Thread: Building an off road boat trailer - plans?

Roverescue up in cook town knocks the up regularly.........he regularly puts his two bond worth in on here.

From memory he uses leaf springs for toyotas.

Hiya Andrew
First suggestion is to get the boat first.
It is far easier to design the trailer around the hull than try to make the trailer fit the boat later.
4.2 with say a 40 four banger will not be a very heavy rig so you wont need to go overboard. Im not a huge fan of using RHS on boat trailers apart from the draw bar which stays away from water. For main chassis I like PFC (Parrallel Flange Channel)
For a light 4.2 I would use 75PFC. On a 4.5 size rig I would step up to 100PFC. Hot Dip Galvanized post construction.

Other things to think about - Do you want it to be a tilt trailer - very handy for beach launching with big tides and helps to keep axles wheels out of the water.

Suspension design depends on what you want to do. For simplicity use 78 series Toyota rear springs with the two heavy load leaves removed then drop out a few of the thinner interleaves as well. Ends up being very soft riding (will need dampers) but is still a simple design. I have built a coil sprung triangulated fourlink boat rig which has stood up to years of abuse on Cape and Gulf roads driven by a toyota driver who knows no mechanical sympathy. Images of that rig are somewhere in this trailer section of AULRO.

For me priorities/ non-negotiable items for a alloy boat true bush trailer are:
-Same track width as vehicle
-Soft suspension to protect hull and outboard.
-Solid keel support (hardwood keel stringer is hard to beat for this)
-solid tie downs to keep boat planted on trailer 16mm threaded rod and a hardwood beam across the gunnels is a good start. Straps generally stretch just enough to allow hull pounding.
-Outboard leg support to protect the transom from flexing

Happy to help if you have any questions fire away!

One word of warning avoid using the AlKO et. al. readily available heavy duty rebound leaf packs. They will pound you hull to smithereens.

Steve

I totally agree with the soft suspension. I followed a guy up to the Cape towing his tinny on pretty standard type trailer. When we put it in the water up the tip it leaked like a sieve. It was full of stress fractures. Soft with good shocks will handle the corrugations better.

X3 with soft suspension.. Being softer, not only is it kinder on the load, but you don't get the 'jarring' on the tow vehicle. Love some pics of the builds Roverrescue.

Thank you Roverrescue for the detailed advice.

My issue is space at home. I already have a dirt bike trailer and 6 x 4 box trailer - both custom built to tow behind my 130.

So after much thought processing, I am going to just get a 3.3 V nose punt and mount it upside down on the box trailer. Will make a mount to house a 15hp outboard. I only plan on fishing/ exploring rivers, not the open sea.

I will be changing the springs out for a softer leaf pack with shocks as the trailer currently has standard trailer (shackle) rebound springs.

Thanks heaps