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

Friday, November 8, 2019

Travelling OffCenterBoards (aka LeeBoards)

OCB in forward, sailing position
(Photo from Pete Frost)

OCB in aft, stowed position
Windows clear!
(Photo from John Herschenrider)

Truly, she doth block a staircase!
-- From 
by Wallace Tripp


Travelling OffCenterBoards (aka LeeBoards)

Let's start with a leeboard.

As we sail into the wind with our leeboard down (on the lee side), the leeway we make presses it against the hull. It likes to slip forward but not sideways (LR for Lateral Resistance), so we don't make as much leeway as we would without it.

Ready about!

Helm down, we turn into the wind, sails flogging as the bow and boom cross the wind. We drop the leeboard on the new leeward side and raise the first one clear of the water. Sails fill, we heel over and off we go on the new tack.

If it sounds like allemande left and dosido, it is. A little choreography on what may be a heaving, wet deck and your partner is a big, heavy leeboard.

Lazy sailors that we be, our interest was aroused by Ida Little as she clamped a 2x2 outboard of her Bolger DUGONG's leeboards to form a slot, instantly converting them to OCBs (Off Center Boards).

No need to tend 'em between tacks! Just put 'em down and leave 'em. If you want to reduce drag sailing off the wind (no need for lateral resistance), you can raise 'em if you want to.

Years went by, and we transitioned to big view side windows. Problem is, with the boards raised (always the case at anchor), they block our view.

We wanted to haul and store them out of the way. We wanted a simple installation. We wanted it quickly and easily handled by one person.

So we scratched our heads and came up with travelling OCBs.


*****

Walk-through of set and stow
Please watch first for overview

The video above walks through from stowed aft to set forward and back. Notice that the stowed position is in the 'blind spot' below the pilot house.


Tour of system components:

Upper cable, eve guard and stop

This is one of our early prototype stops for the board. It's two purposes are to act as a stop at one of the board's two positions, and to shorten the span of the cable.

The traveling block (description to follow) travels along the upper cable until it hits the forward stop (set) or aft stop (stow).

Both functions will eventually be met by a shorter upper cable (shorter span) and crimp on swage sleeves (stops).

In the meantime, we currently tie a double sided rolling hitch around the cable, with the ends led up to a handrail post (i.e., the vertical part, and not the grip), rather than the arrangement shown.

That aft tail is just 'cuz I hate cutting line.


Aft lower guard, mounting plate, lower cable and slot
Forward lower guard, sheathed turnbuckle, mounting plate and slot
Note the guard struts

The lower guard and lower cable - offset by mounting plates - form the slot.

The lower guard doubles as bearing for the OCBs and mounting steps fore and aft. Handy for boarding from the ground or a dock.

A rule of thumb for leeboards is to toe them in 2 degrees. This helps the vessel 'climb' to windward. We haven't done this on these lower guards, but plan to at the first opportunity.

On the lee side, the OCB acts like an ordinary leeboard. It bears up against the lower guard and pulls at the upper cable.

On the windward side, the lower cable prevents the board from winging out, and the upper board bears up on the eave guard.

We adjust cable tension to let them angle inboard, also at 2 degrees. Our thinking is that, when heeled, this produces a downward force at their Center of Effort, equivalent to someone hiking out, acting against heel. I mean, since we're leaving it down, why not?

Incidentally, since both boards remain down, we use only a little more than half the area one might in a leeboard (where one board handles all LR). This is cheaper, faster to build, lighter, and induces less stress.

There are big stresses on OCBs. I would like bigger and thicker mounting plates down the road, though these (1/4in aluminum) seem to be doing fine. I'm guessing the cables help to absorb and disperse some of the stress.


Bottom of OCB from aft

Here we see the retrieval line, its block and cleat. It is used to raise, lower and angle the board with 2 to 1 purchase (we're trying it out... may go to 3:1).

For stowing, the board is moved to the aft stop and raised clear of the water, but with its lower edge still in the slot. This prevents waves from clunking the board when stowed.

For sailing into the wind, the board is moved to the forward stop and tied, then the retrieval line is hauled in a bit to angle it back a skosh. This encourages it to kick back if we bounce it on the bottom in a swell, relieving stress all round.

For sailing off the wind, we haul the board to as near horizontal as possible. This reduces drag from the now useless boards (lateral resistance is not required off the wind).

Due to the relatively poor lead for the retrieval line, while deployed, we can't quite clear the water with the OCBs' lower edges. We're considering a snatch hook under the eave directly above the load... this would improve the lead, but requires awkward handling with low payoff. Still mulling that one over.

Note the upper mounting plates which were cut from aluminum angle.



