Monday 12 September 2011

'Building the Beast' - My Tigger Models 1/32nd Scale Short Sunderland Mk1 build - Part 2

In the first post we left 'the beast' on the work bench having just been cut-out. Now, the work begins to make something of the two hull halves.........

Whilst I was sitting there just staring at the sheer bulk of 'the beast' my eye was drawn to the wing root stubs sticking out from each Port and Starboard hull half. I was pleased when I first saw the kit parts that the molding included for each wing root stub as it meant that a potential major joint had been eliminated and with it the chances of a crack appearing at a later date due to the stresses of the wing-to-hull join being right on the hull itself. Doing it this way meant that at least I had a decent chance to stick both wings on these stubs without having to resort to a huge amount of fairing-in of the wings to the hull at this juncture. The wing fairing would be a major job otherwise. However, that was not what I was looking at; what I noticed just sitting there was that the port wing root  fairing was sitting higher up the hull than the starboard!
"OMG" I thought....! That can't be right. But, unfortunately, it was. The fairing on the port side is a good two or three millimetre higher than the other and is only really noticeable from a head-on viewpoint. It is not noticeable at all from the side and I think that is due entirely to the sheer bulk (again) of the whole thing up close. Looking at a 1/72 scale kit part in-front of you is totally different than looking at this one.

Ok, so it's part of the mold and I will have to deal with it as the build goes on, I said to myself, whilst adding the point to the kit-build list that I had made up. I was already thinking of a way to sort the problem out. However, prospective customers and builders please note that it should be entirely practicable to achieve a solution for this without going to the lengths of major surgery. More on this subject later in the build.

However, having got over this problem, another one loomed up almost straight away! One of the things that any vac-form kit builder has to have in his portfolio is (1)  patience and (2) method aforethought.
The canopy transparency is a large fine molding and looks quite accurate
Patience because this isn't a 'shake n' bake' kit - a kit that is going to 'fall together' out of the box, indeed by its very nature no vac-form kit ever is, or will be. Every time I purchase and start a vac-form I go into a sort of 'building mode' that is best described as 'different to injection molded kit build'. I can't explain it any better than that; it's simply knowing that the kit in-hand is going to  bite you at some point and you have to determine when, to avoid it. That requires of the builder a large degree of patience as this kit is not going to be finished in a weekend, or indeed a number of weekends due entirely to the nature of the presentation of parts. That brings up the second state-of-mind; 'Method Aforethought' - the art of being able to think the build through from the start - then as you go along - always working out what to do next and after that, what to do again and again, concentrating on making sure that the kit will go together as you want, and the manufacturer intended.
Clearly marked here is the widest part of the canopy - this is what will govern the width of the hull
The vast majority of vac-form kits do not carry instructions of how to put them together or the order in which each of the parts should be added, totally different to more-or-less any commercially available injection molded kit, therefore apart from the fact that the parts have to be cut-out from a sheet of molded plastic card the builder is very much on his own and therefore that is why vac-forms are for experienced scale plastic model builders, not beginners.All of the past paragraphs then led me to another discovery on the hull of this kit; as supplied, it's moulded too wide for the cockpit canopy and the true dimensional measurements against the real Sunderland.
The canopy at this stage only fits where it touches
Well, actually that may not be entirely correct; 'Yes', it is too wide as molded but that may not be the fault of the kit manufacturer exactly. All vac-forms are made by forming heated sheet plastic over a mold. That mold can be either accurate or in-accurate; it won't matter to the plastic concerned as it will simply adopt the shape it is molded over and some manufacturers make certain allowances and this one has one of them. That is 'draw allowance', least-ways that is what I'm calling it.

It's not a serious problem in any way once you know about it, that is. And that is exactly where 'Method Aforethought' comes in. The cockpit canopy is a superb transparent molding contained within the kit and my 'inbuilt' vac-form experience reminded me that the canopy cannot be modified, it is a molding of a certain height and a certain WIDTH and that's that. It is, and will always be, 'as provided' for I doubt if there are many brave souls that would consider modifying it. This of course highlights another point that is particular to this, and other kits of the type and that is 'how accurate is the kit'? I mean, it stands to reason that the kit comes 'as molded', right? And the cockpit comes also as molded, so why don't they at least nearly match in width (?) I sat there thinking. The answer was the next job in-hand.
Here you can see the relative pencil markings showing the difference in fit
Realising that the cockpit canopy was not going to be modified, I was reluctant to start getting out the tape measure, calipers and set square and start pouring over the hull to see what the exact measurements are and then compare with the known dimensions of the Sunderland at various points across the width of the hull. Not that I'm one of the 'if it looks right, then it must be right' brigade you understand, it's just that with kit of this immense size, molded from a long-ago built wooden master that someone carefully crafted - slightly smaller than the required dimensions so that the width of the plastic card as molded would be taken into account in the finished molded piece - if you did go to all that trouble only to find that the hull is dimensionally 5mm too high or 5mm too wide, there is very little that one can do about it, and frankly dimensional errors of that magnitude wouldn't notice to the eye on a model of this sheer bulk.
Clearly here you can see the issue in relative width - not a fatal problem though
No, I wasn't going to go that route. It's fair enough to expect millimetre precision on today's state-of-the-art injection molded kits but this is different and it is far better to build it to it's common denominators than try to aim for scale precision. Mind you, I know of at least one person who has built this very kit complete with all the interior details! God knows how he did it..!
This is the amount - the black line - that has to be removed from each hull half, give or take a mm
So, enough of this rambling; I took the decision to take a closer look at the hull to see what could be done to narrow it. That's when I noticed that - I hadn't spotted it before - there is the faintest raised edging to both hull halves. It's so feint that you wouldn't spot it unless you really looked closely under strong overhead lighting, but it is there and I took measurements of it on both hulls. I compared that against the overall width of the canopy at it's rear end, the widest point and 'Bingo' it looked almost a perfect match! In fact, it was better than that, it was as good as it's going to get.

I followed this raised mark all around the hull with a roll of masking tape and for the photo's shown here - for clarity - I filled in the gap with a black fibre pen. The depth was at least 4mm on each hull half that had to be removed. Always cautious, I checked and double checked the measurements to ensure that I was not taking too much off (that would be a disaster) or too little (that is curable, but I didn't want to do the same job all over again).
Keep your fingers well away from the edge as you make these shallow cuts 
Once happy that all was as good as could be, with a heavy duty craft knife fitted with a brand-new sharp blade, I lightly scored along the hull using the tape as a surprisingly good guide and commenced taking off the extra plastic. Remember, this is a job where one slip means a potentially serious finger cut, or worse, so just multiple light scores will do the job. Don't whatever you do try and do it in one heavy cut - it won't work and you'll be sorry. I know I was the first (and last) time the knife slipped and took a chunk out of one of my fingers................
The final test fit - still a lot of work to be done but close enough for now
All the way round, both hull halves and an hour later the job was complete. Now for the moment of truth; I carefully taped the hull halves together and offered up the canopy - 'Hey Presto', it fits! Almost a perfect measurement give or take a millimetre, but more importantly close enough. Job done!

Next up: joining the two hull halves.............