Two Wings and a Round Engine

[David P Williams]

Having got out my plans and bits and pieces for the 96inch Dragon Rapide, and seeking further info and advice on here, I decided that it was a bit too challenging for now.

So - I headed into the loft to rummage through my kit stash for something interesting and challenging enough, but with a lot of the hard work already done compared to just starting with a plan.

I emerged with this -

I've had this a long time - it has moved house with me at least 3 times, and now I have this to go with it -

A big indulgence to cheer me up in these depressing times. Yes I know the Stearman only needs a Laser 180 really, and this is overkill at 77cc and twice the weight, but it would have needed lead up front anyway.

Quite a few have flown successfully with this engine's predecessor - the Evolution E770, so hopefully all will be well. Engine mounting needs a bit of a think as I don't feel that Flair's rolled thin ply tube system will be up to this, but some chunks of 6mm ply should sort it out.

I'm not up to a detailed build blog, but I'll post some progress pics as I go along. I ought to have 8 hour days to spend on this but SWMBO has other ideas of course, so progress might be a bit erratic.

Opening the box reveals this pile -

A mixture of good old fashioned die cut sheets (very cleanly done) and CNC routed thicker sheets, piles of strip and several packs of hardware. First job underway, which is to identify and number all the parts in the sheets from the thumbnail versions printed in the build manual, before they fall out and get mixed up.

The wing plan is helpfully printed on translucent paper, like greaseproof paper, so you build port upper and lower wings then turn the plans over and build the starboard ones.

Probably going to finish it as a US Navy N2S variant, like this -

or this -

I used to work on full size light aircraft maintenance and restoration at Spanhoe Airfield and worked on (and flew in) several Stearmans, so I have quite a few pics to work from for the details. I hope it will be a reasonable scale effort but I'm not trying to win competitions and I will need to keep an eye on the weight.

I'm really looking forward to this.........

[Denis Watkins]

Very few on this site could constructive comment David, as myself I run 1/7th of your motor

And most of my models have a wingspan about the size of the Stearmans horizontal stabilizer

Or maybe just one of your 4 wings

But your aims are spectacular and will feed my dreams, and I will watch closely

Edited By Denis Watkins on 15/04/2020 17:59:29

[Rod Parsons 1]

Very nice

I have one of those to build, as well as the a NIB tiger moth kit.

Mine was one of those ‘well built, part finished kits’ you see advertised.

Luckily just the fuselage and tail had not been attempted (ruined).

In the end I just cut it all up to save and reuse the formers. It’s now totally rekitted.

I think I will make mine into a 4x aileron version. I’ve obtained a second set of hinges.

I will be following this with interest

Rod

[Robert Parker]

Hi David,

Watching with great interest would love to heat that engine.

Regards

Robert

[Robert Welford]

David,

I'm in a similar position also with a Flair Stearman in my kit collection. I have an OS Sirius fr5-300 radial that I plan to use. It will sound superb.

I am making good progress with a few projects so this may get to the front of the queue soon.

I look forward to following your build blog.

Have fun!

Robert

[Simon Chaddock]

Very nice.

Just don't crash it. I am sure the engine is worth far more than the air frame.

[cymaz]

Got an Evolution / UMS 7-77 on a 13kg airframe.....it goes round like a scolded cat !

Torque issues may be a problem. Be careful. Best of luck with the build. Now watching

[Jon H]

is the engine glow?

[Manish Chandrayan]

That should be a cracking combination. But if you think that the engine may crack up few pieces of the aircraft, there is a new 5 cylinder 55 cc petrol or the 7 cylinder 50cc Petrol from UMS available from Morris Mini Motors

[Chris Berry]

I've got a Flair Stearman. It weighs 24lbs and has had 225 flights with me.

It started life with a Laser 200v up front. It was ok and did the job but on a calm, warm day it would take 100yds to get off and loops were just about doable from a dive.

I then replaced with a 300v and it was transformed. Off in 50yds and loop from level. That's not scale but gives some reserve. It's done most of its flying on the 300 which Jon Harper serviced for me last year. It's a twin carb and on a 24oz tank i get about 10 minutes with some reserve.

I think a 180 would be marginal unless the plane is kept light. The Evo77 will be perfect if you build heavy.

I didnt build mine, so can't advise but it's a standard Flair way of building around the central fuel tank box and front end. They are good kits and all fairly straightforward.

Flying wise it needs to be flown on. Being a heavy plane mine wont 3 point very well, it tends to bounce a bit. Ailerons and rudder max deflection and a fair bit of elevator. Loops and stall turns/wing overs are fine. Rolls are slow and need height. Will cope with a good breeze and a reasonable cross wind.

[David P Williams]

Thanks everyone - yes, the first flight or three will be puckering. The engine needs 3 hours of running in before I get to that stage according to the manual.

Yes Jon it's glow. The petrol version of this is now 90cc (same external size) so even more power and torque than I need, heavier with the ignition unit, and £700 more expensive (and I can't stand the smell of petrol anyway). If I use an onboard glow driver I guess the weight will end up the same though - the UMS manual says I shouldn't need one once it's run in properly, but hmmmmm.

It came with a test report from the factory. It had a 20 min run, with a 24x8 Menz prop. 1450 idle and 5450 max. It claims 8.8kg thrust in the spec, so should be "enough".

[David P Williams]

Manish - yes I know about the petrols - I bought this one from Morris. Stearmans have 7 or 9 cylinder engines, so if I'm doing the real radial thing then 5 cylinders won't do. The 55cc petrol is the same physical size as the old 35cc glow, too small to look right at this scale and possibly marginal on power.

[Jon H]

The model was originally designed for a laser 150 but i think you would have to build it really really light for that to work. I always recommend our 300 for it and everyone seems very pleased!

