John Stainforth
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Everything posted by John Stainforth
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Spray guns used for S6b: FastMover (left), and Sata Minigun 4400B (right)
John Stainforth posted a gallery image in Member Albums
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Forum members' new models: Let's see them.
John Stainforth replied to Paul Marsh's topic in All Things Model Flying
That Disco 2 looks really something, but how do you get the CG far enough back? -
Jon, thanks for the reply. Of course, what matters for a scale model is where the propellor shaft is, not the crankshaft. Warbirds with V-engines such as the Merlin had the prop shaft offset upwards, which I think is what you are suggesting. For an upright mounted engine, the position of the crankshaft and bulk of the engine would then be lower in the fuselage, which could be beneficial as far as tank positioning is concerned (which is not currently a Laser strong point). Also, it might make it easier to hide the cylinder heads entirely in the fuselage. And then there is that added noise benefit; could even win back some of the lecce modellers and have them pulling the load-speakers out of their planes. Anyway, sounds like a great project that could be very popular among scale modellers. Edited By John Stainforth on 06/07/2020 17:08:07
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Jon, Sounds like a great idea, because my standard off-the-shelf model engines seem to be borderline re the 82 db limit. But, I would need to know a little bit more before committing, e.g. - Roughly what would be the weight increase? - If the reduction drive is to be offset from the crankshaft, by roughly how much? - What proportion of the power would you expect to lose in the drive? (This one not so important.)
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By 1965, my brother and I had built a dozen model aircraft. The twelfth was this much modified Mercury Matador, which I think was powered by an AM10 (or was it an ED Bee?). This was a sketch I made of it in 1965. Although it was just a single channel rudder-only model, we got it very well trimmed and could usually spot-land it more or less at our feet. But not always, once we lost it in a thermal, and it ended up going 11 miles (from Nomansland in Hertfordshire) before ending up in a tall poplar tree on the edge of a big estate. It was only because some painters, who were working on the big house with very tall ladders, saw it in the tree - and we had our name and address on it - that we got it back, with only minor scratches.
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For the added weight, calculate the surface area of the plane, convert that to weight (knowing the wt/area of the cloth) and double it, because the ideal ratio of resin to cloth is about 1:1. Glassfibre adds a lot of strength to the surface of the plane, so ideally one should try to reduce the amount of weight in the rest of the structure. Admittedly, that is easier said than done!
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Richard, I beg to differ on how aircraft turn. With a well-coordinated turn that uses both aileron and rudder, there is no lateral slip of the plane either in or out of the turn. With an aileron only turn, a plane generally tends to slip out of the turn, so there is certainly no weathercocking into the turn. The fundamental reason why a plane that is banked (using ailerons) turns is because the lift vector then has a horizontal centripetal component that pulls the aircraft round in a turn; the vertical component of the lift is reduced, hence the need for coordinated up-elevator to increase the angle of attack and thus lift. With a rudder only turn, the yaw slightly increases the speed and lift on the outer wing, as you say, but this is pretty ineffective. In the context of this discussion of dihedral, the main cause of a rudder-only turn is the increased angle of attack of the outer wing and reduced angle of attack of the inner wing. Single channel, rudder-only models were given very pronounced dihedral more for this reason than for stability.
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Martin Simons pretty book is marred by many typos and incorrect equations. (It is hard to believe that my copy is a fifth edition.)
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Jon, you definitely should paint up several test pieces for your fuel-proofing. (Klass Kote is a superb paint, but it is very aggressive on almost anything else.) I had four failures with test pieces with my S6b before I found something that worked.
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Aliphatic resin is my general purpose glue (in place of PVA, which I used to use a long time ago). CA for speed and tacking balsa sheet down, although I don't actually like it very much - rather unpredictable, except in its ability to glue skin! I often use both aliphatic resin and CA together, on the different parts of the same assembly. Aliphatic allows me to move things around a bit to get the alignments dead right, then CA to lock the parts in place - instead of pins. Epoxy for all ply and control surface pinned hinges. I like to use so-called half hour epoxy rather than the five minute stuff. I find the working time of the latter is often too short for me. Preferred brands are Deluxe and Zpoxy, for the aliphatic resin and epoxy. Poundland for CA, which I find just as good, if not better than the hobby-shop brands - and vastly cheaper. Have also tried many other glues, such as Superphatic, which seems good, though I'm not yet won over by it.
