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Old May 21, 2006, 11:55 PM
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EDF Harrier VTOL & Reaction Control


There are quite a few posts on RCG that touch on generalised aspects of creating an EDF RC Harrier. I thought I might create a specific thread for VTOL, Reaction Control and Transition of a RC Harrier.

I may be wrong, but I couldn't find any information on any successful attempts using EDF on a Harrier for VTOL.

Currently I'm exploring the concepts based around a Wemotek Midi Fan and Hacker engine.
EDIT: This system is now being developed with a Schuebeler DS-94 (120mm fan) and a Lehner 2240-17 motor.

My inlet and outlet ducting has been made from glass and carbon and it's pretty light.
I've had a guess at the outlet ducting and I'm sure I'l have to make afew versions before I get it right.
At this stage it seems that for an EDF it's not so much about pressure but flow volume so designing the ducting behind the fan I should consider this heavily so as I don't have to have any (much) weight geared towards flow restrictors and diverters etc.

I'll also try and post some Harrier Flight Manual FOD and Stability issues I have sourced.

Any comments?
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Last edited by Psionic001; Mar 08, 2008 at 01:01 PM.
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Old May 22, 2006, 12:00 AM
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Here are some important images I sourced from an old Warbird Series.
I think they are originally from the AV-8A flight manual and discuss some concepts I have not seen on RCG.
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Old May 22, 2006, 12:08 AM
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I wish you luck.

gene
Old May 22, 2006, 12:24 AM
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Yes, interesting. I'll be watching....
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Old May 22, 2006, 05:11 AM
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The harrier now has fences on the underside to try to contain the jet fountain. There are two long longitudinal fences which combine with the gear doors when they are lowered to form a box.
Old May 22, 2006, 06:33 AM
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in my thining i would chose a larger brushless motor and make a long rod to set the motor back. airflow is the most important thing to think about. also the harrier has one vent on each corner that comes from the motor. one on the nose, each wingtip and on the tail. check out the vtol section
Old May 22, 2006, 06:36 AM
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Quote:
Originally Posted by Giz
The harrier now has fences on the underside to try to contain the jet fountain. There are two long longitudinal fences which combine with the gear doors when they are lowered to form a box.
Yes, such a simple inclusion created an extra 1800lbs thrust when used with the Pegasus MK103 (or 105 I think) without a single mod to the engine. I don't understand how that works but I'd like to know.
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Old May 22, 2006, 06:45 AM
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Quote:
Originally Posted by flyboy367
in my thining i would chose a larger brushless motor and make a long rod to set the motor back. airflow is the most important thing to think about. also the harrier has one vent on each corner that comes from the motor. one on the nose, each wingtip and on the tail. check out the vtol section
I have been thinking a lot about the reaction controls and how to keep them light weight.

I was thinking of using carbon tubes with carbon sleeves on them. The inner tube having a hole in it so when the sleeve slides back the hole is exposed.

The setup would be easy with servos on Y-Leads. Also, to avoid thrust changes in hover when using the reaction controls, I would keep each open about 50% in the neutral position. When rolling right for example, The RHS would close the remaining 50% whilst the left would open to 100%.

Same system would probably work with both the pitch and yaw control too.
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Old May 22, 2006, 07:23 PM
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If you get one to work where all others have failed I'll buy 2. I'm sure you'll make a small fortune if you get an EDF Harrier to work.
There is quite a few threads about this but none recently that I can remember.
Scott
Old May 22, 2006, 10:33 PM
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HI

I have had a few ideas and the Idea of using the carbon rod is useful as it can also be the spar for the wing.
I have tested using a wemotec micro Fan feeding to 1 inch tubes as a reaction control as it can provide 500gms thrust - just enough to tilt one way - but not 2 as it will require.

When connected to 4 outlets with 2 running (eg tilt forward and to the side), there was not alot of thrust to tilt the 4kg test rig.

regards
Brenton
Old May 23, 2006, 03:25 AM
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Quote:
Originally Posted by wildtech
HI

I have had a few ideas and the Idea of using the carbon rod is useful as it can also be the spar for the wing.
I have tested using a wemotec micro Fan feeding to 1 inch tubes as a reaction control as it can provide 500gms thrust - just enough to tilt one way - but not 2 as it will require.

When connected to 4 outlets with 2 running (eg tilt forward and to the side), there was not alot of thrust to tilt the 4kg test rig.

regards
Brenton
Hi Brenton,

I believe we spoke on the phone yesterday about a 120mm fan on the Harrier.

I think my test rig is going to be pretty light and I have estimated (guestimated) the reaction control tubes to be between 12 and 17mm dia max. I think if the wings are light on the test rig then I'll need a max of 80-100 grams of thrust to rock it about.

I'll call you after June 1 to discuss the 120mm fan.


best

Matt
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Old May 23, 2006, 03:28 AM
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Does anyone have any thoughts on a neat rotating vector nozzle system?
It has to be clean so as to minimise drag (obviously) and also to prevent dirt from fouling any close tolerance stuff.

Any drawings or clear descriptions would help.

A rotating "tube-in-tube" is looking like a good bet at the moment.

Matt
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Old May 23, 2006, 03:54 AM
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The rails on the underside together with the doors stops the free airflow to the sides
making something like at hoover craft situation.. low airspeed , higher pressure. with the four jetstreams downwards there will be a cirkulation of the air next to the jetstreams, leaving and airbag under the fuselage with much smaller airspeed / higher pressure.
I think this is the way i happens....
Klaus Scharnhorst might correct me if I am wrong.

Claus
Old May 23, 2006, 08:42 AM
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I saw something years ago (about 1985 I think) about this. Someone had made a scale ICDF Harrier, complete with reaction controls and everything. After a huge amount of experimenting he ended up using a large single fan and ducting exactly as per fullsize. The reaction jets were the bucket type and were fed from the fan, also like the fullsize. He eventually got it all to work perfectly in both hover and normal flight modes. But I never got to read the article about the in-flight transition.

As for the EDF bit, I don't know what thrust/weight a large fan and battery can produce compared to a similar sized ICDF and fuel etc. But a true (and scale) DF Harrier is definately possible!

All the best with it!

Martin
Old Jun 04, 2006, 09:28 PM
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I have now created an inlet and exaust ducting to suit a Wemotec Midi Fan and initial tests look good.

I am producing about 1.9kg of thrust and the weight of the ducting, fan unit, batteries & esc is 1.4kg. This leaves me with 500g to play with on the bedstead test rig.... When I get around to creating it.

Edit: Note that the system is far from optimised. The engine could be better, the ducting could be clean (and symetric), I could use nozzle guide vanes and the list goes on. I hope to get another 5-15% out of the inlet/exaust duct system with changes to the above.

I also plan to loose some of that too in the reaction control outlets. 1 for yaw, 2 for roll and 2 for pitch.
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Last edited by Psionic001; Jun 04, 2006 at 09:34 PM.


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