Twin-hull planes

tomo pauk · Mar 11, 2010

I'm great fan of radial engines, too - my favorite WW2 plane remains the P-47 The mud-fighter Spitfire, with 1700 HP Hercules would do just fine IMO. And same engine (with apropriate HP available for year of introducing) would do just fine in Defiant, Hurricane and Fulmar hulls.

As for re-engined B-17s, I like the concept of master-slave engines. The Do-217P used it, with one DB-605 acting as supercharger for two DB-603 engines - the plane was able to do beyond 700 km/h above 10 km altitude IIRC. So I'd propose the 4 x Allison on wings, and 5th in hull, acting as 'slave'. Of course, the MG turrets and posts would be deleted, and crew cut down to 4-5 members. The resulting plane would render the 90% of German AAA useles, since it would fly at 40kft (hopefully ). Same for Fw-190 Bf-109.

Please do share the pics/drawings.

tomo pauk · Mar 11, 2010

Twin Yak-1, hopefully Russkies would managed it in 1942
4 x 20mm, 2 x 1100 HP, perhaps 620-630 km/h - enough to battle Bf-109 in more equal terms.

tomo pauk · Mar 11, 2010

MiG-3 spin-off:
Armed recconaisance version, 2 x 20mm, camera(s), 2 x 1350 HP, just under 700 km/h, feasible in 1941 well beyond Bf-109F/G envelope (but not beyond Bf-109Z ).

Waynos · Mar 11, 2010

Real Hurricanes were armed with twin 40mm cannon so why not give yours three? The other two being outboard in the normal fashion.

Shortround6 · Mar 11, 2010

tomo pauk said:
As for re-engined B-17s, I like the concept of master-slave engines. The Do-217P used it, with one DB-605 acting as supercharger for two DB-603 engines - the plane was able to do beyond 700 km/h above 10 km altitude IIRC. So I'd propose the 4 x Allison on wings, and 5th in hull, acting as 'slave'. Of course, the MG turrets and posts would be deleted, and crew cut down to 4-5 members. The resulting plane would render the 90% of German AAA useles, since it would fly at 40kft (hopefully ). Same for Fw-190 Bf-109.

.

No reason to suppose any such performance. Look up the XB-38. A B-17 with four turbo-charged Allison engines. 1425 hp apiece to 25,000ft.
Changing the supercharger system to a master-slave set up isn't going to increase the basic HP of the engines. Considering the fact the the German set up decreased in HP as it went up from 3500hp total for take off to 3240Hp at 18,700ft to 2880hp at 45,000ft. the American system of maintaining take-off power to 25,000 ft doesn't look so bad. I would also note that the DO-217P carried NO internal bombs.

For a bit of a reality check on some of the performance figures I might suggest looking at the Savoia-Marchetti SM.92. 382mph with two DB 605s.

tomo pauk · Mar 11, 2010

Waynos said:
Real Hurricanes were armed with twin 40mm cannon so why not give yours three? The other two being outboard in the normal fashion.

Feasible, I don't doubt it

I was thinking more in a all-around attacker: 40mm for tank-busting, 20mm for small soft targets, outboard rockets for large soft targets. But any variation would do, I guess.

herman1rg · Mar 11, 2010

Lets see some twin bombers.

tomo pauk · Mar 11, 2010

Shortround6 said:
No reason to suppose any such performance. Look up the XB-38. A B-17 with four turbo-charged Allison engines. 1425 hp apiece to 25,000ft.
Changing the supercharger system to a master-slave set up isn't going to increase the basic HP of the engines. Considering the fact the the German set up decreased in HP as it went up from 3500hp total for take off to 3240Hp at 18,700ft to 2880hp at 45,000ft. the American system of maintaining take-off power to 25,000 ft doesn't look so bad. I would also note that the DO-217P carried NO internal bombs.

For a bit of a reality check on some of the performance figures I might suggest looking at the Savoia-Marchetti SM.92. 382mph with two DB 605s.

I have no hard proof that 'my' B-17 could do what I was claiming, but this is a what-if thread anyway

The turbo-charged Allisons (in real planes) used the exhaust gasses to turn their superchargers, while in my proposal their exhaust gases would be used as additional thrust. Since that effect increases with altitude, it negates the effect of HP drop per engine. In our 'P-47N vs. Ta-152' thread this was better explained than I can - also works as a reality check

Of course, the 'slave' engine would still use the turbo-charger.

While the German plane used bomb bay to house the power plant, the 'slave' engine for B-17 would be located just aft the aft spar. I'd provide the illustration ASAP

tomo pauk · Mar 11, 2010

herman1rg said:
Lets see some twin bombers.

Yep, some 3-engined, twin-hull Mosquito could've replaced RAF's night bombers with ease. Not that 'plain' one was bad either.

tomo pauk · Mar 11, 2010

Here 'tis, placing of 5th engine (original picture from our forum):

tomo pauk · Mar 11, 2010

Twin Ki-43 Hayabusa ('Oscar') with clipped wings for better speed:
4 x 12,7mm, 2 x 970 HP, 550 km/h, available prior Pearl Harbour;
2 x 20mm, 2 x 12,7mm, 2 x 1150 HP, just under 600 km/h, mid-war;
4 x 20mm, 2 x 1300 HP, 630 km/h, late war.

tomo pauk · Mar 11, 2010

Shortround6 said:
For a bit of a reality check on some of the performance figures I might suggest looking at the Savoia-Marchetti SM.92. 382mph with two DB 605s.

