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avtur28/02/2015 20:46:21
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I'm your typical returning modeller in that I've been totally overwhelmed by advances in electric power. Over the past 3 years I've accumulated a collection of various electric ARTF models, they have served their purpose very well, without the convenience of electric I would not have returned to the fold.

However I do have an inkling to fly something which goes suck-squeeze-bang blow! Previously I loved the sound of four strokes but I'm beginning to think that petrol two strokes might be the way forward.

If, and that's a big IF, I understand it correctly a petrol two stroke can offer a very high level of reliability, almost to the point of electrics, in that once set up all you do is put fuel in and they go. Is that realistic or have I just read reports that are overly optimistic about running petrol two strokes?

Given that I have a passionate love of Cubs, reflected in my electric fleet, what would the panel suggest as a good entry level combination into the world of petrol two stroke flight?

I'm a grey haired, semi-retired sport flyer ... I admire those who can fly 3D but that's not my ambition ... I'm looking for something that 'bimbles' very well!

Am I correct in my thinking about petrol two strokes and what would the panel suggest ??

Edited By avtur on 28/02/2015 21:01:36

Bucksboy28/02/2015 21:02:39
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575 forum posts
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Look at the four strokes, I've got a Saito four stroke and its a delight. Much quieter than any two stroke petrol I've ever heard.

Paul Marsh28/02/2015 21:09:00
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3956 forum posts
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Why not go full hog, and get a flat twin four stroke for your cub?

john stones 128/02/2015 21:24:34
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My experience of petrols has been good, very reliable and cheap to run, they need the odd tweak to the needles now and again. A 20cc would fly a good size Cub, Zenoah, DLE etc. They can be a little noisy but a few quid will sort that out

John

Dave Hopkin28/02/2015 21:48:24
3672 forum posts
294 photos

OMG an elecy flyer going to the dark side............... surprise

The full story will be in the Sunday Tabloids....

No seriously many of the flyers at my clubs use 4 stroke and the do sound a lot better than 2 strokes

Havent got a clue about performance, as for reliability, I'm electric so I dont do the prop flicking in frustration bit wink but though I hate to admit it, 4 strokes do sound better, not as "screamy" as 2 strokes....

Willyuk28/02/2015 22:15:39
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176 forum posts
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I like "screamy" nowt better than a decent 2 stroke preferably on a tuned pipe. and way better than electriv. I fly all of them and there is no "better" just different.

iqon28/02/2015 22:29:37
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1481 forum posts
239 photos

price of 30cc petrol, you cant beat it.........and cheap to run........getting one into a cub......well yes i am sure you can....several are designed for 30cc.....( in usa )smiley

avtur28/02/2015 22:32:23
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This may be one of my misunderstandings, but I'm thinking that petrol two strokes don't rev as highly as 'nitro' two strokes. So in the scale of noise then a nitro 2 stroke is at the top of the scale with nitro 4 stroke and petrol 2 stoke somewhat down the scale.

I'm sure that choice of silencer/muffler must have an effect, I would be grateful to hear the opinions of those who are better informed than myself.

The absolute noise level isn't a limiting factor, just that the put-put-put of a lower speed exhaust is more appealing.

 

Edited By avtur on 28/02/2015 22:33:56

john melia 128/02/2015 22:46:53
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i fly only petrol now , got rid of all the messy gunky nitro stuff and never looked back , i had a few hiccups at the beginning but thats to be expected . love the sound , they may be a little on the loud side but once up in the air and throttled back a bit they aint too bad , plus you can get aftermarket exhausts if you need to get the noise down , but exhaust replacement is only part of the equasion , a lot of noise is from the prop , and the fuse vibrating like a drum skin , i pack mine out with foam to deaden it .

why pay £20 a gallon for nitro when you can get a gallon of petrol for a fiver or thereabouts . I've nevef been into electric stuff , doesnt float my boat , but thats just me

john stones 128/02/2015 22:51:44
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11445 forum posts
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They sound a bit throaty Avtur but as John says there are some better after market silencers, but if you're site has no noise issues (like ours) then it's no problem.

John

Adrian Smith 128/02/2015 23:01:26
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2413 forum posts
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I must admit Avtur I am a petrol convert and have some good experiences with 30cc & 60 cc gassers. Where I fly there is no major noise issues but I do invest in some decent after market canisters to quieten things down. That's more a matter of consideration for others than anything else. It's a whole new ball game and dealing with vibrations has been an eye opening exercise believe me. However, engine and prop combination plus thread locking are the key. The one thing I like is that there is no needle fiddling at all after initial tuning compared to glow engines. The only thing I might have to do is open the the HS & LS needles a quarter of a turn on very cold days. I am hooked! Like John leccy has never floated my boat either but each to their own.

J D 828/02/2015 23:02:34
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1439 forum posts
84 photos

There are now petrol 4 strokes on the market,Saito do one.

trebor28/02/2015 23:37:27
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1928 forum posts
216 photos

Can you tell me how the 4 stroke petrol engines are lubricated ? Have they got a wet sump or do you add the lube in petrol ? Its always puzzled me.

Levanter01/03/2015 06:59:16
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882 forum posts
437 photos

The lube goes in the fuel just like the 2 strokes and the lower end is lubricated by some oil blowing past the piston into the crankcase, then to the timing gear and then up to the rockers and valves. Excess oil is blown out of a vent in the crankcase, or is the recent trend, the oil is collected and fed back into the carb.

Oh how I wish someone would develop one with a separate oil system.

..01/03/2015 07:46:44
974 forum posts
1 photos

Why are we calling these " gas" engines? Surely its a Petrol engine.

trebor01/03/2015 07:56:03
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1928 forum posts
216 photos

enlightened Lpg !!

..01/03/2015 08:16:06
974 forum posts
1 photos

The crankcases are aluminium Bob not Aloooominham , so Petrol engines it is. wink

Peter Miller01/03/2015 08:26:29
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10946 forum posts
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10 articles
Posted by trebor on 28/02/2015 23:37:27:

Can you tell me how the 4 stroke petrol engines are lubricated ? Have they got a wet sump or do you add the lube in petrol ? Its always puzzled me.

 

They use the same fuel as two strokes and rely on the oil being blown down past the piston into the crankcase. It works well.

Sorry Levantor. Missed your posting.

Edited By Peter Miller on 01/03/2015 08:27:15

Peter Miller01/03/2015 08:33:07
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10946 forum posts
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The few petrol engines in our club have been very, very noisy. and needed much better silencers.

Our flying field is 1 mile 200 yards from my house. ON a calm day one can just about hear a .40 two stroke. It was so faint that if I had not been listening and known what it was I would have missed it.

A 30cc petrol engine was really noisy. Even at that distance it would have generated complaints. The owner had to make up new silencers. The same applied to a PT20 with a 30 cc petrol engine. Again new silencer needed to get it down to somehwere near acceptable.

Large four strokes are far, far quieter.

cymaz01/03/2015 08:34:44
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9185 forum posts
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Just Engines have some petrol four strokes on the shelves.

I have a couple of Evolution 33GX 2 stroke petrol engines. What no-one can tell you with any certainty is how effective is the exhaust muffling. I've managed by sticking on extra baffle boxes after the standard exhaust output pipe. This has done the trick. But i have had the room to do it.

To me , most of the cheap petrol 2 stroke muffler canisters don't actually reduce the noise. ..just redirect the hot gasses away from the engine.

The more you pay for a petrol engine the better and more effective the silencing should be. I looked on Youtube when trying to choose my first petrol. It was useless really, it all depends on how well the video was taken and how little air noise you got. Alot of the film was taken by mobile phones etc...not the last word in recording.

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