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Thomas. I have had the same experience with a Saito 125 for ten years in a Hangar 9 Funtana. I also use a 16 x 6 prop and 12 to 15% nitro fuel. The engine is side-mounted with a Pitts-type muffler. The piece of fuel tubing I have on the breather nipple is about 15 cm long, and I have never had a issue with that. Indeed, I hadn't realised that there was any issue with the length of the breather tubing.
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Forum members' new models: Let's see them.
John Stainforth replied to Paul Marsh's topic in All Things Model Flying
Beautiful plane, Eric. What is the size, what is the powerplant? -
What size to print plans without a scale tab
John Stainforth replied to Rogeo1983's topic in Scale and Semi-Scale kits
This is a scale model of a full-size plane. Just get the specifications of the full-size and go from there. -
Posted by Andy48 on 18/06/2020 15:10:12: Posted by John Stainforth on 18/06/2020 15:05:16: In the club I belong to in the US, it is mandatory to arm electric powered models on a special bench close to the flight line, and nowhere else. You still have to carry a live model from the bench to the flight line though. This area close to the flight line includes the (mandatory) starting benches and bays for i.c. and turbine powered aircraft, and has a model taxi track down the centre. This track has a big red line across it, on the side away from the flight line, saying "NO TAXY BEYOND THIS POINT" and then continues to the covered work bench area, which is 20 yards away. So the whole start-up area and taxy way are regarded as a "live" area where only pilots and helpers are allowed and extra care should be taken.
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Posted by Andy48 on 18/06/2020 14:59:03: Never had a problem. All my planes are electric, and most are fitted with an arming plug which doesn't get inserted until the plane is on the flight line, and is removed before leaving it. The rest, small foamies have an almost foolproof arming switch on the transmitter which cannot be accidentally knocked on, like MattyB and Tim. Electric can be made very safe with a bit of care. In the club I belong to in the US, it is mandatory to arm electric powered models on a special bench close to the flight line, and nowhere else. I also think that wearing safety goggles should be encouraged, if not enforced, when starting larger engines, in case a prop should throw.
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...a.k.a. bangers and mash!
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There are 40's and 40's. e.g., the OS 46AX seems to produce about twice as much as power as the 46LA.
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Thanks for the advice. If the Xoar 18 x 8 is still too loud in the plane, I will get a Menz 19 x 8. ps. With the two Laser threads running concurrently, I forgot which I was on! Edited By Steve Hargreaves - Moderator on 16/06/2020 21:48:13
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MikeT, Yes, the Pitts mufflers I have used on several Saitos are Slimline mufflers, which I bought in the U.S between 10 and 7 years ago. I see now that they are very expensive (probably about 100 quid) and they have recently had availability problems because of Covid19. You have to specify whether the muffler is for inverted or side-mounting. I see that there are also versions that incorporate smoke generators, so that might justify the cost, if you are into smoke. Googling suggests that Probuild-UK might carry Slimline mufflers, though they don't seem to be listing any at the moment. Otherwise try Ebay etc. But I suppose, at the price, you might as well see if you can get your Saito muffler to work for you first, e.g., by using the highest possible mounting temperatures and high temperature thread locker. You might just be lucky! Another tip: even if you don't use an additional mounting bracket, belay the muffler to the plane with a piece of flexible braided wire so that if it does come off you can't lose it altogether! (Mufflers seem to have a habit of falling into long grass.)
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Engine doctor, even when one runs the engine right up to full running temperature before tightening the nut, the silencer can come loose. What I have found is that if one leans the engine just a smidgen too much, e.g., during tuning, the pipe comes loose - I suppose because the temperature goes up and the problem of differential thermal expansion gets worse. (I also had the same problems with the Saito 180. Unlike the other Saitos, its a vicious engine and I don't like it.) Getting a different type of muffler is an expensive option, but it sure saves a lot of hassle.
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Engine doctor, even when one runs the engine right up to full running temperature before tightening the nut, the silencer can come loose. What I have found is that if one leans the engine just a smidgen too much, e.g., during tuning, the pipe comes loose - I suppose because the temperature goes up and the problem of differential thermal expansion gets worse. (I also had the same problems with the Saito 180. Unlike the other Saitos, its a vicious engine and I don't like it.)
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I have had this problem on several Saitos, the worst being the 125 (which is a favorite in all other respects). I finally fitted the engine with a Pitts style muffler - end of problem. Edited By John Stainforth on 15/06/2020 22:57:59
