Considering Multihull TriloBoats

T40x20 CATAMARAN

Verrrrry interesting.... but STUPID.

-- Arte Johnson (I'm half kidding) 

Considering Multihull TriloBoats

Judging by the amount of correspondence I field on the subject, there's a fair amount of interest in multihull TriloBoats – catamarans (cats), trimarans (tris) and proas. 

Here, I'll lay out the modest benefits and considerable pitfalls I see in this approach at cruising sizes, along with an impressive example of a smaller scale project that I consider highly successful.

I warn you... this is rather dull going. Unless you're particularly interested, I'd bail.

A bit of jargon: Amas are the longitudinal 'hulls' composing a multihull. There's some variation in use about the net, but it seems a pretty generally accepted term.

NOTE: The T40x20 CATAMARAN, shown above, was a 'cartoon' made on request for relatives who'd fallen in love with Phil Bolger's DOUBLE EAGLE. It's way beyond my engineering skills to even put it out as a design, but gives a taste of a square boat approach.

I should emphasize that this approach is not our taste, in general. Anke and I would be off on a Wharram TIKI, or at least a dory-ish trimaran if we ever succumbed to the allure of polyhullery and warm waters.

Multihull Principles

The use of multiple hulls is primarily to greatly improve stability. They may follow one or a mix of two strategies:

Float the leeward ama – Its reserve displacement resists heeling moment, tending the whole to low angles of heel. Its wetted surface and resulting drag, however, slow the vessel and induce lee helm.

Hike the windward ama – Its weight, lifted at the long end of a lever arm, resists heeling moment, tending the whole to low angles of heel. Lifting up and clear of the water's surface reduces wetted surface and resulting drag, as well as hull-dynamic weather helm, optimizing speed.

Cruising catamarans favor the first strategy, while proas favor the second, as do most racing or speed maximizing craft. Trimarans mix the strategy, and tend to work with shorter lever arms.

The longer and leaner the hull(s), the faster the vessel can be. Wharrams suggest a minimum of 11:1 length to waterline beam ratio. Such hulls are easily driven to higher-than-displacement speeds. Extremely narrow hulls with very high freeboard (over low draft) are enabled by the amas, which keep them from flopping over onto their sides.

Circular hull sections are fastest, but have low lateral resistance and can't be easily built of sheet materials. Rectangular sections carry the most load (assuming equal beam and draft), and have high lateral resistance. V sections have good lateral resistance and speed, but low displacement on a given draft.

Long and narrow has ergonomic consequences. In order to have a wide enough interior to fit even a snug double berth within a fast hull, the hull quickly gets long. Flare above the waterline can help, but a platform must be placed high to take advantage, reducing its headroom. The interior is linear, in shorter hulls, with little opportunity for circular social settings below-decks.

A common solution is to live largely on top of the hull/ama(s)/deck. But this generates considerable superstructure which adds weight and windage.

A mixed strategy is often employed... low superstructure to provide headroom over the narrow hull, into which, perhaps, only feet may dangle. It may overhang the sides to help provide 'elbow-room', storage or even low headroom bunks.

Wharrams recommend a 3ft sea-riding height for bluewater cats (I take that as applying generally to multis), measured from the waterline to the underside of decks between amas.

Caveat to Multihulls vs Monohulls

Here are some for DIY builders to consider when comparing types:

For a given footprint, a multihull adds cost, complexity and engineering challenges.

You are building two to three monohulls, cross beams to join them, with one or more decks and/or superstructures over. Each of these components represents a fair chunk of the effort required by a monohull. Special challenges – like mast steps, Ackermann steering, high leverage forces throughout – make design daunting to dangerous for the amateur. Everything multiplied x multi.

In terms of square sections, things get scarier... the initial and reserve buoyancy of a slab is much higher than usual sections. Larger forces develop faster than the usual rules-of-thumb were evolved to handle.

If one joins the very few pioneers in this field, I recommend a cautious approach, backed by modelling, certified expert advice and incremental sea-trials.

The payoffs are speed(!) under sail, humongous decks and undeniably cool. For the pure of heart, able to run lightly through the world, multihulls can more than pay their way.

