Double Pancake

[PR19_Kit]

Oh sure, you could, but it'd balance out the loads on the connecting shaft if you just shut down one half of each engine pair.

[jcf]

The cross shaft is going behind the front seat and in front of the rear instrument panel.

And as the production F5Us had turbine engines they didn't need such large oil tanks............... 

So the rear seat will be where the fuel tank is on the XF5U-1?

But as the engines are the dreaded T40s (hardly any aeroplane that used them was trouble free....) one half of each engine could be shut down in the cruise, a bit like a Gannet.

Living on the edge. 

Cutaway of the proposed Allison turbine version.

[PR19_Kit]

So the rear seat will be where the fuel tank is on the XF5U-1?

That's why it's going to have a couple of under wing tanks............

Living on the edge. 

Absolutely!

That cutaway is VERY interesting, I didn't actually know they planned to make a turboprop version, but it was a logical development. Which engine is that anyway? It doesn't look much like the T-38, which was half the dreaded T-40, but I can't find another Allison engine of the period.

It's interesting that the exhausts go right to the tail, and they seem to negate the use of the pitch control flap things that the piston engined version had.

[Weaver]

I'm tempted to suggest kippering the whole thing to make it wider, fitting longer cross-shafts, and then using a side-by-side two-seat cockpit.

Probably too late now though.

[rickshaw]

Why not simply fit a longer nose to accept another cockpit in front of the existing one?

[PR19_Kit]

As H said, it's too late now. I've already cut away large chunks of the 'fuselage' top decking, and it's looking quite good.

But then I would say that, wouldn't I? 

[jcf]

That cutaway is VERY interesting, I didn't actually know they planned to make a turboprop version, but it was a logical development. Which engine is that anyway? It doesn't look much like the T-38, which was half the dreaded T-40, but I can't find another Allison engine of the period.

Here's what Bill Pearce postulates:
"While it is not entirely clear which engine was selected, the engine depicted in a technical drawing closely
resembles the 2,200 hp (1,641 kW) General Electric T31 (TG-100) turboprop."

From his entry on the Flapjack:
https://oldmachinepress.com/2017/02/05/vought-xf5u-flying-flapjack/

[Weaver]

Why not simply fit a longer nose to accept another cockpit in front of the existing one?

I'm not sure, but I THINK the clearance between the two props is less than the width of the cockpit proper or at least so close to it that stretching it would be dangerous. They're about level with a point where the taper to the nose has already begun.



Image from here: https://forum.warthunder.com/index.php?/topic/185928-xf5u-flying-flapjack/

[kitnut617]

As H said, it's too late now. I've already cut away large chunks of the 'fuselage' top decking, and it's looking quite good.

But then I would say that, wouldn't I? 

But you could have the rear cockpit sitting on top of all the equipment that's there giving the instructor the best possible view of what's happening, sort of a precursor to the modern day trainer arrangement.

[PR19_Kit]

I've already had both those ideas in mind, and if I can get the sawn down Jaguar canopy to work, the rear seat will be higher.

I'm thinking of chopping off the tips of the props too, as most turboprops of the era, and all aircraft that flew with the T40 engine, had clipped prop blades. Unfortunately Mt. Zimmerman died some years back so I can't ask him if that would have negative effects on the vortex production. 

[jcf]

Clearer version of the Vought drawing of the XF5U-1, from the Vought Heritage site (click for full size).
More Vought product drawings here: http://www.vought.org/photo/html/pdown.html

[jcf]

I'm thinking of chopping off the tips of the props too, as most turboprops of the era, and all aircraft that flew with the T40 engine, had clipped prop blades. Unfortunately Mt. Zimmerman died some years back so I can't ask him if that would have negative effects on the vortex production. 

While they look like four-bladed props, in reality the flapping props are each a
pair of two-bladed teetering props mounted one in front of the other. The teetering action
is like that of a Bell helicopter rotor assembly. The design was required to avoid vibration
caused by unsymmetrical airflow and to resist heavy blade loads at high angles of attack.
Cutting off the tips may screw with that.

[kitnut617]

I've already had both those ideas in mind, and if I can get the sawn down Jaguar canopy to work, the rear seat will be higher.

What about a Hawk or Tucano canopy ---

[PR19_Kit]

Cutting off the tips may screw with that.

That's why I wanted to talk to Zimmerman. 

What about a Hawk or Tucano canopy ---

Maybe, but I had the Jag canopy from a crunched FROG kit already.

[PR19_Kit]

I've worked out how long the two seater cockpit needs to be, and chopped a much longer hole in the upper wingelage (wing-fuselage...) of the Pancake and I've added a rearwards extension onto the kit cockpit assembly. With a bit of fettling it looks as if it'll work quite well with the Jag canopy too.

The bang seats are a couple of F4 seats I just happened to have handy, they're about the right size and they look good. The RW pancake didn't have an ejection seat but I'm sure the USN would have insisted when it came to service use.

I've also completed one of the wildly complex prop assemblies too, but it's still in its Blu-Tak jig so pics of that will have to wait.