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Old May 08, 2008, 09:22 PM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
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Mini Pulse XT at 14,240 ft.? Let's find out!

So yeah, I live about an hour and a half from Mt. Evans in Colorado. It currently sports the highest paved road in the world. The road ends at a large parking lot adjacent to an observatory on the peak.

I'm thinking of taking my MP-480 up there and seeing if I can get away with flying it as high as one has possibly ever been flown. Think it'll work?

I'm thinking a 13-7 or 8 prop. On a clear, relatively calm day.

I may try and recruit a videographer to come along and document.

Anyone interested in seeing this?

Evvy

EDIT: It turns out that there is a 16,000 ft paved road somewhere in the Alps... But who's counting, right? Search Mt. Evans, it's very cool.
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Old May 08, 2008, 09:55 PM
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GoldCraft's Avatar
United States, GA, Woodstock
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Id go with a 13x5.5....need more bite in the thin air.
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Old May 09, 2008, 06:54 PM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
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Quote:
Originally Posted by GoldCraft
Id go with a 13x5.5....need more bite in the thin air.
I'm still a bit unclear about how prop-pitch works in the real world. I keep getting conflicting answers from people.

So you think I should pitch down in thinner air?

I normally fly at around 6000 ft. Most people are using 11x7e's on their 480's, should I be using a lower pitch?
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Old May 09, 2008, 07:37 PM
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Quote:
Originally Posted by Wingwrecker
I'm still a bit unclear about how prop-pitch works in the real world. I keep getting conflicting answers from people.

So you think I should pitch down in thinner air?

I normally fly at around 6000 ft. Most people are using 11x7e's on their 480's, should I be using a lower pitch?
Its kinda misleading the way the numbers work ...a 5.5 has more pitch ....in a perfect world the plane would move 5.5 in. in one revolution where a 7 would move 7 in.....so a 5.5 has more bite but less top end speed. In very thin air more bite and more prop length would be better to get the plane moving in the thin air. At 6k the 11x7 may be fine .....but 14k is a new game. A 12x6 may work for you as well. I would take a few different ones ....put them on ....hold the plane and hit 3/4 throttle and see if she has strong pull.
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Old May 09, 2008, 09:02 PM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
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Quote:
Originally Posted by GoldCraft
I would take a few different ones ....put them on ....hold the plane and hit 3/4 throttle and see if she has strong pull.
Good call, that's what I'll do. Thanks.
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Old May 10, 2008, 09:52 PM
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I fly in Colorado also. I'm not sure what Goldcraft is talking about when he says a 5.5 has more bite. More pitch is more bite. A flat prop has no bite, and a 5.5 is flatter than a 7. I've flown at Fairplay in the summer and you need a little more diameter and a lot more pitch. I normally fly in Grand Junction approx. 5000 ft. elevation. In the summer the density altitude can reach over 8000 ft. Most of my planes require 1" more diameter and 1" to 2" more pitch to perform like sea level. On Mount Evans this summer I would think you would need much more than that.
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Old May 11, 2008, 08:20 AM
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See what I mean? Arrgh...
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Old May 11, 2008, 10:23 AM
Faster!
Joshua Wesley's Avatar
United States, NV, Sparks
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Wingwrecker,

When you get to the mountain, add pitch until you reach the same amp draw you have in Parker. That's all you can do. The only other thing to remember is that the stall speed of the aircraft from your point of view will be faster. Make your approach turns shallow, and a little faster than normal. Let us know how it went!

-Joshua
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Old May 11, 2008, 10:37 AM
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Quote:
Originally Posted by Joshua Wesley
Wingwrecker,

When you get to the mountain, add pitch until you reach the same amp draw you have in Parker. That's all you can do. The only other thing to remember is that the stall speed of the aircraft from your point of view will be faster. Make your approach turns shallow, and a little faster than normal. Let us know how it went!

-Joshua
Good advise....
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Old May 11, 2008, 11:16 AM
WAA-08 THANK FRANK!
JimNM's Avatar
Las Cruces, New Mexico, United States
Joined Jun 2002
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For your consideration...

