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Harrier Jump Jet- The aeromodelling Holy Grail !!!!

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Ian Newton21/01/2017 23:44:13
68 forum posts
10 photos

Oh no! That's such a shame. Still at least you have learnt a lot and each step brings you closer to success

bouncebounce crunch22/01/2017 04:21:08
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1739 forum posts
212 photos

Yes, that is a shame. This aeromodelling is far from my skills and knowledge, it is more toward NASA x British aerospace to me.

I hope you beat the challenge Tony.

bbc

Tony Nijhuis22/01/2017 22:21:57
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609 forum posts
233 photos

Thanks guys.....fortunately the wings survived and new fus is almost finished....Its too close to stop now.....

John Holdsworth 108/02/2017 16:17:27
1 forum posts

OpenAeroVtol?

Just a suggestion since its been designed for this kind of thing and combines gyros/accelerometers etc into a relatively easy to configure package..based on the kk2.1 boards which are widely available and cheap.

In any event.... good luck

bert baker08/02/2017 17:33:58
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1503 forum posts
306 photos

In thrust we trust

Tony Nijhuis08/02/2017 21:59:21
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609 forum posts
233 photos

There will five monthly articles starting next month (April issue) about trials and tribulation to date...so 10,000 words of explanation!!!crook

just waiting for some better weather before venturing to the flying field again

Keith Simmons08/02/2017 23:18:10
449 forum posts
9 photos

That's great. Looking forward to read your monthly articles and gain some insight.

Martin McIntosh09/02/2017 10:12:54
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3035 forum posts
1116 photos

I expect that you have looked at this already, but I have been watching some YouTube videos on the E-Flite Convergence. There is a lot of stuff on home brewed VTOLs too.

adam gordon-duff15/02/2017 21:59:42
3 forum posts

Hello everyone. Just a thought but would say 4 x 6" props give you better efficiency through static thrust? After all most quadcopters are prop powered? It's a large model so maybe even bigger props could be accommodated whilst still respecting scale appearances? Be gentle with the explaination of why not as I'm sure I'm missing something with this simple thought?!....All the best, Adam

Steve Cheyne20/02/2017 11:55:34
1 forum posts
5 photos

Tony, I have just been made aware of your efforts by a friend of mine, looks like we have been working in parallel using the same design though mine is smaller using 4s and 50mm fans made from depron. I used a "flying bedstead" to derive the available thrust, control laws and vectoring system and my winged version is just being painted before first fligh. Currently the model weighs 1.5kg and I have 2.7 kg of (uninstalled ) thrust. Unfortunately it is my first time on this site and I am having trouble attaching photos, if you are interested I will email them directly, meanwhile I will try and find a young person to help me!

John Lee28/03/2017 13:47:07
685 forum posts
52 photos

scan 2017-3-28 0003.jpgTony

In the April edition of the RCM&E you state that you are looking to transition with the fans in 3 positions 90, 45, 0 degrees.

John Farley in his excellent book 'A view from the hover' states that for the pilot training for the transition of the full size Harrier they use an initial nozzle position of 15 degrees aft from a steady hover. To quote

'while such a change loses you only about 3% of your engine lift (or gives a 0.03g sink if you prefer)' it provides a very smart forward acceleration of some 0.25g. Pure piloting magic! That is why Harriers are able to leap forward from the hover without any obvious sink. That 3% vertical loss represents about 1% on the rpm gauge so, if you add a touch of throttle before you move the nozzle, the rush of lift from the wing as the IAS increases will soon have you up & away. I bet you never realised that Sine/Cosine relationship could be so useful!'

In contrast a 45 degrees nozzle angle will lose you 30% of the lift.

Tony Nijhuis31/03/2017 23:34:42
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609 forum posts
233 photos

Thanks John,

That's interesting and make good sense......

Tony Nijhuis29/05/2017 21:12:54
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609 forum posts
233 photos

Well its been some time since i last posted and hopefully the articles in the RCM&E were of interest.....

Needless to say i thought by the time I had done the four articles, i may have some good news for you but this project is still very much on going and sometimes i think I'm just treading water.

The hover is now very much sorted but (quadcopter) yaw control is poor and with any small amount of wind, the harrier will happily weather cock like a weather vane..... However today was the transition day down the Hastings club field and the harrier moved into into stage 1 forward flight with the fans switched from vertical to 20deg forward angle...interestingly, model did not accelerate is fast as i thought it would and didn't reach what i thought was a forward speed sufficient to go stage 2 (fans full forward 90deg).

So i increased the stage 1 rotation to 40deg..... this time the harrier accelerated from hover nicely and kept straight and level as she moved away (still in quadcopter mode) then switched to stage 2 hoping she would power away in normal acro mode but instead she reared up vertically, flicked on her back ....at this point I thought that was the end so I hit the switch to return it to hover and incredibly she self righted an I hovered her to ground.....if i hadn't of done that, there is no way it would have survived.

Not quite sure why the model reared up but may be down to the fan thrust line still being at an angle when the when all 4 fans then go to the same speed and this kicked the model up. As the fans are under the wing, the thrust, even when the fans are horizontal, will cause the nose to rise.

Notwithstanding this....a positive day I think!!!!

Tony Nijhuis29/05/2017 21:37:30
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609 forum posts
233 photos

i suppose being an engineer, i alway like to have a backup plan so this is the latest design which now overcomes the yaw problem.

Model has now test flown in hover and work great.....it uses a nano Wii board instead of a KK2 quadcopter board.

