Hull weight estimate 2008-08-26
New Cuboid was created on 2008-08-18. The styrofoam was sanded to 110.41mm x 93.66mm
x 75.28mm and weighed 23 grams. 778470 mm3 = 778.5 cm3 = 0.0295 g/ cm3
Hull area = 0.053 m2. = 530 cm2. So if shell thickness is, say 0.4 cm, core volume = 530 * 0.4
= 212 cm3 which weighs 6.24 g.
Area coated with epoxide is 11,05 * 9.38 cm = 103.7 cm2. Weight increment is 8 g. Therefore
weight of epoxide is 0.0772 g / cm2
Therefore weight of epoxide skin is 16 g. Two layers of epoxide is therefore 32 g or total
weight 38 g – rather heavy.
Try solid with one layer epoxide only.
Kg/cm immersion = 0.213 = 213 g. Mean freeboard =4 cm => above water volume is approx
852 cm3 Plus immersed volume = 366 g = total volume = 1218 cm 3.
This gives blank weight of 1218 * 0.0295 g. = 35 g. + one skin = 51 g. Distinctly heavy.
BUT this gives us a deck, much of the location for bits. Difference is marginal. Simplicity
probably greater with solid block.
We can also use a lightweight filler rather than solid epoxide for the surface finish. Say density
is half that of epoxide and volume is equal. Gives blank 35 g + surfacing 8g = 43 g. This has to
end up lighter than the hollowed out boat – not as light as a Gary Sanderson special but very
reasonable given the relatively small amount of effort required.
Go for solid.
AJCR
26 August 2008