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Midwest Super Stinker angle of incidence - 9/21/2010 3:14 AM   
cde


 

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Status: offline 		Hi there I picked up a beautiful (never flown) Super Stinker and I want to go through the plane just to make sure things are straight etc. I've got the instructions but no plans. Does anyone know what the recommended angle of incidence is on the upper and lower wing? Also, was there any positive or negative incidence on the stab? There was nothing in the instructions that referenced incidence (that I could find) Any info that you found benneficial that you can share would be great! I appreciate your help everyone!
Calvin

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RE: Midwest Super Stinker angle of incidence - 9/21/2010 5:15 PM   
Zor



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Status: offline 		Calvin,

Stab zero
Low wing zero
High wing minus one.

Zor


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RE: Midwest Super Stinker angle of incidence - 9/21/2010 6:54 PM   
smithcreek



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Status: offline 		The Super Stinker is -1/2 upper wing, 0 lower wing, +1 stab

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RE: Midwest Super Stinker angle of incidence - 9/22/2010 12:10 AM   
cde


 

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I measured it last night with the stab zero and both wings have some positive incidence but I will check with positive 1 degree on stab and report back. do any of you know if the original plans actually show the angle of incidence and if so, do you happen to have a copy? Thanks guys!
Calvin

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RE: Midwest Super Stinker angle of incidence - 9/22/2010 12:19 AM   
Zor



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quote:

ORIGINAL: smithcreek

The Super Stinker is -1/2 upper wing, 0 lower wing, +1 stab


Since incdence is an angle measured relative to a reference line _ _ _ 
If we rotate the reference line plus 1 degree (front of the ref line a bit higher)
.The stabilizer becomes 0 (zero) degrees.
The upper wing becomes - (minus) 1 1/2 degrees.
The lower wing becomes - (minus) 1 degree.

Let us ask ourselves why the specification of plus 1 degree for the stab ?
In attempting an answer to the above question we know that some positive angle of attack is needed at the main wings to create a lift nearly equal to the weight of the model.
Since the low wing is built at zero degrees and the top wing at minus 1/2 degree, then some up elevator will be needed to create a positive angle of attack at the main wings.

This becomes equivalent to cancel the plus one degree of the stabilizer.

The weight is always at the CG.
The lift has a variable line of action depending on the angle of attack.
Then the thrust line and drag line comes into play.
If the thrust line is below the drag line, it will create a nose up tendency (how much will vary with the speed at any moment). This can be counter-acted by a positive incidence of the stab.

The ideal condition for an aerobatic model is to have the thrust line and drag line coincident and both passing at the CG (no pitch action) ; then the lift as close to the CG as practical.

In such a condition inverted flight behaves nearly the same as upright flight.
The fact that the lift action varies versus the CG is something we cannot control. It is in the nature of airfoil behavior.

A midwing monoplane design comes closest to have the thrust line and drag line close to the CG or coincident with it.

First Conclusion ?
The CG location setup will really be the factor that determines the need for plus one degree at the stab.
If the elevator is lined up with the stab and naturally lines up with the flight trajectory we then have a negative lift from the main wings.

This design does not appear to me to be the best. I would love a discussion with the designer.

In a biplane we also have to take into consideration the effect of how each wing affects the airflow on the other wing. That is well beyond this forum.

Last Conclusion ! ! !
The average model pilot will never notice any difference in his style of flying. LOL .

Cheers, de Zor.



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RE: Midwest Super Stinker angle of incidence - 9/22/2010 6:06 AM   
Zor



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quote:

ORIGINAL: cde


I measured it last night with the stab zero and both wings have some positive incidence but I will check with positive 1 degree on stab and report back. do any of you know if the original plans actually show the angle of incidence and if so, do you happen to have a copy? Thanks guys!
Calvin


 Hi Calvin,

You posted at 4:10 and I posted at 4:19. That means I was typing when you posted.

