Monday, January 21, 2013

Puzzle Pieces



“I don’t know how to do that. But I will figure it out and get back to you.”

This is my favorite part about working at Rockport Marine; I utter these words or similar almost every day. “Figuring it out” could take a couple of minutes, or it might take an entire day. It doesn’t really matter—either way it’s an enjoyable, challenging and rewarding way to spend your day.

At its core, design is puzzles and problem solving. The puzzles we have at Rockport Marine tend to be large, with a gajillion pieces ranging from new to beyond repair. There are pieces missing and there are extra pieces. Some of the pieces you will need are available in a catalog. Some you will have to invent and manufacture yourself. They are expected to fit together perfectly into a finished assembly whose physical beauty, quality of craftsmanship, elegance of engineering, and prowess under sail or power will inspire all who step aboard. Oh, I almost forgot. It should also last forever. Or maybe almost forever. Some of our grandkids might pursue this line of work and it is probably okay if a few things need fixing by then.

Rockport Marine is a busy place. So there are always puzzles in abundance. We don’t see most of them in the design office because they get solved by the crew and the project managers every day. The solutions take the form of ingenious jigs, and tools improvised or invented that increase the accuracy, efficiency, or otherwise improve the execution of the task at hand. I’d be surprised if we see 1% of the puzzles, but they tend to be good ones so I thought I might share a few.



The puzzles I’ve been seeing most recently have come from John England. John and his crew are roughly a third of the way through the new Friendship 36 from the design office of the Fontaine Design Group.



John will walk in and say, “just to give you a heads up, I’ve been thinking about ______ and I may want you to draw something up.” John’s is as good as it gets when it comes to boat construction and restoration. He’s fast, efficient, and exacting as a boatbuilder and a project manager. He’s also been building boats professionally for about as long as I have been alive. So when he comes in with a puzzle it’s bound to be a good one or he would have solved it already. More often than not, he has a solution that just doesn’t feel like the best solution. The quality of the solutions we come up with is measured by the answers to some pretty basic questions. Is it simple to understand, manufacture, and operate? If you dunk it in salt water, and then alternately ignore it and abuse it will it still be working in 50 years? Is it elegant?


John and his crew are working to an aggressive timetable on this project so we were looking for ways to improve efficiency from the start. One of the challenges associated with working on smaller boats is that you can’t throw people at a time crunch. The darn thing just isn’t big enough fit a dozen people side by side. This puzzle was about how to speed things up a little, and the answer is actually a puzzle itself. We’re going to build the entire cockpit assembly off of the boat. Done properly it should allow us to take the cockpit through to a high level of completion while leaving open access to that portion of the hull adjacent the engine for installation of mechanical systems. When the time comes the finished cockpit will be lowered into place. There shouldn’t be too much left to do other than attaching some hoses to the gutter and footwell drains and running the electrical and electronic cable to the navigation instruments and throttle shifter. There’s nothing especially new or innovative about this technique of building components off the boat to a high level of completion and then installing them in the boat. Production boatbuilders employ this technique regularly and the interiors of the largest custom yachts are frequently installed into the hulls essentially complete, save plumbing and electrical connections.

In our case it meant developing a relatively elaborate mold to capture the geometric complexity of the finished cockpit. Working to the geometry from Fontaine Design Group and in collaboration with Gardner Pickering of Hewes & Company in Blue Hill, Maine, we prepared a 3D model of the mold assembly.

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Gardner and his team nested the shapes for efficient use of material and then cut them with computer numerically controlled equipment. We received a stack of shapes cut from birch plywood. Rockport Marine boatbuilder Greg Pugh reports that they went together in just a few minutes a little like those jigsaw dinosaur skeletons you might have made as a kid. Tab A into Slot B, that kind of thing. 


Many of the bevels were cut by machine. Those that weren’t were cut to the large side and scribed with the cutter head on the small side to facilitate finishing the bevels by hand. Here’s what it looks like: 




We will find out whether this solution is as clever as we think it is when the builders are little farther along and in a position to render judgment, but things are looking good so far.


