Posted by Eric Lindbeck on June 07, 2003 at 19:10:19:
In Reply to: Re: Is it a must to use Fibreglass cloth contd. posted by Mark Bronkalla on May 21, 2003 at 11:39:01:
: I think that the added benefit of cloth in abrasion resistence, dnet resistence and providing a stable survace that will not split or crack are major benefits. Our boat has been used (and abused) and there are number of times when the glass kep the surface intact where epoxy only would have split or cracked off.
: The micro-cracking and checking is especially an issue with fir plywood. The glass keeps the surface layer together.
: With 4 oz cloth , there is really not that much added weight or thickness.
: The downside of glassis in the applicaion, it will be less forgiving of letting a batchof poxy sit too long or of over-working (and foaming) the resin. It makes the epoxy applicaion definitely a 2 person process (one to mix and one to apply).
: As a mechanical engineer/boat designer/marine surveyor, let me say YES, YES, YES, you need to use the fiberglass cloth!!! The cloth carries the load - the resin simply holds it in place. Without the cloth there's not a lot of benefit from putting the resin on. Without cloth the resin is too brittle & won't carry the load.
The resin actually does more for abrasion resistance than the cloth. If the resin gets abraded away & exposes the cloth water will slowly travel along the fibers. For a boat in the water a lot, over time this will lead to layup failure.
If you want to avoid bubbles under your layup, do the job right. Prep the plywood properly before starting to wet out cloth. Cut the cloth carefully beforehand, and prevent any wrinkles. Be careful that your cloth lays flat, including rounding off any corners. Thoroughly wet out the cloth. Work out the bubbles under the cloth with a grooved roller (which can be cheaply made from washers). If you're worried about weight scrape away the excess resin - its not doing any good.
I could go on, but you know all that - it was in the Gougeon Brothers book you should have already read (or lots of other good books). The point is to do it right the first time. Practice on scrap if you're apprehensive. Boatbuilding is no place for cutting corners & doing a half-$%#$ job. At best you end up with a mess & waste your time & money. At worst people die. Do a job you're proud of & can rely on.
Ok, I'll get off that soap box now... Good luck with your project!