Perhaps we need some common understanding of incidence angles and also of another term called "decalage".

The incidence angles are measured by reference to a single reference line.

Ideally, the stab-elev in a single geometrical plane (neutral elevator) are trying to line up in the air stream and produce no lift force. If the main wings do not produce an air stream at the tail which has a downward motion, then the flat plane of the horizontal tail would be parallel to the flight trajectory.

If the tail is exposed to a downstream then some positive incidence might be justified to help achieve a zero angle of attack of the horizontal tail. That can be true at only one speed. At other speeds the angle of attack of the main wings will change and the downstream angle will also change. Then trimming is needed.

You found that if you consider the stab-elev as being at zero angle then both main wings have a positive angle related to the stab-elev. That would be normal so that when the stab-elev line up with the airstream then the main wings are producing some positive lift  We now can say that the stab-elev have zero incidence and both main wings have some amount of positive incidence.

The angle difference between the stab-elev and the main wings is called "decalage" . In a monoplane the reference to decalage is always obviously between the single wing and the stab-elev. In a biplane we also refer to the wing decalage and that is any angular difference between the incidence of the two wings.

In your statements above, I do not know what you did. Perhaps you rotated the stab by one degree in reference to the fuselage or to the reference line or perhaps you simply used a level to place the plane such that the stab is horizontal *using the level instrument". In this latter case then the main wings are also rotating by the same amount (the decalage is not changed). 

The incidence angles are not the important factor. If we change the reference line so that we measure (let us exagerate for clear undestanding) 10 degrees of stab then the main wings have also changed by an equal amount but the decalage has not changed. The result would simply be that the fuselage has a different angle to the flight trajectory.and may offer some kifference in total drag. Remember that 10 degrees is an exageration.

Ideally, at cruise speed (somewhere about half way between stall speed and maximum speed) we have the stab-elec at zero angle of attack and an angle of attack of the main wings to produce a lift force equal to the weight. That requires some positive decalage angle (wing chord leading edge higher than the trailing edge in normal level flight attitude). We as hobbyist have to experiment by setting a cruise power setting and neutralizing the stab-elev and watch if the model is flying level (constant altitude to the best of our ability to judge). If the model keep descending we need more decalage and if it keeps climbing we need less decalage. Yes we can trim for level flight which is possible at a different speed.

There is no black and/or white . . . everything is a compromise with lots of interreaction.
I think I have said enough for now.
I anyon has any questions, just ask. Someone will reply for sure.

Enjoy your flying with a well balanced model airplane dynamically as well as statically.

Zor


 



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RE: Midwest Super Stinker angle of incidence - 9/22/2010 6:30 AM   
smithcreek



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quote:

ORIGINAL: cde
I measured it last night with the stab zero and both wings have some positive incidence but I will check with positive 1 degree on stab and report back. do any of you know if the original plans actually show the angle of incidence and if so, do you happen to have a copy? Thanks guys!
Calvin


I checked my plans before posting earlier. I built this kit, great flying plane. Seems to me if you measured off the stab with the stab leveled to 0 degrees you would end up with negative on both wings if they were mounted right. Are you sure the meter is facing the right direction?



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RE: Midwest Super Stinker angle of incidence - 9/22/2010 7:08 AM   
cde


 

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Status: offline 		I want to thank you both for your replys and education as well. So, as much as it disgusts me to say this... , my meter was in fact backwards... uhg (oh the humility!). With the elevator at 1 degree positive, I've got the left wings almost perfect but the right wings are showing almost identical positive 1.5- 2 degrees both top and bottom. I guess the good news is that they are relative and I should be able to get the warp out. Tomorrow, I'll try removing the brace between the two wings on the right side and see if I can not relieve some pressure and go from there. If not, I'll look at the wing saddles and worst case senario determine if ther is a warp with both wings. I do not have servo's in it just yet so I can only really determine incince only half way through the wing (right before the ailerons-towards the wing root). I need to get the ailerons all straight and measure throughout the wing to determine if there is a warp. Also, Im going to take the gear off and mock the plane on a wooden stand - flat surface - to ensure everything is zero'd out. I will let you know what my outcome is. If I can at least get the left and right sides of the planes wings on target, I can set the upper wings incidence at your recommendations and the lower at 0. Wouldn't that be great!! ??? lol

