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29 January 2014

Ply Foam, Ply!

Cross Sections of Arced and Flat PFP Construction

The light is what guides you home, the warmth is what keeps you there.  

~Ellie Rodriguez

Ply Foam, Ply! Looking at Insulation

Over the years, we've come to value insulation.

Not so much to keep us warm - seems simple plywood sides, a good wood stove, long johns and sweaters are plenty for our personal comfort - but to keep condensation at bay.

Condensation occurs when warm, humid air encounters a surface which is cold, relative to the air. Thinnish, dense materials such as plywood radiate their heat away to the outer world, and provide just the kind of surface that encourages condensation. In the cool, moist climes of the Pacific Northwest, condensation is a constant companion. 

And where condensation is like irrigating the spore farm to encourage crop after crop of mildew.

Good ventilation and techniques to draw moisture from the air help, but every time the hatches open in damp weather, we refresh our moisty atmosphere. For best results, these must be backed up by insulation.

Insulation slows the conduction of heat from the interior. This means less fuel to achieve the same internal temperatures. It also means the inboard surface of insulated walls and windows stays close to the internal ambient. Humidity remains as vapor in the air, where it belongs.

Mildew and airflows play a part, too, in our decision as to how we insulate.

Insulation can be made removeable. This is cheap, quick and dirty. I'm immediately drawn to it!

One friend used foamboard cut to shape, then coated with vinyl wallpaper. The vinyl is attractive, easy to clean and removable for cleaning behind / inspection.

Another used mylarized bubblewrap sheet insulation, simply hung along the walls. The effect was surprisingly cozy, and a lit his cabin up from every direction.

In A Warm Dry Boat by Roger McAfee, he suggests hollow walls with inexpensive fiberglass batting, and conducted some shake-it-up tests that sound promising.

The problem with all these, for us, is that that humid air can flow into all of these, more or less unimpeded, merely condensing out of sight. Mildew or worse, black mold, can happily multiply until spring cleaning rolls around.

Or if one DOES impede airflow, then dryrot - another major foe - lies in wait.

I've torn enough stuff apart, around here, to have seen how nasty, fungal flows love to work into any un-bonded space, however diminutive.

A friend introduced us to SIP (Structural Insulated Panel) construction, aka PFP (ply-foam-ply) construction. In  this method, foamboard is laminated between two sheets of plywood, forming a composite devoid of airways. 

There are even fringe benifits: A PFP composite is, itself, a girder, increasing rigidity and strength. And foamboard contributes substantially toward positive buoyancy.

Since much of the framing will be dimensional, 2x stock, 1 1/2in foamboard is convenient. Total R-value comes to about 8.

We've considered three general approaches:
  1. Build the sides as a single SIP - This offers several advantages, chief among which is the ability to assemble, sheath and finish on-the-bench. But also some big drawbacks. The decisive one, for us is that each side gets to be heavier than we can handle without considerable, mechanical ingenuity.
  2. Assemble the sides from SIPped panels - This makes each sub-panel manageable, at the cost of some of the finishing advantages. Construction is complicated by framing which runs the length of the boat, spanning multiple panels... it's possible to assemble, but tricky to get right.
  3. Retrofit insulation and inboard face - This makes for vertical, tedious, but straightforward assembly, with easy-to-handle parts. It eliminates butts on the inner face. Cleats for furnishings mostly double as framing for foam and inner face, and can be lighter where not. Unlike preceding methods, it puts the heavy skin outboard, where I like it.

    It's economical of materials, as one can be (easily) selective as to what to insulate and what not. We can mix-and-match, with inexpensive doorskin (1/8in plywood, used for hollow door construction)  inside cabinetry, and 1/4 inch elsewhere, where we might want to fasten lightly into the wall. Or FRP (Fiberglass Reenforced Plastic) panel in the galley, for easy wipe-down. It takes special glue, but may be worth it.

So it looks like number three for us. 

We'll be insulating the entire interior this time, including holds (unlike SLACKTIDE). We found that even the holds condense. The forward achor well seems to be the only exception... it may condense as well, but very little, and has a high salt content.

So, having waffled away at this for weeks it looks like the following:
  • 3/4in ACX outer face
  • 1 1/2in foamboard + 2x framing of western red cedar 
  • 1/8in mahogony doorskin and 1/4in ACX
  • Waterbased contact glue for foamboard faces with Gorilla Glue around edges (gap-filling) 

So, until further notice, that's the plan!

21 January 2014

Rig o' Morale

Split Junk Rig Ketch
Rigging Approximate

Still, no one goes 'down to the sea in their proud simulators!'
From Down Periscope

Rig o' Morale

One of the downsides of sailing in SE Alaska is that its kinda lonely, cruiser-wise.

Despite numerous friends from many walks of life, our sailing friends are few and far between. One consequence is falling behind the times.

Our beloved junk rig has undergone some changes in the last couple of decades we've 'been away'.