So, with that caveat, let's continue...

Simple Conversions: Adding Outriggers to Square Boats

Adding amas to a full-width TriloBoat designed as a cruising hull, I feel, is a losing proposition.

Triloboats and other box barges already have the highest monohull form stability possible on a given footprint (length x beam x draft).

As cruisers, box barges skim upright downwind, benefitting from shoal draft relative to their displacement (don't have to push much water aside). On the wind, they benefit from heeling by presenting a V section to the water.

A simple, multihull conversion detracts from both. The outrigger(s) add displacement and drag off the wind, and force the hull more upright on the wind. Plus, they clutter the deck, increase the beam with high windage, vulnerable bits, and – starting from the high mono-deck – don't offer usable sidedecks.

Lose-lose-lose.

Critiquing the T40x20 CATAMARAN

Let's take for granted that my T40x20 CATAMARAN can be well-engineered to be affordably and soundly built.

Even so, the two amas together total only 8ft hull beam. Displacement is roughly equivalent, then, to a T40x8 square monohull. But the monohull wouldn't require the two, inboard ama sidewalls. We'd be able to live within the T40x8, rather than on top of it, eliminating much of the superstructure with its weight and windage.

If a large living platform were the goal, converting to a barge by hulling over between amas would increase displacement by roughly 250%, and likely halve construction effort.

Box Section Approach to Multihulls

So let's look at it from the other direction. Could a 'square' multhull be worthwhile, designed from the ground up? This, to my mind, shows much more promise.

Triloboat approaches that might apply:

• Square sections
• Constant section
• Whole and even fractions of sheet materials

These are independent, and can be considered throughout the design.

We'd likely want to start with a long, slender hull, as per multihull normal, for an easily driven hull.

Square sections carry the same weight on less draft than all others. That can be useful. Their right angle chines provide good lateral resistance. They're easy to build, and interiors are easier to fit. Hull mid-bodies benefit most.

But flat bottoms forward – especially when held upright by amas – pound when slapped by the water's surface. What to do?

Fining down the bow - and maybe adding a cutwater (a sharp, faux hull bonded under the bow) - helps a lot with this. I'd consider matching the forward curves in plan and profile (TAB) for least turbulence.

I doubt the stern needs to narrow, and full width preserves precious deck space at the transom. I'd consider a very easy exit, with the bottom of the transom at or slightly above the waterline. Being a multihull, we're not going to heel much (so won't drag the transom corners), while the release wave depresses to help match the exit angle. Never actually seen this in square hull action, so needs experiment.

Constant sections – of whatever shape – naturally develop parallel longitudinal lines (such as the sheer) along the constant section. This is especially useful amidships, with superstructure planned and fit along this stretch.

Constant section amas , with shaped foam ends (where shapes get complex) and glassed over, show promise, I think, for easy construction and good performance. I'd personally favor assymetrical V sections (especially Newick plow-style), with the leeward face(s) oriented vertically for lateral resistance.

Whole and even fractions of sheet materials can be applied to hull, superstructure and decks, for economies of effort an material.

Another approach to square sections might be to rotate the square sectioned hull 45deg, for an upright V section. We'd end up with a diamond-style section resembling Superman's chest logo (variations are possible). The right-angle keel would run the entire centerline, eliminating any need for a cutwater at the bow. Downside is increased draft for the same displacement.

A Square Trimaran: (Mostly) A Success Story

Mark Meyer designed and built an upright box section trimaran at 27 feet. It is wicked fast, fun, good looking (I think) and carried his family safely across the waters of northern Southeast Alaska. He used it extensively to fish Tenakee Inlet for at least a decade.

Notably, he used square section, aluminum girders, rigidly mounted, for cross-beams. These worked very well.

His only disappointment were the flat-bottomed amas – skimming across the water they pounded hard. He added a V section cutwater toward the bow, which improved the situation, but not much. Apparently, flat-bottomed, flying amas proved to be a poor choice.

NOTE: Wharram Designs abandoned flat-bottoms for their catamarans for the same reason... the windward ama raised enough to pound badly. Nevertheless, they safely travelled far and wide.

