Saturday, December 4, 2010

New Mast and Sail Grommets

I've nearly finished my new mast, this time using Australian Hoop Pine. This is from various sources, though mostly Boatcraft Pacific:

An Australian native pine. Native to the drier parts of rainforests of Queensland and Northern NSW in places that have rocky soil with lower fertility. Most of the timber that is used commercially now comes from plantations. The trees grow to 60 metres tall and can live for 450 years. The trees grow slowly and usually very straight. The first major use for the plantations was to provide replacement masts for the sailing ships, indeed a small portion of a plantation established for that purpose survives in the Brisbane suburb of Sherwood. From an ethical, sustainable point of view, Hoop Pine is streets ahead of most of its plantation-grown exotic softwood counterparts. The best is #1 Clear Grade Dressed All Round Hoop Pine (I used this). This is the finest, most defect free grade available. This specification states that knots, tight or otherwise are not permitted, sloping grain is not to exceed 1 in 5, no pith can be present, no resin pockets, or bark pockets, and it is not to have any checks. According to Bootle, "WOOD IN AUSTRALIA, Types, properties and uses", Keith R Bootle, First Published 1983, McGraw Hill; It has an Air Dry Density of about 530 kg per cubic metre and its mechanical properties are very similar to Douglas Fir (Oregon, Pseudotuga menziesii). It is very suitable for boatbuilding, is easy to work and it does glue well. It is suceptable to rot, so normal precautions need to be taken. Its only limitation is that it is not suitable for steam bending.

You can see in the picture where, as I haven't got enough clamps, I've used the clamp and tape method. Put on your clamps, tape everything up, move the clamps along, tape again, and so on...

I'm also up for some sail repairs. The top of the sail seems to have been under some pressure and I think I'll add a canvas reinforcing patch just to keep it all together. I also found some plastic grommets. There was only one packet of them left at Bunnings so I bought it and the recommended brass ones. I put the plastic ones towards the bottom of the sail and the brass ones at the top (you need more than 10 for a sail).

I bought one of those punch-and-die kits for putting in the 'brass' eyelets/grommets and found that even though they had less contact with the water being at the top, they still rusted. Obviously just a thin brass coating that the salt water can get through pretty easy. The plastic ones are less than $2.00 a pack of 10, you don't need special tools to put in place and they have already outlasted the brass ones.

Anyway, just matter of varnishing the mast, patching the sail and I'm back in the water.

1 comment:

  1. I have used Hoop Pine ply for my Starlet fuselage. Not easy to find it in aircraft grade, if at all. Seems there should be some plantations of HP also for the demand for fine aircraft wood. I will tell you how susceptible it is to steam bending in a couple of months as I have to bend my 3 ply over 90 degrees (wing leading edge). It's been done. With notable breakages if you go too fast (< week!).