In reality for the first month there were two lines of work going on in parallel but this post will summarize the upgrading of the trailer. Obviously that started as soon as the trailer was on our drive with an investigation into what was happening.
By the start of day 3 it was clear that the problem needed to be solved by replacing both of the original axle beams. The initial workable idea is to get two lengths of steel I beam and install those across under, or instead of, the original tube axles. Ideally I would have liked to use tube or channel but the dimensions werent working for me. The suspension units will be bolted to the web of the beams and rest between the flanges on the bottom while the original axle beam minus the strengthening plate could remain inside the other pair of flanges if everything fits. When it came to trying to source the beams it became obvious that I would need to use beams that were the same width in the web and flange directions and that the width of the suspension units meant there would not be room to leave to old beams in place. The steel was ordered as two custom items cut to the right length because the thickness of the steel meant I was unlikely to be able to cut it myself. That meant the steel didnt arrive until almost a week after the order was placed. In the meantime work on the boat progressed with it on the trailer wheels but also supported by axle stands. You will see that progress was steady but there is often not a lot that can be achieved in an evening after work.
By day 10 I had managed to remove 5 of the bolts holding the offside suspension unit onto the front axle but had to use the angle grinder to cut off the remaining ones. Nearside was only slightly easier but finally
got both units off.
My replacement axle beams are just that, RSJs to use the old name. As they are 152 mm across the web and 152mm sides they will definitely be strong enough but are challenging to drill because the metal is 6 to 8 mm thick. Matthew bought a pillar drill some time ago so that came out of the garage to be used in something like “clamp on” mode being moved around to drill the holes while the beam stayed propped up on 
bricks and wood blocks. By this stage I was working under the stern to keep out of the persistent heavy rain. Even on the slow speed and with plenty of lubrication the first set of holes proved a bit too much for my existing HSS drill bits. Each hole was drilled first with a 6mm bit then enlarged to about 10 mm. Final size was aimed to be for M12 bolts but I gradually removed the edges from the 12mm, 12.5 mm and 13 mm drill bits. By the end of the day I had 7 out of the 8 holes large enough to temporarily bolt on the first suspension unit. Going to get a pack of 5 Tungsten coated 12mm HSS bits in the hope they will last to get the rest of the holes done.
Day 11 (Sunday) Decided there is no point leaving the old beam in place when the new ones go on as it will be difficult to remove the strengthening plate with the beam still on the trailer. Removed the original front axle beam by hacksawing through the tube where it was welded to the logitudinal tubes. The beam proved to be still just about in one piece although I put a 90 degree bend in it at the position of the break with one hand to take the rust photo.
Underlying problem is that the tube walls had rusted from the inside until almost no steel was left in a critical area. Around half a mm left by the look of the side walls of the broken tube.
Day 12 Changed some of the old imperial bolts in the suspension units for the new 12 mm ones which arrived today. Not the easiest job with a ring spanner and ratchet driver because the bolts are a bit longer than the ideal. Need to get a 19 mm deep socket to make the job easier. No time tonight to try to drill out the remaining two 12 mm holes to fix the first suspension unit.
Day 13 Got the new socket on the way to work so could get straight on with the drilling and bolting of the second suspension unit after work. The completed axle was roughly located below the trailer as it finally got dark.
Day 15 After work I got started on trying to weld on the cross beam. Not particularly convincing at the first attempt as I need to weld between the bottom of a horizontal tube and the vertical face of the cross beam. Not enough metal left so it broke off when I put the full load on the offside end with a jack. As it got dark I had achieved a stronger set of joints on the nearside and the beam bearing the weight of trailer & boat but there is still too much gap between the tube and top of the beam on the offside.
I think I will weld an angle piece onto the edge of the tubes and use long 12mm bolts through to ensure everything is strong. Will also mean I can pull down the side tube to reduce the gap to fill and therefore increase the chances of a weld taking. Will also replace the three long bolts and steel plate cross piece between the axle cross member and the twin tubes of the tow bar.
Day 17 (Sunday) Welded on the pieces of angle (70 x 50 mm left over from the trailer decking frames) as reinforcing around the joints between the H girder and the side tubes and centre tubes. Looks 
convincingly solid this time so I replaced the wheels. The boat seems to be fairly much balanced on the front axle beam so hopefully this will be strong enough.
Removed offside rear suspension unit before we ran out of light. Got some welding tips from a passer-by on the path. He works as a computer technician but is a dingy sailor and seems to have done welding in a previous job. Apparently I need to use less current when welding “overhead” seams so the temperature is lower and the weld wont run off as easily. Also might be better with some alternative welding rods. I didn’t know this but welding in windy conditions can be a problem because the wind removes the gasses from the flux which protect the weld as it is forming. He reckoned my cross pieces are over-sized but seemed to agree that there is little harm in having them stronger and heavier than absolutely necessary. He also offered to help with welding if I have problems and gave me his card. I think I am doing reasonably OK but time and trailing the boat to water will eventually tell. It is well worth having a backup plan anyway.
Day 19 Drilled mounting holes for the suspension unit and bolted it to the beam. Much quicker with the tungsten carbide coated bits. Also packing Grace’s university stuff into the car and roof box ready for taking her back to Norwich tomorrow.
Day 20 Wed 14/9/16 I was planning to be at work for an hour or so until Helen came back from the GP but my Hospital transfusion team meeting has been cancelled so I have a bit of unexpected time available at the start of my day-off to take Grace back to university. Got up usual time, did the normal chores and was ready to start on the trailer by 7:30. In the 2 hours I managed to remove the final suspension unit, drill the holes in the beam and bolt on the unit. Just one bolt hole slightly misaligned so will need to loosen off the other 7 bolts to get it through.
Day 21 Eighth bolt now in place. Just needed the whole suspension unit moving a fraction of a millimetre. Started to saw off the old axle but there seems to be still some load on it as the first horizontal cut kept closing on the hacksaw blade. Rearranged the axle stands to support the boat better so should make more progress once I have replaced the broken blade.
Day 22 Got on with the hacksawing as soon as I could after work. Cut through both ends of the axle beam but ran out of daylight before I could try to undo the bolts holding it to the longitudinal tubes.
Day 23 Saturday I managed to get the second axle tube removed after using the angle grinder to take off the head of one bolt as it just wouldn’t budge even with the torque wrench. As with the first beam, the metal of the tube was reduced to being less than postcard thickness at the stress point between the reinforcing plate and the suspension unit. There was a surprising amount of rust still inside the tube.
By the evening the trailer was on 4 wheels again. Still have to sort out the brakes, re-align the mudguards and paint the new steel but I can at last start to make some progress with the boat instead of it’s transport arrangements.
Day 24 In the process of jacking the front of the trailer up to drain the cockpit through the stern I managed to break another of the welds between the front axle and the center tubes. Another bit of welding needed although as a relatively early weld this one also probably didn’t have as much metal involved as it needed. It is very easy to think you are bridging gaps with metal but actually it is mostly melted flux so has little strength.
Day 32 Repaired the broken welds on the trailer, more metal involved this time so may last a little longer. I can now get on with painting the trailer and concentrate on the boat.
