Avonds F 15-are 90N enough?
11-05-2002, 11:49 AM
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Avonds F 15-are 90N enough?
Please give me some informations about your power package in P.Avonds F 15....and how it flies with the engine you use.
Thanks.
Julian
Thanks.
Julian
11-05-2002, 12:15 PM
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Avonds F 15-are 90N enough?
I have just started flying an as yet unfinished PA F15, it first flew on a p120 at 117k then the engine was set to 120k the model just gets better and better although the vertical performance from low airspeed was just adequate.
I now have a 160 in it.......WOW.... this engine was factory set at 123k and the performance is as full-size.
I can fly past slow with the gear and the air brake out open the throttle,retract the gear and the airbrake and from just above stalling speed the model will accelerate straight up.... WOW.
I now have a 160 in it.......WOW.... this engine was factory set at 123k and the performance is as full-size.
I can fly past slow with the gear and the air brake out open the throttle,retract the gear and the airbrake and from just above stalling speed the model will accelerate straight up.... WOW.
11-05-2002, 03:38 PM
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F15
Avonds F15 flys great on 12 lb thrust PST J600/MW54 power if built as per Avonds original design. Keep it light eg under 20 lb AUW and you will have a sweet flier.... If you plan on speed brake, rudders, rockets and many ad ons. a turbine set-up for 17- 22 lb thrust is keeping within sensible thrust range. I would not go any higher in thrust for my F15, My TJT 3000 derated to 20-22 lb thrust is already pleanty, I do not feel my F15 needs anymore thrust...
11-05-2002, 07:39 PM
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Avonds F 15-are 90N enough?
Are 90n enough for what, if you wish the model to perform a little better than with a fan then yes, if you wish the model to perform more like the full size which is surely why we fit expensive miniature turbines in our models, you need as much power as is legally reasonable.
I do not consider too much power to be a problem but the inappropriate use of the throttle to be the issue.
You would not expect to see a full size 777 to be flown flat out everywhere!
My F15 which has arguably too much power is a delight to fly flown from a grass strip take offs are drama free, because the model is flown much of the time on half throttle the engine response is good the fuel economy is excellent. IMHO too much power is less of a problem than not enough.
I do not consider too much power to be a problem but the inappropriate use of the throttle to be the issue.
You would not expect to see a full size 777 to be flown flat out everywhere!
My F15 which has arguably too much power is a delight to fly flown from a grass strip take offs are drama free, because the model is flown much of the time on half throttle the engine response is good the fuel economy is excellent. IMHO too much power is less of a problem than not enough.
11-05-2002, 09:47 PM
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Avonds F 15-are 90N enough?
For a change, I agree with our friend Mick. And yes, the Britt gentleman said it first
.
There is not too much power, there is only misuse of that power. You can always detune the thrust or use the throttle with respect.
With good power to weight ratio, you take off almost vertically, it is a wonderfull sight. Then you can throttle back and relax and enjoy the flight at 1/4-1/2 power. Remeber, bigger turbine are more fuel efficient at same Thrust than smaller ones.
.There is not too much power, there is only misuse of that power. You can always detune the thrust or use the throttle with respect.
With good power to weight ratio, you take off almost vertically, it is a wonderfull sight. Then you can throttle back and relax and enjoy the flight at 1/4-1/2 power. Remeber, bigger turbine are more fuel efficient at same Thrust than smaller ones.
11-06-2002, 07:15 AM
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Ehab !
Remeber, bigger turbine are more fuel efficient at same Thrust than smaller ones.
Where do you get this idea from ? It really is not correct, yet I have seen several similar comments on RCU several times.
When a model/miniature turbine is designed (I don't know about full-size turbines) the designer works to get the best fuel consumption at 70% - 100% throttle settings, as that's where they are normally operated.
Check out the fuel consumption at idle, or even 20% throttle settings versus thrust and compare this ratio with the thrust v fuel consumption at full power. You will be surprised at the low efficiency at very low throttle settings !
All model/miniature turbines I have experience of are more fuel efficient (for thrust produced) at higher throttle settings, say above 70%.
This is not to say I don't agree with Mick Burrells comments - much better to have too much thrust and use the throttle, than not enough thrust. Also less possible stress/wear of the turbine when running at lower throttle settings of course, rather than full bore all the time!
To answer the original question in this thread, an Avonds F-15 at even 25lbs wet, flies exceedingly well with a 90N turbine, although the vertical is not stunning. Flying from grass is also easy with 90N installed thrust.
Just my .02 Eurocents worth !
