John Stainforth
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Posts posted by John Stainforth
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I agree with water, oxygen, and nitric acid being corrosive. Is the "it" you refer to alcohol (methanol or IPA)? Surely that doesn't last long enough absorb water and start the pitting process. Most light alcohols evaporate in minutes at room temperature if exposed to air. You have got me worried, because I have used exactly the same method as the Mike Watters asked about: IPA followed by after-engine oil. As far as I could see, the IPA acted as a superb solvent to wash away all the other organic compounds, and the remnant IPA evaporated off in minutes. Then I applied light engine oil.
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Surely isopropyl alcohol, or methanol, can't be the problem with corrosion of bearings, because it evaporates so fast? I've damaged bearings with bad oil, specifically bicycle oil.
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I think it pays off to do it exactly as OS say. (Manufacturers of most things usually know more about their products than anyone else.) All this takes quite a bit of time and fuel. Ditto with the mixture control valve.
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I would be tempted to put strips of sheeting half way down the fuselage sides, between the middle pairs of longerons; or, if that is going to spoil the scale look too much, a zig-zag of diagonal struts along the fuselage sides, between the formers on the inside of the longerons.
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Jon, you are right about American pilots liking their power! In the club I belonged to in Houston, they would invariably put in bigger engines rather than add nose weight. One of the best pilots there (actually, probably the best model pilot I have ever seen - his landings were 10/10 absolutely every single time) was a full size pilot flying 737's for United. I think he liked to do everything with his models that he was not allowed to do in airliners. His buzz was taking standard 60-size trainers, beefing them right up, and putting in multiple engines. The first of these had two OS 90's; that flew really well and like a bomb. Then he built another with four OS 55AX's. He gave that a broader tailplane (sorry, horizontal stabilizer) with two outboard fins (vertical stabilizers). That flew and looked a bit like a Mach 2 Lancaster. It's rate of climb was phenomenal - and those four engines made a beautiful sound.
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I am going to be watching the behaviour of the virus very carefully around that date. It has shown scant regard for these man-made dates on all previous occasions.
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I would test any combinations before trying them on a model. Many plastic paints and plastic films are not very compatible with each other. Epoxy paints, which are excellent in many respects, don't adhere well to many plastic films. (For example, certain plastic films make good separating layers during priming or painting to prevent epoxy sticking!)
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The member's score is simply the number of "likes" the member has received, which partly reflects the amount of entries the member has contributed to this forum. But calling it a reputation"?: I think that's a misnomer. Newcomers to the forum, who don't know its basis, may think it really is some objective measure of a member's reputation in the aeromodelling world.
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5 hours ago, john stones 1 Moderator said:
Mercury Matador O.S 10 in, made a pigs ear of it and wings folded, hit the only piece of concrete in sight, and obliterated itself.
Snap. In 1965, my brother and I built and modified this Mercury Matador for single channel. It flew really well, including one uncontrolled 11 mile flight! It did many flights over a two year
period and never crashed. I gave it to a younger relative when I left home for university. I think it was powered by an AM 10 (1 cc).
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On 05/03/2021 at 15:12, Chris Walby said:
JS, IMHO I don't agree, one sniff of an issue and (not me) people panic and stock up. Some time back one of the ic manufacturers stopped production and another manufacturer got a bunch of enquires about buying spares for engines the person didn't have (ebay resale on the cards at a inflated price no doubt).
Its like Ron posting SLEC have balsa in....Tina at SLEC will be be processing a load more orders as a bunch of people think its a good idea to stock up again...just in case.
Its deep in peoples nature to not want to miss out...Salesmen have been exploiting it from the dawn of time
What I meant to say is: I keep a stock of balsa - enough for another plane - by topping it up in dribs and drabs (e.g., when I go to model shows). Yes it's human nature to protect one's own supply. But it is not the same as panic-buying.
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What is the difference between the blue dot and the star?
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I think most modellers will not be panic buying. Now that a new supply line has been achieved it is likely to be sustained, even if at an increased cost. Also, most people who scratch build are not doing it to save money. They do it because it gives them more satisfaction than buying of the shelf. And they buy in dribs and drabs, so the cost is hardly noticeable.
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Gary,
Great work and tips. I use the same procedure as you for joining sheets, but (although I am a massive fan of white glue - aliphatic resin in my case), I find CA ideal for this task. I sheets don't buckle at all, and by the time I have lightly sanded the joints, they are almost invisible.
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The Victorians used to put deliberate errors into their works, because they regarded it as sacrilegious to be perfect!
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4 hours ago, Jon - Laser Engines said:
I would use klasscote, but i cant get confirmation that it will not eat my enamels and its too expensive to take a punt on and give it a try, only to find its no good ?
KlassKote is superb, but it is aggressive and probably will eat your enamels. Phil Clark does reckon it is possible to spray KlassKote on top of enamels, if this is done with a very light spray coat and the enamels have been left to harden for many days. But I did not manage to do that successfully on enamel lettering, probably because I don't have Phil's years of experience doing that. When I screwed up my enamels, it was on a separate test patch, thank goodness. I think the golden rule is to always test every single new paint combination on a test patch, before committing to a plane! On my next plane, I think I will use KlassKote right through, even if it is expensive - I think it is worth it.
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1 hour ago, Geoff S said:
You should be aware that cycle control cables (gears or brake) are coated and will need to be cleaned if you wish to solder to them. Probably better to buy uncoated Bowden cable from (say) Prime Miniatures. I would use 3mm carbon tube, which has a 2mm hole and glue in 2mm threaded rod with epoxy but Bowden works OK in tension, perhaps less well in compression (ie pushing)
Geoff
3 mm carbon tube with 2 mm ID was exactly what I used, and I was pretty pleased with the result
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2 hours ago, PatMc said:
John, I don't see that this has any bearing on my post that you quoted.
