This plan will allow you to build a single axle V-nose snowmobile / ATV trailer. It includes the optional slide-out rear ramp and tray, plus ski tie-down bars.
Step 5. Next cut 2 pieces of 4" channel each 9' long for the tongue (I recommend this very heavy-duty tongue-you could substitute 3"x1/4" square tube if you wish, which will make installing the coupler a little easier). Set parallel touching each other on the trailer frame forming a rectangular tube. Mark with chalk a 2" line where the pieces join about every 3' or so starting with a 2" mark on each end. You want the chalk mark to touch both sides of the joint. Turn both pieces over and do the same for the other side. Separate the pieces and with a grinder, bevel the areas where the chalk is at about a 45 degree angle for the welds. Clamp both sides together and weld those areas.