I wanted to model mine more like a 30’s-style Waco well taken care of and still flying today.*So the panel design I came up with is kind of a composite of several different older Waco’s I found photos of.*Scratch built.*Instrument faces came off of Chief Aircraft’s ‘full scale’ side of the business – lots of nice HD photos of available instruments – everything from modern to classic – picked the ones I wanted, reduced to the size needed, and high-resolution printed on photo paper….. sure beats the “old days” of a few years ago when a Xerox was about the only tool we had to work with!*The rest is sheet plastic, some plywood, and a bunch of ‘fiddly-bits’ from around the shop.*Fun stuff!
    *
    *
    Peter –
    No, the tail feathers are not removable.*Although I don’t think it would be that hard to make them removable.*I did modify the attachment method some, and the means of setting the incidence….. basically I’d add/remove shims to adjust the incidence, but I figured once it’s set and ‘verified in the air’, there really shouldn’t be a need to change it.*And instead of using 2 ply ‘retainers’ for the rear of the stab I made*up a single laminated retainer the full width of the fuselage at that point…. So make that ‘bolt-on’ instead of glue on, and the stab would be removable.*As far as how to get it out from under the fin…. Fin and rudder would also need to be removable, but that wouldn’t be that difficult to do either.
    *
    *
    Dash7ATP –
    Vinyl graphics are from Kirby’s Kustom Vinyl - http://<font color=&#39;&#39;#0000ff&#39;&#39;>http:...ex.html</font> - Been in the business quite a while and is awesome to work with.*Pinstripe – yes and no – Kirby does his vinyls in layers, so there were black vinyls to apply first, then the slightly smaller red was applied over the black leaving the ‘pinstripe’.*Color ‘bleed-through not a problem as Kirby had a “special Red” that basically has a white underside/base….. still thin enough to pick up some of the Solartex fabric look through the vinyl.
    *
    ** Cowl blisters – not too bad to apply, patience and practice.*14 needed, I ordered 20 to have a few spare to practice with….. not too bad at all once a ‘method’ was established.*Graphics I got were $85 – wheel pants, side stripes, cowl blisters (plus spares), N-numbers, Waco logos, plus a few “No Push”, “No Step”, etc…. seemed very reasonable to me.*Plus Kirby is great to work with as far as sending a ‘proof’ with all color and dimensions clearly laid out to look at before cutting anything.
    *
    *
    ** Guess that’s about it – Thanks guys!
    *
    Barry
    You might just want to recalculate the center of balance on these bipes. We have and contrary to your statements, the Pica flies dragging its butt if balanced at the point shown on the plan. You have to add in a ton of down trim to level it out. That and it will balloon on landing (just ask Mitch). I have the factory drawings and the factory calls out the balance point at 28% Mean Average Chord. We went through all this several years ago here on this forum. You might want to do some research into it.

    Bill, Waco Brother #1
    Its easy, just glue all the pieces together, and sand off everything that doesnt look like an airplane.

  7. #15907
    Dash7ATP's Avatar
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    RE: WACO YMF

    "You might just want to recalculate the center of balance on these bipes. We have and contrary to your statements, the Pica flies dragging its butt if balanced at the point shown on the plan. You have to add in a ton of down trim to level it out. That and it will balloon on landing (just ask Mitch). I have the factory drawings and the factory calls out the balance point at 28% Mean Average Chord. We went through all this several years ago here on this forum. You might want to do some research into it.

    Bill, Waco Brother #1 "


    Hi Bill,

    Ihaven't seen you on here lately. Keeping a low profile I guess.

    I remember seeing the discussions on the CGlocation and your previous remarks. Given your comments, just where does that point fall on the 1/5 model when the plane is in a levil attitude? The LE of the top wing should make a pretty good reference point.

    Thanks,

    Joe
    "When you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."

    AMA # 8870, Member since 1978.
    Waco Brotherhood # 219.

