Traplet Publications Ltd:R/C Scale International
Sept/Oct 2002 Issue 32 PT-17 Stearman
This review is re-printed by kind permission of Traplet Publications, Simon Delaney
For copies of the mags. containing
this review and details of
Author: John Carpenter
Boeing Stearman - Part One
Flair Products' 1:4 scale PT-17 reviewed
The truth is in there
Flair are well-known in the RC kit and accessory industry and have been praised in previous issues of R/C Scale International for producing kits for the scale modeller that would otherwise have been destined for plan builds only. Their Bristol F2B is a good example, and their 1:4 scale Tiger Moth has reached almost mythical status! The addition of the PT-17 has been eagerly awaited by many and I can tell you it's worth waiting for.
This is a large model. It comes in a large box which is deep and packed with a huge array of materials heavy enough to strain the hernia. The contents were removed with increasing amazement and enthusiasm. First came a 55 page instruction manual which includes full descriptions of each building step, complete with photographs. This manual also includes illustrations of all the die cut or CNC parts and full kit parts listing. To give you some idea, there are 253 parts references and 43 large pre-cut ply or lite ply sheets alone (yes, I counted them). Add to this a significant quantity of sheet and strip balsa and hardwood and a small mountain of assorted metal bars and strips, plus two very clean glass fibre mouldings and various ABS mouldings, and you begin to get an idea of just what sort of kit this is. Delving yet deeper, I found six plastic engine cylinder kits, a pair of beautiful and light 5.1/2" wheels, moulded cockpit windscreens and a 20 oz fuel tank. Oh, and before I forget, three sheets of super detailed CAD plans, two of which (the wings in particular) are printed on transparent film so that the plan can be reversed to build the other handed parts. Last, and by no means least, there are bagged metal parts to construct two oleo legs, each over a foot long. Not much evidence of the ARTF approach here then!
The initial impression is of a very detailed and comprehensive pile of good quality material and a quick look at the pre-cut sheets confirmed that the quality is more than just skin deep. I am not a great fan of ABS but do recognise that it has its uses. It rather depends on the quality and thickness of the mouldings and the areas where they are used. In this case the mouldings look crisp and strong and, more importantly from my point of view, are not used around the engine area where engine vibration and heat usually ensures a short life. Flair Products have used a glass fibre moulding in this area which suggests that they are very aware of the limitations of ABS. The more the kit contents are examined, the more clear it becomes that a great deal of thought, care, and it must be said, time and money has been invested in developing and producing it. In particular, the plans and instruction book show painstaking effort has been made to cover every aspect of the build in sufficient detail that there should be no nasty surprises. Possible mistakes the builder can make are clearly identified and warned against. In one particular area I was gratified to note that the instructions stated: "Now if you did not read my previous warning, and like me you forgot to insert part... you may now be cursing." It then goes on to explain how to resolve the problem. Building instructions with a smile built in. I just loved that!
Having recently moved house and completed a new model workshop, this kit was set to be the first model from the new premises. So with unbounded enthusiasm we open the instruction book at page one.
There are a large number of die-cut parts in this kit, as previously mentioned, and it is suggested that these should be identified and numbered in accordance with the identification sheets provided. This is actually essential unless you want to spend several days just searching for parts. I also referenced each die-cut sheet. Having done all this it is relatively easy to locate the required parts by checking the parts list to identify just what the part is and then the die-cut illustration to find which sheet it is on. Then just haul out the relevant sheet and voila, there it is. All this may sound very complicated but is in fact simple and quick once the parts are marked up. If you don't do it you will spend a great deal of time up to your elbows in the box. Those nice friendly people at Flair Products have even stamped the part numbers on most of the sheet and strip material to help you. It's a very long time since I last saw this in a kit! Without this it would have been all too easy to select the wrong pieces from the huge pile of wood. Believe me, I almost did that anyway on several occasions until I learned to trust the instructions.
