A Trilogy of Twinfires

[kitnut617]

Actually steelpillow, the Spitfire carried a stack of dead weight between frames 18 and 19 as ballast. The heaviest amount was around 250 lbs but it depended on which engine and prop combo was mounted on the front. The shortest Spitfire was 3 feet shorter than the longest, again depending which engine/prop combo and rudder hanging off the rudder hinge line which was governed by the length of the rudder chord. The actual fuselage assembly (frame 5 to frame 19) never changed it's length throughout the whole production run of Spitfires, Seafires, Spiteful and Seafang.  Frame 19 is the tail assembly mounting frame which is easily identified by the slanting panel line just before the tail.

[Wardukw]

The weight of a Merlin is 1320 lbs (600kgs)
The weight of a Griffon is 1980 lbs
(900kgs)
Thats a 300 kg difference in weight and 300 kgs on one side of any plane especially a light weight 2 engine plane would make it totally unflyable.
And this plane has 2 tails not one and making one tail larger just to compensate for that weight makes no sense at all..
Hell that 3 of me sitting on the wing .

[Pepsi Concorde]

Oh you nailed it mate..contra props will make this look like a real beast..ive gotta get some after market contra props..one build i have on mind would benefit from them to no end.

Making me think about contraprops for my twin spit now!

For my Twinfire build, I used two of Colin's (Freightdog) Seafire Griffin contra-props sets. Sorry I can't show you photos of it though, the 3rd party host I was using has gone t!ts up.

Looking into it

[kitnut617]

The weight of a Merlin is 1320 lbs (600kgs)
The weight of a Griffon is 1980 lbs
(900kgs)
Thats a 300 kg difference in weight and 300 kgs on one side of any plane especially a light weight 2 engine plane would make it totally unflyable.
And this plane has 2 tails not one and making one tail larger just to compensate for that weight makes no sense at all..
Hell that 3 of me sitting on the wing .

If you're referring to my build, it's not finished yet, the tail will be the same size on both sides. What isn't apparent in the photo, is I made the rear fuselage 1/2" longer, that's 3 feet in RW. So that plus 500 lb of ballast dead weight in the tail should do the job. Right ?

[Wardukw]

Well i think we went a little past your build matey 
The thing is shoving ballast into one corner of the plane to compensate for the engine would possibly cause a fault in the axis of the planes lay out..axis as in one croner to the other which could cause instability issues with the c of g .
With a single fuselage thats pretty easy to sort out..we do it with RC planes all the time and this does apply here ...theres guys out there will check the weight of every piece of balsa they use for the wings..balance has to be perfect from one side to the other .
Fact the centre of gravity on a plane is the most important thing..even on the biggest of aircraft to the smallest.
Thank god we like wiffy cause RW can be a massive pain in every aspect of the word.

[Tophe]

and 300 kgs on one side of any plane especially a light weight 2 engine plane would make it totally unflyable.

except in our whif world where everything's possible!

[Wardukw]

Hahaha Tophe 

[steelpillow]

Actually steelpillow, the Spitfire carried a stack of dead weight between frames 18 and 19 as ballast. The heaviest amount was around 250 lbs but it depended on which engine and prop combo was mounted on the front. The shortest Spitfire was 3 feet shorter than the longest, again depending which engine/prop combo and rudder hanging off the rudder hinge line which was governed by the length of the rudder chord. The actual fuselage assembly (frame 5 to frame 19) never changed it's length throughout the whole production run of Spitfires, Seafires, Spiteful and Seafang.  Frame 19 is the tail assembly mounting frame which is easily identified by the slanting panel line just before the tail.

No need for the "actually", dear boy. Spits varied wildly in the bits hung on in different places, as you point out, and the main fuselage was also strengthened in later marks; some were aerodynamically stable, others were not.

The weight of a Merlin is 1320 lbs (600kgs)
The weight of a Griffon is 1980 lbs
(900kgs)
Thats a 300 kg difference in weight and 300 kgs on one side of any plane especially a light weight 2 engine plane would make it totally unflyable.
And this plane has 2 tails not one and making one tail larger just to compensate for that weight makes no sense at all..
Hell that 3 of me sitting on the wing .