Any slop contributed by the snake between the anchor points is caused by the amount of lateral movement the inner cable can make within the outer tube. The amount of lateral movement possible is identical whether the outer tube is supported at points between the anchor points or not.Snake control linkages are suitable for the great majority of sport models but if you want minimum slop control linkage forget about snakes. Servos positioned close to the moving surface using short push rods, suitable dia (depending on likely control surface loads) longer carbon fibre pushrods or a pull-pull system are all superior to any snake linkage.
I used to use Kavan outers from my LMS matched with close fitting metal inner cable obtained from a cycle spares shop. These were the "least slop" snakes I ever used.
There are other ways of minimising control slop, including utilising the max available servo movement, servos rigidly fixed without grommets & avoiding plastic control horns etc.
What you say is true, if the outer tube can not stretch.
Unfortunately, in my scale model, a pull-pull system would have been difficult to access and there was no room for (hidden) servos in the rear of the plane, so I was more or less forced to use snakes.
Thanks for the cycle cable tip. I wonder if that would be any better than the carbon rod I have fitted.
It is a good general tip to always use the full servo movement, and I always do that (at least 100%, if not 125%).
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On 31/01/2021 at 23:24, kevin b said:Posted by John Stainforth on 31/01/2021 22:51:59:
I've got a large box of balsa bits. I suppose I could start a new currency called Bitbalsa.
Yes, but will you be able to split it to 8 decimal places ?
It's already in bite-sized pieces!
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I think whenever I have had a prop throw, the culprit has not been the prop nut(s) but the screw holding on the front casing of the spinner. If that comes loose, the electric starter twists the spinner housing against the prop and the extra leverage on the prop then undoes the prop nut(s). At least, I think that's the problem.
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28 minutes ago, Martin Harris - Moderator said:
As I mentioned earlier, a Z bend at one end prevents rotation but there is the possibility of vibration fretting threads and a lock nut protects against this.
I use the lock nuts, plus a dab of glue, not so much to prevent rotation but because the screw fittings are often a very sloppy fit in the metal clevises. The nut stabilises the whole thing, preventing it from flexing from side to side (which could lead or unwanted or even catastrophic wear).
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13 hours ago, PatMc said:
So long as both ends of the outer are securely anchored I don't see how it makes any difference whether the length in between is supported or not. It's the two exposed parts of the inner is that's doing the work, the rest of the inner can only be the same length as the outer whether it's loose or supported between the anchor points.
If a fuselage is roomy enough I use push rods or pull - pull for the elevator & rudder. I usually only use snakes when the rear fuselage is narrow such as a glass fibre glider fuselage. In most cases supporting between anchor points would be impractical. When I do use "snakes" I prefer metal inner with plastic outer. I silver solder a metal clevis on the control surface end with length adjustments catered for at the servo end only.
That's what I thought at first, but the reality proved me wrong. It does not take much slop in the pushrod system to create quite a bit of give in the control surface. A 5 mm throw on the TE of the surface might correspond to about a I mm throw on the horn, and if one is using a 1 m (order of mag) pushrod, that can be achieved by only about 1/1000th change in the length of the rod. First, I checked the outer sleeve and found that I had secured this very well all the way along, so it did not seem to be the problem - it had to be in the pushrod itself. The minute slop in the holes in the servo arm and control were contributing to the unwanted movement in the surface, but only to a small degree. So the culprit was definitely the pushrod of the snake. I am a big fan of Slec products, and whilst they are simple and practical they are not exactly precision engineering. The Slec snakes have quite a lot of slop between the OD of the pushrod and the ID of the sleeve, and the pushrod is rather flexible. When the pushrod is relaxed (control surface neutral), it adopts the shortest (straightest) path inside the sleeve. But when a counter force is applied to the control surface, the pushrod is put into compression and its flexibility allows it to conform to slight curvatures of the sleeve. Worse still, because of the sloppy fit of the pushrod, it can cross-over from one side of the sleeve to the other, following the longest possible path. (I am using very exaggerated terms here to make the point; in reality, these movements are very small.) I suppose once the pushrod has taken up this longest possible path (effectively shortening its length) it has nowhere else to go and with sustained compressive stress the plastic of the pushrod itself can then compress slightly. The carbon fibre pushrod, I used as a replacement for the plastic one, was a better fit inside the sleeve, was also much less flexible so could not flex and buckle so much, and is also much less compressible.
Does anyone here know if there are better quality snakes on the market than the Slec and Sullivan ones? I would be prepared to pay more for quality here, because once a snake is built into a fuselage it would be very difficult to change out later.
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On my S6b, I used a snake for the rudder and anchored the outer tube at both ends and about four other places down the fuselage. I didn't find out, until I had completed the model, that there was more give in the rudder (when pressed sideways) than I liked, so I replaced the inner plastic push-rod of the snake with a carbon fibre rod of about the same diameter. This is quite a lot stiffer than the plastic and resulted in far less "give" of the rudder. So you might bear that in mind, if you have similar problems.
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How's that?
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The web designers have done a great job with the new site. After a few minor problems and minor complaints, the designers have responded very rapidly to put these right. I think it is now beyond dispute that the new site is an improvement on the old. Well done!
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Stabilisers. Are they helpful in learning how to fly? What is the opinion of instructors and trainees?
in Beginners
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Pilots of full-size aircraft always move the controls in same directions relative to the direction they are facing, which is the direction of flight. This is so ingrained into them that they find it really hard to learn the control reversals when a model plane is flying towards them. But, from what I have seen in the US, pilots who learned to fly model planes before they took up full-size flying, make superb RC pilots.