First, Arne Kverneland's experience and writings inspired many to build camber (airfoil shape) into junk sail panels. Camber allows the ususally flat-cut junk rig - notoriously 'inefficient' to windward, though comparable to most workboats from the age of sail - to overtake the mid-range of bermudan rigged racer-cruisers.

Steve McGalliard's POPPY under SJR
Second, Slieve McGallister developed the Split Junk Rig (I'll call it SJR, from here on out). Fully cambered, it divides the fore area (called the 'balance' in junk and lug rig... the small sections are called 'jiblets' in SJR) from the main, aft area at roughly 1:2 by a narrow slot along the mast. This reduces turbulence at the mast and keeps it from cutting the camber. Some slot effect may be generated, as well.

To assess the rig, Slieve has been racing POPPY, a middle aged cruiser, against the big boys and girls of Great Britain. And finishing in the top 10% in a field of hundreds!

In other words, a sail with all the advantages of junk rig has achieved excellent windward performance!

Of course, one can't just run with a successful formula...

The rig Anke and I are likely to mount puts a crab-claw panel up top - we like its behavior as the last sail standing. The next panel down is 'transitional' purely for vanity... we like the looks. The rest drops straight down like venetian blinds. The leech has been slanted, a bit, to provide positive, aft 'stagger' (overlap) so the sheets don't foul one another.

That crab-claw serves another function... coming to a universal (rope) joint at the forward apex, the lower 'limb' acts as a strut to the yard. Normally, the pull of the halyard high on the yard would depress its forward end, spoiling sail shape. But with the strut, it's position fixed at the mast by a rope hoop, prevents it from dropping and therefore forcing the aft end up (good for sail set). This eliminates a 'yard hauling parrel' (don't ask), leaving one halyard and one sheet per sail.

Playing with someone else's genius calls for caution... we built a scale model (1:6), which works perfectly. But proof will be in the field, if anywhere. As far as I'm aware, it will be the first, full-size multi-masted rig with two SJR sails.

So we get to mount a LOT of sail on masts of manageable height, each with good bury (support). The foresail provides beautiful balance on and off the wind (without adjusting position), and the aft sail is in good position to manipulate the stern via backwinding. SJR helps fill the space over the big mid-deck without introducing long-boom weather helm.

The layout shown is a big rig totalling roughly 800ft2 (57m2). Both are extremely powerful, so we'll have a learning curve, especially since each sail generates power toward the ends of the hull. We may find ourselves accelerating into abrupt turns until we get the hang of things.

But junk rig is docile, and the large balance of both sails makes it even more so than usual. Speed generally gives good control. But we'll start slow and small, just to be sure!

And the payoff may be some true, windward sailing; not just the plodding we're used to. Our flat-cut sails have surprised more than a few folks on the water; these may astound!

Fire up them morale boosters, Matey!

14 January 2014

Schoon 'er Ketch?

Three masted junk cat schooner

Junk cat ketch

Schoon 'er Ketch?

Anke and I really like multi-masted rigs. 

Schooner, ketch or yawl all grant the engineless a range of means for balancing the vessel underway or stand-still maneuvers. In the many, tight corners we like to explore or tuck ourselves into, these abilities come in mighty handy!

Mid-cabin layouts often have a keel-stepped mast somewhat forward of amidships. This may feel salty, down below, but often means sharing the bunk with a balk of lumber who likes it in the middle. I mean, I'm a tree-hugger, and all, but...

And besides, that forward-of-mid-ships-ish position for the mast means it's CE is even more so. It's very close to the CLR and therefore has very little leverage to crank the boat around. Individual sail CEs further towards the ends of the hull are much more effective.

In this respect, a ketch or yawl beats a schooner, whose main (after) sail's CE has a short lever arm. In LUNA, we addressed this with the small 'driver' set at the aft transom... being far from the CLR, even it's small area is effective for cranking the stern one way or the other.

Note: Actually, it would have been more effective with about twice the area... it couldn't quite hold the head up when drifting, under driver alone.

T32x8 layout, showing potential mast positions (circles)

The layout we're using for the T36x8 gives us the full range of possiblities, assuming masts set in above-decks tabernacles (standard layout eliminates schooner). Note that the positions at the fore and aft decks can be stepped in timber tabernacles whose beams are strongly mounted to bulkheads.

The schooner layout presents challenges, however. The pilot house helps support an aluminum, deck mounted tabernacle, but it's a high-stress affair with larger sails. We're considering a timber tabernacle with one, over-sized, deeply buried post running down the bulkhead. It would impact the dinette seat, or we can through-bolt one from the galley side with considerable overlap. The other post would pierce the deck, but have to clear the opening cut-out between galley and salon.

Okay... comparisons then, schooner vs. ketch:

First, Anke and I are going to cross a yawl off the list. Not because it's a bad rig... but to get the sail area from one sail means a whopping big one, set on a tall mast. We prefer to handle smaller sails, smaller masts, and maintain a lower combined CE. Plus, cat yawls tend to develop wicked weather helm, a real problem in gusty, high wind areas.