There is no such thing as "the" weight of an engine that came in many variants. Late-model Merlins weighed more than you suggest, early-model Griffons less. As I said (that phrase again), the difference was around 10-20% at that point. Note that the tail ballast cited by kitnut617 has a moment arm around 3 times greater. The 87.5 lb (5 standard ballast weights of 17.5 lb) carried by the Mk. IX was counterbalancing some 260 lb or so of two-stage supercharged Merlin 61. The 250 lb balancing the heaviest Griffons offset some 750 lb of engine weight, well able to compensate across that 10-20% range. Moreover, as I also said (ahem! Pay attention at the back, there!) the Griffon's extra weight meant that it never caught up the Merlin in the amount of power delivered for each pound.
Do the two halves of an aeroplane have to be identical in weight? Certainly not. Several successful types have had asymmetries built in for one reason or another. The dffference here could easily be trimmed out by the ailerons (that magnifying moment arm again). Another option would be to fit an extended tip to the Griffon-side wing and clip the Merlin side's (I like that!). But both of those would compromise manoeuvrability - either aileron range or the weak extended tip). Better would be to shift those ballast weights across and design the centre sections to accommodate the slight structural twist that creates. Here's the asymmetric-wingtips version:



But the only external passenger known to have flown on a Spit was clinging to the tail plane - which on a twin-tail can easily accommodate 3 of you. Have a nice flight, and don't let go without a parachute - any of you!   

[Wardukw]

You on the point Steel mate but what qould the point be to build such a cockeyed plane ..when  you build one you'd at least want to make it easy andnlike ya said mismatched parts make for a bad flight..lenghtened this..clipped this and ballast the hell out of it ..i would not want to fly it especially with blokes holding on to it 
The biggest annoyances would the differences in power..trying to get 2 engines of vastly different power ..without mods ..would be a nightmare..its the same in twin engined drag cars..yes you could shorten a prop here and regear this there such as the superchargers but man thats a lot of work for very if any benefits and dude..it would look so strange it would fit in here perfectly 
Im so tempted to build a Rc plane with all least issues and see how it would fly..i am thinking baddly 
One engine will scream and the other would be a little above idle just to match propeller rpm..i have a few choices of electric motors to play with and a couple of planes i can hack up..ive got 18 planes to play with so im good 
Oh i think a experiment is gonna be in the works Mr Pillow mate 

[steelpillow]

The biggest annoyances would the differences in power..trying to get 2 engines of vastly different power ..without mods ..would be a nightmare..its the same in twin engined drag cars..yes you could shorten a prop here and regear this there such as the superchargers but man thats a lot of work for very if any benefits

Sorry you do not seem to be taking it in. I'll try one more time:
The engines were OF SIMILAR POWER at this time and the MANUFACTURER'S OPTIONS INCLUDED SINGLE- AND TWO-STAGE SUPERCHARGERS. The props were MANUFACTURED TO MATCH THE ENGINE and would not have been modded or re-geared. No messin'!

what qould the point be to build such a cockeyed plane ..

..it would look so strange it would fit in here perfectly

You just answered your own question!  Did you like my sketch?

[Wardukw]

To make life simple stick to 2 of the same either Merlins or Griffons .
If i  ever build another twin engined boat ill do the exact same thing i did in the frist place..use 2 of the same of everything..same pistons..valve springs.cranks..etc..took nearly a week to get both of the props prefectly weighted and balanced..damn fast boat ..man i miss that thing.

[steelpillow]

On 17 August 1943, Wing Commander Clive "Killer" Caldwell of the Royal Australian Air Force in his Spitfire Mk V shot down a Mitsubishi Ki-46 "Dinah" reconnaissance plane as it headed out across the Timor Sea for home, mission accomplished.
What history does not record is that his machine was in fact a "Twinfire Mk VV" Pacific interceptor, cobbled together from two "written-off" airframes by deep repair depot ARD 14, based at Gorrie, far inland away from the action in the Northern Territory. Had he been in a standard Spit, he would not have had the range to catch it.
Even the identities of those two airframes have been carefully researched for this whiff; only one suitable one was available at 14 ARD, and the other had to be trucked in from a satellite repair depot. Note the clean appearance of the new centre sections, painted in the RAAF colours of the day (more visible in reality than in the photo), in contrast to the battle-weary original Spits in RAF standard shades. The spare cockpit space houses an auxiliary fuel tank.
Finished at last, here is Caldwell's "Wonky Wonder" as it was that morning, before he climbed in and took off to go Dinah hunting.







It is far and away the most complex, detailed and challenging model I have ever undertaken, in both kitbash and paint job.
In theory it is my warm-up to his sidekick Robert "Bobby" Gibbes' Sharkmouth Mk VIII, which he helped institute for the Mk VIIIs of 457 Squadron. A sharkmouth Twinfire, now that has to be something - as does applying the decals! But I recently dropped the half-painted beast on the floor and that has set it back weeks, probably months. Hey-ho.

[Tophe]

 

[NARSES2]

That's come out really well mate 

[perttime]

Looks credible!
There's more of the "middle wing" than I expected. No guns in it? There'd be a lot of space for fuel.