I liked the travel lift idea, but the lifting webs will have to be vertical, or at least the angles of them to the vertical must be known. The only trouble is what it costs to have them lift it.
If you had another trailer for an afternoon, particularly if it had one axle, it could be done.
If you know the vessel's weight, you could measure what the toppilng moment is. Typically, the trailer would want to tip forward, so if you could measure the force at the towbar ball to correct it, then classic moment balance would betray the C of G.
Allow the distance from the towbar ball to the axle to be : a
With the trailer laden, allow the force at the towbar ball to be : F
Allow vessel weight to be : W
Allow the C of G to be an (unknown) distance b forward of the axle.
Moment balance dictates.... F*a = W*b
such that... b = F*a/b
When you have worked out what b is, chalk the hull with a vertical line.
This approach neglects the toppling momernt of the trailer arnm itself. If you don't want to ignore it, the equation needs modifying a wee bit.
I haven't figured out how to measure the forces yet as a bathroom scale is not likely to work.
If you have a crane, one easy way is to keep lifting the boat onto the trailer until it balances. make sure that the towbar is connected though, as it may topple backwards if it is not.
Last edited by Rockter; 01-28-2009 at 04:10 PM.