Problems in designing a small aircraft.

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Scheny

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Vienna, Austria
I wonder if others have come up with same the problems.
1. To get the spar carry through the fuselage will severely seem to cause plane to be bigger than intended.
2. There seems to be no way to get into the cockpit if everything else seems to be nice and tight.
3. Without pilot inside the plane seems to drop to its tail albeit being a nose wheel design.
I had exactly the same problems with my project, the Horus. If you compare the avatar pic (initial concept) on the left with the current version of the aircraft on my page (www.beast.aero), a lot has changed CoG-wise. For the spar there is not so much problem as it is behind the pilot, but the point 3 cannot be avoided.

The BD-5 that you mentioned, has a sandbag that is put next to the pedals to keep it straight on the ground. In my aircraft, i am adding a retractable "bikestand" in the dorsal fin.
 

Niels

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Aug 15, 2019
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Do you have a Thread on/about your sidevalved 2-stroke ; power
weight dimensions ?

Bille
I had to think it over.The valved two strokes can maybe do a god job for aircrafts that has all motor mass up front.

The thread here is for planes where total engine mass up front is not very good.
My proposal is to put an electric motor/prop on nose and put an IC genset on each wing.

In that case gensets can run much faster than suitable for valves.

There is a thread here

Gas electric drive
 

cblink.007

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K2W6, Maryland, USA
I wonder if others have come up with same the problems.


1. To get the spar carry through the fuselage will severely seem to cause plane to be bigger than intended.

2. There seems to be no way to get into the cockpit if everything else seems to be nice and tight.

3. Without pilot inside the plane seems to drop to its tail albeit being a nose wheel design.

---------------------------------

Many have bee able to by pass these problems in various ways.

Quickie is a good example...three wing design could be another.

BD-5 is a low wing and gets the wing into right place although the CG is a bit critical.

---------------------------------

Any ideas how to solve these "problems" ?
I can only mirror the replies of others. Study the plans of other aircraft, and see what worked great. Keep it simple where possible...because there will be a time to use bigtime brain power...even on a small & 'simple' aircraft design.

Based on your questions posted, it would appear you are new to this...and that is perfectly okay if you are. As such, I strongly recommend the book by Dan Raymer titled "Simplified Aircraft Design for Homebuilders". I encourage you to do your due diligence and homework, as we (and the internet for that matter) cannot provide you with all the answers you are seeking.

As someone who design & tests aircraft, I can tell you, with absolute certitude, that they call it "Aircraft Design" because every other four letter word is already taken. However, the end result is well beyond satisfying!

Best of luck to you!!
 

Riggerrob

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Sep 9, 2014
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Canada
And therein lies the assumption , that in a lot of different
fields of study ; the sum total of mans knowledge is doubling
at a rate of every year at this time, in history.

It's kinda Cool ; if ya think about it !!!

Bille
Many older patents were valid in theory, but they were impractical back then.
Now modern materials, modern micro-electronics and modern software make them practical.
 

bmcj

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Fresno, California
I've never been able to figure out what benefit that arrangement might have. The fin has to be stronger, meaning heavier, to take the thrust and gyroscopic loads, neither of which are insignificant, and added weight for no real gain is never wise.
I agree, and it may create balance issues. If you want a prop in the back, add an extended tail cone and a pusher prop on the centerline, far enough aft of the surfaces to get smoother flow. Throw in a dorsal fin for rotation protection of the prop.
 
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Riggerrob

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I agree, and it may create balance issues. If you want a prop in the back, add an extended tail one and a pusher prop on the centerline, far enough aft of the surfaces to get smoother flow. Throw in a dorsal fin for rotation protection of the prop.
That motor-on-top-of-fin configuration was marginally practical with heavy Lycoming IO-540 piston engines.
It might finally become practical with the latest generation of electric motors.
The original goal was to improve cruise speed by reducing drag by reducing the number of struts exposed to the wind. Others have experimented with retractable tip floats, retractable hydrodynamic steps, retractable hulls (see Blackburn during World War 2), but they all missed the point about seaplanes still needing large wings for STOL performance. STOL performance aka. slow landings and take-offs are needed to reduce pounding in waves. Pounding increases with the SQUARE of the velocity.
So try-as-they-might, they are never going to build a fast seaplane until they can achieve STOL performance with a small wing (cruise sized).
 

