5. Grainger MTB920 Trimaran built with DuraKore planking

Now that the temporary frames were all set up and secured in place, Paula and I held a long board over several frames at a time to see how a Durakore strip plank would look when screwed to the frames, just as a final check to make sure that there were going to be no humps or hollows in the finished hull due to poor temporary frame measurements or cut out.
The 9.2 Meter hull was now ready for the DuraKore planks, but the Durakore was only 2.4 meters long and too wide at 300mm.
DuraKore is a marine grade composite of Baltek end grain balsa bonded in between 2 veneers of marine Gaboon hardwood, providing strength to weight ratio far superior to any traditional method of one off construction.

My next job was to splice those 2.4M planks together to at least 10 meters or longer, and then cut those planks up into suitable strips so that as they could be edge glued and screwed to the male mould frames to form a round bilge hull, and not an obvious multi chined hull shape.
The spliced joint made (male to female) was a 1 in 12 taper cut across each of the hardwood veneers.
Effectively you end up with a tapered male edge, with the marine hardwood veneers tapered down to the edge of the balsa core.
The female joint is obviously the opposite, as the balsa core is machined out a distance equal to a 1 in 12 taper of the hardwood veneers.
I’ll explain, if the hardwood veneer is 1.5mm thick then a 1 in 12 taper will cause a tapered edge to be 1.5mm x 12 = 18mm long. Therefore the balsa removed from between the hardwood veneers will be 18mm deep.
You can see the female joint in the attached photo.
And you will now see that the matching male edge is tapered out to 18mm to accept the female edge.
This 1 in 12 taper splice produces a joint equal if not stronger than the uncut hardwood. West System sells a scarfing tool that can be attached to any Skill saw to do this machining job very easily.
I made a flat “table” area along side one side of the hull, which I could glue and join the planks together, and that they would be perfectly flat long planks (at least 10M or 11M) once the west system epoxy resin was cured. I did not want to make strips which are bent at the joints. That would also have resulted in a hump or hollow to fix up later.
The reason why I made these strips much longer than the hull, was that it is important to stagger the spliced joints. It would be a potentially weaker core if all the strip joints were aligned together.
Once I had glued up a lot of 9.2 meter x 300mm planks, I then sliced them up into approximately 50mm width strips, with a skill saw.
The photos show a pile of those durakore strips ready to be edge glued and fitted to the hull mould.

2. The Trimaran boat build shed

It was autumn and the he first job build a shed, using the cold months of winter to get the mould frames set up so that I could start using epoxy resin and fibreglass to build the boat when the seasons were warm enough to cure the resin. I planned the project around the seasons, so that I always had something that could be done. Progress could not be prevented in my plan.
We moved to Roxburgh, about 1-1/2” hours from Queenstown in the South Island of New Zealand during the summer December 1989. A lovely little town on the side of a river between two large ranges.
It was a country town, with 3000 people on the side of the Clutha River, and a 320 megawatt power station where I worked as an area operator in 1990.
During the summer the temperature can get into the high 30 degree Celsius. The following winter was the coldest on record since the second world war at a low of minus 28 degrees and never got above minus 5 for approximately 7 seven weeks.
So I definitely required a shed!!
I begged and borrowed from some locals for corrugated roofing iron, and only had to buy some 100mm x 100mm x 6M posts and battens for the roof. Begging is something you become good at as a home yacht builder.
While the locals spent their winter days inside next to the roaring fires, I was seen outside building my boat shed. My ears, nose and hands were constantly cold. I reckon they must have thought I was madly insane, they were correct. Everything was constantly white because of the cold, including the coal pile.
Once the shed was built, I had to build a strong back, to support the mould.
This is a solid frame or platform on which the temporary frames and the male mould for the main hull was to be built. The timber for this frame was 200mm x 50mm non treated pine. I concreted stumps into the ground, to provide a solid base that would not move, and built the strong back onto the stumps. This can be seen in the photo of the shed.
The most important thing I learnt from very good tradesmen when serving my time as an apprentice Fitter turner Machinist is that if you start off rough, the job will finish rough. No matter what you try and do later with a rough job it will always finish as a compromise, so always start off with as perfect a job as you can and your boat will look like the panels on a brand new car. No humps or hollows, and minimal filler.
I developed excellent skills as an apprentice and take pride in whatever I do.
I set up the strong back dead level in every direction. This was to be the birth of my Trimaran project.