Soaks up the water, but how much?

[sandingblock]

Down here in NZ we have a lot of macrocarpa avalable, know boatbuilders use it a bit, but is reputed to 'soak up the water' and make for a heavy hull. How heavy? It's a fairly light timber to begin with, after taking up water is it about as heavy as teak? oak? lignium vitea?

[mic]

Hi Sandingblock,
i believe that Macrocarpa is a member of the white oak species (lepidobalanus). It's scientific name is Quercus Macrocarpa
but it's commonly known as either,Bur Oak, Blue oak, Scrub oak etc.
Bur Oak is slightly different to the traditional American or European White Oak (Quercus spp)in that it is slightly softer when seasoned. This sometimes could be a good thing with plank on frame movement, Bur Oak also has a slightly darker color and it's ADD rating (AIR DRYED DENSITY)is aproximatly 600-700 Kg/m3 as opposed to White Oak which is aprox. 750 Kg/m3, remembering that Teak is 670 Kg/m3 for a mature tree and plantation material may be as low as 570 Kg/m3.ADD is rated at a 12% moisture content in the timber and the shrinkage rate will vary to different species,Bur Oak from green shrinks more than both White Oak and Teak thus its ability to "soak up water",shrinkage rate is about 4% radial and 7% tangential as compared to White Oak which is 3% radial 5% tangential and Teak which is 1.5% radial and 2.5% tangential.
I'm not sure which style, or part of a boat you wish to use this timber for, as a rule soft timbers with a lower ADD rating swell more than harder timbers thus they're more desirable for planking, but remember that harder timbers hold festners better and are generaly more rot resistant thus are more desirable for frames etc, although anti rot capibilities are prominent in softer timbers due to the presence of natural oils and resins.The amount of shrinkage timber has from green to seasoned is not always directly related to how much a member will swell in water.
Hope i've answered your question, i'm unsure weather your building a boat or buying one.