syclone

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Dec 2, 2011
Messages
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Savannah, GA/USA
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nose wheel​
8​
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batt​
0​
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canopy​
8​
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engine​
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eng mt​
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firewall​
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inst. Pnl​
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MLG​
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Wing​
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108.4​
5853.6​
Fuse​
40​
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Vtail​
8​
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1440​
Htail​
11​
186.5​
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BEW:
221​
95.7334841629​
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PL​
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108​
22680​
Fuel​
30​
81​
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MGW:
461​
100.362472885​
46267.1​
Here's a crude example that I hope is helpful. Sorry the picture is so crude, but for your early attempts a crude picture is sufficient. Set Fuselage Station (FS) 100 at the wing quarter-chord point and measure the distance to major components. On a small airplane, this will assure that all your weight and balance numbers are positive. Assign wts and FS numbers to each major component, put them into a table and compute the moments. The Basic Empty Weight (BEW) and Maximum Gross Weight (MGW) center of gravity are calculated. If your components and useful loads are properly located the cg will come out near FS 100.

This represents the first of many iterations. As you progress you'll add more and more details and the W & B will get larger and more precise.
 

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Sockmonkey

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Location
Flint, Mi, USA
Would it be possible not to carry the spar through the fuselage at all ?
Yes, if it's braced by struts like the minmax wing.
300.jpg

Ease of entry issues are one of the reasons I like the flea configuration.
lighthouse.jpg

As far as getting in and out is concerned, the Hm-1100 may as well be a car.

If you go for a low-wing through-fuselage spar, you can keep it from being too tall by having your butt between the spars with the forward spar passing under your knees.
 

Beragoobruce

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Oct 16, 2014
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Location
Blue Mountains, AUSTRALIA
The 1980's ARV Super2 resolved these problems thuswise:

Strutted wings forward swept app. 5 degrees allowing spar loads to pass through main bulkhead, behind pilot & pax

Shoulder wing with wing root at pilot's eye level. Excellent viz both above & below

Bubble canopy hinges upwards & rearwards giving good cockpit access.

Visibility in flight is excellent. Low panel line due inverted engine. For the rest, it's like flying in a goldfish bowl.


 

Niels

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241
The 1980's ARV Super2 resolved these problems thuswise:

Strutted wings forward swept app. 5 degrees allowing spar loads to pass through main bulkhead, behind pilot & pax

Shoulder wing with wing root at pilot's eye level. Excellent viz both above & below

Bubble canopy hinges upwards & rearwards giving good cockpit access.

Visibility in flight is excellent. Low panel line due inverted engine. For the rest, it's like flying in a goldfish bowl.


That is my favourite aeroplane as well if pulled by an electric motor on nose ,supplied from two gensets around strut -wing junction.

What is best in a crash?

Two live vires up front
or
running engine, tankage and fuel pipes?
 
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Lucky Dog

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Very light aircraft tend to design themselves, because the weight of the passengers and engine dominates the CG equation. Light aircraft design favors high-wing configurations, because you can balance the airplane, and then plop the passengers right on the CG and forget about it. (witness Phantom Ultralights) If you want a mid-wing, easy access design, you might consider a tri-gear pusher with a twin boom tail The forward wing spar should fall into place behind and below your shoulders in an upright, seated position and visibility would be stunning. Use thin fiberglass for the shape of your cockpit and build the structure with steel tubes, so you can triangulate sturdy hard points for the gear.

As an alternative; modern materials have emancipated designers from the old-school dictum of connecting stressed members in direct load pathways - to a degree. If you can piggy back your project with some experienced carbon composite engineers, you'll have more options to reroute spars and carry-through structures to accommodate seating and ingress with a minimum weight penalty.

1659110945907.png
 
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Sraight'nlevel

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Nov 4, 2021
Messages
386
The 1980's ARV Super2 resolved these problems thuswise:

Strutted wings forward swept app. 5 degrees allowing spar loads to pass through main bulkhead, behind pilot & pax

Shoulder wing with wing root at pilot's eye level. Excellent viz both above & below

Bubble canopy hinges upwards & rearwards giving good cockpit access.

Visibility in flight is excellent. Low panel line due inverted engine. For the rest, it's like flying in a goldfish bowl.


Indeed that looks very well organized concept.
 

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