The instructions suggest that the building should follow the order given to avoid any problems in what is after all a complex kit. I followed this advice and soon found that my confidence in the instructions was growing. Before starting each major part of the model I carefully read through the complete section in order to understand the construction involved and then went back to the beginning and followed through step-by-step. I know this all sounds like kit building for the terminally stupid but in this case it actually did simplify the whole process. In fact whenever I departed from the instructions through error, forgetfulness, or trying to be clever, I soon found I had created a problem for myself. By the time I had built the tailplane and fin I had complete faith in the instruction book and thereafter ceased to attempt to second guess the designer. I suggest you do the same. Just do as it says, exactly as it says, and when it says it and you will have no problems. The excellent plans, instructions and photographs combine to reveal all if you just have faith. To put this statement into perspective, you should be aware that I have been a model builder of both kits and my own designs for over 40 years and thought I knew how to build, whatever the instructions might say. Believe me, the instructions really do it in this case!
Most of the aircraft is constructed of ply or lite ply with balsa mainly used for stringers and areas of sheeting. This might suggest that the structure would be heavy. In fact a great deal of attention (and die-cutting/CNC machining) has been given to removing much of the material through use of lightening holes. As a result, quite a large percentage of the ply from the box actually ends up in the waste bin (or put to better use in my case: I mix up batches of epoxy on the bits). The lite ply is die-cut and needs a touch with the scalpel to free the parts. The CNC parts are in the harder birch ply for parts in more highly stressed areas. The cutting here is superb but paradoxically, the parts are harder to remove from the sheets. The cutting leaves several small and intentional uncut sections in the profiles to keep the parts in place and herein lies the problem. Birch ply is strong and even these small sections of uncut material defy easy removal with a model knife. After several scalpel blades had snapped and departed like shrapnel across the workshop, I looked for a safer method of removal. The answer is to use one of those saws that are made up of a hacksaw blade fitted into an open handle. This did the job quickly and neatly, the CNC slots being just sufficiently wide to accept the blade perfectly. You can have that little tip for free because I'm a generous soul! All the parts fitted together as they should and all the cut-outs for spars or interlocking parts were either spot on or just on the tight side. This is so much better than having such joints too loose since then glue fillets or filler pieces have to be used which are not necessarily as strong.
I am not going to bore you with a 'how I glued part A to part C and then undid it again' because it is much too boring, so I will just concentrate on what I found to be the most interesting or unusual aspects of the kit as the build progressed. Hopefully the photographs will help reveal the design and construction features.
These parts are constructed over a central core of thin ply heavily fretted away to leave just a skeleton of material. A masterpiece of the die-cutting art. The leading edges are balsa or hardwood dowel, that on the fin passing right though the tailplane and interlocking into the fuselage (once that part is built of course). All control surface hinge lines are shrouded in the scale manner, a nice point which indicates the attention to detail.
This is a massive structure of formers and stringers which is actually quite straightforward to build. There are several points of interest here. Firstly, the engine mounting system. This is made of a plywood tube which has the firewall at its front end and which slides into the front two formers and is thus adjustable to match the length of the particular engine of choice, until it is finally glued in place. A clever idea, and the parts go together to produce a good tight fit. The design is such that this engine mounting system is hidden within a glass fibre moulding of the front fuselage, which partly surrounds the chosen engine. Almost any model engine will fit with a little judicious trimming of the moulding. I used my trusty Laser 200, which is a twin cylinder V layout, without problems.
Secondly, the undercarriage which comprises two large oleo legs bolted to the fuselage with a large metal 'carry through' plate to spread the load between the legs. Altogether a fairly substantial looking piece of engineering that is easy and quick to fit. A kit of parts is provided to make up each oleo leg. This involves the assembly of some machined tubes with springs and a couple of sharp blows with a hammer on some taper pins. Job done, and even I could do that, and I usually avoid anything to do with working with metals - it does so ruin the fingernails! By the way, when was the last time you bought a kit with an oleo undercarriage kit in it?
