EDF Harrier VTOL & Reaction Control

[Psionic001]

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?

[Psionic001]

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.

[kriptonic]

I wish you luck.

gene

[punkindrublik]

Yes, interesting. I'll be watching....

[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.

[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

[Psionic001]

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.

[Psionic001]

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.

[speleopower]

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

[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

[Psionic001]

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

[Psionic001]

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

[clausxpf]

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

[MeGrimm]

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

[Psionic001]

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.

[denverone]

Anyone have a good 3-view with cross sections of the harrier. I have been looking and just cant seem to find them.

[Psionic001]

Anyone have a good 3-view with cross sections of the harrier. I have been looking and just cant seem to find them.

Amongst my harrier books I have a handfull.

I'll scan and upload in the next few days if you like.

There are no cross sections. One I have is a 5 view with the TAV-8B (Trainer) side view.

I've also seen some 3df models on the net which may help.

[denverone]

Any drawing would be a help thanks

[mrdj]

psionic, could you please send a picture. I have been playing with a smaller version, that may evolve into someting. Its not pretty, it was more of a "i wonder if this will work". The eventual plan is two units in tandem, two nozzles each.

My simple version uses a GWS fan, with a combination of paper tubes.

My performance measuring system is also simpler:I hold the fan a given distance off of the scale, and run it up.


Fan only - 4oz
Vectored fan - 1 oz (per nozzle)

system weight thus far - 8 1/8 oz

vectoring thrust with a toilet paper tube - priceless

There are two pictures of the current configuration, the extra nozzle was a even simpler attempt. I got about 40% with the one angle, 50 % with two.

[kriptonic]

Here is a shot of my Ducting on my Midi sized Harrier, and some 3 views...

Gene

[Psionic001]

psionic, could you please send a picture. I have been playing with a smaller version, that may evolve into someting. Its not pretty, it was more of a "i wonder if this will work". The eventual plan is two units in tandem, two nozzles each.


I havn't taken any decent pictures of mine yet, just some from a mobile phone camera. The one's here have the battery and accessories strapped to the back to aid in measuring total thrust and weight. Balanced on a small tin. Pretty crude.... yes.

I made my duct a little more advanced than your TPR version but mine too is pretty rough.

I used plasticine to create the shape of the ducts then epoxy/fiberglassed it and put some carbon uni in to keep it rigid. After the epoxy cured, I melted out the plasticine in the oven.

I see the main difference between you TPR version and mine, and it's an important one, is that mine is based on a volume flow system and not a pressure system.

The harrier scale nozzles can move air around 90 degree bends because of the huge pressures involved. I have adjusted mine so that I have smooth corners and no large convergence/divergence in the ducting, both of which will loose you thrust..... I think :).

[Psionic001]

Here is a shot of my Ducting on my Midi sized Harrier, and some 3 views...

Gene

That's a shot of the Harriers belly! ;)

Can we see inside please? :confused:

[kriptonic]

Sure, check out my build thread at the following link.

http://www.rcgroups.com/forums/showthread.php?t=271994

Gene

[mrdj]

You are quite a ways ahead of me. I'm still in proof of concept stage. Its a very impressive set up.

I like the plastiscine/fiberglass idea, it looks to have created a very workable design. This may be what I have to do for a more final package.

My nozzles are rough inside and out. There are also no vanes inside. Lots of room for improvement. I can also smooth the airflow inside the main tube with a slitter ramp. You are right about losing thrust in bends. When I added another cut to the curve, I increased effect, as well as having a greater bend in the airflow.

I didn't design this to increase pressure. The combined area of the two nozzles is about the same as the intake. Nothing too prescise, based on available materials. The two TPR diameters fit into the big Estes tube, with some squeezing and a little room left over.

Please keep us informed on progress.You really have something there!

[Psionic001]

You are quite a ways ahead of me. I'm still in proof of concept stage. Its a very impressive set up.

I like the plastiscine/fiberglass idea, it looks to have created a very workable design. This may be what I have to do for a more final package.

My nozzles are rough inside and out. There are also no vanes inside. Lots of room for improvement. I can also smooth the airflow inside the main tube with a slitter ramp. You are right about losing thrust in bends. When I added another cut to the curve, I increased effect, as well as having a greater bend in the airflow.

I didn't design this to increase pressure. The combined area of the two nozzles is about the same as the intake. Nothing too prescise, based on available materials. The two TPR diameters fit into the big Estes tube, with some squeezing and a little room left over.

Please keep us informed on progress.You really have something there!


The funny thing I forgot to tell you was that when I was carving the plasticine, I had to find something that was tubular to guide the shape of the outlet nozzles. I squeezed some plasticine into the end of a toilet paper roll to get the desired diameter and shape...

TPR-AV-8B? :D

[Psionic001]

Sure, check out my build thread at the following link.

http://www.rcgroups.com/forums/showthread.php?t=271994

Gene

Cool, I have some questions on technique...

How did you make the outlet ducts? Looks like glass on clay?
After carving the wood? How did you make that clear plastic ducting bottle shaped thing?
Edit: Don't make me read the whole build thread. It's waaay too long... :)

[Bobber Bob]

Hi Folks...

Try this Russian site for most of your needs... 3-View, that is.

I believe you will find at least one drawing with some "cuts" here...

http://www.airwar.ru/other/draw/harrieratl.html

I have used their stuff for most of my projects, including "my Harrier"...

Bob

Bob Reynolds
. ComeUpHere

[kriptonic]

Keep reading the thread.

Gene

[Psionic001]

Well I've installed some reaction control ducting and given the system a test run on a hanging test rig. even with the 4 tubes of 13.5mm ID (a 5th tube is still to be added) I have ample thrust to lift the rig and a whole lot more ballast... like a fuselage and wings :)

Impressions:
This thing is a highly unstable beast. It's like balancing a marble on a beach ball with a hair dryer.

After seeing the instability, I cut the 4 exaust outlets shorter and at an angle to vector the thrust in an outwards direction. This helped a little.

The reaction controll jets are not as effective as I thought they would be but I have not optimised the exit duct yet and hope to get a 30% performance increase by increasing the outlet size marginally and smoothing the flow.

A gyro helped marginally but I can see it being more effective with greater amounts of reaction thrust.

Even though all 4 reaction ducts exit the main ducting in the rear section I'm getting an excess of rear thrust so I'll be doing some modifications to fix this. probably even build a new duct.

When first spooled up, the rig wanted to roll left quickly. We thought this was torque roll untill we discovered that the outlet ducts (mine were hand made by visual only) had to have exactly the same outlet size to a very fine degree. the slightest adjustments of a milimeter here and there reduced this issue quickly.

