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Value of a knot



 
 
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  #1  
Old September 6th 04, 09:51 PM
Dude
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Default Value of a knot

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?



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  #2  
Old September 6th 04, 11:27 PM
Ben Jackson
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Default

In article ,
Dude wrote:
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.


They're probably not worth much of anything until you're talking about
airplanes with stock speeds in the 160kt+ range. That seems to be the
speed aircraft designers can easily get by going to 250-300hp. Getting
beyond that requires smarter aerodynamics.

For example, the price difference between a similar vintage Piper
Cherokee 235 and Comanche 250 is $10-15,000 (based on a quick look
at TAP). If you put $15,000 worth of speed mods (ie all of them) on
a 235 it still doesn't go as fast. The same is probably true of the
Warrior - 235 upgrade.

Once your stock speed is up around 160kt it might cost less to add STCs
than to upgrade to a faster model, but the returns have diminished
significantly. I'm not aware of any combination of mods that take a
160kt stock airplane and give you 180kts (with the possible exception
of an aftermarket turbo, if any still exist). Even that only saves you
20 minutes on a 3 hour trip.

If you're flying long distances and want to cut the total time, the most
cost effective way is to carry enough fuel that you don't have to stop.
If you can cut a 30 minute fuel stop out of a C-172 flightplan it's like
adding 15kts.

--
Ben Jackson

http://www.ben.com/
  #3  
Old September 7th 04, 12:13 AM
Aaron Coolidge
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Default

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.

This isn't really what you asked, but its been bothering me for a while.
The most cost-effective speed mod that I have ever seen is:
Ram air knob on an '83 Mooney 201. It adds 0.5 to 0.75 inches of MP at
full throttle, and is worth 3 knots. My friend, the owner of the Mooney,
won't bother using it because "It's too much trouble, and it's not worth it".

I keep reminding him that us Cherokee owners spend over $3000 to get a 3-knot
increase, and he can have the same for FREE!

--
Aaron Coolidge



  #5  
Old September 7th 04, 04:35 AM
Elwood Dowd
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Amen brother. Range was one of the main reasons we chose our Beech
Sierra---only 135-ish knots, but 6+ hours aloft make us faster than a
Bonanza on some trips. Not all, but some. Heck, if you have a Mooney
you get higher speed AND more range (but less headroom).

To answer the original question, if I could spend $1000 to get 5 knots I
would do it, but not 1. If I could spend $5000 and be guaranteed 5
knots I would think about it. If I could spend $10,000 on a turbo that
would take me up higher when I need to climb to be safe, I would
seriously think about it, but I wouldn't count on it to give me lots
more speed.

Regarding range---I have found that for our plane at least, a LOT of
fuel savings can be had by flying at 10,500 rather than 6,500. Speed is
very nearly the same while fuel use drops to about 8.9gph, vs. 10.5 at
the lower altitude. This is not a linear relationship and drops off
above about 13,500. I will leave it to the math weenies to tell me
exactly how long I have to fly for a given leg to get a positive return
from amortizing the climb, but on really long legs I always go up high
and it always pays off.
  #6  
Old September 7th 04, 07:19 AM
tony roberts
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My own view - who cares?
I fly because I love to fly - not because I want to get from A to B in X
amount of time. I have friends who go Waaaay faster than me - and they
burn 14gph. I plod along burning 8gph. I love to fly.They get there much
faster and fly a lot less. I doodle along at my 8GPH, and take way
longer than them. There are faster ways of getting there - but that
isn't why I'm flying. I'm flying because I love flying. So how much
would I pay to fly faster? Very little. How much would I pay to get
shorter and safer take-offs from short high density altitude strips?
Lots.

Tony


--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE


In article ,
"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?





--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE
  #7  
Old September 7th 04, 07:53 AM
Bela P. Havasreti
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Default

On Mon, 06 Sep 2004 20:51:16 GMT, "Dude" wrote:

For 1-3 hour trips, I wouldn't spend anything (well, not $1,000
anyway) to go faster.

I fly a B model 170. All my flying buds own 180s (or 182s). On a one
hour trip, I'm 15 minutes behind them when I show up (they're just
pulling beers out of their coolers), two hour trip, perhaps 25-30
minutes, etc. I burn 7.? gallons per hour. They burn 14 (or more).
When my airplane breaks, a C-note gets it going again. When theirs
breaks, it's more like 5 C-notes.

I could put a cruise prop on my airplane, little baby tires and wheel
pants, perhaps try to trim a few pounds off of it and then it'd cruise
at 118-120 mph instead of 112 mph (I've got a climb prop on mine
and 850 tires).

Bottom line, if you bought every speed mod available for your type
of airplane, the cost to do so might be tough to justify over the
long-run. In my cause, it would be cheaper to pass the 170 on
to someone else who will enjoy it for what it is and go out and buy
a bone-stock (early) C-180.

Bela P. Havasreti



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?



  #8  
Old September 7th 04, 01:45 PM
Nathan Young
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Default

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

  #9  
Old September 7th 04, 03:07 PM
Paul Sengupta
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Default

"tony roberts" wrote in message
news:[email protected]
My own view - who cares?
I fly because I love to fly - not because I want to get from A to B in X
amount of time. I have friends who go Waaaay faster than me - and they
burn 14gph. I plod along burning 8gph. I love to fly.They get there much
faster and fly a lot less. I doodle along at my 8GPH, and take way
longer than them. There are faster ways of getting there - but that
isn't why I'm flying. I'm flying because I love flying. So how much
would I pay to fly faster? Very little. How much would I pay to get
shorter and safer take-offs from short high density altitude strips?
Lots.


Ok, how about turning this around. Each person has their own value
on speed and time...obviously someone who could make $100,000 a
sale and could do three a a day instead of two by going 10 knots faster
would find speed worth it! But...if you're talking about aerodynamic
clean-ups...the collorary to that is if you want to go the same speed,
how much fuel does it save you? It would save more money here in
Europe where fuel is much more expensive.

So how much would you spend to save how much on fuel?? :-)

The ultimate here where kerosene is 1/3 the price of avgas would be a
diesel conversion.

Paul


  #10  
Old September 7th 04, 03:15 PM
Paul Sengupta
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Default

"Paul Sengupta" wrote in message
...
...the collorary to that is if you want to go the same speed,


Corollary...

Brain/finger mismatch.

Paul


 




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