Martin Harris - Moderator
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Posts posted by Martin Harris - Moderator
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"I don't see the problem with what it is called Martin."Neither do I but it seems to be a major problem to some of the thread contributors!I don't know how accurate it was, but it was once an often quoted "well known fact" that according to aerodynamic principles, a bumble bee was incapable of flight. A perfect example of your last point!
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Quote: "I know the term 'semi-symmetric' is locked in modelling yore, but it is a nonsense term, something is either symmetric, or it ain't, and if accurate exchange of information is the goal, then we shouldn't use nonsense terms, specially with single interest subjects."
Perhaps we should rename semi-symmetric as nearly-symmetric? -
Odd - you seem to be well past it!
(says 130 on your ID - or have you been very busy since 13.41?) -
Kevin,You're a lucky so and so to have such an interesting lump to play with!Why don't you download the OS manual for their 5 cylinder radial...which I suspect will be very similar? Page 15 seems relevant...the nipple is a drain plug and should be in place for running.I suspect (never having been lucky enough to own anything like this) that the idle mixture may be grossly rich, giving a slow transition. Probably not helped by the volume of the common induction chamber that I suspect your engine uses?
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Hi. I have a FS400AR SC radial in my ¼ scale Stearman.
The instructions that come with the engine leave a lot to the imagination (literally) it has an on board glow system powered by a 13000mah NiMh which dose the job very well.
My problem is that I still can not get it to run smoothly. The idle is reasonable but takes 2-3 seconds to pick up when the throttle is opened. The top end is lumpy. The needle is open 1 turn and if I open it any more it runs too rich and if I close it any more it runs to lean and dies. When I say open / close Im talking 1/8 turn.
There is also a breather nipple on the bottom of the engine. By all accounts following standard 4 stroke logic this should be open. If I leave it open it turns into a leak and fuel /oil goes every ware, the engine will not start. If I close the nipple the engine starts perfectly and runs as above but oil leaks from the push rod covers. When I open the nipple after a run I get an abnormal amount of oil from the crank case.
The fuel I am using is 10%nitro, 18%oil the rest methanol.
Any one had the same problem or any suggestions.
Regards
Kevin.
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As an ocassional flirter with the dark side I'm not really qualified to comment but I've had reasonable results and some of my more electrified friends swear by it.
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It's the sound that gets me - if you listen to the video carefully you can hear the skis slithering across the snow - even better in real life. Acceleration to take off can be done in an instant as there's virtually no resistance from the ground but it's far more fun to let it run on the skis for as long as possible.As I said in my last post, I've ignored the advice from the link re. my articulating mechanism but it is a very elegant solution which I may well adopt in the future. The articulating skis worked even better than last Saturdays experiment with fixed skis - the sliding turns on the ground, for example, wouldn't have worked. Even though the skis are fairly short, they rode over footprints etc. very well.
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Timbo,Thought you might like to see what the "Southern Softies" were up to in the snow today...never go out when it's below 10 C indeed !!!
I'd like to point out that it wasn't me flying in the clip - I'd handed the Limbo Dancer to one of my mates for this one....and sorry about the film quality - it was taken on a mobile phone (don't tell the committee I took it onto the flightline!) and it was snowing quite heavily.
Despite the advice on the link in the post above, I found the modification since the picture of the skis involving rubber bands and restraining links to allow the skis to float worked extremely well on the icy snow (compacted/melted from @7 inches on Saturday to @3 inches today. )
Brilliant fun and well worth the effort of making the skis - I can only recommend making some even if you're not expecting any more snow as you'll have them for the next time!
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It's all a game, really...she tells me it's something she's had in the wardrobe for years or an absolute bargain in the sales and I tell her it's a model I've had in the loft for years or a kit I picked up at the last bring and buy...She knows that I know and I know that she knows but neither of us lets on that we know that the other knows that we know what they don't think we know.And I need engines and radio gear to go with the models like she needs shoes and handbags so it's honours even..
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I asked 'er indoors whether it was OK for me to tell everyone that I'm the boss in our house and she said, "Fine, if you think it's a good idea."
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Actually, I think I lied about the 3DD - on reflection it was a large CAP with a Zenoah 62 (petrol) owned by the same person...but it's interesting that Richard has witnessed icing on a glow engine.
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Richard, you won't get any arguments from me about icing. I've seen it on cars and it's killed plenty of full size pilots although I'm not sure if alcohol based fuels are as prone to it as petrol - is there any INFORMED opinion on this?Once again it's worth reminding people that carb ice occurs in temperatures well above freezing due to the expansion of the fuel air mixture in the venturi.As an aside, a year or so back, during some good icing conditions, a very well powered 3 Double D (Moki 180) failed to get away from a touch and go and the prop had a thick layer of impact ice on it when retrieved which obviously affected its efficiency. As well as this there could be a strong possibility of carb ice in the conditions so next time an engine doesn't perform as expected in high humidity and reasonably low temperatures it could be something to think about.John, that's a really interesting theory which certainly deserves some thought. However, wouldn't the effect be noticed most during flight as the water concentration would be at its highest?