Mark definitively proved the concept for the main hull, and new amas were in the works last I checked in. 

My personal opinion is that  square sections are a viable choice for hulls that stay immersed, especially when building quick and dirty or on a small scale. 

I, myself would opt  for other shapes in any project large enough to represent a significant investment. It seems to me that, beyond a certain point, the savings in construction effort cut into long-term multihull values.

But that's me.

*****

So there you are, dear Readers. For those of you interested in these exotic pursuits, I wish you happy doodling.

And keep me posted!

When Panic Rears It's Ugly Head

 Cartoon by Gary Larson 

The way the mind will lean under stress is strongly influenced by training.
From Frank Herbert's Dune

Don't Panic. 

Printed in large, friendly letters on the cover of The Hitchhiker's Guide to the Galaxy by Douglas Adams

When Panic Rears It's Ugly Head

Panic is one of the very worst dangers sailors face.

Panic may paralyze us. It may send us into a frenzy of useless or even detrimental action. It may benumb the mind or send it reeling.

Panic, more often than not, is a far greater danger than the conditions which invoke it. Indeed, it can strike in a total absence of danger if the situation is misread.

Panic is one of those reactions that might work sometimes toward survival for prey animals, and it may be that we humans spent a good chunk of our evolutionary childhood in panic-augmented flight.

But panic on board – whether of captain or crew – is not our friend. It can overwhelm anyone, but favors the unprepared. It's contagious and can debilitate an entire crew. At worst, those caught in its grip are a danger to themselves, the crew and the vessel.

Fortunately, we can reduce its onset with training, and break its grip with breathing and focus.We are none of us immune to panic, but neither are we its helpless victims.

Panic - and climbing out of it - is serious business, for which it is well to be prepared.


It was a dark and stormy night.

Well, not stormy, yet, but one was bearing down on us. And it was dark... that nebulous kind of dark where even silhouettes are blurred and indistinct.

We had fetched the reefbound entrance to a fjiord. Just the sort of place that wind, when it hits, funnels together and venturies itself into a rage (vent = wind + furies?). But we were ahead of it and dropped anchor close in the lee of a sheltering island.

Before we could set the anchor, however, the first lick of squall pounced on us and stripped it, blowing us back into exposed water, embayed by rock and reef, lost in blinding rain and intensified dark.

This is not as dangerous as it sounds, but calls for close sailing in tight quarters, with strong, confused winds. It was just a matter of navigating between the lighter water smudges bracketing the island, visible at either end of our tacks. Round up and stall in the blackouts. Work our way into the inky lull between them and anchor on soundings. Not an everyday occurrence, but we've practice aplenty.

Anke went forward to haul the anchor, while I raised sail, an operation that briefly fouls the deck with loops of halyard. Normally this is cleared at leisure as each sail is raised. But, with trouble close to leeward, there was no time for niceties. Sails and anchor up, we set course close-hauled, intending to tack back into our island's lee.

Anke returned to the cockpit and took the helm while I set about clearing the decks by feel. Despite the fact that I couldn't see any of the lines, by habit, I put my head down for a moment. A side gust hit, and we heeled hard and SLACKTIDE rounded toward it in a swoop, dumping power and regaining her feet.

As my head came up, I found that I'd lost my bearings. Neither wind nor the sketchy blots of black fell into a pattern I could recognize. Which way to turn and how long before burning up scant searoom? Panic clamped down hard. Heart pounding, mouth gone dry, knees weak and knocking, mind clutching wildly at any purchase within that churning darkness.

Breathe x four, and my mind began to work again. Still disoriented, but ready to do the sensible thing... ask Anke what's where.

And she soon set me straight.

Note: If we'd both been lost, an unpanicked assessment would quickly reveal standard options; heaving to or dropping anchor till bearings were regained. If we drag, we can row out another, or dredge downwind (dragging anchor acting as a drogue to keep head up; back sails to skin through breaks in the reef (clearly visible for ultra-shoal draft as patches of smoother water between breaking water). If a lee shore (no breaks), ground out and step ashore if and when we must. The first happens now and then, the latter two once or twice.