Another point of interest is that because the lower wings plug into the fuselage there is no access to the interior once it is covered, other than though the cockpit openings. It would pay dividends therefore to plan the radio and fuel tank layout before all the stringers are fitted. I only saw this one just in time even though it is mentioned in the instructions. You have been warned! Fitting the radio through the cockpits could quite ruin your day!. There are no detailed instructions on fitting the fuselage servos and radio so this is one area where original thought will have to be applied. Since the completed model may (will) be tail heavy as it is a short nosed aircraft, fitting everything well forward would be a good idea. Yet another reason to do it before fitting the stringers makes it difficult.
The top wing panels plug into the centre section which is itself bolted to the cabane struts. This is usually an area where building errors can easily occur (been there, done that) but Flair Products provide aluminium cabane struts pre-shaped and cut so all that needs to be done is to bolt them in place, check for squareness and then align and bolt the centre section in place. This bit took all of thirty minutes! I kid you not, it really was that simple. By the way, the 'plug in' arrangement features sockets built into the main spars sliding onto very substantial aluminium spars which pass right through the model. Again, more than adequate for the purpose and the fitting is into pre-cut parts so it is difficult to get it wrong, so long as you follow the instructions.
Four panels to build and all very straightforward. Ailerons in the lower wings have cleverly designed scale hinging using paxolin plates. Everything fits into place as it should and the ailerons in particular are a work of sheer pleasure, having rolled ply leading edges and operation by pushrods within the wing section. Incidentally, the rib spacing, and number of ribs, is an accurate scale representation too. An unusual feature is that the instructions require that the wing sheeting of 1/16" balsa is rolled round the leading edge in one piece. Sounds and looks difficult but is in fact easy, thanks to careful selection of the balsa supplied, and the instructions. The result is also well worth the effort. Interplane strut mountings are built into the wings and the final steel plates fitted into them after covering. I didn't even have trouble getting the strut lengths right on both sides and everybody has trouble with that!
One of the things that sets the Stearman apart is the exposed radial engine. This feature needs to be well represented if the model is to capture the essence of the real thing. It is also perhaps the reason that you don't see too many Stearman models about until now. Flair Products provide six dummy cylinders in plastic kit form and a dummy crankcase in glass fibre which fits over the front of the model engine. I only used five cylinders since the Laser V twin provides the other two. The dummy engine makes up into a robust representation of a radial engine although I have not been able to recognise which particular engine is being represented. For the purists amongst you it is not quite a Lycoming or Continental engine as used in the original aircraft but somewhere between the two. Nevertheless the completed dummy engine certainly does a fine job of capturing the essence of an exposed seven cylinder radial and certainly lends itself to a bit of dressing up by those wishing to enhance the kit (including me!).
Well that just about wraps up the build process. In the next issue we will be discussing the covering and finishing, and finally the flight test. Hopefully the photographs will fill in any gaps in the description and give an idea of the model as the build progressed. All in all a fascinating and enjoyable exercise. Any gripes? Well there were a couple of points that I was not that enthusiastic about but in truth these were so minor that they are not worth the mention. It would be a bit like telling the chief designer at Boeing that the ash trays could be a better shape. I suppose the acid test of the quality of a kit is whether one would be prepared to build a second one and if, in doing so, what would be altered. In my case just give me a couple of weeks to recover and I would happily start a second one and I would change very little. More on that next time.
Publication: R/C Scale: Jan/Feb 2003 issue 34
John Carpenter completes Flair's 1:4 scale PT-17
Having just completed and covered the airframe I was rooting about in the bottom of the box looking for some detail metal part when into my hand fell... a wing rib! Shock horror, panic stations and 'Houston, we have a problem'. What passes for a brain went into overdrive for a moment. What had I done? The wings had gone together exactly as per plan and there were no obvious gaps or errors visible. A quick count of ribs on the plan and in the model produced a match. A check in the ever useful pre-cut part identification sheet finally revealed the small remark that part 140 included one spare! Now that you have read this, it won't happen to you. Are we helpful or what!