We also noted that when the rig rolled more than 30 degrees all was lost and it became irrecoverable. This is because the anhedral contributed to an inward reaction control jet stream when the rig was level and any further roll only reduces the vertical component of reaction thrust on the wing that needs to be lifted.

At this point, I'd like to ask for any suggestions anyone might have to aid in stability.

Edit: Images and video from Mobile phone to follow.
Edit 2: I reckon this thing's only going to have enough battery to hover for 2-3 minutes max.

[Psionic001]

Images from 2nd test run. You can see rig with short and long outlet nozzles, rollowed by blurry images of the reaction control outlet in open, mid and closed positions.
At this stage the roll reaction valves only thrust down. They might also need to thrust up at some stage too.

[Psionic001]

Stop the swinging. This video illustrates the slow effect of stopping a deliberately induced swing on the test rig.

I must emphasize that this is NOT a hover but we were running at about 1/4 throttle.

[turbonut]

Man that is some nice work!..I hope it will be lite enuff when installed in a airframe..I am fallowing your work!
Scott

[Psionic001]

Man that is some nice work!..I hope it will be lite enuff when installed in a airframe..I am fallowing your work!
Scott

Thanks,

I'm sure it will be light enough to carry a basic EPP fuse or similar.
I'm also banking on battery and engine tech to improve a bit over the coming months to give me a little bit more endurance.

If this fails I'll have to step up to a 120mm fan which I hear can give up to 8.6kg (19lb). :D
Edit: See the Schübeler DS94 here http://www.shredair.com/fan.html

Matt

[miljnor]

don't know how much this helps. but...

I used to know a harrier mechanic and I remember him saying that the harrier has air ducting passages going everywhere. IE they have some ducting going to the tips of the wings and the tips of the elevators and nose ect..

Don't know if you could do any of this but it might help.

[MeGrimm]

Impressions:
"This thing is a highly unstable beast. It's like balancing a marble on a beach ball with a hair dryer."

"We also noted that when the rig rolled more than 30 degrees all was lost and it became irrecoverable."


Sounds just like my heli... :rolleyes:

[meles meles]

Oh indeedy, 'oomans. Harriers do have wing tip reaction jets ...

[miljnor]

Oh indeedy, 'oomans. Harriers do have wing tip reaction jets ...

are they jets or just a pressure blead from the main fan unit?

[Psionic001]

are they jets or just a pressure blead from the main fan unit?


Bleed from the main turbofan. Cold air I think.

[wildtech]

HI

I better keep a look out on this thread - a lot has happened since last here

Reactor control air is High Pressure air from the air compressor which is hot.

regards
Brenton

[wildtech]

Hi

One for Denverone

GR7 5 view in BMP, I have a DXF file I am updating to allow for easy scaling - I still haven't decided on what scale to build one at yet.

regards
Brenton

[denverone]

Thanks to everyone who keeps finding drawing and cross sections. This has been a real help as for some reason I could never find a good drawing.

[turbonut]

negitive on the hot air! the reaction control is after the compressor but pre combustion chamber...yes it is hoter then ambiant air due to compressing it but not heated buy fire!
Scott

[Psionic001]

negitive on the hot air! the reaction control is after the compressor but pre combustion chamber...yes it is hoter then ambiant air due to compressing it but not heated buy fire!
Scott

Thought so, otherwise those wing tips might be gettin a little hot. :censored:

[St. Martin]

Hi Matt, Sorry I did not answer on the other thread. Matt, all I have learned on ducted fans(and that goes back to the early 80's), is mass flow. To accomplsh what your dream is, nothing short of "very hard". Please don't mis-interpret my statements.

To compare an internal combustion jet with our "archaic" edf's is fruitless. I have often believed, that a person, with high composite constuction techniquics, could pull a Harrier type, in full function. This would involve construction of internal ducting that would be flexable and sealed. Also, I think a fan unit that could allow conversion of large diameter FSA into a extremly high efflux at the variable outlets.

I wonder, tho, how the rotor blades would accept this pressure behind the rotor, without stalling? Put your hand over the exaust of a standard ducted fan. Very easy to stall the fan.

My thoughts were to make a lightweight composite structure, much larger than the norm. The outlets would need to be 50%, each, of the FSA. Or, 25%, of the FSA if 4 are needed. Thrust, not efflux speed, is your friend here. The ducting will be phenominal, in engineering.

The airfoil would have to be a high lift type. To start flying in forward mode, very early.
It's really to bad we cannot scale the air, to the planes we fly. If we could, it would be easier, more than to the point of unobtainable. Our aircraft would fly with prop rpm's in the 5,000 range, instead of +10,000.

I admire your efforts. The larger, in scale you go, the more your success will be noticed. Has somthing to do with Reynolds numbers..

Regards,

Steve

[Psionic001]

Hi Matt, Sorry I did not answer on the other thread. Matt, all I have learned on ducted fans(and that goes back to the early 80's), is mass flow. To accomplsh what your dream is, nothing short of "very hard". Please don't mis-interpret my statements.

To compare an internal combustion jet with our "archaic" edf's is fruitless. I have often believed, that a person, with high composite constuction techniquics, could pull a Harrier type, in full function. This would involve construction of internal ducting that would be flexable and sealed. Also, I think a fan unit that could allow conversion of large diameter FSA into a extremly high efflux at the variable outlets.

I wonder, tho, how the rotor blades would accept this pressure behind the rotor, without stalling? Put your hand over the exaust of a standard ducted fan. Very easy to stall the fan.

My thoughts were to make a lightweight composite structure, much larger than the norm. The outlets would need to be 50%, each, of the FSA. Or, 25%, of the FSA if 4 are needed. Thrust, not efflux speed, is your friend here. The ducting will be phenominal, in engineering.

The airfoil would have to be a high lift type. To start flying in forward mode, very early.
It's really to bad we cannot scale the air, to the planes we fly. If we could, it would be easier, more than to the point of unobtainable. Our aircraft would fly with prop rpm's in the 5,000 range, instead of +10,000.

I admire your efforts. The larger, in scale you go, the more your success will be noticed. Has somthing to do with Reynolds numbers..

Regards,

Steve

Thanks Steve,

I've had some success with the setup in terms of raw thrust. (I still have a further 500 grams to play with. Now I need to start on the stability challenge. If I waste too much thrust on stability issues, I'll go from the 90mm up to the 120mm which should help as you suggest.

Thanks again,

Matt

[Psionic001]

Can someone tell me what these two areas are, hilighted below:

Midi Fan
Materials: Nylon, ABS, Aluminium
Weight: about 105 g
Rotor: 6-bladed, glass filled nylon
Input power: 200-1000 W
Max. rpm: 35.000 rpm
Kit contents: complete, English instructions
Assembly time: about five minutes
Ageom: 49,4cm2
Aeff: 45,6 cm2
Static thrust: 7-22 N

[Bobber Bob]

Hi 001...

