Fiberglas cloth with or without mat, which to use

A local supplier (possibly not familiar with epoxy) told me that a layer of mat is necessary under the cloth for bonding purposes. He also said that without it, if the repair area takes a hit it would break (?come loose) that the mat sort of cushions the blow. I am using epoxy. I and have read that 2 layers of 12oz biax weighs as much as one layer of 1708 but yields more strength. I am more concerned about the integrety of the repair than wieght. Is his opinion valid for epoxy? Kevin

 

Hi, You will be pleased to hear, your detailer is talking complete B*******s.

Asuumption: repair is hand lamination only.

The reason why a light chop is often used on repairs is to increase the bond strength of the biax.

Basically, CSM are often resin rich laminate (typically 70-80% resin). Biax fabrics are some dryer (often 50%). Not sure if your aware, the key to laminating biax fabrics is to wet the fabric out by drawing resin up from underneath. If you were to wet out the biax from above, it is often very difficult to remove air etc from the laminate (because the fibres are in tightly stitched together). The key is to have just the right about of resin initially. (Remember resin matrix are brittle and fabrics are tough. Less resin is generally more (i.e. makes the laminate stronger)).

Your supplier is just a little confused. The chop ply before the biax acts as a resin rich surface to aid wetting the biax.

The chop will help slightly to product the biax fibres from abrasion. CSM will do very little for impact.

Epoxies are great for repairs as they are natural adhesives. Ensure your surface is properly preparied beforehand (i.e. surface is throughly abraded, dust free and has been degreased). Ensure to protect the suface around the repair area from resin splashes.

Hope this helps.