Model Engine News: October 2013
New Books and Magazines This Month
Engine Of The Month: Yulon!
Tech Tip of the Month
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Ronald A Chernich appearing on the Model Engine News web site are licensed under a
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What can I say? Another bad month, but at least this issue is not as truncated as last month's effort. It is still a bit shorter than what has become "normal", but starting the new one as soon as the previous one has been released seems to have helped a bit. Rest assured that if I did not enjoy it, I would not be doing it, and not being dead, yet, we press on as best able, with apologies to those who are sending information and pictures which I've not yet used. All are tagged for future use, although my system is not exactly infallible. The basic problem has become low energy and pain. The team of doctors I have looking after me provide effective pain control which makes me very happy and a bit useless, so I try to tough it out, although I find that even propped up in bed with my laptop, my endurance is low, not to mention having to get up to use the scanner, do some library research, etc. I'll make it through to January, I hope, then we'll re-evaluate. I also have a neuro-surgical option which may or not make things better—could even end up worse, so I'm not commiting to it until things become impossible. Ok, enough of the downers, let's make models...
Despite all above, I did have a couple of good days during which progress was made on the Still Stuka mentioned in August. I covered the wing, tail, flaps, and elevators with Polyspan, the first time I've used this material which is said to be stronger than silk, and not much heavier than medium weight silkspan tissue. The Polyspan was applied using SIG "Stix-It", another first for me—who said old dogs can't learn new tricks? This is a brush-on liquid which smells like it must be lacquer based and acts as a heat activated adhesive. It worked perfectly for me, and being laquer based, does not cause problems with later doping and acrylic lacquer color finishes, as do some other brush-on, heat activated, "gummy" adhesives. I like to cover wings and tails of control line stunters (which are generally one-piece models) before assembling them. They are easier to handle this way and the tendency to bash them into light fittings and walls while covering them is reduced. It also allows me to track the weight of things for comparison purposes. The Stuka wing has a span of 48 inches, and has an area, including the flaps of some 480 square inches. My wing, complete with flaps, horn, hinges, push-rod, and lead-outs, weighed 202 grams bare. Covering with Polyspan and one coat of 50/50 dope added just 20 grams. The tight "weave" (actually, there is no weave) looks like it will seal with less dope than silk, or silkspan even. The weight increase on the tail surfaces was not measurable on my digital kitchen scales, so must be less than 2 grams. The strength is excellent and so far, I'm impressed. The only negative is that is does not pull around compound curves very well; the tips of the wing requiring two pieces for each side, but I can live with that. Incidentally, the top block was moulded from 1/8" sheet following the Al Rabe method, as an experiment. It too has worked out perfectly and the turtle deck will be done the same way, as soon as I get around to making the form block.
Sadly, it seems like the time has arrived to rationalize the workshop a bit, so I'm selling my Amco 7-1/2" shaper. The machine is in excellent condition, mounted on a mobile, free-standing base which can double as a shipping container. Managing shipping would be beyond me I'm sorry to say, but if there's any reader out there who can arrange a local Brisbane, Australia pickup (it's like heavy, man), drop me a line!
K-Dee Special Revisited
Back in our August, 2012 issue, we added a Watzit which got me so stoked, that the simple watzit description and and answer expanded itself into a full-blown engine review. The engine in question was the K-Dee Special, a 15cc sparkie with twin shaft rotary valve inlets. I became so obsessed with the engine, I even tracked down and bought a set of castings to place under the bench, with all the others. During the process of researching the engine, I was given some images of completed examples, whose constructor details had been lost. Well, last month the builder sent me a very nice email and I'm most happy to add his name to his work. The builder is Mr Anthony Williams, who has generously offered more details about his Silver Crown (seen here). From the image we see that not only does Anthony build nice engines, he knows how to best present them in a photo as well. Expect an update to the K-Dee Special page, in the fullness of time.
Those good folk at Hemingway Kits (UK) have announced another new IC kit which will appeal to Westbury and stationary engine fans, namely the Wyvern, a fine example of which is pictured here. The engine is a water cooled, four-stroke, overhead valve, spark ignition design with twin 6-1/2 inch flywheels, a bore of 1-1/4 inches, and a stroke of 2 inches, for a displacement of 2.45 cuin. It first appeared in the Model Engineer in 1963, with the issue when the ME changed format from "pocket" size to the large tabloid-ish format (the subsequently reduced size again, but not so much, then increased again...) If you hurry up and place your order before October the 6th, 2013, Hemingway will include tungsten points, a sparking plug, and gasket material with the plans and materials kit for £300.00 Sterling, an effective 15% reduction on list price.
