Why isn't the push/pull twin more popular ? What you say.

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Vigilant1

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I'm just waiting for you or someone to start construction of a BeetleMaster.
Tired of holding my breath. :)
I think it would be quite a plane. It would climb great and be an economical cruiser (the engines would live a LONG time at the low projected manifold pressure in cruise, very lightly loaded). Now, we just need to finish off a "few" design details, fire up the torch and get out some clecos and put one together. ;)
 
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Pops

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I think it would be quite a plane. It would climb great and be an economical cruiser (the engines would love a LONG time at the low projected manifold pressure in cruise, very lightly loaded). Now, we just need to finish off a "few" design details, fire up the torch and get out some clecos and put one together. ;)
You first. :)
For me it would be tube fuselage covered in CF shells. Aluminum wings and booms and tails.
 

jedi

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“Why isn't the push/pull twin more popular ?”

Every airplane designer struggles with where to put the propeller. The typical twin solves that problem by placing them on the wing eliminating the fuselage from the slipstream and improving forward visibility with some improvement in reduced noise and vibration. In addition there is the advantage of the blown wing.

The push me pull you configuration doubles the problem of how to incorporate the engine/propeller into the fuselage design. Obviously it can be done but there are twice as many decisions and compromises to make.
 

Turd Ferguson

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Going smaller still, we looked at a single place plane design (MicroMaster) powered by two 28-30 HP industrial engines It also appeared possible to end up with a fun plane with safe single engine performance.
You would need enough power to have at least Cessna 150 takeoff and climb performance with one engine Inoperative. That would make it safe to fly. The second engine would make it a blast to fly.
 

Vigilant1

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time to resurrect the Dave Ganzer Gemini?

View attachment 129949
If it can really fly safely on one 65hp engine, it would be a fine candidate for two of Pops' new flywheel engine conversion jobs (in 1915cc). There, we just saved even more money, and some time machining the case, etc!

The CNC routers available today would make quick and accurate wing cores and foam fuselage bulkheads/formers.. Or, go "hybrid" with CNC hotwire cutters. Or, just buy a friend some pizza for his help and do it the old fashioned way.
 

Vigilant1

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You would need enough power to have at least Cessna 150 takeoff and climb performance with one engine Inoperative. That would make it safe to fly. The second engine would make it a blast to fly.
My rough numbers indicate the Beetlemaster (and Micromaster) would climb single engine at MTOW about like a real C-152 at MTOW on a hot day. Not the C-152 POH numbers, but what I see in real life on the VVI with a sweating, heavy instructor aboard.
 

Vigilant1

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time to resurrect the Dave Ganzer Gemini?

View attachment 129949
I've seen some sources that indicate the plane used 65 HP VW Type 4 engines. If that's right, then substituting Type 1 engines would be expected to reduce empty weight by about 50-75 lbs, which is considerable.
It's hard to find much info on the Gemini. Dave Ganzer reportedly was going to offer plans, but I don't think that ever happened. I'd like to have a set. If the wing panels are actually the same as the Long-Eze, that would simplify things a lot.

There are many positive things about these slippery canard designs, but, they aren't known for low speed touchdowns or rough terrain ground ops. IMO, having a second engine to allow touchdown to be on a runway if one engine quits would be a plus. Obviously, there are many factors to consider.
 
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Brünner

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Hi Dana, sorry, agree to disagree - for me (as an IT guy) a single point of failure is still a single point of failure...
A single manufacturing defect could cause a problem with engine or prop, and that is it (over mountains at night or cold sea).
Although one the 337s went down due to double engine failure! I think it was due to very low temps? Flight in the north...

Going back to the OP's question - I think what people listed here sums it up: too many design problems. And both most known a/c in the class have failed to deliver (337 + Adam 500)
A certain Lindbergh argued that multiple engines represented multiple failure points, not to mention extra workload for the pilot/s and extra weight to carry around for the second donk. He steadfastly refused any advice and suggestion to use a twin for his historic trip, and we all know how it went.
His second aircraft with which he traveled extensively with his wife was also a single and it performed impeccably.

My personal opinion is that when Cirrus came up with the Caps system, the piston twins were made obsolete.
 

arj1

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My personal opinion is that when Cirrus came up with the Caps system, the piston twins were made obsolete.
For me, not over the mountains at night, not with low clouds (~200ft) and not over long stretches of water. Otherwise - yep!
 

Cardmarc

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This airplane seemed to have the single engine reliability, was fast, and had looks that killed (literally for its intended victims and its pilots):

Do335.jpg


All kidding aside, I think the answer to Pop's question is more fundamental to anything technical:

People who own twins want speed, carrying capacity, and roominess. An extreme example, but with the exception of its single seat cockpit, the Dornier above was packed from spinner to spinner with either fuel or engine systems.

