Episode 24 Keel locking pin

I don't like stuff that doesn't work. The locking pin for my keel had been annoying me for some time. Its not that it did not work, but that it did not work well.

My Austral 20 has a swing keel, which pivots on a pin near the front of the keel box. I had quite an adventure un-jamming the keel, and now it swings up and down freely.

The locking pin is a big bronze rod that locks the keel in the "down" position. It is located just aft of the keel, and is inserted into a hole in the side of the keel box, when the keel is down. Theoretically, the keel is heavy enough to stay down, but there is always the worry that if the boat gets rolled more than 90 degrees, the keel could swing up, changing the centre of gravity in the boat and resulting in a full upside-down-and-can't get-upright-again experience, which is something I'd prefer to avoid.

I had noticed that I could not screw the locking pin in. Also, when I grounded the keel (gently) it bent the pin backwards by tearing out the mounting screws. The problem, I deduced, was that the socket on the far side of the keel box was misaligned or blocked. The only solution was to disassemble the locking pin assembly. This was easier said than done because of the odd assortment of corroded screws, epoxy filler and plastic mounting plates that had accrued over the years following the attentions of previous owners.

The application of a drill, hammer, old chisel, much banging and bad language eventually got the components free. These are shown in the photo below, and comprise

  • The brass pin (1/2" diameter)
  • A brass ferrule on the near side, into which the pin was inserted (1" outside socket)
  • A brass socket on the far side, in which the end of the pin rests (1" outside socket)
  • A brass blank, to cover the hole when the keel was up, and so stop water from slopping into the cabin through the open hole.
  • Assorted brass and stainless steel mounting screws, most of which were totally destroyed upon extraction


Austral 20 keel locking pin components

When I got the bronze components out, I cleaned them up with wire wool. They came up like shiny old coins, as illustrated below.

Austral 20 brass ferrule and socket for keel locking pin, before and after  cleaning with wire wool

The original design had a clever feature. The head of the pin had an indented centre, and the blank had an embossed or raised centre; one for "in" and the other for "out", so you didn't need to remove either to check if the pin was in or out.

However, the weakness was that the screw holes in the ferrule and socket were too close to the centre,  and could be easily ripped out.

My suspicions were confirmed when I finally got the socket out and found that it had been filled with putty and then epoxied over. I have no idea why, except maybe to stop a tiny drip from getting into the cabin. The result meant that the pin could not engage the socket, so it was only held on one side. Any forward force applied to the keel would push the pin backwards and, because it was only held by three screws in weak screw-holes, would rip the ferrule off its mounting, making a horrid mess of the GRP and balsa core sides to the keel box.

My solution was to make up a couple of stainless steel plates, 100 x 100mm, to reinforce the mounts, and to provide a waterproof seal (like the plates I had made for the keel pin).  The hardest part was drilling the 1" diameter holes for the ferrule and socket, because the biggest metal drill bit I had was half the required diameter. Being unwilling to spend large amounts of money for a full sized 25mm metal drill bit, I decided to stitch-drill a ring of smaller holes around the diameter, and then file then out the remainder with my needle files. This was tedious, but eventually gave me the holes I needed.

The completed assembly is shown below. I have yet to fit it to the keelbox because I need to have the keel down to get everything aligned. Getting the keel down is easiest to do when the boat is in the water, which means I will have to relaunch the boat, which should happen next weekend.

And, yes, the holes for the locking pin are above the water line. (Think about what would happen if they weren't.)

Austral 20 locking pin assembly with stainless steel plates added. The stainless steel plates will be mounted either side of the keel box.




Episode 23 Varnished handrails

It is surprising what a good sanding and varnishing can do to tired woodwork (like my handrails) that has been left to grey and peel in the sun for many years. If there is a lesson here, it is never to throw stuff away because it looks old and tired, especially wood.

(When I say "good", I am referring to a conceptual ideal, rather than my actual efforts).

My handrails certainly looked bad, as illustrated below.

