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DUCTED FAN JETS

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Old 01-07-2007, 12:14 PM
  #26
Tomcat_104
 
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Default RE: DUCTED FAN JETS

My starter jet was a TGA F-15 as well. I chose it because of its reputation and the fact that we have a grass field at my club. The TGA uses a Byron's fan and rotates off the grass in about 350', our runway is around 900' long. The TGA was easy to build and easier to fly. I liked it so much I bought a TGA MIG-29 that I haven't built yet. A great 1st DF jet or a great 6th jet I think.

Buddude08,

A great F-18 post. I'll read it closely from start to finish in a little bit. Right now my wife is yelling about her honet-do's!

David

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Old 01-07-2007, 02:25 PM
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Default RE: DUCTED FAN JETS

Take the Xmas lights down or cover the wing, lights - wing ---- uhhh.. WING!!

Dan
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Old 01-07-2007, 02:59 PM
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Default RE: DUCTED FAN JETS

Yeh Dan,

That's easy for you to say, you didn't see the size of the stick that she was holding!!

David
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Old 01-07-2007, 04:18 PM
  #29
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Default RE: DUCTED FAN JETS

That is my brother that built that. I am building my kit from his experience talking to him on the phone and reading his thread.
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Old 01-07-2007, 05:39 PM
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Default RE: DUCTED FAN JETS

His thread is like a video journal I'm going to use to build mine.

Dan
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Old 01-07-2007, 05:49 PM
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Default RE: DUCTED FAN JETS

I ended up taking the lights down anyway.............
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Old 01-07-2007, 06:12 PM
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Default RE: DUCTED FAN JETS

Well, I took down the lights, the tree, the reindeer and I still got beat with the stick. When I'm better one of the first things I'm going to learn is to RUN faster!!!!!!!!!!!!!!!!!!! Now back to the fuselage!

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Old 01-07-2007, 07:17 PM
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Default RE: DUCTED FAN JETS

I have a brand new O.S. 91 for the F18. How long of a break in time would the group here feel comfortable with before committing it to flight? Should I break it in mounted to the fan or put a prop on it?

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Old 01-07-2007, 07:25 PM
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Default RE: DUCTED FAN JETS

Dan,

I don't know if I did mine right or not but I hooked my OS 91 to the Dynamax fan for break in. I ran 3 tanks (16 oz) through it very rich then 2 tanks through it not as rich and 2 more tanks through it only slightly rich. This might have been overkill but it was recommende to me by another DF pilot. I don't plan to run again until it goes up in the plane. It will be interesting to see what other folks say.

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Old 01-07-2007, 07:26 PM
  #35
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Default RE: DUCTED FAN JETS

this last weekend we put maiden flight on my brothers. We ran a couple of tanks through the bird to dial in the needle settings and then flew it. On my brothers post shaun evans put a post on there on how to break it in and set it. these engines have a matched piston and sleeve. they dont have to get as warm as your standard abc where the engine has to get hot for the piston to move though the sleeve. We used a mc-09 plug. The engine ran great with that plug. We did the break in with 5% and then ended up using 10% to fly it because he was taking off of grass and it need the extra power to rotate.

ken
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Old 01-07-2007, 07:28 PM
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Default RE: DUCTED FAN JETS

Is the 91 as easy an engine to get along with as other O.S. products? I have always been very happy with the reliability and ease of use with my other O.S. motors.
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Old 01-07-2007, 07:29 PM
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Default RE: DUCTED FAN JETS

How much runway do you think you needed to get the Hornet up?

