Decalage angle

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Eugene

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Aeronca-Chief.jpeg IMG_5600 2.jpg Screen Shot 2019-08-15 at 22.46.35.png

Ok, on Aeronca total drag area probably about ~ 6-8 sq. ft. and that is why this aircraft has wing incidence of 1°, AOA at 85 MPH = 1°, 75% power = 47 HP., 1200 lb.

Skyboy drag area is ~ 16 sq. ft., wing incidence 4.5°, AOA at 85 MPH = 4-6°, 75% power = 75 HP, 1200 lb.

Theoretically if drag on Skyboy will be reduced by 50%, then this airplane will fly 85 MPH at 50% power = 50 HP and AOA will get to 1-2°.

If I understand this correctly drag difference on the wing at different AOA (1-4°) not very big deal at all. Problem is coming from engine/fuselage/landing gear.
 

Eugene

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Or seeing a problem that does not really exist.
Well, let me try to defend my thinking.

My local LSA instructor 3 years ago after 5 min aborted our flight and tell me that he doesn't want anything to do with this airplane. So, problem was there, but I didn't see it. In 3 years I herd so many conflicting recommendations from people who actually went to school for this, that I am not so sure anymore if anybody do see this problem for sure.

Sounds like drag is only problem. So I am trying to to this right and maybe going overboard a little. That's my nature.

Peter was telling us that to have things at correct angles is important


Screen Shot 2019-08-19 at 21.15.17.png

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proppastie

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My local LSA instructor 3 years ago after 5 min aborted our flight and tell me that he doesn't want anything to do with this airplane.
Do you remember how bad it was "handling back then" ? Is it better now. Does he sell LSA too?
 

Eugene

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Do you remember how bad it was "handling back then" ? Is it better now. Does he sell LSA too?

Yes, I didn't buy airplane from "recommended list". But most of it, I think, was fact that this airplane with passenger feels completely different. Like very lazy flying cow.
 

proppastie

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Like very lazy flying cow.
Well I have flown big or slow aircraft that I would call "piggy" they did not respond except with large control movements, and often opposite control to maintain the bank angle. My experience in gliders was they are like that when trying to thermal on the edge of a stall.....My Mooney does not like to fly slow, it wallows and feels mushy.....But this is normal for some aircraft. I am not sure if that is what you are talking about. However someone used to a crisp sensitive handling might find a plane that feels like it is in slow flight not very comfortable. Do you have a large margin to the stall speed?
 

Eugene

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fly slow, it wallows and feels mushy.....But this is normal for some aircraft.
With only 200 hours total I am no expert at all. But as far as I can tell my Skyboy flies and stalls very similar to Aeronca Champ/Chief. Because same 4412 wing with 60" chord. I call it real aircraft feel and not Qucksilver-like. I do like it and and its not my problem.

Problem or question is why this aircraft transforming in to flying cow with passenger? One of this days I will be flying to Oshkosh with my wife and my response for "white pusher, rock your wings" will be very strange looking motions. I am sure they will not call it "good rock!".

If 16 sq. ft. is correct number for my frontal drag area, then additional load as passenger maybe pushing this aircraft to its very limits. I don't know. I do know that Aeronca with much smaller engine and heavier airframe show very little difference with passenger vs solo.
 

proppastie

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Problem or question is why this aircraft transforming in to flying cow with passenger?
not sure what you mean.....the CG is more forward with a passenger.....do you require a much higher AOA with a passenger....I know you have been posting many pictures with angles and AOA but unless you couple that with the handling problem I can not relate to what you are saying.

Do you have a large margin to the stall (Cruse airspeed vs Stall airspeed) with a passenger. Do you feel like you are in "slow flight" with a passenger.

An Aeronca (any aircraft) will climb slower with more weight, but at cruse it should feel about the same, maybe a little more down trim....In your case more up trim.
 

Eugene

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I don't have answers to all questions, but I will try. Some of it I know from personal experience and some from talking to another Skyboy owners.

