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Engine for Flair SE5A


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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 ?

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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 by Jon - Laser Engines
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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 by Matt Carlton
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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. 

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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. 

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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. 

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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

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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.

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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. 

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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.

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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. 🙂 

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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. 

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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. 

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