Dan
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Old 01-07-2007, 07:51 PM
  #38
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Default RE: DUCTED FAN JETS

the engine was very easy to start. The low end was pretty fat, i think we dialed that in about a half turn. Also make sure you get the correct starter probe, and apply some grease into the nut and on the tip of the probe this will help in set in easier.Make sure you have a hemostat on your fuel line while fueling it. If you dont it is very east to hydrolock it up and then you have to remove the glow plug. As far as runway goes. if you are on grass you better have at least 400', i would suspect on a paved one it would rotate fairly quickly.

ken
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Old 01-07-2007, 08:29 PM
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Default RE: DUCTED FAN JETS

Is the gyro a must on the nose wheel? I've read that it can get quite squirrely with ground handling.

Dan
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Old 01-07-2007, 08:39 PM
  #40
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Default RE: DUCTED FAN JETS

Hi Greg,

The Skyburner is still waiting for its first flight. I need to sort out family stuff first. The pipe I have is the one from Trim Aircraft. Works great and its length and coupling is preset so just need to slot in position and you're ready to go. I didn't like the retaining springs for these pipes so I made my own using alumium stock. Its similar to one you can buy from BVM. See picture below.
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Old 01-07-2007, 11:59 PM
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Default RE: DUCTED FAN JETS

Is that Trim Aircraft F-20 still available? I had a FlightTech (Cressline) F-20 years ago. Lost it on the 6th due to motor failure. Would love another F-20 for DF.

TGA-15, TGA-Intercepter, Byron F16 Were my favorite DF, due to the fact my club never had pavement. I had to drive 1 hour to a pave runway to fly my F-20. I got a Byron BD-5 for turbine conversion, but that will probably be my only turbine project, untill then DF flyer I am!
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Old 01-08-2007, 12:07 AM
  #42
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Default RE: DUCTED FAN JETS

hi zagzoo, trim no longer make any aircraft but they do still have good support and a lot of other jet stuff. mafrasca do you have a photo of the spring clamp and the one you made? http://www.trimair.com.au/index2.html
thanks greg
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Old 01-08-2007, 12:18 AM
  #43
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Default RE: DUCTED FAN JETS

BTW.. anyone still got the phone number for TGA?
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Old 01-08-2007, 01:31 AM
  #44
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Default RE: DUCTED FAN JETS

This looks like the thread to put forward my questions. Many many years ago, I bought two Turbax fan units and two K & B fan engines from the States. Never got round to using them, (new, still in boxes), changing direction to diesels and unusual aircraft. Interest in ducted fans renewed when offered a near completed Phanton scratch built fron a Thorps Bros plan, 46 to 60 size? Very well built, light, otherwise I would not be interested. To me, power using a .46 would be marginal. I know there are later versions of the original Turbax but, now the question: Would the Turbax fan unit be able to be used with a Rossi, rear exhaust, same vintage (NIB also)? Is there a difference in fan size in the Turbaxes? Comments please. Oh, yes, would love a turbine but have to keep bread on the table for the family. Would rather cuddle up to the wife at night than to cuddle a turbine through the day. Glen
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Old 01-08-2007, 01:37 AM
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Default RE: DUCTED FAN JETS

OOPs, forgot to mention the Rossi would be a .60. Glen
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Old 01-08-2007, 05:33 AM
  #46
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Default RE: DUCTED FAN JETS

Greg,

The clamp I made is identical to the one shown in my post. You can buy it online from BVM. See this link;

http://www.bvmjets.com/df_power/exhaust.htm

Cheers,

mafrasca.

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Old 01-08-2007, 07:29 AM
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Default RE: DUCTED FAN JETS

Scropio said
"To me, power using a .46 would be marginal"


You would be very surprised how well a .46 size ducted fan model will go.
My Thorpe F20 with a picco 45 and thorjet fan is very good and speed in the air is impressive, if you can keep the weight around 9lb this combination works well and I have heard that with later OS46df engine vertical performance is unlimited.

Dont know personally how the turbax unit compairs but, I know that the thorpes used a lot of these origionally but found the fan unit they developed produced more thrust.

I have just got my hands on a OPS45DF +pipe + thorjet fan on ebay and looking for a home for it !

