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                Blackhorse 85” Span ARTF D.H. Chipmunk

                                                                     By Alan Glover


      I bought this model several weeks prior to the Traplet scale comp. that we held at our Halsall site in May. The intention was that it should replace my ageing Fairchild PT19 which had given sterling service but was getting a little tired and ready for a rest/retirement. As things turned out the PT19 was retired earlier than expected [and permanently] due to a duff Rx battery at that event but that’s another story! Anyhow on with the tale;

        The model arrived packed in a huge cardboard box, [a large car is needed even to get this home never mind getting the completed model to the flying field] and even on first impressions seems to be of very good quality [the model not the box!]. ARTFs really have come on in leaps and bounds over the last few years, and although they won’t ever replace the pleasure of building your own they do serve a useful purpose.

        Just on the subject of the packaging I decided to ‘go green’ and recycle the box, and by the addition of a few strategically placed cut outs and a bit of glass cloth and resin managed to convert it into a reasonable model transporting cradle to keep it from harm during car journeys to and from the flying field.

        Back to the model. It comes as several large, pre covered components. These are; fuselage, wings, tail surfaces and control surfaces [all of built up construction covered in Oracover which is a covering not unlike solarfilm but which seems to be much tougher], a fibreglass engine cowling, ABS moulded undercarriage fairings, a large bag of hardware/metal fittings etc., sprung oleo u/c legs, wheels, fuel tank, spinner and a large [although pretty useless] decal sheet. The bits you will need to finish are; radio gear [8 x servos], engine and material for decals if you decide, as I did, to junk those in the kit.

The basic airframe components are finished in RAF training colours of red, white, black and grey. One nice touch is that the whole of the cockpit area is a one piece removeable unit which includes pre installed aircrew and instrument panels. This whole unit is held in place by plywood tongues at the front and 2 x plastic screws at the rear. When removed a large area of internal fuselage is opened up giving superb access to the radio, servo and fuel tank bays. As the wings are of the plug in type the removal of the cockpit area is also necessary to fit/remove the wing panels to the fuz. This system would also be useful for anyone who wished to power the model by electric as it would afford easy access to the flight pack between flights for battery changes/charges etc.

        The model is advertised as being suitable for 45’ish cc petrol engines. I thought this was a bit OTT so decided to set it up for 4 stroke glow power of around 120 – 180’ish power as I had an ASP 180 sat doing nothing. I decided that I would follow, to the letter, the excellent assembly instructions, every stage being accompanied by photographs.

      The build [or perhaps assembly would be more appropriate] starts with the wing panels. 1st job is to glue the ailerons and flaps to each wing panel using superglue on the fury fibre type pre installed hinges. This is followed by the fitting of the servo’s [one for each aileron and flap, 4 in total] into each of the pre cut and installed servo bays. The next job is to fit the control horns and linkages, again supplied in the kit. The pre drilled ‘hard points’ for these are already installed in the control surfaces so again it’s a pretty fool proof system. The final job with the wings is the installation of the undercarriage legs and ABS fairings which follow the old tried and tested method of securing with saddle clamps to hard points just forward of the wing main spar. Fitting the wheels pretty much concludes the assembling of the wings, and the whole thing can probably be done in not much more time than it took me to describe.

 

                Following the assembly sequence in the instruction manual the next job is to install the engine mount and fuel tank. As the recommended engine is petrol the instructions go down the route of explaining the fitting of such an engine direct to the firewall via the usual radial mount. Because I had decided to go the route of a 4 stroke glow engine I purchased and fitted a commercial mount of the appropriate size. You’ve all done this before so no egg sucking lessons here! One word of caution though, if you choose to go down this route be advised that the supplied fuel tank is also for petrol so will need to be changed or modified to a methanol friendly one. The actual fitting of the engine is fairly straight forward, the only concerns being that its prop shaft is centred on the cowling and that the prop drive protrudes 175mm from the firewall in order that the spinner clears the cowling. Following the fitting of the throttle servo and linkage the next job is to fit the cowling itself. I made several modifications here. The first was to glass cloth a thin ply baffle inside the cowl to drive incoming air directly over the cooling fins of the engine [I’ve yet to have an engine run too cold!]. The reason for this is that the full size Chipmunk engine turns clockwise when viewed from the front driving cooling air from the propeller directly into the offset intake and over the engine cylinder cooling fins, whereas our model engines run anti-clockwise. This may not appear to be a problem but as our model engines run in the reverse direction to the full size this places the cowl air cooling intakes on the wrong side for efficient cooling airflow over the cylinder. Next was the cut out for the exhaust system. In order to avoid any unsightly lumps of exhaust sticking out of the cowling sides I have replaced the ASP supplied exhaust manifold with a stubby 90 deg. item purchased from just engines. This allows the exhaust to exit directly under the centre of the cowl whilst still using the stock ASP silencer. The final mod was to glass cloth thin metal strips inside the cowl at the screw fixing points to hopefully avoid the holes wearing oversize due to engine vibration etc. To finish the job off I installed a Du Bro fuel filler valve and a remote glow connector, both accessed through holes cut into the cowling at the appropriate points, just to make life easier and the finished item a bit tidier at the field.

