On Fri, 28 Oct 2011 15:10:51 -0700, "Steve B"
wrote:

A friend of mine brought me a boat trailer that he wants me to put some
sides on so he can use it for firewood collection. I figured it was going
to be a basket case with rollers, etc. But someone did a right fine job of
redoing it. It has at least four horizontal supports, not sure of what
they're made of. The outer frame is square tube, like 2 x 4. If is decked
with angle holding the decking on, and carriage bolts holding it to the
horizontals. It is single axle with 15" 5 lug wheels, and a stout axle. It
looks the size that would be used to carry like a Searay, or some other
fairly substantial boat. Estimated length of said boat would be 18'.

The positioning of the axle with relationship of the deck is good with
relationship to putting the load right over the axle, with the deck forward
enough to keep it from being tongue light. I'd say 2' - 3' more forward of
the centerline than behind the centerline of the tire.

I like the idea of making the sides stake-sides, then he can pop them
out and use it as a flatbed. There are standard sized steel stakes
and pockets and side panels, or you can make your own pockets out of
Seamless Square Tubing on the chassis, and regular for the stakes.

BUT make sure to have a lock-in method for securing all the stakes to
the chassis, especially on a trailer they do like to bounce out on the
road. And the CHiPpies get real mad when you drop stuff on Their
Freeway.

Drill a hole through the stake and pocket, and put in a PTO Pin, a
Ball-Lock Pin (with a leash, of course!) or a plain old bolt and nut.
Or weld a nut on the pocket and use a short bolt with a T-handle to
lock it in through the outer face of the stake - Do NOT clamp the
stake in, it'll bend and never come out... Then you can get the
standard stake-bed L-latches for the top edge.

My question is what is the best way to approximate the new carrying capacity
so that I know how high to make the rails, and use that as an indicator of
when the trailer is loaded? I did not look for a plate, and suspect if I
found one, everything may be changed due to the modifications already done.

Do a little digging on the Net - they use "standard" axles, springs,
tires, and other pieces to build trailers. And those pieces come in
standard 'steps' of GAWR capacity - 1,000# and 1,500# for little 8"
tire DIY chassis, 2,000# 3,500# 5,000# and occasionally 7,000# for
13"- 15" wheels.

The chassis GVWR is usually permanently marked on the VIN and ID tag -
if you can still read it. Measure the springs - width, thickness,
number of leaves, and you can fairly easily match them up in a spring
catalog and get their ratings.

Same thing with the spindles - look up the replacement hubs and
bearings, and that catalog page usually gives you the ratings. If you
keep getting the same answer every time, that's probably it.

For a small single-axle boat trailer it's probably a 3,500# axle but
you need to make sure. Then you take the completed trailer to a
Public Scale and get the empty chassis weight, subtract that from
3,500 GAWR and there's your load capacity.

Yes, the tongue and tow vehicle takes some of the load, but you don't
want to shave it that close all the time.

And if the guy's worried about overloading it, you look at the springs
that have a nice arch - when the arch goes flat, it's full.

You could install rubber "bullet" snubbers on the chassis so it
doesn't make a hard crash bottom-out on bumps, then put in a Test Load
of bricks at GVWR and proper 10% tongue weight to get an exact ride
height.

Then you tell him to stop loading when there's exactly (example 3")
left between the spring and snubber. Cut him off a (3") chunk of
dowel with a broomstick handle to use as a "Go/No Go" gauge.

-- Bruce --