Does anyone have an experience with 1/2A ducted fan jets?

I've started a kit that should be fun with a little bit of experimentation and imagination, and still at the point where I'm not really sure what kind of luck I am going to have getting it to fly.

There are many appealing aspects of the kit. It is a 25" Douglas F4D-1 Skyray that uses the traditional Stick & Tissue building methods. There is less than 20 dollars involved with the balsa, glue and covering. Its small size allows it to be carried in the trunk of the car, and the support equipment and fuel cost is minimal.

The plans state a 11oz Free-Flight weight with 250 sq in of wing area, but with carefull building and the weight of the newer micro-system radios of today, no more than three ounces need to be added to it to make it fully proportional. At a predicted 14 ounce flying weight, which is on the light side for 1/2A's, the delta should fly and handle well. The elevator mixing and fully symetrical wing profile with no dihiedral should make it a fast flyer also.

Since there is no currently available 1/2A DF kits to swap parts with, I am finding it difficult to find an impeller that would be suitable for it. Luck has been with me though, finding a couple of out-of-production Veron plastic impellers that have the same diameter as the original aluminum blade, but it has more blades and higher pitch.

This has me concerned about the ability of the Cox TD .049 (LH) to turn it at the proper rpm, but at this point it is about my only choice of impeller. If the blade doesn't work well with the ship, I will be forced trying to convert an electric blade to gas and starting over from there.

With this post, I am hoping others have had experience with 1/2A power, impellers and design to help direct me through the project. Designing or building ideas from others would be fantastic!

I'm hoping others will find this project interesting and show thier support in 1/2A ducted fans! The small expense and fun building can't be beat at this point for me Getting one to fly will be just icing on the cake!

I thought about that, but it can get expensive with a good charger and several battery packs to keep it in the air throughout the day, and the wing loading would be much higher.

I think staying with an .049 is the way to go. Light (1.5oz), inexpensive ($50), and 12 minutes of flight time on one fluid ounce of fuel sounds pretty appealing to me. A tuned pipe (worth the weight in performance and sound) directed through the ship can keep things pretty clean, too.

In my first thread for the 1/2A topic, I mentioned there were a lack of impeller options available to suit the Skyray 1/2A kit that I'm working with.

After brousing through a few web pages, I think I have found an impeller that is currently produced that will work. It will require a minimum of modification to bolt up to a TD, and has the correct diameter for the design.

If the impeller has the proper amount of blade area and pitch, I am in luck. I will have to see how it performs after testing the out-of-production Veron blade from England that I will try out first.

The company's name is WeMoTec, and they are based in Germany. The unit that uses the blade is thier version called the "Midi Fan". It has a diameter of 92mm (approx. 3.5"), and is designed for electric use.

A simple rework will have to be performed to remove the motor shaft stem from the inside of the hub, and it should bolt up and balance quite easily after that. It is made of glass filled nylon, which should stay fuel-proof also.

They also sell the rotor and spinner seperate, saving a bit of money by not having to buy the entire unit, and then using only half of it for the project. The U.S. distributor is Electric Jet Factory for WeMoTec. Could a ROG Skyray be in the air soon?..................

Hello,
You stated that you were building from a kit, but you didn't specify the manufacturer. Is it one of the guillow kits, or somebody elses kit? I seem to remember a 1/2A ducted fan warthog from RCM several years back. The builder used two cox td's, and cut two cox propellers down to a diameter of 3.5", then connected them together somehow, and ran the TD's with those. Nowadays, though, wemotec seems a good option. Good luck.
Kurt

I remember that article with the A-10 and the two cut props. They suggested stacking them together. I thought that would have been kinda hard on the motors if you didn't run a bushing through them to make them a set pair, and/or key them together and also reducing the hub thickness for better balance. Machining out a key into each hub to lock them together, bushed, reamed and balanced. Then you'r left with a possibly a weak blade after all anyway. But, it might have a place if things don't fan out.

Here's the specs on the kit I'm tracing:

Berkeley Models Inc.
Douglas F4D-1 Skyray
Manufactured: 1957
Scale: 3/4" = 1'
Wingspan: 24"
Free-Flight Wt: 10-1/2 oz.
Effective Wing Area: 250 sq. in.
OK Cub .049S or Cox .049 Thermal Hopper (shown)

Box reads: "First kit model with internal ducted fan to produce jet power. Henry Struck has been experimenting and testing this type of propulsion for the past five years, - resulting in this highly refined ducted fan design, developing six ounces of static thrust, - ample power for free-flight or controline. Out-of-sight flights were common on original. Landing gear optional."

The kit came with full-sized plans, die-cut and shaped balsa parts (nice cutting), die-cut white cardboard forms for the inner and outer thrust tubes, waterslide decals, vacu-formed canopy, nose and inner thrust tube cap, covering (00 Silkspan), brass screw package and ready-to-install metal propulsion fan.

