The RAF's sole Savoia Marchetti SM-77 - Egypt, 1942

ericr · November 05, 2020, 12:16:18 AM

now that is wings ...

PR19_Kit · November 05, 2020, 06:09:09 AM

That's why I'm building it.

The RW S.66 did have much longer wings than the S.55X, but the S.77 takes them to new 'lengths'.............

PR19_Kit · November 05, 2020, 07:23:33 AM

While building the first S77 engine pod, two Merlins back to back, I found an interesting facet on Lancaster engines. Not only are the inboard engine nacelles longer (they would be, they've got the main landing gear in them....) but they're wider too. The sawn down outer nacelle fits neatly inside the inboard one, making life a lot easier as there's more gluing area to deal with.

Of course it means there'll be more PSR to deal with as well, but that's life in WhiffWorld......

[Note to self] I MUST remember to put the rear engine exhausts on backwards!

PR19_Kit · November 06, 2020, 06:05:49 AM

The original plan for the S77's armament was for it to carry a couple of torpedoes under the centre section and for some gun turrets to be added where they fitted, but when I'd taken in how much wing area it would have I decided to increase its lethality by adding some bomb and depth charge racks.

So I carved a hefty hatch into the side of the hulls to make room for a couple of slide-out bomb racks like a Sunderland. Here's the starboard one with a chunk of the Lanc's bomb bay acting as the slide-out rack, but with only one bomb in position so I could get the hatch size correct.

Even more plastic engineering took place to ensure the wings stayed at the correct dihedral angle as I was dubious that the Lanc's wing braces would work without some positive location inside the centre section. Accordingly I measured the gap between the top of the wing brace and the underside of the roof of the centre section and made up some packing pieces to fill the gap. NOT an easy task as it meant peering in one side of the centre section at the wing that was in position on the other side, and taking a wild guess.

Luckily I guessed right, and the gap turned out to be 4mm. Here's the wing in position with the carefully shaped hole cut in the centre section to match the wing brace.

And here's the packing piece glued inside the centre section. Don't ask how I got it in there.............

PR19_Kit · November 06, 2020, 06:57:29 AM

The various bits and pieces of this build were getting out of hand, and I kept on losing some of them so I got a biggish box to put all the bits I've worked on so far in the one place.

I know I prefer the 'engineering' part of such a build, but this lot's starting to look RIDICULOUS!

So many small parts and a hefty number of big ones too, EVERYthing in there's going to have some part to play in eventual S77, maybe not the whole Lanc fuselage, but chunks of it anyway.

NARSES2 · November 06, 2020, 07:08:41 AM

This is going to be amazing Kit

Must admit I use boxes to separate various sub-assemblies on my builds and then I'll use milk container (they're not bottles anymore) tops to keep the small parts in. Comes in useful especially when painting.

PR19_Kit · November 09, 2020, 03:43:06 AM

Using Lancaster wings for the S77 gave me one BIG problem. Because the main wheels retract into the inner engine nacelles, I've ended up with two HUGE holes in the underside of each wing. So I added some support plates around the edges of the holes and plated them in with handy styrene I had that was just the right thickness. Then it was a few PSR sessions, and at last it's looking smooth again.

Here's the before and after construction pics of the holes.

PR19_Kit · November 10, 2020, 03:01:42 PM

I don't think I've built such a complicated model in ages, lots of small parts, all of which are meant to come together to make the whole thing, and they already do in my head.....

But now they're starting to come together, both wing halves are now glued onto the centre section, and it's looking to be quite a large model eventually.

Because the thickness of the S55 centre section is quite bit more than the Lancaster outer wings, I've added some stepped padding at the roots, and you can see that's already glued in place onto the port wing.

What you can't see is the ASV radome that's scabbed onto the underside of the starboard wing.

It looks a bit like a Sunderland Mk 5, but the radome is the Lanc's H2S dome that's been filed down to fit the wing curvature.

In the process of all this wing work I managed to knock all THREE seats out of the cockpit.

I've found the Captain's and First Officer's seats, but the Flight Engineer's has vanished. I've got some spares knocking around somewhere though.

The first twinned engine nacalle is making progress too, lots of PSR and bits of Lanc fuselage top grafted in to fill in the gaps. The rear engine will need a cooling air intake and that's being donated by one of the spare fuselages that come with the AZ MB6s that I've got.

No, I haven't figured out how to mount the nacalle on a pylon with the intake underneath it, but I'm working on it......

zenrat · November 11, 2020, 02:10:04 AM

I think you are missing a trick Kit.
The inner section of the Lanc wing - from the outside edge of the inner nacelles to the root - is constant chord and as you are cannibalising two aircraft you could extend the span by adding the inner section of the spare set of wings...

PR19_Kit · November 11, 2020, 04:48:09 AM

I actually thought of doing that too, but it looked WELL OTT, so I stuck with one wing set per side.

Gondor · November 11, 2020, 11:17:18 AM

Quote from: zenrat on November 11, 2020, 02:10:04 AM
I think you are missing a trick Kit.
The inner section of the Lanc wing - from the outside edge of the inner nacelles to the root - is constant chord and as you are cannibalising two aircraft you could extend the span by adding the inner section of the spare set of wings...

Tha's what I am doing with My Lancaster XL

Gondor

PR19_Kit · November 11, 2020, 12:48:12 PM

You may recall I was having to think about how to get the engine cooling air into and out of the paired, back-to-back Merlins a while ago. Last night I had a brain wave at around 1 am, as you do

and this is what I came up with.

The outline of the paired Merlins is in black of course, and the pylon plan is in red (thanks for the idea Fred.

) Now the cooling air exhaust from the front engine will go down into the pylon and will be directed out from a port on the INBOARD side of the pylon itself (shown in green) The intake cooling air for the rear engine will be sucked in from a duct (an AZ MB6 fuselage cooling duct turned on its side) from the OUTBOARD side of the pylon, into the rear of the pylon and from there up into the radiator (shown in blue)

So what do you think of that do you see any problems?

Gondor · November 11, 2020, 10:18:11 PM

You could just mount the rear engines radiator on the top of the engine and back to front. Don't forget the make sure that the propellor for the rear engine is faceing the right way.

Gondor

zenrat · November 12, 2020, 02:13:03 AM

Quote from: PR19_Kit on November 11, 2020, 04:48:09 AM

I actually thought of doing that too, but it looked WELL OTT, so I stuck with one wing set per side.

shock! horror! gasp!

PR19_Kit · November 12, 2020, 03:51:41 AM

Quote from: Gondor on November 11, 2020, 10:18:11 PM

You could just mount the rear engines radiator on the top of the engine and back to front. Don't forget the make sure that the propellor for the rear engine is faceing the right way.

I could, but then it would lose the inherent 'Merlinness' of the engines. The idea was to keep the original intakes and radiators but working in reverse.

The prop issue still has to be sorted, and the engine would have to run in reverse if I kept the prop with the same pitch angles.