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1. 04:54 PM - Re: Lycoming O-235 engines (Mark Kettering)
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| Subject: | Re: Lycoming O-235 engines |
Hi Al,
Actually the airfoil is just about perfect for the aircraft as a whole. But for
max speed there is just too much wing area for the weight even with a slight
increase in gross for the carbon version. Of course to keep the landing speed
down I would not want to decrease the wing area. I plan to slightly increase
the wing area via new wing tips similar to what Scott has done on his TR-1.
This will help with stall speed with the slight increase in gross.
The airfoil is not all that important at cruise for most light aircraft. Light
aircraft just have way too much wing area for ideal cruise performance so are
not generally in best place of the drag bucket. For example a TR-4 with a 180
hp at max cruise is flying with a CL of about 0.3. No standardish airfoil that
can produce good lift for landing has a minimum drag at or near 0.3 CL. With
a 350 hp turbo motor and flying at 24k MSL the CL would be about 0.2. A bit
farther from ideal but since we were already so far the difference is small.
The only thing to do is reduce wing area. This is what Lancair does. The
4P has only 98 sq ft of wing and a much higher gross weight than a TR-4. But reducing
the wing area would increase the stall speed and make the plane less safe.
I want a plane that is fast but also has a nice safe low landing speed and
good power off glide.
Also keep in mind that this is just the induced drag we are talking about. At
cruise even with the 180 HP most of the drag is skin friction and not induced.
At the higher cruise speed with 350 hp the induced drag is an even smaller part
of the total drag. So even if there was a fairly large change in the induced
drag due to the airfoil (there is not) it would have a very small impact of
cruise speed.
Mark
-----Original Message-----
>From: Alfred Rosa <76papa@dishmail.net>
>Sent: Nov 7, 2009 7:12 AM
>To: kis-list@matronics.com
>Subject: Re: KIS-List: Lycoming O-235 engines
>
>
>
>On Nov 6, 2009, at 8:50 PM, Mark Kettering wrote:
>
>>
>> Hi Al,
>>
>> For my all carbon TR-4 I just bought a 350 HP TIO-540 from a Mirage.
>
>
>Are you modifying the wings? I don't think the original airfoil
>design is ideal for utilizing the speed from such a powerplant.
>
>Al
>
>
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