I awoke at 5:30 AM and departed Santispac anchorage in Bahia Concepion at 6:20 AM destined for Caleta San Juanico. It is a 54 mile journey and I wanted to be certain I arrived at San Juanico and was safely anchored before dark. It was cool and there was a 12 knot wind blowing from the north when I departed.
After about 45 minutes I got a call on the VHF radio from Matt and Rachel on Aeoli. They had departed earlier than I did and were ahead of me. They called to say that they were on their way to San Juanico also. I over took them about 3 hours into the trip. I was able to overtake them because my boat is about 10 feet longer that their boat.
The top speed of a displacement hull, like the ones we have, depends upon the boat’s waterline length. That is the distance from point where the bow (front) of the boat first makes contact with the water to the point where the stern (back) of the boat last makes contact with the water. The top speed of the boat is 1.34 times the square root of the waterline length. My boat has a waterline length of 34’ 6” so it has a hull speed to 7.87 knots. This limitation exists because as the boat moves through the water it makes waves. The faster the boat moves the longer the waves it makes. When it is going at hull speed, it makes a wave that is exactly the length between the bow and the stern. Essentially, the boat gets captured within the wave it creates. If you look at the boat moving through the water, you will see a wave crest at either end of the boat and the wave trough in the middle of the boat. To make the boat go any faster, you need to add enough energy to climb up and over the wave and make the hull skip along the top of the waves. That is what small runabouts and water ski boats do. They have a powerful engine, relative to their size, which is capable of lifting the boat above the waves the boat creates while underway. A sailboat like mine, does not have a powerful enough engine to do this. Even the sails cannot generate enough force to overcome this limitation. The only time the boat exceeds its hull speed is when it is surfing down fair large waves. Then the boat is moving at nearly the speed of the waves, and the waves may be moving fast enough to exceed the boat’s hull speed.
By about 11:00 AM the wind was blowing at almost 20 knots from the northwest. By using both the engine and the sails, I was able to move along at about 6 knots. As the afternoon progressed, the wind grew strong, as it normally does, and it was blowing at up to 30 knots. Between the engine, the strong wind, and the waves created by the wind, the boat was moving along at over 8 knots with occasional peaks of up to 9 knots. This speed was possible because the boat was surfing with the wind waves.
I arrived at Caleta San Juanico at 2:40 PM and was anchored shortly thereafter. “Aeoli” arrived before 4:00 PM. “Scottish Mist” a Westsail 42 from from San Francisco with Bob and Doreen aboard, “Sagittaire”, and a boat with no name were already present in the anchorage when I arrived.
I will need to listen to the weather report on the Saturday morning cruiser’s net before deciding what to do next. The last forecast I heard on Thursday was calling for a Norther to blow at 34 knots on Saturday and Sunday. That may keep me here for the next two or three days. Even after a Norther ends, it takes a day or so for the seas to calm down.
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