Rethinking the Rig

Our first shot at SJR Ketch...
Looks good, but doesn't feel right

Second thoughts are ever wiser.
- Euripedes

Rethinking the Rig

In a previous post (Rig o' Morale), we introduced a variation on Slieve McGallister's SJR (Split Junk Rig), and the above ketch sailplan.

But a few points have been gnawing at me:

The mizzen (after sail) is most valuable to us as a maneuvering/weathercocking sail. Efficiency is welcome, of course, but not a prime consideration.

To leave anchor, for example, we raise mizzen, haul anchor, drift back on backed rudder and back mizzen to fall off reliably on our preferred tack, then raise main and sail off. No muss, no fuss, even with dangers close at hand. For sailing backward, again, we're backing sail and steering with rudder reversed. Occasionally, we'll leave the mizzen standing for a riding sail. We'll often drop the foresail, haul the mizzen close and drift, bow into wind of virtually any strength. This stops our headway, and eases motion for such chores as bailing the dory.

For each of these tasks, SLACKTIDE's flat-cut, low-lift, high drag mizzen has been perfect. Picturing these maneuvers with an extremely high-lift sail, with a large balance (area forward of the mast), jiblets cut full with a loose leech... well, it gives me pause. The high-lift can kick in abruptly, turning a backed sail into a driving one... a willawaw in close quarters could get tense. The large balance moves the mizzen's CE forward, reducing its positive effect aft. The jiblets are likely to flog in irons, which is hard on the sail and nerves... no problem for normal sailing, but... well... we're not normal!

If we want, therefore to go back to a good ol' unsplit, flat-cut mizzen, it reduces the balance by about 4ft, vacating considerable 'airspace' over the hull. Our sailplan is already snug, partly to avoid micro-burst surprises, and also as we don't like to handle very tall/heavy masts. So we want to fill that gap, at least to some extent.

Schooner rig (main mast at the forward end of the pilothouse) would do the trick, but the less efficient, after sail would be far bigger than it needs to be for our needs, and a relatively expensive tabernacle is required to deck-step the tall, free-standing mast. Also, the sheets sweep the cockpit (doable, but annoying), and we'd then want a driver (transom mounted sail) to improve balance, induce weather helm and take over maneuvering (more gear/handling/maintenance/expense). So we'll stick with ketch.

How to close the gap?

First way is to grow the mains'l, extending the battens from 18ft to 20ft. This is as long as one can get commercial lumber, in our parts. We generally prefer shorter battens for higher sail aspect ratio on a given height and less weather helm. But with this design's long mid-deck, we'll make the stretch.

Second, we'll reduce the mains'l balance to 25%. Slieve's first sail set in this proportion. He felt that more, up to 35% would improve performance (subsequent experiments confirmed this), and handling by reducing sheet stress. But even at 25%, the rig performed and handled well. We'll be rigging six part sheets, which will easily handle any extra sheet stress.

Another consideration is that our favored sailcloth comes in 60in width (5ft). At 25% balance, the jiblets can be made from one swathe, while the body can be made from three. Material efficiency!

 As a trade-off, this arrangement sounds reasonable to us.

The result now looks like this:

Note the mizzen slot is gone.

Since these changes, I'm breathing easier. That tight feeling I've gotten - trying to picture our first sailplan in an emergency exit, after dark in rising wind - it's gone away. Confidence is high. Without realizing it, that SJR in the aft position had been working at me.

Funny thing with design. We doesn't always know exactly what we want, or why. Things feel right, or not, and it may take a while to figure out why or why not. But it's almost always worth the effort.

And changing our minds on paper is cheap!

The Dark Side of DIY

Harboring a Drudge

I gave ya one,I gave ya two
The best that rotten ol' boat would do
Ya won't be happy til I've given' ya three
But I'll be damned if you'll get me!
From The Ways of Man by Gordon Bok


The Dark Side of DIY

I once took a battery of aptitude tests for a range of 'skills'. I confident and capable with all of these (pretty rudimentary). And being good at multiple-guess, I was breezing my way through. 

