Albert Ace Posted September 17, 2023 Share Posted September 17, 2023 Chaps As above. But never built one, and its going to be Glow powered. Choice of OS 70 surpass, (fitting in looks difficult) or OS 56 alpha, again four stroke, but easier to fit (i think) I know they need a forge in the nose to get the balance right, so maybe the 70 but ?? Thoughts, suggestions, all help appreciated. Albert Quote Link to comment Share on other sites More sharing options...
Jon H Posted September 17, 2023 Share Posted September 17, 2023 Use the 56 and a 13x5 or maybe 14x5 prop. My dad's Pup flew on OS48 and then 52 4 strokes with no problem at all. Yes it carried a lump of lead, but the model was still plenty light enough for the 50 class engine to do the job. These models fly much slower than most people expect (so they fear a stall much earlier than it will actually occur and fly flat out) and i think this is why there is a tendency to over power them. With a 56 fs and the fine pitch prop i recommended before the model will not be fast but will have good thrust for loops etc. As its a pup, it should not be that fast and these really do excel when flown slowly. A slight headwind will offer landings at barely walking pace once you learn to trust its low speed handling. The flair fokker DVIII is the same way and i flew one with an ASP52 fs without any trouble at all. I have flown customers examples of the pup powered by the laser 70 and found them unpleasant to fly as i was barely off idle much of the time and just a touch on the throttle had the thing accelerating like crazy. They did all comment on how slowly i flew it compared to how they would fly it and couldnt understand why it hadnt fallen out of the sky. My dad moved his firewall back about 3/4 inch to get the engine in the cowl. The engine is inverted and balanced a little forward of the marks on the plan if i recall correctly. I have a beaten and battered example that i picked up for 20 quid at old warden last year and it will be getting an equally battered os52fs when i eventually get around to repairing it. Quote Link to comment Share on other sites More sharing options...
Maurice Dyer Posted September 17, 2023 Share Posted September 17, 2023 Thanks Jon, you have reinforced my own theory. Thank you.. Quote Link to comment Share on other sites More sharing options...
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