  8. #15908
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    RE: WACO YMF

    ORIGINAL: Stickbuilder


    ORIGINAL: bhall01

    Chuck-
    Balance – depends on where you want to balance it.*Based on the description in the Waco kit’s documentation (nothing shown on the plans), it sounds like they’re saying to balance just in front of, or on, the rear cabane struts.*To balance at that point would require about a pound of weight at the tailpost.*However, that point seems a bit rearward to me (tailheavy).*Based on the ‘old school’ method for figuring the CG of a bipe – well explained in this link *http://www.modelairplanenews.com/blo...cing-biplanes/ that point calculates to a CG at about 38%.
    *
    ** I checked at about 30% (using the method in the link) – that’s about 2” in front of the rear cabane mount.*Balance just barely tail-down at that point.*Compared that point to the CG noted on the Pica plans for both the 1/5th and 1/6th scale Wacos – their CG is in about that same relative location.*Same with the GP ARF Waco…. And all of those fly fine.*So for now, it’s balanced at that point… worst case it’s a little nose heavy (compared to the documented location), so I programmed in a 3rd flight mode with a little extra up-elevator – just in case.
    *
    *
    WacoNut –
    Thanks – I like the panels too!*The new “glass panel” Waco’s are fine, but I wanted to model mine more like a 30’s-style Waco well taken care of and still flying today.*So the panel design I came up with is kind of a composite of several different older Waco’s I found photos of.*Scratch built.*Instrument faces came off of Chief Aircraft’s ‘full scale’ side of the business – lots of nice HD photos of available instruments – everything from modern to classic – picked the ones I wanted, reduced to the size needed, and high-resolution printed on photo paper….. sure beats the “old days” of a few years ago when a Xerox was about the only tool we had to work with!*The rest is sheet plastic, some plywood, and a bunch of ‘fiddly-bits’ from around the shop.*Fun stuff!
    *
    *
    Peter –
    No, the tail feathers are not removable.*Although I don’t think it would be that hard to make them removable.*I did modify the attachment method some, and the means of setting the incidence….. basically I’d add/remove shims to adjust the incidence, but I figured once it’s set and ‘verified in the air’, there really shouldn’t be a need to change it.*And instead of using 2 ply ‘retainers’ for the rear of the stab I made*up a single laminated retainer the full width of the fuselage at that point…. So make that ‘bolt-on’ instead of glue on, and the stab would be removable.*As far as how to get it out from under the fin…. Fin and rudder would also need to be removable, but that wouldn’t be that difficult to do either.
    *
    *
    Dash7ATP –
    Vinyl graphics are from Kirby’s Kustom Vinyl - http://<font color=&#39;&#39;#0000ff&#39;&#39;>http:...ex.html</font> - Been in the business quite a while and is awesome to work with.*Pinstripe – yes and no – Kirby does his vinyls in layers, so there were black vinyls to apply first, then the slightly smaller red was applied over the black leaving the ‘pinstripe’.*Color ‘bleed-through not a problem as Kirby had a “special Red” that basically has a white underside/base….. still thin enough to pick up some of the Solartex fabric look through the vinyl.
    *
    ** Cowl blisters – not too bad to apply, patience and practice.*14 needed, I ordered 20 to have a few spare to practice with….. not too bad at all once a ‘method’ was established.*Graphics I got were $85 – wheel pants, side stripes, cowl blisters (plus spares), N-numbers, Waco logos, plus a few “No Push”, “No Step”, etc…. seemed very reasonable to me.*Plus Kirby is great to work with as far as sending a ‘proof’ with all color and dimensions clearly laid out to look at before cutting anything.
    *
    *
    ** Guess that’s about it – Thanks guys!
    *
    Barry
    You might just want to recalculate the center of balance on these bipes. We have and contrary to your statements, the Pica flies dragging its butt if balanced at the point shown on the plan. You have to add in a ton of down trim to level it out. That and it will balloon on landing (just ask Mitch). I have the factory drawings and the factory calls out the balance point at 28% Mean Average Chord. We went through all this several years ago here on this forum. You might want to do some research into it.