"Aeff", is probably the area of the eflux, and, hopefully is the "FSA", and that would leave the "Ageom", meaning the total fan's area (Geometry), including the motor...

My guess, but those that REALLY know will be "chimming in" shortly...

Bob

Bob Reynolds
. ComeUpHere

[mrdj]

How much thrust was lost by bleeding off the reaction jets?

[Psionic001]

How much thrust was lost by bleeding off the reaction jets?

I didn't measure how much thrust I lost, but it wasn't much. However I was hoping to loose a little more as the reaction outlets could have pushed a little harder. I'm guessing I felt 50grams of thrust per outlet.

This week, I'm optimising the internal design of those reaction outlets to see if I can squeeze some more out of them for free.

regards

Matt

[jumpy]

How are you controlling the airflow through the reaction outlets?
Great work by the way.
Phil.

[Psionic001]

How are you controlling the airflow through the reaction outlets?
Great work by the way.
Phil.

Hi, the last 3 images of post #30 show some blurry photos of the outlets.
It's just an outer tube blocking some holes in the inner tube.

The air is scavenged from various places inside the main duct.

Matt

[vampire67]

Hi, the last 3 images of post #30 show some blurry photos of the outlets.
It's just an outer tube blocking some holes in the inner tube.

Is there some internal guide vanes to improve flow guiding out of the nozzles


The air is scavenged from various places inside the main duct.

Your setup is the most advanced I've seen.

But it might still not being realy voluminatric.
As the only air guiding is done by the duct walls and the duct walls exceeding the deflection angle of the EDF rule books the flow might become turbulent at most of the deflection points.

What about internal (variable) guide vanes activated by servos?
This could help control as you may control thrust of the 4 main outlets reperately. It would possibly also increase the thrust ratio.
By the way they are also shown on the real pegasus engine.

This variable guide vanes may also be used to control bleed air for the reaction outlets. Instead of open/close the nozzles the vans can deflect air into or away from the reaction control outlets.
Another advantage is that the control servos could move into the fuselage.
That's moving the weight closer to the center.

May the thrust be with you ;D

kind regards Peter

[Psionic001]

Is there some internal guide vanes to improve flow guiding out of the nozzles


Your setup is the most advanced I've seen.

But it might still not being realy voluminatric.
As the only air guiding is done by the duct walls and the duct walls exceeding the deflection angle of the EDF rule books the flow might become turbulent at most of the deflection points.

What about internal (variable) guide vanes activated by servos?
This could help control as you may control thrust of the 4 main outlets reperately. It would possibly also increase the thrust ratio.
By the way they are also shown on the real pegasus engine.

This variable guide vanes may also be used to control bleed air for the reaction outlets. Instead of open/close the nozzles the vans can deflect air into or away from the reaction control outlets.
Another advantage is that the control servos could move into the fuselage.
That's moving the weight closer to the center.

May the thrust be with you ;D

kind regards Peter


Thanks Peter,

Good to hear more ideas...
The new version of the ducting (MK2) I started last night will be far more advanced than the first which was made by hand/eye. I have some new secret sauce to add which should improve the efficiency.

To the best of my knowledge, the guide vanes in the outlet ducts of the real Harrier do not move. I will be adding guide vanes to mine but they will be fixed.

"What about internal variable guide vanes?", Well I think that would be nice but too complex and heavy. I'd prefer to get the math right on this, and if necessary, keep evolving a standard duct template untill I have something that's rock solid.

On the Roll reaction tubes, where they are exiting the main duct, I'm actually taking advantage of the compression to get a touch more thrust.

There are no guide vanes for the nozzles but I'm toying with the idea. I'm trying to think of a clean way to do it on a 13.5mm diameter tube. The best way I have come up with so far would be to laser cut (or similar) a curve through the whole tube side then slide a curved form (made of thin stainless or carbon) through to the other side.

MK2 also more closely follows the "area rule" to the best of my ability.
http://en.wikipedia.org/wiki/Whitcomb_area_rule

If all goes well, I'll be testing MK2 late next week as I've had no build time lateley. MK1 is in the meaphorical bin!

best

Matt

[vampire67]

Thanks Peter,
To the best of my knowledge, the guide vanes in the outlet ducts of the real Harrier do not move. I will be adding guide vanes to mine but they will be fixed.

Yes obviously they are, and also just in the outlets.
Here I would suggest just to copy this and put one or two fixed guide vanes into each nozzle were the flow is deflected 90°.


"What about internal variable guide vanes?", Well I think that would be nice but too complex and heavy. I'd prefer to get the math right on this, and if necessary, keep evolving a standard duct template untill I have something that's rock solid.

May be not Vanes but just one or two.
Think about a simple vane in the middle that can balance the flow of the left and right side. Think about a simple inverted rudder like vane in front of a separator in the middle of the flow channel just behind the EDF.
I believe a simple vane of 1/4" tied to the control servos should be more than sufficiant to improve roll control. Two more similar vanes to adjust flow between each front and back nozzle and you get added pitch control.

Another benefit is that this would be helpfull for adjusting statical balance. You indicated a high sensitivity to manufacturing tolerances.
The vanes will allow compensating tolerances.

The variable vanes have an high benefit to seperate EDFs that I have seen in another VTOL thread here. They react quickly compared to power control of seperate EDFs.

The only problem are the forces on an inverted rudder like vane direct in the flow. Maybe a balanced construction is better, but a bit less effective.


There are no guide vanes for the nozzles but I'm toying with the idea. I'm trying to think of a clean way to do it on a 13.5mm diameter tube. The best way I have come up with so far would be to laser cut (or similar) a curve through the whole tube side then slide a curved form (made of thin stainless or carbon) through to the other side.

No need for carbon.
Have you thought about thin plastic, like yoghurt cups or may be aluminium from coke cans. You can take the bended part direct from the sides.
It's thin, leightweight and cheap.

regards Peter

[Psionic001]

Another benefit is that this would be helpfull for adjusting statical balance. You indicated a high sensitivity to manufacturing tolerances.
The vanes will allow compensating tolerances.

The variable vanes have an high benefit to seperate EDFs that I have seen in another VTOL thread here. They react quickly compared to power control of seperate EDFs.

The only problem are the forces on an inverted rudder like vane direct in the flow. Maybe a balanced construction is better, but a bit less effective.


