IanFS
Petty Officer 2nd Class
- Joined
- Apr 21, 2009
- Messages
- 188
Re: Boat wandering at slow speeds, videos attached
This question has a really simple answer and it's one to do with boat building. There is a lot more to it than I have written, but I am trying to keep it short and sweet.
Traditionally boats have been built with a keel also known as a keelson to which the frame is attached. In addition they would be designed with a proportionate sized rudder. The keel is the key to straight line cruising at slow speeds. Displacement craft have keels in one form or another.
Take the keel away and the boat will wander, which is what is happening with sportsboats. If you were to add a keel to a fast sportsboat it could dig in when turning at high speed and flip the boat. The trade off is the boat design and therefore low speed handling.
Finally a slow speed engine powered displacement craft would have propellers before the rudders in order that the flow of water produced by them flows over the rudder to assist in straight line perfomance and turning. One of the biggest mistakes with the Titanic disaster was that the Captain threw the engines into reverse.....the only rudder control was from the ships energy. It would have turned a lot quicker with flank speed over the rudders.
A stern drive only has water flow over its shape and again at slow speeds there is not a lot of control. So a sportboat will sail with "Three Sheets To The Wind" an old sailing term where 3 of the sheets are loose and the ship wanders.!!
I hope this helps explain it.
This question has a really simple answer and it's one to do with boat building. There is a lot more to it than I have written, but I am trying to keep it short and sweet.
Traditionally boats have been built with a keel also known as a keelson to which the frame is attached. In addition they would be designed with a proportionate sized rudder. The keel is the key to straight line cruising at slow speeds. Displacement craft have keels in one form or another.
Take the keel away and the boat will wander, which is what is happening with sportsboats. If you were to add a keel to a fast sportsboat it could dig in when turning at high speed and flip the boat. The trade off is the boat design and therefore low speed handling.
Finally a slow speed engine powered displacement craft would have propellers before the rudders in order that the flow of water produced by them flows over the rudder to assist in straight line perfomance and turning. One of the biggest mistakes with the Titanic disaster was that the Captain threw the engines into reverse.....the only rudder control was from the ships energy. It would have turned a lot quicker with flank speed over the rudders.
A stern drive only has water flow over its shape and again at slow speeds there is not a lot of control. So a sportboat will sail with "Three Sheets To The Wind" an old sailing term where 3 of the sheets are loose and the ship wanders.!!
I hope this helps explain it.
