Welkin Mk III

[PR19_Kit]

But now of course Kit you are just going to have to build it, maybe standard or the ultra high altitude version with even longer wings?

You read my mind Jim............... 

After writing this in the 'Holey Grail Kit' thread, my Welkin vacform has been bugging me. So this morning I shook the bits out of the bag and examined them with a view to building it. Naturally there's NO chance that it'll be built OOB, and it OBVIOUSLY  needs longer wings so I figured the so far ignored Welkin Mk III would be a suitable project.

The Mk III was introduced into squadron service after the MK Is were found lacking in catching the high flying Me 364s used by the Luftwaffe Kampfgruppen during the second half of 1944, and were successfull in bringing that part of the German bombing campaign to an end. Having been re-engined with Griffons, the Welkin Mk IIIs were able to climb much faster than the Mk 1s and could be waiting at altitude as the 364s approached the UK.

This being so, I need to swap the Merlins in the kit for some Griffons, and the question is, which Griffons? The ones I have to hand are those from the AZ Martin Baker MB5 kit or the Airfix Spitfire PR19, and I've drawn up the two options below.

Which one does the committee think looks best on the Welkin?

They'll use the appropriate props, contra-prop 3 bladers on the MB5 installation and a big 5 blader on the PRXIX setup.

[Old Wombat]

I prefer the look of the PR.19 engine cowling but I think the MB.5 cowling looks more appropriate on the Welkin.


Having said that: Which type of propeller is better at altitude, 5-blade single-prop or 3-blade contra-props?

[kitnut617]

Watching this one Kit.

Which one does the committee think looks best on the Welkin?

They'll use the appropriate props, contra-prop 3 bladers on the MB5 installation and a big 5 blader on the PRXIX setup.

Personally I think you need the Firefly Mk.IV cowling    

Mind you the problem with the Welkin was the wing, I've read that they couldn't run the Merlins at full power because the wing would high-speed stall. So it didn't matter how much more powerful the engines were, it could only fly so fast anyway.  Westland had a solution for it, they were going to increase the chord length by 20% but by then the Air Ministry had lost interest in it and nothing was done.

Some time ago I got hold of a couple of the CMK resin Welkins with the plan to add this 20% into one of them. Evan (elmayerle) had said the best place to add it would be either side of the main spar, so that's how I'm going to approach it.

[PR19_Kit]

Personally I think you need the Firefly Mk.IV cowling    

Mind you the problem with the Welkin was the wing, I've read that they couldn't run the Merlins at full power because the wing would high-speed stall. So it didn't matter how much more powerful the engines were, it could only fly so fast anyway.  Westland had a solution for it, they were going to increase the chord length by 20% but by then the Air Ministry had lost interest in it and nothing was done.

Some time ago I got hold of a couple of the CMK resin Welkins with the plan to add this 20% into one of them. Evan (elmayerle) had said the best place to add it would be either side of the main spar, so that's how I'm going to approach it.

I KNEW you'd mention the wing business Robert  and I thought of doing the broad chord version too, but it'd be extremely difficult with a vacform wing. I have some ideas about doing it, and I'll see how it works when it comes to cutting plastic.

[kitnut617]

Personally I think you need the Firefly Mk.IV cowling    

Mind you the problem with the Welkin was the wing, I've read that they couldn't run the Merlins at full power because the wing would high-speed stall. So it didn't matter how much more powerful the engines were, it could only fly so fast anyway.  Westland had a solution for it, they were going to increase the chord length by 20% but by then the Air Ministry had lost interest in it and nothing was done.

Some time ago I got hold of a couple of the CMK resin Welkins with the plan to add this 20% into one of them. Evan (elmayerle) had said the best place to add it would be either side of the main spar, so that's how I'm going to approach it.

I KNEW you'd mention the wing business Robert  and I thought of doing the broad chord version too, but it'd be extremely difficult with a vacform wing. I have some ideas about doing it, and I'll see how it works when it comes to cutting plastic.

The wing wouldn't be any thicker than it is, just the chord would've been lengthened.  IIRC, I worked it out to be about 1/2"

[NARSES2]

I prefer the look of the IIIb

I've built the CMR kit and it's a nice build Robert. Still got another one in the stash and the 2 seater 

[kitnut617]

Got the two-seater too Chris, I prefer it to the other one too.

[PR19_Kit]

I'm getting fed up with this................ 

Both my last post and this one have vanished just as I was reaching the end. It doesn't happen on other sites, just on here!!!!! And yes, I know all about writing it off-line and then copying and pasting, but I shouldn't have to!

I've drawn up the Welkin III with the 20& increased chord, and I make somewhat less than 0.5 ". Using the plan I have I make it around 9 mm at the root. Naturally I've had to increase the span a tad too...... 

I've drawn it with the MB5 cowling as using the Spit cowling will be a lot more difficult. The engine bulkhead of the PRXIX is not only at an angle but it sits well back behind the wing leading edge, whereas the MB5 cowling is well forward of its LE.

[kitnut617]

Now that looks good Kit. The MB5 cowling probably fits better because it has the same width as a Tempest fuselage, the Spitfire was quite a bit narrower.

I was trying to remember what I had worked the chord increase was, but it could have been 3/8".  Could you do that top view again without the wing span increase, I'd like to see what it looks like please.

[PR19_Kit]

OK, give me an hour or so.

We retired folks don't have much to do really. 

[kitnut617]

OK, give me an hour or so.

We retired folks don't have much to do really. 

[Rheged]

OK, give me an hour or so.

We retired folks don't have much to do really. 

Really??  Sounds of hollow laughter from further up the Wye valley.

[Tophe]

What about the twin-boom version?

[PR19_Kit]

Here you go Robert.

It looks quite 'ordinary' with that wing, don't you think, huge though it is?

[PR19_Kit]

What about the twin-boom version?

I can't do a twin boom version Tophe, I've only got one Welkin kit.