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twin engines models. why, how?

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twin engines models. why, how?

Old 03-25-2007, 08:25 AM
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Default twin engines models. why, how?

Just wondering how does a twin engine plane flying characteristics differs from the other mono engines models that we usually fly.
Isn't it the same? any new challenge that we should expect?

I've heard many considering this move as an upgrade in skills... what entry model do you recommend?
Will it be interesting to fly, more difficut, challenging????
Old 03-25-2007, 12:13 PM
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Default RE: twin engines models. why, how?

Just from what I've seen. Be ready for a one engine out condition. All the power is on one wing with lots of leverage. Then I guess if you're inexperienced in knowing how to deal with it, it has the potential to become a frisbe. I did that once on my sim and it just flat spinned fast into the ground.
Old 03-25-2007, 02:42 PM
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Default RE: twin engines models. why, how?

The problems exist [] and that is a sad truth about multiple engine AC.

IF you thought tuning one engine was tough try to get two working at the same time at exactly the same speed - otherwise you will get un even thrust and yaw will be induced.

Then you have the problems of a single enginr failure. This is tough if you are in a plane and you know WHICH engine failed - now you can compensate for the loss of power with lots of rudder - but in RC IF you hear an engine fail you don't know WHICH engine it was so ... which way do you push the rudder?? [X(] [] [:@] Often all you can do is kill the engines and dead stick in... [&o]

For those who master the problems, flying twins is a great form of RC - but there are risks.

Good Luck.
Old 03-25-2007, 02:46 PM
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Default RE: twin engines models. why, how?

I see
So it is basically more of how to handle the unexpected or shall I say expected RC problems; rather than flying skills and flying characteristics.
Old 03-25-2007, 05:32 PM
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Default RE: twin engines models. why, how?

When both engines are running at or about the same speed, a twin flies just like a single. Exception: Twins with single rudders have no prop blast over the rudder to help you steer at slow speeds. This can make tail-dragger takeoffs and any "go-arounds" a challenge.

Jim
Old 03-25-2007, 07:55 PM
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Default RE: twin engines models. why, how?

I make it simple with my multi engine,I have a simplex conector on the fuselage and I conect my lap top with a program called all systems go. I ajust each engine through the lap top then latter I compare the recorded performance.If there's so much as 1killabyte diffrence during flight the program automatically makes the changes nessasary in real time. the laptop is connected to the buddy cord and will also ajust trim ect. and will switch to the mal engine .
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Old 03-27-2007, 03:42 PM
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Default RE: twin engines models. why, how?

ORIGINAL: NJ Georgee

I make it simple with my multi engine,I have a simplex conector on the fuselage and I conect my lap top with a program called all systems go. I ajust each engine through the lap top then latter I compare the recorded performance.If there's so much as 1killabyte diffrence during flight the program automatically makes the changes nessasary in real time. the laptop is connected to the buddy cord and will also ajust trim ect. and will switch to the mal engine .
WOW! So you use your laptop like a flight engineer. Really neat.
Old 04-04-2007, 08:05 AM
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Default RE: twin engines models. why, how?

Its not worth the complexety of it though you have to have a buddy operating the lap top as you fly and he must be savy with the program.It would be alot better if there were on board starters for each engine and glow management on each.There just isnt enough room in the cowls for all that.I mainly get data for engine prfomance I can shut down any engine thats acting up,but there again its only done by visual problems like a miss due to fuel problems. I think simple is better. My da was a side gunner in a B29 I have a lot of nose art pics with him looking out the pilot window. I wish he was still around so we could share this hobby.
He didnt have me and my bro till he was 43, he was 75 in 93 and passed on that year. Now they have so much on TV like the military channel I wish we could sit down and watch it together. When he was alive I use to like his war storys.He had a lot of stuff from the war like a B29 pilots manuel and cannon shells. But all that stuff diapeared as I was growing up.Half his pics were stolen by my so called freinds too.
Old 05-21-2008, 12:14 PM
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Default RE: twin engines models. why, how?

My first twin was a Midwest Twin Stick...after that I built two more. Then I discovered the Hobbico TwinStar and had 3 of those. The twin sticks had ST .23's, then Leo .25's and then OS FSR .28's. The Twinstar had OS .40 FP's then Magnum GP .42's. Flying a cabin twin with K&B 65 Sportsters on 3 blade props, it's a Giant Scale 80" airframe.
You need to learn to use Rudder to fly twins and warbirds. An engine out WILL happen sometime. Throttle back and use rudder to land. Twin require reliable engines, and don't tweak them to max RPM. Detune the strong engine to match the weak one..My 80" twin is for sale for $175 with servos and needs more covering......its coming off....
Old 05-22-2008, 09:02 AM
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Default RE: twin engines models. why, how?

I built a Sr. falcon twin from plans. There is no concern about the engines running at the same rpm. as a matter of fact what sounds like a lot of offset in rpm by sound is no less then a thousand. I do not spend much time making sure the engines are in sync. I tune each individually, then start both and fly. I notice some trim concerns with an engine out but the main thing is do not hammer the throttle with one engine still running. While flying at cruising speed. I notice only a little deference. the biggest battle with an engine out is if you miss the runway and have to abort and fly around again. accelerating, climbing and turning all at the same time with an engine out is a task. I will slowly apply throttle, climb,level out, then begin to turn for another approach.
Old 05-22-2008, 09:06 AM
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Default RE: twin engines models. why, how?

