>> The all-up weight of your trailer, boat, and gear ought to be about
>> 1,700-1,800#. Thus, you want about 170-180# at the tongue.
OK, assume 1800 lb for the boat, trailer not included (Ursa Minor
measured over 2300 lbs, loaded), and assume the distance
axle-centerline to hitchball-centerline is 143" (as I just measured
on my Shoreline trailer): each inch that you move the boat forward
will increase the tongue weight by approximately 12.6 lbs. Converting
this to a dimensionless case, each inch forward will increase tongue
weight by approximately 0.7% of boat weight. This assumes (1) that
trailer weight has a negligible impact, (2) that the trailer remains
horizontal, and (3) that you move the boat, not the axle (either is
possible, but the former is easier).
FWIW, I'm familiar with the 10% rule-of-thumb for tongue weight and
often advise others to use it, but I have carry only about 5% and
experience no sway at all -- over about 25,000 miles. This may,
however, be because I tow with a full size van, which for a number of
reasons is an ideal tow vehicle. I did have to move the boat a bit
forward in the early days to achieve this weight.
Regards,
Bill Combs
WWP 19 #439 (Aug 1987) "Ursa Minor"
Fort Walton Beach FL
ttursine@gnt.net