David, the engine looks awesome. Its a shame i cant offer you one of my 75 or 90cc designs. They are only 3 pots though.

As for running it in, i read the blurb on the evo versions and was really surprised by their recommendations. 3 hours is a crazy amount of time and if its the same as it was dont you need 3 different fuel blends and can only run for 5 minutes at a time?

I remember thinking i would never buy one if i had to go through all that as i cant even begin to understand why its necessary. I can only assume its insurance against those without any mechanical sympathy?

Anyway 5450rpm on a 24x8 is woeful for an engine of that capacity in hp/cc terms, but its not designed for high performance as its all about the looks, sound, and the delivery. It should suit the stearman very well.

[bert baker]

I’m not a fan of a 7-70 glow

[bert baker]

But the Stearman is nice to fly, ( when all the cylinders are alight)

[Rod Parsons 1]

Saito do a couple of 3 cylinder petrols.

I thought the 90 3x cylinder would work ok. From what I read the 84 that preceded was not that good.

I also see on their website they have a 5 x cylinder 73 which looks like a new addition.

Rod

[David P Williams]

Jon - if you did a 7cyl radial of around the correct scale dimensions I would of course rather buy that. This Indian engine may turn out to be a mistake, but it is the right physical size for the model, has the right number of cylinders, and looks fantastic, like a piece of jewellery.

The fuel and "break in" advice in the manual seem to be the same as you mentioned for the Evolution version

Like you, I can't understand why it needs such a faff. I normally take your view on "running in" - fire it up, tune it up and go fly. My engines have always been fine. Looks like I will have to get into mixing up my own fuel though, one way or another. I use Model Technics Lasermix 5 in all my engines at the moment which I think is 15% oil so mixing half with straight methanol would give 7.5% oil and 2.5% nitro I think. Will have to work out how to mix it oilier for first runs I guess.

And yes, it's all about looks and sound - I won't be trying to prop hang.

If you ever get the inline twin you have hinted at into production I'll be first in the queue - somewhere else in my kit stash is a TopFlite 1/5 89" P51 just waiting for that engine.

[David P Williams]

Bert - I remember your complaints about the Evolution engine on another thread. Glad you think the Stearman's nice to fly though.

Rod - Yes, I'm aware of the Saitos but as I said earlier this is about how it looks and sounds, and I don't do stinky petrol (yes I know I could use Aspen at the same cost as glow fuel)

[Jon H]

David, i wonder if their instructions are intended to protect against stupidity. They make it seems really convoluted just to get the point across?

Looking at the construction of the engine i cant see much in it that is likely to cause a problem. Ball bearings dont run in, the rings are in chrome liners, which dont need much running in, the valve gear is all steel...The rods might need some care? but even if they arent bushed i cant really see it.

My only thought was that as they cycle the intake charge through the crankcase they dont want to draw all the metal particles from running in back into the cylinders so try and slow down the run in process. Its a stretch but its all i can think of.

As for my radial designs they were all 3 cylinder as the objective was to make a powerplant first and 3 cylinders has a number of advantages in terms of cost, weight, complexity. We did do a few 7 cylinders years ago. I think they were about 180cc? It was long before my time but im told they had 3 people stood on the test stand and it was still being pulled forwards!

As for the mustang, if all works out nicely i might have something interesting for it. Assuming my prototype works!

[David P Williams]

Thanks Jon. I 'll have a chat with Morris about the run-in, if he says it's necessary then I'll work my way through it.

Good luck with your prototype, looking forward to more info about that in due course.

So - the start of a build, tidied up workshop, cleared bench, EXCITED

As is fairly normal practice, the manual recommends starting with the tail group

More info as I get to major points in the build.

[Rod Parsons 1]

Hello

The Saito sound quite nice. I’ve seen reports of them eating themselves, which isn’t good, consider the cost.

ive got some other projects ( total house renovation) before I get on with the Stearman.

There were some build threads on RC Universe reporting of incorrect tail incidence and a power climb issue.

I was trying to get hold of pictures of the full size to see if the tail section was cambered or symmetrical. I figured if I made the tail ribs cambered it would help reduce the power climb tendency.

I will be flying mine pretty much ‘full on barnstorming’ hence I’ve got another set of horns/hinges to make it 4x aileron.

I didn’t see any 3 x cylinder Laser engines on the site or know of their existence

regards

Rod

[David P Williams]

Hi Rod - Jon's 3 cylinder engines are just designs at the moment I believe, he's unable to get them into production just now.

The first batch or two of the Stearman kits had some errors, including the tailplane incidence. I believe later batches were corrected, but the tailplane incidence should be between +3 and +3.5 deg to avoid carrying lots of down trim and the power climb problem. They also suggest up to 3 deg right and down thrust for larger, more powerful engines.

The Flair Stearman webpages are still live, with the customer feedback, hints, tips and corrections here

[Lindsay Todd]

I built mine back in 1999 when they first came out. Fitted with a Zenoah 45cc petrol gives adequate power but you do need a shallow dive for loops and then keep up the momentum. I can't complain though as I still have her after 20 years and still looks good and fly's great. There was an incidence issue as already reported with a climb under power being quite noticeable. I increased the incidence on the tail plane by probably 2-2.5 degrees to counter and largely resolved the issue, later plans I believe were rectified so it will depend on the age of the kit if this correction has been applied. I still think this is probably my all time favourite model though.

Linds

[Jon H]

Yea my radial aspirations are as yet unrealised. The designs are more or less done and have been for years, i just have to try and encourage the boss to get them manufactured.

Part of the delay came from the fact that at 90cc it needs to be petrol and we didnt have that sorted at the time.

[bert baker]

My Stearman is heavy it’s from a Ziroli plan

When the engine is on song, it is a good fun plane to chuck about