Reverse the Purchase

I did a quick internet search to try to find out when we first started to see reverse purchase main sheet systems on sailboats but came up with nothing definitive. I’m going to guess that this innovation appeared 8-10 years ago. Have you ever noticed how a main sheet these days seems to be a single line that disappears into the boom on one end or through the deck on the other? No blocks or purchase cluttering up the deck, just clean and simple… Well sort of. As with many modern gadgets I’m not sure this particular innovation has eliminated complexity. What it has done is remove it from view.

Note the simplicity of the main sheet arrangement on this Friendship 40.


If it sounds like I’m not entirely sold on the concept it’s because I’m still unsure how I feel about it. I am certain that I should reserve judgment until I have some more experience with them. Reverse purchase main sheets have been around for a while now and have established a reliable track record of relatively trouble free service. You have to admit they do look pretty slick. Clean and spare decks is a goal worth pursuing both from an aesthetic and functional standpoint, and these reverse purchase main sheet systems definitely achieve that.

I guess I have am still reluctant to take a dead simple, idiot proof thing like a main sheet (rope, blocks, cleat or winch if necessary) and exchange it for the complexity of a hydraulic cylinder that is then hidden from view below decks or in the boom. But in the age old battle between simplicity and creature comfort I would say things are trending in favor of the latter. Certainly if you start from the viewpoint that clients expect push button convenience in the main sheet system, well the system starts to make a lot of sense.

And people do love these things. They love the way they look. If they are more costly and complicated, well at least they seem to work reliably, consistently, and well. And every puzzle has parameters you have to honor. The only ones we won’t attempt are the ones that can’t be solved safely, without danger to life and limb. Push button sheeting hardly falls into that category. If a reverse purchase main sheet is called for than we’ll configure the best one we know how. For those of you that like solutions, here’s one way to do it.

Dead end on the boom: There are reverse purchase systems that dead end the sheet on deck and fit the purchase system in the cavity of a hollow boom. Harken even makes an in-boom, electric-powered version. It seems to me that the point of this thing is for it to look great, and therefore eliminating the hardware on deck is a bigger visual improvement than eliminating hardware on the end of the boom.

Fairlead through the deck: The deck will want a smooth ring like a miniature version of this hawse pipe. It need only be large enough to pass the sheet but should be well radiused to eliminate chafe when the sheet deflects forward sailing off the wind.


Turn, turn, turn: The below deck sheaves are fairly easy to install, although the first one will need to be in a box of some kind to collect and drain water that comes through the deck penetration. All of the major modern block manufacturers manufacture what are commonly called foot blocks. Here is a particularly attractive 100mm stainless steel version available from Harken, but as these are all below decks, the anodized aluminum really ought to suffice. Just be sure to match the working load to the loads in the system.


images courtesy of Harken

The first turning sheave leads the sheet outboard and the second redirects fore and aft where there is room to accommodate the purchase system and the full throw of the hydraulic ram. The purchase in the system is achieved via the foot blocks above and a specialized sort of a fiddle block that threads directly on to the end of the hydraulic rod.

Image courtesy of Harken


So the main sheet dead ends on a cleat effectively affixed to the underside of this rod end fiddle block. From here the sheet leads around the first sheave of the double foot block, to the first sheave on the rod end fiddle, to the second sheave of the double, back to the second sheave on the rod end fiddle, to the single foot block, to the turning sheave on centerline, up through the fairlead, and dead ends on the boom. All together it looks like this:




Still, it is one solution to the puzzle of making a mainsheet look simpler than it actually is. 

-Brendan Riordan

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1 Comments:

At June 9, 2017 at 8:11 AM , Blogger best content writing services said...

It is a very informative post for the designers of the boats and ships. You have shared detailed drafts of the construction which would make it easy to make the drafts and make changes in them.

 

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