No need for carbon.
Have you thought about thin plastic, like yoghurt cups or may be aluminium from coke cans. You can take the bended part direct from the sides.
It's thin, leightweight and cheap.

regards Peter

Peter,

I think you are correct that internal vanes will have a big effect (though not scale) in getting this project off the ground sooner...pardon the pun... A balanced vane might work like a carburettor choke, rotating from the centre.

The coke can idea will work well too as the flow forces probably won't even be enough to vibrate & flex the aluminium. If I doubled it over with a bend I'll also have a sort of smooth leading edge too.

Thanks again for your input, it is really helpful,

regards

Matt

[mrdj]

There are no guide vanes for the nozzles but I'm toying with the idea. I'm trying to think of a clean way to do it on a 13.5mm diameter tube. The best way I have come up with so far would be to laser cut (or similar) a curve through the whole tube side then slide a curved form (made of thin stainless or carbon) through to the other side.

How about putting the vanes in the plasticine form? The cured expoxy from the nozzle could hold them in place, and the plasticine holding them initially would melt away. It would also keep th nozzle clean and strong (and light)

djm

[rotccapt]

this sounds cool

[MeGrimm]

I didn't measure how much thrust I lost, but it wasn't much. However I was hoping to loose a little more as the reaction outlets could have pushed a little harder. I'm guessing I felt 50grams of thrust per outlet.

This week, I'm optimising the internal design of those reaction outlets to see if I can squeeze some more out of them for free.

regards

Matt

Would the wingtip jets give more thrust if they finished in a little downward facing nozzle, or 'thrust pipe', rather than just a hole in the wall of the tube? The extra tube could be simply added onto the bottom of the existing hole and slide back and forth like it does already.

[miljnor]

I would think you would want the outlet for the wingtip jets to be in a curve (were the highest pressur is) for them to get maximum air flow ect..

[Psionic001]

How about putting the vanes in the plasticine form? The cured expoxy from the nozzle could hold them in place, and the plasticine holding them initially would melt away. It would also keep th nozzle clean and strong (and light)

djm
Would the wingtip jets give more thrust if they finished in a little downward facing nozzle, or 'thrust pipe', rather than just a hole in the wall of the tube? The extra tube could be simply added onto the bottom of the existing hole and slide back and forth like it does already.

I would think you would want the outlet for the wingtip jets to be in a curve (were the highest pressur is) for them to get maximum air flow ect..

Yes... currently at the end of each nozzle (wings, nose, tail pitch) I have stuffed a little lump of plasticine and rounded it with a ball shaped instrument so it has a smooth outward flow. I have not bench tested the difference between this and the old set-up which was just a hole near the end of a blocked off tube.

On the wing tips, the reaction thrust departs at an outward angle and not at 90°. This helps as it negates the anhedral which is already inherant in the wing, giving me a more vertical component of reaction thrust. Hope that makes sense.

Of note, the reaction thrust is so far aft that I can't help thinking that it must be contributing to a nose down moment, therefore I need even more compensation from the pitch valves. Hmmmmmm!

[QUANTUMPHYSICS]

I personally don't think the HARRIER can be built as an EDF model for a number of reasons -at least, not with fully funtional verticl to forward flight and VTOL.

#1 No electric fan will give you enough thrust to lift the airframe and its components as well as the engine. You need to produce a thrust to weight of 1.25 to get this model to work like the big boyz. No singular EDF will give that.

#2 The harrier's flight balancing is entirely based on the 4 nozzles. The wingtip puffers are for balancing mainly and an EDF won't produce enough air output for them to even be considered. A single EDF won't give you enough thrust to push an equal mass of air through all 4 nozzles. You might try making the front nozzles smaller than the rear nozzles.

#3 Your airframe needs to be EXTREMELY light. I think Balsa is too heavy for what your doing.

A gas powered model will produce far more power and thrust than the EDF (obviously). I think you should consider gas power instead.

Right now I am building two models.

One is a F-35 JSF with full VTOL capability (a EDF lifting fan and a main gas powered fan for forward thrust).
I am also building an SA-43 HAMMERHEAD (from Space above and Beyond).

So far, My F-35 hover's perfectly 7 feet off the ground but, I'm not finished with the battery design and lighting LED's I am working on finishing it. Should take me a month.

[vampire67]

I personally don't think the HARRIER can be built as an EDF model for a number of reasons -at least, not with fully funtional verticl to forward flight and VTOL.

. . . same as earth must be flat and sonic barrier can not be broken . . .
:D
Sorry, I couldn't resist.


#1 No electric fan will give you enough thrust to lift the airframe and its components as well as the engine. You need to produce a thrust to weight of 1.25 to get this model to work like the big boyz. No singular EDF will give that.

I have some news for you. There are EDF jets out there in the 1.3:1 ratio.
Not only that but they have quite some durability due to advanced batteries.

Were you are right is that this will be very difficult accieved. These EDF use almost optimal ducting, while the Harrier in hover mode may have some ducting losses of 20..50%.
It's easy to get highter thrust ratio with of the shelf parts. Problems are the batteries. LiPos are made for durability, so even high power EDF have 5..6min flight time, so the average load is 10C.
For hover we need some turbo mode were LiPos might be loaded with more than 20C. Together with the zero (external) airflow in hover mode LiPos may get toasted.

However there was already a STOL Harrier from Dirk Juras 10 jears ago. That was pre LiPo and Pre-Schubeler and flow with 4 jurassic Rojets and NiCd.
The technilogy has meanwhile arrived and it just takes a pioneer to put it together.


#2 The harrier's flight balancing is entirely based on the 4 nozzles. The wingtip puffers are for balancing mainly and an EDF won't produce enough air output for them to even be considered. A single EDF won't give you enough thrust to push an equal mass of air through all 4 nozzles. You might try making the front nozzles smaller than the rear nozzles.

That's why I proposed variable vanes in the duct.
And Psionic001 already measured about 50g thrust from the wingtip buffers.
So the numbers are there, just read it.


#3 Your airframe needs to be EXTREMELY light. I think Balsa is too heavy for what your doing.

Wood is one of of most advanced materials. Nature has spent millions of years development time. Trust me, it's not easy to surpass ;)
Ok, an ocational CFK reinforcement helps.


A gas powered model will produce far more power and thrust than the EDF (obviously). I think you should consider gas power instead.

Right now I am building two models.

One is a F-35 JSF with full VTOL capability (a EDF lifting fan and a main gas powered fan for forward thrust).
I am also building an SA-43 HAMMERHEAD (from Space above and Beyond).

So far, My F-35 hover's perfectly 7 feet off the ground but, I'm not finished with the battery design and lighting LED's I am working on finishing it. Should take me a month.
. . . at least someone with background . . .

