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Old Jul 26, 2011, 09:06 PM
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United States, AZ, Mesa
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Originally Posted by chalmrast View Post
And it travels even better under water!
So why can't I hear anything if I have water in my ears?
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Old Jul 26, 2011, 09:07 PM
Pusher jets rule!
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Mesa, AZ
Joined Jan 2006
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Ha! Good one Bill!

Pat
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Old Jul 26, 2011, 09:57 PM
Totally!!
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USA, AZ, Tempe
Joined Jan 2009
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6 am for sure, everything reach's is max volume at 6am.
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Old Jul 26, 2011, 10:11 PM
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Gilbert, AZ
Joined Jun 2008
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Originally Posted by bolibruch1 View Post
6 am for sure, everything reach's is max volume at 6am.
But everything is utterly silent at 1am considering I never heard Craig roll up.
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Old Jul 26, 2011, 10:28 PM
TAFTS
Chandler, AZ
Joined Apr 2008
323 Posts
Easy there boys on the "more thrust makes plane go up" explanations. While it is accurate technically, the effects on models like the Stuka are minimal. Take any properly 'trimmed' model and vary the throttle between half and full and you will notice very little change. What little change there is is more a function of the total airspeed increasing than the prop wash, which usually only covers a small portion of the wing.

This effect of "adding throttle makes plane go up" is more influenced by other factors such as airfoil, thrust line, and airplane rigging. Lets look at each:

Airfoil: A flat bottom or high lift airfoil is very sensitive to speed changes. This is the major reason R/C trainers don't make good R/C trainers. The slightest throttle change affects pitch trim. To see the effects of this, play with a slow stick or have someone take you for a ride in a typical GA airplane (Cessna, Piper etc).

Thrust Line: The more flat bottom the wing, the more down thrust we add. As we add more thrust, the motor pulls the nose down to counteract the increase in lift due to higher airspeed. On a well designed trainer, this negates most of the pitchyness with throttle changes. This is NOT the case on a slow stick with zero down thrust. A few washers here can make a lot of difference

Airplane Rigging: The stab incidence can affect speed/pitch sensitivity but is the least likely culprit on most models, especially the Stuka. The smoking gun on the Stuka is most likely the Aileron/Flap rig. They are detached control surfaces that are difficult to get just right. When I test flew the first one from the Distributor, we spent a few flights just getting them rigged right. We used an incidence meter in the original build but found the plane to be pitch sensitive. We checked the thrust line and thought it was pretty good. As we messed with the flaps, we were able to get the plane trimmed to have little to no noticeable pitch change through the throttle range from half to full. Below half, you get into a different kind of flight (gliding) and you will certainly need to re-trim or carry a little elevator as you slow down.

If you need a better explanation of any of these ideas or principles, go to the field with someone knowledgeable and go through the trimming process. Its not uncommon for a pattern or IMAC pilot to spend several flights trimming the model so the trim won't change with throttle setting. You'll learn why you need a down-line mix and why dihedral is good/bad.

Hope this helps. I don't get out much but would gladly help anyone that wants it. We'll save right thrust for another day.

Scott
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Old Jul 26, 2011, 10:37 PM
Gilbert, AZ
chalmrast's Avatar
Gilbert, AZ
Joined May 2007
3,564 Posts
What is the proper trim setting for a scrape-n-go???

Chad
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Old Jul 26, 2011, 10:42 PM
Frankenstein recycled packs
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USA, AZ, Gilbert
Joined Jan 2006
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HELP then. Why, with this much down thrust does this plane climb like a banshee at WOT? Like Rob's Stuka, 3/4 down elevator to maintain level flight. Then the real issue starts, either I don't know how to maintain flat flight and turn at the same time (down + left or right aileron) or there is some nasty coupling.
I am pulling around 1200 watts. 6S 5000 pack, cg close to suggested and I can/have played with it some.
I have not checked ailerons, there are no flaps, but maybe someday when you and I are there...

My last one was great. I had much less down thrust and I could knife edge with my left hand on the rudder only. This one... forget it. [shrugs]

Rick
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Old Jul 26, 2011, 11:00 PM
Pattern Abuser
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Gilbert, AZ
Joined Apr 2008
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Perhaps we need a seminar/workshop. The Texan climbs like crazy too and it appears to have appropriate down thrust. I am hesitant to add any more.
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Old Jul 26, 2011, 11:03 PM
Jeremy-I'm crash proof!
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USA, AZ, Gilbert
Joined Mar 2008
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To be honest I thought all or most planes climbed with more power applied??? Just seemed to make sense to me.
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Old Jul 26, 2011, 11:23 PM
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Gilbert, AZ
Joined Jun 2008
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Originally Posted by rampman View Post
HELP then. Why, with this much down thrust does this plane climb like a banshee at WOT? Like Rob's Stuka, 3/4 down elevator to maintain level flight. Then the real issue starts, either I don't know how to maintain flat flight and turn at the same time (down + left or right aileron) or there is some nasty coupling.
I am pulling around 1200 watts. 6S 5000 pack, cg close to suggested and I can/have played with it some.
I have not checked ailerons, there are no flaps, but maybe someday when you and I are there...