Top of OCB from Inboard

These two pics show the hanging / travelling arrangement for the OCBs.

As seen above, an inverted block runs its sheave above and along the upper cable. A lanyard is fixed to the block, and passed through the board to the outboard face. The board pivots from the block when raising and lowering.

[NOTE: We've found Stanley™ Pulleys to be perfect for the job... cheap, strong enough, and the sheave pin is R-sprung for easy dis/mounting.]

Below, we see the lanyard emerge and tie off to a cleat. We pull the block as snug as possible, inboard to set the board as high as possible. This gives good landing on the eave guard. The eave has the dual function of bearing against the upper board, and keeping deck runoff from the windows.

The tail of the lanyard - stopper knotted at its end - is used to haul the boards fore and aft. In the forward position, we tie off to the handrail with a clove hitch to keep the board from pulling aft when raised in place for off-wind sailing.


Top of OCB from Outboard


A little miscellany... 

There are two main criticisms of OCB/leeboards; clunking and picking up 'scultch' (seaweed Klingons).

We've only had board clunking issues in light winds and riptide conditions. Otherwise, the boards either immediately bear up and go silent or 'shuffle' along in no wind. In LUNA, we added firehose along the lower guard, which eliminated clunking, but it's seems only vaguely worthwhile.

We do pick up weed now an then, but it's easily dislodged by raising the board briefly.

As a frequent criticism of OCB/leeboards, I don't get it. Any LR device picks weed, and in most it's a LOT harder to ditch. I see plenty of fixed keelers dragging a garland.

OCBs are easy to construct and maintain, requiring no hull apertures or complex structures. Ventilation is most excellent!

Maintenance is a relative snap. To dismount, we uncleat the lanyard, which can then lower the board with 2:1 purchase. We temporarily hang the board by its cleat's lower horn hooked over the lower cable. We can leave it like that until ready to remount or take it ashore.

We shoot for a ballast load that floats them vertically, about a foot or so proud of the water when dismounted. We can easily tow them ashore on a 'leash' for whatever. Propped up flat, they make a great work bench, ashore.

We don't always sail with both boards down. Each significantly reduces leeway, but there are days we just don't need to be sailing at our best to windward (e.g., a short leg after a long run). In case we change our mind, the second is easy enough to set up, underway. If not, that much less to put away at the end of a pleasant sail.

Retractable LR is a given for ultra-shoal draft. It opens up a hundred sheltered spots for every reasonably deep anchorage. When the wind come on, it can save hours to the next hidey-hole.


*****

We've been sailing with OCBs, now, for 20 years, and travelling OCBs for about half of that. We sail year round in SE Alaska most years, across a considerable range of wind, weather and water.

I'd say it's working!




[NOTE: In SLACKTIDE we had windows along the entire cabin. To stow, we had to lift the boards clear of the slot and slide them dead aft. This complicated retrieval to brute force. Lighter boards are recommended.

There's a primitive ancestor of this post on SLACKTIDE's system, here.]

Monday, November 4, 2019

Going Nowhere

Elev. ~20ft over low water

Going nowhere isn't about turning your back on the world;
It's about stepping away, now and then,
So you can see it more clearly
And love it more deeply.

-- Pico Iyer


Going Nowhere

It was a dark and stormy night...

Wait. No. It was bright and balmy day. We had turned the corner from Chatham into Peril Strait, cutting through Morris Reef as we've done a hundred times.

But this time, we were continuing the turn into Sitkoh Bay, intending to skirt the outlying reefs along the inside corner. We'd threaded the reef on the last of the rising tide, and it was now starting to fall. What's worse, it was now past top of springs (tides getting smaller for the next week and wouldn't be this high again for two weeks). Flat seas, that day, but forecast SE 20kts rising to 30kts (from the worst quarter) with seas 4 to 6ft for the next day.

We took bearings from the chart and gave ourselves some extra margin. Not enough as it turns out, and definitely given those italics above.

Anke had the good sense to think one of us should be at the bow (me saying, "Only if you like... we're well clear!"). She wasn't even all the way forward before she called out, "Hard to port!"

I duly put 'er over hard, but too late. We fetched up mid-ships against the only point in the whole durn area that could have caught us, a little 4in pinnacle standing atop a sunken hill.

In 30 years of sailing cheek on jowl with reefs, this is only the second rock I've hit. Ironically, the first was about a hundred yards away (broke my rule about running through unscoped kelp patches) and about a mile from where we spent a few memorable days on the beach.

This one was a doozy!