Nobody says it's easy.
And it's common sense that gas powered is easier.
Gas powered have been done, so they lost the novelty and we all want to "boldly go, were no one has gone before".

But you may help with some numerics.
Like Turbine thrust in flight configuration and hover mode and thrust of hover fan. This might help Psionic001 to estimate the power requirements more correct.
I would assume that your hover fan at least contributes about 30..40% total thrust in hover mode. Otherwise balance would be nightmare with the rear nozzle of the F35 being in the far rear end of the fuselage.
Taking the added weigt of turbine and fuel it seems to be also not an optimal setup, but the EDF hover fan was easier than powering it from the turbine like the real one.

Have you thought about putting a electical generator on the turbine shaft (how about the starter motor in a JetCat in generator mode) and powering the EDF from the turbine too. Could bet a weight benefit to get the EDF batteries out.

kind regards Peter

[Psionic001]

I say that if my project dosn't work then I'lll just wait the 6 months for batteries to catch up AND/OR just step up to the 120mm fan.

Anyway, somebodys gotta do it oneday.... Why not me :)

I have put together some new duct plans and totally redesigned the ducting based on some new ideas and some ideas provided here in this thread.

Will let you all know next week.


best

Matt

[eatond]

So far, My F-35 hover's perfectly 7 feet off the ground but, I'm not finished with the battery design and lighting LED's I am working on finishing it. Should take me a month.

Hi QUANTUMPHYSICS,
got any pictures of your F-35. Love to see it. Also I'm curious about your design decision about using an EDF for hover and a GDF for forward flight. I'd have thought it would have played to their individual strengths the other way around.

Dan Eaton

[QUANTUMPHYSICS]

VAMPIRE -
a very decent, well thought out reply. I didn't not mean to sound arrogant


PSIONIC -
Yes, I think you will need better batteries. My Sa-43 Hammerhead is using regular
LI-ION batteries since it only has to fly like a typical airplane. Most of the parts I'm using are from F-14 kits since it is a twin engine design.
Since the HAMMERHEAD has a canard front wing design, it naturaly flies fast because it down pitches (to compensate for the tail wing stall).
When I am fully done, I think I should be able to push it harder than 200 MPH.
It was as easy to build as a F-16 would be from scratch.


My F-35c has custom LI-POLYMER batteries cells that I ordered from
GOLDEN YIP - Chinese hobby shop.
I am using 2 x GWS engines. (EDF3045x4 & Em300H) - one is the main lift fan. The second is for the main engine. I removed the standard blades and added a lighter fan with more blades. We dropped the glowfueled engine for weight saving. Using them instead in the SA-43.
I get about 250front/300rear g of thrust (on 12.5 Volts). The only problem is that the motors burn out after about 10 test flights.
I am using FUTABA 4.5g micro servos which weight about 17 grams total.
Tsunami10 ultralight speed controllers.
A Futaba 9ZAS/WC2 radio - for all three of my models and my Aerotech Shkyhawk.
I am also using a heavily customized control board from my old DRAGONFLY 4 electric helictoper. The control board/ speed ships and servos measure about 90 grams.
So far my thrust to weight ratio is about 1.65 but it will drop with addons.
Mostly foam, no balsa...no metal. Plastic tube landing gear, plastic pushrods.
The battery and airframe are the heaviest parts but since the engines give so much thrust its not a big problem.

My secret to making it hover and transition are speed controllers - as well as weight control. I have designed a lobster nozzle just like the real thing out of thin plastic. When I use the servo, the lobster tail points downwards which allows the ducted rear engine to make up for the thrust the main lift fan IS NOT PRODUCING (since it isn't ducted). Because of this, the plane pitches downwards a little - but the hover is perfect when you use the forward speed control.

I wasn't going so much for durability as I am for lightweightedness so I can get indoor use. It I could get a material lighter than foam and sturdy like plastic, I could make this thing a best selling toy.

BEcause this model has 2 engines, I dont have the same weight balancing issues you do with the harrier. After experimenting, I can see that The US Government was smart for picking the F-35 because it is naturaly more stable. I read the F-35's engine is the most powerful jet engine in the world - surpassing the Harrier's.
My design is not complete yet because I'm trying to add lighting, landing gear retracts and I have to paint it& decal.

I was kinda thinking about adding the dorsal MAIN LIFT FAN COVER DOORS and making them motorized but I don't think I can because of the weight.

EATON-
so far I have a video clip on 8mm. I'll try and get some pics as soon as possible.

[QUANTUMPHYSICS]

I am thinking of designing a SA-43 HAMMERHEAD with two Pegasus HP ducted fan engines. IT would be about 6 feet long.
The Pegasus HP weighs 5pounds and produces over 35 lb of thrust.

[QUANTUMPHYSICS]

PSIONIC,

I must say, your engine design as in post (Jun 09, 2006, 10:05 AM ) is absolutely brilliant.

[vampire67]

My F-35c has custom LI-POLYMER batteries cells that I ordered from
GOLDEN YIP - Chinese hobby shop.
I am using 2 x GWS engines. (EDF3045x4 & Em300H) - one is the main lift fan. The second is for the main engine. I removed the standard blades and added a lighter fan with more blades. We dropped the glowfueled engine for weight saving. Using them instead in the SA-43.
I get about 250front/300rear g of thrust (on 12.5 Volts). The only problem is that the motors burn out after about 10 test flights.

Now you surprised me.

If I understand you right, you have a parkflyer size F35 now fully hovering with EDF.
It sounded like you did it with a turbine. Now it dawned me that you ment ICDF instead.
From all what I know ICDF are easy to surpass with EDF. Only real turbines are a real competition. Only real benefit of ICDF is faster "recharging".

There was an EDF VTOL thread (thread (http://www.rcgroups.com/forums/showthread.php?t=460061) ) mentioning control instability caused by slow EDF spool up times.
How did your F35 stabilise ?

[COLOR=Green]
When I am fully done, I think I should be able to push it harder than 200 MPH.
It was as easy to build as a F-16 would be from scratch.
Don't want to disapoint you but if this are ducted fans (wether EDF or ICDF) I don't belive you you will cross 200MPH (120m/s :eek: ).
Ducted fans have an automatic speed limit because of the (relative low) exhaust speed.
Nomatter how much static thrust you have, kv and voltage define the maximum rpm of the fan and therefore the speed.
Vector and Blade II EDFs are scratching this border, but they need state of the art in aerodynamics.
The hammerhead has a interesting apearance but good aerodynamics seems to be missing.
Speed range >200MPH are turbine only. Based on the exhaust speed of turbines you can accelerate until your air frame disintegrates.
With (current) EDF you can't cross this line.

kind regards Peter

[speleopower]

QUANTUMPHYSICS-I'm sure we have some members in or near New York who could swing by your club field to photograph and video your F-35 hover machine fly. Which club are you affiliated with?

