Twin Engine Thunderbolt in 1/72nd Scale

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T Bolt

Colonel
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4,485
Mar 24, 2010
Chicago, Illinois
Well I'm at it again, cutting up two perfectly good kits, this time to make something strictly out of my imagination. Several years ago I made up a couple of twin P-40's, one in 1/72nd​ and one in 1/48th​ scale based on a widely circulated photo of what appears to be a full scale mockup of a P-40, but for which there was absolutely no information on.

That build thread can be found here: P-40 Twin

Near the end of that thread found here: I posted several 3 way drawings that I had modified from single engine fighters as twins like the P-40 and there was a lot of discussion about it that can be found here: P-40 Twin

I have an Academy 1/72nd scale P-47 Razorback and a Revell P-47M in my stash and have recently acquired a bubble Academy so I decided its time to give it a try as I will be cutting up all 3 to make this work. I also have some bits and pieces from another Academy razorback and Revell P-47M that were used for conversions into a XP-72 and XP-47J

This one is going to me a lot harder than the P-40. I will be lengthening the wingspan by about a fuselage width, and the nacelles are going to prove to be very difficult. Looks like I will be spending some time sorting through all my spare parts boxes.

Below is the 3 view drawing I worked up. This one is not going to be finished overnight.

 
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Work begins

I began my cutting up the Academy bubble top kit for one of the nacelles, using a scriber to cut out the wing roots and cutting slots for the wing to pass through higher up. So far, so good but still a whole lot of work to form the taper at the rear of the nacelle. The same thing will be done with the razorback kit for the left wing. This is just a test fit, the wing still needs to be lengthened.

 
Ivan1GFP said:
Very interesting concept. There are a couple things that I can't quite figure out from your drawings:
Where are the turbochargers?
How does the landing gear fold up into the wing root?

- Ivan.
Click to expand...
The tubros are buried in the nacelles exhausting through the rear of each naecell.
The landing gear folds into the same well in the wing root with the gear leg mounted on the wing spar in the nacell. The portion of the gear cover on the lower wing will be mounted on the gear leg while the portion covering the slot in the naecell will be hinged shell like.
 
Nice fantasy, but in order to get any performance gains, they'd invariably lengthen wings, and all that bulky fuselage is now wasted space, drag and weight.
Could really slim down nacelles also ... compare with R2800 twins, both B-26s and F7F.
Bad place for needed fuel ... better place would be wings.
Would lose a lot of turbocharger benefit w/o long run for gas expansion.
And why not tri-gear for obvious reasons?
Coulda bashed a P-47 and a F7F ... but would have wound up with a F7F with Republic wings and tail!
 

To some extent, I agree with you and for some I do not.
I believe it would have made more sense to keep the wing with the root starting at the nacelle.
This would allow the landing gear length to be maintained, and armament to remain in the wings.
The nose would be a great place to put a RADAR system.
The depth of fuselage and nacelles even with turbos would not need to be as deep because the ducting for exhaust and pressurized air would not need to go around a cockpit.
This is where I disagree with you. There isn't really a benefit for long runs of ducting for turbochargers. The long run of ducting allows exhaust gas to cool and lose energy needed to run the turbines. Note that the various US bombers had turbos very near the actual engine.
The original location for fuel tanks was a pretty good one. There is a lot of volume. Obviously more is needed, so without the landing gear in the wing center section, there is probably room for a good size fuel tank on each side in the spirit of the P-47N along with sneaking in a couple 20 mm cannon between the propeller arc and fuselage on each side. The nice part of all this is that all the disposable loads would remain at the aircraft CoG and the wing center section would be available for ordnance or external fuel.
The problem with these ideas is that a lot of the visual connection with the Thunderbolt would be lost.

- Ivan.
 
Just a few words ... where in the world will you find enough room to hold the enormous fuel tanks that it would take to make this aircraft (as cool as it is!) be of more use than a short-range home-defense interceptor? For any long-range work, it would need to carry a total of 700 or so gallons of AV gas ... that's > 2 TONS of fuel - and that's a low number if you ask me, for two gas-guzzling R2800s...and where would you put the gas?

SURE - this proposed aircraft would NOT have a GE turbosupercharger system in the rear fuselage, and that'd make room for a lot of internal fuel tanks, but what would you do to somehow get the weights and balance numbers to where the CG for the aircraft to be ANYWHERE near where it needed to be for the plane to fly straight and level?
 

The ability to carry sufficient fuel is really the least of your problems with this twin Thunderbolt.
The mid / late production D-25 through M Thunderbolts had a 100 Gallon and a 270 Gallon internal fuel tank.
The removal of the engine from the fuselage clears up a LOT of space in the belly that was used for ducting that can be used for an additional fuel tank. The wing center sections between fuselage and nacelles can be used for fairly large fuel tanks similar to the P-47N.
Now that there is no engine in the fuselage, there is room in what was the engine accessory area for a very large fuel tank and perhaps one behind the cockpit to balance it. As with the original Thunderbolt, there is space for drop tanks under the wings outboard of the nacelles in this design or if the LG is moved to the nacelle or outboard, there would be room to hang some drop tanks on the wing center section.

The problem as I see it is that there really isn't sufficient wing area. The take-off performance of the original Thunderbolts was never all that good and now we have an aircraft that weighs a LOT more but without any more wing area and with a lot less flap area.

- Ivan.
 
Ivan1GFP said:
The problem as I see it is that there really isn't sufficient wing area. The take-off performance of the original Thunderbolts was never all that good and now we have an aircraft that weighs a LOT more
Click to expand...
The original Jug beat the air into submition.
A twin Jug would have twice the power with a nominal amount of weight gain to improve on that.
 
GrauGeist said:
The original Jug beat the air into submition.
A twin Jug would have twice the power with a nominal amount of weight gain to improve on that.
Click to expand...

The original Thunderbolts didn't really have any more power at sea level than any other R-2800 powered fighter. They just were able to maintain that sea level power to a much greater altitude. In order to take advantage of that extra engine power at altitude, they really had too much propeller at low altitude. That and the fact that the Thunderbolt was a bit over built for strength meant that it was trying to get a lot of weight moving with a propeller that was lugging a bit. Check the propeller power coefficient and you will see what I mean. The power coefficient at altitude is fairly optimal though which is where the plane was intended to perform best.
Keeping the same wingspan and area but adding a couple of nacelles effectively reduces the lifting surface and definitely reduces the flap area. The weight gain of an extra engine and induction system and double the fuel is fairly significant. Basically you will have an aircraft weighing about twice as much because all the parts not duplicated are the lightest structures of the airframe.
 
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