Trailer build

[Andy Young2]

I am refurbishing a 6.5m Libra Rib with 2x Yam 75's. It is apart at the moment and tubes are with Paul Tilley for replacement. The boat is in Muscat and has been stored and launched by tractor from a basic trailer which is now u/s.
I want to make a road trailer to take the boat to launch sites for diving.
i have the trailer pictured below but side rails are rotted out. I plan to cut the independant axles off and the triangular 'front end' and then add 2 new rails with cross beams, keel rollers and bunks. i would be grateful for advice on:

First size of box to use for main rails. i am thinking 120 x 50mm - any advice?

Secondly size of box for cross members (say 4)

Finally positioning of twin axle. I have access to measure the axle layout of the same size of rib on a professionally built single axle trailer. I can measure the position of the single axle in relation to say the stern of the rib and mark that point on my on my new trailer. However where should I position the twin axles in relation to the single axle mark. Axles centred equidistant around it, rear axle centred on mark etc...

many thanks in advance

[bedajim]

Originally Posted by Andy Young2

I am refurbishing a 6.5m Libra Rib with 2x Yam 75's. It is apart at the moment and tubes are with Paul Tilley for replacement. The boat is in Muscat and has been stored and launched by tractor from a basic trailer which is now u/s.
I want to make a road trailer to take the boat to launch sites for diving.
i have the trailer pictured below but side rails are rotted out. I plan to cut the independant axles off and the triangular 'front end' and then add 2 new rails with cross beams, keel rollers and bunks. i would be grateful for advice on:

First size of box to use for main rails. i am thinking 120 x 50mm - any advice?

Secondly size of box for cross members (say 4)

Finally positioning of twin axle. I have access to measure the axle layout of the same size of rib on a professionally built single axle trailer. I can measure the position of the single axle in relation to say the stern of the rib and mark that point on my on my new trailer. However where should I position the twin axles in relation to the single axle mark. Axles centred equidistant around it, rear axle centred on mark etc...

many thanks in advance

Any idea on what your boat will weigh ?

I'd go 120mm x 50mm x 6mm for your rails and then run a smaller rail (30mm x 30mm x 4mm) above it with some 120 mm off cuts as spacers to make two ladder sections.

I would run the two 30mm box sections onto the existing front triangle to give you an overlap of joints and also weld brace sections under the 120mm x 50mm box to give you a stronger join.

I think it's best to bolt the cross members to the rails with U bolts so you can move them and use them to mount the keels rollers. I'd do the same with the axles so you can move them forward and backward along the rails to suit your boat's loading. I bolted my axles to two long cross members with short rails at either end so you can then use these as fixing points for the bunks mud guards etc and it spreads the load.

If you want any pictures give me a shout

Jim

[JSP]

Jim I'd be interested in seeing the pictures please.

[Andy Young2]

Jim
thank you for your reply and for giving me some excellent ideas. I would like to see pictures. The problem I have in Muscat is obtaining things like U-Bolts and chandlery items. I shall get on the case today and see what I can source from Dubai.
The boat is a Libra 6500R dry weight 745kg, 150L fuel tank, 2 x 75hp Yamaha O/B.
Pictures below show the boat on the tractor launch trailer, resting on webbing straps.
Third picture shows how the independant axle is connected to the trailer rail via a bracket.
Final picture is looking forward to the forward 'triangular section' that contains tow ring, jacking leg etc (this is all sound)
From your suggestions my thought is to weld the two axles together using a short rail of 120 x 50 across the brackets to make a bogey. The main rails can then be inset 50mm each side on the forward triangular section so that the bogey can slide up and down to get the perfect nose weight on the trailer once the boat is completed and loaded.
Once positioned the bogey can be U-Bolted in place. Bunk brackets etc can also be U-Bolted in place. The advantage of this method is that I don't have to worry about positioning and welding the axles on at this stage.
It will be hard for me to get this galvanized. I propose to seal all the box section with welded patches is this the way to go or leave them open and flush out.
I look forward to seeing your pictures and further advice.

[Andy Young2]

Jim
Another thought; the bottom of the main rails will sit above the axle by say 50mm as the rails will be on top of the axle brackets. If I mount the rail crossmembers which will bear the keel rollers flush with the top of the main rails the rib will sit pretty high, meaning i will have to get my car further down the launching ramp than I would like to launch/recover.

Therefore I would like to rib to sit as low as reasonably possible on the trailer. To this end the crossmembers will either need bending or welding into a flattened v-shape so that the keel clears the axle by say 75mm. Do you think this is enough clearance for the type of axle? I am unable to testhow much the suspension deflects until I get it all together however the sheet steel that makes up the current trailer bed is 5-6mm.

What size of box section would you recommend for the crossmembers bearing in mind the weight of 745kg plus, fuel and motors - I am thinking of using 4 crossmembers and 4 keel rollers plus a bow roller/stop.

Once I know what size of box section I can then see if I can find anyone to bend the steel as I need it. Attached are two examples from trailer under another rib undergoing refurb. These crossmembers look like 120 x 50 but less than 6mm. They 'drop' by about 150-175mm from the level of top of the chassis rail. The third picture appears to show abou 150mm clearance above the Land Rover tyre but this trailer has no suspension.

Thanks again for your advice

[bedajim]

Originally Posted by Andy Young2

Jim
Another thought; the bottom of the main rails will sit above the axle by say 50mm as the rails will be on top of the axle brackets. If I mount the rail crossmembers which will bear the keel rollers flush with the top of the main rails the rib will sit pretty high, meaning i will have to get my car further down the launching ramp than I would like to launch/recover.

Therefore I would like to rib to sit as low as reasonably possible on the trailer. To this end the crossmembers will either need bending or welding into a flattened v-shape so that the keel clears the axle by say 75mm. Do you think this is enough clearance for the type of axle? I am unable to testhow much the suspension deflects until I get it all together however the sheet steel that makes up the current trailer bed is 5-6mm.

What size of box section would you recommend for the crossmembers bearing in mind the weight of 745kg plus, fuel and motors - I am thinking of using 4 crossmembers and 4 keel rollers plus a bow roller/stop.

Once I know what size of box section I can then see if I can find anyone to bend the steel as I need it. Attached are two examples from trailer under another rib undergoing refurb. These crossmembers look like 120 x 50 but less than 6mm. They 'drop' by about 150-175mm from the level of top of the chassis rail. The third picture appears to show abou 150mm clearance above the Land Rover tyre but this trailer has no suspension.

Thanks again for your advice

Hi

I've not got my camera at work today but will post pictures tomorrow

Jim

[Andy Young2]

Many thanks Jim
I have sent my enquiries out regarding steel and U-Bolt availability and will get the old trailer cut up into the components. I have been amazed at the ingenuity of the local suppliers. I had missing ignition keys for Johnsom motors and a chap had keys cut to fit the barrels within half an hour.
regards

[bedajim]

Some pics of the trailer during build, showing the cross members etc

Mine has a cradle for the boat but you can see the ladder rails and the cross members with the longer ones at the axles held on with u bolts. If you can’t get u bolts you could weld some flat bar onto the cross members and bolt over the top of the rails, you can also see the stiffening bar over the join in the rail.
Third pic is of the longer cross members for the axles etc

[bedajim]

couple more

[Nos4r2]

Off topic, but who did you use for galvanising?