But then I came up against this one section...

Oh, I was competent, but that was the problem. So I have to admit that I cheated.

Here's the deal. I had little control over where I would eventually be assigned; I would be stuck where a) I showed 'competence' and b) they needed me.  If I scored equally well across the board, it stood to reason, that I could end up in any field in which they had a short-fall.

Here's what the aptitude test looked like:

OOCOOCOOOCOOOOOCOOOCOOOOCOCOOOOOOOCOOOCOOOOOCOCOOOOCOOOOCOO

A whole page of this! In each line, they wanted to know how many C's - a) 12, b)13, c)14 or d)15? Please mark clearly with a number 2 pencil.

My sight purpled with a vision of spending years of my life in a windowless cubicle, doing whatever task for which that aptitude would recommend me. 

The thing is, I'm good at this sort of masochistic detail, but I loathe it!

So I fudged every third-ish answer by one, one way or the other, praying that I was being random enough to evade detection. The final scores showed a satisfying dip at that aptitude... clearly, detail was by far my worst feature.

Now what, you might ask, has this got to do with boat-building?

Well... we're going to be building remote. We'll have a shot at one - maybe two - deliveries in the course of the project. Every sheet, piece of wood, stick, foamboard, nail, glop of glue, smear of paint - not to mention tools, gloves, brushes, trowels, spreaders - not to mention shed materials, generator, fuel - not to mention our daily bread (by which we do not live alone) - all this and more, more, more needs to be counted, recounted, shopped for (on-line), ordered and transportation arranged.

Design is fun. Building is fun. Sailing is outrageously fun.

But did I mention that I loathe counting it all up???

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!

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!

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:

Pros:

• 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.

Cons:

• 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:

Pros:

• 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.

Cons:

• 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!!

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!

Raising the Roof: How High Should We Go?

The foot bone connected to the leg bone,
The leg bone connected to the knee bone,
The knee bone connected to the thigh bone,
The thigh bone connected to the back bone,
The back bone connected to the neck bone,
The neck bone connected to the head bone,
Oh, hear ye the word of the Lord!
'Zekiel saw them Dry Bones', Traditional 

Raising the Roof: How High Should We Go?

We've already seen a few ergonomic considerations flash by, without much comment. 

In plan view, bunks are laid out just-so long to accommodate folks. Standard is 6ft6in, but people are getting taller. Anke's brother's height (he can use 7ft) actually influenced our design.

Seats are thus high and yea deep. Foot room requires so much. Gangways are sized to let two squeeze or waltz by.

Last few days we've been going over the complex of head room.

Sitting headroom, to be exact, which is all we're going to have in the salon (living room). Ply dimensions yield (almost) no-brainer, standing headroom, but sitting headroom is tricky.

Note, in the following, that the cabin headroom, in TriloBoats, is completely tied to the height of hull sides (with a given amount of crown (6in)) , since there is no bilge. 

We've got to balance the following elements:

• Construction Economy -- Four feet is too low for standard sitting headroom over standard seat heights, so the sides must be extended upward. The range of (our) possibilities runs from 4ft8in to 5ft sides. This determines the height to the inside corner of sides and deck.
  
  A 36ft hull is 4 1/2 sheets long (48inx8ft each). That means twice that number of strips to extend the sides upward. So nine strips. Already an ugly plywood number.
  
  We can get six, 8in strips out of a sheet, so we'd need a sheet and a half for 4ft8in sides.
  
  We can get five, 9in strips out of a sheet, so we'd need most of two sheets for 4ft9in sides.
  
  We can get four, 10in strips out of a sheet, so we'd spill into three sheets for 4ft10in sides, but with significant, odd leftovers.
  
  We can still get four, 12in strips out of a sheet, so, three sheets for 5ft, with a counter sized off-cut.
  
  But a sheet runs around $30, so, even if we can't use off-cuts, this isn't going to be a big consideration.
  