It is scaled down very well, with lots of .020" sheeting (fuselage and leading edges) The thrust tube build up is interesting also, with an inner thrust tube supported by six curved straightening vanes by the impeller, and four at the outlet. I believe there are three other D/F's in Berkeley's series, an .049 F8U Crusader, .020 Tigershark, and an .049 Tenco.

Not a bad kit, and now that servo weights are under 0.3 ounces it could be easily converted, from the designed free-flight or Stanzel's Monoline control unit, into a two microservo elevon mix no problem, or maybe even up to four with rudder and throttle, or the new lightweight parkflyer retracts...

Keeping the kit as close to its originial condition, copying the kit is what I had in mind. It can almost be done by using a copy of the drawing for tracings, but difficult. There would have to be a few areas drawn out by the builder.

The Veron kit that you built sounds interesting, as I was unaware that Veron made more than just impellers (say, ahh...still have the plans? ) I never heard of the company until the search for a modern blade for the build made one turn up. The two that I was able to purchase (out of buisness I believe) are going to be tested in the plane.

They are both a Type "C" (.061, but this was before TD's I'm pretty sure) and 3.625" in diameter - same as original but has more blades and pitch.

If I can't get the revs out of a stock one, I might try narrowing the blade width, and saving the other one to try out on a Norvel .061, but that would take some re-engineering for the tractor set-up so I'm saving it. Currently manufactured impellers for this size engine and duct are hard to find. I'm wondering if I am looking past them, like in a dustbuster unit or something like it that I could take apart or order a replacement part and adapt it.

The Skyray kit as mentioned was designed orignally for FF or Stanzel's Monoline set-up. The FF version has seperate ailerons, and rudder.

With my plans of converting it to R/C, using a two-channel / two-servo mixed set-up, will a rudder be necessary for turning?

I'm trying to stay as light as possible the first time around, and want to stay with only two servos if possible.

I included this post to provide anyone that shares an intrest in the kit that I am tracing out.

The kit is very close to these outlines, and very few concessions were made to allow the fan to work efficiently (cheater hole on bottom of plane)

Jetpack,
In 1980 I built a Midwest A-4 Skyhawk( foam fuse and built up wing)-it flew pretty good on just 2 channels(aie@elv)-it was bungee launched-had a midwest .049 fan with a TD .051 for power-it flew about 50mph.I think Bob Kress built the fan.


Jackjet

I used to play all kinds of games with stacking props on .049's. Its not hard, and works amazingly well. One very successful stacked set was 2 of the 3-blade props simulating 6 blades, with just 3/4 inch clipped from each blade. (I think those were 5 inch dia props... the stock Cox 3-blade from the mid 1970's, they only had one.)

There's no keying or anything really needed. Just rough the two prop hubs a bit with sandpaper and put them on a long screw shaft. They stick n alignment quite well even using the Cox Spring starter or an R/C car motor converted to act as a 1/2 A starter.

If it were only that easy to make up a home-brew fan for a .40.... but the shafts aren't long enough.

Hello.
I am looking for a ducted fan engine, and I found the MidWest RK Fan an excellent model.
I would need to buy it. I have airplane(parts), with foam wings, that I want to transform in a jet plane.
I am a beginner, I am 14 years old[img]i/expressions/face-icon-small-smile.gif[/img]. I have a lot of parts to trade for that ducted fan. I have a cox .049 engine without carburetor, with fuel tank, prop installed, a lot of other things(spinners, fuel tanks, props, etc).
If you want to trade with me, please contact me at [email protected] .
Thanks a lot. Hope you can help me.
Sincerely, Florin

I am looking for one of those midwest a-4 skyhawk kits if anyone knows about one available.

There was a stand way off scale F16 (kind of box shaped fuselage and flat bottom wing) set of plans that I used to build the jet with an RK049 fan and TD .051. It barely flew like most little fan jets of the era. This was 1980 or so. I wish that I still had the plans. It could have made a good EDF project today. As I think about it, the plans may have been from a project in one of the magazines. Does anyone out there remember this plane?

There is a new almost 1/2 A ducted fan with motor in the Kamdex Mig-15 that Tower is importing from Taiwan. The motor is a hot A class .061 and it is reputed to work very well with the Kamdax fan unit, with none of the tedious building and setting up of the Midwest RK.049 fan.

The kit with fan, motor, landing gear and hardware seems a little pricey at 250, but I looked inside one and it actually included a fueler and a custom offset electric starter. It was pretty well done and the model is also said to fly well. The assembled fan unit and motor is a little bit high at 200, but if it works, it is worth it, IMHO.

Also, you can buy the complete MiG airframe in parts from Tower for a 50-60 bucks. allowing you to create a Mig-15 for experiments with your own 1/2 A ducted fan unit.

[link]http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXFAT7&P=7[/link]