Thread: Value of a knot
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Old September 7th 04, 01:45 PM
Nathan Young
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On Mon, 06 Sep 2004 20:51:16 GMT, "Dude" wrote:

I got an idea from a recent thread.

I would like to know what you guys would spend to go a little faster. This
would seem to be interesting information, and a fun topic.

Please note the present speed of your plane, because 5 knots means a lot
more at 100 than 200.

Personally, It seems to me that a speed mod less than $1,000 a knot is
likely a good deal. I presently fly about 142 in a hurry, and 120 when I am
not.

I know the people selling the mods often over advertise, but lets assume we
know the real increase of a given mod from an expert. What's it worth to
you?


I fly a PA28-180. Added the K2U speed mods (all of them) and fly
approx 5-8mph faster than the plane used to. (The performance seems
to be dependent on OAT).

This means I get to cruise @ 140mph loafing, or 150mph pushing it @
8000ft.

Cost was a bit lower than $1k/knot. There are other benefits than
speed though. Climb rate is better, and handling is much crisper with
the aileron and stabilator seals, so there is value there.

One interesting data point. You really need a constant speed prop to
take full advantage of the drag reduction from speedmods. I can
redline my prop close to 10k DA. I've considered repitching to
capture some additional speed, but obviously there would be a loss on
climb. I am also not sure of the legalities in repitcing as the
PA28-180 is only certified for a 58 or 60" prop and I already have a
60" prop.

From a financial standpoint. The speedmods make the plane about 3-4%
faster. So if it costs me approx $60/hr to fly my plane, the
speedmods are saving me approx $2-3/hr. That's a long payback period.
I'm not even sure if that is a fair comparison since that is my hourly
operating cost (including insurance, hangar, etc), and not the direct
(fuel/oil) operating costs, which would be even lower.

-Nathan