    Bill, Waco Brother #1
    If an airplane drags it's tail in level flight power on, then it is generally more of an AOI issue between wing and horizontal stab relationship than a C/G issue, he stated that he was going to be a little more nose heavy, so why would that make it drag its tail? That would be stating that the more weight you add to the nose, the more tail heavy the airplane acts in flight... Just curious.

    By the way Berry, beautiful job on your WACO!

    Bob
    Fly It Like You Stole It!!!

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    RE: WACO YMF

    Hi Sensei, Yes, more stab incidence or down elevator (which no one likes) is most of the answer for horizontal "stance" in flight. That said the YMF should cruise in slightly tail high attitude. But the center of balance should also be considered for the type of stability the pilot wants whethrtit be rock solid with enough nose weight setup for a decent landing flair or with rearward for a pitchy aerobatic airplane. All things considered there are always compromises when setting up an aircraft. Mitch

  10. #15910
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    RE: WACO YMF

    This has always worked for me on my scratchbuilds, and my Pica.

    Les
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  11. #15911
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    RE: WACO YMF

    ORIGINAL: LesUyeda

    This has always worked for me on my scratchbuilds, and my Pica.

    Les
    Yes, a touch of negative AOI on the top wing has always worked for me on my bipes.

    Bob
    Fly It Like You Stole It!!!

  12. #15912
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    RE: WACO YMF


    ORIGINAL: nine o nine

    Hi Sensei, Yes, more stab incidence or down elevator (which no one likes) is most of the answer for horizontal ''stance'' in flight. That said the YMF should cruise in slightly tail high attitude. But the center of balance should also be considered for the type of stability the pilot wants whethrtit be rock solid with enough nose weight setup for a decent landing flair or with rearward for a pitchy aerobatic airplane. All things considered there are always compromises when setting up an aircraft. Mitch
    Designing aircraft platforms is mostly about compromises in my book and any aircraft that doesn't fly neutral to slightly tail high stance just doesn't look right to me. I do agree that that center of balance is a consideration however proper C/G and AOI are considerations as well and 1-2 positive degrees AOI on the horizontal stab is commonplace on many full scale aircraft. Another consideration would be to reset the AOI of the wings in relation to the FCL so you are not dragging the fuse during level flight, this would allow you to have a close to 0 if not 0 degrees AOI between the wings and stabs.

    Bob
    Fly It Like You Stole It!!!

  13. #15913
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    RE: WACO YMF

    This gets brought up every year or so about the balance and setup.

    AMR Has 3deg+ in the Stab, Barth has 2 deg+ in the stab. I have my wings set at 0/0 on the incidence. I had my balance at 31% MAC the 1st time around and will change it to 28% MAC this time around. This contributed to the stall on final that led to the crash of my 33% last spring. Totally preventable on my part where I had the CG set but moving the CG forward will improve the handleing IMO.

    Later!!
    Anthony
    WACO Brother #30 Cub Brother #17
    It's not the hours you put in It's what you put into the hours.

  14. #15914
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    RE: WACO YMF



    My Barth kit calls for 0-degrees on the lower wing and a 0 to -2 on the upper wing, recommending the -2-degrees for 'better roll performance'....... Iwent, again, with my "old school" way of doing things on a forward stagger bipe, with the same airfoil on upper and lower, you want a slight positive incidence on the upper wing. The idea being that in a stall condition the more positive-incidence upper wing will stall first, resulting in a "not-stalled"lower wing now flying a quite nose-heavy bird. Nose will pitch down and bring the plane back to a not-stalled condition.Negative incidence in the upper wing would result in the lower wing stalling first, now the not-stalled upper wing is flying a tail-heavy plane... and the stall condition gets worse..... bad day.

    Read this 'method' in a Pitts book quoting design ideas from Curtis Pitts himself, Ibelieve. Another method he used to have "0/0" incidence yet have the same functional results was to use different airfoils on the upper and lower wings symmetrical, or "more symmetrical", for the upper wing, semi-symmetrical for the lower wing.

    Whatever. Bottom line - flown bipes with a slightly positive upper several times, so far it's worked for me. So my Waco has just over a +1/2-degree in the upper wing. Also had a Pilot Pitts kit several years ago with the Symmetrical upper, semi-symmetrical lower set at 0/0... flew great.Went with what hasworked for me in the past.

