Im re-building the sponsons of my Merc 2.4EFI modified tunnel boat, and my current deadrise angle is 15 degrees. Should I increase this deadrise angle?
Whether you do increase or not is up to you, but I can tell you what the performance result of the change will be. A higher deadrise angle will give better performance in rough waters, but a lower deadrise angle is more hydrodynamically efficient and thus can generate better acceleration and a faster top speed. The effect is complex, since the more efficient hydrodynamic lift also means less wetted length, changing sponson aspect ratio. The difference in going from a 15 degree deadrise to a 10 degree deadrise angle on conventional sponsons is a hydrodynamic (sponson) lift coefficient increase of 65%. This can translate into big performance improvements, even as much as +10 mph in the “over 100 mph” range. You’ve got to be prepared to accept the stability and handling degredation that will come with the changes, however. The TBDP, Version 7 does a great job of analyzing the combined impact of changes like these.