Incidentally, the builder of the Wyvern in the photo was my old friend and mentor, the late Russell Watson-Will. Russ' wife always said the sound of the Wyvern reminded her of a Mercedes (model unknown ). Hemingway has catre blanch to use whatever photos from this site they wish, and I'm most pleased to see Russ' Wyvern being used to advertise their latest kit. I'm sure it will be a quantum improvement on the old Woking Precision set.
Here's a new design from our old pal, Dave Miner. It is a 2.5cc, two-stroke, cross-flow, glow ignition, bar-stock, front rotary induction engine fitted with an R/C carby. Dave reports that it is easy to start and build, and will turn a 9x4 prop at 9,000 rpm, or a 7x6 at 13,400, using 10% nitro fuel. It will idle reliably down to 2,800 rpm. I think Dave has selected a "sweet spot" size for his design. Parts are not so small that machining is tricky, nor so large that mistakes are costly. Fits in the 2cc region are less critical than sub-1cc engines too. I suspect that owners of tabletop machines may have some bother as the size is on the limits for machines like the Sherline, but the ready availability today of inexpensive vertical milling machines like the X3 would help considerably with the required milling. Dave has followed our suggestions on Engine design features for first time builders, an says the only thread cutting required is the crankshaft (why not a stud, Dave?) He las also kindly offered plans and construction details, so as I seem to say all too often, watch this space!
Steve Huck continues to develop and refine his Demon automotive V8 design, even if the latest modificatio, he admits, is not exactly major: the carby lever has been shortened by 0.050" to provide more clearance on the Rootes blower. Steve reminds us in his update bulletin that there are two carburettor versions, but the change has no implications for either. If you chase back to the Demon news item in the May, 2013 issue, you will find other links to previous information about this engine, along with where you can get plans. I've examined the plans in detail and they are an excellent, clear, well detailed set.
New Books and Magazines This Month
During the past month, I needed to refresh my mind on some aspects of aircraft design. My memory managed to come up with knowledge of what was required, but the how it was done had left the building. Fortunately, where that "how" might be found still remained, which I believe is the optimum. You don't need infrequently used stuff on instant recall, just the knowledge that it does exist, and where to find it is quite enough. What I was after was how to determine the Mean Aerodynamic Chord (MAC) of a complex wing planform, how to calculate the Tail Volume coefficient (VH), and how aircraft weight and balance is done at the design stage.
All this, and more, resides in one of the oldest "bought when new" volumes in The Library: Light Aircraft Design, by Ladislao Pazmany, self-published, 1963. The book is soft covered with a cloth spine and contains 80 pages on the design of light aircraft, mostly using as an example, the author's PL-1, a very efficient and safe two place, single engine, fixed tricycle gear, low wing monoplane with stressed skin, all metal construction. The book takes the reader through the main aspects of design, using no more that high-school level mathematics (no calculus required), considering factors such as airfoil selection, power plant requirements, safety (crashworthiness), weight and balance, plus a lot more. What is not covered is stress analysis, which helps keep the text "accessible" by an average reader who is prepared to work at it and not be scared by what a few formulae and graphs are trying to tell you.
Ladislao Pazmany (Paz to his friends) was born in Hungary and grew up in Argentina, before emigrating to the USA in 1956 where he worked in aircraft design for companies such as Convair, Ryan, General Dynamics, and Rohr. He was recognized as a world expert on landing gear design. As soon has Paz arrived in the US, he attended a meeting of the local chapter of the Experimental Aircraft Association (EAA), and soon after a series of designs for home built aircraft and related publications followed. The PL-1 used as the example in his 1966 design book was superseded by the PL-2 which cleaned up the design a little, but retained the basic configuration. An unusual feature of the design was the use of 2024-T0 alclad sheet for the ribs and formers. In the T0 state, this sheet bends like soft lead, enabling extremely complex, compound curved formers and ribs to be easily made using wooden form blocks. The downside is that the parts must then be heat treated to bring them up to the T43 hardness state. This cannot be done at home and so, has had the effect of limiting the popularity of an outstanding design. This excellence was recognized by the Taiwanese Air Force who licensed the design and put it in quantity production as their primary trainer.
Paz followed up the PL-2 with a very different design. This was the PL-4A, a T-tailed single place, all metal, low wing design with foldable wings (the PL-1 and 2 wing spar was straight through, tip to tip, including the seat bottoms and flap handle). The PL-4A wings could be folded and secured by a single person and was narrow enough to be road-able. In keeping with the light weight, low cost, sport plane theme, it used a modified VW engine, with a belt reduction drive. His last design, the PL-9, was a 3/4 scale Fiesler Storch replica.