*****

Panic took me in its vice that night. It happens. And if we don't get a handle on it, it'll run us under.

So here are some tools we've found useful. While they don't all address panic itself, together they lower the odds that panic will take over. And once your mind is your own again, you're ready to take on trouble.

*****

Preparation

Take care of yourself – Dress appropriately for conditions. Get adequate rest. Eat and drink well (never alcohol, however, while at risk).

Outfit yourself – Reliable gear that works well together across real and anticipated scenarios gives you the physical basis to deal with emergencies.

Train yourself – Develop skills before you need them, and practice them in increasing conditions. If nothing else, imagine scenarios and response in detail.

Drills help immensely. But a word of caution... skills are most powerful when seen as modular – useful separately or in combination with others. Seen thus, they empower improvisation. Overfocusing on set drills can leave us unprepared when the real world deviates from the 'script'. I seen it happen!

Orient yourself – At all possible moments, know where you are. Where are your fall-backs? What is your fail-safe strategy? What is the path of least resistance?


In the Moment

Breathe! -- First thing you'll need is oxygen. Adrenalin kicks us into high gear and we start burning through O2 reserves like wildfire, and we need to up our intake.  

I like the 'fourfold breath'... enough air to supply the brain, and counting helps focus and bring me back. Consciously use feature to ease yourself down. Four quick breaths are not enough to hyperventilate or delay your recovery. But do take more if you need to. 

NOTE: I've since read of a technique use by US Navy Seals called square breathing. In 4 seconds, hold 4 seconds, out 4 seconds, hold 4 seconds. Repeat. Long story, but this helps bring O2 and CO2 into balance.

DO NOT PROCEED until panic ebbs... until you do, your actions are unlikely to be helpful and may cause harm! Our best shot is to keep with it until you have yourself in hand. Note the distinction between panic and merely being afraid. You can function with the latter.

To captains: If you allow your personal panic to persist, both ship and crew are as though rudderless. Your calm and confidence aid the crew to deal with their panic. You may have to relieve crew who cannot control their panic before it spreads lest they endanger the ship or themselves with panicked mis-actions.

TIP: If you are in the grip of panic, it may help to close your eyes for this step... this shuts out alarming visuals which, at this point, you are in no shape to process. Benefit varies from one individual to the next, however.

Assess, Address, Appraise – What are the dangers and/or damages? Options? Resources? Priorities?  What is your plan? Are your actions producing their intended effect? What must be done to remedy, if not? Don't hesitate to trade up one plan for a better one, where possible. We need to home in on effective address, pronto.

To captains: This is your responsibility. If time allows, consider consulting with knowledgeable crew. Consider staying in the moment... what came before or comes after is likely irrelevant in the crisis.

Communicate – Make sure everyone involved knows their job. If time permits, fill them in on the situation and the why of what they're told to do. This helps them deal with their panic. Help them with that process where time allows.

To crewmembers: Consider that the skipper may not have time to fully brief you. This is the time to 'put your head down' and perform each assigned task to the best of your ability. If you observe something urgent, report it, but consider that the skipper must rank that information into priorities to which you may not be privy. S/he may have you abandon your assigned task in favor of another as plans change rapidly. Resist the urge to act without instruction (at least such actions as dropping or raising sail).

Buy time – Actions which buy you time – to think, orient, improvise, etc. - can be invaluable, even when they don't directly improve your situation. Make the most of the time you've bought!


Afterwards:

Attend to the ship –  Damage assessment and control that hasn't been addressed during the emergency. Make all gear ready to run. Get to shelter, if necessary. Initiate repairs, if necessary.

Attend to the crew -- All present and accounted for? Any trauma or medical issues? Apply first aid, if necessary. Get help, if necessary.

ReAssess – What went well? Not so well? What could be improved? Has training adequately prepared each for their role? Was the ship's outfit up to snuff?

NOTE: As with any debriefing session, this is not a blame game. That someone panicked and/or was unable to to climb out from under it is not  reprehensible, but rather grounds for further training. This includes everyday and emergency seamanship AND in techniques for ending panic.

