Originally Posted by colemj
CSM is not used to bulk up thickness (well, it shouldn't be, at least). The purpose of CSM in a layup
is to help with print-through on the gelcoat
side and to help with bonding between layers of the real structural glass (cloth, stitched fabric
, roving, etc). In the first use, it should be only as thick as necessary. In the second use, it should be thin - for example, 18oz biaxial fabric
will use a 0.75oz CSM between layers.
If it is being used to make a layup
significantly thicker, then it is being used incorrectly and corners are being cut - or it is just a cheap
, non-structural part.
You are being a tad extreme in the "incorrect" statement, folks will do what they do for their own reasons. I am not going to judge that because I do not know their reasons.
I will state though, that if you are engineering a membrane using the skins as the key elements, it is a totally different structure than a solid mass of goop - whatever that goop comprises. At the end of the day, both can do the same job, albeit in differing manners and with different time and cost.