Ok, by now you should get the point that Paz has the credentials to speak and write with authority. His plan sets are also a work of art, conforming the industry standards, leaving nothing to the builders' imagination—probably a factor in the Taiwanese Air Force decision process. His writing is clear and light-hearted, but not short on complexity when complexity is required. I got precisely what I was after when I pulled this old book off the shelf where it has sat for the past 48 odd years, and re-reading parts of it have reminded me of things either forgotten, or never known. There are literally heaps of texts on amateur aircraft design and construction. I've seen some written by amateurs and they basically scare the pants off me. Pazmany's book on the other hand is good in what it explains, and has the benefit of including notes of where he has simplified some aspect, or omitted something as being beyond the scope of the text, so at least you are left knowing there are things you don't know, and what they might be. For a serious model maker who as progressed beyond taking a Nobler plan and changing the wing tips and turtle deck, you will get a lot from this little volume. In my case, I'm re-designing a model to take electric power. The extra weight of the battery meant I needed to do a weight and balance on the proposed model, or be faced with possibly having the add a ton of lead to the tail, or nose. This required shifting the wing. With the wing moved, I needed to calculate the Tail Volume Coefficient to compare it with other designs known to turn nicely, but exhibit positive longitudinal stability (the ability of a F2B stunter to "groove"). That required calculating the MAC for wing and tail. All I needed was in Paz's little book, plus a lot more.
Amazingly, the book remains in print! You can get a Kindle version (for your Kindle, iPad, or Android reader) from Amazon for $50, with free delivery. Print versions are also available, with a little hunting. So four and half stars to Light Airplane Design (I've knocked off half a star due to some areas I thought he could have expanded on, plus the fact that my 48 year old copy's binding is, like its owner, disintegrating...disgraceful!) .
Engine Of The Month: Yulon!
Lovers of loud old engines rejoice—and when we say loud, we really do mean LOUD! Adrian has managed to put together all you ever need to know about an old charmer whose reputation approaches legend: the Yulon series from Olde England. This is not our first tilt at the Yulon—the thing is far too magical for that, but seeing as how the earlier Yulon page was little more than a nod and a wink to the type, it has been replaced in the Engine Finder with what I believe is now the definitive word on the beast. So click through to the new Yulon page, where you get it all: the 29, the 30, the 49, the Yulon Eagle, and one I did not know existed until editing Adrian's latest, the Yulon Diesel!
Tech Tip of the Month
There are three secrets to a good solder joint, my electronics instructor used to say, cleanliness, cleanliness, and cleanliness! Provided that you follow these "three" rules, making a good solder joint is easy, very easy. Despite that, I continually see otherwise fine jobs marred by poor soldering, and in the cases of some model aircraft, rendered un-safe in the process. Most often, this is evidenced in the way solder has failed to flow around the piano wire and the washer intended to retail a wheel. This always leads me to wonder what state the push-rod retainers might be in. If the model is a profile C/L job, the sad truth lies open to public gaze, so I shudder quietly, to myself, being far too polite (these days) to openly criticize someone else's work. It seems that the cleanliness lesson has not been stressed enough, so this month, I'm going to be an absolute pedant and write more words with pictures than I'd previously thought possible or perhaps wise, on the simple topic of soldering a washer to a piece of piano wire in the new, How To: Solder a washer to wire page.
Collectors' Corner: Mills Snos
Here's the first in an occasional series intended to help collectors with things like distinguishing between models, serial numbering, etc of popular model engines. At the time of writing, the MEN site contains 1145 individual pages of data, with around 32,000 images and even I no longer know precisely what's in there. We will almost certainly be repeating ourselves, re-presenting data already scattered around in various articles on the site, but therein lies the issue: scattered! At least this way some of that useful information is collected and our automated indexing should list it in the Site Map page, and search facility. To kick off the series, Adrian has put together what we Motor Boys know about the serial numbering system employed by Mills Bros in their extremely popular and long lasting engines. Click the thumbnail of follow the link to the Mills Bros Serial Numbering and Production Figures page.
This section is intended to alert you to little things that are hard to expand to a full news item, or cunningly wind into the Editorial, but are worthy of note never the less.
- Some (ahem) grammatic errors in the September 2013 issue have been corrected.
- The review of the Gotham Hobby Deezil has been updated with two new images, plus words about them. To save you the impossible task of locating the insertions, here are links to them: Early Gotham Deezil with tank, and Early Deezil fitted with tank from another example.