WesWorld

For the 4th time again; The historical J.10 had swept wings. This probably wasn't to do with reducing drag but altering the centre-of-gravity, like on the C-47 and Me-262.

I know the J.10 doesn't have true swept wings.

However given Italy's and Germany's wind tunnel resources I'd expect them to develop such wings earlier than GB and even the USA. They simply have the resources to research the area more efficently and draw the right conclusions. If the designers listen to the advice is another story.

Reading an offical SAAB book they claimed the USA largely ignored delta and swept wing research largely because they could not read German! That's why, SAAB argues, the Swedes having had close contact with German firms was in a better position to benefit from this data. Enter the Draken...

So if its because of a center of gravity issue I could life with it even if its still way early in mid-30s but I would prefer not to bring swept wings into WW reality as the "center of gravity argument" would just open too many doors...

It wasn´t until the early 1950s until the Americans really began to study swept wing designs and the mathematical theories behind (X-5 project based on Messerschmitt Projekt P.1101 with variable wing geometry to test different angles; first flight X-5 21.06.1951). Prior to that there had been wind tunnel tests but nobody really understood the aerodynamic effects really. Hence all first and second generation jets except the Me262 had standard wings (Gloster Meteor, Hawker Hunter, Bell Aircobra, Bell X-1, He162 etc.)....

Again my arguement is typified by the C-47 with swept wings.

The wings on the J.10 are totally unsuited to transonic flight as they're so thick.

Swept wings for aerodynamic reasons would come around later when there are engines powerful enough to reach 800km/h + (i.e. GTEs) but the preliminary research in the field was already being done in the 1930s by Italy and Germany, and for higher speeds with Italy having the world's only supersonic wind tunnel. There was the Volta conference in 1936 in Italy especially dealing with high-speed flight. Of more interest to me personally for this is Ing. Crocco's design for a propellor incorporating sweepback towards the tips. I've always wanted to try and break the sound barrier with a prop-driven aircraft.

A "SWEPT" wing requires both Leading and Trailing edges of the wing to be beyond 90 degrees to the fuselage. The ME 163 was the first production fighter to use such an arangement.

The J.10 is , like the C.47 and the F15 and F16, a heavily "TAPERED" or "DELTA" wing as their trailing edges are NOT beyond 90 degrees, in all these cases they are exactly perpendicular to the flight axis.

The planform of the J.10 is not that radical for the period, just look at the Westland Lysander, that IS a radical shape for the period.

RA,

The Iberian competition made me look again at the CR.35. In this 1934 airplane thread, you indicated that the

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Pre-Production with Semi-Asso engine (19L inline 6, one block of Asso 1000) as its available and does work.

Early series staying with Semi-Asso engine

Late series (35/36) moving to L1406 engine (720hp)

38/39 production aircraft refitted with uprated (996hp) engine with more emphasis on low altitude performance as newer and better fighters appear. This version also includes bombracks and a ventral 25mm cannon. (Pictured)

Edit; I just had a play with fitting the Asso XI engine (960hp) and a larger fuselage to accomodate it. Had to increase the weight a bit but it actually works quite well. Might end up using that instead.

You also stated

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The tolerances for desmodromic valves make them expensive to manufacture and unsuitable for mass production.

So... the encyclopedia is showing the L1406 engine, not the Asso XI, but it's also showing a 800lb weight increase and 960hp, not the 720 discussed for the 1934-35 L1406. Did you go with the Asso XI? If so, could you be so kind as to let us know what the displacement, weight and size of the engine is? Or just post the planebuilder that you are using?

The bis version chosen for production mounts the Isotta-Fraschini Asso XI engine which gives 960hp@14000ft and weighs 513kg.