Any takers.

If you have video on 8mm video than I can easily digitize it then convert it to just about any file type you like. It's pretty easy to convert 8mm to .mpeg or .avi with the right gear. If you don't have capibility to photo and video your machine I'm sure you can contact one of the major RC magazines and they'll send a field reporter to your club field. They will probably do a feature story on your machine or at least publish a picture or 2.



Scott

[QUANTUMPHYSICS]

VAMPIRE -

Your absolutely right about the F-35 - it's ultralight. I wouldn't call it a park flyer but, if you think that's an appropriate name, OK.
I am building the HAMMERHEAD with help from a friend who is heavy into HElicopters. To be perfectly honest, I'm relatively new to scale R/C. I just bought parts he suggested and came up with suggestions.
I've tested a much smaller hammerhead model made out of regular aircraft parts. And it buzzed around pretty well.
I want to build a SCALE Hammerhead thats about 6 Feet long and power it with two glofuel jet turbines.
Forgive me if some of my posts are innacurate because Im not the expert on R/c. mY HELP IS.

i SHOULD HAVE SAID

When I am fully done WITH THE LARGER SCALE MODEL, I think I should be able to push it harder than 200 MPH.

The true Hammerhead is supposed to use Scramjet engines. Since that is an impossibility at this scale, I am trying to figure out what the best glofuel jet engines would be for this model.

[QUANTUMPHYSICS]

speleopower

When I started on the F35c I was going for a TOY that could be used indoors. So far, I've been happy with the outcome but now I want to make it larger and more functional. I'm thinking, retractable landing gear, flashing nav lights, the works.
Right now I've got what is more like a cheap glider that can take off vertically hover and then thrust forward.
I' am happy with the fact that it flies relatively slowly. Its easier to control that way.
It burns power very quickly. A cool feature is that it can land almost vertically around 3 feet from the ground - if you pitch up and decrease the speed controls simultaneously. When its close to the ground its almost like a hovercraft riding an air cushion.

When I'm proud of what I built Ill send some pictures to one of those model airplane magazines.

[m2energysolution]

Hi,
I don't mean to interrupt. I can across this and thought I would share! :cool:

http://www.airpacmodels.com/skymasterfiles/AV-8B.wmv

Dave

[QUANTUMPHYSICS]

m2energysolution

I saw the video. Looks very good so far. I could be wrong but to me it didn't look like a ducted Fan jet with the 4 Harrier jet nozzles - just the roll control.

It appears to me that this guy did what I did to a degree with my F35.
Put a powerful motor facing downwards and add vectoring nozzles to stop the roll.

To tell the truth, I should have built mine with glofuel power instead cause he gets far more time out of his contraption than me.

I think if this guy fashions a harrier body around what he has, even without full thrust forward flight, he's got a great toy.

[winmodels]

Can someone tell me what these two areas are, hilighted below:
Ageom: 49,4cm2
Aeff: 45,6 cm2
Static thrust: 7-22 N

Hi 001

I'm surprised that nobody has answered your question. As far as I can remember it is (was) actually explained in WEMOTEC's brochure.

Ageom means geometric area (of the exhaust) calculated from the diameter.
Aeff means effective area (of the exhaust), which can be construed to be smaller than the geometrical one on account of the BL influence. If you use Aeff for the efficiency calculations of an EDF instead of Ageom it calculates a better efficiency. This may be all very true, but the definition of the Aeff is not easy and bound to create some controversy. In the end it is actually the exit diameter in the model which should be used for these calculations, but there it becomes even more complicated.

Have fun with fans

Klaus

[Psionic001]

Hi 001

I'm surprised that nobody has answered your question. As far as I can remember it is (was) actually explained in WEMOTEC's brochure.

Ageom means geometric area (of the exhaust) calculated from the diameter.
Aeff means effective area (of the exhaust), which can be construed to be smaller than the geometrical one on account of the BL influence. If you use Aeff for the efficiency calculations of an EDF instead of Ageom it calculates a better efficiency. This may be all very true, but the definition of the Aeff is not easy and bound to create some controversy. In the end it is actually the exit diameter in the model which should be used for these calculations, but there it becomes even more complicated.

Have fun with fans

Klaus

Thanks Klaus,

that does clear things up a little better. Since I didn't have a clear answer, I did use the AEFF with my calculations and, combined with some principles from the area rule, I think I might be on a path to a better MK2 design. Remember my first one was hand carved from plasticine and was a pure guess.

Considering the numbers: Aeff: 45,6 cm2.
I have calculated that if I need 5 reaction outlets, each of 13.5mm dia, then each of the remaining main nozzles need to be about 36mm dia, give or take a millimeter. I have rounded down in all my calcs to take into account bends in the ducting, but I certainly don't have the skills to figure out duct losses in my design. :(

best

Matt

[QUANTUMPHYSICS]

may I ask you PSIONIC
what is the model EDF you are using -
how much does the EDF weight -
How much thrust does it produce with optimal intake ports -
How much does your battery weight-
How many volts/ amps is your battery supplying.

[Psionic001]

may I ask you PSIONIC
what is the model EDF you are using -
how much does the EDF weight -
How much thrust does it produce with optimal intake ports -
How much does your battery weight-
How many volts/ amps is your battery supplying.

Hey QUANTUMPHYSICS,

Off the top of my head, because I didn't write down the specs:
EDF is a Wemotec Midi 90mm size.
Hacker motor B50 13XL I think. I believe this is not optimum.
http://www.hackerbrushless.com/motors_b50.shtml Maybe the 11XL would be bettter.
I'm using 120% intake which I'll convert back to 100% based on feedback here.
Thrust on the MK1 design was 1.9kg total from 4 mains with reaction tubes blocked. That's unoptimised thrust. I believe I can push 2-2.2kg at best.
Battery + motor + fan + ESC + ducting = 1.4kg
Batteries in series 22.2V ....
2 Kokam LiPolys 11.1v/3200mah/20c batteries
We uses a clamp meter to measure amps during our runs and did not exceed 60-64amp bursts to protect our gear.


POWER HELP:
This is my first foray into EDF and eletric as a whole, and really, I don't know a whole lot about it. If someone can recommend an alternate setup that would reduce the weight or optimise the endurance of the system I would be greatful.

Thanks

Matt

[vampire67]

Hey QUANTUMPHYSICS,
I'm using 120% intake which I'll convert back to 100% based on feedback here.

I would wait for some feedback from Klaus on that.
The 100% is for horizontal flight mode.
As as are looking for optimal setup for hover mode the facts could be different.

