John Rickett 102

Ok Richard, pleased to hear you are making progress. I’m not sure you’re correct about the stitching only being required on the rudder and elevators, here’s a picture of the fin which shows it’s stitched. It’s the clearest one I’ve found but most pictures look as if all but the leading edges were stitched. As you are basing your finish on a recently restored Gull, it’s appropriate to use pinked tapes if that’s how it was recovered, I wanted the Vega Gull to be as it left the works in 1936 which means it probably had plain tapes. If it helps, a useful source of small screws is Quicktest. If you are going to push them into drilled holes and are not concerned about a particular thread, they are a cheap source. They can be bought here.

Brian, You'll need some sharp scissors to cut it. While very good and ideal for our purposes, its extremely light and will drag, pulling the weave if not handled carefully.

For this model I thought I’d try a different method of simulated rib stitching. Previously I’d used Solartex for both the stitch carrier and the top tapes. I also wanted to know the likelihood of the aircraft having plain or pinked tapes. As far as I can tell, pinked tapes started to be used just prior to the 2nd world war, as this particular aircraft was produced in 1936 its likely that plain tapes were used. To my mind they are not as attractive as pinked tapes but plain tape wouldn't be inappropriate and they'd be considerably cheaper, in fact, free as I could cut my own. The idea was to use heavyweight tissue as the stitch carrier and polyester fabric for the top tapes. First an oversized piece of tissue was placed on a flat surface (an offcut of ply) which had been covered in parcel tape. The tissue was given a coat of thinned fabric cement to pre-shrink the tissue as well as create an adhesive surface. Thick cotton thread was dipped in the same thinned fabric cement and drawn through the fingers to remove the excess cement - this is a messy process but needs must in the pursuit of scale fidelity. The thread was wound over spaced nails (½” pitch, which equates to 2” at full scale) with the tissue underneath. Further fabric cement was brushed on to wet out the previous applications and firmly stick the thread to the tissue. Once dry, which only took a few minutes, the tissue was sliced up in ¼” widths. For interest, a ½” pitch was chosen based on an American standard (AC 43.13-1B) applicable to fabric coverings where original information is unknown. I couldn’t find a British standard and it may not have existed in 1936 anyway, so assumed there would be little if any difference between what the British and Americans had discovered through trial and error, and later adopted in a standard. The relevant page is shown below. On previous models I had doped the wings and tail parts after application of the tapes, but this time doped them first. Solartex has an impervious heat activated adhesive layer which can be ironed on but the new method required a sticky surface (once dissolved) to achieve the same adhesion, so all the fabric covered parts were doped (non-tautening dope) before beginning the rib stitching process. Each strip was then placed over a rib, with the strip inverted to put the stitch underneath the tissue. Well thinned fabric cement was applied to attach the tissue but think that dope would probably do the same job, if a little slower to dry. For the top tapes, offcuts of Koverall were given a coat of fabric cement, in a similar manner to the tissue and when dry, cut into ½” strips and again attached with more thinned fabric cement. The result is less bulky than using Solartex – tissue is thinner and plain Koverall doesn’t have the added adhesive and coloured layers, I was quite pleased with the effect. The truth will come out once the final finish is applied, just barely visible tapes but bold stitches is what I’d like to achieve.

Thank you Brian, I get most of my supplies from Bucks Composites. I've just checked the site though and the lightest advertised just now is 25g. You could try giving Graham a call to see if he's going to restock. There is an ebay seller here asking £12.15 for 5m of 18g - that seems a good price.

