Replacing Rotted Balsa Core
In getting ready to awlgrip the cockpit floor I knew there was a soft spot underneath the fly bridge ladder I was going to have to address. Like all of these projects the problem was worse than what I thought. Balsa core is an interesting medium for boat building. In some ways its the worse material in the world for a marine environment, and in some ways it works quite well. Generally speaking the boat builders think its great, and the boat repairers are not so keen on it.
After much debate though I did decide to use balsa core for the repair. Intially I was thinking about just using pressure treated ply wood, but was concerned about matching the shape of the floor, it has a pretty good crown to it. The balsa core did work great in this respect, due to it being scored so much, it easily matched the curves of the floor.
Here is where I bought the Balsa Core it was $42 for a 2 x 4 sheet.
Here is where I bought the epoxy I used.
First up was trying to determine the extent of the damage. To do that I started drilling holes in the floor. The really bad spots are easy to recognize. When you drill out comes stuff that looks like wet peat moss.
Heres where you know its rotted; "soft as cream cheese!"
Heres a spot thats not to bad. Whats interesting is you can have spots that are quite strong, yet still have water drip out when squeezed.
Initially I thought the biggest culprit was the ladder, turns out it was the fill hole for the fresh water. Thats where a LOT of water got in. Here is a picture with the fitting removed.
I kept drilling until I found solid core.
I then drew lines to mark the section I wanted to cut,
then fired up the old skill saw and cut away.
Then I pulled up the floor. Probably everyone wonders if they can keep the top peice intact and then put it back down when the job is done. The only way that would be possible is with a small job, maybe up to 10 x 10 inch. After that its just not worth the aggravation of trying to pull it up one peice or even possible as was the case here. Once I got to where the core was not rotted, but still wet, the top was attached hard to the core.
Where the core is not mush, its still pretty tenacious.
Toward the end I had to cut up sections and use a chissell to get it up.
Getting there.
Done with that!
You can see here I dug underneath the old flooring about 1.5 inches, and will slip the new core underneath.
In the corner here I went a little further as it was a bit soft to leave it.
Once all the old core was out I began by putting the new core in on the sides of the cut out.
One big tip here, you can tap these blocks in but you can't go to hard or they crack and crumble. Getting them underneath the floor was challenging. In hindsight I dont think I really needed to drive them as far under as I did.
I worked my way around. After that I could use a few good sized peices. The thing with the balsa core is you have to get resin in between all the individual blocks.
On the back side of the sheets is cloth that needs to be wetted out.
Sorry about the dark photo's, but I have been working nights on this project!
Just about done with this part. I'm very happy with the way the balsa core curved to match the crown on the floor. You can see it pretty good on the right hand side of this photo.
After the balsa core was down, I took a grinding wheel to make a good bevel between the old and the new. Talk about dust!
Then I gave the whole thing a quick sanding.
Next I put down a strip of cloth around the permiter.
Then a full layer of cloth.
Here it is cured.
This is after two applications of cloth.
The I put down a layer of woven cloth, this stuff was pretty thick.
Here it is after I sanded it down a bit.
Overall its pretty close but there are some undulations to it I need to fare out.
Now back to the job of refinishing the cockpit floor