X Dim
08-05-2007 | 05:26 AM
#2
the Flightmaster
Joined: Nov 2005
Posts: 331
Likes: 1
From: Stuttgart, Germany
No, the original definition of the x dimension is the distance from the driveshaft of the motor (input shaft of drive) to the lowest point on the vee.
However because this doesn´t take into account whether a shorty, standard or spacered drive is fitted, most people measure the x dimension as you have described, propshaft to bottom of vee (whether that is pad, or a conventional vee).
On a twin, the relevant dimension is measured from the hull bottom directly in front of the centrleline of the drive, to the propshaft.
On a single, 7"+ (prop to vee) is not unusual on older hulls running 3 blade props, but less than 6" is more common, these days, especially with 4 blade props. Stepped hulls can run higher drives than conventional vees, I believe.
90+ mph boats running 5 or more blades get down below 4".
My 80 mph 26 foot boat has a 4 1/2" drive height (on an extension box) and runs real nice.
The variables of hull design, weight, centre of gravity, prop, intended speed range make it impossible to generalise, too much.
However because this doesn´t take into account whether a shorty, standard or spacered drive is fitted, most people measure the x dimension as you have described, propshaft to bottom of vee (whether that is pad, or a conventional vee).
On a twin, the relevant dimension is measured from the hull bottom directly in front of the centrleline of the drive, to the propshaft.
On a single, 7"+ (prop to vee) is not unusual on older hulls running 3 blade props, but less than 6" is more common, these days, especially with 4 blade props. Stepped hulls can run higher drives than conventional vees, I believe.
90+ mph boats running 5 or more blades get down below 4".
My 80 mph 26 foot boat has a 4 1/2" drive height (on an extension box) and runs real nice.
The variables of hull design, weight, centre of gravity, prop, intended speed range make it impossible to generalise, too much.