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Thanks "flytilbroke" - to make it easier to visualise for the sceptics, another way of looking at it is that an gram of water is equivalent to 20 drops. 20 drops in 73 gallons of air at 100% (absolute) humidity at 30 degrees C gives less than a third of a drop per sealed nearly empty container if all the water is absorbed by the methanol.
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It's leaving the top off that's a no-no...
Not having even a gallon of air in a closed container and a dribble of fuel will make any significant difference. -
Quote:
I`m might try the Bushwacker 20% larger,
any ideas for a name ?
Colin.How about Obamawhacker? -
Mine never lasts long enough to deteriorate!If you habitually leave the top off there could be a problem but the amount of water held in the volume of air inside even a substantially empty container is insignificant. For example, even at the worst case humidity conditions (if my sums are correct) you'd need 73 gallons of air to hold one gram of water. Of course, with air changes and condensing conditions you can then extract considerable amounts......so, I'd advocate replacing the cap between uses at the field (or better still using a cap which has nozzles to attach the pipes to and allows a sealed system between uses which will reduce all forms of contamination).Nitromethane will deteriorate in direct sunlight but is largely stable once mixed with methanol so that shouldn't be a worry in normal circumstances.
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I remember feeling rather upset several years ago (when I was about 14) when the tissue covered wing that warped after I'd doped it burst into flames like a latter day Hindenberg while trying to take the warp out in front of an electric fire. Luckily the house didn't follow suit...Don't know about the rest of you but my builds are littered with so many little *!!*££! moments that it's not easy to pick one out but one that comes to mind is when I went to great pains shaping and pre-covering the opposite handed cheek pieces to fit over the backs of the engines on the Slim Twin in my avatar - I always dread building 2 left wings etc. - and with a smug glow of satisfaction that I hadn't made the obvious mistake of making them both the same, I went to glue them in place. It was only then that it dawned on me that despite the fact I was working on left and right fuselages they were supposed to be identical with both engines pointing the same way...doh!
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A bit off topic but the moderator has made comment earlier in the thread - Brian, did you get the - Sorry, but you need to pass a thread id into this page.- message when you tried to post? I seem to get that when I post from my work PC (using IE) but not from my home one on Firefox...
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An old chestnut but true, nevertheless...measure twice, cut once.Really, the only way to learn aeromodelling is to get on and do it! Pick something that interests you but is fairly straight forward to build and fly. The 1/4 scale Constellation can wait a while!Spend a LONG time poring over the plans, visualising the construction and building it in your head before starting. Talk to clubmates - most of the insoluble problems will have been encountered by them before - although I've seen the most experienced modellers scratching their heads over some plans.If the designer hasn't made things clear it may be worth trying to contact them - most are only too pleased that someone is interested enough to be building their design and will be delighted to assist.And don't forget a note of thanks to him and a short report on the finished article!When you start building, don't lose heart when you make a mistake. There is virtually nothing you can't undo and/or remedy with a little thought and it is these moments that provide you with the basics of being a model builder. Don't hesitate to ask for help either locally or on the forum. There are very few real modellers who don't enjoy helping others.
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120 and 180 have both worked well for me. Excellent starting and reliable (but I have always used an onboard glow for peace of mind as they are inverted).As far as I'm aware, the only difference between ASPs and SCs are the letters cast into the crankcases and the boxes they come in.
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Now I've worked out the "approved" method of uploading photos:
No science with the tail end - just the longest bit of thin ply I could find - sealed the ply with thinned 5 minute epoxy 15 minutes before going flying!Worked a treat in 6 or 7 inches of powdery snow with a slight crust as long as the tips were kept out of the snow - next thing to try would be springs to keep the noses as high as possible as in some of the other postings to allow "normal" landings instead of harriering it...
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Seeing as you've shown me yours I'll show you mine!
This is a bit of an evolution, hence the rather poor finishing - the original scale support block broke (although I've just remembered from the plan extract above that it was something I added myself at the build stage) so I made a replacement to go over the existing piano wire - hence the aluminium U plate to stop the slot (end filled after assembly) splitting out.The bar over the horizontal cranked bit is held by 2 screws covered in silicon tube which allows slight movement to enhance steering with the essentially fixed tailwheel - a field mod. when flying at our German "twinned" club's annual display in a vicious crosswind was (a) nearly impossible and (b) potentially extremely embarrassing with the fully castering wheel!The oleos were standard items from (I think) Ripmax and weren't more than about £20 for the pair (2003) unfortunately I can't see them on the Ripmax or Perkins websites but a model shop might be able to help.
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Since when did the French ever care about abiding by EU rulings or standards? Mind you, we seem to be the only country that blindly adopts every bit of EU legislation however stupid or irrelivent it may be...
Tomorrow doesn't look too bad eh?
in Flying Field Reports and Chat
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