Nearly had an accident, but why?

[thataway]

You are correct in your description of Porpoising. Most boats are designed to run fairly level when on a plane, and do not need much in the way of fore and aft trim (by tabs or a engine fin). If the Permatrim is running at the surface of the water, the bow will be forced down, but there will not be much upward force on the bow (actually the effect is all at the stern--lifting or depressing the stern--opposite to the way the bow reacts).

Normally you can bring a boat on a plane faster or planing at a lower speed by giving it full tabs and permitrim engine trim all of the way down. After the boat comes on a plane, then you bring the trim up, until you get the best speed for the RPM--often backing off on the throttle. Many boats need no trim alteration. The trim tabs are used for lateral (side to side trim) and the Permatrim more for bow down. Normally you do not want to run bow down because it will cause steering problems. In your case, you put bow down too much.

There are two things which can cause erratic rapid rolling. One is "chine walking" that is where a fast boat begins to plane on one side or the other and on on its bottom. Most often will occur in V hulled boats, such as bass boats at high speed.

The other is "Bow steering" That is where the bow begins to act as a front rudder, and pushes the boat one way, and then the other. It can occure with a slow boat coming off a wave, and is a component of a slow speed broach. It can also happen with a high speed boat which puts the bow down too much. The water on one side of the bow, causes pressure to push the boat one way, and then the other, instead of going straight. The cure is to bring the bow up and slow the boat down. In your case, you were probably going at the controlable limit of the boat for its weight distribution and attitude with bow trimmed down. Further trimming of the bow down, caused the bow steer.

When running down waves, always have the trim tabs up, and you want to run with motor (Permatrim) up also.

 

[Rich]

I had the same experience when I first got my CD22. I was on the ocean and had the trim tabs down runiing about 16kt. A steep wave pushed my stern buryed the bow. The boat went sideways and scared the heck out of me. After that I learned don't use the trim tabs on the ocean or in any rough water. In my second season I've been hit with some large stern waves and the boat handled them well. The boat was very stable and my confidence was restored. No trim tabs. I'm finding this boat has inherent stability that I think is easily altered by trim tabs. I use them in calm water but thats it. I'm a little skeptical about these permatrims too.

 

[Mullberry]

In respone to some of the questions:

This is a 1983 Angler with the flat bottom and no gradual v at the bow where the hull enters the water (I've heard it described as an iron, the kind you would iron your clothes with, and that is a pretty accurate description of the hull style).

It is powered with a 2004 2-stroke 40 hp Yamaha and has a 6 hp 2-stroke Suziki for a kicker. We had 2 gallons of kicker gas and 5 gallons of fuel on board for the main. The Suziki and 2 gallons of fuel where on the Port side (the side that dug in) and the 5 gallons where on the stbd. side. There were two individuals on board, myself at 195 lbs. on the port side, and the acting captain at 180 lbs. at the helm. Other than that, we had a few miscellaneous pounds of fishing gear.

I am not surprised we carved in on the port side, as it was heavier, but when we were running it was not noticeable listing to one side.

Normally when running, I run with the spray from the hull being produced about where the helm is located.

In looking back, we were clearly pushing the boat. I believe we came down, placing the bow down slightly off center, began to turn to the stbd while being heavy on the port, rolled down on the port, and it felt like the boat began running on the chine, using it for the bottom of the boat - instead of the flat bottom. It was like having the boat search for a "new" bottom and using the chine as that bottom - that also describes how hard the boat listed.

On a more positive note - I took my two boys out fishing this weekend and ran the boat in a more responsible manner. No problems - I kept the speed down and watched the boat trim closely. As I was working the trim it became obvious that if I was not careful I could trim the boat to a point where the main would cavitate. Still practicing but having fun, even without successfully catching a king.