DIAMETER governs THRUST - larger # = MORE THRUST
PITCH governs SPEED - larger # = MORE SPEED

To double you altitude, (wild donkey guess follows...) +2" Diameter and +3" to +4" on pitch. A "windless" day on top of a peak in the Rocky Mountains is not bloody likely. Good luck - take an amp meter and several LARGE props. Test by holding the plane nose up, by the wingtip and apply throttle. If there is enough power to fly, the plane will come to almost level - if the plane wants to walk all the way around the wingtip that you are holding... then you have good power to weight.
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Old May 11, 2008, 01:34 PM
Who needs a pilot??
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Alexandria, VA
Joined Jul 2002
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I'll double up 1966's post about more pitch. Goldcraft, I think you have it backwards. More pitch for the 7" prop means it'll bite more air each rev than a 5.5". I'm a low-land flier relative to this discussion, but thought I'd chime in. For the same engine, if you wanted more top-end speed, you want to increase pitch and drop diameter so you keep the load roughly the same but have the ability to eat incoming air (versus a flat prop). If you need low-end thrust, up the diameter and drop a pitch because airspeed is slower and with the lower-pitch, the engine can unwind a bit more and the flatter pitch but lower airspeed match up just fine.

I'm sure for a brief moment you'll be the highest model airplane in the world! Whoa!

Nice idea :-)
Dan
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Old May 11, 2008, 02:10 PM
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Quote:
Originally Posted by danstrider
I'll double up 1966's post about more pitch. Goldcraft, I think you have it backwards. More pitch for the 7" prop means it'll bite more air each rev than a 5.5". I'm a low-land flier relative to this discussion, but thought I'd chime in. For the same engine, if you wanted more top-end speed, you want to increase pitch and drop diameter so you keep the load roughly the same but have the ability to eat incoming air (versus a flat prop). If you need low-end thrust, up the diameter and drop a pitch because airspeed is slower and with the lower-pitch, the engine can unwind a bit more and the flatter pitch but lower airspeed match up just fine.

I'm sure for a brief moment you'll be the highest model airplane in the world! Whoa!

Nice idea :-)
Dan
Yeah , I agree after rethinking it . I was thinking more low end thrust would be needed. I know my boat is much quicker to accerate with a 17 pitch prop v. a 21 but has less top end....must not work the same in air.
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Old May 11, 2008, 02:49 PM
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Gold Craft, you're absolutely right about the pitch and acceleration, but water density is always the same unlike air. Plus, internal combustion engines loose power at higher elevations (unless they are supercharged) and sometimes cannot turn any increase in pitch or diameter. An electric motor performs in either condition and will need to be loaded more when higher.
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Old May 11, 2008, 03:19 PM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
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Quote:
Originally Posted by danstrider

I'm sure for a brief moment you'll be the highest model airplane in the world! Whoa!

Nice idea :-)
Dan
Thanks. I'm hoping the moment is not TOO brief!

Quote:
Originally Posted by JimNM

A "windless" day on top of a peak in the Rocky Mountains is not bloody likely.
Yeah, I'll be checking the wind forecasts and keeping my fingers crossed.. If I can get a day with 15 mph or so winds, I will be fine. That seems to be all we have here in Denver during the spring and I've grown pretty accustomed to it. Whoever named Chicago the 'Windy City' has obviously never been to Denver!

So thanks guys for all the input. I'm definately going with 13" dia. I'll have to check what kind of pitches I can get at that size. I'm thinking that a 13-8 to 13-11 is the range I want to be in. I'm new to EF so I don't own a watt-meter yet, but I will get one, learn how to use it and bring it with me.

Just need to find someone with a video camera or get a 5-in-1 for my hat.

The road doesn't open till the end of this month and I'll give it a week or two for the opening season crowds to subside a bit so that I can have some landing space.

Hope I don't get hassled by a park ranger! The ticket will be worth it, either way...

I'll keep you guys updated, In the mean time all suggestions are very welcome.

Thanks again,
Evvy
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Old May 11, 2008, 04:17 PM
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Quote:
Originally Posted by A1966C150F
Gold Craft, you're absolutely right about the pitch and acceleration, but water density is always the same unlike air. Plus, internal combustion engines loose power at higher elevations (unless they are supercharged) and sometimes cannot turn any increase in pitch or diameter. An electric motor performs in either condition and will need to be loaded more when higher.
Yeah...plus the big issue for a boat is cavatation....higher pitch props tend to cavatate when you try to accelerate to fast from dead stop in water . A fluid dynamic thing

But I understand the need to load up the motor more for electrics now.
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