Weighing a boat with bathroom scales

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DetroiTug
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Re: Weighing a boat with bathroom scales

Post by DetroiTug » Wed Mar 14, 2018 6:39 pm

Post some pics when you have a chance.

-Ron
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PeteThePen1
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Re: Weighing a boat with bathroom scales

Post by PeteThePen1 » Fri May 04, 2018 8:08 pm

Glad to see that this thread still has some life in it. Definitely looking forward to seeing any pictures of your new boat Mike.

Here, much later than ever expected, are the results of the bathroom scale weighing of Frances Ann, a Beckmann Rose hull fitted out as an English Gentleman's Launch. Why would one wish to do it this way? It was never possible to find a handy dock and public weighbridge and then I sold the large US built trailer that would not fit in the garage. I now need to source a small British one so the weight is a requirement. The 'float it in a tarpaulin' idea is lovely, and I do have such a giant beast, but I have not followed this thread for ages so missed the suggestion.

Basically the boat was weighed on a 4m plank with the boat 1m in from one end and and the scale 3m away at the other.
weighing the stern (500 x 375).jpg
No space to show the whole plank and the boat.
weighing the stern (500 x 375).jpg (66.42 KiB) Viewed 577 times
The individual removable bits were all weighed on the scale without the plank except for the boiler. For that we used the suspension scale approach:
Figure 3 (500 x 308).jpg
Figure 3 (500 x 308).jpg (21.77 KiB) Viewed 577 times
Once the job was done I was able to bring together all the individual items (All in kg):
(Sorry about the plain list - not sure if I dared cut and paste in an HTML table)

Saloon roof 11.0
Left side panel 6.4
Right side panel 6.4
Rear Panel 4.4
Front door panel 9.9
Cushions 2.2
Porta Potti 4.2
Sub total 44.5

Locker left 11.4
Locker Right 12.2
Floor grating 6.6
Swivel seat L 6.0
Swivel seat R 6.0
Sub total 42.2

Basic Boiler 79.8
Side panel L 4.0
Side panel R 4.0
Brass bands 2.6
Ash pan 3.9
Fire bars 6.4
Funnel 11.0
Sub total 111.7

Engine 56.2
Feed pump 4.2
Hand pump 7.6
Sub Total 68.0

Hull fore end 52.1
Hull aft end 116.9
Sub Total 169.0

Grand Total 435.4kg or 960lbs

It should be noted that the figures exclude all the plumbing and the brass deck fittings, not to mention water in the boiler or fuel in the bunkers.

Given that the general displacement weight given for the Rose hull is 544kg (1200lbs), it looks as if this is about right once you add back some figures for what will need to be added for use plus (say) 120kg for crew. It was also interesting to sketch in the positioning of the known weights on the hull:
Figure 4 (500 x 275).jpg
Figure 4 (500 x 275).jpg (29.36 KiB) Viewed 577 times
Many thanks to Lopez Mike for explaining that this was possible and to Mike Rometer for help in doing it.

Hope this is of interest.

Pete
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DetroiTug
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Re: Weighing a boat with bathroom scales

Post by DetroiTug » Sat May 05, 2018 2:08 pm

Hi Pete,

Quite an involved process, and the weight sounds about right.

The deck and coaming look good!

-Ron
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Lopez Mike
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Re: Weighing a boat with bathroom scales

Post by Lopez Mike » Sat May 05, 2018 5:15 pm

I'm impressed at how light it all is. I'm up to perhaps 800 lbs. with no machinery. Even allowing for the difference in length you have succeeded in avoiding the creeping mass issue. It will help a lot when trailering.
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