dual engine plans?

rubber314chicken

rubber314chicken

Pre-takeoff checklist
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Rubber314chicken
Unless you build it like the Air Cam ( http://www.aircam.com/ ) which can actually climb on one with the other NOT feathered (windmilling props create enormous drag) you will be descending on ONE engine.

In that case, a single bigger engine would be a wiser choice, more economical and better power to weight as well as fuel efficiency.
 
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what makes that plane climb without a feathered propeller? What about having a manually adjusted propeller angle, wouldn't that allow it to be feathered (and reversed)? Or does the engine need to have something additional to support an adjustable pitch prop?
 
rubber314chicken said:
so, I came across this engine: http://www.sonexaircraft.com/eshop/cart.php?target=product&product_id=16424&category_id=268 while browsing some stuff on home built airplanes (I've always wanted to build one, but I'm thinking I won't until a while after college), and I looked at it, and I thought two of those would make a mean double prop machine. Anyone know of any plans/kits for something like that?
Click to expand...

A Tailwind with a rotary engine will still be faster, less maintenance, safer, and cheaper.

Dan
 
okay, I guess you all win... I was looking at it with an initial investment pricing, not considering the cost for more gas, more maintenance, and feathering props..... but I still think it would be safer because there is a 1/4 chance of losing all power compared to a single engine plane.

but I guess there really is no reason to re-invent the wheel.... Though I'd still like to build that engine sometime, just so I can say I've built an airplane engine.

but if 2 engines are not as well of as just one (or is it just this case) then why does beechcraft make so many dual engine planes?
 
rubber314chicken said:
what makes that plane climb without a feathered propeller? What about having a manually adjusted propeller angle, wouldn't that allow it to be feathered (and reversed)? Or does the engine need to have something additional to support an adjustable pitch prop?
Click to expand...
It's fixed props. What makes it able to climb w/o feathering propellors is that the engines are VERY close to centerline (little rudder drag during SE ops) and the aircraft is overpowered. Wing loading is near 7 pounds/hp. One one blower it's 14/hp, about like a C 172.

But on anything that has a shell (translation=WEIGHT) fuggedaboudit. There was a little two seat twin, called the Wing Derringer (fixed props), which would just not climb on one. They sold about ten, or some miniscule number.
 
rubber314chicken said:
okay, I guess you all win... I was looking at it with an initial investment pricing, not considering the cost for more gas, more maintenance, and feathering props..... but I still think it would be safer because there is a 1/4 chance of losing all power compared to a single engine plane.

but I guess there really is no reason to re-invent the wheel.... Though I'd still like to build that engine sometime, just so I can say I've built an airplane engine.

but if 2 engines are not as well of as just one (or is it just this case) then why does beechcraft make so many dual engine planes?
Click to expand...

You can build that engine and say you built a Volkswagon engine, which really is a long way from an aircraft engine. If you want to use a VW in an aircraft, you really need a 2:1 reduction drive so you can run the engine at 4000 rpm for a 2000 prop speed at cruise and 4800 for a 2400 max T/O power. At 4800 you can get 260hp out of those engines pretty reliably.
 
Before you say you can get 260 HP out of a Volkswagon engine reliably, I respectfuly suggest you put one on a Dyno and run it that hard for several hours.

I think (if you can even get that much, or even half that much) you will end up with a melted puddle of aluminum on the floor, before very long.

Jim in NC
 
Yeah, I have to go with Jim on the HP output. I used to build a fair number of VW 2180s. In fact I've got a brand new one in peices right now if someone wants to build it (hint, hint). I sure wouldn't charge any $6500 for it either.

With the intake pictured, not knowing anything about the cam, or intake runners, 100HP would be a good rule of thumb @ around 4200RPM. the Sonex people quote 80HP prolly at 3600RPM. I got one up to 245HP for a while with stage 5 heads, dual 45mm Delortos and a very aggressive cam. it lasted for three seasons of sand dune action, which was pretty typical.

I've seen them spit plugs, spit heads, drop valves, heck just about every failure mode you can think of. Tehy put out pretty fair torque due to the boxer design, just like real aircraft engines. Not my favorite engine for an aircraft.
 
One of the guys here at work has a Bug, can't remember exactly what engine is on it, but it's also turbocharged. His last dyno session he was making somewhere over 300 hp at the wheels on under 15 psi boost. One thing, though. It's a "street" car that is really a drag car. It only needs to last 10 seconds at that power, not 1500-2000 hours running at 60-80% power for most of the time.

When it comes down to it, you'll have a hard time finding a car engine that is going to have the capability to do what an aircraft engine will do, at least unless you want to run ridiculously low power settings all the time.
 
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