qwertypemdas

My Feedback: (1)

I'm building a big twin engine plane but I'm trying not to break the bank here so I'm thinking about picking up two Aviastar 46's for $100 total. If I were to go with OS I could easily spend $300 for the same size. Aviastar engines haul ***** as I hear but does anybody know about the reliability? With the plane I'm building if one engine goes out you're done, end of story. So I'm looking for reliability in the full throttle range. I looked through the reviews here on rcu and one guy said the engine was great other guy said low end and transition was terrible and the engine just cut out every time. Is the .53 more reliable? I don't mind spending an extra $20 for a bigger more reliable engine but it's just the 46 with a longer stroke I think. Any other engine suggestions would be nice. Recommended engine sizes are .40-.60 two stroke. Power isn't really a problem I hear it flies great on 40's and I build light. Might try 4 strokes but that would probably be too spendy.

rambler53

My Feedback: (494)

You said it yourself. Flame out with a cheap engine, costs you the plane. Ante up for the OS, and no, you can buy 2 AX46's on the marketplace for about $200.

spaceworm

I would only do a twin with electric power, that is why I don't have any twins! But a twin 46 equivalent electric system would cost more than two
OS 46 engines, I think. If you go glow, read about the advantages of engine thrust angles and which engine to have quit first, etc. And, sharpen your reflexes.

Regards,

Richard

jeffie8696

As Ihave pointed out in my reviews the Aviastar engines have unreliable carbs in some instances. It is a hit or miss issue and Sig is great about correcting any bad carbs but with reliability being so critical to a twin engine project Iwould spend my cash on something like a Thunder Tiger Pro 46 or OS engine. Thunder Tiger GP42 is also a very reliable engine at a modest cost .

qwertypemdas

My Feedback: (1)

Hmmm, so a pair of nice engines from the market place here or ebay nib or something would be the way to go I guess. I am DEFINITELY not going electric so yeah I guess price is reliability. Probably won't finish this plane for 2 years, I have a few other projects so I'll keep my eye's peeled for deals on some OS's.

hugger-4641

My Feedback: (6)

Ditto what was said above, get a pair of Os 46. Ax. I have an Aviastar .46. I'm now getting good service out of it on a high wing trainer since I installed a modified carb from an Italian .45 Super Tigre. I would recommend just getting an Os.

qwertypemdas

My Feedback: (1)

Ok, well just for hoots, are 4 strokes very reliable? I've had tons of 2 strokes pass through my hands but I've never once gotten into 4 strokes. Would probably make a more scale sound with a more scale propeller and a smaller muffler, but costing twice as much...

Ed_Moorman

My Feedback: (1)

My buddy, "Flaps" Laffert and I have built 25 twins, so we are pretty familiar with how to make them work. Problems with twins come from inexperience and letting your buddies who have no knowledge of twins help you.

Use some out thrust on your plane if you can. It works. 8 degrees is ideal, but it looks like way too much. You don't notice it in flight. Any amount is better than nothing. I built and tested a plane with 8 degrees out thrust and took off with one tank half full and the other topped off. I did this with both engines and flew acro until the one with the low tank quit. The only way I could tell is the plane slowed down. Just to prove a point, I removed the original engines and installed a Thunder Tiger .46Pro/11-6 and a Thunder Tiger GP.42/10-6 and flew it that way. Couldn't tell a difference.

1. Break in your engines on a single engine plane first and get the needle settings right before putting them on a twin.

2. Use a mid range prop on the .46, something like an 11-6. Don't go for a small prop for speed or a large prop until you get things sorted out.

3. Set your engines individually. Crank one and set it, hold the nose up for a good 20 seconds, then shut down. Crank the other engine and set it. Top off tanks and start both and fly. Do not tweak the needles. You will probably get one too lean and have an in-flight failure. Trust me on this, 1,000 rpm difference is much better than 10,000 difference. Your best setting for a twin is slightly richer than for a single engine plane.

4. Forget a tach and syncing your engines. set both for reliable running and fly. Your flight setting should be SLIGHTLY RICHER than normal. With 2 engines running, they will tend to run leaner in flight. Don't go peaking them out or let your buddy peak them out.

5. Pull-pull is best for rudder. And also a strong servo-80-90 in-oz torque. If the plane comes with a rudder pushrod, install another control horn on the other side of the rudder and run a cable to the servo. Hold full rudder stick and try to straighten out the rudder both directions. If you can do it easily, you need a stronger servo or to stiffen the pushrod or install pull-pull. The rudder is going to save your *****, so get it right.

6. If the plane goes goofy in flight, or sounds funny, chop the throttle, get it under control and slowly add power, checking if you need rudder. I have seen to many guys try to stay at full power and lose it. You may not be able to hold the plane with full power on one engine. Setting it down level in the weeds is better than rolling over and dieing with one engine at full power.

mike109

G'day Four strokes are very reliable. These days I only fly four strokes - mostly Saito, a couple of OS and three beautiful Lasers. The Saitos need about 40 minutes running in and from then on they are bullet proof. A pair of 56s or 62s would be excellent in your model. I have most running upright but some are mounted inverted and at other angles.

The trick is to put them in a test bench for 20 to 40 minutes then put them in a trainer for about an hour before putting them in your twin.

I did try a couple of Magnum 30 four strokes for a twin but I could not get them to run the same. Other Sanye (ASP and Magnum) four strokes I have owned have been fine. Cheap too but they do need some castor oil in their fuel especially when new.

Saitos usually come out of the box with the low speed needle set very rich and for reliable operation this needs to be correctly adjusted. There are many threads telling how to do this.

Have fun.

JohnMcGowan

My Feedback: (15)

Listen To Ed Moorman... he KNOWS what he is talking about!![sm=thumbs_up.gif]

John

Ed_Moorman

My Feedback: (1)

We have used 4-strokes on twins, too. Mike109 has some excellent points. We tried a couple of Mag .30 4-strokes, but could never get them to run together reliably. The Magnum .52 4-s run great in twins. We've had our pair on a couple of scale twins and never had an engine failure in flight except for my flying too long and running them out of fuel.

I also have several Saitos and they are really reliable. I tend to use 4-strokes on seaplanes so I don't have to paddle out when they quit on taxi back. I have a .56 and it is excellent. My buddy Flaps likes scale so he tends to snag all the 4-strokes. He's 89 and I do all the flying. I like faster sport, twins, seaplanes and Sticks, love Sticks. Anyway, I tend to end up with the 2-strokes, except for seaplanes.


I bought this nice little Thunder Tiger .75 4-stroke. Good running engine. I broke it in on my bench for about a half gallon of fuel, then flew it in a plane to further run it in. Next thing I know, Flaps wants it for a scale project. It's a short engine and won't stick out past his cowl. That's where it is now, in a 72" radial engine version of a Fairchild 24.