*****



Bonus Feature

In the following scene, from the movie Flight, involves a flight crew's response to mechanical failure.

I admire both the captain's expertise, and handling of the situation and crew. He is decisive and proactive in both respects. He plays a large role in keeping his crew from panic and moving toward a solution.

NOTE: This scene focuses on what happens in the cockpit but includes asides depicting physical trauma to crew in the cabin. It was 'loosely' inspired by a real life incident (Alaska Airlines flight 261) in which all passengers and crew perished).

Though ultimately unsuccessful, by not panicking, the real-life crew gave themselves and their passengers the best chance of survival. They were posthumously awarded the Airline Pilots Association Gold Medal for Heroism.

Please view with discretion.

Shadow Dollars: Assets vs Liabilities

From Albert Opoku's Life Lesson 50

Asset:      A possession which makes you money.

Liability:  A possession which loses you money.

-- Paraphrased from Rich Dad, Poor Dad by Robert Kiyosaki

Shadow Dollars: Assets vs Liabilities

Is our boat an asset or a liability? Simple question; not so simple answer.

The standard definition of a (hard) asset is any (physical) possession that stores value. We have equity in it (some portion we own). It can be liquefied, presumably by selling it at what price the market will bear, though that's a trickier aside.

Well, lessee.

We live aboard home-built, plywood boats that're kinda funny looking, have no engine, little standing headroom, little to no plumbing, low electrical production and tend to get banged up.

We don't 'work' the vessel in a commercial venture. We don't live near the kind of water-hippy communities that might barter for her. It's a buyer's market. No one will insure us, much less accept the boat as collateral for a loan (should we or a prospective buyer get crazy).

So we consider the recovery of intrinsic value (the value of its gear + scrap value of copper) to be a decent return. In other words...

Standard Asset Value of Our Vessels = Surely You're Joking!

 Even so, yes; in the standard sense our boat is likely to be an asset; just not much of one.

Yet, in terms of the more dynamic definition quoted above, value is not static but seen as flow. We should be asking, “Is our boat making or losing us money?” The thought plickens!

We maintain that our humble vessel is a money making MACHINE! It makes money for us hand-over-fist. Not in cold, hard cash, but in Shadow Dollars that exist 'off the books'.

Let's break it down by fiscal year... conservative estimates throughout (conservative, indeed, for urban Alaska):

Rent saved at $1K/mo                                                         $12,000

Utilities saved at $150/mo                                                 $   1,800

Groceries saved (forage) at 75% of $200/mo               $   1,800

Transportation at $1000/yr (2 RTs out-of-town)       $   1,000

Deck Sheathing: Alternatives to Fiberglass Fabric and Plastic Resins

What next?

Rain on the flowers,

Rain on the trees,

Rain on the rooftops,

But not on me!

 -- Mother Goose

Deck Sheathing: Alternatives to Fiberglass Fabric and Plastic Resins

Plywood decks are strong and easy to build, but not naturally waterproof. Sealers, paint and/or saturating resins help, but are relatively fragile... wear and tear from traffic soon allows water to penetrate. Sheathing is an attractive option.

Sheathing is a layer of fabric which is saturated by - and provides a matrix for - a waterproof substance which, once cured, bonds this layer to plywood, forming a composite structure.

Nowadays, a matrix of fiberglass cloth set in epoxy or polyester resin is nearly universal. For many reasons, Anke and I prefer an alternative suite of materials and techniques, which we learned about back in the day. To my mind, they are much more amenable to amateur construction, and worth considering in many applications around a home-built or modified vessel.

Current Practice

GRP (Glass Reenforced Plastic aka fiberglass) is undeniably wonderful stuff. It can take on most any shape, and be layered up into a skin which is itself structurally adequate for hull construction. But for sheathing its strength is wasted.

Pros are that the matrix is reliably waterproof and generally long-lived. There is abundant information available for its application. These resins are very versatile, and may already be in service for other tasks around the boat, spreading the costs of special tools and accessories.

Cons...

Fiberglass isn't particularly nice to work with. It tends to fray messily, and when trimmed, it often produces needley, itchy li'l hairs. Both are made worse when smeared with uncured resin. No fabric likes to make a sharp turn, but glass fabric is particularly fussy. Grinding to smooth is toxic and itchy.