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Old 01-08-2007, 08:08 AM
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Default RE: DUCTED FAN JETS

The Tubax body is not large enough to support the Rossi. Jet Hanger did make a Turbax III for the larger engines. Call them they may still have them.

As for DF kits, I believe Jet Hanger is still making them. Thorp, JD Enterprises, DCU, Century Jets and DL Aeromodeles are good places to look as well. I don't think you will find and company who will produce these kits using modern ARF technology unless the plane can be made to handle an electric source and/or turbine. The market is too small and the customers are too fickle.

The OS 91 should last as long as any other IC engine if you take care of it. Due to the high performance nature, if you over-rev or have a lean run, it may not survive. I break mine in in the plane. When they hold an idle, they go up. I have never had an OS fail for anything other than a dead plug, no fuel or a set-up error.


Mark
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Old 01-08-2007, 09:06 AM
  #49
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Default RE: DUCTED FAN JETS

Well let's see how much use I can be.

TGA is gone. Steve's number is 815-433-6132 but I've been trying him for over a year and I still haven't gotten anyone to answer. Terry Holsten, whose here on RCU was a rep and has been VERY helpful to me. You might ask for his help. I was told to call Steve before 10:00AM but I was never told which time zone.

Larry at JHH can answer any question you have about the Turbax or Turbax III unit. It is too small for a Rossi .91 or a K&B 1.00, I tried both in the past and they didn't fit together, nothing beats experience even when it's bad experience.

I have switched to OS 91's and I agree with MMALLORY that I've yet to have one fail. Not even on a plug. I use Dynamax fans (a few Byron's in my TGA jets) with my OS Engines. I use a different brake-in procedure but basically agree, once it idles it flys.

I hope this helps a little.
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Old 01-08-2007, 09:09 AM
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Default RE: DUCTED FAN JETS

Gents, if I may add my 2 cents. I had flown ducted fan for many years (since 1988) and have been through quite a learning curve. I have transitioned to turbines; however, miss the many jet flyers that were in the hobby since the price of turbines has eliminated the common sense pricing of the ducted fans. Personally, I have been thinking of reverting back to Ducted Fan.

On the subject of breaking in the OS-91. I believe the secret here is the fuel. I use a fuel with 22% oil. With the RPM's of these engines reaching 23,000 RPM, oil becomes your friend. We have access to Ritches Brew 10% nitro, 11 / 11 oil (22%). Which means 11% synthetic - 11% caster oil. The price is right at $10.00 a gallon. I run the engine rich for the first few flights and break the engine in while in flight.

I would also recommend using an "in flight" needle valve sold by Jet Model Products or BVM. You can richen or lean your engine out in flight using a spare channel / servo on your radio. The secret here is to look for a good exhaust trail from your plane while in flight. If the exhaust trail gets too thin while in flight, simply adjust your servo controlled "in flight" needle to richen up the engine.

On the subject of Fan Units, Jet Hangar hobbies offers the Turbax I for .46 DF engines. For the .65 to .82 DF engine I would recommend the Jet Model Products Dynamax unit or BVM Viojet. The .91 DF engine I would primarily recommend the Ramtec fan unit and secondly the Dynamax unit or BVM viojet. The reason for the Ramtec over the Dynamax / Viojet is due to the transitional design of the units. The Ramtec fan blade pitch was designed to be used with the .91 engine. It properly loads the engine to limit the RPMs while producing more thrust than the Dynamax / Viojet units. The Dynamax and Viojet units were designed when the smaller DF engines were available (i.e., the .65 to .82 size DF engines). Just from experience, I can note that the Dynamax and Viojet units require the .91 to turn at 22,500 to 23,000 RPM to product the same amount of thrust of the RAMTEC running at 21,500 RPM. In short, you will have fewer problems with your engine self destructing due to the stress of the higher RPMs required by the Dynamax or Viojet. Once again, this is my opinion based on using all three types of fan units.

Hope this helps!
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