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flaps and their efficiency

Good sims require good FDMs (the "thing" that makes an aircraft behave like an aircraft).

Re: flaps and their efficiency

Postby wlbragg » Sat Mar 11, 2017 8:24 pm

Well, I'll have to try that. I know the nose falls out of the way like it should.
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Re: flaps and their efficiency

Postby Bomber » Sat Mar 11, 2017 8:30 pm

Yeh but is that because there's an extra moment rotation being applied or......
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Re: flaps and their efficiency

Postby wlbragg » Sat Mar 11, 2017 8:32 pm

OK, kind of hard to test, but here is what I think happens. To get to 17deg pitch I need the 90hp at full throttle and stable climb. throw the flaps to full and it drops off. I can't keep the pitch at 17 after the flaps are deployed to a full 50.
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Re: flaps and their efficiency

Postby Bomber » Sat Mar 11, 2017 9:11 pm

I tell ya what..... send me a download link to your up to date plane and I'll convert it's fdm to go in a wind tunnel and then test it for you...
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Re: flaps and their efficiency

Postby Alant » Sat Mar 11, 2017 9:12 pm

Asuming Simon is modelling the Corby Starlet CJ-1 the answer to his question is zero as it does not have flaps.
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Re: flaps and their efficiency

Postby Bomber » Sat Mar 11, 2017 9:34 pm

Yes some rather conflicting information always makes the task harder..

http://www.pilotfriend.com/experimental/acft2/32.htm

Notice the words flaps...

Yet I'm not sure it has them.
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Re: flaps and their efficiency

Postby Alant » Sat Mar 11, 2017 10:20 pm

1. Look for the flaps on the drawing and data sheet http://corbystarlet.tripod.com/tech.htm
2. Google "corby starlet flaps"
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Re: flaps and their efficiency

Postby wlbragg » Sat Mar 11, 2017 10:45 pm

Simon, the J3Cub in fgaddon is current.
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Re: flaps and their efficiency

Postby Richard » Sun Mar 12, 2017 12:16 am

Bomber wrote in Sat Mar 11, 2017 6:04 pm:Richard I don't know what percentage flap to wing ratio you're using but be aware...
on the Corby Starlet the inner part of the flap is 32.5% going to 35% at the outer part of the flap..
Ailerons go from 34% inner part to 24% outer part


sorry for the confusion the plots are for my current WIP model; nothing to do with the Corby; it just so happens that's what I'm doing today so I figured I'd share my results as it seems relevant.

One thing that I have come across with VSPAero is that the lateral coefficients, particularly sideslip are changed by flaps; and yet (providing I remember correctly) there isn't usually a set of tables for this; all I've managed to find is asymmetric effects of flaps.

However as AlanT correctly says, there are no flaps (I checked and he's right). So maybe that's why it's proving so hard to model them -)
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Re: flaps and their efficiency

Postby Bomber » Sun Mar 12, 2017 12:25 am

I understand that Richard.... it's just that your flap look to be 25%....

Hope that's correct
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Re: flaps and their efficiency

Postby Alant » Sun Mar 12, 2017 2:06 am

The Corby Starlet CJ-1 has a very large propeller to wingspan ratio.This means that approximately 25% of the wing is in the downwash of the propeller.
As noted in the data sheet this will have a significant effect on lift with powrr on and power off.

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Re: flaps and their efficiency

Postby Bomber » Sun Mar 12, 2017 9:58 am

wlbragg wrote in Sat Mar 11, 2017 10:45 pm:Simon, the J3Cub in fgaddon is current.


Just updated my copy to ensure I had the most up-to-date.... it's a YAsim model yes ?

If so I've no experience or understanding of this type of flight model.... I'm gonna have to say I can't help on this type.

sorry
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Re: flaps and their efficiency

Postby wlbragg » Sun Mar 12, 2017 10:06 am

No, it's the JSBSim version, specifically the PA-18. The J3Cub does not have flaps.
The files to use would be
/J3Cub/J3Cub.xml (FDM)
/J3Cub/PA-18-set.xml
/J3Cub/J3Cub-main.xml
/J3Cub/Models/PA-18.xml
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Re: flaps and their efficiency

Postby Bomber » Sun Mar 12, 2017 10:43 am

Some confusion here then as I've not got those files in my latest download... this morning...

Can I ask you to just post up the link... that way we're 100% certain that I'm working on the correct plane

Regards

Simon

{edit} downloaded another version from here...

http://wiki.flightgear.org/Piper_J3_Cub
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchel
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Re: flaps and their efficiency

Postby Bomber » Sun Mar 12, 2017 11:38 am

Richard wrote in Fri Mar 10, 2017 8:23 am:
I can't really answer the question as to whether your 30kts is valid in terms of Cl, because there isn't enough information; however if you give me the span, root & tip chord, root & tip aerofoil I'll run it through VSPaero and see what comes out.



span 18.5ft
root cord 52.7inches
tip cord 39.9inches
airfoil = NACA 43012
http://m-selig.ae.illinois.edu/ads/aircraft.html
polars
    0.000000,0.000000
    0.012500,0.038900
    0.025000,0.051400
    0.050000,0.069200
    0.075000,0.080300
    0.100000,0.087700
    0.150000,0.093300
    0.200000,0.092700
    0.250000,0.089500
    0.300000,0.085700
    0.400000,0.077000
    0.500000,0.065600
    0.600000,0.052000
    0.700000,0.037000
    0.800000,0.024400
    0.900000,0.012500
    1.000000,0.000000
    0.900000,-0.015000
    0.800000,-0.027400
    0.700000,-0.036000
    0.600000,-0.039200
    0.500000,-0.040300
    0.400000,-0.039200
    0.300000,-0.035000
    0.250000,-0.032700
    0.200000,-0.029500
    0.150000,-0.025700
    0.100000,-0.021100
    0.075000,-0.018500
    0.050000,-0.015400
    0.025000,-0.011400
    0.012500,-0.008300
    0.000000,0.000000

incidence at root = 2 1/2 degs
incidence at tip = -1 degs [1]

Incidence 21/2° - 1° Tip
http://corbystarlet.tripod.com/tech.htm

[1] Be aware that's my interpretation of what it's saying for incidence
"If anyone ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me - it's all balls" - R J Mitchel
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