I was pleased with the lightweight fibreglass covering of the flap boxes undersides so covered each of the flaps in the same lightweight (19 gm) cloth. Prior to covering it was possible to twist the flaps if enough force was applied, but it takes far more torque to put any kind of twist in now. Brushing out the wrinkles during cloth application seemed to give a flat surface, though during the curing process some wrinkles would creep in again. All that could be done was to sand flat, apply patches where the cloth has been sanded away and then blend in – effective but time consuming. I’ve since discovered that its better, once the cloth has been completely wetted out, to tug at the edges as if to stretch the cloth, perhaps only a millimetre or so is gained but its sufficient to take out any invisible slack and prevent the wrinkles forming. Previously, my normal preference for covering a largeish model was fabric, especially if the original had been fabric covered. Having now experienced the strength, rigidity and minimal weight gain of really light glass cloth and resin, I think it’s the way to go in the future for those parts, like flaps or fully sheeted tails. The flaps on this model are sheeted in 3/32” balsa but I believe now I could have used 1/16” and achieved more than enough strength. Here a flap box has had a coat of resin brushed on, rubbed down with 180 grade wet & dry cloth (used wet) and then given a further coat of resin using the credit card squeegee technique. After allowing 2 days to cure, 400 grade wet & dry cloth soon produced a surface to which a coat of primer/filler could be applied. To further keep down the weight, the insides of the flaps and flap boxes will only be given a light coat of colour, if someone wants to try and peer into the flap recesses and find fault, that’s ok with me! All the control linkages have now been made up. In trying to keep with Edgar Percival’s quest for a clean design which minimises parasite drag, the flaps and elevator rods are internal. The elevator rod is 3mm, that’s a bit of weight right at the back where it’s not wanted, but with the length of the rod being 7” and the elevator area at about 112sq ins, I didn’t want the chance of flexing to occur. The flaps and aileron rods are 2mm, which I think is sufficient given their short lengths. None of this has any scientific basis but gives me peace of mind. Ignorance is bliss! The servo covers are sheet balsa covered either side with glass cloth. Rudder and tailwheel are both closed loop using 80lb rated, nylon covered fishing trace. The ferrules supplied are large so instead I’ve used 2mm od brass tube. By squeezing the tubes oval, two cables (0.75mm od) will go through the hole. The ferrules were then nipped with side cutters and a spot of thin cyano applied. The cables run in 2mm id plastic tube, using tube allows for the cables to be fitted once covering and painting is completed. The tops of the cabin doors and aft cockpit have single curvature windows, on the model the radius is about 1”. I thought at first that 0.5mm PETG clear sheet would easily follow the curve.…until I tried it, then found that there is a lot of spring in the material which would be difficult to hold while glue was setting but also that the spring probably would, over time, distort the doors. Another plan B was required. A phone call to Sarik confirmed they could vac form the windows if I provided suitable plugs. Their suggestion for ‘one-offs’ was for a plug to be formed from plywood, which had been coated with Upol Easy 1 or Isopon P38 filler sanded to a smooth finish. They further suggested that a plug should be raised a small amount above the finished height (a piece of wood fixed to the base) to allow for the fillet during pressing and that the sides should be bevelled slightly so that the formed sheet will release from the plug. Armed with their suggestions a couple of plugs were made. Its possible that on the real aircraft, the front and back curves are the same, but on the model they have come out slightly differently, it’s not a lot, but an unknown to me whether the formed shapes would readily adapt to a slightly different shape. If the curves had been the same just one plug would have been needed but I decided to play safe and make them handed. A DIY electric planer produced the rough shape which was then finished with an orbital sander. Here, the two plugs prior to coating with P38, are lined up with the doors. The coated, primed and sanded plugs. Its been reported by she who observes such things that all the surfaces in the kitchen have taken on a faint grey colour - who would have thought that P38 dust would travel far! In discovering how difficult it was to curve the side windows, I thought I had better check that the curved portion above the windscreen panels would accept the PETG sheet. The conclusion was - with difficulty, so the decision was made to make a plug for that part as well. The plugs are all ready for a coat of gloss paint, once the weather cooperates. Fortunately, the five panels which make up the front windscreen are completely flat so should be straightforward to glaze. As an aside, Percival introduced a blown curved windscreen later on, as fitted to the Proctor, though some owners didn’t like the visual distortion and had their aircraft retro fitted with the flat panels windscreen.

Richard, I've a box of A4 sheets, enough to last until I'm 999 which is unlikely, pm your address and I'll send you some. I must have had this box for 30 years and despite building many models in that time, have only worn out a few - they last forever. My thoughts are that tracing through using carbon paper will only introduce one error, whereas the pinprick method could introduce two, one if the pinpricks are not exactly in the centre of the line and another when the dots are lined up with the french curve. If you use, say, a red or green ball point pen, you can see on the plan all the lines that you've covered.

That's interesting Richard, why do you prefer the pin prick method instead of good old fashioned carbon paper?

