Thrust Angles?

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Jolly Roger
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Thrust Angles?

Post by Jolly Roger » 05 Feb 2017, 21:30

Hello tuggers,

I'm quite new to all this powered-flying business and need some advice on thrust angles for the ARTF Cub I'm screwing together.

The firewall seems square to the centre-line of the model in both planes, so I am assuming I don't need to build in any extra downthrust.

But roughly how many degrees right thrust do I need?

Ooh and as a bonus question, has anyone tried mounting electric motors with some rubber washers in an attempt to avoid resonance? Obviously there is a risk that adding elasticity to the fixing could actually make vibrations worse, which is why I've always bolted my motors in tight, but I hear others think it can improve the sound by reducing the whine of the motor.

Thanks for all ideas.

Rog

john greenfield
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Re: Thrust Angles?

Post by john greenfield » 06 Feb 2017, 07:22

Roger

There is not a simple answer too your question as how much down and side thrust will depend on the power of your motor. For a low power (typical Cub scale type flight) you may not need any at all but put a bigger motor in it for towing and you will need some but how much depends on what you are towing and how big the motor is.
It is beneficial with tugs to have a little less downthrust than normal so that the model enters a shallow climb at full power. This coupled to the high tow point that you will have with any Cub model will help keep the tug nose up during the tow.

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)

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Barry_Cole
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Re: Thrust Angles?

Post by Barry_Cole » 06 Feb 2017, 07:34

Rog,
As long as your motor is not over powerful, and you are towing light gliders in the 10-12 lb range, the side and down thrust will not be too important. I towed for years with a 1/4 scale cub powered by a Zen 62, this took excitement to a whole new level.

The Cub is not an ideal tow plane, as the tow point is too high. However if it is fun you are looking for then you will not be disappointed.

And then there are the landings to look forward to.......

:o :o :o :o

BC

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Ray Watts
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Re: Thrust Angles?

Post by Ray Watts » 06 Feb 2017, 16:56

Just starting to look forward to the new FLYING season and everyone starts mentioning landings.
:roll: :roll: :roll:
It's always calmer indoors :D

Jolly Roger
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Re: Thrust Angles?

Post by Jolly Roger » 06 Feb 2017, 21:18

John, Barry, Ray - many thanks - I'm reassured that thrust angles maybe aren't too critical. I'll pop in a degree or two of right for good measure.

My Cub's just for pootling around so won't be highly powered - maybe 2200W for its lightly-built 1/3 scale airframe. If I get the urge to tug (...suggest own double-entendre) then I'll up the Watts.

Thanks again. I'll post a piccy or two when I'm done.

Rog

john greenfield
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Re: Thrust Angles?

Post by john greenfield » 08 Feb 2017, 07:21

I am sure "Watts" will be happy to help. He is not a bad tug pilot !!? :lol:

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)

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B Sharp
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Re: Thrust Angles?

Post by B Sharp » 08 Feb 2017, 19:01

I would avoid the rubber washers or bushes Roger. I tried that with an Extra many years ago back in the dawn of electrical flight. There must have been an imbalance somewhere in the setup but the upshot was that when I opened up the motor to full power the motor plus the firewall shook itself loose and ended op in a blackcurrant bush at the bottom of the garden. After that it was solid mounts for me!
Brian. :?

Jolly Roger
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Re: Thrust Angles?

Post by Jolly Roger » 08 Feb 2017, 21:06

Good to hear from you Brian.

So you can't beat a good solid mount, eh?

I'll bolt it tight for bench testing and see how it goes. Probably be along with more New Member questions in a while.

Best wishes,
Rog

Elliot Howells
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Re: Thrust Angles?

Post by Elliot Howells » 09 Feb 2017, 20:27

Rog,

I find 4 degrees down and right works well for 100cc plus. My 1/4 scale cub has a little, probably more like 2. I'm not sure I'd want to tug with it though, it's a bit 'exciting'...

Ell.

Jolly Roger
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Re: Thrust Angles?

Post by Jolly Roger » 09 Feb 2017, 23:56

Cheers Ell. I think I have about 2 or 3 deg down and right on my 1/5 Cub.

Getting seriously short of excuses not to finish this thing. I could be flying it in literally a matter of just a few years!

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