Austral 20 handrails in poor condition

So, I got to work with an orbital sander and 80 grit sandpaper. The trick, I found, was to remove all the greyed wood, which showed up better after the first coat of varnish than before. This made me sand through a couple of first coats of varnish, before I got rid of all the visible grey.

Austral 20 handrails, one before sanding (at rear) and one after sanding.

I applied several coats of varnish, the first being cut with about 20% mineral turps to get good penetration into the timber. As I'd noted earlier, I applied the coats thinly, waited several hours for each coat to harden, then lightly sanded back with 120 grit sandpaper. The new is still not perfect, but is strikingly better than the old.

Of course, the new handrails fitted back nicely onto the cabin top and lined up with the bolt holes to fix them down. A small amount of FixtTech180 applied to the bolt and screw holes ensured that the cabin roof was watertight.
Austral 20 handrails after sanding and varnishing




Episode 22 Turnbuckle Straighteners

One of the problems of having a demountable mast is that it can be quite easy to bend expensive bits and pieces when raising or lowering it.

I've learned this the hard way, by bending the connections to the turnbuckles at the base of the shrouds. (The shrouds are the wires that connect the mast to the sides of the boat). The problem is that when you lower the mast, things can fold up on themselves, as illustrated in the following photo. If you are not careful to un-fold things before raising the mast and tensioning everything up, you'll get the perfect conditions to bend your shiny stainless steel connections into a horrid mess.

Austral 20 turnbuckle with mast down, showing how it can twist
One solution is to buy expensive turnbuckle covers. I'd need four at about $35 each, giving at outlay of about $140. However, I'm a skinflint, so I decided to experiment with a 1m piece of pipe insulation or lagging (25mm diameter, $4.50 per 1m length), cut into 200mm lengths, and some leftover duct tape. The 25mm diameter insulation is just the right size to fit over the turnbuckle, and is easy to slide up the shroud to give access to the turnbuckle for adjustments. They seem just rigid enough to stop the turnbuckle connections from folding back completely on each other, although they are still quite floppy. Something a little stiffer would be good, but I could not find anything suitable in the giant hardware store down the road.

The straighteners/covers should reduce the risk of bending of my shiny fittings, and there is the bonus of providing some padding, should you decide to stub your toes on them whilst walking about on deck. See below, for a saving of about $135.50, although it is somewhat agricultural and might not be as durable as the proper covers.

Gaffer tape might yield something stiffer than the duct tape, but I find that the adhesive has a habit of oozing out at the edges. Maybe I should try both.



Finally, a tip; when wrapping the duct tape around the pipe insulation, pull about 1m off the roll and lay it flat on a table top with the sticky side up. Then, roll the insulation tube onto the tape. This way, you'll stop the duct tape from folding onto itself and stretching unevenly.

Episode 21 New Tiller

I broke my old tiller, by leaning on it. I'm sure I have a knack for finding the weakness in any thing or system the first time I touch it, leading to its immediate breakage. I've just got to think about how to market this talent; something like "Need to test your thing or system? just give it to me and I'll find the first thing that breaks in record time".

Actually, the old tiller came with the boat, and has survived my attentions until now. It split along the grain at the back, where it pivots on a bolt. This area is also the most exposed to the weather, so it is not surprising that it split there. When I broke it, I was about 5 nautical miles from home, and had to nurse the boat back by holding the tiller in the rudder stock. It was not a disaster, but it was awkward when I needed to hook up Otto*, the ST1000 Tiller Pilot.

(* Stolen from the 2008 movie WALL-E**)

(** Its a pun, Otto/AUTO/Autopilot***)

(*** Bad dad joke)

So, I decided to make a new tiller.

The first thing I needed was a suitable piece of wood. Pine would be fine; light and easy to work, but I was open to suggestions.

I went to a local specialist timber merchant, nearby. "Timber", it said proudly over the gate. It also sported a very large shed full of nicely cut arboreal material of different types, sizes and lengths. I handed the old tiller to the fellow over the counter and asked, hopefully, whether he could sell me something to replace it with. He scratched his chin, and told me that he could not. Pine, apparently, was not sustainable. What about another timber? No. Too heavy and difficult to work. Perhaps I should try Louis' Woodturning on the other side of town.

