As the weather gets colder, it has become time to put the polythene covered inner windows in the mesh covered frames at the top of the two end doors. One end goes in easily but I got the sizing wrong on the far end and had resorted to attaching it externally using screws, which is much more awkward than just slotting the inner frame into the outer one from inside. This year, I decided it was time to take the offending piece apart and fix it properly.

It looked like my mistake was to forget to account for the width of the two side pieces when cutting the top and then, when I tried to correct it I went a bit too far. Rather than buying more bits of timber (I was a bit short on suitable spares) I decided to 3D print pieces to both fill the gaps and to reinforce the frame. A simple timber square is quite weak if you are using pieces of batten for the sides and I think it was the attempt to create wooden corner reinforcements that threw me off before.

I did have to go through a few iterations. My first design was too weak in draft mode and would have thrown the spacing out if I had pushed it thicker. My final solution was a set of hollow right angled triangles with holes for small tacks and slots going in both directions near the right angle. I also printed spacers of the right size which would link with the slots and also allow me to use wood screws to fix the ends on to the sides. The result came out reasonably well and the final window, recovered with polythene, fits in neatly. Should we get a spell of warm days, I can pop it out for improved ventilation and, the rest of the time, it will help keep the internal temperature a bit higher than outside.