hi there, this is a project which I have been working on. It began as a feasibility study to see if it is possible to drive a scale model Bluebird with a ducted fan. As people were saying, the air intake required for the fan to perform at 100% and larger than the ones available on the scale Bluebird. That is why you see on certain videos and in model magazines, a stand-off style Bluebird, with a very large/over scaled air intake.

So, this was my assignment. I achieved it - I would say by 97%.

I overcame the airflow intake problem by manufacturing the canopy from some aluminium mesh and also either side of the canopy on the deck there are 2 openings which are covered in mesh. This seems to give me sufficient airflow for the fan. The fan is 80 mm diameter running on 22 volts and the model is 1/8 scale. It has been clocked by the satellite GPS (which is fitted onboard) at 31 mph which is quite acceptable in my books.

John

To begin with I used several sets of drawings.

I purchased a CD from a well known site on the web - containing the original drawings of Bluebird (as she was built). Also a few modifications to her.

I purchased a set of plans from the old MAP site; these were of her final disguise.

Then there were several books which I used for reference, which I will list further on for anyone interested.

The materials used for Bluebird model consist of 2mm lite ply and also balsa wood. Obechi strip used for the majority of the planking. She is also coated in purely 4 coats of Z-Poxy finishing resin.

First thing I did was make myself a true and flat building board to work from.

I made loads of little plywood clamps so I could clamp the base of the hull which is 2mm lite ply flat to the building board.

I didnt want the bottom to distort in any way. Then, I added the 2 internal keel frames which I glued in 90 degrees to the hull bottom. Then I started adding the frame ribs. Not once removing the model from the building board, it had to be kept flat and true.

The next thing I did was to plank the internal thrust tube and this gave the hull immense rigidity because it is made in place and glued through the frames.

The fan: Electric ducted fan and speed controller

This is of an 80 mm internal diameter. 12 blades. Producing (so they say) just under 7 lb of thrust. Running on 22 volts. The speed controller is 120 amp capacity - 24 volt. This is, bearing in mind, all new to me (new territory that is).

Couple of things for anyone new to the ducted fans which I learnt was - what you suck in the front - you can only push out the back of the fan that is 🤓 . The air is not expanded into a gas as in a real jet engine.

The other thing is you can reach (what they would class as a terminal velocity) where if you are lucky enough the fan will be travelling at the same speed as the air it is pulling in. You have to think about this one a bit - as the fan cannot go faster than the air it is pulling in.

We will leave it at that for a moment.

Couple of pics.

Oh, this is a picture of where the servo is mounted for the rudder and it drives the rudder through an aircraft snake.

John