stuey Posted October 19, 2011 Share Posted October 19, 2011 Hi chaps, bit of advice sought. I am flying my Kyosho Mustang 40 with a year 2000 odd vintage SC 52FS with an APC 12x6. It is turning about 8500rpm, which seems a bit down on previous readings from my rpm gauge. I am however getting a bit suspicious of the readings I get from it as they do seem to vary day to day, but thats another story. It flies well enough, but it would be nice to have a little more speed. I am thinking of trying a 11x7 for a bit more pitch and hopefully a little more rpm. Good idea?? Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 19, 2011 Share Posted October 19, 2011 TBH I tend to go the other way and put large diameter props on because I'm a vain so-and-so and I think they look better On my Pitts which has an OS56 Alpha upfront for example I use a 13x6. THis is good for a aerobatic model as OK its not fast but it has a lot of pulling power - good for stall turns, loops and bunts etc. An 11x7 would certainly give you more speed but I'm not sure you would get significantly more revs - but hey what does that matter? I think folks get a bit too hung up on the speed of the engine - as long as you are on, or about, the peak in the power curve at WOT, 500rpm here or there makes little difference to the average model. Having said that 8,500rpm is a little low for that size engine with a 12x6 prop - which is hardly pushing things prop-wise. I assume you have tried all the usual stuff, throttle opens fully - when running! I have seen a few engines where the throttle opens OK when the engine isn't running but then "binds" short of fully open when it is running. BEB Quote Link to comment Share on other sites More sharing options...
stuey Posted October 19, 2011 Author Share Posted October 19, 2011 The throttle is set up fine, I suspect the carb is not as its best although I have renewed both needle O rings. The rocker cover is leaking mess like my ASP 61 so I will check the tappets while I'm at it. I am contemplating replacing the carb rather than try to rebuild it, but as I bought the engine around 2000 I'm not sure the series 2 version of the carb or whatever it is now will fit. The main needle seems a little loose, I have read that people have used a bit of fuel tubing over the needle housing joint to seal it but I cant see how that will work as the ratchet tab is there?? Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted October 19, 2011 Share Posted October 19, 2011 On my "Ruperts Dad "SC52fs powered ,(the nearest machine I have to 3-D designed for a four stroke),I started with the usual 12"X6 "black Master prop & then followed it with 12/1/2" X 3& 3/4" APC .Incredible difference ! Acceleration phenominal at TO & lowish airspeeds & braking effect also .Depends what you want doesn't it .? I'm in agreement with BEB --The bigger the better -Diameter that is .One can choose the thrust factor with the pitch.Never mind the rpm. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted October 22, 2011 Share Posted October 22, 2011 I use a 12x8 or a 11x8 on a 52 FS. Seems to be right in the power range. Quote Link to comment Share on other sites More sharing options...
stuey Posted October 23, 2011 Author Share Posted October 23, 2011 I seem to have solved the problem. Just before I flew it last, I moved the engine back on the mount about 5mm. Somehow when I built it over 10 years ago, the gap between the spinner plate and the cowl was far too big. Although I am normally very careful about setting up the throttle linkage, I forgot to readjust it. This meant I was getting to around 3/4 throttle, which would probably explain the lack of revs!! I have been out this morning and retuned the engine, now getting a safe 9200rpm which is most likely the bit I have been missing. A lesson learned my me!! I will fly it again and see if I feel the need for any experimentation on the prop front. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 23, 2011 Share Posted October 23, 2011 Ahem! BEB Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 23, 2011 Share Posted October 23, 2011 I use a 12 X 6 or even go down to 11 X 6 on my SC 52s. Quote Link to comment Share on other sites More sharing options...
Kev Bamber Posted October 23, 2011 Share Posted October 23, 2011 My ASP 52FS shows around 9600rpm on an APC 12x6. Kev. Quote Link to comment Share on other sites More sharing options...
JC Posted November 22, 2011 Share Posted November 22, 2011 I use a Graupner 11x6 on an SC 52 fs fitted to my Travel Air. I have no idea with regards to the rpm but it gets off the deck in about 20 feet and I'm seriously worried that it might pull the wing off. Not overly helpful I know but it makes me smile. Quote Link to comment Share on other sites More sharing options...
stuey Posted November 23, 2011 Author Share Posted November 23, 2011 Unfortunately after my last post where I thought it had settled back down ok, it was back to rubbish again. Nothing had changed, and couldnt get it over 9000 rpm again. I have solved the issue by buying an OS FS-62V . I will probably go back to it another day, perhaps put it in a model with lesser power needs. Perhaps the engine is now a bit tired, which hasnt taken very long running time wise as far as I can remember.... Quote Link to comment Share on other sites More sharing options...
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