Crazy XB-15 WHIF

[KJ_Lesnick]

Originally the XB-15 was to use the V-1710 but the engine wasn't ready yet.  Though it would have produced somewhat more horsepower and less drag, I'm not sure it would have been terribly fast.

However imagine an XB-15 with 6 x V-1710's  
                                                           
Admittedly it would require a stronger wing and structure to carry an extra two engines (V-1710's were also a bit heavier than the R-1830), and the extra fuel to feed them, but as I see it 4 x R-2600's weighed more than the V-1710's and even with the extra weight, it would potentially perform pretty good especially if supercharging or turbocharging were incorporated into the design: I'm thinking the extra engines, and fuel requirements would bump the OEW to about 48,000 pounds (maybe 50,000), with a fuel fraction around 32-35% the plane could cruise faster and the 12,000 pound bomb-load.  Weight would probably be (assuming a 48,000 OEW) 91,500 at MTOGW and that would give a power-loading that's pretty close to the B-17 providing a supercharged V-1710 (and possibly equal if turbos were added). 

Admittedly it's wings might very well have had a greater T/C ratio (I know they were physically thicker, but I don't know what the ratios were), I know it's wing loading was lighter even with the extra weight I described added (though it's aspect ratio was slightly lower) and this would naturally result in potentially less performance (admittedly the inlines produce lower-drag) so I'd assume it would be a somewhat slower, but I'm not sure.

What do you guys think?

[wuzak]

The XB-15 used R-1830s. So 4 x V-1710s would be heavier, let alone 6.

[KJ_Lesnick]

wuzak

You did read my first post right?  I already explained that...

[wagnersm]

Perhaps rather than the Allisons, use  1,600 horsepower (1,200 kW) Twin Cyclones as was used on the Boeing B314A Clippers.

The B314 and B314A used the same wing platform as the XB15.  It would be a natural fit.

Steve

[wuzak]

wuzak

You did read my first post right?  I already explained that...

Clearly I didn't!

I got it into my head for some reason that you thought the XB-15 had R-2600s....

[KJ_Lesnick]

WagnerSM

Perhaps rather than the Allisons, use  1,600 horsepower (1,200 kW) Twin Cyclones as was used on the Boeing B314A Clippers.

The twin-cyclone wasn't used in any aircraft before 1938 it would appear (there's one French design which flew in 1937, however it used that engine later) and the B-15 flew in 1937.


Wuzak

Clearly I didn't!

You must have read the comment I made about the R-2600 and jumped from there.  It's not a big deal.

[jcf]

Twin Cyclone = R-2600 Cyclone 14

Wright engine summary:
http://www.enginehistory.org/Wright/CWafter1930_2.pdf

[KJ_Lesnick]

Twin Cyclone = R-2600 Cyclone 14

Wright engine summary:
http://www.enginehistory.org/Wright/CWafter1930_2.pdf

Now this is a nice asset... so it was in production from May 1937?

[Logan Hartke]

I know it's boring, but I've looked at the growth potential and production possibilities for the XB-15 myself, and I likewise concluded that the R-2600 and eventually R-2800 were the best options for the aircraft.  Long-term, even the R-3350 may work, but going with six engines or liquid-cooled engines would just complicate things.  I'm sure they'd have tested it with V-3420s, but I'm also sure that nothing would have come of it.

That would have been enough power to get the job done.  It wasn't the most aerodynamic airframe, but it really wasn't too bad, either.

Cheers,

Logan

[KJ_Lesnick]

Logan Hartke

I know it's boring, but I've looked at the growth potential and production possibilities for the XB-15 myself, and I likewise concluded that the R-2600 and eventually R-2800 were the best options for the aircraft.

What lead you to believe this?

going with six engines or liquid-cooled engines would just complicate things.

I'm just basing it on the fact that the plane was designed back in 1934 at which point the R-2600 wasn't in service (it was first run in 1935). 

At the time they wanted to use the V-1710 so if the engine was available (which largely had to do with a poor demand for them resulting in a slow development). 

The problem is even if they were able to use the V-1710, the plane would have been too slow (admittedly the specs they were pushing for only called for 200mph), so I figure adding 2 more engines would fix the problem. 

I figure the R-2600's could have been fitted by the time the plane made it's first flight as it was in production starting in May 1937 and the plane didn't fly until later in the year: However I want to point out the Boeing 314 could only do around 210 max which used R-2600's.  I suppose it might very well have been acceptable for the time however.

[Logan Hartke]

Not all V-1710s were created equal.  In fact, four 1938 R-2600s of 1,600 hp (such as those on the Boeing 314) produced as much power as six V-1710s of the same period (such as those fitted to the YFM Airacuda).  Add to that the considerable weight increase of two additional engines and the associated mounts, fuel tanks (they were thirstier engines), coolant tanks and coolant (unnecessary on radials), and wing structure to support the added weight and you're still much better off with twin-row radials.

The Boeing 314 is not a great comparison for speed (and speed isn't everything, anyway) since it had so much more drag.  Even so, the Boeing 314 had a higher cruising speed than the B-17s of the same period.  Later, you could upgrade those engines to R-2800s or R-3350s for even greater performance.

Again, I'm just pointing out what is most practical.

Cheers,

Logan

[KJ_Lesnick]

Not all V-1710s were created equal.  In fact, four 1938 R-2600s of 1,600 hp (such as those on the Boeing 314) produced as much power as six V-1710s of the same period (such as those fitted to the YFM Airacuda).

That's a good point.  And even if turbosuperchargers would add power, so to would they on a radial

The Boeing 314 is not a great comparison for speed (and speed isn't everything, anyway) since it had so much more drag.

I assume you mean the boat-hull, sponsons, and three tails, because the 314 had no turrets...

Even so, the Boeing 314 had a higher cruising speed than the B-17s of the same period.  Later, you could upgrade those engines to R-2800s or R-3350s for even greater performance.

Nah, I'd much rather go with a better design like a B-29

[wagnersm]

I know it's boring, but I've looked at the growth potential and production possibilities for the XB-15 myself, and I likewise concluded that the R-2600 and eventually R-2800 were the best options for the aircraft.  Long-term, even the R-3350 may work, but going with six engines or liquid-cooled engines would just complicate things.  I'm sure they'd have tested it with V-3420s, but I'm also sure that nothing would have come of it.

That would have been enough power to get the job done.  It wasn't the most aerodynamic airframe, but it really wasn't too bad, either.

Cheers,

Logan

I would expect that the XB15 would have grown the same way was the B17 did. 

The aircraft have a family resemblance.

Steve

[KJ_Lesnick]

Why didn't they put a tail-turret on the back of the B-15 and B-17's from the outset?