Help! Tiny Trainer doesn't fly

[Harry Joelsson]

I scratch build a Tiny Trainer and used the Power Pack A. I checked CG and thought it was ok.

Here's what happened:

https://imgur.com/a/JOPIV8F

Two complete nosedives. Any ideas? The CG was fine, I don't think that's the issue. Perhaps wond but it was light today and the same thing happened both times.

 

[Merv]

... Any ideas?...

It looks like the prop is not correct. It looks like is is pushing not pulling.
The numbers on the prop need to be facing the direction of travel. If the numbers are facing the other way, the prop will only produce about 40% of the expected thrust. Make sure it is spinning the correct way.

The plane should produce enough thrust to be pulled from you hand.

 

[Mr NCT]

I scratch build a Tiny Trainer and used the Power Pack A. I checked CG and thought it was ok.
View attachment 246696 View attachment 246697 View attachment 246698
Here's what happened:

https://imgur.com/a/JOPIV8F

Two complete nosedives. Any ideas? The CG was fine, I don't think that's the issue. Perhaps wond but it was light today and the same thing happened both times.

Along with what @Merv said it looks like your prop is a clockwise instead of the normal counter clockwise. The video does look like it's pushing backwards.

 

[Harry Joelsson]

It looks like the prop is not correct. It looks like is is pushing not pulling.
The numbers on the prop need to be facing the direction of travel. If the numbers are facing the other way, the prop will only produce about 40% of the expected thrust. Make sure it is spinning the correct way.

The plane should produce enough thrust to be pulled from you hand.

How do I know the prop is spinning the right way? Clockwise relative to which direction?

 

[Harry Joelsson]

Along with what @Merv said it looks like your prop is a clockwise instead of the normal counter clockwise. The video does look like it's pushing backwards.

Counter clockwise relative to which way

 

[Mr NCT]

CCW as you look from the back of the plane.

 

[Harry Joelsson]

CCW as you look from the back of the plane.

Ah! I think that's it. I had thought in my head it spins clockwise, perhaps since real aircraft do that. Will try again!

 

[Merv]

How do I know the prop is spinning the right way? Clockwise relative to which direction?

CW or CCW rotation depends on which prop you have. The prop should pull the plane forward.

 

[Mr NCT]

Ah! I think that's it. I had thought in my head it spins clockwise, perhaps since real aircraft do that. Will try again!

Sorry, I was totally wrong, it's CW looking from the back of the plane. (I'm blaming it on pain meds)

 

[Mr NCT]

You look like you have a reverse pitch prop on the plane

 

[Harry Joelsson]

You look like you have a reverse pitch prop on the plane

Ok, explain what that is. Can my problem.be solved if I just flip the prop the other way so the numbers point backwards

 

[Harry Joelsson]

You look like you have a reverse pitch prop on the plane

These are what I'm using

 

[Mr NCT]

These are what I'm using
View attachment 246705

Are they all pitched in the same direction?

 

[Harry Joelsson]

Are they all pitched in the same direction?

Yes

 

[Mr NCT]

Which way does your prop spin? Does it try to pull?

 

[Harry Joelsson]

Which way does your prop spin? Does it try to pull?

I figured it out; the pros I bought were NOT all the same pitch, but rather half were CW and the others were CCW. I had the wrong props on. I can feel the air flowing back over my hand now when I hold the plane. Guess I'll just pay more attention to which prop I'm using in the future. Thanks for all the help.

 

[Merv]

Ok, explain what that is. Can my problem.be solved if I just flip the prop the other way so the numbers point backwards

NO!
The numbers on the prop ALWAYS face the direction of travel. It doesn't matter if the prop is reverse pich or not. Also doesn't matter if the prop is in the front or in the rear (a tractor or a pusher). The numbers always faces the front, the direction of travel.

To use a reversed pitch prop, you need to reverse the spin of the motor. You do it by swapping any 2 of the 3 wires going to the motor. It doesn't matter which 2, just swap them.

 

[Mr NCT]

Just remember that the tiny trainer has thrust angle built into the power pod. If you put on a prop and reverse the motor you will get too much pull to the right. It's set up for the prop to spin CW as you look at it from the back.

 

[Merv]

I agree using a reverse pich prop is not ideal, but the plane will fly just fine. I've done it many times. There is a bit of yaw action going on when you go from gliding to full throttle. A untrained eye may not even notice it.

A reverse pich prop does change how a plane knife edges. My planes always knife edge better to the right. With a reverse pich prop they are better to the left.

 

[Harry Joelsson]

I switched the motor rotation and it worked... finally! So happy to get my first sucsessful flight. Only problem I've had is that since the motor is spinning in the adverse direction it was designed the spinner nut unscrews itself sometimes. I've found that when the props have an R on them, like "6045R" it means they are reverse props. Now this is where it gets confusing. The prop spin direction is relative to the front of it, unlike the motor spin direction. I think this is because for multirotors you look at the prop from the top down. So, a "standard prop" is actually considered to be spinning CCW.