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Introduction and Engines query

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Nigel R18/08/2020 08:09:24
4173 forum posts
698 photos

great stuff

flying's like falling off a bicycle, it'll come right back

Simon Lumsdon 116/09/2020 00:05:21
8 forum posts

Well i built the Cougar and fitted the OS FS 40 and flew it and it was a bit of a handful for a beginner i must admit, had to throttle it right back, it flew ok but felt over powered and a bit twitchy. I managed to get disorientated and binned it which broke back of fuselage at the weekend, decided to fit a good OS FP 40 i had sources on ebay following a previous recommendation, flew it this evening and much much better, smoother and steadier. The FP on a 10x6 is definitely lower powered than a FS 40 Surpass on 11x6.

Anyway, quite pleased that i now have a plane which i can hopefully get some time on to improve.

Bit disappointed in the build quality of the Cougar, extremely lightly built, just bought a Wot4 artf as its potential replacement and it much more strongly built, we shall see ...

perttime16/09/2020 05:42:11
200 forum posts
11 photos

"1.3cc Mills - planning for a Just Junior "

Give Control Line a try?

People have been flying Weatherman vintage speed, and I believe there is a separate class for the Mills.

Chris Walby16/09/2020 06:24:44
1350 forum posts
338 photos

Simon, sorry to hear about your disappointment with the Cougar, but it is what it is...a light weight very aerobatic model.

I have used one for instructing new trainees and orientation can be an issue (until a couple of large Solartrim circles were stuck to the upper surface of the wing). My students got on well with it, as it could fly very slowly and on low rates is very stable, but on high rates for the instructor makes it very responsive to avoid the ground.

Mine and another one at the club have done sterling work and taken a lot of knocks and I can only think you have high rates and an incorrect C of G to make it fly so poorly.

If I could find a 4 stroke to do it justice I would get another, but may just end up with an electric version to really explore the manic capabilities.

PS - Fly the WOT-4 and get the thumbs well dialled in....then its Cougar time wink

Nigel R16/09/2020 08:39:08
4173 forum posts
698 photos

Cougar is meant to be very light. And very responsive. This is it's natural environment:

If you find it twitchy, it needs the movements reducing. These sorts of models are pussycats at slow speed with reduced throws.

BTW the OS 40 FP is definitely (slightly) more powerful than a 40 FS; if yours is not then something is amiss.

Edited By Nigel R on 16/09/2020 08:42:57

Simon Lumsdon 129/09/2020 22:39:59
8 forum posts

The Cougar is flying well (or i am improving), have increased throws to 50% and the FP40 is well suited to the model, starting to get my confidence and started to hoon it around on full power today In hind sight suspect issues were all flying related, c of g, throws and engine are all fine. Adding some circles to the top of the wing is a good shout, it does seem easy to get disorientated with this model, someone commented the purple doesnt help either, although that may also just be inexperience..

kc30/09/2020 09:15:11
6724 forum posts
174 photos

Note that the original OS 40 FP benefits from a large diameter prop such as 11 x7 as it won't rev but does much the same revs on an 11 x 7 as on a 10 x 6 ( see engine tests of the time it was first sold) Later OS40FP had different piston and liner I think so it may not apply to them but worth a try.

So when you need more power try an 11 x7 - if the u/c gives enough clearance for the prop

Martin Arnold 130/09/2020 10:51:18
34 forum posts
5 photos

"If I could find a four stroke to do it justice"

Several of us at my club have been running 4 stroke Cougars for years, powered by OS 52, Saito 50 and 56, the Saito powered ones are arguably the best as the Saitos have a sharper throttle response (most important on a Cougar) than the OS 52, there is not much difference in weight between the three they are all around 450gms with silencer.

Mine is the one with the Saito 56 on an APC 12.25 x 3.75 funfly prop, it is pulling 11900 rpm flat out (usually only used in the vertical) which makes for an impressive thrust to weight ratio. The plane is 3lb 10oz all up and those figures give 9lb 7oz static thrust !! With a top speed of 42 mph.

The point with a Cougar is not to let it fly too fast they are likely to self destruct with surface flutter if you over speed them, so I would keep away from props with too much pitch.

The thing I like the most about my set up is the instant knife sharp throttle response and grunt from the Saito, which most 2 stroke can't match also the 4stroke gives good engine braking to slow you down.


I spend a lot of time setting up the motor for perfect transition and good idle as particularly on a Cougar the throttle is a primary control !!.... It will get you out of all sorts of trouble


Edited By Martin Arnold 1 on 30/09/2020 10:58:08

Nigel R30/09/2020 11:15:06
4173 forum posts
698 photos

"The Cougar is flying well (or i am improving)"

Good stuff yes

"Later OS40FP had different piston and liner I think so it may not apply to them but worth a try."

I have two of the later version FPs.

Both will spin a 10x6 APC on any given day at around 11,500. I have seen near 12k for the odd peak from the (ever so slightly) stronger of the pair on the right day with all the moons in alignment etc etc. I recorded the 11x6 APC turning at a hair over 10,000. I use 5% Weston synth fuel and Model Technics warm plugs.

I would say the 10x6 is not ideally suited to the Cougar. A lower pitch would be better, say 11x4, which would provide more thrust at the low speeds the Cougar flies at.

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