Re: Hull bounce?
Stuee, porpoising can be caused by different factors. Has to do with center of gravity of your boat, weight distribution, hull design. And it may take multiple things to remedy. Double click the attached picture . You are pushing a load balanced on a fulcrum from the rear. The load is your boat, the fulcrum is where your hull and the water lift occurs, it moves arouns as you acellerate. The force pushing you forward is the prop. If your engine is to low then it will exert forces to lift the bow, if engine is to high it will cavitate loose forward force and move the fulcrum. Engine trim is also a factor as it moves the angle of the prop in relation to the boat, more or less up forces applied to the bow. If rear is to heavy it will tend to keep bow up. Whats happening is as you are trying to push forward and also hold the bow down, it drops, but then at certain speeds or conditions the fulcrum moves, or the prop forward/upward force shifts, front to rear balance is lost and the bow rises back up. Then fulcrum then moves to a good spot and bow drops down and the cycle repeats. Basically the boat is not set correctly for all the forces needed to hold a steady plane. Correct weight distribution, motor placement, prop and hull defects are first to look at. The rest are just bandages if to hide the problem.
There are multiple things that can fix porpoising. Re-balancing load rear to front that you have already tried, raising the engine so it has more forward leverage and less up leverage (think theoretically of a prop 10 feet down in the diagram, how it would tend to push the bow up almost vertical). Tabs can be of value to to push up the stern. A lift type of prop will give a upward force to the stern. Sometimes it takes only one or multiple fixes. Hopefully you don't have a distorted hull that moves the fulcrum around and makes balancing a moving target.
View attachment 222745
Stuee, porpoising can be caused by different factors. Has to do with center of gravity of your boat, weight distribution, hull design. And it may take multiple things to remedy. Double click the attached picture . You are pushing a load balanced on a fulcrum from the rear. The load is your boat, the fulcrum is where your hull and the water lift occurs, it moves arouns as you acellerate. The force pushing you forward is the prop. If your engine is to low then it will exert forces to lift the bow, if engine is to high it will cavitate loose forward force and move the fulcrum. Engine trim is also a factor as it moves the angle of the prop in relation to the boat, more or less up forces applied to the bow. If rear is to heavy it will tend to keep bow up. Whats happening is as you are trying to push forward and also hold the bow down, it drops, but then at certain speeds or conditions the fulcrum moves, or the prop forward/upward force shifts, front to rear balance is lost and the bow rises back up. Then fulcrum then moves to a good spot and bow drops down and the cycle repeats. Basically the boat is not set correctly for all the forces needed to hold a steady plane. Correct weight distribution, motor placement, prop and hull defects are first to look at. The rest are just bandages if to hide the problem.
There are multiple things that can fix porpoising. Re-balancing load rear to front that you have already tried, raising the engine so it has more forward leverage and less up leverage (think theoretically of a prop 10 feet down in the diagram, how it would tend to push the bow up almost vertical). Tabs can be of value to to push up the stern. A lift type of prop will give a upward force to the stern. Sometimes it takes only one or multiple fixes. Hopefully you don't have a distorted hull that moves the fulcrum around and makes balancing a moving target.
View attachment 222745
Last edited:
win.
