My brother, who has been flying mostly nitro powered planes (and some electrics, rarely), wants to move on to gas powered ones.  He has two or three .90 size planes. 

So the question to people who have significant experience with gas planes here are :

1) Is it OK with putting an appropriately sized gas engine on one of the 90 size planes (assuming such an engine is commonly available), OR is it just better to go for a 120 size plane or higher ?

2) If it is quite OK to use a gas engine on a 90 size plane, what engine do you recommend ?  I think he does not want to spend much on it now, just looking for something like, for example, the better ones available in Hobbycity (we may find some thing in the classifieds locally here).

3) If it is better to get a 120 sized plane, what engine do you recommend ?  We know DLs and DAs, but the question is more about the clones (and other brands) that people have experience with.

4) Should the plane be even bigger than 120size (which is commonly available locally), for the whole thing to make sense ?

the main reason to go in for gas normally should be to fly 120 and above as nitro engines are not common on bigger capacities.  it would be better to go in for an all new gas airframe and engine of atleast 50 cc  and keep the nitros the way they are and use them.

Getting new airframes is sort of easy here, as the secondary market is quite active.  Many people with "resources" get new stuff, play with it from sometime, get bored and move on , allowing the rest to pick up stuff in good quality at really good prices.  But the big engines are not not actively traded like that.

its better to invest in a quality engine in the first place as he is an experienced flyer and move on.

At around $120, the engines from HobbyCity are quite enticing, that is what he was telling me.  Wonder if anyone here any experience with those ?

Bumping this topic.  In addition to the gas engine itself, what other items does one have to procure for a gas setup ? 

What are the specific items to note during the build ?

Hi Anwar,

Let me impart my limited knowledge on this topic,

1. As a thumb rule, a 1.20 size plane can be comparable to a 26cc plane.  This is the rough conversion.  But if planning on 3D flying, then it makes more sense to go in for atleast a 50cc engine as the power to weight ratio would drastically increase.  But it does not imply that a 1.20 plane on a 26cc gasser cannot do 3D!!

2. On a .90 size plane, a 26cc might be slightly overpowered, but it is doable.  A friend of mine has the Seagull Yak .90 and he is putting a CRRC Pro 26cc engine on it.

3.  Companies that can be considered for a 26cc engine are SPE, Melody and the latest DLE 30!!

4. As far as the building front is concerned, the main problem is dealing with the vibration.  Everything should be rock solid and should be secured. 

Please do let me know if any more info is required. Would be glad to help out..

- Chan

I thought there are other issues specific to gassers, like using a separate battery for ignition and so on ?

Some more pointers,

1. As Anwar pointed out, a 2100 mAh 6V battery is required for the ignition.  I personally use a LiFe, but a NiCd or a Lipo with a regulator should also work fine.

2. The props should be drilled according to the engine.  The DA prop and the 3W prop have different mounting holes.  So we might have to make a jig to drill props.

3. Get hold of a few NGK spark plugs.  Quite difficult to source in India. 

4. Use threadlock on all mounting bolts.

5. Separate tubing is required for gasoline engines.  Regular silicon tubing would not do!! You need to buy tygon tubing for the plumbing and also for your fuel can.

6. Gas Oil mixture also plays an important role.  Depending on the lubricant that you use, be careful in mixing according to recommended proportions.  I personally use 20ml of Klotz Gasoline oil for every liter of petrol.  And upto 50cc engines, we do not require high octane petrol.  Regular petrol should be enough.

7. You would need two switches.  One for the ignition and one for the Rx.

8. DO NOT COMPROMISE ON SERVOS!! The vibration of a gasoline engine puts in more stress on the servos than a regular glow powered plane.  So always try and go for slightly overkill servos.  Because of the vibration and strain on the servos, the Rx battery drain will also be higher..

Would update as I think of other things..

- Chan