My last one was great. I had much less down thrust and I could knife edge with my left hand on the rudder only. This one... forget it. [shrugs]

Rick
is there anyway that the wing or horizontal tail incidence is different from the last one?
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Old Jul 26, 2011, 11:51 PM
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Gilbert, AZ
Joined Apr 2008
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Originally Posted by neck View Post
To be honest I thought all or most planes climbed with more power applied??? Just seemed to make sense to me.
As Scott mentioned it depends on the airfoil/wing design. On my pattern plane I have near symmetrical wings so I get ZERO climb or dive regardless of inverted or upright, up line or down line. BUT, this took about 10 trim flights to get the CG and lateral balance perfect. Then I added just a touch of down elevator trim which is simply a personal preference that helps me on my down lines and stall turns.

Again as Scott mentioned, it takes a VERY knowledgeable and experienced precision pilot to really trim out a plane and diagnose CG and lateral balance issues. As an reference point, that would NOT be me. AJ, the designer of my airframe, spent an entire morning working with me to "get it perfect".

But all that is not necessary for sport flying, but it can greatly enhance your experience and fun when you are not fighting the aircraft.

But this is just bla bla bla. These radical climbing issues are likely a different set of problems.

Scott knows what he is talking about. It would be cool to drag him out to the field for some diagnostic sessions.

Cheers,

Jim
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Old Jul 27, 2011, 09:41 AM
TAFTS
Chandler, AZ
Joined Apr 2008
323 Posts
Rick, if memory serves me right, your airplane has a VERY flat bottom wing. As pointed out by several people, Lift101 says more speed is more lift. That down thrust was put there to counteract that. I helped someone with a chinglish copy of another trainer a few years back and the stab was very positive which contributed to a severe pitching moment it had.

When I designed/built my full size biplane, I analyzed the crap out of it to try to get the incidences right. The airplane started life as another design and I put too much faith in his work. My work kept disagreeing with the original designers and I just was hesitant to take the leap of faith. So I split the difference and built it in the middle. Damn! I was closer than he was. It took a lot of work to get it to fly the way I wanted and its still not totally correct. If you look at the photo, you can see the gap at the front of the stab where I added washers to change the incidence. In addition, bipes have some odd characteristics related to down wash interaction we can talk about later. Most chinglish R/C models don't spend much R&D or test flying time so you get what you get.

Speaking of knife edge, with a little help from those mixers you don't like, you can make a closely trimmed model knife edge much better. I'm happy to make appointments to help. It might cost you a Diet Coke or two.

Thanks for the words Jim. Most people hear bla bla bla when I talk, but thats normal, like McDonalds

Scott
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Old Jul 27, 2011, 09:48 AM
TAFTS
Chandler, AZ
Joined Apr 2008
323 Posts
Oops, forgot the photo and couldn't figure out how to add it after posting...

"What is the proper trim setting for a scrape-n-go???"

This a very Technical issue which I'm sure is way above the head of most of our readers.

Lets just say you could make it normal, like McDonalds...
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Last edited by Scott Todd; Jul 27, 2011 at 10:22 AM.
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Old Jul 27, 2011, 11:14 AM
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United States, AZ, Queen Creek
Joined May 2004
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Quote:
Originally Posted by chalmrast View Post
What is the proper trim setting for a scrape-n-go???

Chad
It is typically a bit more down AFTER the scrape and go.
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Old Jul 27, 2011, 02:46 PM
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fly4fun's Avatar
Gilbert AZ
Joined Jun 2001
9,323 Posts
Quote:
Originally Posted by Scott Todd View Post
Oops, forgot the photo and couldn't figure out how to add it after posting...

"What is the proper trim setting for a scrape-n-go???"

This a very Technical issue which I'm sure is way above the head of most of our readers.

Lets just say you could make it normal, like McDonalds...
\

Scott does that airplane Quality for LSA registration. Actually I'm guessing it's ESLA.

I see in the FAA Database Its Experimental built. Of course it is.
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