Warren's Build Log, CAN 573

[admin]

Way to move forward! I built a lot of my keel first too, although at this point I'm sort of moving backwards....

ugly keel.jpg

[Warren Nethercote]

Thinking ahead, waaaay ahead, I was speculating that I might have a reasonable number of Harken bits buried in my spares box. (I was also thinking of a PHRF boat that I sail on that could use a donation or two in the block department.) Reasonable number indeed: some were still wrapped! I won't mention or show the large number of ugly, plain bearing blocks (tufnol even) or cleats of various descriptions. What does your spares box look like? It is worth an exploration.

[Warren Nethercote]

More of the same, but different ....

Starting the keel next, with the aim of getting two-part finishes on it before the heating season forces me to close up the workshop windows. A Cedar core like the rudder, but this time with a glassfibre batten glued into a slot to permit a sharp, but robust trailing edge. Next, a sharp plane and lots of shavings. I could start by hogging off some material with the table saw or a router to reduce planing effort, but I seem to have become sensitized to cedar sawdust. But I do admit to satisfaction in seeing the shavings curl away ...

[Warren Nethercote]

Sidebar:

Some years ago there was a motorboat fire on the BBYC marina and the motorboat's finger-mate, a 40 odd foot, carbon-composite Farr racer, was written off, after the outer laminate of the cored topside blistered, as did the Hall carbon spar. A friend of mine bought the write-off, and rather than scrapping it for parts he rebuilt it, including the spar. He's done now, and offered up 3 gallons of West 105 and two containers of West 209 that he didn't use for $300CAD (about $225US). I was first to his door...

Thanks to Bruce for excellent pricing. I haven't used 209 hardener before, but Bruce remarked that it was good for 'big mixes' where heat of reaction would sometimes make even slow hardener kick off 'in the can'.

[admin]

Man, what a deal. Yeah, there were definitely times when I could have used some 209. Few things worse than holding a smoldering container of cooking-off pox!

[Warren Nethercote]

Continuing pillar to post .... time lost to judging, although some might say that 10 days in Cartagena isn't too painful. Just don't forget the antibiotics for travellers tummy. Some attempted ice-boating too (after returning home of course), but after 4,000 km of driving it was a bust. That's the nature of the sport.

I started on a building form and in its incomplete state it was a good platform for cutting so I got on with it, instead of getting frames NC cut. Seeing progress, however limited, is much more satisfying than planning.

[Warren Nethercote]

Christmas Eve is the big one around our house, so Christmas Day is rather laid back - just do your own thing while waiting for the turkey or the leftovers from Christmas Eve. I have often spread some papers on the dining room table to sketch out a design (a dinghy I once built, for example), and this morning I laid out my concept for structure forward. I'm building a PDX-style boat, and won't be sleeping on it, so ....

- I am running the cockpit sole all the way forward to Frame 18, with a step up there so Frame 18 can support the prod tube
- but keeping the foredeck to be class legal
- and cutting a hole in the foredeck for a spinnaker launcher.

I will have a fixed (non-slewing) prod, for simplicity, and in fear of conflict with the under-deck spinnaker sock.

The actual layout is being done full-scale on the frames, which will be assembled upside-down, for a conventional build. More to follow ...

[Warren Nethercote]

And here are the frames corresponding to the sketch in the preceding post .... The layout does NOT represent a body plan because the frames are aligned along the centreline and cockpit sole, not the centreline and baseline. Alignment is not perfect, but even so there is evidence of some need for fairing once the jig is set up. Note that Frame 18 has not been completely cut out above the cockpit sole level. That awaits deciding how to locate the prod.

I have a some concern about deck camber: Frames 110 and 89 have the same camber, but 56.5 (Edit: per Loh's subsequent post, Frame 53.5) and 18 have progressively tighter radii, so here's hoping that deck camber approximates a transition from cylindrical to conical development forward of frame 89, although I suspect that with 6mm plywood, brute force would prevail.

[lohwaikin]

Hi Warren,

It's frame 53.5, did you just wrote frame 56.5?

I interpreted "fair curve" as a "parabolic" curvature produced by bending a uniform batten (I used a slim aluminum extrusion) through 3 plainly-supported points.
So the plywood's bending resistance is felt most at the middle of the curve. Bending resistance diminishes on both ends, though not zero.

However, if we are to interpret fair curve as a regular arc, then I supposed the plywood's bending resistance will be constant from one end to the other.

I'm none the wiser which one is better. But now looking at the frame drawings for A5 & A6 versions (no cabin versions), that's some serious deck camber to overcome.

I really miss those days (well actually nights) of lofting, cutting and stitching plywood. And epoxy filleting!

Cheers,

[Warren Nethercote]

Hi Loh,

Yes I 'mis-spoke' when it came to frame numbering!

