Please visit our home site at www.TRILOBOATS.com.

Anke and I are building our next boat, and writing about it at ABargeInTheMaking.blogspot.com. Access to the net comes and goes, so I'll be writing in fits and spurts.

Please feel free to browse the archives, leave comments where you will and write, and I'll respond as I can.

Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Saturday, March 28, 2015

Glass House of Waffles: Looking Along a Path Not Taken

T32x8 FANCY STANDARD

This is a modified repost from abargeinthemaking.blogspot.com, where I chronicle our building of a T32x8 LUNA variant. This post goes over why we chose that type over the FANCY STANDARD version. By a whisker. Here's a look into some of our decision process.


Glass House of Waffles: Looking Along a Path Not Taken

When the tarps came up from Andy Stoner's MARY ELISABETH (T32x12), Anke and I nearly swooned from the view!


360deg View
ME is what I call a STANDARD TriloBoat design, meaning half her length being standing head-room cabin, with end curves limited to the end quarters of hull length. One long sheet wide. Sides a cross sheet and a half tall plus crown (6ft at the sheer, up to about 7ft down the centerline).

Very efficient of time and materials. Good living space to length ratio. Sedan-like aesthetics. And the windows... did I mention the windows? 


 

That upper, half sheet can be plexiglass. In a 32ft hull, the cabin is 16ft. Windows along each side are 2ft x 16ft huge! That doesn't count the smaller, end and bunk windows!

270deg View
Inspired, we designed SLACKTIDE around (almost) 2ft x 8ft windows with a 'kayak' view... sitting on the floor with generous headroom. 

And it has been wonderful!






  *****


So we were sorely tempted by a variant of T32x8 STANDARD.

The huge windows and 360deg view are attractive, as is full, standing headroom throughout the cabin. The galley and sitting room are luxuriously large (in our layout), with enough to carve out a bit - if we so desired, for other purposes. 

Quick and inexpensive construction get us going quicker, with more left in the kitty, compared to virtually any other design.

Problem to address: 


Standard 4ft side height is very efficient in terms of materials. A sheet of ply topped by a half sheet of plexiglass.

Bit it means the lower edges of windows are above eye level when seated in furnishings built on the inside of the hull (no bilge) to normal dimensions. Without some juggling, one can't enjoy most of the view from a seated position.

Andy chose to raise his dinette 10in, gaining a great, all-round view while seated at the table. 

His settee, opposite, stayed low in the hole. This worked as Andy was looking to sleep eight people on-board. The back of the low settee folded up and locked to make an upper bunk over the one at seat height.

Being greedy, Anke and I want a view from all seats.


We could raise the whole sole 10in, but that would sacrifice full standing headroom in the sitting room, and force a step up/down from the galley and to the forepeak bunk. 

But we like the bunk area to be part of the sitting room social space. Being under the foredeck, it's low already, and a 10in drop increases the isolation.

Raise dinette and settee? That leaves a full-headroom gangway between settee and dinette, with views from both. Hmm. Feet are left to dangle from the settee. A fold-up footrest could work, but on 8ft, would cramp the gangway. Boo.

Well... if we lower the bottom edge of the windows 6in it solves the eye-level problem. And it grows the windows (now 2ft6in)! 


Only draw-back (a considerable one) is that we can no longer use efficient half sheets of plexiglass. Some of the 1ft6in offcuts are usable, but it's gonna cost us. But hey, it's only money.

But OH! To sit at the table with the mornin' cup o' mud, looking round with 360deg view through those giant windows!! I'll call this variant (with lowered windows) a FANCY STANDARD.

Another consequence; the leeboardy, off-center-boards we favor are already squeezed by a standard standard (assuming blocking the view is not an option). Lowering them reduces leverage above their fulcrum, requiring tricky engineering, both of board and hull. And, when stowed, low boards can't clear the water, so clunk in any slop. 


In SLACKTIDE, we addressed the problem with traveling boards, which roll all the way aft for stowage, clear of water and windows. But they have to pull clear of the slot and they're heavy suckers! I haven't figured out a way to get sufficient but simple, traveling mechanical advantage to help (a boom works but is only so-so simple). 


As is, they're beyond Anke's strength to lift clear and stow, and it won't be long before they're beyond mine. The only options are accept boom hassle, build them lighter, and put up with blocked windows or noise at anchor.

Skegs would be our choice, but they double our draft. Only to two feet, but that's the difference between boots and hip-waders. And that extra foot would exclude us from many's the skinny and interesting perch along the high tide marks. Every now and then, it would mean the difference between skinning into shelter and not. Boo.

On the other hand, we don't have to handle them, 'specially as we age. They raise the bottom, when grounding, a foot proud of nasty rocks. Copper bottom plating can be much lighter, saving thousands of dollars. 


Hmm... there's a coupla yays to balance that boo.

One perk of the design is that, since it has flush sides (and a wet-locker arrangement that can act as a mud-room... see Getting aHead), we could build a watertight door into it. Handy for loading, and it may come to pass, as we get older, that we might want to haul ashore. Diminished agility to climb in and out of the boat would likely be a big part of that decision... a sole-level entry would come in handy.