The Cessna Skymaster has the same issues with useful load and cabin space. The cabin space and useful load is very similar to a Centurion...and is in fact slower! I guess the interference from all those tail booms and struts really did a number on its drag coefficient.

That, and that the target audience for twins being more well-to-do individuals who want to take 2 of their best buddies and their spouses (who are probably leery of flying and will bring lots of luggage), they're going to want something that's fast, roomy, and looks like an "airplane".

I think the Adams A500 had the best chance to break the mold, but they just never attained the critical mass to make it happen.
Yup, the wwII GERMAN Dornier DO-335 Phiel (Anteater) was a fine (fastest) wW ii piston plane. A composite replica would be the cats meow.
 

PMD

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Of course, airplanes break down into several different groupings: those you can go to the corner store and buy, those you THINK should have been built, and finally those the most ambitious of all actually DO build. I am too old to head to the latter, and too poor to exploit the first, so leaves me dawdling in the middle category while working on other things aviation. When defining the ultimate personal single seat, IMHO nothing comes close to Taylor Mini Imp. To me, covers almost all of the realistic bases for that carrying capacity and a great home for 100 HP. Moving up to 2 seats, a 330LT would be ideal, and no need to design it as with a mere half mil you can buy a low time used one. Efficiency takes a back seat to pure fun for that one. BUT: when we get to the concept of 4 to 6 and long range, mid to high altitude IMHO efficiency and safety (for other people's lives) come back to the top of the list, as these are REAL transportation tools. I certainly understand the intent of the 337 while vastly preferring a 600A when it comes to real world first group. When I move that mission into the second group, though, ALL of the possible efficiency things pull at my heart strings. The safety thing DOES come down to 2 failure prone engines since one of such failures DOES NOT need to represent a forced landing - and night, mountains, water and remote areas have always been my "normal" theater of ops. While a Da62 comes close, I really want to have pusher props (even counter-rotating!!) to allow clean fuselage (such as in Celera). As much as I LOVE the RED 03 it comes down to the one single engine and IMHO not for me (or I suspect they are going to find much of anyone else who wants to cross a mountain range, the high Arctic or an ocean. That brings me to 2 x 400HP pushers out on the wings (vertical inline engines to keep less nacelle on the wing). Think of a smaller diesel Piaggio. That configuration keeps fuselage clean, wing more clean than tractor, covers powerplant redundancy and propulsive efficiency.
 

Spaghetto

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327 Baby Skymaster - reduced scale four-seat version of the 337, with cantilever wings replacing the 336/337 strut-braced configuration. It first flew in December 1967. One prototype was built before the project was cancelled in 1968 due to lack of commercial interest in the design. The prototype was delivered to NASA to serve as a full-scale model for wind tunnel testing. It was used in a joint Langley Research Center and Cessna project on noise reduction and the use of ducted versus free propellers.



Murphy, Daryl (2006). "The Cessnas that got away". Archived from the originalon February 27, 2009. Retrieved December 22, 2008.
 

Vigilant1

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327 Baby Skymaster - reduced scale four-seat version of the 337, with cantilever wings replacing the 336/337 strut-braced configuration. It first flew in December 1967. One prototype was built before the project was cancelled in 1968 due to lack of commercial interest in the design. The prototype was delivered to NASA to serve as a full-scale model for wind tunnel testing. It was used in a joint Langley Research Center and Cessna project on noise reduction and the use of ducted versus free propellers.



Murphy, Daryl (2006). "The Cessnas that got away". Archived from the originalon February 27, 2009. Retrieved December 22, 2008.
Interesting. Two IO-320 engines. It was unpressurized. A good looker, and they arranged things to keep the pilot ahead of the wing leading edge for great visibility.
Hopefully, Cessna learned enough from the Cardinal to avoid the inadequate tail effectiveness during landing (or maybe the weight of an engine back there helped with that 😀).
Photos here. (Facebook page, but Facebook membership not reqd)
 

PredragVasic

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why isn't the push/pull twin design used more ? Pros and cons

I hadn't seen this mentioned but I believe it may well be a significant factor why the C-337 and similar push-pull concepts aren't nearly as popular as C-182: engine noise.

If you sit behind a single engine, you accept the noise you get from it, because that's the price to pay for a cheap airplane. When you "upgrade" to twin, you expect it to be much less noisy, with the engines being outside the fuselage, a bit of a distance away.

Being tightly sandwiched between two engines that are inside the fuselage and make it resonate loudly is even worse than sitting behind a single engine.
 

dog

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Scaled down Dornier Do 18g,three seat tandem,
side windows slide back,doors fold down
level with the sponsons,stand or sit on them
pair of 100hp would be ok if it was kept realy
light
 
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