Sunday 11 May 2014

More bulkheads, mast step doublers and centerboard stuff

I'm gradually working my way backwards in a reasonably methodical way.

The next logical step after bulkhead 3 was to do bulkhead 4. I deviated from plan again, making it from a single piece of 9mm ply that goes the full width of the boat. I wanted the area around the front of the centerboard case and back of the mast step as strong as possible. To do that I knocked up a couple of doublers for either side of the spine between bulkheads 3 and 4, and added tabs to the front of them that pass through bulkhead 4 and into the front of the centerboard case. This will stop the centerboard case pivoting with respect to the mast step.

Here's the detail of the join. It holds together nicely even without epoxy. I'm hoping once it's epoxied and filleted it'll be nice and strong. I'm thinking perhaps adding some unidirectional carbon tape along bulkhead 4 once things are together could also be helpful, as bulkhead 4 transfers loads from the shrouds to the centerboard and mast step, so we want it to be as stiff and strong as possible.

Bulkhead 5 is almost to plan. The only deviation is to make the side seat 20mm taller and 20mm less wide. That gives a bit more space for centerboard case stuff, and reducing the width of the seat gives me a touch more room in the cockpit - think putting a sleeping bag on the floor and sleeping in the boat. I'm thinking I might make a removable slat floor to facilitate this without getting soggy, but that's a long way down the track. Incidentally my 12.7mm trim bit makes short work of duplicating pieces - just make one then run round it to make another. Alas bulkhead 5 can't support itself until I do the floor, so for now it's just neatly packed away.

I also made the arms for bulkhead 3, again using the trim bit to duplicate. This led me to find my first stuff-up. I'd got the measurements wrong on bulkhead 3, so one vertex was out by a good 5mm. After vacillating for a little while, I just cut a new piece from 6mm ply. Took less time to actually do the work than umming and ahhing about what I was going to do. I'm sure I'll be able to recycle the old piece into other things.

I cut the side pieces for the centerboard case from 6mm ply. The rest of the centerboard case will be made from "Tasmanisn oak", which I'm told is neither Tasmanian nor oak. Indeed I believe it's also known as Victorian alpine ash, which is Victorian but isn't ash, being a eucalyptus. Anyway, it's a good middle-of-the road hardwood. reasonably strong and durable, but without the weight of jarrah, and with nice straight grain. It's readily available locally in lengths to 3m. I'm thinking this will be my go-to hardwood for the boat. I'll use it for stringers, keel plank, keelson, etc.

So here's what the spine is looking like now, assembled as best I can without actually gluing anything together (I'm waiting on my first shipment of epoxy - what is it with boat supply places taking forever to fill orders?). The astute can see my first go at bulkhead 3 leaning against the wall in the background, and the rapidly growing pile of offcuts.

Last job for the weekend is to laminate the timber for the centerboard itself. I'm using western red cedar for the majority of the centerboard, with the leading edge made from jarrah. I'm told they used jarrah for the young endeavour, which is plenty strong. In any case it's the toughest timber I know of, and I'm sure it'll help protect the centerboard from dings when I run it into rocks etc. The western red cedar is incredibly light, I'm hoping it'll be reasonably easy to shape. Once it's shaped I plan to sheath the whole thing in unidirectional carbon to give it stiffness, strength, and impact resistance.

So after two weekends and a few evening's work, I reckon I'm up to 30 hours.

1 comment:

Rik said...

Hi Suzy,
The way u r going u will have the gem done in 300 hrs. I am amazed at your neatness, perfect drawing setup, good ideas to changes of the best in the industry (JW) and relentless building drive.
I am completing a Pathinder myself. If you want to see how others struggle with what you breeze through, take a look at by blog.