Tuesday, April 14, 2009

Bunn's Feed & Seed, Part 6: Roofs

[Barn roof panels]

When it comes to building the roofs it’s all about the balsa.

I followed Mr. Moore’s recommendation to build the roofs for the buildings from 1/8 inch sheet balsa. I drew and cut the roof panels so that the grain ran parallel to the long axis of each building. This may have been the wrong thing to do since there was a little warping when the overhangs were painted and the coverings were glued down. On future builds I’ll use 0.060 inch or 0.080 inch sheet styrene instead, but, as I’ve mentioned previously, in this project I was trying to stick close to the methods discussed in the article.

[Addition roof panels]

The roof panels were attached to the walls with super-glue. I had to pay special attention to making sure the panels were firmly glued to the wall corners to help minimize warping caused by painting and gluing the roofing material. There were a few times when I had to go back and do a little more gluing to secure sections of balsa that gapped during later stages of the roof build.
The ‘metal’ panels used to cover the barn roof are made using the same scribing technique discussed back in Part 3 that was used to make the siding for the addition. However, in this case, the scribes were made in every fourth groove.

The scribed panels were attached to the balsa with a very thin layer of white glue washed over the balsa. The lower panels are applied first, and then the upper one, slightly overlapping the lower panel. To finish off, a strip of paper was glued along the ridge.
The addition has a little bit of the main structure protruding into the roof. The side walls for the protrusion need to be installed before proceeding with the addition’s roof. These side walls were cut from styrene – dimensions as per the article – covered with scribed siding, and then glued in place with super glue. A small balsa roof extension was then installed over the sidewalls.

Mr. Moore recommends covering the roof with ‘tissue’ strips to simulate tar paper roofing. I wasn’t sure if he meant using tissue-paper or facial tissue. Instead, I used strips of masking tape. I used this method way back in the ‘70’s – can’t remember where I read about it – but it can be effective since it does give the roof surface a little texture. Don’t rely on the tape’s own adhesive to hold it in place. Use some white glue. I still have a scratchbuild from the ‘70’s on which I used this method; it has held up well and still looks passable.

After this project was done I read a few other scratchbuilding articles from that era and found that ‘tissue strips’ refers to single-layer facial tissue cut into strips and glued in place with thinned white glue. No doubt this would work well.

The roofing on the addition was finished by adding a paper strip along the ridge to simulate flashing. I think the strip is a little too wide, but once some weathering was done on the roof, and the overhead piping was added, it becomes less noticeable.

The barn’s metal roofing was painted with Tamyia flat aluminum, and the addition’s roof was painted with Tamyia medium gray. Later, both roofs were weathered with thin washes of flat black. Also, a thin washes of Polyscale Rust was used on the barn roof, and PolyScale Dust was used on the addition.

The chimney was then added to the barn roof. This is a scratch built item. Styrene embossed with HO-scale bricks were used to cover a balsa core cut to the size of the chimney specified in the article.

One last item that Mr. Moore doesn’t appear to discuss in the article: I found that the roofs need to be notched in order to get the placement of the silo correct. My silo’s diameter is probably a little off, which necessitated the roof notches to help make sure the footprint of the overall complex is maintained. Unfortunately I didn’t realize this until the roofs were in place and covered. I had to cut the notches, and do some touch-up, when they were firmly glued in place. Do some test fitting to make sure everything lines up before gluing down the roofs – this will go a long way to making final assembly easier and neater !.

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