Twin Dak

Martin H

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Ok on the Adventurelounge site (http://www.adventurelounge.com/aircraft/full/ i Found this patent for what looks like a twin C-47 type aircraft dated 1941.

http://www.adventurelounge.com/aircraft/full/design/054.html

being a member of the IPMS (UK) C-47/DC 3 sig as well as leader of the IPMS(UK) what if? sig i decided to have a go and see what it would look like in 72nd scale.

(the end result)
twindak003.jpg

My only problem with this project, is that 3 engines doesnt seem enought to lift this beast off the ground, and what role would it best suit. Troop transport or Glider tug? and would it be needed anyway?

If u think this one is fun, u should see the 4 body version from the same patent claiment.
http://www.adventurelounge.com/aircraft/full/design/058.html
 

Tophe

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If there is not enough power, add a central pusher engine: central push-pull with 4-engines as total. No? As there is less drag and weight than 2 complete C-47, this would be overpower, increasing speed.
Otherwise, how to have 3-and-half engines?... A tiny Ranger engine could do it, but that would not be easy for spare parts to have 2 different engines to check/repair, no?
 

elmayerle

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A pusher engine would be the easy solution to adding a fourth engine, but I'm not so sure it'd work from the aspects of cooling a pusher engine and ground clearance for the prop with the aircraft being a taildragger. I'd suggest that a center section more like that of the He-111Z would be more probably if three engines were insufficient.

*smile* Of course, the other alternative is to convert this three-engined bird to a five-engined one with nose-mounted engines on both fuselages.
 

Tophe

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elmayerle said:
A pusher engine would be the easy solution, but I'm not so sure it'd work from the aspects of ground clearance for the prop with the aircraft being a taildragger.
You were very right, Evan: pusher propellers are a problem with tail wheels: no ground clerance. So it would be possible to use counter-rotating propellers of reduced diameter:
r_dc3pp_y.jpg

Thanks dear engineer!
 

frank

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What would reducing the diameter of counter-rotating props accomplish? Regardless of rotation, you'd need the same diameter prop for the same power output. Why not just use a smaller diameter prop with more blades &/or wider chord blades?



Tophe said:
elmayerle said:
A pusher engine would be the easy solution, but I'm not so sure it'd work from the aspects of ground clearance for the prop with the aircraft being a taildragger.
You were very right, Evan: pusher propellers are a problem with tail wheels: no ground clerance. So it would be possible to use counter-rotating propellers of reduced diameter:
r_dc3pp_y.jpg

Thanks dear engineer!
 

Tophe

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I am not sure at all, I just repeat what I heard...
see for instance http://www.tgplanes.com/Public/snitz/topic.asp?TOPIC_ID=774
Engineer, could you confirm: with the same diameter, isn't a counter-prop device more powerful than a simple one? (so the same thrust would require less diameter with counter-prop)
I am sincerely willing to change my mind if I was wrong.
 

frank

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Oh, I see, you mean contra-rotating! I don't think that would help much in this case.



Tophe said:
I am not sure at all, I just repeat what I heard...
see for instance http://www.tgplanes.com/Public/snitz/topic.asp?TOPIC_ID=774
Engineer, could you confirm: with the same diameter, isn't a counter-prop device more powerful than a simple one? (so the same thrust would require less diameter with counter-prop)
I am sincerely willing to change my mind if I was wrong.
 

Tophe

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elmayerle said:
I'd suggest that a center section more like that of the He-111Z would be more probably if three engines were insufficient.
Dear Evan, here is your 5-engined Twin C-47 inspired by the He 111Z… Maybe this was technically the best as 20th century's machine, but as 21st century's model, there is a problem: it would require 3 C-47 kits instead of 2 for MartinH's wise one…
r_dc3z_c.jpg
 

elmayerle

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I honestly think you'd have needed a conversion to tricycle gear to use pusher propellers successfully. With taildragger gear, besides the possibility of ground strike by the pusher propellers, you would also run considerably risk of serious damage to the pusher propellers from rocks and debris thrown up by the main landing gear.
 

Tophe

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I have tried: lengthening the noses, for a room to retract the nose wheels, and slightly moving the wing backwards, for balance. Is this better?
r_dc3pp_z.jpg
 

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