The Rot Doctor


Subject: engine compartment floor beneath batteries
Date: Sat, 16 Oct 2004

I have a 1996 Crownline 266 LTD which has had the batteries mounted to the floor next to the engine as most are typically mounted. There is no carpet, only a gelcoated floor/liner.

The problem is as follows: the battery trays had been redrilled at some point by the previous owner and never sealed the original holes. There is a soft spot beneath the battery trays and it has spread to about an 15" x 20" area where the wood underneath the glass is soft. The area directly below one of the batteries is bad enough to the point where there is a hole starting. I have tapped around the area to pinpoint damage and there is good sound wood beyond the battery area.

What would be the best way to go about the repair? Should I replace the entire area with new plywood, resin and re-gelcoat or only replace the location where the hole is starting (say a 12" square) and treat with CPES and resin? Any advice would be appreciated.

Cutting out all the old damage and rebuilding is the standard way of repairing this type of damage. Treating the damaged wood in place with our products can be successful as well. Each method has its pros and cons.

Cutting out all or most of the damage is usually quicker and generally easier as far as getting all the damage treated. For a first timer, re-fiberglassing can seem a little intimidating. It is not actually that tough, especially using our products as they are very user friendly. Looking over a book on fiberglass repair would probably be very useful. Ultimately the toughest part is how it looks when you are done. It is not hard to pile up enough fiberglass cloth and epoxy resin to make the area strong, as long as you follow the techniques used in repair books. The toughest part is making it look like it was never repaired in the first place. If you don't really care what it looks like, it is not really that difficult.

Drilling some holes and treating the rotted wood in place is easier in that you are not required to do a lot of re-fiberglassing. It can be more time consuming because you do need to dry the wood out if it is wet, and the less area you have exposed, the longer this will take. It is also harder to be sure that you have treated all the damaged wood thoroughly if you don't open up the fiberglass. But it certainly can be done. And it certain situations can actually be the preferred method.

Generally I prefer to cut out the minimum amount of fiberglass. For your battery tray, I might cut out a 12" x 18" square of the top layer of fiberglass. If there is a bottom layer, it would be better to leave this in place. This would get you to within 2" of the edge of the damage, making it quite easy to dry the wood, and for the CPES to soak out to the edge of the rot, thereby guaranteeing a strong permanent repair. The wood in the cut out area could be either treated in place, or dug out and replaced using our Layup & Laminating Epoxy Resin. If you cut out the top skin carefully, you could even glue it back, leaving only a small cut line visible. In a structural area, you would want to grind a bevel in the top fiberglass on both sides of the cut line and re-fiberglass into be shallow groove. This procedure is outlined on our website.

For a non-structural area you could just fill the cut with Fill-It Filler and call it good, if you were happy with the look. A coat of white polyurethane paint would hide the repair completely.

I hope this is helpful. If you need further clarification, or have further questions, don't hesitate to get back to me.