Trailer frame re-design thoughts

The frame rebuild could take on several approaches, each with pro's and con's. I've scoured the Investigator web forum to see other I 563 trailers. There are a wide range of designs from different manufacturer's. Some have mechanical brake systems like mine, others have hydraulic brake systems. The original wheels were just 13" with a straight axle (to get keel base lower). Allot, like Teria's, have larger wheel rims with an offset axle.

Some trailers have what appears to be 4" or 6" high main long beams in Channel or box section.
Some trailers have 3"x 1.5" channels for cross beams.  Others have only 2" high (box?) cross beams.

Also looking at other TS and large powerboat trailers too.

Choice of materials.

a) Use black steel box beams with final hot-dip galvanizing
b) Use C-channel beams with hot-dip OR pre-galvanized with cold gal paint on welds.

The only problem with box beams is that once the trailer frame is hot-dipped, then extra modifications can't be welded on later. The weld heat would burn off the galvanizing inside and create a future hidden rust spot. So things like side bunks/rollers must be U-bolted on, this is OK as then they are fully adjustable, can be moved or re-moved. Allot of Investigator 563 trailers have this system.

The open C channel beams would allow later weld customization. All existing and future fittings can be welded straight on. The other advantage of this would be in later trailer life it could be corrosion maintained so might last longer.

Choice of specifications

1) "Like for like" - replace with 3x2" beams. Add a 1/2" reinforcing steel rod rail about 2" above the frame.

2) Increase the vertical width to 4 or 5 inches for side frames.

A few variables to think about. A main consideration is to keep the trailer weight similar to the original. Visited the local steel supplier and picked up a steel stock specifications booklet to study, it has mass/meter for every steel section. The C - channel section has greater wall/ flange thicknesses than same sized box beams for the same outer dimensions..

Draw bar length

Increasing the draw bar length would be good. Teria's trailer's draw bar was only 1.1m long (3'7"), way too short for my tow-car setup. 1.8m long (6') or more seems far better. The length could vary depending on the location of the pivot hinge and length in front of A frame. A long draw bar would allow for back wheels of the car to remain dry and get the hull in deeper at the launching ramp. Turning circle may alter,??  If the winch post is further away from striking the ute's tray with a long draw bar it may actually help with tighter turns.

Trailer frame rebuild Ep2 - Stripping it down

Once the trailer was clear i put it up on stands.

Then measured up and drew some dimension diagrams, so it could all be re-built to size again.

Removed all the fittings. The bunk supports, rollers and their frames, wheel assembly, winch assembly, the draw-bar and it's pivot, the A frames apex plate, the jockey wheel fitting.

Some things were held on by square U bolts (50 mm inside width) , others were welded on so cutting discs on 9" and 5" grinders removed these.

(NB - I have oxy acetalene gear stored - this would have helped, but haven't hired the gas bottles for years  as don't use it enough )

Normally with the boat on trailer, it's very hard to see all the parts hidden under the hull. So these photos reveal some of the parts that are usually unseen.

The draw bar removed from A-frame

Trailer axle position

Draw bar on bench for dismantling

Stripping down the trailer frame

Axle, suspension and wheel assembly

Disc brakes, leaf springs and drop axle

Brake lever , disc

A good sized "deco" floored shed and workshop area - the shed posts are made from swamp paperbark tree trunks with bark removed (They are quite rot and termite resistant when concreted in, kept dry and sump oiled at the base)

Winch post assembly

Trailer frame birds-eye view

 I kept the frame mostly intact - so it can be used as a template/ base to build the new frame on.

5" cutting wheel on grinder - weld-on roller frame clamps removed.
Other frames had bolt-on roller frames

Trailer parts cut off - A frame apex plate, jockey wheel clamp, pivot frame for tilt arm

Bolt and nut to hold tilt draw bar (to A frame apex plate)

Tow ball coupling and brake actuator, brake lever - removed from draw bar and re-assembled.

Plan to re-use most trailer fittings on the new frame once built.

Trailers parts storage box

Trailer frame re-build Ep1 - breaking the trailers backbone

The old trailer frame developed too much rust damage. It wasn't galvanized and looks like it was epoxy painted long ago. I tried to maintain the outside with metalfix and zinc primer but saltwater got inside the 3x2" box beams and it rusted from the inside out. Holes were beginning to form at various spots in the frame.

So the boat and trailer were carefully towed to my shed with the intention of just replacing a few beams that looked bad.

There was a space limitation to fit the ute in behind a storage container so pulled the Teria into the shed backwards on it's trailer using a turfer winch.

Backing the boat in with a turfer winch

Turfer winch

The ute was connected to the trailer again, ropes tied to the deck cleats to hold it and the car inched forward incrementally to pull the boat back off the trailer. Wooden ex-railway sleeper blocks were laid under keel, props and ropes to chain plates held the hull upright.

I forgot to remove the tilt bolt, a critical error. The trailers main frame bent like Plasticine, creating an inadvertent tilt-trailer action as the hull weight bore down on the aft roller of the trailer. The trailers backbones had been broken.

On a positive note, it was better it happened in the work shed. The frame was declared a write-off and a new one needed to be built.

Bent frame

The rusted A frame joint buckled

A bent trailer frame

Well so much for replacing a few beams idea - starting to look like some major surgery is required.