Mike C
11-06-2002, 07:43 AM
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Avonds F 15-are 90N enough?
Hi Mike C;
I think you may have misunderstood my comments about bigger engines vs smaller ones. Let me explainn: a P80 at 15 lbs of thrust consumes, let's say 5.8 oz of fuel per minute (just as an example). A P120 at 15 lbs of thrust will consume 4.9 oz per minute. That's what I meant by SAME THRUST. So, a P160 may consume may be 4.5 oz....These are only rough examples but I think you get the point. Fuel efficiency vs RPM for a turbine is a totally diffirent thing all together.
Hey Mick;
I may be getting an F15 by airmagic and a P160 will go in it!!!! will let you know
I think you may have misunderstood my comments about bigger engines vs smaller ones. Let me explainn: a P80 at 15 lbs of thrust consumes, let's say 5.8 oz of fuel per minute (just as an example). A P120 at 15 lbs of thrust will consume 4.9 oz per minute. That's what I meant by SAME THRUST. So, a P160 may consume may be 4.5 oz....These are only rough examples but I think you get the point. Fuel efficiency vs RPM for a turbine is a totally diffirent thing all together.
Hey Mick;
I may be getting an F15 by airmagic and a P160 will go in it!!!! will let you know
11-06-2002, 12:34 PM
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Airmagic F15
Hi Ehab,
I see you might be getting an Air Magic F15?
I just purchased one and was going to go with a P120
Well this thread is making me rethink that! I will be doing a few option's but plan on flying it without for the test flight's..so really is there that big a difference in the turbine's? Or do you get used to the speed it goes now and then go .."you know let's make this baby go FASTER!" Know what I mean?
Thank's and hey were close..maybe formation flying sometime!?
Kevin
I see you might be getting an Air Magic F15?
I just purchased one and was going to go with a P120
Well this thread is making me rethink that! I will be doing a few option's but plan on flying it without for the test flight's..so really is there that big a difference in the turbine's? Or do you get used to the speed it goes now and then go .."you know let's make this baby go FASTER!" Know what I mean?
Thank's and hey were close..maybe formation flying sometime!?
Kevin
11-06-2002, 05:18 PM
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Avonds F 15-are 90N enough?
Hi Kevin;
The Avonds/magic F15 is a very big and draggy plane for a p80, a P120 is better and the P160 is even beter. You gain in accelleration and vertical climb not so much in top speed. Plus, a P160 can be tuned down or up based on the airframe........
Yeah, If I get it we'll fly formation, Chris and I did it with Bandits and it was a blast!!
The Avonds/magic F15 is a very big and draggy plane for a p80, a P120 is better and the P160 is even beter. You gain in accelleration and vertical climb not so much in top speed. Plus, a P160 can be tuned down or up based on the airframe........
Yeah, If I get it we'll fly formation, Chris and I did it with Bandits and it was a blast!!
11-06-2002, 05:55 PM
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Fuel consumption figures
Hi Ehab,
With all due respect I did not misunderstand you - and FWIW I think that you are wrong, based on more than 3 years of manufacturing production turbines and much engine testing.
I am not making any reference to RPM, as was also misunderstood in a previous thread - ONLY thrust v fuel consumption at low power settings on large v small turbines.
Are the fuel consumption figures you quote in your message 'manufacturers figures' or just random guesstimates ?
Go and run (the examples you chose) JetCat P80, versus P120 versus P160 and check the fuel consumption of all of them at, say, 12lbs thrust. Of course all should be run on the same test-stand, with the same fuel, the same ambient temperature and pressure conditions, and preferably within a few minutes of each other.
I think you will be VERY surprised at the specific fuel consumptions of each at this thrust level, and am fairly sure
that you will find that the smaller engine is more fuel efficient at that thrust level.
This is certainly the case with AMT NL turbines, however I am not experienced with JetCat turbines. Please do not just trust all the manufacturers specifications, or interpolate any thrust v fuel graphs given by them - go test it yourself!
For those of you that think I'm having a 'cheap shot' at a competitors turbines - you are very much mistaken and will waste your time if you try to get me into a slanging match on that subject!!!! I won't 'bite', and actually have great respect for the performance and reliability of the Jetcat turbines that I have personal experience of.
'Flame-suit on - ready for incoming' !!!
just my .02 Eurocents worth......
Mike C
With all due respect I did not misunderstand you - and FWIW I think that you are wrong, based on more than 3 years of manufacturing production turbines and much engine testing.
I am not making any reference to RPM, as was also misunderstood in a previous thread - ONLY thrust v fuel consumption at low power settings on large v small turbines.
