I like a nice pre-rolled boiler and the C15 comes with one. This makes me a happy builder.
The instructions mention that you might not have to overlap the seam at the bottom. Odd, since there is a half etched section on either side of the gap to ensure a nice clean join.
Anyway, I merrily follow the diagram and solder in the two formers. They push the tube out slightly and so while the ends touch, they don't overlap. "That's what he means" I think. A bit odd but probably a niggle that didn't warrant modifying the etch. The smokebox is quickly and easily assembled and looks like it will fit the slots in the footplate.
Then I try the boiler in the body. It doesn't fit. Not by much but if I want it to go in there I'll need to whack the front with a hammer. Worse, if I do get it in the loco, the centre line will be too low compared to the smokebox. Looking inside the tabs it's supposed to sit on are bent down. Hmmmm
The problem is that either the tank tops are to close together or that the tube is too fat. The former are nigh on impossible to fix as bending the metal back to flat to allow me to remove a little, would see it split along the relieving lines. I hoped putting the boiler on a diet would solve it.
Out came the formers thanks to the persuasive powers of a lot of heat and some poking with metal objects. Not pretty but effective.
Re-fitting the now adjustable boiler things looked a lot better. The unit went in, the tank sides stayed parallel and the smokebox fitted. I tack soldered everything in place and looked again. Still OK. Making up a bracket that joins the tanks over the boiler showed it to be about 1mm under size. I can live with this, or at least I can compared to the alternative.
The boiler/smokebox join had a ring of fat copper wire fitted. Lots of solder, flux and heat made a reasonable job of this but I'll want to tidy up a little with some filler later. I know when it's time to stop waving heat around !
At the end of the day I think the problem is that the tank tops once bent over are slightly too close together. Taking around 0.5mm off each would make things fit better. The trouble is, that's only a theory and I suspect that the amount of metal to be removed depends on how you bend the top corners. And by this point you can't bend them back and removing the metal accurately is now very difficult. It's an example of the prototype not helping us modellers out.