Hmm. Hmm. Nice foredeck... 8ft square!

But the bunk has to go under it and headroom is low. There's plenty for sleeping, and enough to sit and read. But kneeling would be bad for the back (you 'vigorous couples' - as Wharram would say - will know what I mean). Could always limit the repetoire or take it elsewhere, but it breaks up the moment. Boo.


We prefer to sleep longitudinally, rocking side-to-side on (rare) rolly nights. Oriented so, the bottom curve competes with the foot of a full-length bunk. To get more length, the bunk has to stay high (can't lower it for more headroom).

We could live with a shorter bunk (but, alas! I'm 6ft). Or we could make the bow curve slightly more abrupt to clear the foot. Or lower (bigger bow transom), meaning more plunging and introducing pounding. Or we can add structure for more bunk head-room, such as a pop-up hatch, but that's kludgey, blocks the view and imposes on the foredeck.
And no storage (aside from the anchor well) forward of the bunk. Boo.

On the plus side, the big foredeck compliments the split junk ketch rig we're favoring (not shown). It's high balance (sail area forward of the mast) makes the most of that big, open space.


Turns out, after months of fiddling, we could address each of these problems to the point that they were no longer boos. But not quite yays, either.

We could sleep thwartships (easy bow curve, forepeak storage vs narrower bunk, reduced bunk lockers and book-space, and some discomfort in rolly conditions). We could extend the cabin 4ft forward (excellent bunk headroom and improved mast position vs fugly appearance and increased windows (already ample, now just expensive). The skegs... erm... not first choice but call it even.

But those windows... what would we sacrifice for those??? The windows held us in dithering limbo.


*****

What we finally decided, after months of waffling back and forth, is that - for the way we live - the fancy standard would be great in harbor vs good-but-not-great underway (draft, mostly). Great for old age vs good-but-not-great while still up-and-at-'em. Great windows vs a handful of compromises.

So, reluctantly, we decided to abandon those wonderful windows.

Boo hoo.




I could'a been a Contendah!

Monday, March 23, 2015

Form Follows Function: Comparing Bottom Profiles

Comparing two possible Triloboat hulls on the same footprint, plan and layout
Both deadflats end on bulkheads


I'm not bad, I'm just drawn that way.
- Jessica Rabbit

Form Follows Function: Comparing Bottom Profiles

Anke and I are building our new boat to the lines of the upper model shown.

It's the shape I typically draw for Triloboats - 1/4 aft + 1/2 deadflat + 1/4 bow - each given as a fraction of Length Over All (LOA).

This distribution maximizes interior volume and overall displacement, as well as rectangular storage areas. The long deadflat produces fully right angle carpentry throughout most or all of the interior, simplifying carpentry. It carries extra initial and reserve buoyancy at the ends, which dampens pitching, and makes the ends less sensitive to weight loading.

Of especial note, in this layout, the weight of the trunk cabin and contents of the large, under-the-cockpit hold (some may even have an engine in there) has more floatation in its vicinity. This allows heavier stuff to be stowed where the stowin' is good.

But it's not the slipperiest shape availbable to a box barge/scow.

The lower model shows a roll-up bow. This won't plow water when plunged into it, so doesn't slow the boat as much as the transom. If driving forward through water, the angle drawn (one among many) will develop kinetic lift. Cost is less reserve buoyancy (which helps lift the bow in short, steep seas, regardless of forward motion), and cuts some useful volume away (from, say, an anchor well).

The lower hull has had some of its underbody pared away, resulting in a hull that is easier to drive through water. Of the two, this should be the faster hull.

Its deadflat has been reduced to about 1/3 LOA (adjusted to land on bulkheads; not shown). This affects both bottom end curves, lengthening and 'easing' them. They are somewhat easier to construct, possibly avoiding the need to kerf. More importantly, they offer less resistance to the water, as it flows along the hull.

Lost volume is likely negligible, but lost displacement may cost you your collection of vintage bowling balls.

These changes drop roughly 2000lbs of displacement. Assuming all else is equal in terms of rig, gear, crew and outfit, that's 2Klbs of payload that comes out of your elective stores.

Depending on how you cruise, this might be a good trade; stuff for speed. After all, the barge/scow hullform - compared to many others - has carrying capacity to burn. It may well be that you can spare it.

Anke and I sail with a lot of food, tools, spares and books that see us through long spells between resupply. But most folks don't ask that of their boats. Instead of years, they're out for months, weeks, days or even hours. That 2Klbs is superfluous to the way their needs.

Of course, one could go to fully rockered bottom (no deadflat), and ease on down their road.

Both of these models are fairly well balanced, meaning that they should float fairly level, all things being equal. But other arrangements may not. For example, we use the upper forward and lower after end. The bow would then be buoyant, relative to the stern.

Not a problem, up to a point. In lading the vessel, we'd want to pay attention to weight distribution for trim. Heavy stuff amidships, and tending further forward than aft. Low and secured, as always, of course.