Are you describing your old transmitter or the 16IZ? The manual I have for the 16IZ explains how to set flaperons and airbrakes on pages 130/131, its no different to the 16SZ.

Andy, I'm now confused, not that I want to indulge in small models carrying cameras, however when it comes to doing the RCC tests, this is what the BMFA currently says in its Article 16 authorisation: 5. Remote Pilot Requirements 5.1 Remote Pilot Competence It is a legal requirement that anyone who flies a model aircraft or drone outdoors with a take off mass 250gm or above, or that has a camera attached must have a CAA Flyer ID. Previously BMFA members who hold a valid BMFA Registration Competency Certificate (RCC), or a BMFA A or B Certificate passed before 31/12/2020, did not require a CAA Flyer ID. This has now changed and you will require a CAA Flyer ID. However the BMFA can request the Flyer ID on your behalf.

Thanks Brian, it was food for thought. I don't have any 1 ohm 1 watt resistors just now but do have some 0.47 ohm 3 watt so tried an experiment. To get a scientific (!) baseline the top wing was connected to a 7.4v lipo and the bottom to a 6.6v life battery. There is a noticeable difference to the eye although its not so obvious in the picture. To try to quantify the difference, I used a 35mm SLR camera with an exposure meter. The lipo powered lamp indicated 1/4000th at f8, the Life 1/2000th at f8. Clearly the exposure meter could detect the difference. I then connected both lamps in parallel and checked them with the lipo connected and with the resistors in series (near enough to 1 watt) this measured 1/5000 at f8. Measuring again without the resistors, showed 1/6000th at f8. From this I've deduced that inserting the resistors is similar to running on life batteries. I'll charge both the lipo and the life batteries, then tomorrow (its supposed to be dry and sunny here) see what the brightness is when outside. It may be that a life battery is bright enough, in which case it will be a safer bet to leave in the model and save a few grams at the same time.

Steve, as Grumpy Gnome has said, unless there is a compelling reason you want to put the servos in the tail, you'd be much better off with them at the front. The Mighty Barnstormer does not have a particularly long nose so its unlikely the cg will be too far forward with everything as near the front as you can achieve, and an aeroplane with a forward cg will almost certainly fly better than one with a rearward cg, or extra weight to compensate. Those who want the most power and precision at the control surface will accept the trade-off but a Barnstormer is not in that league. As suggested, a closed loop (pull pull) arrangement for the rudder and tailwheel, and a snake to the elevator would be ideal for the model. Its your build of course and you're free to do whatever you want, but you may regret it later...

Ok Brian, Thanks for that. The LEDs seem bright, but may not be quite as good outside. I'd like to leave them as bright as possible though don't want to burn them out, I'm hoping that they will last the lifetime of the model, once the model is covered they won't be accessible without surgery. Do you think that a full charged lipo will be doing them any harm, if so I'll add the resistors as suggested?