Finishing and detail
I mentioned in part one that the radio installation in the fuselage needs to be planned and provided for before all the stringers are fitted. This also includes the elevator push-rod and the rudder and steerable tailwheel cables. You can do this after covering and indeed the elevator push-rod is fitted as the tailplane is fitted, after covering. However, planning the installation and making everything up to fit is so much harder with restricted access that I was a bit surprised that Flair do not put greater emphasis on this point. However, this kit is not really intended for the uninitiated so perhaps they thought common sense would apply. Trouble is, common sense comes in so many versions, it is not that common! Just to make life even more interesting, in my case I also needed to fit two fuel tanks (one for each cylinder of the Laser) in the front fuselage directly behind the front bulkhead. Not difficult if done at an early stage but a lot more problematic with all the stringers and front fuselage skin in place.
I covered the airframe in the appropriate yellow and blue Solartex to match the US Army scheme. This is a nice bright scheme and easy to do, particularly since there are paints from the same manufacture which match the 'tex colours. I used Solartex rather than Glosstex because I have always thought the gloss material is just a little too shiny. Feel free to disagree but I prefer a gloss fuel- proofer sprayed on to give a slight sheen. Yes I know the 'tex material is fuel proof but the proofer goes over everything and protects the painted areas and keeps the dirt out of the fabric. However, before we reach the fuel-proofer stage the opportunity just has to be taken to add such items as elevator trim tabs, pitot head, fuel lines and wing walkways. These items are all very easily produced from odd bits of wire, small nuts and off cuts of Solartex and dabs of paint. There were a few other items of interest arising from the finishing stages and these are described in the following paragraphs.
The completed wing panels, once covered, look a bit bare and uninteresting. The application of rib tapes adds textural depth and interest. There is a 'quick and dirty' method of producing them which results in a good representation of the aircraft detail without taking weeks to produce. Onlookers will marvel at your perseverance and skill, so let's just keep the secret between ourselves. Take a piece of Solartex of sufficient length to produce the required tape. Carefully make a cut at the top left hand edge of the piece of 'ex and separate the edge from the backing. Now grasp the corner and tear the 'tex along the edge. Solartex will tear along the warp or weft of the material to produce a nice neat straight edge. Now make your next cut the width of the intended tape from the torn edge and tear again and you should end up with a straight tape of the required width and length with a very slight frayed edge. All future cut and tear operations from this edge should produce identical tapes. Try it. It works almost every time and saves hours of cutting out with a scalpel and straight-edge. I have examined photographic evidence and a full size example of the aircraft from a few feet away and could not tell whether pinked edge tape was used or not so my method is probably good enough in terms of accuracy. The completed job certainly helps bring the model to life. By the way, the fuselage is mainly fabric covered over stringers so guess what, more tape required here! The finished job is, however, well worth the effort.
Cockpit canopies and windscreens are always a bit of a pain to fit and doubly so in my case here since I covered the airframe and was then faced with either cutting away the 'ex so the glue would 'take' to the structure underneath or finding an alternative method. I chose the latter. This is a trick I have used before with good results. First I tape the windscreen in place and drill pinholes through the flange and into the fuselage skin. Then, using some miniature scale rivets (actually short flat headed metal pins sold in packs by Nexus Model Supplies) I apply a minute dob of slow set cyano to each rivet, push it into place and hold briefly until the glue sets. About ten or twelve rivets does the job nicely. Of course this only really looks right if the real aircraft had a windscreen frame that was either riveted or bolted on. Exactly right for the Stearman in fact.
I made up and fitted a remote glow connection for the Laser, making use of the scale oil filler cap in the engine nacelle as a plug in point for the glow lead. It is quite possible to connect the glow leads directly to the plugs but removing the leads once the engine is running could lead to time spent searching in the grass for several missing fingers so discretion is the better part of valour here.
The front bulkhead, through which the engine mounting tube passes, is quite heavily fretted away both for access to the undercarriage mounting behind it and for lightness. Unfortunately, once the model is completed it becomes obvious that these various holes will allow exhaust residues through to the next bulkhead and the gap between the two will become an 'oil trap' in the fullness of time. A quick solution here was to make up a cover plate to be fitted after the undercarriage is finally bolted into placed. Future access to the undercarriage mounting bolts, will necessitate cutting a couple of small holes for the Allen key. This is a price I am prepared to pay for an oil free front end. An access panel was also made and fitted with small screws to the lower front of the bulkhead to allow access to this area because the front flying wire tensioning spring sits inside here.
