Problems in designing a small aircraft.

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John.Roo

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You are closer to Graz than me and Czech people have some very smart engine designer/manufacturers and very good electric people also.

My information comes from papers for session 5 from 2020.

smart two strokes
You are right - Graz is not that far from my house (+-500 km) and in CR are good engineers ;)
However small (10-15 kW) range extender is still not available, so if TU in Graz has some positive results than it is interesting for me - thanks for info 👍
 

Riggerrob

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If it's an amphibian, it means you don't need an additional pylon to carry the engine. It also puts the prop noise back behind the cockpit.

Sure, but you then need external wing bracing or very strong fuselage sides.
They are called ring bulkheads or ring spars, but tend to be heavy and complex to build. A few jet fighters use ring bulkheads. like the Lockheed CF-104 Starfighter. Even fewer commercial passenger planes use ring bulkheads, like the Burns light twin. The most subtle ring bulkheads were retrofitted when converting WW2 surplus twin-engined bombers (A-26 Invader and B-26 Marauder) to carry executive passengers who wanted full stand-up room, but their bomb bays were too shallow.
 

Bill-Higdon

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They are called ring bulkheads or ring spars, but tend to be heavy and complex to build. A few jet fighters use ring bulkheads. like the Lockheed CF-104 Starfighter. Even fewer commercial passenger planes use ring bulkheads, like the Burns light twin. The most subtle ring bulkheads were retrofitted when converting WW2 surplus twin-engined bombers (A-26 Invader and B-26 Marauder) to carry executive passengers who wanted full stand-up room, but their bomb bays were too shallow.
Also used in the Gloster Meteor & English English Electric Camberra/Martin B-57 wings spars
 

Bille Floyd

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Everything new is built on everything old. You need to know old, before designing new.

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
 

Riggerrob

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Also used in the Gloster Meteor & English English Electric Camberra/Martin B-57 wings spars
Correction, British-built Gloster Meteor Mark 4 used straight spars, but Martin/English electric B-57 used ring spars.

Meteor used early jet engines with centrifugal compressors while Canberra used more modern axial compressors.

This was back during the early days of jet flight when fighters (e.g. Meteor) and bombers still used jet engines with centrifugal (same say radial) compressors. Since they did not understand intakes very well, they just dumped all the incoming air into a plenum chamber then allowed the centrifugal compressor to suck in random molecules of air. This made more sense on second-generation engines which had double-faced centrifugal compressors. While the front compressor face might have benefited from smoother inflow, that was totally lost to the rear compressor face. So Gloster Meteor just left incoming air to find its own way around a rectangular wing spar .... because centrifugal compressors are relatively forgiving of turbulent inflow.
Part of the reason for co-locating wing spars and thrust lines was to minimize pitch changes with throttle changes. They also mounted engines a half propeller diameter out on the wings "because that is the way we have always done it."

Since early jet engines were such a large fraction of the empty weigh, they needed to be balanced by locating engines near the center-of-gravity, which is why Meteor and Canberra installed their engines between wing spars.

Later they learned to simplify wing structure by mounting engine intakes below spars (see Avro Jetliner and Boeing 737).

Hint: my first job - as a young RCAF technician was overhauling Nene 10 engines with centrifugal compressors. Then we installed them in CT-133 Silver Stars that were even older than me. The RCAF kept their fleet of rugged, dependable T-33s flying into the 21 st century.

Was that enough obscure information about antique jets ... for this audience??????
Hah!
Hah!
 

Bille Floyd

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For a single seat:
A 8kg 30kW electrig motor up front
and two 15kw/10 kg range extenders from battery cars,one on each wing.
Pilot somewhere in between.
People at TU Graz in Austria are seaching for best range extener configuration.
Results to be shown on a two stroke conference in september on a conference in Sevilia,Spain.
My sidevalve two stroke was favourite in 2020 so I am biased.
Do you have a Thread on/about your sidevalved 2-stroke ; power
weight dimensions ?

Bille
 

Riggerrob

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Most modern bizjets run the spar and wing below the fuselage.
Yes, a quick and simply solution, but it creates a fuselage that is as deep as the pilot's spine plus the depth of the wing spar, plus the depth of the "canoe" to streamline the wing root to the wing.
... The original poster was trying to avoid an overly deep fuselage.
That "canoe" is more of a box with rectangular cross-sections. 90 degree angles are the easiest to streamline after the fact.
 

Bille Floyd

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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.
The "prop on tp of fin" appears to work quite well , on
the Sunseeker Duo .
from :

Bille
Sunseeker Duo .jpg
 

Vigilant1

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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.

If a designer has plans to achieve laminar flow over the fuselage, a tractor prop in the nose of the plane is not an option. A pusher prop behind the fuselage pod often is hard to get right (prop in turbulent air, downwash from high or mid wing = different AoA for prop blades on each side, etc). An electric motor is small and not too heavy, so maybe mounting it on the fin seemed a good option. As you say, it does have structural "issues." Also, weight at the end of that tailboom will affect spin modes and recovery. Also, expect a nose down pitch change with power reduction or loss (which is generally an okay thing).
 

John.Roo

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The "prop on tp of fin" appears to work quite well , on
the Sunseeker Duo .
from :

Bille
View attachment 128068
Sunseeker Duo is really great project 👍
 

John.Roo

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These guys make a 10-15 kw e-motor ; and also build
a folding prop for it :
scrool down to engine ---
HPD12 12kWc./15kWp. @ 3.75kg; 2180 rpm
from :

Bille
Products of Mr. Geiger are TOP 👍
Unfortunatelly prices in EU are much higher...
For example 1 kWh of battery capacity for airplane costs far over 1 000 EUR (actually is bank rate between EUR and USD 1:1). It means that for complete propulsion for small airplane you pay arround 20K EUR...
 

Niels

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

Bille
not really but if You do some searching on two cylinder opposed two strokes for direct drive drone engines and list cylinder volume,max claimed power/revs plus mass we can make a good guesstimate as specific mass of eletric machines can be found as well.
 

Bille Floyd

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not really but if You do some searching on two cylinder opposed two strokes for direct drive drone engines and list cylinder volume,max claimed power/revs plus mass we can make a good guesstimate as specific mass of eletric machines can be found as well.
I will do that ; Thanks !!

Bille
 

Bille Floyd

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Messages
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Products of Mr. Geiger are TOP 👍
Unfortunatelly prices in EU are much higher...
For example 1 kWh of battery capacity for airplane costs far over 1 000 EUR (actually is bank rate between EUR and USD 1:1). It means that for complete propulsion for small airplane you pay arround 20K EUR...
How about just the motor, and folding prop ; maybe
find another source for controller and battery ?

Bille
 

BBerson

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Port Townsend WA
Yes, a quick and simply solution, but it creates a fuselage that is as deep as the pilot's spine plus the depth of the wing spar, plus the depth of the "canoe" to streamline the wing root to the wing.
... The original poster was trying to avoid an overly deep fuselage.
That "canoe" is more of a box with rectangular cross-sections. 90 degree angles are the easiest to streamline after the fact.
Right. But a bump just for the main spar is less wetted area than a full length deep fuselage.
My design is a sit on top of the spar. I could move the seat back and below the main spar. But that will reduce downward visibility in front of the wing. Or I could move the spar root behind the pilot and with forward swept tips for balance. I am aware of the problem, but don’t have an easy answer.
 
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