Ashley Hunt Posted July 13, 2022 Share Posted July 13, 2022 Hi, I’m about to start building an SE5A and when I bought the kit I also bought an OS FS40 Surpass for it. I’m now thinking that the OS engine might be marginal in terms of power, especially since I don’t seem to be able to build a light model. Has anyone any experience of a Flair SE5A with a 40 size four stroke ? Quote Link to comment Share on other sites More sharing options...
Martin Arnold 1 Posted July 13, 2022 Share Posted July 13, 2022 From what I can gather that model will come out around 6-7lbs auw, in which case a 40 Surpass is very marginal to say the least, would have thought you are going to need at least 56 - 82 size four stroke. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 13, 2022 Share Posted July 13, 2022 Mine had an OS .61 Fs in it,(1988 ) when the top wing literally fell to pieces with the oily firewall I flew it as a low wing monoplane with an os .48 Surpass . I currently have a 'greeny brown second hand one I bought the same size, maybe a Ripmax artf, with the same engine in it, the OS .40 Surpass won't be enough. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 13, 2022 Share Posted July 13, 2022 (edited) you need an absolute maximum of a 50. I fly a flair nieuport of 5lbs 13oz on a saito 45 which i have brutally over propped and yet it still wafts along at half throttle. My model is just a smidge under the 6lbs flair recommend and i see no reason for your se5a to be any different. If you have the 40 available i would use it and if you find it needs a little more then pick up a 50 fs at a later date as i think the mounting pattern for the bolts is the same. With a model like this you fly using the wings and not the propeller. I have people calling me asking for our 70 and 80 for this and the larger pup and DVII in their range and, frankly, its just madness. My dad taught me to fly on the pup using an OS 48fs and then 52fs when the 48 died. I flew the DVII on an ASP52 and found it more than adequately powered for scale performance. My Dad is also building an se5a at the moment with a saito 45 in hand for that, and he flew the smaller triplane they did on the os 48after it was fixed and the 52 was in the pup. A club mate had one with an asp 52, it flew lovely, another 2 club mates had the hobby king 55 inch se5a and they were very well powered with 52's, another flew the dennis bryant (i think) of about 55 inch on 52 and that model was heavy but flew fine. I have 2 40 os 4 strokes, one wrecked old fs and one surpass. I might dig the surpass out and run it as i am sure it will run a 12 or 13x5 prop at more than enough rpm to satisfy the se5. In fact, one of these engines is destined for my sfm se5a which is only a little smaller. Honestly, less is more and unless you want to turn it into a pitts special on steroids stick with a 40-50 engine. Edited July 13, 2022 by Jon - Laser Engines 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted July 13, 2022 Share Posted July 13, 2022 My dad had one with a 48 fs in it. Was about right for power i believe. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 13, 2022 Share Posted July 13, 2022 My Flair SE5a flew just fine with an OS48 4-stroke in it. For the past umpteen years though it's been powered by a Graupner Compact 390 motor on a 5-cell A123 battery pack. Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted July 13, 2022 Share Posted July 13, 2022 (edited) There's a tendancy to assume that unless a model flies like an overpowered WOT4, takes off in 2 yards, climbs vertically out of sight and "hauls ass" then it is underpowered. There is absolutely no need to overpower a model like an SE5a, especially if you want it to fly like one. Pretty much every Flair Se5a I have seen or flown is happiest with a 52 size 4 stroke at most. Decent diameter, low pitch, wide bladed prop and you don't need a 1:1 power to weight ratio, that's what wings are for. Takeoffs can be longer than 10 yards, it's quite nice actually to fly scale and "on the wing", especially when there's a lot of wing area as with the SE. Edited July 13, 2022 by Matt Carlton 3 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted July 14, 2022 Share Posted July 14, 2022 the Os .48 Surpass gives ( engine tests) 9.700 on a 12 x 6 and 10.150 on the Os .61 not a lot of difference but you could make it work by putting a proportional servo on the throttle.🥳 Quote Link to comment Share on other sites More sharing options...
David Davis Posted July 14, 2022 Share Posted July 14, 2022 If it's of any interest or value, I had a Flair Baronette, the little triplane in Flair's scout series finished in the colours of Hans Weiss, one of von Richtofen's flight leaders. An OS 40 Surpass powered it perfectly. 2 Quote Link to comment Share on other sites More sharing options...
Ashley Hunt Posted July 14, 2022 Author Share Posted July 14, 2022 Matt, when you say a decent diameter, low pitch, wide bladed prop, what sort of size are you suggesting ? Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 14, 2022 Share Posted July 14, 2022 12x5 should be no bother for it. Even a 13x5 might work depending on the brand as some props run faster than others. I have a turnigy 15x5 on my saito 45 and the poor thing is flat out at around 6000rpm. Its a gross overload but the engine carries it well. I have run my ruined 40fs on a turnigy 13x5 and it ran well, but the turnigy props do run fast. I will dig out my 40 surpass and run it up. Its been a while and it will be a nice little job for this afternoon/tomorrow. Quote Link to comment Share on other sites More sharing options...
gangster Posted July 14, 2022 Share Posted July 14, 2022 SC52 FS worked well for me. I suspect in terms of power to weight even a 40 would be way more than the real thing had back in the day. Quote Link to comment Share on other sites More sharing options...
