Interstate L-6 (oz2555)


Interstate L-6 (oz2555) by John Watters 1986 - plan thumbnail

About this Plan

Interstate L-6 Grasshopper. Scale rubber model utility aircraft. The "L-6" was the US Army designation for the S-1B1 Interstate Cadet, and 250 were built.

Update 18/12/2020: Added article, thanks to algy2.

Quote: "Interstate L-6. Try a spot of Rubber Scale. Build John Watters' 27 inch (3/4in : 1 ft) replica of this little known US trainer. Full-size plans overleaf; comprehensive instructions below .

IN GENERAL CONVERSATION with a colleague of mine, who knew that I was interested in model aircraft, and for that matter most things aeronautical, he mentioned that he had the first three volumes of Aircraft of the Fighting Powers 'originals' and would I like to look at them - obviously the answer was yes.

Although I have quite a comprehensive amount of literature on both full size aircraft and models, I must admit that I had never seen any copies of these books - let alone owned any. True to his word he brought them for me to look at. After a few attempts to 'cross his palm with silver', to lever the volumes away from him (I must admit I would not have parted with them either), I was reduced to relying on the trusty Xerox copying machine to add the more interesting information to my collection.

One of the many new (to me anyway) aircraft within these volumes that looked right for modelling was the Interstate L-6. This aircraft gets its designation from being the sixth light liaison aircraft. The full size machine started life as the Interstate Cadet; and was modified to the L-6 by enlarging the cabin area, and glazing in particular. This was to allow for the addition of a 'map table'.

After studying the L-6, it seemed most appropriate to design it for rubber power (with a few necessary modifications). One thing it does have in its favour, for rubber power anyway, is its reasonably long undercarriage legs. This allows for a good propeller diameter with some ground clearance, without having to exaggerate the undercarriage.

Tailplane and Fin: The enlarged tailplane area is the only deviation from true scale outline. Due to the rather 'curvy' outline of the fin and tailplane, and its flat plate section, a laminated outline seemed to be the best type of construction. To anyone who has not tried a laminated construction before it may look difficult, but once mastered it really isn't. Excellent stiffness for little weight is the main advantage.

First mark out onto either a piece of 1/16in medium balsa sheet or card the whole of the inner profile of the tailplane. Cut out the shape and with a candle rub the edges of the template until it has a thin coating of wax. Run a piece of string around the outside of the template and measure the length, which will be that of the balsa strips you will need.

For the laminates themselves, cut strips of 1/16 wide balsa from 1/32 medium sheet. Make the strips longer than actually required, and cut a few more than you need, just in case you break one. The template can now be pinned down onto your building board. Before the strips are wrapped around the template, they should be softened. This you can do either by soaking them in water, or use good old saliva, ie run the strips through your lips a few times.

Position the first strip (still wet) against the edge of the template and pin it in place. Now with a firm continuous motion, wrap the strip around the template, pulling gently. The strip can be held against the template by scraps of balsa pinned against the strip. The next and any further strips are added in the same manner, but one face of the strip should be smeared with PVA glue. The small retaining scraps are removed and repositioned each time a strip is added.

After building up the outline of the required thickness, and allowing it to set thoroughly, sand the structure smooth Whilst it is still on the template. Lastly, remove the outline from the template and trim to length. Now pin the outline down over the plan and build up the inside structure from the 1/16 sq cross pieces. Finally remove the completed part from the plan and lightly sand smooth.

The above construction method can be used equally well for the fin and wing tips. If on the other hand it all seems too much, the outlines can be made up from sheet pieces - but is is recommended that you laminate!

Fuselage: Begin by building up one side frame to the shaded outline. Select medium stiff strips for the top and bottom longerons. The remaining spacers can be from lighter balsa. I used a PVA glue for all the 'balsa to balsa' joints.

Use whichever method you prefer for building up the second side (building the two frames one on top of the other will give you the best results). Now with both sides completed, glue formers F4 and F5 into position on one side frame. You will probably find it best to check the correct alignment of these formers by positioning the side frame over the plan view. The second side can now be added..."

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Interstate L-6 (oz2555) by John Watters 1986 - model pic


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User comments

I built this model in 1986 and powered her with a CO2 motor. She flew very well on calm summer evenings, a joy to behold. Regular 2 minute flights and I did not know how to trim at that time. Straight off the building board. What a beaut. Will download the plan but power by rubber this time because CO2 was a bit unreliable.
MalcolmJ - 10/08/2016
Hello Mary, I am attaching some photos of the L6 Interstate build so far [more pics 003-009]. I put the plan through GIMP using Ubuntu and overlayed a 1/2 inch grid to make alignment easier. I have been using Posterazor for a few years now to print out large plans such as the Junior 60 and found that a 1" grid made alignment of the various sheets very simple, and also only printed out the wings, fuz and tail etc as separate items. Trying to stick the different parts together as one large plan always lead to parts not lining up correctly, and who wants one massive plan to try laying out to build from? Hope I have have the L6 finished before all this good weather disappears. Best regards
MalcolmJ - 06/09/2016
I had just built the tail plane and fin assembly for the L6 when it all started warping, just as it did when I built my first L6 in 1986. I remember that I kept the tail assembly permanently in a jig to try to keep it straight. This time I sanded some 3mm depron down to 1/16" and made the tail assembly out of this and covered it with coloured packing tape. Been 4 days now and no warps showing up. Photo attached [more pics 010]. Just got to make the wheels and she will be ready for test flying.
MalcolmJ - 09/09/2016
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