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A Question of Greed?

Old 03-07-2014, 03:13 AM
  #26  
SrTelemaster150
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Originally Posted by 2walla
The two most expensive things on glow fuel are oil and nitro pick something to short to increase profit...

True that.

Methanol is cheaper than gasoline if you can find it in bulk & bring your own containers.
Old 03-07-2014, 05:26 AM
  #27  
Airplanes400
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Originally Posted by CLBetten
My local hobby shop has fuel that has all the same specs except the nitro content for the same price. So 5, 10, 15, and 20% cost the same. I've always ran 10 or 15% and been perfectly happy. Is there any point in getting the 20 or is my temptation to do so likely sparked by being programmed to expect the higher nitro to cost more?
You never mentioned how much the shop is charging. So, how much?
Old 03-07-2014, 06:19 AM
  #28  
SrTelemaster150
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Originally Posted by Airplanes400
You never mentioned how much the shop is charging. So, how much?
Good question since 20% nitro for the market price of 5% is a great deal. 5% for the market price of 20%, not so much.

Last edited by SrTelemaster150; 03-11-2014 at 04:10 AM.
Old 03-07-2014, 06:46 AM
  #29  
JohnBuckner
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Beyond competition purposes, and yes high nitro contents definitely can improve performance when done right and to that end, there is another very important reason for using higher nitro and that is related to geography. This may never be realized by folks that are relative lowlanders.

Density altitude is what all aircraft performance is related to and it effects the aerodynamic lifting surfaces the propellers and the engines. Density altitude is not the same as actual elevation and can on hot summer days easily approach several thousand feet higher than actual elevation. This can have devastating effects on the ability of our RC aircraft or any aircraft for that matter to even leave the ground.

It is common to use relatively higher nitros in high country out west. For example just a short distance from my home field to the west on the Colorado River at an elevation of around 500 feet, the fields down there most use 10% nitro. Now here at my home field the elevation is 3500 feet and density often goes over 5000 well to acheve similar performance as we would down on the river most everyone uses 15% with the same airplanes. Heck every time we go down there its wonderful to fly in that thick air.

Now just a short distance to the east of us on the Mongollon Rim, the club just east of Flagstaff is around 7000 feet elevation and the density altitude in the summer often gets to 9000 maybe a smidge more. The fellows there recommend 25% minimum for two strokes and 35% minimum for four strokes. When the lowlanders insist on using their 10% there the fellows always gather to watch the takeoffs for obvious reasons.

So there really is some very viable reasons for using higher nitro contents and of course good needling techniques must be used, as it is just as easy to burn up an engine using 0% nitro as it is using say 25% if poor engine tuning techniques are used.

Just my opinion

John

Last edited by JohnBuckner; 03-07-2014 at 06:55 AM.
Old 03-07-2014, 08:21 AM
  #30  
SrTelemaster150
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Originally Posted by JohnBuckner
Beyond competition purposes, and yes high nitro contents definitely can improve performance when done right and to that end, there is another very important reason for using higher nitro and that is related to geography. This may never be realized by folks that are relative lowlanders.

Density altitude is what all aircraft performance is related to and it effects the aerodynamic lifting surfaces the propellers and the engines. Density altitude is not the same as actual elevation and can on hot summer days easily approach several thousand feet higher than actual elevation. This can have devastating effects on the ability of our RC aircraft or any aircraft for that matter to even leave the ground.

It is common to use relatively higher nitros in high country out west. For example just a short distance from my home field to the west on the Colorado River at an elevation of around 500 feet, the fields down there most use 10% nitro. Now here at my home field the elevation is 3500 feet and density often goes over 5000 well to acheve similar performance as we would down on the river most everyone uses 15% with the same airplanes. Heck every time we go down there its wonderful to fly in that thick air.

Now just a short distance to the east of us on the Mongollon Rim, the club just east of Flagstaff is around 7000 feet elevation and the density altitude in the summer often gets to 9000 maybe a smidge more. The fellows there recommend 25% minimum for two strokes and 35% minimum for four strokes. When the lowlanders insist on using their 10% there the fellows always gather to watch the takeoffs for obvious reasons.

So there really is some very viable reasons for using higher nitro contents and of course good needling techniques must be used, as it is just as easy to burn up an engine using 0% nitro as it is using say 25% if poor engine tuning techniques are used.

Just my opinion

John
All of your points are valid & very good information. I would have to say though, that your estimation of increases in DA could very consevative in some parts of the country. Perhaps due to the low relative humidity in you location.