Fair curve can be any number of things. When laying out the curves for the hull side and bottom cambers I used wooden battens and three old-fashioned lead drafting weights. I located the end weights at the ends of the curve which, as you note, leads to a flatter curvature towards the end of the curve. This is not as attractive as a curve running beyond the end boundaries of the line, to get more uniform curvature along the line's length, but it represents what will happen to the plywood which has minimal bending moments on its boundaries.

For the deck crown I initially used a longer batten and drafting weights again, but didn't like the appearance, so I reverted to the old ship drafting technique of dividing the radius and quarter circumference of a circle of the same radius as the deck crown into quarters and then connecting the quarter points (I can attach a sketch if needed). But that gave too much curvature towards the ends of the curve, so I used those offsets only at the centreline, and at 1/8th and 1/4 of breadth points from the centreline, and let the batten run freely towards the gunwale, to approximate the moment-free plywood edge. This gave me better port-starboard symmetry and something that looks reasonable. How easy it will be to lay (sic) 6mm plywood over this curvature remains to be seen!

[Warren Nethercote]

Progress, or at least some progress between the iceboating distractions and 'honey-doos'.

I have some nice clear spruce left over from my last iceboat build and am using it for doublers on the frames, since I will be building over a form, rather than inserting frames later, stitch-and-glue fashion. I hope I have enough to do all the frames, because my source no longer retails, and what I have has been in my shop for 3 years now, so it is quite dry and stable.

[Warren Nethercote]

I had a friend around last night to help with the preliminary glue-up of my I-beam mast support structure on frame 89. I was glad of the extra hands, and didn't begrudge the expenditure of beer! More work yet to do, but after frame 89 is tidied up I can start setting up frames on the building form.

[admin]

Interesting solution to the challenge, Warren!

[Warren Nethercote]

Yes, I struggled a bit with a solution until I remembered the Australian un-decked boat in the build log section. I've since added some fillets, 17 oz biaxial tape and a layer of 11 or 12oz carbon fiber uni to stiffen the web. Probably overkill, but looks cool, if you don't look closely.

Now something of a hiatus while five of us head off to parts west for the DN Gold Cup and North American championships. Typical DN regatta: set off at 0800 tomorrow without site confirmation until tomorrow night at the earliest. But it will likely be in Wisconsin so we must get moving.

[admin]

Excellent! I hope you find perfect ice when you get there, wherever it is

[Warren Nethercote]

Back in the saddle after iceboating - first job was to glue up the deck penetration flange for the mast support, again in the style of the undecked Aussie boat. With all those picky pieces and slots, the best Christmas present I ever gave my wife was a scroll saw!

The iceboating was a bit of a mystery tour. We set off from Nova Scotia for parts west, with Wisconsin experiencing +8C temperatures and rain. En route we sailed on Bay of Quinte (Trenton, Ontario), in case it needed to be used as an alternate site. Then we set off west again, and turned right at Flint because Red Cliff on Lake Superior had promising black ice - but lost the gamble because access to the black ice pan wasn't safe. But I got to see the Mackinac bridge for the first time. We ended up in Madison WI on 14 inches of hard black ice with soft white spots, but had the Worlds cut short after one day of racing, then one day of calm, followed by snow. We sat about for a day and a half while ice checkers searched for a new venue and ended up on Green Bay, WI, on 16 inches of hard white ice. There was no concern over ice strength there - the windward mark 'boat' was a Suburban! We got the North Americans in as a full 7 race series and then set off for home via Sault Ste Marie and the northern Trans Canada highway. The only excitement on the return trip was the gas jocky who attempted to fill my Diesel Colorado with gasoline. 6400 km of driving, but it was worth the joy of racing in big fleets, whatever my (mediocre) results!

(FYI, for the observant. DNs are not a World sailing affiliated class, so we never converted to the Olympic -TV-oriented three digit country codes. USA is just US, Poland is P, Canada is still KC, etc, etc. You will also note that for big fleets - only the starboard half of the line is shown here, the starting line is just that - a 1500 ft polyprop line with numbered starting position tags every 32 feet.)

[Warren Nethercote]

Multi-tasking ....

I was taken by the way Chad assembled his keel-box against frame 110, but the picture I saved was his last step - the boat builder's equivalent of the math text saying 'the proof is left for the reader'. But I 'figgered her out'. Build a tray of sorts, shown here with the upper end left long for the moment. More filleting and biaxial glass tape to come before I can glue both it and the other 'tray' to frame 110, like Chad, to make a keel box. Then start erecting frames on the build form.

