portager
Senior Member
Northern Spy has a good point. 23 kN is only 5170 lbs force. This isn't a very high load.
As far as the loading on the stringers goes, it isn't a twisting load on the stringer. The primary loading is up on the stringer that the boat is rolling toward and down on the opposite stringer. This load is distributed into the skin and the frames over a large area so there shouldn't be an issue. That said, I would still hire a Naval Architect or a structural engineer to perform a loads analysis if only for peace of mind.
The infinite load life statement is a typical fatigue loading term that a structural engineer would understand. In high-cycle fatigue situations, materials performance is commonly characterized by an S-N curve, also known as a Wöhler curve where S stands for stress and N the number of cycles. In some materials, such as aluminum, the S-N curve intersects the zero stress axis. These materials are said to have a finite fatigue life. Some materials, such as steel, the S-N curve becomes horizontal at a stress value greater than zero. This stress value is defined as the infinite fatigue life stress. When the structural engineer selects the adhesive bond material he will use this infinite fatigue life allowable stress to determine the minimum bond surface area that is required. There will also be a factor of safety that is applied to account for possible voids in the adhesive bond.
The initial target market for Seakeeper was Sportfishing boats because fin stabilizers have higher drag loss at planning speed and Sportfishers spend more time drifting or at trolling speed (where gyro stabilizers work better than fin stabilizers). Now, having made significant inroads to the megayacht and sportfisher markets, Seakeeper is targeting trawler owners as potential users of its new gyro stabilization system. Read more: Seakeeper Gyro Stabilization for Trawlers | OceanLines
They are also experiencing success in the Naval market. Seakeeper Sets Standard for Stabilizing Naval Vessels. Read more: http://www.maritime-executive.com/a...ard-for-Stabilizing-Naval-Vessels-2013-05-30/
Even though Seakeeper is new to the trawler market, they have delivered more than 1,300 gyro systems, and 374 were delivered in 2013, says Seakeeper’s Shep McKenney, who founded the company in 2003. I have yet to find a report of a Seakeeper failure.
“With every boat we draw now, we have to have a planned space for [a gyro stabilizer],” said designer Michael Peters, owner of Michael Peters Yacht Design in Sarasota, Fla. “Five years ago, we didn't even think about this. It’s a huge development. It’s becoming much more prevalent than we thought. We thought it was just for guys with larger boats and deep pockets, but with everything we design over 40 feet, the builder wants to know where the gyro is going.” Read more: VIDEO: Gyro stabilizers gain popularity | Trade Only Today
As far as the loading on the stringers goes, it isn't a twisting load on the stringer. The primary loading is up on the stringer that the boat is rolling toward and down on the opposite stringer. This load is distributed into the skin and the frames over a large area so there shouldn't be an issue. That said, I would still hire a Naval Architect or a structural engineer to perform a loads analysis if only for peace of mind.
The infinite load life statement is a typical fatigue loading term that a structural engineer would understand. In high-cycle fatigue situations, materials performance is commonly characterized by an S-N curve, also known as a Wöhler curve where S stands for stress and N the number of cycles. In some materials, such as aluminum, the S-N curve intersects the zero stress axis. These materials are said to have a finite fatigue life. Some materials, such as steel, the S-N curve becomes horizontal at a stress value greater than zero. This stress value is defined as the infinite fatigue life stress. When the structural engineer selects the adhesive bond material he will use this infinite fatigue life allowable stress to determine the minimum bond surface area that is required. There will also be a factor of safety that is applied to account for possible voids in the adhesive bond.
The initial target market for Seakeeper was Sportfishing boats because fin stabilizers have higher drag loss at planning speed and Sportfishers spend more time drifting or at trolling speed (where gyro stabilizers work better than fin stabilizers). Now, having made significant inroads to the megayacht and sportfisher markets, Seakeeper is targeting trawler owners as potential users of its new gyro stabilization system. Read more: Seakeeper Gyro Stabilization for Trawlers | OceanLines
They are also experiencing success in the Naval market. Seakeeper Sets Standard for Stabilizing Naval Vessels. Read more: http://www.maritime-executive.com/a...ard-for-Stabilizing-Naval-Vessels-2013-05-30/
Even though Seakeeper is new to the trawler market, they have delivered more than 1,300 gyro systems, and 374 were delivered in 2013, says Seakeeper’s Shep McKenney, who founded the company in 2003. I have yet to find a report of a Seakeeper failure.
“With every boat we draw now, we have to have a planned space for [a gyro stabilizer],” said designer Michael Peters, owner of Michael Peters Yacht Design in Sarasota, Fla. “Five years ago, we didn't even think about this. It’s a huge development. It’s becoming much more prevalent than we thought. We thought it was just for guys with larger boats and deep pockets, but with everything we design over 40 feet, the builder wants to know where the gyro is going.” Read more: VIDEO: Gyro stabilizers gain popularity | Trade Only Today
