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DLrocket89

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I know that Chris Heinz was working on and built the "gemini" twin, but that it isn't going to be released anytime soon. Are there any other experimental twins out there, either kit or plans?

Gemini:

GEMINI CH 620
 

PTAirco

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The success of the Tecnam twin surprised me; here is a four seat twin that is actually somewhat affordable to fly (if not to buy, at almost half a million), roomy interior, easy to get in and out of and to load, moderate speed and well behaved when one fan stops. Someone ought to get going on a similar, plans built type.
 

wsimpso1

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Burt Rutan had the Defiant, but decided to get out of the plans business. I would bet you could find plans for it... Story is it was an excellent and versatile bird.

Billski
 

autoreply

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I would expect Lancair or those alike to come out with a (conventional) twin as "the next step up". With 2X 350 hp one could keep up with the slowest microjets and beat them easily by range...
 

DLrocket89

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I would expect Lancair or those alike to come out with a (conventional) twin as "the next step up". With 2X 350 hp one could keep up with the slowest microjets and beat them easily by range...

That would be awesome. I was thinking more along the lines of an RV-10 fuselage attached to a pair of IO-320s or thereabouts...bascially, two 320s compared to one 540. *shrugs* one of my goals in life is to fly a plane that I built around the world over the course of a month or so.

Building a Mustang II right now, a guy from Australia made the trip to Oshkosh in 1999 I think with one, so it's possible, but the whole "single engine" thing scares me a bit.
 

autoreply

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How many seats / useful load?
It's a tandem seat dual (two engines, two pob). Projected top speed (@ max continuous power, 2x100hp) is 220 kts @ sea level and 275 kts from FL140 up.
Looks ambitious, but comparing it to existing designs (Venture, Lancairs) I think it's achievable :)
 

mz-

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Of course there's the new standard from Colomban: Twin-R
Two 100 hp Rotax 912 ULs and 450 kg empty mass means something. Four seater. 175 kts at 75% power. It's not pressurized of course so none of that turbo or high cruise stuff.
 

autoreply

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Of course there's the new standard from Colomban: Twin-R
Two 100 hp Rotax 912 ULs and 450 kg empty mass means something. Four seater. 175 kts at 75% power. It's not pressurized of course so none of that turbo or high cruise stuff.
Well you don't need those to go high up (I've been up to FL180 with nauseous oxygen only). Oxygen instead of pressurization and overpowered engines instead of a turbo. Your cruise speed will stay roughly constant once you go up high, but fuel consumption will seriously degrade, at FL180 your range can be almost twice that of low-level flight, flying on atmospheric engines.
At FL100 (where you can fly without oxygen all day) my speed increase is already close to 30 kts or 14% for the same fuel consumption (or a 30% lower fuel burn for the same speed)

Hadn't heard about the Columban, but it sounds like a great idea. It will be underpowered though and one-engine flight is going to be marginal at best, especially considering the rather high wing loading, the very low weight and the wide engines.
 

autoreply

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So, if I were interested in designing my own, where do I start? :ponder::para::whistle:
First of all, by thinking why you would want one. Twins need more power (has to fly once one engine fails), have serious conceptual and control issues and because of the aforementioned reasons are way more complex and expensive to both design, build and operate.

I personally can think of only two reasons to go the twin-route, reliability (in case an engine fails) and a lack of a suitable engine. If you're looking at a 700+ hp ship and you want a certified engine you might want two engines for example, though the single turboprop is by far the most popular option.
 

DLrocket89

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First of all, by thinking why you would want one. Twins need more power (has to fly once one engine fails), have serious conceptual and control issues and because of the aforementioned reasons are way more complex and expensive to both design, build and operate.

I personally can think of only two reasons to go the twin-route, reliability (in case an engine fails) and a lack of a suitable engine. If you're looking at a 700+ hp ship and you want a certified engine you might want two engines for example, though the single turboprop is by far the most popular option.
Reliability (over the open ocean).
 

AnxiousInfusion

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Reliability (over the open ocean).
(Pardon the rude nature) Or you could forget about the fear of engine failure altogether and take a single. Look at the statistics! Just keep in mind that no matter what you do, you still die in the end.:para:

You might be interested in looking at turbine or wankel singles.
 

autoreply

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(Pardon the rude nature) Or you could forget about the fear of engine failure altogether and take a single. Look at the statistics! Just keep in mind that no matter what you do, you still die in the end.:para:

You might be interested in looking at turbine or wankel singles.
You're completely correct, at least for a certified engine. Comparing a double certified piston with a single turboprop failure rates are comparable. While the piston isn't such a bad engine a major part of engine failures aren't limited to one engine. Fuel starvation, carb/prop icing, faulty parts and so on will occur to both engines at the same time. Also a piston is of course much more complicated than a turboprop will ever be, not to mention the much more expensive fuel (avgas is going way over 10 US$/gallon, jetfuel is less than half)

My major reasons for going the double route:
*No price penalty (2X912 or 914 is comparable in price to a single bigger engine)
*Completely split systems to prevent fuel starvation
*Much lower weight (per hp) and frontal area, thus seriously reducing drag
*My design only works with a relative low engine weight (otherwise the tail gets too heavy, engine has to move forward, requires a shaft, torsional vibration and so on)
*None of the other penalties of a twin (not asymmetrical, very low weight)

The only engines that give this benefit are (from my point of view) the Jabiru or the Rotax. Once you're settled with a Lyc/Conti it might be just as good to simply pick a twice as heavy, twice as expensive and twice as powerful (single) engine :)
 

bmcj

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Burt Rutan had the Defiant, but decided to get out of the plans business. I would bet you could find plans for it... Story is it was an excellent and versatile bird.

Billski
He also had the Boomerang. I don't believe it ever went to plans, but was reportedly far superior to the Defiant.

RutanBoomerang.jpg

Bruce :)
 

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