If I read the EDF books right the 100% rule seems to apply for protecting the fan from overpresure during flight.
I doubt that the Harrier will be fast. To much drag from the big fuselage.

If you look at the real Harrier it has several cheater holes placed around the intake.
The F35 has also a cheater hole on the top, right behind the lift fan for added air intake area.
If the real thing needs this (with turbines) we may also need this.
So I would experiment with different intake sections but would guess that we need 110%..120% rather than just 100%.

kind regards Peter

[Psionic001]

I would wait for some feedback from Klaus on that.
The 100% is for horizontal flight mode.
As as are looking for optimal setup for hover mode the facts could be different.

If I read the EDF books right the 100% rule seems to apply for protecting the fan from overpresure during flight.
I doubt that the Harrier will be fast. To much drag from the big fuselage.

If you look at the real Harrier it has several cheater holes placed around the intake.
The F35 has also a cheater hole on the top, right behind the lift fan for added air intake area.
If the real thing needs this (with turbines) we may also need this.
So I would experiment with different intake sections but would guess that we need 110%..120% rather than just 100%.

kind regards Peter

Great minds...

So my next question was...
Do you think I'd go to 105% or something like that to account for duct losses in horizontal flight? i.e. 5% makes up for (balances?) any back pressure due to the losses.

I did intend to keep the inlet at 120% for hover attempts unless I'm missing something about the inertia of air... hmmmm :confused:

[QUANTUMPHYSICS]

Great minds...

So my next question was...
Do you think I'd go to 105% or something like that to account for duct losses in horizontal flight? i.e. 5% makes up for (balances?) any back pressure due to the losses.

I did intend to keep the inlet at 120% for hover attempts unless I'm missing something about the inertia of air... hmmmm :confused:




I was reading online and I came across this description of the HArrier VTOL:


Specifications (Harrier GR.1)
General characteristics
Crew: One
Length: 45 ft 7 in (13.90 m)
Wingspan: 25 ft 3 in (7.70 m)
Height: 11 ft 4 in (3.45 m)
Wing area: ft² (m²)
Empty weight: 12,190 lb (5,530 kg)
Loaded weight: 17,260 lb (7,830 kg)
Maximum Take-Off Weight: 25,350 lb (11,500 kg)
Powerplant: 1× Rolls-Royce Pegasus 101 turbofan with four swivelling nozzles and four 'puffer jets' in the nose, the wing tips, and one (steerable) on the tail, which are used to control the aircraft during vertical flight. The puffer jets use engine bleed air and provide up to 1,000 lbf (4 kN) of thrust., 19,000 lbf (84.5 kN)

The procedure for VTOL involves parking the aircraft facing into the wind. The aircraft is brought to a halt, throttle to idle, wheels locked. The thrust vector is set to 90 degrees and the throttle brought up to maximum. The aircraft leaves the ground rapidly. The throttle is trimmed until a hover state is achieved at the desired altitude. During the ascent and hover, the reaction control system is continuously adjusted to maintain position over the patch of ground, much as it is with a helicopter. The aircraft has to face into the wind when taking off in this way. A side wind causes the aircraft to pitch away from the lee side. This would alter the thrust vector away from vertical and cause the aicraft to slew sideways. This is hard to control and dangerous. In severe cases the aircraft can settle with power while moving to the side. While taking off in windy conditions is always more difficult when within ground effect, it is easier to maintain heading away from the ground effect as the tailplane tends to stabilise the heading into the wind. At hover, the thrust vector is slowly returned to horizontal while the altitude and angle of attack is maintained in a specified range. At or shortly after normal take off speed, the thrust vector is set to horizontal and thrust is usually trimmed back to control acceleration.

The HArrier is remarkable because its Engine is able to produce 19000 lbs of thrust even when the aircraft is loaded weighing 17,000 lbs.
Thrust to weight ratio being 1.11
I read that an aircraft must be able to produce a ratio of 1.15 in order to Hover. I believe that the Harrier is never fully loaded in order to increase the thrust to weight ratio.

In my opinion, to make a good harrier, the engine must have an intake area that perfectly matches the intake required for that specific model.
I don't think cheater holes are neccesary because these EDF's don't produce thrust on the scale as the harrier - I'm not sure if you noticed but those smaller intakes surrounding the Harrier's intake are Variable geometry, they don't remain open. I believe the pilot or the flight computer is able to vary the size of each port in order to achieve maximum power. There is no way we could accomplish that on this scale. I noticed that I didn't need to cut extra vents in my F-35.

[Eddy]

The cheater hole vents open as the engine needs them to, in forward flight, as the ram air increases they close due to the negative pressure on them,
They are free floating work on that very principle. In Hover the engine needs the extra air and they automatically open to let the air in.

[kriptonic]

The "Cheeter" holes in the Harrier are spring loaded shut, and open when the engine is causing a low enough pressure to overcome the spring tension durring full power/low airspeed hovering.

I built my Harrier with the intention to make it a VTOL once a 3.5kW power system is avaliable for the 90mm fan range, hence the balsa airframe and wings for future reation control system, my harrier AUW is 5.5 lbs on 2kW of power.

check out the build thread on it at the following link

http://www.rcgroups.com/forums/showthread.php?t=271994

Gene

[Psionic001]

The "Cheeter" holes in the Harrier are spring loaded shut, and open when the engine is causing a low enough pressure to overcome the spring tension durring full power/low airspeed hovering.

I built my Harrier with the intention to make it a VTOL once a 3.5kW power system is avaliable for the 90mm fan range, hence the balsa airframe and wings for future reation control system, my harrier AUW is 5.5 lbs on 2kW of power.

check out the build thread on it at the following link

http://www.rcgroups.com/forums/showthread.php?t=271994

Gene

Indeed the "Cheater" holes are lightly sprung. I recently watched a Harrier DVD which included footage of a pilot doing a walk around. he poked at some of the holes and they lightly spring back.

Matty

[Eddy]

Actually they are not even spring loaded, there just on a pivot pin.
If you ever notice on a harrier that does not have the engine running the top vents are always open, they fall down to the open position due to gravity and the bottom one also fall down to the closed position, a person pushing them in from just below the widest point of the fuse down, would have them fall back due to gravity.
In a hover or in flight are the only times you will see them all open or all closed.

[Psionic001]

Actually they are not even spring loaded, there just on a pivot pin.
If you ever notice on a harrier that does not have the engine running the top vents are always open, they fall down to the open position due to gravity and the bottom one also fall down to the closed position, a person pushing them in from just below the widest point of the fuse would have them fall back due to gravity.
In a hover or in flight are the only times you will see them all open or all closed.