Eric Robson Posted July 14, 2022 Share Posted July 14, 2022 I built the Flair Se5 when the kit cost £45 and put in an OS 40 two stroke, it flew like a demented Pitts. I replaced it with an OS 40 Surpass and it transformed it into a well mannered aeroplane. I flew it regularly for 7 years till a faulty servo brought it's demise. I have another one now which has flown a lot on electric set up but I am going to fit a four stroke in for longer flights and better sound I have a new 40 and a well used 52 I will try the 40 first and see how it turns out. 1 Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted July 14, 2022 Share Posted July 14, 2022 5 hours ago, Ashley Hunt said: Matt, when you say a decent diameter, low pitch, wide bladed prop, what sort of size are you suggesting ? 12x5, possibly 13x5, maybe even an APC 13X4W, the point being that a larger prop spinning at a reasonable rpm is better on this kind of model than a smaller one rotating faster. We need reasonable static thrust, we don't need huge pitch speed. With all the drag of the airframe, trying to go quicker isn't going to happen, but we can use a big, low pitch prop for reasonable acceleration and braking at the lower speed bracket it'll be flying in. 1 Quote Link to comment Share on other sites More sharing options...
Maurice Dyer Posted July 14, 2022 Share Posted July 14, 2022 Built two. Weight 6.5 pounds. O.S.52 surpass four stroke, 90 degree manifold from Just Engines and normal muffler. Take out the wood where the plastic radiators get glued on to the front face and make up false rads from 1/16th ply. Will need about 5/6 ounces in the nose. Maury Quote Link to comment Share on other sites More sharing options...
Maurice Dyer Posted July 14, 2022 Share Posted July 14, 2022 Just now, Maurice Dyer said: Built two. Weight 6.5 pounds. O.S.52 surpass four stroke, 90 degree manifold from Just Engines and normal muffler. Take out the wood where the plastic radiators get glued on to the front face and make up false rads from 1/16th ply. Will need about 5/6 ounces in the nose. Maury Oohh... And flies on 12 x 6 prop. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted July 14, 2022 Share Posted July 14, 2022 40FS is very happy on 11x6. So I'd start on 12x4 and see where that gets you. Not much point trying any sort of high pitch prop. It's a slow airframe. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 14, 2022 Share Posted July 14, 2022 Being a curious chap i dug out my 40 surpass and ran it up in the garden on a turnigy 13x5. She gave me a healthy 9200rpm and even though these props do run a little fast we can assume that even a prop from another brand running 1000 rpm slower will still be fine at 8200. Considering the engine has not run in...7 years? i was very pleased with it going on a flick start almost immediately. Quickly tuned up for the new optifuel 5/15 laser mix and it sang very sweetly. I plan to run up its rather less healthy brother tomorrow just for fun. Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted July 14, 2022 Share Posted July 14, 2022 Jon - do the Turnigy props run fast because of some advanced design, or are they just "optimistically pitched" as it were? Quote Link to comment Share on other sites More sharing options...
Eric Robson Posted July 14, 2022 Share Posted July 14, 2022 Hi Jon, if the OS runs on the optifuel 5/15 would it be alright for a Saito engine? Quote Link to comment Share on other sites More sharing options...
David Ovenden Posted July 14, 2022 Share Posted July 14, 2022 Not quite the answer to the original question, but... I had a Flair scout triplane that flew OK on a first generation OS FS40 (not the Surpass) and a Flair Legionaire biplane with a Saito 45 using a 12.5 x 5 prop. I really don't see why the OS40 surpass wouldn't be OK in your Flair SE5A unless it ends up extremely heavy somehow. 1 Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 14, 2022 Share Posted July 14, 2022 59 minutes ago, Matt Carlton said: Jon - do the Turnigy props run fast because of some advanced design, or are they just "optimistically pitched" as it were? i think its because they are very thin, These are turnigy type A wood. I have a number of them and they all run fast. Its how i can get away with a 15x5 on my saito 45. While on fuel, my saitos have all run in 5/15 model technics laser 5 for years. I am yet to transition that model to the new optifuel but i do not expect it to be an issue. I switched my enya 53 over and it ran really nicely. In fact, my enya 53 and both of my OS40fs's would knock and throw props from time to time on the MT laser 5 fuel if i went too far past peak revs when tuning. Having switched them to the optifuel laser 5 they no longer do this. which is nice as the 53 was savage. 🙂 Quote Link to comment Share on other sites More sharing options...
Ashley Hunt Posted July 15, 2022 Author Share Posted July 15, 2022 Wow, that turned out to be quite a lot of information. Thanks to everyone for your input. I think I’ll move the OS40 on and go just a little bigger to give myself a bit of a margin. All the information on props was great, that’s always been a bit of a black art for me and just buying different sizes to see what happens can get expensive, so thanks. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 15, 2022 Share Posted July 15, 2022 30 minutes ago, Ashley Hunt said: I think I’ll move the OS40 on and go just a little bigger to give myself a bit of a margin. You might change your mind when you see the price of new OS's at this size. The 40 might all of a sudden become very attractive so i recommend you hang onto it until you find the deal you want on a 45-52. 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted July 15, 2022 Share Posted July 15, 2022 1 hour ago, Ashley Hunt said: just buying different sizes to see what happens can get expensive Cheaper than another engine, an APC 12x4 is a fiver.... trying a prop takes, what, one flight? 15 minutes? Quote Link to comment Share on other sites More sharing options...
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