Are the fuel consumption figures you quote in your message 'manufacturers figures' or just random guesstimates ?
Go and run (the examples you chose) JetCat P80, versus P120 versus P160 and check the fuel consumption of all of them at, say, 12lbs thrust. Of course all should be run on the same test-stand, with the same fuel, the same ambient temperature and pressure conditions, and preferably within a few minutes of each other.
I think you will be VERY surprised at the specific fuel consumptions of each at this thrust level, and am fairly sure
that you will find that the smaller engine is more fuel efficient at that thrust level. This is certainly the case with AMT NL turbines, however I am not experienced with JetCat turbines. Please do not just trust all the manufacturers specifications, or interpolate any thrust v fuel graphs given by them - go test it yourself!
For those of you that think I'm having a 'cheap shot' at a competitors turbines - you are very much mistaken and will waste your time if you try to get me into a slanging match on that subject!!!! I won't 'bite', and actually have great respect for the performance and reliability of the Jetcat turbines that I have personal experience of.
'Flame-suit on - ready for incoming' !!!
just my .02 Eurocents worth......
Mike C
11-06-2002, 06:16 PM
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Avonds F 15-are 90N enough?
No problem Mike;
I have flown a Mercury, a P80 and a P120 in a Bandit and I assure you my flight time got longer and longer doing the same routine. Now, I DID NOT use any measuring devices, just the timer on my Tx and the fuel left in the Bandit.
I am also told by Jetcat that THEIR larger turbines are more fuel efficient at same power level. Since I experienced the same thing, I believe it to be true ..so far.
If you can give me some measured data under controlled conditions, I would love to learn the facts!!!
I personally do not feel you're slaming anybody. So please educate me!!!
I have flown a Mercury, a P80 and a P120 in a Bandit and I assure you my flight time got longer and longer doing the same routine. Now, I DID NOT use any measuring devices, just the timer on my Tx and the fuel left in the Bandit.
I am also told by Jetcat that THEIR larger turbines are more fuel efficient at same power level. Since I experienced the same thing, I believe it to be true ..so far.
If you can give me some measured data under controlled conditions, I would love to learn the facts!!!
I personally do not feel you're slaming anybody. So please educate me!!!
11-07-2002, 10:30 PM
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Fuel consumption
Hi Ehab,
Guess I've put my foot right in it now - so will have to find some time to make some test with our 3 turbines to prove or dissprove my point. Will probably be a week or so before I have time, but will let you know results - even if I'm wrong !
However I still think it would be interesting to check out the actual consumption with a P80/120/160 as I think you will find that the figures are not as you listed!
Will be in touch a.s.a.p.
Mike C
Guess I've put my foot right in it now - so will have to find some time to make some test with our 3 turbines to prove or dissprove my point. Will probably be a week or so before I have time, but will let you know results - even if I'm wrong !
However I still think it would be interesting to check out the actual consumption with a P80/120/160 as I think you will find that the figures are not as you listed!
Will be in touch a.s.a.p.
Mike C
11-08-2002, 03:54 AM
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Avonds F 15-are 90N enough?
Thx Mike;
This data you gather will help put some questions to rest assuming proper test methodology. It would be great to do the following:
Run the engine under test at, say 12 lbs of thrust and measure the fuel consumption accurately. now run the 2nd and 3rd engine under the same power and test set up exactly, same day, same fuel...etc...etc. Have a beer on me and Let us know your findings.. not necessarily in that order!!
This data you gather will help put some questions to rest assuming proper test methodology. It would be great to do the following:
Run the engine under test at, say 12 lbs of thrust and measure the fuel consumption accurately. now run the 2nd and 3rd engine under the same power and test set up exactly, same day, same fuel...etc...etc. Have a beer on me and Let us know your findings.. not necessarily in that order!!
11-08-2002, 06:58 AM
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Test methodology !!
Hi Ehab,
When the tests are run they will be done on AMT Netherlands calibrated test stand, as per all tests run on new and repaired motors. We can weight the fuel used accurately (+/- 2grams) per minute.
The 'quick change' system used for restraining doifferent types /sizes of turbines means that we could probably test all 3 within 1 hour at the most!
Will let you know how it goes.
Mike C
When the tests are run they will be done on AMT Netherlands calibrated test stand, as per all tests run on new and repaired motors. We can weight the fuel used accurately (+/- 2grams) per minute.
The 'quick change' system used for restraining doifferent types /sizes of turbines means that we could probably test all 3 within 1 hour at the most!
Will let you know how it goes.
Mike C
