The purpose of this project is to design and mass-produce kits for a floating tiny house that can sail. It combines high-tech modeling and fabrication and low-tech assembly that can be carried out DIY-style on a riverbank or a beach. This boat is a 3-bedroom with a kitchen, a sauna and a dining room. The deck is big enough to throw dance parties. It can be used as a river boat, a canal boat or even a beach house. Oh, and it's rugged and stable enough to take out on the ocean. Kits will start at around $50k (USD). The design has been tested in simulation and prototype; full-scale production will begin next year.

Tuesday, January 20, 2015

The masts

About the most cost-effective and quick way of making a mast is to use a tapered aluminum flagpole. That is what I had on HOGFISH, and it worked just fine. There the mainmast was stepped in a tabernacle, and had 4 lower shrouds (fore and aft), 2 uppers (aft only) with no spreaders, a genoa stay which went to the end of the bowsprit and a staysl stay. Taking down the mainmast, and putting it back up, was always a bit of an adventure. Getting the mast up or down was pretty much the easy part; it was rigging and unrigging the gin pole, and detaching, coiling, reattaching and tuning the standing rigging that took all the time. Plus all that coiled wire rope cluttered up the deck when the mast was down.

On QUIDNON, I intend to go with unstayed masts. The arrangement I have thought up is as follows. The tabernacle of each mast consists of a galvanized steel pipe with a bracket made of steel plate welded to the top of it. The bottom of the pipe rests in a cup cast into to the concrete bottom, in which it turns freely if you twist it hard enough. The cup has a drainage path into the bilge, to shed any water that finds itself into the pipe. After fabrication, the tabernacles are slag-blasted and hot-dip galvanized.

At the deck, the pipe goes through a precise, snug-fitting hole in a very substantial hardwood block (unvarnished teak) which is bolted through the deck and also tied into a frame made up of deck beams, knees and ribs. The pipe has a ring welded to it that rests flush against the bottom of the hardwood block, preventing the masts from falling out in case of a capsize. The ring is cupped, and there is a couple of small holes drilled through the pipe level with the upper surface of the ring, so that any water that finds its way there does not drip into the cabin but goes inside the pipe and eventually finds its way into the bilge.

The top end of the pipe has a three-sided bracket welded to it made of steel plate. The top of the bracket forms a slot which accepts the heel of the mast, allowing it to pivot.

The bottom end of the mast is fitted with a plug milled and lathed out of a block of aluminum. The part of the plug that fits inside the mast is lathed to the correct diameter and taper for a very precise fit. The mast and the plug are mated for life by driving the plug into the mast with a sledge. There is a mechanical screw holding the two together, but it's mostly there to stop people from asking questions.

The bottom of the plug (the heel) is square in cross-section, and precisely fits the slot in the bracket with which it mates with just enough room for two large fiberglass washers inserted where galvanized steel and aluminum meet whose job is to prevent them from galling together. It has holes drilled into it for two bolts. These two bolts can properly be called "Jesus bolts," because, as with the "Jesus nut" that holds helicopter rotors together, the failure of either one of them would tend to interrupt one's voyage in a serious way. These will be one-inch diameter stainless steel bolts, and keeping them tight, clean and oiled is a key bit preventive maintenance. The mast heel also has a hole drilled partway into it at a 45º angle that accepts a gin pole, which is a 1-inch diameter solid aluminum rod that has a sheave on one end. There is a short pendant threaded through the sheave. The pendant has a thimble on one end and a snap shackle on the other. Lastly, there are two rings welded to the tabernacle pipe, one right below the mast, and another right above the deck. The boat will carry two gin poles, for a reason that will become clear in a moment.

The masts are erected in 12 easy steps:

1. The mast is maneuvered so that the square end of its plug sits in the slot in the tabernacle.
2. The top "Jesus bolt" is inserted and assembled with washer and nut, but not tightened.
3. The bottom "Jesus bolt" is dropped into its hole in the plug from the front but the nut is left off.
4. The gin pole is inserted into the plug, and the 4-part halyard block is attached to thimbled end of the gin pole pendant.
5. The end of the halyard is sent through a snatch block hooked onto the ring on the tabernacle right below the mast, then all the way back to the anchor winch in the pilot house.
6. The snap shackle at the other end of the gin pole pendant is attached to the ring on the tabernacle pipe right above the deck.
7. The halyard is hauled in using the anchor winch until the mast flops forward in its bracket, then cleated off. (QUIDNON's masts have forward rake.)
8. Washer and nut are threaded onto the second, lower "Jesus bolt" at this point, so that the mast doesn't come crashing down if a big wave hits once the halyard is released.
9. The halyard is released and detached from the gin pole pendant.
10. The gin pole is pulled out of the plug.
11. The "Jesus bolts" are tightened using two large box-end wrenches.
12. The happy single-hander, who has just single-handedly raised a mast without any fuss at all, does a little victory dance.