A couple of pics.
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Old 05-22-2008, 09:40 AM
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Default RE: twin engines models. why, how?

ORIGINAL: bbbair
... IF you thought tuning one engine was tough try to get two working at the same time at exactly the same speed - otherwise you will get un even thrust and yaw will be induced.
There is no need to tune the engine to get them to run at the same speed. On the contrary, do not even try to get them to run at the same speed. Instead tune each engine individually using a slightly rich high speed setting and a safe idle speed.

Then you have the problems of a single enginr failure. This is tough if you are in a plane and you know WHICH engine failed - now you can compensate for the loss of power with lots of rudder - but in RC IF you hear an engine fail you don't know WHICH engine it was so ... which way do you push the rudder?? [X(] [] [:@] Often all you can do is kill the engines and dead stick in... [&o]
With experience you will learn how to handle one-engine out conditions. Most twins will fly just fine on one engine, at least good enough to make a safe landing. For twin-engine newbies my recommendation is to reduce the second engine to idle (or slightly above), keep the nose of the aircraft down and handle the situation as you would a single-engine aircraft dead-stick landing.
Old 05-25-2008, 06:14 AM
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Default RE: twin engines models. why, how?

rc flier is on target when he says match the strong engine to the weak one...don't try to match the weak engine to the strong one....in other words de-rate the strongest of the two engines.....as for single engine operation...the more powerful the engine is and the more distant from the center of the airplane the worse the adverse yaw will be....it also helps not to make a turn in the direction of the dead engine
Old 07-23-2008, 04:18 AM
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Default RE: twin engines models. why, how?

Flying twins is very cool and rewarding with the engines resonating with each other on a downhill run. Give it a go with a light twin with lots of wing and small engines first. Years ago I flew a 100 inch span DHC-6 Twin Otter powered by two OS MAX .28 FSRs. My first 18 take-offs had the right engine flame-out at about 50 feet. I simply pulled the remaining engine to idle and landed straight ahead. Only had slight damage on one landing. Reason for the flameout turned out to be a hard-to-diagnose vibrating throttle control cable. (Shook the throttle barrel back and forth fast enough to make it act like an air pump into the fuel line.) After fixing that, had four years of great and fun flying. You will have more challenges like starting and tuning two engines, but there is nothing like a good flying twin at the field!
Old 07-29-2008, 05:30 AM
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Default RE: twin engines models. why, how?

I have always wanted a twin but didn't want a high dollar scale model to spear in because of an engine failure. So I solved that by getting a cessna 336. Twin inline. No engine out issues.
Old 07-29-2008, 06:39 PM
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Default RE: twin engines models. why, how?

My building buddy, Flaps Laffert, and I are planning our 25th twin. We have made about every mistake you can possibly make so here's my take on flying twins.

1. As long as both engines are running, a twin flies just like a single. A heavy scale twin flies like a heavy scale single.
2. Reliability is king. You need reliable engines and you need to break them in before flying. We havde tried Magnum engines, GMS engines, Thunder Tiger engines and finally spent the extra bucks on OS engines. They seem to run more reliably on a twin than any other for us. The other engines run excellent on single engine planes.
3. Break the engine in first and fly it on a single engine plane before installing it on a twin. If you love trouble, put two new engines on your twin.
4. Use a fuel filter.
5. Stick to lower nitro fuel. 30% may make your engine screan, but 10% will keep running under adverse conditions.
6. Do not peak the engines out. One will quit. If you normally peak, then open 2 or 3 clicks, that is probably too lean for a twin. Peak and back off 4-6 clicks. You need to be leaving a nice smoke trail at the first of the flight. If you are a person who compulsively tweaks the engine every flight, go fly an electric twin.
7. Never, never adjust one engine with the other running. You will set it too lean. Crank one engine, set it, hold the nose up at full power for 20-30 seconds to make sure it keeps running. Shut down and start and tune the second engine. Crank both up and fly.
8. I never bother to synchronize my engines. It wastes my time and doesn't seem to add anything. I have flown planes with 1,000 rpm difference and, for a test, I flew one twin with a TT .46Pro/11-6 on the left and a TT .42GP/10-6 on the right. I couldn't tell any difference.
9. Out thrust works to help control when you lose an engine. 8 degrees is the magic number we have found. It looks like a lot, but you only lose 1% of you forward thrust.
10. Use a strong servo for rudder. I like a digital. Pull-pull is also best. If you use a pushrod, hold full rudder and try to straighten out the rudder. If the pushrod flexes, you need to brace it. When you need rudder on a twin, you really need rudder.
11. When you lose an engine, and you will lose an engine some time, immediately throttle back, regain control, then ease back to half power, holding rudder.
12. If your plane rolls over or does something weird, it's 99% you've lost an engine. Throttle back, recover control, then power up and land.
13. If you are flying a big, heavy scale twin and lose an engine, do not try to stretch the glide, land somewhere. It's better to tear a gear out than to snap, crash and ruin the whole plane.

A good starter twin is the Hobbico TwinStar with 2 OS .25LAs. The trim peels off, but the plane flies well. The engnies are GMS .32s. They're fast, but half the time, one quits. Check the landing, the right engine's out.
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