I might have missed something here, but directing me to another retailer (which happened to be closed at the time) did not strike me as a sustainable business strategy.

Finding myself in the position of John Cleese, upon entering Henry Wensleydale's Purveyors of Fine Cheese, I decided that arguing was pointless, and left with my tiller and wallet fully in tact.

Fortuitously, I found a nice piece of pine in my little hoard in the back yard. It was an off-cut from the bunks I had made for the trailer. Further, it had been CCA treated for outdoor use, so promised to be quite durable. I cut out the billet, and began to shape the handle.

Billet for new tiller, with old tiller at rear

Shaping the handle end

Knowing that the old tiller had split at its pivot-point, I reinforced the rudder-stock end with a couple of pieces of aluminium angle. The aluminium also served as packers, to take out the slack between the timber tiller and alloy rudder-stock, and spread the loading from the rudder stock onto the soft timber so that it would not get crushed.

I needed to cut some grooves into the aluminium angle, because the tiller stock had two cleats attached for securing the rudder in the up or down position. These cleats were held by round-headed bolts, with the round-heads protruding into the rudder stock. The old tiller accommodated these bolt-heads with some roughly gouged grooves. It took a little adjustment to get a snug fit. I shaved off the back a little, to allow the tiller to rotate freely on its pivot, and cut the length down to avoid a clash with the main sheet. The new tiller is longer than the old, which allows me to stretch a little less, when reaching for something forward with my free hand.

New tiller with aluminium angle reinforcement at rudder-stock,  ST1000 bracket fixed, and cover, with old tiller behind.
Another small improvement was the shape of the handle. The old tiller had a rounded square at the handle, but my version had a kind of upside down fat teardrop, which is easier on the hands and legs (one technique I am developing is to get both hands free by draping a leg over the tiller, and steering with that).

The new tiller now needed some external varnish. I think I have finally figured out why my previous attempts at varnishing have been rubbish. The missing ingredient was patience. 

What I had been doing was applying wet varnish to all four sides of something, including the new tiller. This inevitably led to drips and runs of gloopy stuff that would not harden, especially on the undersides. I think the drips carry the more gelatinous fractions of the varnish compound with them, so you end up with a soft, gloopy snot that you can scrape off with your fingernail. Its probably obvious to experienced varnishers, but is seldom mentioned in on-line tutorials

When I restricted myself to applying the wet varnish to the upper, flat surfaces only, I found that the gloopy snots would not form, and the coat would smooth out and harden within 4 to 8 hours, meaning that I could apply two every day. This turned out to be much faster than waiting a week or so for the gloopy snots to harden, and then attempting to sand them down. I could then lightly sand the hardened coat, and apply another layer, per the tutorials. 

My other tip is that "lightly" sanded means very little downward pressure on the sanding paper. You should apply just enough pressure to move the sandpaper back and forth. Too much pressure, and you could rip the varnish off in rolls or crumbs. However, I found that to be less of a risk when there were none of those gloopy snots to deal with. This shows you the importance of only applying the wet varnish to flat, horizontal surfaces, so that the gloopy snots don't form.

Finally, I thought about getting a cover for the tiller, to keep the sun of my shiny varnish. The old tiller had crazed and flaked to a grey mess in the sun, and I liked the look of the honey-coloured pine grain. It occurred to me that, in my hoard of stuff that may one day be useful, I had the "sock" that an old hammock had come in. To my surprise, it was the perfect length and diameter. 

In the end, the only new materials in my new tiller were the aluminium brackets and a tin of external varnish. The rest came from the hoards in my back yard. That's not to justify hoarding as a good thing in general, but just saying ...
Video of new tiller in the capable hands of Otto the TillerPilot

Episode 20 Theoretical Hull Speed

I had thought about calling this blog "How fast is my boat", then recalled that we're talking sailing here and a more appropriate title would be "How slow is my boat". Then I split the difference. Kind of.