Speaking of Chad again - he kindly sent me a digital file of his chain plate cant frame, but I ended up cutting my other frames manually. I initially got a local guy to print the cant frame on paper, but it was a dimensional instability disaster. Today I picked up a full size print on film, and like everything else I've (manually) modified the frame to be a complete ring. With all the changes I've gone chicken about going straight to 6mm BS1088 with this one and will make a pattern out of some cruddy 3mm Meranti I have laying about. (The diagonal line on the drawing is a check dimension to ensure that the film is dimensionally stable.)

[Warren Nethercote]

One more down .....

I assembled my keel box rather like Chad's, by first building trays with the keel box sides and then gluing them to Frame 110. I differed in that I did not leave the keel box long ('high') , but finished it to frame height, minus 6mm doubler plates top and bottom to increase gluing area for this high-load area of the boat. The bottom doubler also includes a 6mm plug in the bottom of the keel box so the bottom of the boat will be 18mm thick where the keel penetrates it.

I am toying with the idea of gluing Frame 124 to this assembly - rather like creating a shipbuilding 'unit', but if Frame 124 ends up out of plane, or worse yet twisted on the longitudinal axis, I will be in trouble!

[Warren Nethercote]

On plywood ....

I was just about to set up frames when I realized that it would be easier to scarf and cut out side and bottom panels using the building form frame as a base. I popped out to my plywood source to find that they were out of Joubert BS1088 and now stocked a Spanish-produced plywood. Mixed reviews from this guy: denser, shorter grain so harder to scarf with a hand plane, and not as flat to boot. I guess you gotta use what you're given.

Cut out the bottom panel, but need to troll Chad's build log again. I recall him reporting that the side panels were a smidgen narrow when he added them after the framing. If that memory is confirmed I will add appropriate extra width to the sides when I cut them out.

Of course, no solution is without its own problems: what am I going to do with three 18 and a bit foot long panels while setting up frames?

[Warren Nethercote]

Found the relevant bit in Chad's log (photo below). If the gap is continuous, looks like adding about 6mm to side panel offsets at the sheer line would do it. Chad?

[Warren Nethercote]

In Chad's own words in another post:

"I found that the frames held the deck about 1/4" above the hull sides through the entire middle of the boat. So the hull sides didn't quite reach the frame corners at the top. The frame curves were added to the plan, but the hull side shape has never been adjusted to account for this. I think this gap is the result, but it's a pretty minor issue if you have a sheer clamp and just plane it to a fair curve hitting the frame tops, then fill the little 1/4" x 1/4" gap above the hull panel. Then radius the edge and most of the gap gets cut away, anyway."

Edit: So what I did was lay out the side panel per the plans, then add 3mm at sheer and chine for the middle few stations, 2mm for a couple after that, and washed it out to nothing added at the ends. I did check the panel widths at stem and transom against 'as-produced' measurements for the stem and frame 214, which were OK. The resulting offsets easily took a long batten to draw the cutting lines. One more to go, but my knees could use a rest.

[Warren Nethercote]

In many of the ex-brit dominions the fiscal year starts April 1st, and so new projects often start then. For me, assembly begins ....

[Warren Nethercote]

No free lunch ...

Adding the mast support structure to frame 89 and the keel box structure to Frame 110 saved time with subassemblies, but made erection on the building form a PITA! It could have been worse: I might have listened to my enthusiasms and glued frame 124 to the keel box earlier in the process. As it was I had to add the frame 124 supports after it was glued to the keel box. It would have been an absolute stinker to set up a full subassembly of frame 110, frame 124 AND the keel box. After that, progress is a bit easier.

As an aside, my earlier concerns about maintaining axial alignment of Frames 110 and 124 through the keel box were unfounded. That bit was straight forward.

[Warren Nethercote]

Got the last of the frames installed today, although a test with some battens suggests that I didn't quite get 169 1/2 right. The batten sits about 3/8 inch above the frame. Experience says "if the batten isn't fair, the boat isn't either." Need to investigate ....

I haven't installed the stem yet and Chad's drawing doesn't help there. But Leon, who built PhattAss upside down provides hints in his build log on Facebook. I will follow suit.

[Warren Nethercote]

Sometimes your decisions get taken away from you.

I have been thinking ahead: "Will I install the bottom or side skins first?" I am not there yet, as I am installing longitudinal members (stringers, chine logs, etc). I decided to laminate the chine and sheer stringers, just because. But after the clamps came off the first chine it was apparent that while it was fair in profile, it had gone a bit flat in plan view forward and aft of Frame 169.5. Grrrr. So the bottom will go on first. That way I can stabilize the chine log and add and fair a thin lamination of spruce to the outside of the chine log forward and aft of frame 169.5 so that the sides don't go on with flat-looking bits on the after side shell.

Sometimes, upside-right stitch and glue building looks attractive ....