Christchurch and District Model Flying Club

Piper L4 Grasshopper by Ken Spokes

The story so far: Ken has resurrected a 1/4 Scale Piper Cub and is converting it to electric power and the L4 military version.

The engine cowl I  purchased with the plan was a fibreglass moulding that fitted an inch or so over the front end of the plane. It was quite smooth with just one hole for the prop shaft and as it turned out, this was in the wrong place. Now the cowl on the Piper is made up of a number of sections which are either riveted together or secured by wire clips. Quite distinct lines are visible where these overlap and to get this effect, I tried a technique that I had read about years ago in one of the scale magazines. This involved placing several layers of masking tape ( which had been cut through to get a sharp edge ) along the line of overlap. Two- part epoxy filler is then knifed over and away from the masking tape edge feathering out for about an inch or so depending on the scale of things. When the filler is set , a block sander is used to remove the excess down to the masking tape and to smooth into the original base.When the tape is removed, a nice sharp edge is revealed to simulate the overlap.I found the operation quick and easy and the end result really brought the cowl to life.

The next step was to cut out a number of holes for the dummy engine, exhaust pipes, and air coolers  and to make a radiator which could be removed when flying to allow a good air flow over the controller which  will no doubt get quite hot.

The engine fitted to the Piper was usually a Lycoming or a Continental four cylinder and as I have scale drawings for the latter, this is the one I will build. .As it is aircooled, most of the engine sticks out of the cowl into the airstream and is very visible which unfortunately, means quite a lot of detail needs to be included if it is to look anything like. I searched around to see if something was commercially available which could be used but unfortunately no joy..So, it means a scratch built job with a lot of boring repetition work for things like cooling fins, rocker covers, exhaust and induction pipes for each of the four cylinders.

 Later. Work on the dummy engine is going well although it is more time-consuming than I had first thought .Construction is fabricated out of balsa and 1/64" ply with the parts for each cylinder mounted on a short length of 1" dural tubing which in turn are secured to a ply plate just inside the cowl opening.  3/8" dowel seems just the right size for the exhaust pipes with the bends made out of balsa and epoxy filler. The welded joints are formed by pieces of thin string wound round plus plenty of white glue. The large air scoops on each side of the cowl are made out of 1/64 ply sheet steamed to shape.All these bits and pieces have now been put aside until I get the motor as I am still not 100% sure how the cowl will fit over it.

The undercarriage was made out of 6swg steel wire which took quite a bit of bashing into shape. These pieces plus all the anchor plates for the telescopic spreaders were firmly clamped in a jig and brazed together.Scale brake discs were machined out of dural stock. Fill -in between the wires is balsa and ply which eventually will be covered in matching Solartex. A pair of Dubro scale Goodyear treaded tyres finished the job off. The steel wires lock into hardwood slots built into the fusalage and are secured in position by four mild steel plates, the rear plates doubling up as anchor points for the wing struts.

.I have made a start detailing the cabin.The instrument panel has been completed using parts from a J'TEC scale instrument kit and as there are only five instruments, it was a fairly quick job. I had quite a search for a photo of an original L4 panel as many of the planes that are around today are fitted with modern instruments.The panel was enhanced with pin heads representing fixing screws and additional surrounds for the ASI and altimeter. To finish, it was spayed matt black. Cabin access is through a two- part door/window. The bottom door part hinges down and rests on the strut while the top window hinges up and clips to the underside of the wing. I have made the door part hollow and installed a handle on the cabin side that operates pins.at each end to lock it closed. I have still to figure out how to lock the window down.

Time to get the motor. As usual these days, I searched the web for the best deals Most of the UK suppliers were quoting prices within a few pounds of each other but looking further afield, I noticed that prices in the USA were significantly cheaper and not only that , they offered combo deals for both motor and speed controller. I have heard of people buying model goods from America but never had the courage to try it myself. However, with $/£ exchange rate so much in our favour at the present time, I found I would be making a saving of over £85 and that included postage  HOBBY LOBBY seemed  the best supplier, so with some trepidation, I made out the order on line, clicked “buy" and waited for something to go wrong. With my luck, I thought it would probably get lost or I would be faced with a big Customs bill. But no. After six days, my goodies arrived in a well packaged box designated "Toy Motor". Seems a good way to go if you are thinking of buying some pricey gear.Compared to the smaller Axis I have been using, this one seemed huge and I immediately had more misgivings about it fitting in the cowl. Luckily, it did but only after I had extended the prop shaft by machining a 3/16" dural spacer. As this motor would be developing well over two HP, a good solid mounting was required which I fabricated from quality three ply with castellated joints for added strength. This also incorporated cooling ducts for both the motor and controller with an exit on the underside of the fuselage just ahead of the U/C. I have also built in a cooling duct on the inside of the cowl to take air to the motor from the Heater Intake, the Carburettor and the Cooling Air inlets which I had cut earlier. Fingers crossed, this will be adequate. All the bits and pieces inside the cowl have been fixed in position using a hot glue gun which gives a really solid bond,

The wing structures have been completed apart from fitting the servos. which I intent fitting outboard positioned at each aileron mid point. As the leads will be over 30" to each one, filters will be fitted just before connection to the receiver to eliminate possible interference.

To be continued.

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