Characteristics:

Weight (maximum) 3,500 lbs
Weight (empty) 2,895 lbs

Length 24 ft
Wingspan 28 ft
Wing Area 140 sq ft
Sweep 5 degrees

Engines 1
Isotta Fraschini Asso XI
Piston

965 hp
at 14,000 ft


Crew 1

Top Speed 349 kts = 401 mph
at 14,000 ft
Mach N/A

Operational Ceiling 42,000 ft

Range 400 nm = 461 miles
with 108 lbs payload
112 lbs released at halfway point

Climb 4,406 fpm

Cruise 190 kts = 219 mph
at 14,000 ft

Corner Speed 236 KIAS =
236 kts at 0 ft
Mach N/A
Turning Rate 35.5 deg/sec
Radius 1,287 ft



Internal Data:

Intake / Fan Diameter 9 ft

Bypass Ratio 96

Engine Weight 1129 lbs
Overall Efficiency 23 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 350 kts
Wing Ultimate g Load 12.00 g
Wing Taper 0.8
Wing Thickness at Root 1.2 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 6 ft
Diameter 3 ft
Fullness 0.5

Fuselage Diameter 3 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 70 percent
Unstreamlined section 0.8 sq ft

User equipment 250 lbs

RA,

Thank you for posting.

According to this page,
Engine

the Isotta-Fraschini XI RC40 engine weighs 1322lbs, and is fractionally bigger than 3' in frontal area.

My preference would be for rough field landing gear, and I'm still not keen on the almost-delta .8 wingform. I don't see how you're going to fit another 400lbs of 20mm cannon and armor to satisfy the Iberians.

Other than that, very lean mean machine.

I'm not sure where that data is from. The Asso XI was a V12 of 140x170 giving a displacement of ~31L. My figures show a weight of 513kg. Its not really a delta wingform. I just fiddled with the numbers to give proper leading a trailing edge angles (5 and 20 IIRC).

Armour consists of an 11mm plate behind the pilot. Having the cannon firing through the prop saves considerable weight as you can use the engine as an inertia block to minimise the recoil forces.

This is odd.
The page would seem to have the right engine, yet your 513kg isn't unreasonable either, as the Hispano-Suiza 12Ys were about the same p/w.

The page lists the RC40 at 1991cu in displacement or 32.6L, roughly about right. The dimensions and weight appear reasonable for the period as well.

I must be misunderstanding what you mean by 140x170, because that would bes 55x66 inches or 4.7x 5.6 ft, which is far larger than most of the 31L engines, and wouldn't fit with either weight, or fit in your fuselage, but the web page's dimensions would almost fit.

As for deductions for inertial blocks- that probably needs a rule of thumb so all of us can be on the same page.

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I must be misunderstanding what you mean by 140x170

140mm bore by 170mm stroke rather than the 146x160 given. The data given for the Asso 750 is also incorrect. The engine should fit into the fuselage but there might have to be bumps over the cylinders as in the Griffon Spitfires.

Armament: I'm not really happy with planebuilders assumptions especially for large calibre weapons.

Hard-mounting a cannon to the engine has it's downsides: it means that the gun will receive all the vibrations that the engine has, which is not necessarily good for reliability (see the difficulties BFW had with trying to engine-mount an MG-FF)

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Originally posted by Red Admiral

Quoted

I must be misunderstanding what you mean by 140x170

140mm bore by 170mm stroke rather than the 146x160 given. The data given for the Asso 750 is also incorrect. The engine should fit into the fuselage but there might have to be bumps over the cylinders as in the Griffon Spitfires.

Armament: I'm not really happy with planebuilders assumptions especially for large calibre weapons.

Ahh bore and stroke- makes much more sense
The bumps would do it, the dimensions are very close to the same, and since we're dealing with maximum width/breadth vs. an averaged area, I don't see why it wouldn't work.

As for weapons, they've bothered me for some time, but I have a hard enough time finding the discrete weights of the guns, I have no means of accounting for bracing weights.

IIRC, only 7.7mm machine guns were rigidily mounted, others having springs and dampers. Mounting on to engine block with a set of such. Then, the breach recoils and the entire gun recoils also.

This gives weapon weights. So does wikipedia. I don't have anything to go off to see whether planebuilder's assumptions are correct.

Heh I was looking there earlier in the hopes of getting a weight for the FN-Browning 13.2mm the Belgians used. It also lacks either Madsen cannon, and I have not been able to find them, so I just use the default.

The FN Browning shouldn't weigh much different than the M2 as it's just chambered for 13.2x96 instead.

Given the size of the Madsen cartridge (20mm or 23mm?) I'd guess a weapon weight of 50-60kg.