I agree, thinking about it now, the pilot could only reach the bottom half of the cheater holes which fell with gravity.

Attached is an illustrative photo.


matty

[kriptonic]

time to give back my friend his Marine issued AV8-A manual.

Gene

[Psionic001]

time to give back my friend his Marine issued AV8-A manual.

Gene

After scanning to PDF and posting here I hope??? :D

[QUANTUMPHYSICS]

After scanning to PDF and posting here I hope??? :D


Considering that the harrier when finished is not going to fly very fast, do you think Micro-Servos are a good idea?

I was thinking that if I built a harrier, I would only have Elevator and Rudder control servos to save on weight.

[MeGrimm]

I was thinking that if I built a harrier, I would only have Elevator and Rudder control servos to save on weight.

Surely the rudder is a luxury, but you'd need ailerons with so much anhedral, for forward flight at least?

[Eddy]

kriptonic
time to give back my friend his Marine issued AV8-A manual.

Gene

I hope I did not offend you, just commenting on how they cheater vents work, I have the corporate version of your manual and about 20 other books and 30 years research on this.
Do you have different info on the vents?

[QUANTUMPHYSICS]

I think this engine would be good to build a harrier with. HYPERFLOW 370EP
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLXA3&P=7

If you get a brushless motor as suggested, you can get 700g static thrust.
I think I might consider this.

[Psionic001]

Thought:
It's amazing how well a PET 1.25 litre soft drink bottle works as ducting for a wemotec. There's even a little built in lip.

[Psionic001]

Does anyone have this?
http://www.flight-manuals-on-cd.com/AV8.html

[speleopower]

Regarding post 77
"Off the top of my head, because I didn't write down the specs:
EDF is a Wemotec Midi 90mm size.
Hacker motor B50 13XL I think. I believe this is not optimum.
http://www.hackerbrushless.com/motors_b50.shtml Maybe the 11XL would be bettter."

The B50-13XL is a very good choice for the Midi fan.
See post #7 of the following thread. http://www.rcgroups.com/forums/showthread.php?t=473134#post4978323

There is a lot of fan/motor combos out there. It takes a couple evenings to find a lot of the info but it's here.

Scott

[vampire67]

I think this engine would be good to build a harrier with. HYPERFLOW 370EP
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLXA3&P=7

If you get a brushless motor as suggested, you can get 700g static thrust.
I think I might consider this.
Nope,
to much flow for the size (Micro ?).

For the Harrier you would need a rather big fan with high static thrust.
So a lot of blades and a low angle of the blades seems to be better.
The discussion was already going for EDF for airliners that need thrust not speed.

Maybe Klaus (Winmodels) has some suggestions, but I belive we need a fan for low speed but high static thrust.
The ducting will cause some back preasure and this might cause high flow EDF to stall before reaching the desired thrust.
Schübler and WeMoTec may therefore be also not optimal as both are designed for high flow.

regards Peter

[QUANTUMPHYSICS]

Nope,
to much flow for the size (Micro ?).

For the Harrier you would need a rather big fan with high static thrust.
So a lot of blades and a low angle of the blades seems to be better.
The discussion was already going for EDF for airliners that need thrust not speed.

Maybe Klaus (Winmodels) has some suggestions, but I belive we need a fan for low speed but high static thrust.
The ducting will cause some back preasure and this might cause high flow EDF to stall before reaching the desired thrust.
Schübler and WeMoTec may therefore be also not optimal as both are designed for high flow.

regards Peter




Maybe a 120mm with a very powerful Brushless motor?

I was thinking an AMMO 24-45-3790kv Brushless motor.

[Psionic001]

Maybe a 120mm with a very powerful Brushless motor?

I was thinking an AMMO 24-45-3790kv Brushless motor.


QUANTUMPHYSICS,

absolutely agree. 120mm will be the first easy to design and fly EDF Harrier.
I think mine will just hover (maybe bedstead only) with the wemotec 90mm.

The 120mm will be producing about 19pounds/8kg of thrust with a big motor.

I have promised myself a gift of a 120mm fan if I can hover my 90mm setup!

best,

Matt

[QUANTUMPHYSICS]

QUANTUMPHYSICS,

absolutely agree. 120mm will be the first easy to design and fly EDF Harrier.
I think mine will just hover (maybe bedstead only) with the wemotec 90mm.

The 120mm will be producing about 19pounds/8kg of thrust with a big motor.

I have promised myself a gift of a 120mm fan if I can hover my 90mm setup!

best,

Matt


DO you think it would be logical to use 2 servos (one per side) to handle the thrust vectoring nozzles transition . How are you planning to make your harrier nozzles rotate?

[Psionic001]

Hi QUANTUMPHYSICS,

even though I don't need them at bedstead stage, the design & rotation of the vector nozzles has been my biggest hurdle.

I'll be using one servo for each side I think, that way I can cheat by mixing in a little yaw control to back up the yaw RCV (Reaction Cont Valve). The yaw RCV is the most inneficient as it's a single tube to serve both left/right thrusts, whereas all other RCVs are dedicated.

Also: By stepping up to 120mm size, I'll be playing with bigger parts which will make rotating nozzles easier to design.

If you or anyone else have any great insights into a nice rotating nozzle system, then I'd like some help.

Matt

[QUANTUMPHYSICS]

[QUOTE=Psionic001]Hi QUANTUMPHYSICS,

even though I don't need them at bedstead stage, the design & rotation of the vector nozzles has been my biggest hurdle.

I'll be using one servo for each side I think, that way I can cheat by mixing in a little yaw control to back up the yaw RCV (Reaction Cont Valve). The yaw RCV is the most inneficient as it's a single tube to serve both left/right thrusts, whereas all other RCVs are dedicated.

Also: By stepping up to 120mm size, I'll be playing with bigger parts which will make rotating nozzles easier to design.

If you or anyone else have any great insights into a nice rotating nozzle system, then I'd like some help.

Matt[/QUOTE


I wonder if it would be possible to use two servos and some gears to make each side's ducts rotate simultaneously. I don't think there is any other way to do it and keep the weight down. Except...maybe... two push rods - but would they be able to resist the down force of the airflow when you switch to forward thrust?

Actually, SCRATCH THAT. I think we need a SINGLE servo connected to gears that make all 4 nozzles rotate simultaneously. Otherwise, we'd be putting a huge number of servos in there cause you're gonna need Aileron/rudder and elevator for forward flight.

A gear design that mixes the pitch of the nozzles with the pitch of the Harrier's Main FLAPS.

How exactly would you mix the servos so that they respond to a single input?
I think a 6 channel radio for a HELICOPTER would be in order here.