Patching holes in aluminium hulls
It is not uncommon for a thin-gauged aluminium hull skin to be punctured or torn by some unseen underwater object or unforseen trailering mishap. If you don't have skills or the patience for welding or riveting aluminium you can still effect a sturdy repair with G/flex 650 epoxy and the following items not included in the kit:
• XK0400 400gm Double-bias (+/- 45°) Fiberglass Fabric 0.762m x 0.762m
• WEST SYSTEM 808 Flexible Rubber Squeegee
• WEST SYSTEM 803 Glue Brush
• 80-grit sandpaper
These items along with the kit materials will allow you to repair a damaged area up to 15cm x 15cm as follows:
1. Hammer the torn aluminium back as close as possible to the original hull shape. Cut away torn edges as necessary for the metal to lie smooth.
2. Drill a 4.5cm diameter hole at the ends of each crack to prevent further cracking (5).
3. Smooth edges and rough areas with 80-grit sandpaper.
4. Abrade away any remaining paint in the area at least 5cm larger than the hole on the inside and outside of the hull (6). You can improve adhesion to aluminium by treating with an aluminium etch - follow the manufacturer's instructions.
5. Cut a piece of XK0400 400gm fibreglass cloth 5cm larger on all sides than the hole to match the abraded or treated area.
6. Dispense equal volumes of G/flex 650 Resin and Hardener into the mixing cup and stir thoroughly with the mixing stick.
7. Place the fibreglass on a piece of plastic. Using a disposable brush, apply the mixed epoxy to the fabric until it is saturated.
8. Position the wet fibreglass over the hole on the outside of the hull with 5cm of fabric extending beyond all sides of the hole. Use a plastic spreader to smooth the fabric against the surface while wiping off excess epoxy (7).
9. Mix a batch of G/flex 650 and stir in enough 413 Microfibre Blend Powder to thicken the mixture to a "mayonnaise" consistency.
10. Apply the thickened mixture to the repair area on the inside of the hull, filling the gaps in the metal and leaving a thin layer of the thickened mixture over the entire repair area.
11. Cut a piece of XK0400 400gm fibreglass cloth 5cm larger on all sides than the hole. Cut a second piece 2.5cm larger on each side than the hole. Then cut a third piece 0.6cm larger on each side than the hole.
12. Dispense equal volumes of G/flex 650 Resin and Hardener into the mixing cup and stir thoroughly with the mixing stick.
13. Place the three pieces of fibreglass on a piece of plastic. Using a disposable brush, apply the mixed epoxy to the pieces of fabric until they are saturated (8).
14. Position the largest piece of wet fibreglass over the hole on the inside of the hull with 5cm of fabric extending beyond all sides of the hole. Position the next biggest piece centred over the first. Then position the smallest piece centred over the previous piece. Using a plastic spreader, smooth all of the fabric against the surface, smooth all of the fabric against the surface, eliminate trapped air and wipe off excess epoxy (9). Check the outside of the hull to make sure the patch was not pushed away from the surface. Smooth it with the spreader as necessary.
15. When both sides of the patch have cured to a duct tape-like tackiness, mix a batch of G/flex 650 and stir in enough 403 Microfibre Blend Powder to thicken the mixture to a "mayonnaise" consistency. Using a plastic spreader, apply this mixture over the patch, filling and smoothing the uneven edges and blending both sides of the patch into the undamaged area around it (10). Allow the patch to cure overnight.
16. Wipe the area with water and sand the epoxy smooth and dull before applying a final finish. (If you are not satisfied with the smoothness of the patch repeat steps 15 and 16 before continuing with the final finish.)
17. Apply a finish coating to protect the epoxy from the effects of sunlight. If the hull is painted, you can coat the repaired area with a marine or automotive primer and matching paint. Follow paint manufacturers recommendations.
Note: Wherever fibreglass fabric is called, you may use more layers of lighter weight fabric that totals the same weight. For example, to equal 3 layers of 400gm fabric, you may use 6 layers of 200gm fabric to total 1200gm. Always make top layers progressively smaller than the bottom layer. Centre each layer over the previous layer with the edge of each layer stepped back from the edge of layer below it.