Calvin

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RE: Midwest Super Stinker angle of incidence - 9/22/2010 7:09 AM   
cde


 

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Status: offline 		Smith my gosh is your plane beautiful!!!!!

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RE: Midwest Super Stinker angle of incidence - 9/22/2010 6:20 PM   
Zor



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Status: offline 		Hi guys,

Smith, I have to say it also. Your Skybolt is absolutely gorgeous.
You have all reasons to be proud of it.

This discussion has led me to attempt to design and build an incidence meter.
I do not have one because I disagree with the designs I have seen.

I would not be Zor if I did not explain why I disagree. Note that I may not have seen every incidence meter designs existing. Those that I have seen have an angular locating geometry (difficult to explain in words) Something like an equilateral triangle or the smaller angle of an isocele triangle sitting against the leading edge of the wing and a similar arrangement for the trailing edge. This results in a two point contact to a curved surface (the leading edge of he wing(s)) and similar at the trailing edge.

I do not like this arrangement because the angle measured will vary with the curvature of the leading edge (not being absolutely straight or uniform along the length of the wing) or if the trailing edge is not straight in a vertical geometrical plane. It can be straight looking from the top but it might not be straigth looking horizontally.

I have made my verifications using measurements.
The sine of 1 (one) degree is 0.01745241
The tangent of 1 degree is 0.01745506
I think you will agree that the first 5 decimals being the same we can work with those 5 decimals.

So a flat geometrical plane, representing the chords of the airfoil would have a difference from the horizontal as follows _ _ _ 
Chord of 4" and incidence of 1 degree means 4" x 0.01745 gives 0.06982026 inch difference.
Mesuring with a Mitutoyo caliper we accept 0.069 inches.
Chord of 8" and incidence of 1 degree means 8 x 0.01745 gives 0.13964052 Obviously twice the above twice as far.

My Skybolt has a chord of 8.5" for the lower wing and 8 11/16" for the upper wing. Similar calculations can be made and easily measured anywhere along the the wingspan leading and trailing edge in reference to a flat plane surface. Call me crazy and I know that I am but I think I have a fair idea of what I actually enjoy doing.

Figuring the lower wing to be at zero incidence the obvious is same dimension at the leading edge and the trailing edge. (zero incidence) as measured to a flat horizontal plane.

Figuring the top wing the dimensional difference for minus 1 (one) degree becomes _ _ _ _ 
8.6875 x 0.01745 gives 0.1516 inch wih the leading edge closer to the flat reference by this dimension.

If anyone is not enjoying this, STOP READING. _ _ _ Laughing Out  Loud.

Incidentally, My Skybolt drawings are asking for . . .
Low wing 0 (zero)
Top wing -1 (minus one)
Stab 1 1/2 (plus one and half).

So I am asking myself ... "How do the designer arrives at these figures ?" and "How accurate are they ?" and "How much accuracy do I need while building ?" and "What are the results of errors (differences) in the building and assembly ?" and "How can I judge any results of errors ?"

What would be the difference in the flying of the model ?

I truly believe that these angles, if close enough with our ability to measure or with the use of commercially available meters, are not very critical.
I also believe that the average flier is not capable of noticing any differences in the flying due to building or assembling errors.

Now I am on my way to design and build my own incidence meter.
All kinds of ways to be crazy  _ _ _  and have lots of fun and enjoyments.

Wishing all readers a great day flying.

