Then I moved on to the right side, which includes the living room bay window. I ran into trouble deciding how to treat the edges of the bay window, and ended up trying three different options before arriving at a fourth option which was my chosen solution.
1) I had already painted the bay window in my clapboard colour (green) before applying the blue window trim. My original plan was to apply clapboard only up to the window sill level, and leave the rest of the bay bare green. However, I found that once I started clapboarding up the side of the house, that when I looked from the front of the house, the bay side wall looked really naked and wrong. So I ripped off the side boards I had applied, back to the level of the windowsill. I am now using a British solvent glue called UHU, similar to QuickGrip but perhaps not as strong and more prone to strings, but I was able to rip the boards off.
2) I mocked up a narrow vertical strip of clapboard siding on some masking tape, and stuck it on the front bay side wall (the one you see from the front). This immediately looked a lot better from the front of the house, because it gave the continuity of the clapboard ridges. But it looked terrible from the side of the house because you saw all the rough raw edges of the clapboard ridges and the gaps between them as they rested on top of each other. And although I have seen pictures of other Willowcrests where keen builders have applied clapboard all around the tiny gaps between the window frames, I didn't want to try to do that with all the complex angles involved. Because of the big gap I had previously had to fill, between the bay front side wall and the next angled panel, my corner wasn't even sharp, it was more sort of rounded from filler and not even entirely straight vertically, so I didn't fancy my chances of trying to mitre clapboard around the corner.
3) I tried simulating the clapboard ridges by cutting appropriately spaced grooves into one clapboard, and sticking it on vertically on the bay side wall. I flooded the grooves with a little diluted black paint to give them the appropriate shadowing. This didn't look too bad from the front of the house, but didn't look very realistic from the side, so I took that off as well.
4) My final solution has been to stick an additional post down the side of the front bay wall, painted green to match the clapboard, and then applied clapboard in the remaining space between the post and the side wall. This means that from the front of the house, the eye sees the expected clapboard, but from the side of the house, the post gives a neat finish and you don't see the rough side edges of the clapboard. Painted green, the post is unobtrusive and the end result is acceptable. I still need to do a bit of paint touch up, but you can get the idea from the photos.
Happy new year to everyone following my build, and I hope that you have a productive 2008.