DA not only affects aircraft lift, it affects any internal combustion engine's power output.

When I drag raced my 2006 Charger, I have seen DA as high as +3600' in the summer @ NJ drag strips that were 50' above sea level & as low as -2600 in the spring & fall @ those same tracks.

Spring & fall were the times that records were broken, but only on "crisp" days.

Cold, damp days reduced power output because of increased DA due to humidity & reduced traction making hook up more difficult.

All the more reason to have a little extra nitro in the fuel for such variables when aircraft performance (lift) is a factor.

The only draw back of a little more nitro, within reason, is the decrease in fuel economy that goes with it.

Last edited by SrTelemaster150; 03-07-2014 at 08:23 AM.
Old 03-07-2014, 11:32 AM
  #31  
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Well now we have all told everyone just how knowledgeable we are about all things nitro and played at who’s the best at baffling the public with terms like altitude density for all anyone gives a hoot. Just wonderful to hear ourselves slide those things off the tongue can someone actually answer the original posters question? Or does anyone even remember what it was? If not here ya are.

"My local hobby shop has fuel that has all the same specs except the nitro content for the same price. So 5, 10, 15, and 20% cost the same. I've always ran 10 or 15% and been perfectly happy. Is there any point in getting the 20 or is my temptation to do so likely sparked by being programmed to expect the higher nitro to cost more? "

I'll give it a try. If you’re perfectly happy why would you want to change? What you’re doing is just fine. You might not even notice the difference after all.
Dennis
Old 03-08-2014, 07:16 PM
  #32  
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A few messages and a few replies were deleted. Thanks to those who kept their cool and offered good advice. For some reason, my message earlier that I was locking this thread didn't post. I had to be somewhere this evening and I thought everyone would be notified that I had locked the thread.

Last edited by blw; 03-08-2014 at 07:20 PM.
Old 03-09-2014, 11:54 PM
  #33  
CLBetten
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The cost on the fuel is $19.95 per gallon and it is Powermaster. It sounds like with my stock engines I will get just as much or more flying time with the 15% I'm used to. The reason I mentioned "greed" is due to the fact I wouldn't have even considered the 20% if it were priced higher than the others.
Old 03-10-2014, 04:13 AM
  #34  
JohnBuckner
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Good morning if 15 is what you feel comfortable with then great stick with it. I did google Clinton and found that your elevation is 4400 hundred feet and during the hot summer yes your density altitude goes up considerably and since your airplanes performance responds to density altitude you may find that the 20 would surprise you. That of course is up to you and I suggest you ask what your fellow club members tend to use.

You are right at the elevation point in the summer that slightly higher nitro content would make your flights more enjoyable.


John

Last edited by JohnBuckner; 03-10-2014 at 04:17 AM.
Old 03-10-2014, 04:22 AM
  #35  
SrTelemaster150
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Originally Posted by CLBetten
The cost on the fuel is $19.95 per gallon and it is Powermaster. It sounds like with my stock engines I will get just as much or more flying time with the 15% I'm used to. The reason I mentioned "greed" is due to the fact I wouldn't have even considered the 20% if it were priced higher than the others.
That price for single gallons is pretty reasonable even for the lower % fuel. Run the least amount of nitro % that gives you satisfactory performance as the higher % will require a richer needle setting & degrade fuel economy. As JohnBucker pointed out, you might use a higher % of nitro, W/the required needle adjustment, will be needed during the hot, humid summer season to maintain a satisfactory (to you) performance level.

Last edited by SrTelemaster150; 03-11-2014 at 04:02 AM.
Old 03-10-2014, 09:48 PM
  #36  
CLBetten
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Good advise. I've learned a lot from everyone. I'm surely not out anything to experiment a little. Altitude does play a big role here. Especially when discussions turn to prop size. On average for my .25 to .90 engines I find I lose about an inch in diameter. High humidity here is almost non existent.
Old 12-11-2014, 04:27 PM
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Having been trained as a mechanic we were trained well trained in the dangers of gasoline, it will in fact ignite and burn from a burning match or spark, it will not ignite from a hot wire. In a full open container or a part filled container with a opening equal to or exceeding it's area (in most but not all cases) it will only burn and not all that impressively at that, however when in a partly filled container or room where the openings are small the vapors will accumulate and when ignited expand so rapidly and with such heat as to cause an explosion. So anytime the vapors can accumulate there is danger.
Old 12-11-2014, 04:38 PM
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As a healthy young man I got altitude sickness in Flagstaff thought I was having a heat attack so I can verify the air is thinner.

Jay

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