1 << Rob's Racing Harrigami Report 2 - Photos

• a lighter boom that could be removed without removing the mast and a jib sheet track that was not so vulnerable to damage.
• a telescoping mast to reduce weight and windage aloft.
• a new cheap mast building technique suitable for amateurs.
• a rudder system that allowed the rudders to kick up in a collision, and to be steerable in shallow water, with no holes in the hull below the water.
• rudders that would work in both directions without rotating 180 degrees.
• demountable beams and a quicker method of attaching/detaching the trampoline

The racing possibilities resulted in

• A longer lee hull with finer entry
• minimum sized ww hull
• wider boat

These were relatively easy to achieve. We lopped off the foam bow and bonded and shaped new ones. It will be interesting to see if this is strong enough. It is certainly tough enough. I hit a steel piling head on at 2 knots yesterday. No visible damage. The entry could still be finer, so a bit more shaping may take place down the line.

The lee hull was drawn around 2 bunks, with a bit of space between them, as is required for the rules, then knocked up out of 8mm kiri with double bias glass each side. Lighter and less windage than the cruising one. Also not as high, so the boat and trailer will fit in a shipping container without having to remove the wheels.

The wider beam meant that folding was not possible, so we tapered the ends of the beams and fitted sockets in the hulls. This has worked a treat and is now standard on all designs. The tramp attachment system is very easy, not very elegant and takes about 15 minutes for 2 people to fit the 4m x 5m tramp. We are working on the elegance! The racing ww hull is interchangeable with the cruising hull, with very little effort.

The ideas to be tried were a bit more challenging.

The boom is diamond shaped with 100mm square box section sides. About half the weight of the old one and pivoted in the middle to allow folding and removal. The surprising thing (to me) was how difficult it was to locate it in space. It needs 8 pieces of rope, plus the main and jib to keep it in position. I have some ideas for removing some of these, but it is a more complex bit of gear than the original box boom. It does solve the jib track problem, and also the removal hassles. For the heavy load bearing pieces (boom vangs and forestay) I made some carbon cored rope. This should not (has not so far) stretch and was far cheaper than any other marine rope of equivalent breaking strain. However, it is difficult to knot or splice successfully so terminations are tricky. The core is also very prone to damage, so needs to be looked after.

The telescopic mast was built in four pieces using the carbon strip planking technique described on Building walk through Harrigami Week15 . Materials cost was less than $aus2,000. It was ready to join when I broke my achilles tendon and had 8 weeks on crutches. I decided that, to get the boat in the water in the summer, I would forget the inevitable time consuming debugging process and join the two halves to make a single piece mast with ballestron rig, instead of the proposed una rig. The mast with all fittings weighs 50 kgs. The telescoping idea is still near the top of the to do list, for beams as well as for masts.

The rudders were a lot of fun. I decided to mount them outside the hull on the windward side of the lee hull. To allow them to kick up, we built a semi circular track for the top attachment to rotate around. This failed miserably as it needed too tight a tolerance. The bottom attachment had to rotate in 2 directions and was achieved with a stainless rod through the hull with a tube welded on the end. Even less elegant than the tramp but it worked. The rudder blades were mounted in cases to allow them to be lifted/lowered. This also worked. The back of the cases breaks open in the event of a collision, allowing the board to kick up. The first set of blades were a 2 way section drawn by Tom Speer. These would work very well as daggerboards, but getting them to trail fore and aft when the tiller was released was beyond me. This was a function of the location of the pivots, not the boards. After a lot of trial and error, I abandoned them and went with conventional NACA0012 sections as per the photos. A simple solution which does everything required, but still not perfect, see sailing results.

Half a dozen paragraphs to describe 6 months work! The heap of discarded bits and pieces out the back of the garage is probably a better indication of what has been going on.

2 of us lifted all the components onto the trailer and towed it down to the water. Assembly took a few hours, but included some messing around with the mast bearings. Didn't get a chance to weigh it, but it should be less than 500 kgs. Could easily knock 50 kgs off this on the next one. The old dagger cases are still in the lee hull, as are 4 unnecessary bulkheads and a lot of bog. The mast is also 10 kgs overweight due to the join and the tapering process. The next boom will be lighter, and smaller.

We did some drag tests, although the results are a bit dubious due to choopy seas and the difficulty for the tow boat driver of steering straight and reading the scale and gps simultaneously. The three points we did get were: tow speed of 6.5->7 knts = 16 ->20 kgs, 9->9.5 knts = 28->32kgs, when trying to get to 12 knts it was around the low 40's but would bang on the end of the spring so I slowed down so that we didn't damage the scale. These figures are pretty near spot on the figures for a 4.5m/14' racing dinghy. Not bad for a 12m/40 footer!

I have sailed it 3 times so far. Each time in 4-8 knots of breeze which is typical round here in winter, if it is not blowing the oysters off the rocks. Top speeds by gps so far is 10.3 knots, reaching relative to the true wind. The bottom was a bit grubby, the rudder blades are not at undercoat stage yet. The jib needs a bit of work, so upwind performance is not good.

The rudders work, but because they take all the sideways load and because the gudgeon pivots are ahead of the hydrodynamic centre the tiller loads are high on the aft rudder. I can see no way round this as balanced, liftable rudders are not possible, so will lock the aft rudder and steer with the front one. It will not be a problem for wheel steered boats. With the rudders locked, it tracks very well, and does not seem to be affected by me moving round the boat.

The mast is very stiff, the boom rigid and the hulls both slip through the water with remarkable ease. Shunting is very easy, even singlehanded. Sheet loads are higher than I would like, but will reduce when the jib is sorted. No sign of hull flying, even with me sitting to leeward.

So far so good. Not yet competitive with a hot 40 foot racing cat, but pretty quick on the basis of sail area (30 sq m dacron, to make recutting easier) or cost ($Aus20 grands worth of materials). And still a lot of improvements to come.

The sailmaker is coming out this week to sort out the jib, and there is a mono race on the 24th.

The to do list includes:

• following the monos around to get a feel for our performance,
• capsize/ extreme hull lifting tests, both static and sailing
• trying my 9 sq m kite, then in September buying a tailor made version.
• borrowing a screecher to check out control and speed related issues.
• Finishing the paint job and rudder blades and removing some weight.
• Sleeve on the mainsail
• Maximising the area of the jib and main. The areas and shapes chosen were to enable us to get a feel for the sail balance for the boat for Maine, for which we had no time for sea trials.

We also have a sponsor, with offices all around the Pacific. More on this and my plans/dreams on official launch day.

More on sailing in higher breezes as it happens. Any comments, questions, ideas or improvements, either email me or share them with interested parties on the multihull (multihulls@steamradio.com) or proa (proa_file@yahoogroups.com) mailing lists.

Rob

Click on the images to enlarge. Photo credit, thank you : Julian Zotti.

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