There is quite a lot of rigging to be fitted but the system used, which includes metal plates glued into pre-prepared slots in the structure and nylon coated fishing trace, is easy to fit and looks the part. The cable supplied in the kit (a stated 40 feet of it!) was actually about ten feet short but fortunately I had some 'in stock'. This was the only material shortcoming in the entire kit. Assembling the model at the field does take a little time and connecting up the rigging cables is the quickest bit. The most time consuming part is fitting and tightening the eight wing bolts and the twelve nuts and bolts holding the interplane struts. Having had several nuts slip from my fingers and trampoline off the fabric into the grass I finally built them into the ends of the struts. This speeds up assembly considerably. Use of M3 bolts and a ball driver would improve matters still further.
I used only five of the six dummy engine cylinders supplied because the 'real' engine is a twin cylinder Laser 200. I reduced the cylinder height on the dummy cylinders a bit more than the instructions suggest because the completed engine still looked over scale and also because it helped the Laser to 'blend in'. I also chose not to fit the pushrod covers since they merely accentuated the missing two scale cylinders (and, to me, represented the wrong engine). To further assist the disguise I painted the originally black dummy cylinders a fetching shade of aluminium, courtesy of car acrylic spray (Audi aluminium does the trick). I thought this preferable to spraying the Laser cylinders black.
The tailwheel area of the fuselage is enclosed within an ABS moulding which also covers the elevator, rudder and steerable tailwheel connections. The instructions suggest that this should be glued in place but I chose to make mine removable to allow access 'just in case'. It is in this area that I had my one problem with the kit. The design of the elevator horn is a metal plate which the instructions state should be firmly glued between two hardwood blocks which are themselves screwed to the elevator. What worried me was that the resultant horn was actually taking the elevator loads through a glue joint rather than a mechanical joint. Should that joint fail, and it could come under quite a heavy load, then the result would almost certainly be terminal for the model. Since I was building the model for review then I should, in all fairness, follow the instructions and use the materials supplied. Furthermore, I have no evidence that the proposed method would not be entirely satisfactory, but the whole principle just gave me goose pimples looking at it. Having made the tail cone removable I could at least keep an eye on this area but common sense (or my version of it) told me that any failure was likely to be sudden and under load so inspection was unlikely to be helpful. I contacted Flair for a quick discussion of my concern and they reported that two prototypes had now been flying for a year and no problems had so far emerged, either from their prototypes or reported by customers. Nevertheless I agonised over this for some time but in the end my concern got the better of me and I fitted a nylon horn firmly bolted to a hardwood block which was also glued and screwed to the elevator centre. If I had not made the change it would have worried away at me every time I flew the model. I hope you and Flair Products will forgive my possible excess of caution.
As previously mentioned the kit is very comprehensive in that it includes just about everything to complete the model, including wheels and a fuel tank, both items which kit manufactures often choose not to include. A bit surprising therefore to find that the decals are an optional extra. I indulged myself and found the quality of these items to be very good, given that vinyl decals are always a little thicker than waterslide transfers. A more understandable optional extra is a pilot figure answering to the name of 'Lloyd', after Lloyd Stearman who designed the aircraft. This is a pre-painted item in silicon rubber with the head as a separate moulding so that the 'attitude' of the pilot can be selected before finally joining the parts at the neck. A very nice figure, if a touch expensive. Hey, but if you're going to indulge yourself, do it twice! Anyway, I could not contemplate flying the model without a pilot since the model just looks wrong in photographs with a bare cockpit.
