4oz cloth - 100 or 200gsm?

áHi I'm building a Shearwater Sport kayak. We only get metric cloth here, and it seems the options are 100 or 200gsm for what I'm looking for. The plans specify 4oz, which as far as I can figure equates to 120gsm. Would 100gsm be too light? Regards Dave

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RE: 4oz cloth - 100 or 200gsm?

after a bit of research i found the following conersion table....

1.5 ounce cloth (50g)……..1 gallon (3.785 litres) wets out 40 square yards (33.45 M2)
2.5 ounce cloth (85g)……...1 gallon (3.785 litres) wets out 25 square yards (21 M2)
4 ounce cloth (135g)………1 gallon (3.785 litres) wets out 15 square yards (12.5 M2)
6 ounce cloth (200g)………1 gallon (3.785 litres) wets out 10 square yards (8.36 M2)
10 ounce cloth (340g)……..1 gallon (3.785 litres) wets out 6.5 square yards (4.4 M2)

so i suspect your 100 gram cloth is equivelent to 3 oz cloth...a bit thinner than what is spec;d.

my sense is that for most of the boat  you will be fine but you may need to double up in the cockpit/coaming area.  in Nick Schades book on building strip plank boats he has various layup recipes. (light, standard, heavy duty).  he gives a good illustration of areas that you want a little bit beefier layup.  but out towards the ends (fore and aft of the bulkheads), i think 3 oz on the inside is just fine...except for under the rear deck where you want as much as 12 oz (3x4oz).  hull bottoms outside are often doubled up as well. 

i have had no issues building 'light' boats with slightly less heavy layups than 'standard'.   i just don't smash them around.

alternatively, just go with the 200gsm...the boat will be a bit heavier and equivelent to a 'sturdy' build under most systems vs a 'light' layup with a 'standard' being 4 oz.

the folks at clc, i am sure would also be happy to answer your question if you called them or wrote to their tech support.

h

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