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Old 10-07-2019, 09:29 AM   #11
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Re: Converting EDF to turbines


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EDF versions of twin powered jets like the F4, F18 have a single fan which pushes air through a ducting tunnel. The tunnel is split near the rear to maintain the looks of the two exhaust nozzles. This works fine with air but you can imagine the outcome if the air was 600 C from a turbine....lol

The solution is to cut out the tunnel into one large single duct and place a straight pipe. This means you have to cut the inner parts of the exhaust nozzles on the model...or you can place the turbine in the same spot as the ducted fan unit but slightly angle it so the exhaust gases just go out one of the nozzles. The thrust is so close to the center line that the model exhibits no trim issues. This is an asymmetric set up.

Bifurcated means... a single pipe splitting off into two pipes. This maintains the scale look of the model but comes at a price of weight, complexity and some thrust loss. Not generally used in models smaller than 120N powered.
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Old 10-07-2019, 11:14 AM   #12
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Re: Converting EDF to turbines

Isn't there a pretty good risk of a fire having a hot jet engine inside of a styrofoam airplane?
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Old 10-07-2019, 12:00 PM   #13
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[QUOTE=Helijet;3725253]I have put a Kingtech 60 in the HSD F16. It flys well but it is a bit heavy for the small airframe. The EDF version flys better overall IMO.

What's size is your tank and flight times with kt 60?
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Old 10-07-2019, 03:14 PM   #14
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Re: Converting EDF to turbines

cast-away....about as much as fibreglass and wood....lol
With good air flow and a properly designed exhaust duct no problem at all....
JETco… I used the tank that came with the HSD F16 turbine package & 6:30 with reserve.

dw
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Old 10-07-2019, 05:41 PM   #15
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Re: Converting EDF to turbines

Received the first conversion pack from HAB Sweden today for an Avios Mig 17. The 800 cc tank should be good for about 7 - 8 minute flights with reserve. The single walled pipe is 50mm diameter which is appropriate for 35 - 50N turbines. The black pieces are carbon fibre turbine rails and a centering ring for the tube. You will note the use of a felt filter. No uat being used on this one.

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Old 10-07-2019, 05:48 PM   #16
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Re: Converting EDF to turbines

Mini Avanti came today. This is a 90mm EDF that lends itself well to turbine conversion. It features a fibreglass fuse / wood-foam ultracoat covered wing. My son Eric showing off its huge size.....lol
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Old 10-07-2019, 05:52 PM   #17
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Re: Converting EDF to turbines

The Freewing 80 mm Avanti and the 90mm for relative sizing. Not much difference. The Mig 17 subject is in the background. I have lots of flights on it in EDF form and should prove to be a good flyer. I will be replacing the stock wheels with JP Models 60mm wheels and brakes as she will be flying off our local paved flying field at KMAS.
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Old 10-08-2019, 04:43 PM   #18
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Re: Converting EDF to turbines

So lets talk fuel tanks. Keeping in mind that there is no pressure required in the tanks most any container can be made to work in the smaller jets. I have seen small soft drink bottles, shampoo and juice bottles etc. I am not a fan of the expensive Kevlar offerings as they are heavy and offer no more or less safety in small models than plastic ( ie Dubro, Sullivan ). What is more important is to ensure a good gas compatible seal / stopper is used.
I have used tygon tubing for years as its readily available and inexpensive. Here is an interesting option....I am going to use these 24 oz tanks that I got through Valley View RC. They cost about $25 US but have some key features I like...metal fittings, additional fill line, heavy felt clunk with supported internal fuel line and..clear!
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Old 10-08-2019, 11:40 PM   #19
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Re: Converting EDF to turbines

Quote:
Originally Posted by Helijet View Post
Received the first conversion pack from HAB Sweden today for an Avios Mig 17. The 800 cc tank should be good for about 7 - 8 minute flights with reserve. The single walled pipe is 50mm diameter which is appropriate for 35 - 50N turbines. The black pieces are carbon fibre turbine rails and a centering ring for the tube. You will note the use of a felt filter. No uat being used on this one.

dw
Hi Dean, I'm trying to understand the lack of use of UAT, (other than space) the felt clunk has been discussed a few times on forums where some say it's all that is needed, but the buy in is very limited if at all. Most if not all manufactures recommend an air trap.? not sure what the x45 spec's out

does it have something to do with the lower fuel flow that reduces the need or is a high quality felt clunk good enough to eliminate any bubbles. I certainly like the idea but never had the guts to try.

I believe the in air auto restart is very fast... a good back up

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Old 10-09-2019, 01:37 AM   #20
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Re: Converting EDF to turbines

Excellent comment Angus. I still use a UAT type tank in my big stuff - partly because of old habits but it also gives me an idea as to how patent my fuel system is. Any small leaks - for example around the stopper or a festo connection can more easily be found. The volume of flow is much higher as you stated and the possibility of a large bolus of air is more likely in a high flow delivery. In days of ago - its true that the combustion and ecu programming were not tolerant of air bubbles. Todays turbine are a different beast. The diffusers and combustion designs have come a long ways to the point that small bubbles do nothing but decrease the full thrust output and in fact, the ecu in many cases, compensates for it. Felt clunks are nothing new. Carf has been using them for years and many kit suppliers use them in the main tanks. The clunks themselves are standard in high vibration 2 stroke appliances such as chainsaws. What needs to be noted is proper cleaning of filters downstream, as over time, the small felt threads accumulate. In the small engines this may need to be addressed every 15 hours or so. At the end of the day - I am looking at keeping the small birds as light and simple as possible. The flow rate mentioned earlier is also much, much less ( max 3 oz per minute ). John at Wren turbines has always used a felt filter - never an airtrap and has had good success. More smaller turbine operators ( 80N and less ) are changing over as well but use what works for you. If you are more comfortable with an air trap of some sort than by all means use it. I'll try just the felt pick up in these small engines for now and will report back my findings......I may fly a little higher for the first few flights...lol

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