The procedure for lowering the masts is basically the reverse of the procedure for raising them, with just one additional step: once the halyard is attached and tensioned and the nut from the bottom "Jesus bolt" is removed, the tip of the mast has to be pulled aft using one of the topping lifts. Then the halyard can be paid out slowly, and the mast will come down.

Once both masts are down, the two gin poles are inserted in the holes through which the top "Jesus bolts" go. The masts rest on the gin poles, along with the sails, and are lashed down to them in a single tidy bundle. (You didn't expect the gin poles to serve just one function, now, did you?) The masts do not overhang either the bow or the stern of the boat, and do not incur any penalties in the form of increased slip fees (which are based on LOA—length overall) when QUIDNON is being used as a canal boat, with the masts down.

A mast wiring bundle comes out of a hole in each mast right above the plug, threaded through a length of hose. The hose screws onto male hose fittings on the mast and on the tabernacle. From there, the wiring runs down through the tabernacle pipe, out its bottom, and through a wiring chase cast into the bottom, then up through conduits that lead to the switch panel and the instrument panel. For lightning protection, the mast is electrically bonded to the tabernacle, and the tabernacle to the copper cladding on the bottom of the boat.

In calm conditions this operation can be managed by one person, but if there is a big sea running some extra hands may be needed to keep the mast from twisting around as it's going up. This can be done by running the topping lifts to the stern and keeping some tension on them. The other option is to simply let it twist as it likes, because once it's up it can be rotated to the desired orientation by putting one's heel against the gin pole. It's a good idea to put up the foremast before the mainmast, to eliminate the chance of the foremast banging into the mainmast and denting it as it comes up. For the same reason, when taking the masts down, the mainmast should come down first.

I would think that with this system a well-trained crew could drop sails and the masts in about 15-20 minutes, start to finish, and to put them up and get ready to sail in the same amount of time.

19 comments:

  1. How does the aft mast not overhang the back of the boat by a bunch of feet? Does it hinge mid way up too?

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  2. When it's down and bolted into the tabernacle the mainmast overhangs the transom by 20'6". When it's unbolted and slid forward, it does not overhang either the transom or the bow.

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  3. Are you planning on using one or both of the aluminum masts as your shortwave antenna? Or do you plan on doing the 'inverted V' wire antenna with twin stayed wires? It seems like the inverted V would get in your way raising and lowering the masts, but typically has better emission characteristics than the tuned quarter wave that a single mast would be. However, using the mainmast as your shortwave antenna would fit well with your 'everything has more than one purpose' principle.

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  4. The question is, how can a mast be an antenna and a lightning rod at the same time? Perhaps a better choice would be to run a few wires between the two mast-tops?

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    1. The inverted V wire setup is a better antenna than just a horizontal wire spread between masts, but if you're just listening to broadcasts it won't matter. If you want to transmit, it will matter. But yes, a mast can be both an antenna and protected from lightning at the same time, any terrestrial broadcast station has to do it anyway. However, that also not as simple as just bonding the mast to the copper bottom and running a coaxial cable up the center of the mast. Contrary to popular belief, a true and proper lightning rod isn't designed to ground out the strike to prevent damage; the energy pulse is simply to great for that to work effectively. The goal of proper lightning protection is to manage the differences in electrostatic charge between a building (or boat) and the local ground references, so that passing through the building on the way to ground is NOT the ideal electrical path. There are solid state devices that radio hams (such as myself) install between the transmitter and the antenna, whose purpose is to prevent the current from traveling through the transmitter to ground, and a separate device installed between the transmitter and it's local ground rod that introduces resistance between the two whenever the transmitter is transmitting, thus permitting the antenna to function both ways by limiting the strike risk to the time period of actual transmission. The lighting protection used by broadcasters work in a different manner, but I don't understand it, and they cost a fortune.