Zor
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RE: Midwest Super Stinker angle of incidence - 9/23/2010 7:24 PM   
flygilmore



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Status: offline 		Uhhh Zor, thats a Super Stinker, not a Skybolt ! Indeed, a beautiful plane worth being very proud of BTW!!!!!!

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RE: Midwest Super Stinker angle of incidence - 9/23/2010 10:56 PM   
Zor



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quote:

ORIGINAL: flygilmore

Uhhh Zor, thats a Super Stinker, not a Skybolt ! Indeed, a beautiful plane worth being very proud of BTW!!!!!!


flygilmore,

You are correct about the Super Stinker.
It is so beautiful that it blinded me at first sight and did not pay more attention.

My apologies for the misnomer.

I now feel that my Skybolt by comparison IS a stinker. Hee Hee !

Thanks for the correction.

Zor


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RE: Midwest Super Stinker angle of incidence - 9/25/2010 10:44 PM   
Zor



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Status: offline 		cde,

Did you find a satisfactory answer ?

Zor


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RE: Midwest Super Stinker angle of incidence - 9/28/2010 6:04 PM   
cde


 

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Status: offline 		I will take a look at it this weekend and let you know. I hope to round up a few more incidence meters from my friends so I can have one on each wing and each side.

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RE: Midwest Super Stinker angle of incidence - 10/2/2010 6:44 PM   
Texan



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Status: offline 		Interested in how those settings work out for you. Please comment on your maiden flight. My Super Stinker is starting to get the reputation of "Hangar Queen" ... I wonder why

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RE: Midwest Super Stinker angle of incidence - 10/2/2010 9:13 PM   
Zor



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quote:

ORIGINAL: Texan

Interested in how those settings work out for you. Please comment on your maiden flight. My Super Stinker is starting to get the reputation of "Hangar Queen" ... I wonder why


Hello Texan,

I think I know why _ _ _ _ You keep admiring a beautiful model and there is no time left to go and fly it.

I do not have this problem with my Super Skybolt because it looks like a Super Stinker.

Ha Ha! _ _ _ _ Hee Hee ! _ _ _ _ LOL

Now _ _ _ Why would they name a beautiful machine a "Super Stinker" when it looks just as nice as a "Supe Skybolt" ? to the point that I misidentified a Stinker as being a Skybolt. (read previous postings).

As I wrote before; its beauty just blinded me.

Zor



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RE: Midwest Super Stinker angle of incidence - 10/6/2010 7:27 AM   
cde


 

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Status: offline 		HI guys, well I've put 6 total angle incidence meters on both right and left upper and lower wings as well as both sides of the stab with +1.... both left wings are perfect and both right wings are off by over one degree each. It appears that the prior owner hung the plane and I can see stress marks on the leading and trailing edges of the right wing which might have cause a warp over the many years. No worries, I can fix it easily! Now for the next question... I can not get a set of plans (both Midwest and RCM do not have plans). Can anyone tell me what the thrust line of the engine should be? Currently the firewall or engine mount has positive AND right incidence. If the plans say what angle they should both be I'll be set to either fix it or leave it alone. Can anyone help? Do the orignal plans even say the up/down/right thrust degrees??

Thank you all for such great support!! I promise to post pictures soon...

Calvin

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RE: Midwest Super Stinker angle of incidence - 10/8/2010 11:03 PM   
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Status: offline 		Just checked the plans, there is no reference in the handbook.

2 deg. right thrust with 2 deg. up thrust.

The hand book states this for a Moki 180 and has been pre set for the build. I fly with a Supre Tigre 3250 and have no problems. My set up is four high torque servos on the wings, one on the rudder, two elevators, one throttle. Because of the power drain I use a two cell lipo as the battery power.
Hope this helps

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RE: Midwest Super Stinker angle of incidence - 10/8/2010 11:11 PM   
smithcreek



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Status: offline 		I wouldn't even bother checking the engine box thrust angles, they are set in the die cut pieces and would be nearly impossible to screw up.

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