Tuesday, April 28, 2009

The Dreaded Keel Joint

Last post I talked about refinishing my iron keel and the wonders of POR-15. At haulout my keel looked like it had done fine under the water; no signs of rust. This spring I found a line of oxidation along the keel joint, which you can see in the pictures.

Rust along the hull-keel joint.

This is likely due to the fact that I filled and faired the keel joint with fairing compound instead of a flexible poylyurethane bonding sealant. The fairing compound is totally stiff and showed signs of cracking in a few places. I scraped and sanded away the oxidation stains and antifouling paint. In a couple of spots I hit bare metal, so I knew I'd be off to the store for some more POR-15 and Interprotect 2000 to make a few touch-ups. VC-17 antifouling paint turns black within a few weeks, so sanding it off along the joint allowed me to inspect the situation more closely.

The hull-keel joint sanded

Things looked pretty good at this point and I was second-guessing my decision to do any major work on the joint. A couple of spots had cracked or missing fairing compound, and had allowed water seepage. I toyed with the idea of simply scraping and patching these spots. Initially I used a simple triangular can-opener, sharpened on a grinder, to scrape at the fairing compound in the joint. This removed a few small pieces of compound that hadn't bonded well or had rusted underneath, but in general it wasn't very effective.

The alternative was to use a dremel tool, but I was pretty reluctant to try this at first since I thought I might damage the gel-coat and fiberglass on the hull itself. Apparently the flange on the keel is about 5/16" high (that's the part that extends inside the hull) and by staying up against the flange, and using the dremel tool no deeper than that, cleaning out the joint with a small burr is alright. I donned my mask and goggles, bit the bullet and fired up the dremel tool. The result (of the port side) is seen below.

Keel joint after dremel tooling

The port side went pretty smoothly but the keel butts against the hull on the starboard side, making things more difficult. Once this joint is cleaned a bit more, perhaps with a bit more hand sanding ro remove fairing compound from the edges, I'll treat the keel side of the joint with Metal-Ready, POR-15, Interprotect 2000E.

After that I'll tape the hull and apply either 3M 4200 or Sikaflex 291 (essentially the same) into the joint, smooth it out. These are rapid-cure caulks and should be ready in 2-3 days for painting over with Interprotect 2000. Finally, VC-17 will go over the entire underwater surface.

Thursday, April 23, 2009

How to refinish an iron keel

Update: Canadian Tire has started selling both the POR 15 Metal Prep solution and  POR 15 paint.

Today at the Chandlery I found out a little secret... the shops that sell Interlux epoxy and paint products don't recommend using POR-15 because they don't carry it, and they make money by promoting the Interlux primers instead. Unfortunately Interlux doesn't manufacture a product like POR-15, so if you take the advice of the Interlux dealer you might be dealing with rust every couple of years on an iron keel. Interlux makes great products and I recommend them below, but for an iron keel you should start with POR-15 first, and then move on to the Interlux.

I refinished my keel in last spring and it's still clean as a whistle with just a smidgin of oxidation around the hull keel joint, which I didn't have time to finish properly. I'm really happy with the results so far and will probably carry on and deal with the hull keel joint this month or wait till next year.

(Update: as of spring 2014 the keel is still in great shape, and the hull-keel joint looks good, too. That's seven years and counting. Only the very bottom of the keel, which I couldn't reach, has some rust-scale on it. A project I hope to tackle in stages by raising the adjustable cradle pads and putting some 2x4's under the keel when I haul the boat out in late fall.)

This is a pretty big job, but it's doable. As a one-man job it took me about two weeks of steady work on evenings and weekends, without having much prior experience. Given the motivation, perserverence and elbow grease, it can be done by an amateur. There's always the alternative of hiring a pro to drop the keel, sandblast it, and professionally refinish it, and if you have a grand or so to spare, you might consider it. If that's not an option and you can get an extra set of hands to help, I wouldn't hesitate to tackle it. Here's what I recommend:

1. Get the old paint and rust off.

Use a grinder for this. Scrapers don't work, drills don't work. Grinders work good. I used a very aggressive sanding disk (designed for metal) with a backing plate, and also the meanest looking wire brush attachment I could find in Canadian Tire. My first attempt was using scrapers and they did almost nothing but remove some surface rust. The sanding disks worked well but I went through a half dozen or so rather quickly. The wire brush was pretty good as well, and by alternative between sanding disks and the wire brush, the keel cleaned right up.