• Seat Heights  -- 18in is standard, kitchen chair height. Lets assume the cushions will compress out to that. We don't want to play with this too much. Lowering cuts into storage, under. Gotta keep tote sizes in mind, too.
  
• Crowding (Sitting) -- This is where mockups really help. If the overhead is low enough to crowd us, we slouch away from it, which is uncomfortable and downright bad for the back.
  This is one of those that can't be looked up in a book. It's subjective.
  For me, it turns out that 4ft9 sides (six inch crown) is the comfortable minimum. I'm sure I can get by with 4ft8in, but my relief is palpable when it goes up that one, measly inch.
  
• Crouching (Standing) -- This is advice paraphrased, as I recall, from
  Boatowner's Sheet Anchor: A Practical Guide to Fitting Out, Upkeep, and Alteration of the Small Yacht by CARL D. LANE.

  Don't let your sitting headroom be high enough to tempt you to stand, or soon you'll develop that hang-dog feeling.

  He's referring to the bad effects of standing just out-of-line, hunched due to inadequate standing headroom. Believe me, this is a pearl of wisdom! Better to zip in and sit, with dispatch, low headroom discouraging delay.
  
  In our case, that rules out 5ft sides... down the centerline, the 6in crown makes 5ft6in; Anke's exact height. Crowded into a crouch.
  
• Windows -- Taller the better! Furnishings push the bottom edge of the cutout to 3ft3 1/2in. The upper edge is going to be 2 1/2in from the upper corner between sides and deck (more on the whys another time). Together, the non-window portion of the sides adds up to 3ft6in.
  
  Looking at our extremes:

  4ft8in minus 3ft6in equals an opening of 1ft2in... tolerable.
  
  5ft0in minus 3ft6in equals an opening of 1ft6in... yeah, baby!
  

  Both are under the 2ft 'limit' (half a sheet of plexi-glass), beyond which waste gets expensive.
  
• Line of Sight -- Anke, standing in the galley, would like to see forward over the deck, whose height off the bottom will be side.height + deck.thickness + crown.height + window.lip.height (the height of the lower lip of the trunk cabin windows). Her height of eye is 5ft2in.
  
  Deck.thickness (2 1/4in), crown.height (6in)  and window.lip.height (1 1/2in) are known, and together they equal 9 3/4in.
  
  Now, we're going to be raising the galley sole, to lift her eyes up and over the centerline galley window lip, but the lower the better, with 8in being about max (for other reasons for later). Let's say 8in... that raises her height of eye to 5ft10in off the bottom.
  
  Again, looking at our extremes:
  
  5ft sides + 9 3/4in = 5ft9 3/4in, so her eyes clear, but barely. Has to tippy toe for a view.
  
  4ft8 sides + 9 3/4in = 5ft5 3/4in... we could even drop the sole to 6in and she'd have 2 1/4in clearance.
  
  Room to negotiate.
  
• Sheer Height -- Since the top of the off-centerboard guards will come to 2ft, the further distance to the sheer with 5ft sides is 3ft. That's a bit of a clamber. It's near my crotch height on tippy toes, but well over Anke's (2ft7in).
  
  At 4ft8in (4in lower than 5ft), Anke is in tippy toe range. Of course, with a 3/4in caprail, it's that much higher.
  
  We could add an extra, external step (especially as we age), and may have to, even if we went for the low extreme.
  
  And, if we have to add the step, any old height will do.
  
• Windage, Thermal Volume, Hull Weight, Surface Area (Cleaning and Painting) -- These guys all agree. The lower the better. 

Sooo... we've decided to procrastinate this decision. 

We're likely to settle on 4ft9in corner headroom, aka 5ft3in centerline headroom. Low as I (the tall one) find comfortable. Or 4ft10in.

But for now we're keeping it open. 

Big windows still sound good, and may make Anke's standing on tippy toe to look over the centerline worthwhile, and she could learn to resist temptation to stand in the salon. The extra work and heating involved probably won't push us over any edge. A step up over the sheer may be inevitable, anyway.

In practical terms, that means ordering one extra sheet of plywood, to cover the 5ft option.

Big whoop.