Initial assessment showed a couple knots of current held us pinned against that toe-stubber at about our Center of Lateral Resistance (side point around which a boat will spin... or not), so we:

  1. Tried to spin off under sail... not enough wind to overcome current.
  2. Tried to pole off... not enough strength at a steep angle.
  3. Stepped onto the rock and tried to push off by hand... we were on a peak and I couldn't step far enough away from the CLR to gain leverage.

    By now, we're starting to settle on whats showing as a small, thwartships ridge a foot aft of CLR. It's no longer just current we're fighting, but gravity.
  4. Tried levering off... ditto.
  5. Tried lever + handybilly... double ditto.
  6. Rowed out a kedge... by now, we're settled too hard to shift, even with capstan assist.
Okay. At this point, we give up on trying to get off the rock, and turn toward stabilizing ourselves on it.

Luckily, that ridge was plenty long enough to support us across the bottom. No fear of tilting and falling sideways. But, being a ridge, it was like a teeter totter with the big kid at the bow. The bow started to settle, and our stern reached for the stars.

Our first impulse and effort was to lash some fenders under the bow for a cushion. But it soon became clear that even with their extra height, we would be dangerously bow-down by the time they fetched up. At worst, we'd nose-dive down the hill and fetch up hard.

Sooo. We had plenty of firewood... we were able to post two pieces on end - one on each side, about 4ft forward of the fulcrum point, standing on the rock and shouldered under the bottom. Further settling of the bow was stopped, and we could breathe a little easier as the water ebbed away.

Fortunately, we could move freely around the boat without our weight being an issue, though we were pussy-footing, to be sure. Didn't want to shake ourselves off those posts!

We rested a bit and had a meal. What a view! The sun was getting low over two of SE Alaska's great waterways. First snows on the peaks all round. Us in the high bleachers, looking down upon it all. Warm food, coffee and time to think out a plan.

Kinda like yoga.
Doesn't really catch how high up we were!

First thing was to run the numbers. Check the tides, calculate ranges, apply the Rule of Tenths. Check it twice. Safe by a foot... we would float in the very early morning.

Next, we contacted the Coast Guard to let them know our situation (about which they would likely get some calls from passing traffic), and that we had it in hand.

We reset the kedge further out in sandy bottom, well off the port quarter (the free shot out).  Set up a snatch block for the anchor line to lead it fair (from directly forward) to the capstan. This let us use nearly its full power.

Before calling it a night, we added two more rounds of firewood lying flat, aft of the fulcrum. Our thinking was that, as the bow lifted and stern lowered, we would rotate around those, lifting up and away from the stone fulcrum. Any wave-induced pounding would be on a more forgiving surface.

Oh. And I took a sledge to that 4in pinnacle and beat it flat. If we were going to bounce in the morning, we sure didn't want it poking up at us!

Approximate line of 'our' rock...
Post and round drawn in brown.

In the wee hours, the tide duly came back, and as promised, lifted us free, aided by light chop. We waited until we were just quivering before hauling the kedge line bar taught. 

Within a few minutes, we slipped free in two lunges. No grinding, no damage.


*****

As you may have noticed, there was considerable luck involve, good and bad, as is the usual case.

If we'd been half our beam in either direction, it would have been a close call but no contact.

If we'd hit that pinnacle a few feet from CLR, we could have spun off.

If the rock had been flatter (longships), we could have spun off.

If it had been too much of a steep rock, we could have slid off either forward or sideways.

As it was, we were reminded again how forgiving ultra-shoal draft boats can be, particularly those with flat bottoms. 

We appreciate the virtues of girder construction. You can see how rigidly our stern cantilevers. The wide, flat, rigid bottom facilitated posting to limit rotation.

These two features most often mean that, even if a strong sea builds up, we can get out with little harm from a scrape like this. As the tops of the first waves lift us, the kedge pulls forward. Only a small drop and crunch are likely, and only a few of those.

All in all, however, we count our lucky stars.


*****

On Appraisal, we draw these reminders and lessons:

  • Always give extra margin on falling tides, especially falling from springs to neaps!!
  • Remember that reefs and shorelines are rarely accurately charted!

    Pilots advise traffic keep whopping distances off visible landmarks. We run reefs all the time, but when skirting need to be on full alert or follow the pilot. Extra wide margins! Lookout at the bow!
  • Set a kedge early!

    We dillied and dallied too long, partly as it was a foul spot; easy to lose an anchor. Still, anchors are cheap relative to risking the boat, so delay was a poor choice. For ultra-shoal, it's not usually the first response, but shouldn't be delayed long. It's our heavy lifter.

*****

We met thirty some years ago at the Pioneer "P" Bar in Sitka, AK. Its walls are covered with photos of boats on the rocks. Not exactly a Hall of Fame, but rather a Wall of Infamy.

We finally earned our spot!