There are various methods but one issue is getting to the backside of the hull with no access nor inspection port particularly with small daysailors, catamaran hulls and so forth.
First I would cut the crack or hole out either in a rectangular, circle or oval shape. With a crack, cut it large enough where you can slip a finger in with 80 grit sand paper and sand about 1-1/2 inch inside and then wipe out with acetone. Next bevel the opening edge from the inside to the outside at least at a 45% or more angle.
Cut a piece of stiff cardboard about 1-1-2 inch bigger than the cut out area with string in it knotted on the backside. You may need one, two or three strings. Cut two pieces of glass the size of the cardboard and guide the string through it. Add a littler more hardner to the resin for it to kick quicker and apply liberally to the glass and coat the inside where you sanded. Then stick the cardboard into the cut area and hold with the string until it is adhering to the backside of the hole. Let dry and cut the string off. What you have done is preparing a surface which to lay glass on from the outside plus it locks the glass in which is a darn good strong area. Lightly sand after each coating.
Earlier I forgot to mention, the first piece of glass you cut, cut it exactly to the size of hole and then each successive piece of glass cut it bigger to overlap a little the first piece so only enough will go onto the bevel and bigger the next time. You do not want a lot of excess glass overflowing from the repair to the hole which can be a mess not to mention the extra sanding.
If you do not own a resin roller, you can buy one made by seadog and when using, clean off with acetone and immerse it constantly. You can roll the air out between the layers of glass as well as smooth it out.
If on a vertical surface, only one layer at a time; otherwise it will sagg on you. Once level with the outside surface, spray either gray or black paint on the glass and then sand smooth. When finished sanding, the remaining paint will show the valleys left. You will need to fill in with more glass or two part epoxy depending on what you see. When smooth, fill in with fine two part epoxy and then wet sand smooth after it is dry in order to fill in the fine pours. Then it is up to the individual to come back with gel coat or Krylon paint for plastics. Remember that gel coat uses a higher temp. hardner, not the regular hardner bought in a hardware store.
If you have any questions, email me via the forum email.
First I would cut the crack or hole out either in a rectangular, circle or oval shape. With a crack, cut it large enough where you can slip a finger in with 80 grit sand paper and sand about 1-1/2 inch inside and then wipe out with acetone. Next bevel the opening edge from the inside to the outside at least at a 45% or more angle.
Cut a piece of stiff cardboard about 1-1-2 inch bigger than the cut out area with string in it knotted on the backside. You may need one, two or three strings. Cut two pieces of glass the size of the cardboard and guide the string through it. Add a littler more hardner to the resin for it to kick quicker and apply liberally to the glass and coat the inside where you sanded. Then stick the cardboard into the cut area and hold with the string until it is adhering to the backside of the hole. Let dry and cut the string off. What you have done is preparing a surface which to lay glass on from the outside plus it locks the glass in which is a darn good strong area. Lightly sand after each coating.
Earlier I forgot to mention, the first piece of glass you cut, cut it exactly to the size of hole and then each successive piece of glass cut it bigger to overlap a little the first piece so only enough will go onto the bevel and bigger the next time. You do not want a lot of excess glass overflowing from the repair to the hole which can be a mess not to mention the extra sanding.
If you do not own a resin roller, you can buy one made by seadog and when using, clean off with acetone and immerse it constantly. You can roll the air out between the layers of glass as well as smooth it out.
If on a vertical surface, only one layer at a time; otherwise it will sagg on you. Once level with the outside surface, spray either gray or black paint on the glass and then sand smooth. When finished sanding, the remaining paint will show the valleys left. You will need to fill in with more glass or two part epoxy depending on what you see. When smooth, fill in with fine two part epoxy and then wet sand smooth after it is dry in order to fill in the fine pours. Then it is up to the individual to come back with gel coat or Krylon paint for plastics. Remember that gel coat uses a higher temp. hardner, not the regular hardner bought in a hardware store.
If you have any questions, email me via the forum email.
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