According to boat-lore, longer boats are faster. You'll find formulae on the interweb that will work out the theoretical hull speed, but not many explanations about how the formulae were derived. So, I'll give it a go, based on my understanding of hydraulics.

The formulae are based on wave theory, but what has that got to do with boats? Firstly, sailing boats are displacement boats, meaning that they sit in the water, rather than skimming over the top of it like planing boats (or the ultra-modern sailing boats with foils). Displacement boats have to push the water out of the way to move forward. Most importantly, a displacement boat will sit in the trough of a wave, with the front peak at the bow, and the rear peak somewhere behind. The front peak is always at the bow, but the position of the rear peak determines the magical number - the theoretical hull speed.

The other important fact to bear in mind is that the speed of the wave is a function of the distance between the peaks (the wavelength). So, the faster the boat goes, the longer its wave becomes, until the rear wave peak falls behind the stern of the boat.

Try to picture three cases in your mind, looking at a boat from the side as it sails past;

  1. Front wave peak at the bow, rear wave peak half way along the boat. Both the front and rear of the boat are supported by the wave peaks, so the boat is sailing on the flat, lengthwise. The boat is simply overcoming friction.
  2. Front wave peak at the bow, rear wave peak at the stern. Again, both the front and rear of the boat are supported by the wave peaks, so the boat is still sailing on the flat, lengthwise.The boat is simply overcoming friction, again.
  3. Front wave peak at the bow, rear wave somewhere behind the stern. Things now change because the stern is not supported, so it drops. From the point of view of the boat, it now needs to climb uphill to keep up with the front wave peak. The boat needs to expend extra energy to climb the up the trailing face of the wave. Not only is the boat overcoming friction, it is climbing against its own weight, which tends to push if back, away from the front wave peak, thus slowing it down.

The additional energy needed to climb the trailing face of the wave becomes a case of diminishing returns, the faster we go, the longer the wave, and the steeper the climb up the trailing face of the front wave peak. The theoretical hull speed, then, is not a fixed limit, but it becomes harder to overcome both friction and the climb up the wave as the speed of the boat increases.

That's why it is possible to drive a sailing boat beyond its theoretical hull speed. You can do it with a motor boat, which will push it all the way to the top of the front wave peak but, then, you'll be planing.

And so, we can get to the formulae, which are a mix of theory and empirical observation. A useful one relates theoretical hull speed to the square root of the length of the water line

V = 1.34 x √LWL
Where

V = Theoretical hull speed in Knots
LWL = Length of water line in Feet

Note that this relates to LWL (length of waterline), not LOA (length overall).

Applying this to an eclectic selection of boats yields the following table. Apart from the last two boats, I have not included boats above 32 foot. This is because they become much more expensive above 30-35 feet, and they will likely need crew. Bigger might be better, but there is a trade-off in dollars and the ability to sail off on your own.

Boat LOA (ft) LOA (m) LWL (ft) LWL (m) Theoretical hull speed (knots)
Cygnet 20 19.3 5.9 17.7 5.4 5.6
Austral 20 20.0 6.1 17.0 5.2 5.5
RL 24 24.0 7.3 19.6 6.0 5.9
Noelex 25 25.5 7.8 22.1 6.8 6.3
Ross 780 25.6 7.8 23.3 7.1 6.5
Austral Clubman 8 26.7 8.2 25.3 7.7 6.7
RL28 28.1 8.6 23.6 7.2 6.5
Hanse 315 31.6 9.6 28.5 8.7 7.2
Cavalier 32 32.0 9.8 24.0 7.3 6.6
Suhaili 44.0 13.4 28.4 8.7 7.1
Ranger (J Class) 135.0 41.1 87.0 26.5 12.5

This table indicates that my Austral 20 has a theoretical hull speed of 5.5 knots. However I have pushed it to 6.5 knots and just touched 7.5 knots briefly, with a crew, coming down off a wave. It depends on which point you're sailing, how many spare hands you have, and the state of the sea. For instance, if I'm closed hauled and climbing upwind, I'd be happy with 3.0 knots, but if I bear away on a broad reach in the same conditions, I could do 6.5 knots. In the light of these experiences, I look at the theoretical hull speed as an indicator of the average upper speed of your boat. My Austral 20 might do a circuit of Peel Island at an average of 5.5 knots, but it would be prudent to allow for 5.0 knots, or even 4.0 when planning the day's sailing. If I were to upsize to an Austral Clubman 8 or Cavalier 32, I might be able to increase these allowances to 6.0 or 5.0 knots. The gain of 1 or 2 knots is not insignificant when you consider that tidal currents in Moreton bay could get up to about 1.5 knots against you.

