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Trailer for Rival 34

19 Jan 2016

Christmas 2015 will be fondly remembered by my wife and kids as a season of wind and rain and cabin fever while Dad escaped to "work on the trailer". Luckily I had the assistance of a very skilled welder / fabricator and the effort was occasionally supervised by a man who has owned many boats and trailers.

We had the use of a heavy machinery repair workshop and access to some scrap metal, including 2 mismatched truck axles and 2 girders of unequal dimensions which made up the parallel(?) sides of the chassis.

Some initial work was required to cut out the rusted and seized brakes from inside the wheels, and weld the axles to disable the built-in steering and prevent any future turning of the wheels. From there we proceeded to line up the unequal sized axles with the axle centres hopefully in a straight line between the wheels.

There were some existing holes in the heavy cast iron axles which we used in order to attach the girders, but as these holes were not exactly the same distance from centre on each axle the girders had to bend slightly to achieve this, and were then clamped and drilled with a heavy duty magnetic drill to make the fixing holes.

Once we had two girders fixed to two axles some cross pieces and end pieces were added. The next job was to measure from drawings and on the boat to decide the best positions for uprights, and to check the length of drawbar required.

The drawbar was made from another girder and the hitch was set up to to be approx 2 feet in front of the boat's bow to allow for clearance on the tractor cab.

It was decided to position uprights just in front of the mast and also about 10 feet aft of that position. Corresponding in theory to Sections 6 and 11 on the table of offsets / line drawings. It was useful that the height of sheerline and half-breadth of hull to outer edge of toerail were given at those positions in the table of offsets.

The 9" channel iron for the keel was sourced, this ended up being a little too tight for the widest part of the keel, which suffered a bit of compression and slight surface damage as it settled into its base on the trailer.

6 guide bars were added to help the keel slide down into the channel.

Improvements for next year

The boat is positioned a foot or 2 further back on the trailer from where it was intended to be. With a 10 foot keel base under the 6 foot long keel it is not a problem but we will add a horizontal bar in front of the keel for next time so that when the keel butts up against it we will know its in the right place as we position the boat on the trailer under water.

As the studs & nuts on the double wheels on one of the axles would need to be cut away in order to remove them, we had 5 wheels on 2 axles which performed ok on the road when being towed from the workshop to the slipway but I plan to replace a wheel or two before towing the trailer with the boat on the road. It only had to travel about 50 metres from slipway to its parking spot.

Materials / Dimensions: 
Main chassis girder length: 22 feet 
Drawbar & hitch made from another shorter girder

Cross pieces support under girders and providing the wider bases under the uprights were made from 6" channel iron, end pieces from girders and 6" channel iron.

Uprights: front posts approx 70mm diameter, rear posts approx 60mm diameter, one rear post hinged to allow the widest part of boat to pass through

Channel iron for keel base: 9" channel width (external) with approx 8" internal space and approx 10 feet long

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