Point is, our needs lie along a spectrum. What shape we choose for our hull reflects how we see ourselves faring. And to shift the simple options of the box barge/scow isn't rocket science, but simply redrawing curves. Look at it from every angle you can think of... but you were going to do that anyway!

So, if you purchase one of our StudyPLANs - typically drawn with the higher capacity lines - please consider it but a starting point.

Remember the words of the late, great Dynamite Payson...

"If it looks like a boat, it'll pretty much act like a boat."

...and take up your pencil and play!

Saturday, March 14, 2015

Roll Yer Own: Roll-Up Bows for Boxy Boats






Traditional Junk and the Latest Thing
(SKROWL 900 by Yann Quenet)

I like the way you roll!


Roll Yer Own: Roll-Up Bows for Boxy Boats

Box barges (scows) very often have a rectangular bow transom. They're easy to build, and help provide a little extra room and buoyancy at the extreme forward end. Mostly, they ride clear of the water.

Mostly.

'Course, when they don't, they're a little like a bulldozer blade. Even if we don't feel the resistance when it hits green water (and can't say I ever have), we know it's there.

By rolling the bottom up to meet the foredeck (or top of gunnel), we can eliminate the bow transom, and smooth interactions with the water.

Triloboats can be built with all flat bottom planes, their end rise joining the deadflat at a 'knuckle'. Or they can be curved. Generally, a long deadflat shortens the end-curves, making them more abrupt than a fully rockered bottom. Thicker sheets of plywood (more efficient for building up the bottom quickly) may not be able to follow the bend unaided.

One solution is kerfing; transverse cuts through several laminates of each layer, leaving a few intact. Kerfs in each are offset from others to avoid their lining up. Once the layers are laminated together, a smooth, strong, curved structure results. See more details here and here.

Once you've given up simple bending, and started kerfing, there's no construction reason not to continue with a roll-up bow. The curve is a little more extreme, so your kerfs must be closer together and possibly deeper. But that's it!

In other words, a roll-up bow costs very little extra effort, if any, over a transom bow.
 

A few possibilities for roll-up bow profiles...
Note that curves drawn outside the original lines
ADD volume, those inside REDUCE volume.


Design-wise, there are any number of ways to arrange a roll-up bow.

Some considerations:
  • Weight distribution within the hull - Does forward weight encourage forward buoyancy?
  • Storage - Do you wish to prioritize forward volume vs other considerations?
  • Typical sailing - Do everyday considerations outweigh rarer ones?
  • Extreme conditions - Do you wish to prioritize for rare occasions vs other considerations?
  • Speed - Do you want to minimize resistance (easier entries) vs other considerations?
  • Lift - Buoyant (more volume) or kinetic (angled entry)?
  • Pounding - My theory is that pounding occurs when bow angle matches wave angle... the higher the angle, the less often it will pound, all else being equal.

Virtually any boxy, flat bottomed boat can be redesigned for a full or partially roll-up bow. Most of these considerations can be juggled to produce a bow that fits your situation.

Wanna roll one up?



PS. Anke and I chose to stay with a bow transom on our new boat... it has a short foredeck, and we wanted to maximize the anchor locker volume for a given curve, and maximize our corner post bury. But we waffled... could'a gone either way.

Saturday, March 7, 2015

Square Boats, Asian Style

Painting by Valentin A. Sokoloff
This one bears a strong resemblance to Phil Bolger's Advanced Sharpies!


Square Boats, Asian Style

Here's some eye candy that demonstrates that there's very little new, under the sun. Enjoy!


Cho-sun Sailing Barge (Scow)
Note the catwalk along the outboard sheer... 
This approach can extend side decks along trunk cabins.
Also, the bottom is rolled up to meet the sheer, replacing the Bow Transom.
This can be applied to any Triloboat, as well.

*****

Fishing Barge (Scow)
Another variation... we're seeing approximately the same shape,
but with varying Beam:Length ratios,
and relative transom widths.
Not sure what provides the Lateral Resistance for this one.

*****


Fishing Barge (Scow)?
I'm not positive, but this one may be a (side) dragger...
If so, the foresails will be sheeted flat against a beam wind,
while fishing gear set over the windward side drags the bottom.
Note the Bow Transom, raked well forward.
Note that aft, overhanging platform.

*****

Cormorant Fisher
That is to say, they use the cormorants to catch fish.
Their necks are ringed so they can't swallow...
Once they've returned to the boat, they get a 'crew share' of the fish.

*****

ASYLUM by George Davis
Not Chinese, but Sampan hull with Asian flair.

*****

Sampan Run-About
Now, doesn't this put a Tupperware Tub to shame?
Looks like another bottom, rolled to meet the sheer.
Think that guy lost his paddle?

*****

Chinese Junk by Lydia Marano

Well, not exactly square
But who's gonna quibble?


(Astute reader, Robert Goad, identified Ms. Marano's subject as one of Tom Colvin's flat-bottomed junk designs:

From the board of Tom Colvin