Compare Sir Robin Knox-Johnson on Suhaili, who was the first person to sail solo around the world non-stop, covering 30,123 Nautical Miles in 313 days. His average speed was 4.02 knots (A World of My Own, Robin Knox-Johnson, 1969), which was much less than the theoretical hull speed of the boat (7.1 knots). However, he did not have the luxury of picking his conditions or scampering to port when the winds were either too light or too fresh.

Finally, it seems the boat manufacturers have done their sums, and know that most new boat-owners are likely to be fair weather sailors. The older designs, after the likes of Suhaili, have a considerable shorter LWL than LOA. The reason is that the boat is more "sea-kindly" with a sloping bow and counter (overhang) at the back.

So, for instance, an older design like the Cavalier 32 has a lot of boat above the water at the bow and stern. This makes it more comfortable in heavy weather. It slams less, when the front of the boat drops off a wave and hits the water below, because the bow is more knife-like. Its the difference between slapping water with the palm of your hand, and doing a karate-chop on it. It is also less likely to get pooped, when a trailing sea dumps a large volume of water in the cockpit, because the approaching wave will pick up the counter before hitting the cockpit. However, these sea-kindly features come at the expense of accommodation. Pinched ends generally mean smaller bunks and cramped cockpits.

The other factor is that although LWL gives you speed, LOA is what you actually pay for. Marinas tend to charge per foot (or metre) of the overall length, per berth. So, the difference between LOA and LWL becomes an "overhead". If you want to reduce the overhead, you need to reduce the difference between LOA and LWL, which brings us to the newer boat designs, such as the Ross 780, Austral Clubman 8 or Hanse 315.

These boats have plumb ends, which give you more theoretical hull speed per foot or metre of LOA. They also have larger accommodations; the Hanse 315 as a stern wide enough to place a double bed width-ways across the boat, which makes good use of the available space. They might be less sea-kindly than the older designs, but the manufacturers probably reckon that their owners would have tied up safely in their marinas than put to sea in rough conditions, anyway.

In conclusion, then, the theoretical hull speed is a guide, rather than a limit. Also, there is a trade off between speed, sea-kindliness and accommodation. Generally, the bigger the better, but bigger boats are more expensive and might be difficult to sail single-handed.

Episode 19 Galley

It has finally happened. I’d like to say it took, maybe three years’ of hard slog, unwavering dedication and unprecedented sacrifice. But, actually, it took a couple of weekends, some off-cut ply, a Maxie Metho stove from Gumtree, a donated sink (thanks to fellow tsp-er rseydler), some Hardiflex, stainless steel hinges, hooks and screws, and a few other bits and bobs. My boat finally has a galley.

Not just any galley, but a removable galley. Something you can take out of the boat and take camping, like we did last weekend, for a test drive. Again, I’d like to claim credit for a stroke of genius, but the truth is a little more mundane - a square box is easier to make than the curvey-wurvey thing I’d need to make for a permanent fixture. Besides, if I’d got it wrong, it could be removed without leaving a lasting scar on the boat.

It’s a bit agricultural. If I would remake it, I’d do it in aluminium. The 6mm Hardiflex that lines the stove box ensures that the thing will not catch fire, but its made of cement, and weighs a ton. Ok, that’s an exaggeration. The whole box weighs about 25kg, which is not much when you’ve got a straight back and plenty of room to move. But, doubled over in the confines of a cramped cabin manoeuvring the thing into place, I was acutely aware of how easy it would be to give myself a lower back injury. An aluminium box would be equally as difficult to set alight as concrete, but at a fraction of the weight. That would make it easier, for example, to haul it out into the cockpit for an open air barbecue. At least I now know the dimensions I would need.

