wrote in message
...

Ideally, the center of mass of the boat should be just ahead
of the axles, just enough to give you the tongue weight you're shooting
for. All else being equal/unchanged increasing the tongue length will
increase tongue weight by the amount of extra material in the tongue.

That's true, the tongue weight will increase by the weight of the
added material. (Actually, as Steven pointed out, some of that
added weight will also be supported by the whels.) But most
of it is nearer to the ball, and most will be supported there.

BUT, the weight of the added material is very small
and I believe can essentially be forgotten about. In our
example, an extra 3 feet of tonge would be maybe 20 lbs
of material. When we're looking for a tongue weight of
400#s, thats nominal.

What is ALSO true is that that longer tongue (all else
staying the same) moves the end of the tongue farther
away from the pivot point (axel). A longer arm (tongue)
gives more leverage. It would be easier to lift that
tongue off the ground or up off the ball. There would
be "less tonge weight".

Now I wonder how we ever made it to the moon, when a group of educated
intelligent men are debating the results of one of the most basic
engineering axioms. Also amazing is that so many people rush to proclaim a
known fact.......on a national stage............when they are exactly wrong.

I wonder how this thread would play out in Japan, or Germany?

Most people using and even building trailers are not engineers and the "rule
of thumb" is usually good enough for them. I've built 100s of trailers and
never needed to resort to a finite stress analysis or calculation of polar
moments to design a good trailer. However, knowledge of how these affect
the performance of the trailer is important.
BTW, I've seen trailers with very small tongue weight that tow just fine and
others with the "recommended" tongue weight but and unbalanced load (i.e.,
high polar moment) that sway all over the road.
The suggestion to: "Get the boat where you want it. Then make the tongue
the length you want
it. Finally move the axle to get 10% of the weight on the tongue.", is a
pretty good one... but 10% may be too little or too much depending on the
design and towing vehicle.
I've also build trailers with movable axle/spring frames to allow the
trailer to be blanced to carry different boats.


"Floyd in Tampa" wrote in message
om...
Now I wonder how we ever made it to the moon, when a group of educated
intelligent men are debating the results of one of the most basic
engineering axioms. Also amazing is that so many people rush to proclaim
a
known fact.......on a national stage............when they are exactly
wrong.

I wonder how this thread would play out in Japan, or Germany?