The Flying Bit
Stand up all those who rushed to this bit first! Nice to meet you here, because that is exactly what I do when reading such articles. Anyway, to business. I had expected the model to be tail heavy and even with the Laser 200, which is a tad heavier than a single cylinder equivalent, I thought it prudent to fit a larger than average nicad (2000mah) right up front to help balance things out. This proved correct, no further ballast being required. With all radio checks complete and the control throws set as per the instructions the Laser was fired up and checked. A quick taxi test on grass revealed that the tailwheel control is very effective and that the stalky undercarriage would allow a wing tip to be dragged in the grass if rudder and throttle were carelessly applied. Gradual application of power had the aircraft off the ground and climbing strongly after no more than 30 feet of ground roll. Increasing amounts of down trim were applied to control the attitude until straight flight was achieved, this required a lot of down trim. Interestingly, closing the throttle did not have a significant affect on the trim, indicating that the problem was not related to the engine thrust line. A cautious couple of circuits revealed good solid control authority with perhaps a little too much elevator throw for complete comfort. The landing was uneventful except to note that there is quite a lot of drag so fully closing the throttle causes a very positive rate of descent, just as mentioned in the instructions.
Further flights with the elevator trim and throw adjusted have revealed that the model is an absolute peach to fly. Control authority is good in all axes with perhaps the ailerons the least sharp, in terms of response. I have found that coupled aileron and rudder (thanks to computer radio) with about 5% rudder coupling is very helpful, as is differential on the ailerons, again as detailed in the instructions. Get the landings severely wrong and it is possible to generate the most enormous bounce which is very impressive, not to mention embarrassing with such a large model. However, quick application of a touch of down elevator and throttle will retrieve the situation. Aerobatics are smooth and can be very scale like but do have to be flown rather than just jamming the controls over and expecting perfect precision. Well it is a large scale biplane, what did you expect? There were no nasty surprises and control authority has a reassuringly solid feel about it. All in all the flying experience matches the building experience and I look forward to many happy hours getting to know the Stearman's little tricks and idiosyncrasies in detail. I think that the match of the airframe to the Laser 200 is just about perfect. The instructions suggest that a laser 150 is the minimum power and I would certainly be happier with a bit more than that. The Laser 180 should be a good match if you don't wish to go for the glorious throaty crackle of a twin cylinder four stroke hauling 22lbs of biplane up into the sky with plenty to spare. You pays your money and you takes your choice!
This is always the most difficult part of any review to write. The questions just pile up. Is it good value? Is it well designed? Is it easy to build? Is the kit essentially complete or will I have to buy a ton of bits? Any nasty surprises hidden away in the flight performance? How accurate a scale model is it? Can I trust the reviewer to tell it as it is, warts and all, or is there some hidden agenda. Let me try to answer these.
Yes it is very well designed and yes it is easy to build, if you follow the instructions and are prepared to enjoy the experience. This is not an ARTF nor a build that should be rushed. The kit is very complete, including wheels, tank and many other parts not normally seen in kits and all of good quality. Flight performance is exemplary and should cause no problems to the reasonably experienced. Yes I believe the kit to be very good value for money, not just for what comes in the box but also for the time, effort and yes, money that the manufacturer has invested in ensuring that the product is one of the best of its kind. Yes it could be improved in one or two areas, as I might have indicated but then I have yet to build any kit (or model of my own design) that could not be improved here and there. The design and production engineering has to stop somewhere otherwise the kit would never reach the model shops. As far as I have been able to ascertain, the model is an accurate rendition of the aircraft in general terms such as rib spacing etcetera. It would certainly serve as the basis for a competition model. Can you trust the reviewer? Well, I asked the editor to let me review the kit because I like building and I like the Stearman and not for any other reasons. I have no connection with Flair Products other than as a customer. Look, just trust me, OK?
If you hunger for a big sexy scale biplane and love building, go buy this one. Tell Flair I sent you - they'll be expecting you!
Wingspan: 2264mm (89")
Weight: 8.6 - 10.5kg (19 - 22lb)
Engine: 150 four stroke minimum, 120 two stroke minimum
Radio: 4 channel, 5 servos
Servos of minimum 45 Ncm (64oz. In) are advised for all control surfaces.
Sources: Available from your local Flair dealer.
Flair Products, Holdcroft Works, High Street, Blunsdon,
Swindon, Wiltshire, ENGLAND. SN26 7AH. Tel: 01793 721303. Fax: 01793 721841. Website: www.flairproducts.com