The metho stove and sink works well, as we found out last week whilst camping at a mate’s property. It could do with a rack to drain the dishes (I’ll check out the camping stores), and a drawer below the sink. 

However, Version 1.0 was too big for the boat. I could either open the front, or the top, but not both. There was not enough room in the cabin. After a lengthy chin-scratch, I sawed the lids in half and hinged them. Now they fit - Version 1.1. The advantage in doing things on the cheap is that you know you won’t lose much by sawing your beautiful creation into bits. 

I'll need to fix it into place. In the accounts of Sir Francis Chichester and Robin Knox-Johnson on their solo-round-the-world voyages, there are scary descriptions of knock-downs in stormy seas. The boats had survived remarkably in-tact, but both sailors had estimated, from the dirt and debris deposited on the cabin roofs, that their boats had been turned from between 90 to 135 degrees from the vertical. To visualise this, imagine the mast as the hand on a clock, starting at around 12:00 and moving through 3:00 to about 4:30, and the cabin below doing much the same thing with everything in it. I doubt I would get the same extremes in Moreton Bay, but the lesson is clear; if it's not physically tied down, it might end up somewhere other than where you put it. And, if its as heavy as my galley, that means some serious damage between point A and point B and all intervening points inclusive. For fixings, I'll probably fix some eyes on the interior, and lash the galley to them. I should also do it before attempting to take the boat to sea again. No matter, I have some eyes and screws salvaged from the shelf (see below). Yes, I am the kind of person who keeps the screws from things after I have unscrewed them. Yes, I also sort them into different pots in the garage. Don't hate me. I do chuck out the ones with damaged heads.

The only sacrifice was the starboard shelf, the source of my new set of screws, which is now sitting in my garage amongst the small, but growing pile of boat-junk (I need to keep an eye on that, to make sure it doesn’t grow much more). Not a great sacrifice, because the remaining port shelf has enough room for the usual cabin bric-a-brac, and a previous owner had cut a car-radio-shaped hole in the starboard shelf for a now-defunct-car-radio. Apparently, marine environments and car-radios don't mix. Ho hum.

I’m not sure if I’m a dreadful snob, or just plainly sensible, but I find the noise of commercial radio unbearably intrusive. The car-radio and its speakers were among the first items to leave the boat, together with the rotting shoes. The gentle sound of the water on the hull is perfect therapy for me and I can’t imagine how that could possibly be improved by the urgent pleading of some numb-nuts psychopath trying to sell me carpets, or pizza, or shampoo, or the latest TV do-not-miss episode of pure shyte. If that’s your poison, then I hope you enjoy it, but, for me, one of the reasons to get on the water is to leave all that behind.

With a galley, and working anchor lights, I can think about longer trips on the water. I can now make a cup of tea, I exclaimed proudly to my wife, who then put my grand designs into perspective with just two words, as wives are wont to do; thermos flask. 

Galley - open, showing metho stove and sink

Galley - open, showing metho stove and sink

Galley - closed, showing drain pipe from sink

Episode 18 Pole, Son of Pole and Twin Poles

This is not a blog about Polish men, its about building a contraption for stepping* the mast safely.

(*Yachtie phrase, meaning getting the mast up)

I had the following criteria

  • It could be operated it single-handedly
  • It could be locked off at any point in lowering or lifting the mast, to allow me to scurry about and untangle things*
  • It could be folded up for storage
  • It was safe
  • It was cheap

(* This is inevitable when you consider the rigging's penchant for turning itself into a pile of knotted spaghetti whenever it is demounted)

Firstly, it is necessary to point out that the masts on trailer-sailers like mine, are designed to be lowered and raised. Mine has a pivot pin on the cabin roof, and is designed to be lowered backwards. Once the pivot pin is removed, the mast can be slid forward for transport-by-road. It seems likely that the designers of such systems believed that the typical boat-owner had a family of 7 ft weightlifters conveniently at hand for all such operations.OK, so that's an exaggeration, but getting the mast up or down is a challenge for me and a mate, and that presumes that I have a mate, and that he or she is available and willing to help.

