Repairs

As I mentioned previously, there are two main problems with the trailer as it is right now.

This is the first. One of the side supports is so low that the end almost touches the ground.

This shows the errant support and you can see that it is not vertical but slanted backwards. This is due to it being so low that it dragged on the scaffold boards when we were hauling the boat and trailer on to the car transporter. Still, it needs to be fixed.

This is the second issue. Shoal Waters sites very low on the trailer. I can understand why that should be since this is also her launching trailer and the lower to the ground the hull is, the sooner the boat will float as the tide rises.

However, if you look across the trailer so that the top of the metal beam on this side of the trailer is level with the same beam on the other side, you can see that there is no space here to put a supporting beam on which the boat may rest and be raised such that the trailer can be moved out from under the boat.

There is also another issue but a minor one and that is that the side supports on the left hand side of the trailer are lower than the ones on the right and so Shoal Waters is resting at a tilted angle as you can see here.

When I was replacing the axle and wheels last week I took the opportunity to spray all the nuts and bolts that hold the supports in place with penetrating oil and I was delighted to find that every one turned easily with a spanner despite being fairly rusted. So much so that once I had leveled the boat on the trailer, or close enough for now, I crawled under the boat with the penetrating oil and liberally applied it to the bolts that hold the centre supports since I’ll be needing to raise those up once the trailer is out from under the boat.

Now Shoal Waters is almost level. It isn’t perfect right now but it will suffice since I need to get the changes to the trailer done before I can level the hull properly so that it is level with the trailer.

Now the very low support strut is a lot closer to being vertical and is also a little bit higher off the ground. Silll not high enough but that will be rectified later.

Finally, for today, I blocked up the stern behind the trailer so that there is lateral support once the boat is raised up off the trailer and no longer supported by the side supports.

Time for a cup of tea.

The following day I set too with paint brush and wood preserver to coat all the cut ends of the block in an attempt to slow the cracking of the blocks due to them drying out.

I jacked up the trailer one side at a time and blocked it up such that the tyres were off the ground.

So far so good and the whole thing is really stable allowing me to work on moving the axle without fear of the whole thing collapsing on me as I work.

I decided to move the axle forward 100mm or 4″, an inch or so more than necessary and marked the spot on both sides where the axle should end up. Then it was a case of loosen the nuts on the u-bolts and wriggle the axle forward to the new position. I say wriggle but in practice it was hit it with a mallet as the axle is heavy!

After a dozen or so small moves the axle was in the correct place and I tightened up the nuts again, jacked the trailer up again and took out the blocks. Now for the acid test. I suspended my 350kg scales above the hitch and measured the weight.

Not pretty but it works well.

Not easy to see in the bright sunlight, but the tongue weight of the trailer and empty boat is 37.4kg. That is pretty close to being correct, not that I’ll be towing this trailer anywhere but if I have to do that, then the tongue weight is not far off the correct value.

So, first things first. Off to the local timber merchant to buy six reclaimed railway sleepers. These need to be cut into blocks which will be used to support the trailer and the boat when necessary.

Railway sleepers are heavy so I cut them up by sliding them out of the minibus and cutting the end off, five times per sleeper.

Our super new electric chain saw wasn’t quite wide enough to cut the sleepers so I used the saw that came with the gardening tool thingy and that worked well.

Six blocks on one side of the boat…

… and six blocks on the other

The rest I stacked in the Hay Barn for now.

With the boat now on her trailer with wheels but pretty much empty, now would be a good time to check her weight. We do have a local weighbridge but you need to make two trips, one with the boat on the trailer and one with it off. This is not really practical for fairly obvious reasons. Fortunately, there is an easier option and that is to use a simple method taking advantage of what the physicists would call moments of inertia summing to zero. Fancy name for the fact that the centre of mass of the boat times the distance from the centre of the wheels pressing down must equal the length of the trailer to the jockey wheel pushing up.

But what about the weight of the trailer and the boats centre of mass, to say nothing of the centre of mass of the trailer, I hear you ask, well if you do the measurement twice with the boat moved a bit on the trailer between the measurements, all the unknown bits cancel out (I’ll publish the maths in another post for those that don’t believe me).

So, here is the method.

Move the boat backwards on the trailer about 4″ or 100mm. The more the better but don’t overdo it so that the boat tips the trailer back. Make a pencil mark on the trailer somewhere using a plumb bob from the bow of the boat. Now measure the weight at the jockey wheel, call it M1. You can use bathroom scales if you like but I use a 350 kg scale suspended over the hitch. Now measure the distance from the centre of the wheels to the point at which you made the measurement and call that L. Be as accurate as you can. Now move the boat back to its normal position and make another pencil mark on the trailer using a plumb bob from the same place that you made the first mark. Carefully measure the distance between the two pencil marks and call that D. Measure the weight on the jockey wheel again and call that M2.

Now, the weight of the boat is the (M2 – M1) * L / D

That’s it.

The only hard part about it is moving the boat backwards and forwards, but at least you don’t have to move the boat off the trailer completely and then back on again.

But before I can do any of that, I need to adjust the trailer in two ways. Firstly, the swing arms on the new axle are 3″ shorter that those on the old axle and I now need to move the new axle forward at least 3″ to compensate. Secondly, all the boat supports on the trailer are down very low. Too low to be able to put a beam under the hull but over the trailer that is strong enough to hold the boat up off the trailer, so the trailer has to come out from under the boat so that I can raise the supports as high as they will go.