First ideas for a mash-up homebuilt.

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manhaes

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Jul 8, 2021
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Hello All,

After many months of analyzing many aircraft projects, I started to put together a list of what I liked of each one of them.

The resulting sketch seen here is a combination of elements from the following planes: J-1B (cabin), Cri-Cri MC 15 (twin-engines), PIK-26 (wings), and Airbus E-Fan (engines localization).
The objective is to have a Home-Depot airplane, mainly constructed from wood, with great visibility, and the possibility of different motorization options (IC, Jet, or Electric).

Its working name is "Short Bigeye MM-01", with the nickname of “Don Cri-xote.”

Now, starts the real project work of transforming this idea into a technical plan. I never built a real aircraft before. Only many RC models.
My goal is mainly to create the technical project and, later, build a large RC model for tests.

I will appreciate critiques and suggestions on major flaws or problems that one of you might catch based on the 3 views posted here.

Thank you all in advance!
MM-01 - 3 Views.jpg
 

TiPi

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Hi manhaes, very nice. Do you have some specs for weight, engine power and speeds? What aircraft class/category will this design fit into (SSDR, ULM, LSA, other)?
Have you done a CofG calculation? The pilot position seems to be a bit too much forward of the wing?
 

pylon500

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Probably should try to superimpose a human figure of correct scale (like the Russian drawing), as TiPi suggests, you pilot position looks a little too forward, or or pilot assumed to be a little too small?
 

blane.c

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Have you chose an engine(s)

Would it be possible that you would get better elevator effectiveness when moving the throttle forward if the horizontal tail was lowered into the propeller blast?
 

Lendo

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You may laugh, but as an Instructor once suggested to me was, if you push a C172 Tail down, when it's fully loaded and it come back up, it's safe to fly. I've never established it that's true or not. I wonder about the Weight and Balance, with fuel use.
George
 

pylon500

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You may laugh, but as an Instructor once suggested to me was, if you push a C172 Tail down, when it's fully loaded and it come back up, it's safe to fly. I've never established it that's true or not. I wonder about the Weight and Balance, with fuel use.
George
That's probably a good 'Rule of Thumb', but more importantly is, if it doesn't come back up, it's time to drag out the W&B chart...
Have you chose an engine(s)

Would it be possible that you would get better elevator effectiveness when moving the throttle forward if the horizontal tail was lowered into the propeller blast?
This sounds good in theory, but doesn't consider the change in handling quality should you suffer an engine failure.
In that position, you are going to be busy enough without wondering why the controls feel wrong.
There's also the propellor slipstream/vibration fatigue point to consider.
The tail arm /volume is rather short and the main gear is too far forward (assuming the cg is at 25% wing chord), it will tip on its tail.
Tail area looks... adequate... but tail moment is a little short, not so much for the horizontal, but the fin/rudder combination has a very limited moment to handle the two engines, and I'd also question the area of the vertical surfaces to handle all the forward 'keel' area of the cabin?
Main gear will make rotation and flare easy, but yeah, could be a little further back.
As for sitting on it's tail, once the pilot gets out, this will happen anyway, all BD-5's do this, unless dummy weights thrown into the cockpit when parked.
 

manhaes

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Thank you all! I am still reading each one of your comments and suggestions. Based on what I have already read, I made some changes to the sketch. @Goflybefree suggestion to take a look at the Phoenix M-5 was a breakthrough for me. Thanks a lot! I kept +/- the same dimensions of the M-5. Please, let me know what you think...
 

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pylon500

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On paper, it's going to look a little 'guppy', but all those shapes / moments / areas look about right.
As for 'fine tuning' the layout, you may save a little frontal area if you can pick a 'waistline' (like just below the canopy line), and then cant the lower sides in a little, probably only 15~20º to give a slightly hexagon cross section?
The cons would be two more joins down the underside, more head scratching on the development of the side profiles, bit less room for your butt, but a payoff in the aerodynamics I think.
Might pay to look at the rudder to see you have enough area to handle asymmetric thrust, baring in mind the airflow off the top of the fuselage may not be very smooth...
 
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