The answer to my lack of mates, of course, is the mast-stepping contraption. This went through several iterations before I got something to work, which I have called Pole, Son of Pole and Twin Poles.

My first attempt was an early variation of a gin pole, using a long piece of timber. Let's call it Pre-Pole. A gin pole is a pole that is supported at one end and held at ninety degrees to the mast. The pole is supposed to be kept in this position by guide ropes secured on the deck. However, the wood in Pre-Pole split, and the mast collapsed onto the boat. Fortunately, my boat is strongly built, and didn't seem to mind, which surprised me almost as much as the mast falling down onto the stern of the boat.

Pole: 18mm aluminium tube with rubber vee-block foot,
showing buckling in the middle
Many, many months later, I revisited the concept with Pole, an 18mm diameter aluminium tube, 3m long from the giant retail hardware store down the road. By this time, I had my furler, which probably added another 30kg to the mast assembly, bringing it up to maybe 60kg, and the corresponding potential to do much damage if dropped.

Like its ancestor, Pole was a gin-pole, supported in the vertical position by guide-ropes on either side. The foot of Pole comprised a rubber vee-block, which, I had hoped, would grip the base of the mast. I drilled a 38mm hole into the rubber vee block to fit it to the end of Pole. The best way to drill a hole into a rubber block, I found, is with a spade drill, which is remarkably easy. The only hard part was sweeping up umpteen rubber shavings off the floor after the event.

If you're paying attention at this point, you might ask how I got a 40mm pole into a 38mm hole. The answer, of course, is that the hole is in a rubber block. One trick that worked well was to squeeze the rubber block in a vice. Drill the hole, release the vice, and the 38mm hole expands to 40mm. But, why not simply get a 40mm spade drill? Because the giant hardware store down the road didn't have anything bigger than 38mm.

Son of Pole before lowering the mast,
showing the yoke at the bow for the furler
Pole did not split, like its timber ancestor, and showed early promise as Pete (a mate, yes I do occasionally have them) and I gingerly rocked the mast and fuller back on its pivot. We almost declared victory, when we noticed that Pole had bent alarmingly in the middle, so we put everything back before Pole would be overcome by Euler's Buckling Load (something I had learned at University) and drop the mast on our heads.

Seeing that Pole was not beefy enough, I then tried Son of Pole. Son of Pole was a 30mm aluminium tube with 3mm thick walls, acquired from a metal merchant in the suburbs for about $30.

Son of Pole, with gin-pole upright and mast fully down.
Note the guide-ropes either side,
which should have kept Son of Pole upright.
Son of Pole did not bend in the middle, like its predecessor, and I successfully lowered the mast and took the photos shown here. However, when I tried to raise it again, Son of Pole inexplicably lent over to starboard, and the foot nearly detached from the mast. The whole thing threatened to collapse, so I got a shoulder under it. This time I was on my own (Pete had better things to do), and suddenly realised that I was stuck with a teetering mast and nowhere to go. Thankfully, a passer-by saw my predicament, rescued me, and helped me get the mast back up.

Now, I knew two things; the 40mm aluminium tube was beefy enough to avoid buckling, and I needed something to stop the mast slewing over to one side. I decided the most robust approach was an A-Frame, with two poles either side. Enter Twin Poles.

Twin Poles needed another trip to the metal merchant to buy another 40mm aluminium pole plus something to make the feet with. This delayed progress in weekly increments, as the only time I could get to the metal merchant was before 1100 on Saturday Morning, such were my working hours, and the metal merchant's opening hours. The same applied to the bolt shops, as I tried to source metric stainless steel bolts of the correct length, with or without shanks. The giant retail hardware store down the road does stock stainless steel bolts, but only in packs of three, or five, when you want four, and rarely of the right length or diameter.