It's very important to wear proper protection for this step including a respirator and protective glasses. The dust from sanding and grinding the bottom of a boat is toxic, nasty stuff and you do not want to breathe it in or get it in your eyes.

It's not essential to get down to bright metal. You're not setting your table with it. The bits of original primer that stick on the keel won't hurt. With a grinder you'll quickly discover all the rust pockets and make short work of them.

Some owners with heavy rust scale have reported that an air hammer works best. It depends how bad your keel has deteriorated but if you the rust is coming off in heavy flakes, renting an air hammer might be your best option.

2. Metal-Ready

Also known as POR 15 Metal Prep, you can get this at Canadian Tire now. This is a recommended prep before POR-15. It contains phosphoric acid. You can get other brands but this is the one I got from the truck shop that sold POR-15. Spray it on, and any remaining rust or oxidation that has happened since your last grinding session will magically convert into a zinc phosphate. You're supposed to wash this off with water. I was very reluctant to wipe my bare metal keel down with river water, but I did, and it was fine. Metal-Ready is a water based solution itself. It didn't start to rust like I feared, but instead rinsed most of the residue away and left a good surface for painting. This stuff works amazingly well to obliterate rust, and the zinc phosphate film left behind is apparently a good prep for POR-15 to bond with and helps prevent future corrosion.

3. POR-15

You can now get POR-15 at Canadian Tire. POR-15 is hands down the single best rust-preventative coating on the market today. It forms a chemical bond that converts rust into a rock hard compound and locks out corrosion. Unlike other coatings it actually cures and becomes harder in the presence of moister, so it's ideal for underwater applications like keels. I did three coats with about 8 hours between coats. It dries ultra-hard so you need to put the next coat on while the previous is still a bit soft.

4. Interprotect 2000

This is the famous epoxy bottom coat. I did not put this over the fiberglass hull because my boat shows no signs of osmosis. On the recommendation of a local yacht repairman, I did five coats over the keel, very lightly sanding the POR-15 first with a fine grit to provide a bit of tooth. I had no problem painting Interprotect 2000 over the POR-15.

5. Fairing compound.

This is getting to the last stage. Fair the keel with a fairing compound and sand it smooth. How much time you spend on this depends on whether you want a racing bottom or just a respectable cruising keel. Mine falls in the "respectable" category but I'm likely to do some more fairing work with time and conditions permit. Because time was running low, I faired up the hull keel joint without caulking. I recommend treating the hull keel joint differently however. I'm planning to dremel out the keel joint and caulk it. Filling it with fairing compound was a timesaving measure to be ready in time for last year's launch.

6. Hull Keel Joint

Update: I have written about fixing the hull-keel joint here:




The basic process is to clean out the joint with a Dremel tool, dab some Metal-Ready onto the exposed keel edge, paint with POR-15 using a small brush, over-coat with Interprotect 2000, fill in the gap with Sikaflex 291 caulking, and then paint over the whole mess with VC-17 antifouling.

7. Top Coat

On top of the fairing and caulking of the keel joint, put a top coat of Interprotect 2000. It mainly covers up the fairing compound and gives you a consistent color. Functionally it doesn't add much.

8. Anti-fouling

Everybody uses VC-17 around here. If you sand the old antifouling off your hull, use a really good air mask with dual filters and snug fitting seal around your nose and mouth. You do NOT want to breath this stuff in, it is highly toxic. Also wear safety goggles whenever you're working under the boat. Any drops or tiny spatters of paint, flakes of rust, or other nasties that land in your eye can cause serious damage. The VC-17 goes on watery-thin and dries fast. You have to work quick with this stuff. Tape the waterline and give everything below it a thin coat of VC-17. It's as shiny and bright as a new penny, and looks beautiful.

9. Launch

Watch all your hard work disappear under the water! Pray that it holds out for the season (and hopefully for another ten years). Iron keels add a unique dynamic to boat ownership and will always keep you wondering in the back of your mind how that big hunk of iron is holding up. Sure those keels all could have been made of lead with no fear of corrosion, but what fun would that be?!

Saturday, April 11, 2009

Sound Test

My attempt at creating a patch in Omnisphere. It's inspired by a Korg Triton combi but the sound here is 100% Omnisphere. The music is an excerpt from an original composition.



©2009 Darren DeRidder

Translate