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Author	Topic: Cyl Airfoil question
Laika 801 Pilot	posted 03-14- 05:54 AM OK the Ishak is still to fast in speed (about 10-15 mph) and climb (16400 ft in about 4.2 minutes). I set the RPM to 2000 (original 2250) but I would keep the prop size (1400 mm, pitch 55). My Cyl-Airfoil´s area is 140 sqft but I´m still not sure how to measure it exactly. Should I take the whole fuse and estimate the surface of it ?. I need any tips comments etc for that Cyl-thing and its chord!!! IP: Logged
Tailslide Pilot	posted 03-14- 11:25 AM Laika, go to http://firelight.dynip.com/oppforum And look in the documentation forum. I just updated the FM FAQ. The cylinder airfoil represents all the drag on the plane other than the wings and I don't think it's possible to calculate it since it depends on alot of things up to and including what kind of paint and rivets were used on the plane. TS IP: Logged
Tailslide Pilot	posted 03-14- 11:49 AM I'd leave the RPM at the original values if you know them and change other things.. try making your prop blades skinnier. TS IP: Logged
Laika 801 Pilot	posted 03-14- 01:40 PM thanks - I´m still testing ! IP: Logged
Laika 801 Pilot	posted 03-14- 02:09 PM Another question - I got odd values for the AirAr when I determine them as described in the OP Manual/Specification (Ar=2.36). I´m not sure if my chords are right. How and where must I measure the Chord for an element. Maybe someone can post a small pic ? IP: Logged
Laika 801 Pilot	posted 03-14- 05:49 PM ? IP: Logged
Laika 801 Pilot	posted 03-14- 06:07 PM [img]http://rcswww.urz.tu-dresden.de/~re723888/closeform.gif[img] How can I tell them NOT to fly this way ? BTW - DONT TRY THIS AT HOME ! IP: Logged
Laika 801 Pilot	posted 03-14- 06:08 PM sorry IP: Logged
Tailslide Pilot	posted 03-14- 07:27 PM Can you post some more details about how you arrived at your wing area and chord? TS ------------------ ________________________ TS Aircombat IP: Logged
Tailslide Pilot	posted 03-14- 07:29 PM Looking at your wing, I would say you could just measure from front to back in the middle of one wing to get your chord. TS IP: Logged
Laika 801 Pilot	posted 03-15- 03:14 AM The wing-area should be 156.6 sqft. I set the wingtip to 18 and the wing to 60 = 78 x2 =156. This should be right. Chords - I measured 3 chords along the wing and calculate the average = 5.5 ft. Then I measured the lengt (half wingspan) and divided it by the average chord. I get an AR of about 2.7. But with your method I get about 5.8. So maybe I should use the whole wingspan ? Then I get 5.4 as AR. How did I measure the chord for the fuse (whole lenght ?) IP: Logged
Laika 801 Pilot	posted 03-15- 04:31 AM OK - now the Ishak matches Speed quiet good up high and down low. It´s about 10 mph to fast up high (313 mph instead 303) and climbs a bit too fast (4 min 50 sec to 16400 ft, should be 5.2 min). How should I measure the climb-time (with or without takeoff) ? I also got different specs for the I-16: Speed L273/H303 (good source) mph or L288/H323 (?) mph. So what should I do ? Increase the prop pitch and get a faster plane but the right climb time ? I don´t know ! IP: Logged
Tailslide Pilot	posted 03-15- 10:34 AM Make your prop blades a bit skinnier yet.. reduce the cylinder airfoil a bit to compensate for the speeds down low. Correct, you want to use the whole wingspan not just the span of one wing when using that forumula.. Climb rate, load the plane with a full fuel load, double check it's weight against the real plane's takeoff weight. Once that is correct climb full fuelled through 1000 feet for one minute then subtract 1000 from the altitude you reach, that's how I got initial climb rate in feet per minute. You also need to measure sustained climb rate like you are doing.. (x mins to y altitude). TS TS ------------------ ________________________ TS Aircombat IP: Logged
Tailslide Pilot	posted 03-15- 10:36 AM Whats the wingspan? It would be (wingspan * wingspan) ---------------------- 156.6 IP: Logged
Laika 801 Pilot	posted 03-15- 03:21 PM It would be ? What ? Wingspan is 14 feet 54 inches. (14.54 x 14.54)/156.6 = 1.3586 ? ? ? IP: Logged
Tailslide Pilot	posted 03-15- 03:33 PM Wingspan is the distance from wingtip to wingtip are you sure it's only 14 feet? IP: Logged
Tailslide Pilot	posted 03-15- 03:35 PM If you were just measuring one wing then it would be 29.08 x 29.08 --------------- 156.6 =5.400 ------------------ ________________________ TS Aircombat IP: Logged

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