I've just checked out the data for SM.92- the plane was a real blooper. Eg. Fiat G.55 was faster with just one DB-605. But Italians had another plane that disappointed them similarly - Ba.88 - voted many times as worst of WW2 planes in our forum. Even some Ambrosini fighters with 750 HP were faster (but with less firepower, admitedly). I guess there are excellent designs, and there are bad ones

Shortround6 · Mar 11, 2010

tomo pauk said:
Here 'tis, placing of 5th engine (original picture from our forum):

It still doesn't make much sense. you are replacing 800-1000lbs of turbo superchargers with 1600-1800lb worth of 5th engine, radiator, oil cooler PLUS the weight of the central supercharger PLUS the weight of the ducting to get the air to the engines in the wings. You also have the cooling drag of the 5th engine. You would probably get some increase in performance but is it enough to make the project worth while?

Your proposed engine location is aft of the center of gravity and would require some shifting or removal of weight. deleting ball turret and waist guns and gunners would help but this is in the nature of balancing the plane and canceling weights rather than reducing weight for performance gain.

the French and Germans who used this system didn't have workable turbo-chargers.

Your additional thrust from exhaust gases might help cancel the fuel burn of the 5th engine to help keep the range of the aircraft but since the exhaust thrust also varies with the speed (better at higher speeds) bomber cruising speeds might not give you the boost that fighters get.

Shortround6 · Mar 11, 2010

tomo pauk said:
I've just checked out the data for SM.92- the plane was a real blooper. Eg. Fiat G.55 was faster with just one DB-605. But Italians had another plane that disappointed them similarly - Ba.88 - voted many times as worst of WW2 planes in our forum. Even some Ambrosini fighters with 750 HP were faster (but with less firepower, admitedly). I guess there are excellent designs, and there are bad ones

I am not sure how it is a "blooper"?

It is after all 30-40 mph faster than an BF 110 using the same engines and it is alsol faster than than a ME 210 using the same engines.

It is almost the same speed as a ME 410 using 1750hp DB 603s. With three 20mm cannon and 5 12.7 mm mgs it doesn't look like it sacrificed much armament to it either.

The 1200 mile range without drop tanks might have something to do with it also.

tomo pauk · Mar 11, 2010

Shortround6 said:
It still doesn't make much sense. you are replacing 800-1000lbs of turbo superchargers with 1600-1800lb worth of 5th engine, radiator, oil cooler PLUS the weight of the central supercharger PLUS the weight of the ducting to get the air to the engines in the wings. You also have the cooling drag of the 5th engine. You would probably get some increase in performance but is it enough to make the project worth while?

I'm also deleting the MGs (10-11 x 90 lbs = cca 1000 lbs), ammo (? lbs), 5-6 crew members their flak jackets (x 200 lbs per man = cca 1000 lbs), turrets their armor (??lbs) - perhaps 2500-3000 lbs saved on these accounts. The drag of cooling system is less then the drag of MG turrets, single MGs and MG openings.

Is my project worthwhile? Again, I can't prove it, but in my eyes it has merit

Your proposed engine location is aft of the center of gravity and would require some shifting or removal of weight. deleting ball turret and waist guns and gunners would help but this is in the nature of balancing the plane and canceling weights rather than reducing weight for performance gain.

Then I'd say we disagree
Russians were known for cutting the weight to gain performance, and NAA also put P-51 to the treatment to have P-51H.

the French and Germans who used this system didn't have workable turbo-chargers.

Despite employing turbo-chargers, B-17s and B-24s could not owerflew the 109/190 combo and heavy AAA, so I propose something that could

Your additional thrust from exhaust gases might help cancel the fuel burn of the 5th engine to help keep the range of the aircraft but since the exhaust thrust also varies with the speed (better at higher speeds) bomber cruising speeds might not give you the boost that fighters get.

Do-217 had the boost, and flew as high as 53kft (data from Wiki), and it was bomber. So I'd guess again that concept had merit

tomo pauk · Mar 11, 2010

Shortround6 said:
I am not sure how it is a "blooper"?

It is after all 30-40 mph faster than an BF 110 using the same engines and it is alsol faster than than a ME 210 using the same engines.

It is almost the same speed as a ME 410 using 1750hp DB 603s. With three 20mm cannon and 5 12.7 mm mgs it doesn't look like it sacrificed much armament to it either.

The 1200 mile range without drop tanks might have something to do with it also.

If the plane really used 2 x DB 605 (x 1450 HP) engines and managed 610 km/h (with really low-drag airframe), it was way slower then P-38J with 2 x Allison ( x 1475 HP IIRC) that had bigger (=draggier) central nacelle.

Bf-110 was one of slowest twin-engined fighters per HP installed, so there is no much worth comparing it with other designs.