Reaction of my instructor was very similar to different instructors on first flight with new owners. Firs impression that aircraft doesn't want to fly and need a lot of back pressure on the stick with 2 people. CG with 2 big boys can be at 24-22% MAC and you need a lot of up trim. Some instructors call it sling shot. With a lot of pressure on the stick and 60-70 mph indicated rotation is somewhat abrupt if you don't know this aircraft.

One story I now about instructor went to fly solo first. He made 180° turn and immediately landed. He walked away and didn't want to fly this airplane ever again. He was very light little guy and we think CG with full tank was about 37-39% MAC. Rear limit is 36.6%.

With my instructor we had hard time to stall. Not enough elevator with 2 people to do it. Solo without ballast upfront CG at 34-36% and you can do stalls all day long. Power-on stall attempt turned into slow flight with 2 people.

Flying solo Skyboy stick feels like Aeronca. With passenger my instructor was moving stick side-to-side but aircraft wasn't responding. I did get pretty nervous that day. He did used word "mushing" many times.

I personally had Cessna 172 - 160HP with 3 big passengers (about 200 lb. over gross). I do remember this mushy overloaded feeling. You only do this ones if you walk away from it.

From AOA stand point all owners report that with ballast upfront airplane flies better and faster. I now with my wife (140 lb.) my airspeed indicator is showing me 7-10 MPH better speed and smaller AOA. Wing almost level with horizon. You can call me crazy.That's OK.

With bigger passenger feels much mushier with airspeed moving in to red zone at 5500 RPM and you need to remove power. At 5000 RPM you will get 85-90 MPH indicated with ailerons not very responsive at all. Visible about 6° AOA. Lot more up trim. To me feels like Cessna with full flaps. Feels like you no longer flying this airplane, and airplane flying you.
 
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proppastie

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aircraft doesn't want to fly and need a lot of back pressure on the stick with 2 people. CG with 2 big boys can be at 24-22% MAC and you need a lot of up trim.

With my instructor we had hard time to stall. Not enough elevator with 2 people to do it. moving stick side-to-side but aircraft wasn't responding. I did get pretty nervous that day. He did used word "mushing" many times.



From AOA stand point all owners report that with ballast upfront airplane flies better and faster. I now with my wife (140 lb.) my airspeed indicator is showing me 7-10 MPH better speed and smaller AOA. Wing almost level with horizon. You can call me crazy.That's OK.

With bigger passenger feels much mushier with airspeed moving in to red zone at 5500 RPM and you need to remove power. At 5000 RPM you will get 85-90 MPH indicated with ailerons not very responsive at all. Visible about 6° AOA. Lot more up trim. To me feels like Cessna with full flaps. Feels like you no longer flying this airplane, and airplane flying you.
I was taught 25% was a good cg .....you should have enough elevator to stall but you do not.
 

Eugene

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fullsizeoutput_17c5.jpeg fullsizeoutput_17c7.jpeg


It was explained to me that's sometimes in problem areas on trailing edge better to end it like on Icon A5. It forming spinning area that acting like bearing. Not sure if my picture is correct. I have similar area in front of propeller on my wing. Planning to do same thing on my new fearing.

fullsizeoutput_17b6.jpeg
 

Eugene

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Screen Shot 2019-08-24 at 22.22.36.png Screen Shot 2019-08-24 at 22.20.37.png Screen Shot 2019-08-24 at 22.19.19.png


Looking at this pictures, I see relationship between diameter and length as 1:3.75. If this relationship is still good for 100 MPH, then my new fearing will not have any flow separation on bottom part. I understand that part in front of propeller will have to look like on Icon A5. No options there.
 

Eugene

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View attachment 88124

Have a closer look at the trailing edge just in front of the prop.

The noise reduction was remarkable.

Thank you. Looks like another attempt to organize air flow if front of propeller and as result improving efficiency. Prop extension on 912 engines limited to 120 mm. Would be nice to see the picture from the top. It is hard to make clear understanding what was really done and at what angle.
 
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