The relatively hard matrix can craze or shatter under impacts, leading to delamination and requiring a wider area repair. This is of particular concern for bottom sheathing where grounding the boat is desired. Even small rocks can compromise GRP sheathing, so substantial repairs can be a seasonal chore.

Worst, glass is inelastic and plastic resins little more so... plywood expands and contracts a bit with humidity and temperature, and glass doesn't like to move with it. The result is shear forces between wood and sheathing, increasing chances of delamination. White finishes help considerably to reduce thermal movement.

Note: In this regard epoxy, which has smaller molecules, is preferable to long-chain polyester resin, and its performance is generally considered to be acceptable. Good results have also been obtained with polyester resin with good attention to surface preparation, catalyst proportions and thermal sequence). In other words, the problem aren't insurmountable in either case.

Plastic resins are toxic, exothermic chemical admixtures (can spontaneously burst into flame) involving solvents; they do best in fairly well controlled building environments and impose strict working times; they're expensive and require special tools and heaps of disposable accessories.

Acrylic Fabric, an Alternative to Glass

Acrylic fabric – often referred to as DYNEL after a former, proprietary product of Dow Corporation – is an inexpensive, soft yarn synthetic (rot proof) which wets out well, conforms well, frays only moderately, and is both elastic and highly abrasion resistant. It is often used for drag strips to protect the keels of GRP kayaks from chafe.

Acrylic has been extensively used with epoxy resin to sheath high-end plywood hulls by Reuel Parker and others. It does not contribute significantly to total strength, but that is supplied by the wood it protects (note that dry wood is much stronger than wet).

Being elastic, it moves with plywood. Crazing or shattering, when it happens at all, is limited to a local area. Shear stresses are low, so local damage is much less likely to spread, making repairs a much smaller task.

Grinding acrylic doesn't throw a cloud of glass shards, but does tend to fuzz and pill. This can be shaved, however, and if necessary, a final topcoat of pucky may be applied after grinding.

One caveat... I've read that acrylic should not be used with polyester resin. Dunno why. Our samples showed no short term problems with polyester resin, catalysts or cured resin (that is, nothing melted). In the longer term, we used acrylic/polyester for our dory chine chafe strips... they held up as well as their glass epoxy predecessors despite much poorer application conditions.

Non-PlasticResin Pucky

For many years, DIY boat builders decked with various fabrics (even burlap!) set in asphalt tar, paint and (of particular interest) lagging compounds – various latex puckies used to saturate cloth wrapping for hot water pipes. The huge advantages are economy, ease of application and water clean-up. It is also very easy to repair.

One favored product was ARABOL (now unavailable), which was essentially waterproof Elmer's Glue (both made by Borden Corporation as lagging compound). We used this with glass fabric to sheath LUNA's decks, which were still looking good at the 18 year mark. We know of one lapstrake(!) hull which was fully(!!) albeit sloppily sheathed in ARABOL/burlap to give it an extra decade of live-aboard life.

Lagging compounds tend to finish rather soft... a thumbnail can leave a dent, and a floppy block can wear a hole. Chafe protection in choice spots and prompt repairs easily keep up. 

Overall adhesion, while sufficient, is rather low. This can be an advantage when replacing as the entire matrix, once started, can be peeled away with relative ease. This makes it a good underlayer for asphalt products without commiting the underlying wood.

In WAYWARD, Anke and I are experimentally decking with acrylic plus TiteBond III. It cures to a plastic, slightly elastic sheet which is harder than lagging compound and fairly similar to epoxy/polyester. It is cheap (in bulk), very low toxicity, needn't be mixed and wears a lot of hats.

This method passed our 7 month immersion tests in salt water. It adheres to our wood (radiata pine)'s full fiber strength, so is very strongly bonded.

At present, WAYWARD's sheathed and topcoated deck has been sitting out in winter rain/freeze/thaw cycles for four months, and reports are that it's "looking good".