                Next job is the fitting of the elevators to the tail plane [or horizontal stabiliser as our trans-atlantic cousins would have you believe]. This basically follows the same procedure as the ailerons, again each being driven by a pushrod from fuselage mounted servos. The whole unit is then glued firmly to the fuselage. The rudder uses quite a clever and tidy control system. It is driven from a control horn which is attached to and drives the steerable tail wheel via a servo operated pushrod. The whole thing is fixed inside the fuselage. The top of the wire on which the tail wheel fits is a length of piano wire which protrudes up from the fuz. to just behind the tail fin. This is then bent rearwards through 90 degrees and cut to a suitable length. When the rudder is fitted it is this wire, inserted about 2” into the rudder, which drives it via the tail wheel crank. The big advantage is that the whole assembly is the tucked away inside the rear fuselage. The downside to this is that you must get your angles right or the rudder and tail wheel will always be at different angles and fighting each other. Apart from a few bits of ABS trim to improve the scale appearance that is pretty much it.

 

As mentioned earlier you do get a sheet of decals with the model but these are so unlike anything I have ever seen that I decided to junk them and make my own from a combination of solar trim and letter-a-set with a lacquer sealant where required, and if I say so myself I think they do look better than those supplied!

 

            I have installed my 180 ASP married to an 18” x 6” Master Airscrew prop as at 85” span this is no park flyer. However on completing the model and putting it on the scales it has come out at a shade under 14lbs ready to go less fuel, and at that balances spot on the recommended C of G position without any additional weight so the 180 may be more than is required.

          I have included a couple of photo’s of the completed model which, although no Nats winner is I think, enough of a Chipmunk not to be mistaken for anything else.

    

 

Flying;

            The test flight was made at Aughton on Friday 24th July on a fine and sunny but rather breezy day. The model flew better than I dared expect right from the first take off. Very smooth and due to the weight I was able to keep the speed down to a realistic level with no stalling fears at all. The take off was made at about 50% throttle, confirming my suspicions that the 180 is probably more power than needed. Loops, rolls, reversals, Imelemans etc. are all possible on not much more than ½ throttle. In fact this leads me to suspect that the one problem I will have is that the model will be difficult to slow down enough for the low throttle manoeuvres such as spinning, descending circles etc. With flaps deployed even on tick over the model does not want to lose any height, so much so that I could not use them for the landing. For this reason I will probably replace the 180 with my 120 [taken from the aforementioned PT19] for what should hopefully be a more realistic power to weight ratio.

 

Latest Update;

            Following the fitting of the 120 engine [which will turn a 16"x6" prop at 8,000 rpm] the model has been re flown and now displays far better flying characteristics. It can be slowed down to realistic flying speeds, yet still has more than enough power for any manoeuvre that a full sized Chipmunk would be capable of. The shift in C of G resulting from the fitting of the smaller engine is so minor as to have had no discernable effect on the flying of the model. The overall result from this alteration is that the model is now far more pleasant to fly than it was originally when so overpowered.

            I took it to this years Nationals and flew it in the flying only class. As you may be aware the weather was pretty dreadful but the model coped with winds gusting up to 23 - 24 m.p.h. with enough power to retain control. Not pleasant but 'do-able'.

            Anyone thinking of buying one and flying it on petrol would, in my opinion, be advised to stick to something in the 25cc area as anything more would be far too much power. Bear in mind though that a petrol engine is likely to be heavier than my 120 and so the appropriate C of G checks will be required. Alan.

  
 

                                Super Scale Model
                              Feisler Storch by Gary Protheroe

         

‘Here are 4 photos. Two are of the full size in the French Alps that I have modelled my Storch on. The other two are of my model. One shows it in a side view taken at Burscough Airfield. Or as it is known Ringtail Aerodrome the home of the Seafires. The other is a shot with the wings folded.

            

The folding of the wings was probably the most difficult part of the build. The geometry looks simple, but it rotates and swivels upwards at the trailing edge and has to miss the gun canopy. I almost gave up on three occasions, but with the support of people like Andy and the rest of the team and their encouragement I soldiered on and I think it was successful. I believe it is the first model of the Storch to have folding wings. The guy that drew the plans (Top Gun) Ed Newman (U.S.A.) also seems to think so. I have to give credit to George Swallow for turning up a couple of the pivot forks. I even had to make the lower pivot ball joints, which had to be in steel to take the loading. The front pins are 2mm steel threaded with a fine thread hopefully will not come undone in flight and will take the sheer loads. Particularly on my landings! The cabin structure is silver soldered tubular frame as per the full size. The undercarriage struts are just sprung at the moment, but will probably change then to soft spring high damped struts later.

It was at one of the Traplet competitions with my old Storch built in 1980 when I met another Storch fanatic who had also been in contact with another 'Storcher' and all three of us were building 1/5th scale Storches. I know it doesn't sound very big but the full size is 49 feet wingspan! I have scale propellers and after test flights with a standard prop I hope to fly it on a scale propeller. The full size is a wide bladed prop so that on a STOL landing you are supposed to put the nose down 40 degrees with 40 degrees of flap and with the engine on idle the prop is supposed to act as a brake and maintain slow speed. We shall see!! Well that's the theory.

The engine is a Laser 200 V twin four Stroke which sits just right in the cowl. Well is there any other engine I would have put in my scale models! Ha! Ha! (Alright I know some of you only like petrol. What I say each to his own, but Lasers are better!)

Contrary to belief the pilot and passenger are not Thunderbird figures as was suggested by:- " No Names". The pilot is Lieutenant Herr Protheroe and the passenger is Herr Major Hartmann being transported to his ME 109 squadron, hence the green heart and shield.

The model now has the fuselage lettering and it is hoped that in April it will be in a photo shoot at Old Warden with the other two Storchers against the fully restored full size down there, and all three are hopefully going to be at Cosford for the LMA 'Big One'.

I will try and give you more detail on the build later in the year.

 

Gary.