Invest five bucks
In a DIY manual, like the West System "Fiberglass Boat Repair & Maintenance" manual, or a similar publication. It covers all those issues in some detail, with illustrations etc. It may be possible to give you a 2-3 line answer to your question,but you have a better chance of success if you have better info. You might want to think about why those cracks are occurring too:it may be that something is inadequately mounted.