The difference is that fans are pivot controlled independently by a servo so yaw is now done with gimbling the fans, backward on one side and forwards on another. The result is the model now yaws with authority and better still, i don't need contra-rotating fans .....they all rotate in one direction and the yaw control deals with the torque effect.

the test model is purely a hovering test bed and the model AUW is just over 1kg.....

img_4649.jpg

img_4648.jpg

img_4650.jpg

Edited By Tony Nijhuis on 29/05/2017 21:38:40

Edited By Tony Nijhuis on 29/05/2017 21:39:23

Guvnor29/05/2017 22:40:59
122 forum posts

Has anyone seen this one...?

https://www.facebook.com/f35model

Edited By Guvnor on 29/05/2017 22:41:32

Ernie31/05/2017 12:37:30
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2515 forum posts
21 photos

Many many years ago, i took my wee daughter to an airshow (leuchars perhaps)

That plane I said, pointing to the harrier is going to stop in mid air Dont be so stupid was the reply, as 10 year olds do.

So we got to the front of the crowd, right at the middle of the flightline It was perfect..It flew slowly straight towards us and of course stopped

wonderful

ernie

Steve Houghton 131/05/2017 15:18:28
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1897 forum posts
128 photos

Back when 3 & 4 Squadron were operating Harrier GR4's out of Gutersloh. Germany, the station song was Queens, Another one bites the dust, and I remember attending at least two crash sites. One just a few miles from camp, near to where we had a large bulk fuel installation, and another near Frankfurt where the aircraft had crashed through the last of a row of houses. The brave, selfless pilot stayed with his craft to ensure he kept casualties to a minimum. As I remember, fortunately I think he was the only casualty.

Then I was having my lunch at my work place one sunny day when I heard a loud bang and we all ran to the window. A Harrier had been hovering over the runway when something went wrong. The pilot had banged out, but because the aircraft was at an angle at that moment, the pilot ended up in the bomb dump before his chute deployed, and the Harrier crashed on the runway.

They always performed great at airshows, and everyone would want to see their display, but they were notorious for crashing.

Tony Nijhuis04/06/2017 23:26:33
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609 forum posts
233 photos
Posted by Tony Nijhuis on 29/05/2017 21:12:54:

Well its been some time since i last posted and hopefully the articles in the RCM&E were of interest.....

Needless to say i thought by the time I had done the four articles, i may have some good news for you but this project is still very much on going and sometimes i think I'm just treading water.

The hover is now very much sorted but (quadcopter) yaw control is poor and with any small amount of wind, the harrier will happily weather cock like a weather vane..... However today was the transition day down the Hastings club field and the harrier moved into into stage 1 forward flight with the fans switched from vertical to 20deg forward angle...interestingly, model did not accelerate is fast as i thought it would and didn't reach what i thought was a forward speed sufficient to go stage 2 (fans full forward 90deg).

So i increased the stage 1 rotation to 40deg..... this time the harrier accelerated from hover nicely and kept straight and level as she moved away (still in quadcopter mode) then switched to stage 2 hoping she would power away in normal acro mode but instead she reared up vertically, flicked on her back ....at this point I thought that was the end so I hit the switch to return it to hover and incredibly she self righted an I hovered her to ground.....if i hadn't of done that, there is no way it would have survived.

Not quite sure why the model reared up but may be down to the fan thrust line still being at an angle when the when all 4 fans then go to the same speed and this kicked the model up. As the fans are under the wing, the thrust, even when the fans are horizontal, will cause the nose to rise.

Notwithstanding this....a positive day I think!!!!

Decided to give it another go toady, but made a few modification in particular moving the CofG forward by 1/2" (because of last week's violent 'rear up', positioning the fans at stage1 to 45deg (to give greater forward speed) and decided to keep the quadcopter board operating until the fans all all became horizontal.

The wind was quite strong so she was get blown back in the hover so back on the ground I decided to take off at stage 1....(45deg fan position)...doing this the harrier gently rose off the ground, accelerated forward and climbed to around 20' under quad controll before gingerly switching to stage 2 (full transition).....this time, no change in pitch, she just accelerated away into normal flight.......fantastic....Managed about 5 circuits before and decided to land conventionally with no bother.....Finally get somewhere!

Doing some further test this afternoon and hovering into a head wind, all the fans need to be set at 10deg forward for a 10mph wing and I would suspect 15deg for a 15mph wind.

Chris North 305/06/2017 07:35:19
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316 forum posts
512 photos

Tony,

I have never designed a plane so probably have no right making comment but from what I understand wind loading is a function of wind speed squared.

Wind Loading = Area x Wind Pressure x Friction Coefficient and, since the model is the same, Area and Friction are constant and so can be ignored.

Wind Loading = Wind Pressure = 0.00256 x (wind speed)2

Which means that the wind loading at 15 mph is about 2.25 times that at 10mph (Wind Pressure (.256 llb/ft2 at 10mph and 0.576 llb/ft2 at 15mph)

If your fans were angled at 10 deg in 10 mph wind they will need to be angled to give 2.25 times the forward thrust in 15 mph wind.

Forward thrust at 10 degrees = Sin 10o = 0.1736 so forward thrust required at 15 mph = 2.25 x 0.1736 = 0.2588

Therefore Sin-1 0.2588 means required fan angle will be 20.3 degrees

Martin McIntosh09/06/2017 21:00:54
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3035 forum posts
1116 photos

For some reason I was flicking through Dec 91 RCME and came across this in an article on finishing techniques. No further details.

2017-06-09 17.33.11.jpg

2017-06-09 17.35.54.jpg

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