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Old Dec 15, 2012, 02:00 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,625 Posts
Quote:
Originally Posted by cfircav8r View Post
Being under powered will not make a plane harder to control. Aircraft setup, design, launch technique, and control inputs are the reason for launch problems. Under powered planes just won't climb or hold altitude, but will still be fully controllable, although many people believe that if it won't climb vertically then its under powered. The best thing to do is to learn what forces are involved in the hand launch and the techniques and control inputs needed to control, and/or work with those forces.

That's 'sort of' true but flying a plane that has very marginal thrust is actually really hard because the plane is constantly flying on the edge of a stall, and even doing a gentle turn can cause it to fall out of the sky. Having a little thrust in reserve does make a plane much easier to fly.
Having good thrust also makes hand launching much easier because the plane gets up to flying speed quicker, even if the launch is poor. This is especially true for heavier faster flying models where it's hard to get the plane up to flying speed by throwing alone.

With my 3D models all I have to do is point the plane up, open the throttle, and let go... and away it goes straight up Try doing that with a plane with marginal power.
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Old Dec 15, 2012, 02:42 PM
Registered User
Canada, BC, Port Coquitlam
Joined Apr 2012
1,190 Posts
/\Agree 100%
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Old Jan 01, 2013, 09:29 PM
crazyflyer
Joined Jan 2013
21 Posts
Looks like it stalled.
To much up elev.left at start and right alliron and left dont match up.
It is too slow to get lift, and the too much elev caused it to stall.
At least that's what it looks like to me.
I never give elev off hand until needed.
You know it could be that the motor isn't properly installed you know they shouldn't be on center line. I can't remember the degrees but it should be down and off to one side.
To keep it from going nose up, and to counter torque.
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Old Jan 02, 2013, 07:59 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,173 Posts
Quote:
Originally Posted by JetPlaneFlyer View Post
That's 'sort of' true but flying a plane that has very marginal thrust is actually really hard because the plane is constantly flying on the edge of a stall,
We'll join our contrary opinion, in progress........
Spencer's World Record 468mph Kinetic100DP flight video!!! (6 min 44 sec)


Let's look at the score, shall we?
Hand launch..........................................ch eck!
Unpowered plane--NO thrust................check!
Very hard to fly.......................................DOUBLE check!
Constantly on the edge of a stall...........forgiddaboudiiit!

Above quote...........................................BU STED!

All slope glider and thermal sailplane pilots are coming over to your place to eat all your food and have a little discussion!
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Old Jan 02, 2013, 09:04 AM
Space power
cfircav8r's Avatar
United States, IA, Hampton
Joined May 2012
307 Posts
Most planes that are "under powered" will fly fine if you know how to "fly." Unfortunately too many pilots need lots of power to really haul the plane around the sky. They need to learn to "fly" the plane not "drive" it. I have a Guillows Hellcat that I converted to electric and its wing loading is higher than the upper range of acceptable for a "scale" plane, which happens to be the highest range on the model charts. Add to that the power system is marginal wattage for a plane that weight. It flew great and I never got over half throttle on the maiden. It wasn't difficult to hand launch and was never "on the verge of stall", but you couldn't horse it around like a sport plane.

The point is there was nothing really wrong with that plane and it had more than sufficient power to fly. It was a bad launch and poor piloting that caused the crash nothing more, and until he learns what he did wrong and why the plane did what it did he will always struggle with certain aspects of flying.
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Old Jan 02, 2013, 10:05 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,625 Posts
Quote:
Originally Posted by Rockin Robbins View Post
All slope glider and thermal sailplane pilots are coming over to your place to eat all your food and have a little discussion!
Actually I've flown lots of slope and thermal, I went for many years doing only that. And I can confirm that on a flat field where there is no lift trying to consistently climb or even maintain altitude on a glider is not only hard but IMPOSSIBLE.
If you can throw fast enough and only expect a gradual descent to the ground then even the most underpowered plane is flyable, but when flying power models the expectation is that they can at least stay in the air under their own power. This I'll repeat... is really hard if they are very marginally powered.

Also what is being overlooked is the difference in wing loading and stall speed between the typical sailplane and a typical aerobatic power model. A sailplane usually is easy enough to hand launch (esp. if launching off a hill into a strong wind) but a typical powered sports type model is a lot harder if you don't have some good thrust to help because as a rule the required flying speed is much higher.

The dynamic soarer in the video had LOTS of power.. it was provided by the wind and the hill and gravity. Lets see him do the same thing on the flat or in calm conditions

But the clincher....
All this talk about it being totally pilot error and nothing to do with thrust seems to conveniently overlook the facts of the case:
  • He repeatedly could not launch the plane successfully.
  • He changed the prop and now he has no problems
Obviously he learned how to launch/fly while changing the prop
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Old Jan 02, 2013, 10:41 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,173 Posts
Quote:
Originally Posted by JetPlaneFlyer View Post
The dynamic soarer in the video had LOTS of power.. it was provided by the wind and the hill and gravity. Lets see him do the same thing on the flat or in calm conditions
He couldn't have had TOO MUCH power. He only got to 468 mph... Pass me one of those turkey legs, will you? Just thought that video would be fun here.

Another fun video would be one of the DLG (discus launched glider) boys. They can fly just fine with no lift on a flat field. They wouldn't be all that happy but the planes would fly fine! Let me scrounge around here.......
Threading the Needle -Paul Anderson (1 min 52 sec)
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Old Jan 02, 2013, 11:03 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
11,625 Posts
I've got two DLG's they are great fun, but they have power - The power of the human arm. In a no lift condition it's all downhill after the arm does it's bit.

Here's a couple that give some impression of how much energy the launch gives.

This is my Elf micro DLG with a keychain can velcro'ed onto the wing.. On an 80g model the weight and drag kills the performance stone dead but still interesting.
Elf Micro DLG birds eye view (1 min 34 sec)


View out the rear window:
Elf micro DLG (1 min 18 sec)
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Old Jan 02, 2013, 11:28 AM
buyer of the farm
United States, FL, DeLand
Joined Mar 2009
4,173 Posts
Quote:
Originally Posted by JetPlaneFlyer View Post
I've got two DLG's they are great fun, but they have power - The power of the human arm. In a no lift condition it's all downhill after the arm does it's bit.

Here's a couple that give some impression of how much energy the launch gives.

This is my Elf micro DLG with a keychain can velcro'ed (blah, blah, blah!)
Holy cow! Some of the finest DLG videos I've seen. I love the launch view out the back of the plane. And that looks like amazing fun! Subscribed.

Hey, here's a little test glide from a hand launch. Ignore the title. There's no stunt. This is cool, restful flying at the beach with a DLG plane.
Best soaring stunt you have ever seen (2 min 27 sec)
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