    As for the CG on mine.... going to stick with the 30% of MAC..... we'll see!

    Good input guys! Thanks!

    Barry

    No matter where you go, there you are.

  15. #15915
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    RE: WACO YMF

    ORIGINAL: Dash7ATP

    * ''You might just want to recalculate the center of balance on these bipes. We have and contrary to your statements, the Pica flies dragging its butt if balanced at the point** shown on the plan. You have to add in a ton of down trim to level it out. That and it will balloon on landing (just ask Mitch). I have the factory drawings and the factory calls out the balance point at 28% Mean Average Chord. We went through all this several years ago here on this forum. You might want to do some research into it.

    Bill, Waco Brother #1 ''


    Hi Bill,

    I*haven't seen you on here lately.* Keeping a low profile I guess.

    I remember seeing the discussions on the CG*location and your previous remarks.* Given your comments, just where does that point fall on the 1/5 model when the plane is in a levil attitude?* The LE of the top wing should make a pretty good reference point.

    Thanks,

    Joe
    Joe, there is not a magic bullet on this. You still need to compute or measure your total chord and find the Mean Average. The best we have seen is 28-30% of that Mean Average. As to the Incidence, I like to set my bottom wing at zero and install the top wing with 1 degree negative (trailing edge higher than leading edge). This changes where the stall occurs. The Horizontal Stab is moot on mine since I can adjust it for the correct attitude in flight. It fly best at around positive 2.5 degrees.

    By the way, the factory full scale drawings state that 28% is the ideal point of balance for the full scale airplane as well. They show a very narrow range of balance too. They only allowed for 2 degrees total range.


    Bill, Waco Brother #1
    Its easy, just glue all the pieces together, and sand off everything that doesnt look like an airplane.

  16. #15916
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    RE: WACO YMF

    Barry,
    I believe Chuck is building a Barth Waco and he verified with Peter Barth that the -2 deg on the Stab was in error. He meant the Stab L/E higher (+2 deg) and he put -2 deg in the instructions.

    You may want to verify this especially if you set it up per the instructions.
    Anthony
    WACO Brother #30 Cub Brother #17
    It's not the hours you put in It's what you put into the hours.

  17. #15917
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    RE: WACO YMF

    Anthony,
    My instructions DOcall for +2 on the stab, which Idid incorporate. Also in mutliple places the instructions call for the -2 on the upper wing. Iopted to deviate from that.

    Thanks -

    Barry
    No matter where you go, there you are.

  18. #15918

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    RE: WACO YMF

    Guys,

    Maybe you can help me understand. What I know for sure is Lift of Wing plus Lift of Tail equals Weight of plane. If you make a side view sketch of plane and show the Wing lift going up and the Tail Lift going up, then the Weight is going down. Everything is in balance. What I don't know is the fore-aft locations of both Wing Lift and Tail Lift. Location of Weight is easy to find. It appears the only case where you would need no Tail Lift is when the Wing Lift vertical line passes right through the Weight (CG). So how do you find the location of the Wing Lift and Tail Lift relative to CG? I sure don't know how, and I'm guessing the Wing Lift is forward of Weight (CG) requiring Tail Lift to balance it out. The earlier notes suggested 2-3 degree positive. That's what I'm going to do on Barth 1/3. But it would be nice to know how to find the locations of Wing and Tail Lift.

    Hope this isn't too confusing.

    Mike Hopkins Waco Brotherhood # 132

  19. #15919
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    RE: WACO YMF

    ORIGINAL: hopkimf

    Guys,

    Maybe you can help me understand. What I know for sure is Lift of Wing plus Lift of Tail equals Weight of plane. If you make a side view sketch of plane and show the Wing lift going up and the Tail Lift going up, then the Weight is going down. Everything is in balance. What I don't know is the fore-aft locations of both Wing Lift and Tail Lift. Location of Weight is easy to find. It appears the only case where you would need no Tail Lift is when the Wing Lift vertical line passes right through the Weight (CG). So how do you find the location of the Wing Lift and Tail Lift relative to CG? I sure don't know how, and I'm guessing the Wing Lift is forward of Weight (CG) requiring Tail Lift to balance it out. The earlier notes suggested 2-3 degree positive. That's what I'm going to do on Barth 1/3. But it would be nice to know how to find the locations of Wing and Tail Lift.

