Ron Gray Posted July 24, 2019 Share Posted July 24, 2019 Your cheater ducts look to be too far forward? Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted July 24, 2019 Share Posted July 24, 2019 Have you installed the Lipo in a "pannier" under the fuz/wing as per Tony's proto? Quote Link to comment Share on other sites More sharing options...
Steven S Posted July 24, 2019 Share Posted July 24, 2019 My FMS 3S fans tested at: 559 grams thrust 33.8 amps 351.5 watts 10.4 volts I found that a 2200 battery had a very very large frontal area and blocked too much of the airflow, even a 1800 is big. I think his newer designs with the large side inlets and the battery out of the airflow will be a much better design. Edited By Steven Shaw on 24/07/2019 11:50:59 Quote Link to comment Share on other sites More sharing options...
Colin Bernard Posted July 24, 2019 Share Posted July 24, 2019 Thanks to all for your thoughts and suggestions. Piers - appreciate the compliment, thanks! (Not looking quite so good now I've ripped the wings off to get at the ESC for testing!) I agree with you, and the others in that swapping to a 1500 would pay dividends - I just didn't have any at the time. Ron - yes my cheater holes are further forward than the plan due to servos. I wanted to put them as far back as possible to give me more room in the cockpit area. It's cramped enough in there. The position should not make much difference though - the main thing is the amount of inflow available in front of the fan. Interestingly, all my testing has been with the cockpit lid off the fuselage and the battery hanging down the outside of the fuselage in an attempt to get the best reading possible. This gained about 10% over the fuselage closed with the battery inside - not as much as I thought. Alan - the model is built as per plan. If you have a look at the mag you can see the LiPo sitting in the bottom of the fuz. The 'pannier' is a hand hold to assist hand launching - unless I have missed some pics somewhere. Steven - your results are interesting. I see it still falls short of the 620g FMS claim and the 700g some have reported. With you using a proper test setup I trust those figures more than simply upending over some kitchen scales which is what I do currently. So next steps - compare the AEO; get some 1500 LiPos; stick the wings back on; try again! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted July 24, 2019 Share Posted July 24, 2019 Colin - the cheater holes should be immediately in front of the fan, I’ve played around with these on other edf models and it makes quite a difference! Quote Link to comment Share on other sites More sharing options...
Tony Nijhuis Posted July 24, 2019 Author Share Posted July 24, 2019 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....... Quote Link to comment Share on other sites More sharing options...
Colin Bernard Posted July 24, 2019 Share Posted July 24, 2019 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 Quote Link to comment Share on other sites More sharing options...
Tony Nijhuis Posted July 25, 2019 Author Share Posted July 25, 2019 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!!!! Quote Link to comment Share on other sites More sharing options...
Colin Bernard Posted July 25, 2019 Share Posted July 25, 2019 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.) Quote Link to comment Share on other sites More sharing options...
Tony Nijhuis Posted July 26, 2019 Author Share Posted July 26, 2019 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 Quote Link to comment Share on other sites More sharing options...
brokenenglish Posted July 26, 2019 Share Posted July 26, 2019 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. Quote Link to comment Share on other sites More sharing options...
Colin Bernard Posted July 26, 2019 Share Posted July 26, 2019 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! Quote Link to comment Share on other sites More sharing options...
Tony Nijhuis Posted July 26, 2019 Author Share Posted July 26, 2019 Ok so put the wings on, cut a 40 x 40 hole and go and fly it....... Quote Link to comment Share on other sites More sharing options...
Adam Lomax Posted July 27, 2019 Share Posted July 27, 2019 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 Quote Link to comment Share on other sites More sharing options...
Andrew Calcutt Posted August 18, 2019 Share Posted August 18, 2019 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. Quote Link to comment Share on other sites More sharing options...
stuey Posted October 6, 2019 Share Posted October 6, 2019 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 Quote Link to comment Share on other sites More sharing options...
Andrew Calcutt Posted October 6, 2019 Share Posted October 6, 2019 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. Quote Link to comment Share on other sites More sharing options...
Marc ROCHE Posted January 1, 2020 Share Posted January 1, 2020 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. Quote Link to comment Share on other sites More sharing options...
Marc ROCHE Posted July 5, 2020 Share Posted July 5, 2020 hi, A short video of the MIG15 modified in this hot windy day. https://youtu.be/0Pjh_Wc4Dyc Go fast. Marc Quote Link to comment Share on other sites More sharing options...
Ben May Posted September 1, 2020 Share Posted September 1, 2020 hi, What percentage of dual rates and expo have others setup in their transmitters for this model? I found on my first flight the controls were super sensitive! TIA Quote Link to comment Share on other sites More sharing options...
Marc ROCHE Posted April 24, 2022 Share Posted April 24, 2022 Bundeswehr Sabre f-86. I hope to have as much fun as with other minijetNijuis Models. 1 Quote Link to comment Share on other sites More sharing options...
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