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Trevor

Petrol beginners guide

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For the uninitiated among us, can someone explain what is required to use petrol instead of glow? How do you overcome interference etc? Is there an equivalent of the .61 2-stroke glow in petrol or do you have to start with 30% CAP size planes and 26cc engines? What is a good starting point for introduction to petrol?

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I was seduced by the easy of starting and the lack of field equipment, in theory all you need is the plane, your tx and a can of petrol. Switch it all on and flick it over.

 

The reality is a little different as those watching roger starting his 62cc zenoah today will testify, it needed two 12v batteries and a good starter to get it turning over. For some reason the hand flick just wasn't working.

 

Anyway to your question 'where to start' and how big?

 

You're spot on with the engine size, the 26cc petrol motors are about as small as they come, but the mvvs 1.60 (26cc) weighs the same as an OS120 four stroke and would fly something designed for that.

 

I'm just building (assembling) a Glens Models CAP which is designed for a 120fs or the zenoah 26cc. The zenoah is over a pound heavier than the mvvs. As for the model in actual size (68" span) is about the size of AstroHog's that a few of s built a few years ago.

 

http://www.glensmodels.com/CAP232%2068%20Frame.htm

 

I should have the engine on tomorrow, I'll take a few pictues of it.

 

I also have an extra 300 which is a world models kit designed for a 160 two stroke and in this I've put the mvvs 2.15 (36cc) petrol. This is a 78" span and I've attached a couple of pictures.

 

The ignition system is electronic and you tend to mount this up front with the engine and that's good enough to overcome any interference issues (not that there should be).

 

I've taken extra precautions by fitting an opto-isoltaor to the reciever to keep servos and rx separate on different batteries but I don't think it's really necessary.

 

As for fitting out, the only real differences are that the fuel tube is different, you don't pressurise the tank from the exhaust (unless you want a big bang and fire)

 

Joe and Gary may want to pitch in with their thoughts, but that's about it.

extra-running-in.jpg.b11a1479002afc1203692a6493afbf82.jpg

mvvs-36cc.jpg.a6c243c2149edad299ab326e74395f2b.jpg

first-flight.jpg.9a33b1a1e3b6c567b2d1fd82f7cbf54b.jpg

dp-and-extra.jpg.188ae457d1b4a673329964f6f0677127.jpg

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Thanks. Could you also include pictures of how the electronic ignition and radio stuff is wired together? How many batteries are required? I assume the ignition requires a separate battery?

 

The size of these engines seems a bit scary to someone used to .40 - .61 size engines but I suppose you get used to it.

 

Can you recommend a more sedate model kit for petrol then a CAP for a beginner, like a Cub or something?

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Wiring is simple, ignition unit is either run from a separate battery or off a magneto on the engine itself.

 

My mmvs's have a separate ignition unit connected to a separate battery by a switch. The ignition unit has an HT lead to the spark plug and a sensor lead to the prop driver - that's it. Again I'll take a picture or two to show.

 

The zenoahs have magnetos which do away with the 2nd battery but this makes them a bit heavier - but you don't have to worry about charging.

 

So in my aircraft I have 3 batteries, 1 ignition, 2 rx and 3 servos but you could run with just two and have common rx & servos but I like the security of an extra battery. See joe's post CURRENT LOSS for some more thoughts on batteries.

 

As for a model, don't be intimidated by the size, my 78" Extra flies like a wot4. When roger cut the throttle on his big CAP, see the Bank Holiday Sunday at Fickleshole thread in general chitchat to see how big that is, it was like someone applying a brake.

 

The trouble with something like a cub is that they only need low power so to make use of a 26cc petrol you'll be looking at a 90-100" span cub and that's getting huge. Gary and I have been talking about an ExtraWot and this would probably go OK with the 26cc mvvs.

 

I'll have a think but you should be looking for something designed for a 120 four stroke as an initial guide.

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Here are a few piccies

 

Some of the engine itself and a couple of the CAP next to my Wot4 for comparison.

 

The shopping centre beckons but when I get back and if it's stopped raining I'll get the cap and wot4 outside and take another couple of shots

cap-and-wot4-2.jpg.d98dd36fddeeaaf7a92c71222368f9b3.jpg

 

mvvs160-on-cap.jpg.d1a9c8d5a2fb311d4c8de2e279e76780.jpg

mvvs-160-plus-silencer.jpg.686efc7b628cfb4537323437a8542e59.jpg

mvvs160-and-Irvine-53.jpg.647ce01bddc3a951575e592778e49c8c.jpg

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and the sun is shining.

 

As promised here are a few shots outside so you can get a better feel for the size.

cap-cowl.jpg.bca7534aff9879277d130dbc8cfba3e3.jpg

 

cap-and-wot4-3.jpg.ebb81c1a41e84bd4b95a8c8511c872c4.jpg

cap-and-wot4-4.jpg.dc52497c9778f6fbddf389f23f5a3261.jpg

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