Twin Poles: Foot assembly on the
starboard side showing ply board
slotted on to the base of a stanchion
and a chain plate, pivot pin assembly and
aluminium pole
I intended the feet of the A frame of Twin Poles to be supported on the deck either side of the cabin. The wider the feet, the more stable the A frame. However, there was nothing on the boat that would provide sufficient support and articulation. A simple rubber foot could slip, or punch through the deck. The first step was to make up a pivot pin for each foot, which is harder than you might think because everything was arranged at every angle except a right angle. I decided to get a couple of short sections of 70mm square aluminium box section from the metal merchant, cut one side off, drill through holes at the right angles and use M10 stainless steel bolts as pivot pins. I used aluminium because it was light, and quite easy to drill, cut and file.

Twin Poles: Yoke Assembly
part way through operation,
showing line through block on
the anchor plate to control the drop and lift
Next, the pivot pin assemblies needed to be secured to the deck. I didn't want permanent fixings, so opted to use some off-cuts of builder's ply. I realised a secure support could be got by using the ply to bridge between a stanchion and chain-plate. This had the added advantage of allowing all the axes of rotation for the mast and A-Frame feet to be positioned roughly in-line. Further, bring the A-frame feet further aft meant a longer lever arm, and a longer lever arm meant less stress, which meant more safety. I found most of this by experimentation, which resulted in my aluminium poles being about 200mm too short. The short-fall was made up by lengthening the plywood yoke. One pole was fixed to the yoke with two bolts, and the other with one to it be rotated to bring the legs together for storage and transport. Also, some rotation was needed because of the inaccuracy of my measuring, cutting and drilling.

Getting the angles right for the pivot pins was difficult. I pre-drilled the holes in the poles, then found corresponding points in the pivot-pin boxes. The pivot-pin boxes were fastened to the ply boards by a single bolt, which allowed some rotation between the pivot-pin boxes and boards. The rotation was needed to allow the boards to be slid into place. Some precision was needed to allow enough wiggle to allow the boards to be mounted and demounted, while getting the yoke to hold the forestay and furler in the right location.

Twin Poles; view from the stern
showing the hauling line passing
round the cabin top winch and
secured on the port jam-cleat
To prevent scratching the furler, I lined the inner faces of the yoke with an off-cut string of neoprene, held in place by some black goo and covered with a duct tape from an off-cast roll. Unfortunately, the furler didn't escape completely unscathed; when Son of Pole dropped the mast, the furler hit the ground and collected a few scratches.

I secured the spinnaker halyard to an eye on the top of the yoke, which was bolted directly to a corresponding eye on the bottom. The hauling line was secured to the bottom eye. I thought that a direct fixing from one eye to the other would be more robust than something that relied on the plywood in the yoke. In the final assembly, the yoke had no bending moments, and the forces were transferred directly between the halyard fixing points, and straight down the axes of the poles. The structural engineering that I did in the early part of my career came in useful here, as I visualised how the forces would be transmitted through the assembly.

Twin Poles: at the start of the drop
The hauling line passed through a block on the anchor chain-plate, went aft to the cabin-top winch and then further aft to a jam-cleat, where I could lock it off at any point. The photos show the furling line exiting the furling drum next to the hauling line. Its there because I didn't take it off, but it was slack and took no loads.

Easing the hauling line allowed the mast to pivot back. This was a nervy moment for me and I jammed the hauling line a couple of times so that I could go forward and check that everything was secure, and to take photos. As in previous attempts, the mast wanted to slew off to starboard, but Twin Poles held firm.

With the mast fully down, the lever arm of the A-Frame became apparent. I had intended to make the lever arm as long as possible to reduce stress, but had it been any longer, I could not have un-hooked the furler, which was now almost 2m above the cabin roof. Having dropped the mast, I took out the mast pin and shifted the mast and furler forward to rest on the bracket on the bow rails. I then made the boat secure on its trailer and hauled it home, where I intended to do more tinkering.



Twin Poles: Mast safely down

Twin Poles: Mast down,
view from bow showing
the A -Frame and hauling
line head-on

Episode 24 Keel locking pin

I don't like stuff that doesn't work. The locking pin for my keel had been annoying me for some time. Its not that it did not work...