It would be a significiant boost for Italian air force, but I guess they prefered G.55 and Re 2005.

Shortround6 · Mar 11, 2010

tomo pauk said:
I'm also deleting the MGs (10-11 x 90 lbs = cca 1000 lbs), ammo (? lbs), 5-6 crew members their flak jackets (x 200 lbs per man = cca 1000 lbs), turrets their armor (??lbs) - perhaps 2500-3000 lbs saved on these accounts. The drag of cooling system is less then the drag of MG turrets, single MGs and MG openings.

Is my project worthwhile? Again, I can't prove it, but in my eyes it has merit

Al true but if you ripped that much weight out of the XB-38 and faired over the gun/turret openings would would also gain performance.

tomo pauk said:
Then I'd say we disagree
Russians were known for cutting the weight to gain performance, and NAA also put P-51 to the treatment to have P-51H.

The Russians ditched weight because their engines couldn't make any more power.
Adding over a ton of weight to the radio compartment doesn't just call for weight reduction, it calls for weight reduction from the radio compartment aft or weight ADDITION from the bomb bay forward. other wise the CG would be too far from the center of lift and make the plane dangerous to fly. The Streamlining is sort of a side bonus.

tomo pauk said:
Despite employing turbo-chargers, B-17s and B-24s could not owerflew the 109/190 combo and heavy AAA, so I propose something that could

the Higher the bombers flew the worse the accuracy of bombing was. stripping out a few thousand pounds of weight from the B-17/XP-38 might have given it a few thousand more feet of ceiling and accomplished much of your goal with less trouble. Standard B-17s were credited with about 7,000ft more ceiling than B-24s and their turbo charged cyclone engines could cruise at 35,000ft putting out 750HP for as long as the fuel would last. The turbo Allisons should do a bit better.

tomo pauk said:
Do-217 had the boost, and flew as high as 53kft (data from Wiki), and it was bomber. So I'd guess again that concept had merit

As a "bomber" it could carry a pair of 1102lb bombs on under wing racks. The 3 Pre-production machines carried cameras and according to Green (which maybe out dated) the 53,000 ceiling was at 29.250lbs. At 30,600lbs the ceiling dropped to 50,800ft. Normal loaded weight was 31,600ft and max was 35,200lbs.

Shortround6 · Mar 11, 2010

tomo pauk said:
If the plane really used 2 x DB 605 (x 1450 HP) engines and managed 610 km/h (with really low-drag airframe), it was way slower then P-38J with 2 x Allison ( x 1475 HP IIRC) that had bigger (=draggier) central nacelle.

But the P-38 used a wing only 3/4 the size. It also had less drag than a F6F Hellcat and a little less than twice the Drag of a P-39.

to get true comparisons you have to compare planes at the same hight AND know what power the engines were giving at the hight in question.

tomo pauk said:
It would be a significiant boost for Italian air force, but I guess they prefered G.55 and Re 2005.

Nobody intended the "twin" fighters for the air superiority role. They were intended as long range escort fighters or heavy bomber destroyers. They won't roll as well as a single fuselage machine so initiating turns or reversing turns will be slower, They have higher wing loadings than the parent singles and so have larger turning circles.

Speeds are suspect also: exactly which engines were used for the performance that is quoted on various web sites?

P-82s had (the few that were built with Merlins) could operate with water injection as could the Allisons that powered most of the production. These engines were good for 2000-2200hp at certain altitudes, the question is what HP the engines were putting out at the altitudes the speeds are quoted for.

tomo pauk · Mar 11, 2010

Hi,

Re. cleaned-up lighter XB-38 vs master-slave version: I agree that 'your' version would work nicely - yet 'my' version would be notably faster since the 4 wing engines would deliver both power to prop AND considerable residual thrust, while 'your' version would not deliver the residual thrust. It would weight 24-25 tons empty (if we agree that it would be 1 ton heavier then stripped XB-38 ) - cca 4% more that is.
Liberator with master-slave...hmm... maybe even more useful

Re. twin fighter for Italians: they SM.92 we're talking about offered nothing more then G-55 or Re 2005 could (aside of range - not an issue here) despite having twice the number of engines. No wonder they didn't produce it. Heavy fighters of other countries provided either greater speed , or firepower, or both (plus range), when compared with single-engined planes sharing the same engine.

Forgot the CG issue, after installing the engine just behind the aft spar: we do delete the 4 x HMG (two hip MGs and talil MGs) ammo ( 4 x 120 lbs), 3 crew members their gear (3 x 200 lbs), armor for tail turret (? lbs). That equals 1100 lbs + armor of tail turret, and these pieces of gear are much farther away from CG then heavier 5th engione associate equipment. CG issue solved

tomo pauk · Mar 13, 2010

Anyway, here is twin Defiant night fighter:
6 x 0.303 in wing (later 4 x 20mm), 4 x 0.303 in turret (to double as 'Schreage musik'), 3 crew members, radiators relocated to central win, engines from 1030 HP (well above 500 km/h) to 1450 (around 600 km/h). So beating any contemporary NF Germans had in numbers.

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