09-14-2012, 10:36 AM
I would say that Homasote isn't a necessary thing. It's a little like the advice fathers used to pass on to sons about the REAL way to drive a stick shift -- maybe it'll work, maybe not, but some folks think it's the REAL way to do it! The disadvantages include that it's hard to find, it's very messy to cut, and as Jack says, it swells and distorts if you get it wet (e.g., using water to apply ballast glue). The biggest reason it was advocated in the past was that it held spikes well with hand-laid track, although hand laying track is less and less common, with flex track readily available in several code sizes and gauges.
Celotex is an alternate product that based on a google search is available in the UK. They are both sold in 4x8 foot sheets 1/2 inch thick. The difference is that Homasote is compressed recycled newsprint, while Celotex is compressed sawdust. They are both used in construction for sound and temperature insulation. Celotex doesn't have the problem of swelling if wet, though it's still messy to cut. The advantage for modeling is that although Celotex doesn't hold spikes as well, it does do a good job holding track nails, which are hard to apply on bare plywood.
The advantage of either Celotex or Homasote is also that they're quieter, an advantage particularly with sound-equipped locos. However, to get things really quiet, you need to back both of them up with substantail plywood subroadbed as well.
Celotex is an alternate product that based on a google search is available in the UK. They are both sold in 4x8 foot sheets 1/2 inch thick. The difference is that Homasote is compressed recycled newsprint, while Celotex is compressed sawdust. They are both used in construction for sound and temperature insulation. Celotex doesn't have the problem of swelling if wet, though it's still messy to cut. The advantage for modeling is that although Celotex doesn't hold spikes as well, it does do a good job holding track nails, which are hard to apply on bare plywood.
The advantage of either Celotex or Homasote is also that they're quieter, an advantage particularly with sound-equipped locos. However, to get things really quiet, you need to back both of them up with substantail plywood subroadbed as well.