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New EDF Mini Jets- Sabre & MiG15 RCM&E 2018 Special

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Tony Nijhuis24/07/2019 21:29:34
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609 forum posts
233 photos

Colin,

Firstly the 600g is a guideline as to a 'manufactures stated thrust' which is always in 'open field testing' on a test rig. When buying a fan, you only have the manufactures stated thrust to 'BUY' to!. Im saying that a fan unit with a manufactures stated thrust of 600g, in a model such as the Sabre, will fly it very well indeed. It would be ridiculous to expect modeller to test the thrust of an EDF in there own model and then compare that to a specification....

I know from 'open field' test on a rig the FMS 50mm fan on 3S (11.1V) you will get around 620g or thereabouts. However, put this into model and that figure WILL be reduced due to air flow resistance both in front of the fan and losses after the fan....You could easily lose 50% of your thrust but the model will still fly....why???? because i used a rubbish AEO fan in the test Sabre, that could only muster 380g in free air (and probably 150g once in the model) and that still flew!!!

So if your getting 350g in the model, tested......it will go like a rocket!!!!!!!!!!!!!!!!!!!

Having now developed a further six more jets, the secret is a cheat hole (40mm x 40mm or equiv. CSA) in the under side of the fuselage just 15mm or so in front of the fan and this will UNLOCK the performance of fan. The Sabre side scoops would then be redundant.....

30C Lipos are fine....1800 to 2200mah...perfect......anything more may add thrust but this will be offset against the weight increase.......

Colin Bernard24/07/2019 21:58:39
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503 forum posts
93 photos

Thanks Tony - appreciate the answer - but if I understand you correctly you are saying that it should fly OK, even with a 2200 and the problem is just that it needs a large cheater hole adding?

If so what makes mine, built as per plan, different to yours and the others who say theirs fly OK? (I feel sure that I built accurately, CG was right etc)

Happy to try anything - just need to understand.

Edited By Colin Bernard on 24/07/2019 22:06:50

Tony Nijhuis25/07/2019 21:31:58
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609 forum posts
233 photos

Colin,

I find it unexplainable why this model dose not fly.....If you telling us you measure the thrust of the model at worst being 350g which is 14oz, against an AUW of 21oz you have a 67% thrust to weight ratio which is ample......My sabre flew on a 50% thrust to weight ratio using the cheap AEO fan!

I can only suggest the 40mm x 40mm cheat opening in the underside. Also check your speed controller is giving max output....it is a 40amp controller i assume?

All the latest designs i have produced use the FMS50mm 3s fan and the AUW range from 22oz to 26oz!!!

one last and curious point, did you know you used the Mig canopy on your Sabre!!!!

Colin Bernard25/07/2019 21:40:47
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503 forum posts
93 photos

I am wondering how accurate my thrust measurement is. I simply inverted the model over the kitchen scales as close as I could to the scales without touching them, and then gave it WOT.

I'll stick the wings back on and try adding that cheat hole.

As to the canopy I must have traced off the wrong side of the plan! Never mind, have plenty of pop bottles!

Thanks again Tony - I'll post any updates.

Looking forward to building the Provost next.

(And must summon up the courage to maiden the Vulcan too.)

Tony Nijhuis26/07/2019 17:11:22
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609 forum posts
233 photos

Colin

Try putting the nose of the model on the kitchen scales.....switch them on and they will zero with the weight of the model on them....then give it WOT with just lateraily supporting the model

brokenenglish26/07/2019 18:11:24
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580 forum posts
30 photos
Posted by Tony Nijhuis on 26/07/2019 17:11:22:

Colin

Try putting the nose of the model on the kitchen scales.....switch them on and they will zero with the weight of the model on them....then give it WOT with just lateraily supporting the model

Won't "nose on scales" affect the entry of air? Maybe you'd need standoffs between the scales and the nose.

Colin Bernard26/07/2019 19:01:03
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503 forum posts
93 photos

Tony - I did it tail down for the reason brokenenglish mentioned above.

However since at the moment there are no wings or cockpit on the fuz it's no issue so out of curiosity I did it nose down on a fresh battery and got much the same - 16oz/454g thrust.

And I hate to admit it but yes, I had copied off the wrong side of the plan for the canopy - duh!

Tony Nijhuis26/07/2019 21:49:07
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609 forum posts
233 photos

Ok so put the wings on, cut a 40 x 40 hole and go and fly it.......smileythumbs up

Adam Lomax27/07/2019 16:32:46
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142 forum posts
4 photos

Tested mine a couple of days ago, flew really well with plenty of power on the FMS fan.

Just need to finish the canopy and air scoops now smiley

8c27e6a4-8148-46d7-8abe-9c9d72a706dd.jpeg

Andrew Calcutt18/08/2019 20:02:39
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61 forum posts
1 photos

Finally got mine flying well,I am using an 11 blade fan from bang good,3cell 1300 battery.First couple of attempts didn't work,cut a much larger cheat hole underneath and moved the c of g slightly forward,she now flies well with a good turn of speed.

stuey06/10/2019 12:32:15
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610 forum posts
12 photos

Hi everyone. I am considering the Sabre from the mini jet selection at the moment. So can we say that a 3s 2200 pack is OK with sufficient cheater inlets? I have plenty to use rather than buy some smaller packs. Cheers

Andrew Calcutt06/10/2019 12:41:00
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61 forum posts
1 photos

I fly my mig on a an 11 blade ba good fan,1400 30c battery,cheater holes are essential.I think a 2200 3s may be to heavy.with this setup it flys well just keep the speed up if not it will go into a spin on a turn.

Marc ROCHE01/01/2020 22:15:09
22 forum posts
25 photos
Just a little message to revive the post. My Mig didn t support a fautly servo. I make a new plane
but i modified the tail to make it look like a Mystere II.

20191231_190630.jpg20191231_190646.jpg
Marc ROCHE05/07/2020 18:11:26
22 forum posts
25 photos

hi,

A short video of the MIG15 modified in this hot windy day.

https://youtu.be/0Pjh_Wc4Dyc

Go fast.

Marc

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