Lessons from a Beer Can and a Sail

[schoonerdog]

Just wanted to pass this on. We have beer can races here in Annapolis every year. People basically can use two beer cans and make them into any shape they want. These boats are then put into a large shallow pool with some big industrial fans behind them and raced. The whole contest is for charity and it's a lot of fun. The winning designs are typically catamarans or tri's, but one thing was interesting to see. Many people would make their catamaran hulls nice and narrow and long and fairly stable, but connect them with cross beams that were joined at about half way up their hulls. The result is that the boat would only have a small amount of clearance underneath the boat. As the races would start, these boats would start moving very well. Then as they gained speed their bow wakes would hit their low crossbeams and stop them dead. The boats would then start again and stop again all the way across the pool. Interesting lesson on wakes in boats. A larger boat would have more mass and momentum, but still would be hampered by the wave action. I used to own and older PDQ 36 that had the step down into the main cabin that caused it to have 10" of clearance. When fighting up wind to get into the chesapeake it would struggle to make any forward progress at all, I suspect because of the bridgedeck hitting the waves. Down wind it wouldn't be much of an issue, in fact waves could push you along. My present boat has far better clearance and is much faster up wind, around 9 knots in 14 knots of wind sailing 55 degrees into the wind. Anyway, when people discuss how bridgedeck clearance is important in catamarans, that's what comes to the front of my mind. Not the slap, but the lack of ability to beat into the wind.