The surface mount LEDs for the landing lights arrived safely across the high seas from China so thought I’d see how bright they were and also think about fitting them in the recesses. I was quite satisfied with the brightness especially if they were doubled up in series. Each LED is rated 3w at 3.7v. By using a 1000mAh 2s lipo (7.4v, which provides the ideal voltage) no regulation is required. The current drawn is 0.94A, which doesn’t tally with my schoolboy science formula of W=IV so I imagine the stated 3w is optimistic, however the battery should power the lights for many flights between charges. Given that the lights are only on for a minute or so per flight, the little battery should be fine. At first, I wired a couple using red/black wire but thought it intrusive so tried again using white wire. Although far from scale, I wanted to include LEDs on this model and had the brainwave that adhesive backed silver foil would make a simple reflector, but having tried it decided it was too amateurish so went back to the original idea of chrome sprayed plasticard. With the basic set-up complete, the LEDs were stuck with double-sided tape so that a test of the lamp wiring and control could be conducted. It worked but melted the double-sided tape quite quickly…a Plan B was required. With some fairly thick litho plate (0.33mm) a backing plate was made and the LEDs stuck this time using JB Weld, which claims to be able to withstand 288C. That seems to work as a heatsink, leaving the lights on for 2 minutes did generate heat, but not enough that the backing plate couldn’t be held in the hand. Having lined the recesses with plasticard, each area was masked and then sprayed with gloss black paint. The instructions for the chrome paint I have is that best results are achieved when sprayed over a glossy black base. Once the paint had dried, a dusting of the ready-mixed chrome paint was applied. I think the process works quite well, this was done using a cheapo non-branded Chinese airbrush. For small areas which includes lettering and striping these airbrushes are adequate. Provided they are cleaned properly after use, something which applies to all types and makes, they offer a way of getting good results for little outlay. I’d recommend using a compressor to provide the air, not cans, as even a small gun like this will consume air quickly. My one came from Machine Mart many years ago, I think it was the smallest in their range, its more than adequate for powering this and a touch-up gun which is used for larger areas. I bought a vinyl cutter about three years ago although up to now had only cut paint masks and vinyl lettering, having read that Richard Crapp had cut shapes in plasticard for his current project, I thought I’d try the same. A simple bit of design and hey presto, the machine will cut the acetate landing light cover and the plasticard rim, both of these are for the right-hand lamp. The flap boxes had been made, hinged and latches installed but I’d done nothing with how the little latches would be operated. There is only a small (3mm) bent wire tab which should emerge through the sheeting, the slots for which would surely wear very quickly unless reinforced. To strengthen the 3/32” balsa covering, a slotted piece of 1/32” ply was glued on the underside of the balsa and then the topside covered in 19gm fibreglass overall with a couple of smaller pieces of 50 gm cloth where the slot is. After being left for a few hours to semi-cure, the slots were cut through with a sharp knife and then, once fully cured, tidied up with a small file. Hopefully now the reinforcement will prevent the slots from widening and looking a mess. The next concern is how to prevent paint from getting into the slots when that time comes round…. Having been surprised in how glass cloth as light as 19 gm can impart strength, it gave me confidence in covering the underside of the flap boxes in the same weight material; the upper is open structure so will be covered in fabric. The flap boxes seemed to be quite rigid prior to covering so only required something as a base for the finish. 6 gm of resin was all it took to get to this stage and that also included covering the areas for the latches and servo cover. After 24 hours a light rub around the edges with a sanding block will cut the cloth. Using a sanding block rather than a knife will trim the cloth at the very edge leaving nothing to clean up afterwards. The next time fibreglass resin is required for another job, a second coat of resin will also be applied here, there’s no point in mixing resin especially for this one job as the small amount required would just result in waste – something I’m averse to! The model has got to the stage where its structurally complete, so time for an assembly to check the fit with all the main bits in position. Not much room to move around with the wings on so it won’t stay like this for long! The undercarriage oleos from John Brooks are a work of art, it seems a shame to cover them up, I just hope my landings do justice to them. While there is still a fair way to go, the next tasks are cockpit glazing and making up the control linkages, particularly the closed loop runs for the rudder and tailwheel, then attention can be turned to covering.

Don, The mixing doesn't 'cut in' its always there - zero mixing at idle and maximum (whatever you've set) at full throttle. I use Futaba, but I'd expect all makes nowadays will have the facility to not only have the mixing linear but follow whatever curve is desired. Its worked well for me on a draggy biplane and I have one model which, ordinarily, will put its nose down with increased power, setting a mix to apply proportional 'up' elevator with increasing throttle has cured that one. Built-in side and down thrust is a throw-over from free flight days and simple analogue radios, if you want to make a model of an old design exactly as originally designed, that's absolutely fine, however the facility now exists, in just about all transmitters I'd think, to be able to let the electronics take the guess work out of it.

I’d agree that built-in side and downthrusts are unnecessary with modern radios, the same result can be obtained with a bit of programmable mixing – progressively increased down thrust with advancing throttle, and increased right rudder with advancing throttle. What built-in angles are required is a bit of a guess for a given power output and if its not right you are stuck with it. Using the radio to obtain the trim required can be fine tuned once the first flights have been made. My start point would be a 5% offset at max throttle, if that’s wrong it doesn’t matter just add more or less for the next flight. Also, making the bulkhead/fuselage joints using a tab and slot arrangement, similar to the two formers in your photo, will impart considerably more strength than butt joints, won't add weight or take up useful space. The bulkhead joint is the one where the strongest glue available should be used, Hysol takes some beating!