    Hope this isn't too confusing.

    Mike Hopkins Waco Brotherhood # 132
    Are you saying the lift must equal or exceed weight by means of thrust, airspeed and AOA in order to fly?.

    Bob
    Fly It Like You Stole It!!!

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    RE: WACO YMF

    I believe for full scale aerodynamics the wings produce an upward force at a point called center of lift, weight produces a downward force at a point called center of gravity slightly ahead of the center of lift and the tail surface produces a balancing force that it usually downward but changes with airspeed. This is why if a plane is in level balanced flight and the power is brought back, with no other control inputs, the nose will drop due to a reduction in the downward tailforce and the plane will seek a flight attitude that will again balance. This usually means a descending nose down attitude. This makes sense to me looking at a plane like a Beechcraft Sport which has a full flying stabilator that is an inverted airfoil.

    But, I can't get the models I look at to make the same sense....a positive incidence on the stab equates to an upward force with airflow to my mind....but they sure do fly that way.

    Although, the minus 1 or 2 degree on the top wing compared to the bottom makes sense to me as that will keep the top wing flying if the bottom wing has reached or is near it's critical angle of attack. The bottom will will start to stall first and maybe give you some warning while the top wing is still producing lift and has not stalled yet.

    Just stirring the pot.

    Jaybird

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    RE: WACO YMF

    Bob,

    If a plane is flying steady state, the four forces Lift, Weight, Thrust, and Drag are balanced. Take the same plane and add 10 lbs while retaining everything else. Lift is less than weight. It's going down. To overcome that, more thrust (higher speed) is needed to generate more lift. Higher speed means more drag. So addition of power is needed with weight change. It's back in balance again. I believe the relationship still holds.

  22. #15922
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    RE: WACO YMF

    ORIGINAL: hopkimf

    Bob,

    If a plane is flying steady state, the four forces Lift, Weight, Thrust, and Drag are balanced. Take the same plane and add 10 lbs while retaining everything else. Lift is less than weight. It's going down. To overcome that, more thrust (higher speed) is needed to generate more lift. Higher speed means more drag. So addition of power is needed with weight change. It's back in balance again. I believe the relationship still holds.
    I agree, after reviewing the post over and over, that is why I change my question.

    Bob
    Fly It Like You Stole It!!!

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    RE: WACO YMF

    I think the answer to your question is yes! All of those elements, in steady state (not accelerating or decelerating etc.) are balanced. Change one element and the others will automatically adjust. To get a specific result though, an element will have to be intentially changed.

    Jaybird

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    RE: WACO YMF

    Jaybird,

    Appreciate your comments. But I still don't know where the center of lift for wing and tail are. If you draw a simple moment diagram, you could need tail down force or tail up force depending on location of centers of lift.

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    RE: WACO YMF

    I'm baffled too when it comes to the models. The flight training manuals and operating handbooks for the full size aircraft I fly clearly show the center of gravity ahead of the center of lift which is where the tail downforce is needed to balance. The full size obviously have total weight limits for combinations of fuel, passengers and cargo. Performance changes depending on that total weight. It also has to be be within a certain acceptable range which varies with the total weight. Too much weight too far forward and you may not have enough tailforce to pick the nose up at slower speeds (like during the landing flair). Too much weight too far back and you may not have enough tailforce to push the nose down once it is airborn. I believe the full size trainer planes are designed with the C of G ahead of the C of L so that they will be more stable and "better behaved" and have a tendancy to seek a balanced state without a lot of pilot input. Perhaps higher performance aircraft have the two closer together so that they are less stable and therefore easier to move around it's axis.

    For any particular aircraft design, the points where those elements occur are part of the engineering process. Most model plans only show a center of gravity point and not center of lift.

    Jaybird


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