In a sense, we were fixing what weren't broke; we were perfectly happy with the soft deck. But TBIII certainly wears more hats than lagging compound, so we decided to take the risk for science.

You're welcome!  8)

Application of Fabric plus Water-Based Pucky

Application consists of the following steps:

1. Sweep and wet-tack for a dust-free deck
2. Lay out fabric (may be overlapped, but abutting is sufficient and smoother)
3. Wet out fabric (Yep. Water... drippy wet)
4. Paint on pucky (may thin somewhat with water, if necessary for low-drag)
5. Dry
6. If not satisfied, repeat from 3 (a bit of weave left provides texture)
7. Prime and top-coat

The first round of 1-4 is the primary adhesion step. As the water dries out of the weave, waterbourne pucky wicks (is drawn by capillary action) down into pores of the plywood substrate, creating a permeating bond interface. Subsequent layers build to coat and fill the weave.

On a warm, dry day, water evaporates quickly. If the fabric is drying ahead of you, consider keeping a water-brush on hand to refresh the wet. Without that water, wicking is reduced, and glue may not dilute and penetrate the fabric or wood surfaces for full adhesion.

At the end of the first pass, the fabric is only lightly bonded, however, and can be fairly easily torn away. It is reenforced by subsequent passes, however, and the result is firmly attached.

Consider whether to leave some weave for texture (thin matrix), or fill past the top of the weave for longevity (thick matrix). In the latter case, you might consider added texture in the topcoat.

My only semi-eddicated opinion is that green (not completely cured) layers bond better. Thus many layers can be applied in a single day. I especially like to prime over a green layer, in effect gluing the primer to the matrix. The whole seems to cure well over ensuing days (possibly even faster than the generally indicated 24 to 48 hours).

Topcoats

Most standard topcoats can be used, keeping in mind that the more elastic the matrix pucky used, the more elastic should be the topcoat.

Our preference is for flat latex housepaints (trim or porch enamels are most durable). If we leave the weave unfilled, this provides sufficient texture for good footing. If desired, SKID-NO-MORE adds ground rubber to a latex base.

Aluminumized trailer paint (ATCO SILVER SEAL is the best we've tried), applied with a short nap roller, provides great footing, and can be built up to an independently waterproof layer, especially along interior corners. It's messy, however, with lots of solvent... we've abandoned it for the most part.

Repairs

Puncture – Repair any wood damage. Patch with fabric, if necessary. Rebond as above. For small punctures, a shot of latex caulk or dribble of latex paint will do.

Abrasion – Patch, bond and topcoat. Consider a chafe patch or ropework, or eliminate the source.

Delamination – Slice the matrix to peel back. Inject latex caulk as deeply as possible. Work away from the slice to fill the blind pockets, then reverse and work toward the opening. Squeeze any excess out and smooth. Topcoat.

Repaint – We like to spot paint as the topcoat wears through to primer, and repaint fully when it gets widespread. On SLACKTIDE, that seems to be a full recoat every four or five years. We've never tried it, but I see no reason not to add pucky over paint if general re-thickening of the matrix seems advisable. In general, we try to avoid wearing down into the fabric itself... so far, no more than paint has seemed necessary.

* * * * *

Acrylic is great stuff, and useful in many places where glass fabric is structurally unnecessary. It happily works with epoxies, but also with much friendlier, water-based products.

Consider the application and what is demanded of it. Will a cheaper, easier, more benign suite of materials do the trick?

If so, why not?

A Note on Longevity

Rule of thumb on fishboats was that a lagging/burlap deck would last about 15 years. Synthetic fabrics were thought to last longer somewhat longer, perhaps to 20 years. Use and quality of application likely played a role.

Epoxy decks are generally considered to last 20 to 25 years, I've read.

The problem for comparison had been that most side-by-side data was generated by yachts vs non-epoxy workboats (which have only fairly recently 'gone over'). Even full-time cruisers don't give their decks the workouts that a fishboat takes. In addition, a mid-season epoxy repair is a non-starter for a working vessel. That being said, non-epoxy fishboat decks likely gets/got more new layers slathered on, here and there, than the yacht.

My guess is that they may be fairly comparable if traffic loads are taken into account?