Three masted cat schooner:

  • Schooners are just cool.
  • Principal sails are close if not equal in size (both smaller than equivalent ketch main).
  • Under stowed main, we get a modest cat yawl... a good heavy weather format.
  • The driver has many uses (riding sail, manipulation, can add weather-helm when desired).
  • Was handy and efficient in tight quarters on LUNA (square boat approval!).
  • Principal sails are solidly sheeted inboard (no boomkin).
  • Principal masts are located on centerline.
  • Sheets don't threaten to foul the smokehead.
  • Driver takes extra mast, step, rigging and handling.
  • Driver is less effective than ketch mizzen (aft sail).
  • Main boom is higher and harder to reach.
  • Main sheets sweep the cockpit.
  • Main tabernacle blocks some view from pilot house, and takes up mid-deckspace.
  • Main tabernacle is structurally less robust.

Cat ketch:

  • Both tabernacles solidly mounted, and buildable from inexpensive timber.
  • CE of after sail is well placed for manipulations.
  • It's boom is low and easy to reach.
  • One less mast to worry about.
  • No rig intrusion into the interior.
  • Forward view is unimpeded.
  • Main (fwd sail) is significantly larger (can't reduce and still fill 'airspace' above decks).
  • Main mast is likely taller (discuss another time).
  • Mizzen is off-center (neither critical nor optimal, in my opinions).
  • Mizzen is sheeted from outboard (boomkin... hard to reach, and vulnerable).
  • Unequal sails (meaning can't mix and match in a pinch... minor point).
  • Sheets (may) threaten to foul the smokehead (minor point).

Our conclusion is that it's a close call. 

We were  very happy with LUNA's rig. The only issue I see as important is the integrity of the mid-ships tabernacle on a larger boat (bigger sails, stiffer hull).

SLACKTIDE is a pleasure, as well. The only issue I see is that the main sail (fwd) will need to have very long boom and battens across the long mid-deck, or we leave an overlarge gap between sails.

Chances are, once we've settled on the sail planform, that will make the decision for us.

Stay tuned!!

06 January 2014

Mock Turtle Soup

Building it isn't TOO much harder
(a LOT more expensive, though).

Mock Turtle Soup: Models and Mock Ups

If a picture is worth a thousand words, I'd say a model is worth a thousand pictures. I reckon that makes a model worth a million words!

It doesn't have to be a museum piece. Building in scale is important, so you can measure directly from the model. The more detail you build in, the more you'll solve and anticipate problems ahead of time. But TriloBoats are boxes... there's not so much to figure out on that score.

Note bulkheads, deck and framing lines...
almost all layout happens on sides or bulkheads.

We used doorskin (this time) and cardboard, held together by hot melt glue. Crude, but tells us all we need to know. A couple of scale models of ourselves (and a pet or two have since materialized) to picture lines of sight and boarding issues and there ya go.

We laid out the principle (side) component landings, and window cutouts.

Next step is to start marking it up with material counts:
  • Ply Sheets -- Sides, bottom, bulkheads and transoms, decks... each gets written up in place.
  • Copper Plate and Angle -- Sides and bottom; along both chines.
  • Framing -- Chines (bottom and sheer) and nailers, bulkheads and transoms, decks.
  • Nail Counts -- Parallel to framing, one or two sides... How long? How often?
  • Surface Areas -- How much for paint, sheathing, glue?
Writing our results in place beats a list by far... we can see at a glance what we've counted, and what not. Much less likely to over or under count. A different check mark for each pass through lets us check and recheck.

And we can just sit there and stare at it!


Mock-ups are different. The trick here is to be able to get the feel of a feature in full size.

We've got a collection of chairs, tables and counters picked out that we can go to for the feel of things. We might set up a mock 'gangway' to get a feel for how tight things have become in our present state of 'middle age spread'. And maybe a (literal) fudge factor? A strip of plywood simulates the overhead.

Window height has been a big issue for us. Here, we mock up the shortest windows in prospect, in their correct location on the sides.  If these are okay, the rest is gravy.

And it's okay.

Not a bad view for below-decks in a sailboat!

About Me

My photo
Anke and I live aboard WAYWARD, our T32x8 ketch. We sail by wind, tide and muscle in the waters of mid- to northern Southeast Alaska. We try to maximize the joys of life, and minimize the chores. ........ We live between the communities of SE Alaska, but drop in to visit with friends. Lately, we've worked, every other winter, care-taking Baranof Wilderness Lodge in Warmsprings Bay. This has given us a window on Web. ........ We're working toward a subsistence lifestyle, somewhat impeded by addictions to coffee, chocolate and cheese. ........ We think TEOTWAWKI is looming, and while we won't be ready, we'd at least like comfortable seats.