watt_the!

thought i'd start a thread and then summarise it later..

in another thread, a member- "the ghost" is describing his $600US setup that delivers 17lb thrust from a byron fan in an f16 (with retracts) with an AUW of 12lb.

He's running max C of 15 and most of his flight is spent under 8C.

overhead on the ESC is 30-60%.


To me this is finally feasible for the larger, previously turbine only models- and with the regs for turbines it makes more than just financial sense.

I thought I'd start a thread comparing turbines to an equivalent EDF setup.

The first one being the smaller of the wren turbines..the first real natural choice for DFers other than those who try the JetJoe...

the idea is to take the turbine, its fuel and all accessories, plus the ductwork as the weight and cost.

then compare the same to the EDF equivalent. obviously EDF wont need any heat shields and im figuring battery weight may be comparable to fuel.

Duct size is a consideration also.


For those who are technically minded, im not intending to get into the pressure and sound argument. this is just to compare it for those who may be considering the options they have for certain types previously reserved for turbines or even ICDF only.

We wont go down the speed argument either. Sure theres tradeoffs- the focus is on thrust.

any comments and comparisons most welcome.

Tim

The Ghost

Tim, I don't know weather the turbine models would be good for electric conversion as they are made a lot heaver that the older fan models. The conversion of the fan to turbine or Electric DF would be a better comparsion as the models you would be looking at are models that people have sitting in their hangers or houses and are looking at converting to turbine.
Look at conversion with nothing.
Most turbine conversions require turbine and controlling equp($$$). Then fast charger for turbine batteries, fire ext, relevant regs for area, fuel container and pump system to fuel model. Then you are controlled by the regs of the aera that you live in as to when you can fly as well as any inspections required to fly the model. A lot of messing around if you don't live in an area where there are turbine inspectors. I know as I have had turbines and sold them because of all the regs assoated with them. Don't get me wrong there are great, the sound, smell and preformance.

To convert one of the engine powered DF's to electric all you need is a motor, speed controllers(using exsisting fan) and batteries (mine would have cost around US$600) as I allready had the batteries that I used in electric prop planes and a charger for LiPo's or the batteries that you use. Then it is just the same as it was except that it is electric powered and you would be able to fly any where you could fly it before. A lot of flying sites you are not allowed to fly turbines from. As for preformance you should be able to get it to at least orignal or better. My setup has given me at least 5lbs thrust more that orignal.

Cheers

watt_the!

good points. I guess what i was really saying was that turbine was previously an area that existed primarily becuase of the performance required.

i was considering it as an alternative- where possible- to turbines as a power source. For instance to me it would seem that the Feibao jets would be good candidates.

watt_the!

Wren 44, $2500US, total weight including fuel, 1550g (approx 3.5lb)

Thrust 45N (10lbs)
Size 215mm x 75mm
(8.5in x 3in)
Weight 600g (21oz)
Fuel Consumption 176ml / min
(5.7oz / min)
Flight Time 5.5 minutes full power on 950ml tank


at 3 inch diameter theres probably still nothing that is equivalent to this turbine.

the option would be to go for a 70mm or preferably a 90mm fan....the 70mm fan options can't compete.

im looking for recent data on 90mm or even the new 85mm schuebeler fans.

Ron101

My Feedback: (22)

Hey Tim,
I’ve been flying large electric jets for over a year now and have put lots of time into research and driving to jet meets to watch as many EDF’s fly that I can. I also spend too much time at the other rc site (no supposed to say it here) there is much more info and guys building and flying these jets. The main problem you’re going to find trying to convert a turbine plane in intake ducting. To get the best performance you can from an EDF you need good intake ducting. So unless you’re really good at making a plug for the ducts and glassing it, you’re going to have a tough time. That’s not to say many great conversions aren’t going on. I just sold a cermark F-16 with no intake ducting, it has a DS-94 with a neu motor 1527 on 12s 5000 mah packs.. This was a great plane and flew really nice. But as a comparison I also have a Tam Jet’s A-4. Tam makes the ducts to convert his turbine plane to electric. He also had the factory lighten the airframe. This plane weighs 17 pounds (two pound more that the F-16) it also has a 1521 neu motor..which is a smaller motor and draws less amps. This plane out performs the F-16 in every way.
It’s because of the intake ducting. Its top speed is close to 160 mph .. with a 5:00 flight time. The F-16 with no ducting was about 135 mph with a 3:30 flight time. If you want the best performance you need a plane that was designed to be EDF from the start. Planes like the BVM electra and the comp arf spark are 195 mph planes, unlimited vertical and 5:00 to 7:00 minute flight times. I’m doing a spark right now .. with a Tam Jets fan it will out perform many turbine planes. Here is a cost comparison for you.

The spark is $1200
The ready to fly Tam Jet 100 mm fan (fan, ESC, motor) $1000
Retracts, wheels, brakes $400
RX, servos $500
Total = $3100

I never add the price of the batteries that the fuel for two years.
You could fly it one cheap 8s packs for $300 bucks
Or top of the line 11s packs for $700

Just a small turbine will cost you $2500 bucks, don’t even look at jet joe there a joke.
So even if you converted the very same plane (the spark) to turbine you’re talking $4600 dollars. Jet fuel is not cheap either and you will burn A LOT of it. I fly with turbine guys all the time. They buy a 5 gallon can of kerosene for $35 to $40 dollars add a $12 can of aeroshell oil to it and burn one to two cans a day. So you can easily burn $50 to $100 of kerosene at a jet meet. I’ve heard of some burning 5 gallons at a meet ($250). These same guys make a big deal of the cost of batteries. The newer good cells get get anywhere from 100 to 300 flights and now with a 5c charge you can recharge if 30 to 15 minutes.

Take a look at Tam Jets. Tam makes ducting for almost all the yellow aircraft kits and many others. His fan is one of the best on the market. If you want to do an older ducted fan plane check out the dyn e max. It’s a very well done conversion of the dynamax.
Here’s a link to a flight video: http://vimeo.com/2389252

There are many nice units on the market and lots of ways to get it done. From my experience just really research before you buy. And don’t try and cheap out.. most of the time you get what you pay for.

Ron