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    2. Technically, it's inductance (not resistance) that is between the antenna and it's ground. Most hams use these...

      http://www.iceradioproducts.com/impulse1.html

      Which constantly bleed static voltages to ground, but still permit transmission powers to about one kilowatt, within a frequency range. They will NOT protect your gear, or your boat, from a direct hit; but signicantly reduce the likelyhood of getting struck. Trees are more likely to get hit by lighting because they can develop a static difference compared to the ground around them in the wind. And ungrounded mast can do the same thing. What attracts the surge of power is a (slight) charge on the elevated object, not really it's elevation above ground. I've personally witnessed a strike hit a tree 30 feet from a much taller building.

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    3. Perhaps you can do both by using a 'spark gap' between your bonding cable (from your coppered bottom) and your mast, while electrically bridging that spark gap with one of the above static arrestors? I would assume that if the mast was actually struck, the arc will jump the spark gap just fine; while the arrestor can still reduce the odds of that occurring most of the time.

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  5. I was interested to see a mention of lightening strikes in this post. I do not have sailing experience but I have read books on sailing that say 1) that many cruisers elect not to insure their crafts or are unable to; and 2) that a lightening strike can cause catastrophic damage to sailboats or at least all of their electronics. This has always troubled me, since, in my inexperience, I would expect that a sailboat would have a high likelihood of being struck at some point. Is there any predicting how effective the mitigating factors you describe in this post will be in minimizing damage from strikes?

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  6. I've never been struck by lightning, but the theory is, lightning strikes the tallest object in the area, and sailboat masts are tall. Also, lightning always seeks the lowest-resistance path, and a grounded mast provides a lower-resistance path than an ungrounded mast, so I'll only ground one of the masts.

    As far as insurance, it's generally a rip-off. Most people in the US have to have insurance for liability, to fight off the bloodsucking American lawyers. Everywhere else "no tengo dinero, Señor" is generally good enough. Insurance against your own losses is called money.

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    1. Have you ever seen St Elmo's Fire on Hogfish? Was the mast on Hogfish grounded to the sea?

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    2. No, on HOGFISH the masts weren't grounded, and I never saw Saint Elmo's fire. I did sail through some fierce lightning storms, but nothing strange ever happened.

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  7. Dmitry, why all the h/d galvanised mild? For a once-in-long-while set of relatively small fittings, why not stainless throughout? What am I missing?

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    1. Galvanized mild steel is a lot cheaper.

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  8. How much does it cost to have custom items hot dipped? Would it be a worthwhile maintenance procedure to have them re-dipped every few years during annual dry dock (or in Quidnon's case, annual dry beaching)? Or would that process make them more expensive than stainless in the long run?

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    1. Galvanization is done just once, post-fabrication. After that it generally lasts for the life of the boat if galvanized pieces are oiled every few months or painted with epoxy paint just once.

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  9. You write of wanting to use many parts for multiple purposes. You also wish to ventilate and insulate the interior effectively. Have you considered running a very thin wall plastic pipe up the inside of the mizzen mast and using it for a counter flow heat exchanger for cabin air? It would need insulation for the lower 2/3's, which could be effectively arranged if the mast tapered. Detailing of the ducts at the lower end to be quick disconnected and/or flexible when lowering the masts, and arranging for condensation drainage from the inner (exhaust) tube would be crucial. With good detailing it could be used with the mast lowered as well. The flow could be driven by clever shaping of the intake and exhaust fittings near the mast head, and augmented when not underway in calms by PV or battery powered 12V, 4 Amp computer fans.

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    1. This is a very interesting idea. I'll have to think about it. I was thinking that the hollow boom gallows ducted down into the hull, along with the airgap between the black-painted topsides and the insulated cabin liner, would provide enough ventilation.

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  10. If you have tabs welded to the tabernacle to prevent the bolt from rotating once inserted (pieces of flat bar simulating a wrench welded to the tabernacle) then you only have to go on deck with one wrench, and you only need one hand to hold that wrench, the other can hold on to the boat. This would only be important in bad weather, but it could be very important at that time

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    1. Actually, it's even easier than that. A shallow slots milled into the front mast heel (which is a block of aluminum) would grab the head of the lower Jesus bolt, while with the top one one side of the tabernacle bracket would have a square hole milled into it, and then I'd use a carriage bolt.

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