Increased stability

I decided to increase the weight of the keel to increase stability, or better to say, to increase the AVS. The stability of a Catalina 22 is sufficient as far as the action of wind is concerned, i.e. it is not tender, but with a wipe-out and waves you can easily go beyond 90 degrees, and that is when AVS becomes the most important factor. Increasing it by 10 degrees can mean the difference between making it home or not.

For that, I had to increase the weight at the tip of the keel. I decided to cast a lead bulb. First, I prepared a Styrofoam male plug which I shaped roughly following the keel shape in the bottom part. Then, I poored plaster into a big plastic box and then put this Styrofoam plug inside. When the plaster set, I removed the Styrofoam with a knife, scraping it out, and the mold was ready. I dried it in wooden fire during a couple of hours (it is very dangerous to pour lead into wet mold, it may explode due to vapor generation!) and then poured molten lead which was heated on the sime wooden fire. The finished lead plug weighted 36 kg. It was attached to the keel by means of two 3mm. thick stainless steel plates on each side of the keel and several through bolts both in the lead bulb and in the keel. Despite low weight, it was extremely difficult to attach the bulb, and two persons had to do it.

Keel bulb.

In the hindsight, it may have been better and easier to cast two halves of the bulb and bolt them to the sides of the original keel. The bolts and nuts in my arrangement protrude from the plates and create a small extra resistence which could have been avoided had I used two halves. Also, there is a separation between the cast keel and the bulb where nets and rope can catch, and it should be eliminated.

I have not run exact tests yet, but I did not feel any significant difference in speed so far. I have a very exact value of speed 5,75 knots (+-0,03 knots) with a 5HP outborder on lake, without any wind or waves before I did this keel upgrade, and I certainly will try to repeat this measure in the near future to see whether I have lost some speed.

Keel bulb.

The total weight added was 39 kg, and the keel became now 12 cm. longer. According to Catalina manual, the original keel weighted about 255 kg. I estimated that adding 40 kg to the tip were equivalent to changing the whole keel for one which weighted 375 kg (50 % increase)! I did not dare to add more than 40 kg. due to high torque load which would be exerted on the keel box and on the hangers and the bronze pin.

I also added about 50 kg. of lead inside the hull near the keel box area. I cast several smaller lead pieces to fit existing spaces and fiberglassed them with epoxy to stay put. It is far less efficient than adding weight to the tip of the keel, I calculated that 3-4 kilograms of lead in the bilge are equivalent to 1 kg. of lead at the tip of the keel, but it is much safer to add weight there than at the tip. Also, I had this crazy idea of what if... should the keel fall off (very unlikely, but happened before), the lead in the bilge may make the difference of returning home (although only in relatively good weather).

20 and 10 kg. lead slabs at the port side of the keel trunk (view from above).
Same slabs seen from side.

In total, I added 90 kilograms of lead, and the ballast ratio increased thus from 25 % (original swing keel design) to 35 %.

More lead in front of the keel box. The lead is wrapped in fiberglass cloth and glued with epoxy to prevent shifting.