The Naiad Voyages

Mark Austen

2018.03.28 - Weighing Naiad Again

With the approach of some slightly warmer weather I decided that it was time to invert the boat and get the hull prepared for the paint and epoxy. It occurred to me that this process lifted Naiad off the trailer and I could use that to move the boat on the trailer to measure her weight the other and more accurate way. So I prepared the workshop by putting the reinforcement under the chain hoists and positioned the trailer so that the strops were in the correct place. Then I measured the weight on the end of the trailer by the tow hitch. Having noted down the weight I lifted Naiad off the trailer and moved the trailer forward a bit and let her down. Again the weight the same point as before was measured as was the distance the Naiad moved from the first position. Then I put her back onto the trailer properly, Finally I measured the distance from the wheel axles to the measuring point which gave me all the measurements I need for the calculation.

Initial weight: 47.7kg

Second weight: 10.7kg

Distance moved: 466mm

Distance from axles to measurement point: 3830mm

Putting all that into the formula gives a boat weight of 304kg with is vastly different from the 590kg for boat and trailer that I got before. Now the trailer is not 286kg so there is a big difference in the results. I'm inclined to believe the 304kg value as I could measure all the variables quite accurately with the exception of the distance from the measuring point to the axles and even if I assume a plus or minus 1% error in that, the results only change from 307kg to 301kg. A +/- 1% error measurement error is +/-38mm and I was much closer than that, perhaps within 5mm. Nevertheless even a +/- 38mm error only changes the result by 6kg.

Naiad is still on the trailer. I need to source something to hold her off the ground whist she is inverted. The last time I did this I used a few hay bales but I do not have those any longer so I'll have to find something else.