While in Fremantle for the 2002 Grolsch 505 World Championship, I was able to check out 505 technology in the dinghy park and nearby. Since this was the first 505 World Championship with the long luff spinnaker, there was quite a bit to see in terms of mast rigging. The new carbon pre-preg 505s from Van Munster and Fremantle 505 looked great. Not all 505 technology was working well, as a number of masts were broken in the first race of the pre-worlds and some rudders and rudder fittings broke early in the pre-worlds too.
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| The launcher, bulkhead and mast step mouldings sit in a hull |
The CB trunk sides moulding lying loose in a hull |
The launcher front is not yet fitted to the tube here |
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| The launcher, bulkhead and mast step moulding bonded to a deck |
The opening in the watertight bulkhead where it extends into the mast step is sealed closed by bonding in another piece of carbon skinned honeycomb. |
Various openings in the deck moulding are sealed closed the same way |
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| The launcher-bulkhead- maststep moulding not yet bonded to the tanks-and-interior moulding |
launcher-bulkhead- maststep moulding bonded to a deck |
The openings where the tanks become the transom are sealed closed with carbon skinned honeycomb. |
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| Inside seat tank bracing |
I am SO impressed with what I saw of the pre-preg construction process. It is a much cleaner working environment than with a wet layup, and the clock is not ticking while you do the layup. You use a vacuum bag with both a wet layup and a pre-preg layup, but are not time constrained putting the bag on with the pre-preg. The moulded parts were very light; I picked up a completed but not bonded together hull and deck (so everything except the forward bulkhead-launcher tube-mast step moulding and the centreboard trunk liner moulding) with another person. My estimate is that the two major moldings going into the boat weighed 100 pounds together (that might be 45 kg). The boats feel very stiff when I pound on them, though I wonder about the longevity of an all-carbon layup; my understanding is that carbon is "brittle" and cannot absorb energy from impacts by yielding, so a collision with a dock or another boat may well result in greater damage than would happen with a fiberglass or Kevlar boat, or even a boat that has both carbon, and Kevlar or glass in the skins.
There actually is a very little bit of glass in the boat. In order to get the honeycomb to bond to the pre-preg carbon, they are using a very light-weight pre-preg glass cloth that has a very high resin-to-fiber ratio, so they are more or less adding a layer of epoxy in between the carbon skins and the honeycomb. The glass cloth is very fine and very light, and may also help with any porosity issues in the carbon pre-preg, keeping the honeycomb sealed.
My PDA crashed while I was returning from Australia and I lost some of the detailed notes on the Fremantle 505 I had. So I have no specific cloth details and weights (Brett had been happy to answer all my questions on these topics). I believe they are using pre-pregs from SP systems. I think they started with a carbon twill cloth and still use that for the bulkead-launcher-mast step moulding, though they switched to something else for the hull and deck. At least one of the hulls -- for Nigel Lott -- was built of two layers of carbon biaxial pre-preg on either side of the honyecomb core. That boat has more carbon than the normal pre-preg Fremantle 505 and cost more, but that is what Nigel wanted. Apparently one has to be careful orienting the cloth, so you get the same thing on both sides of the core, and do not create any twist in the resulting moulded part. So I think with two layers on each side of the core, the two inner layers match up and the two outer layers match up.
I believe the core is Nomex; the streched version that bends on one axis more easily than another. The core may have been one cm in thickness.
Windrush puts a near-vertical seat tank reinforcement web in the boat that ties the middle of the seat tank to the hull. You can see this in one of the photos on the web site. I was intrigued that they thought they needed it, given the apparent stiffness of the mouldings. It would also increase the fitting time when preparing to stick hull and deck together.
The parts are released from the molds, trimmed, other pieces are bonded in, but the hull goes back into the mold for bonding the deck to the hull.
In various places in the deck and launcher-watertight bulkhead-mast step moulding, pieces have to be added to make them watertight. For example since the Fremantle 505 thwarts are moulded with the seat tanks, the areas where they attach to the seat tanks have to be sealed, otherwise an opening into the seat tank will remain. Similarly for the watertight bulkhead to mast step transition; the mast step is not watertight but the forward compartment has to be. The gaps are filled with pieces of honeycomb cored pre-preg carbon, similar to what the part was layed up with.
The opening through the diagonal bulkheads is not made by a removable piece in the mold but is cut out afterwards. I would guess portions of this cut out are reused to fill the gaps as in the above paragraph. The resulting cut edge is manually filled and smoothed. The result does not look bad.
My recollection is that the CB trunk liner molding is not cored. It has to be fitted to both the hull moulding and the deck-centerboard-cap-thwarts-diagonal-bulkhead-foredeck moulding. I do not recall seeing any extra reinforcement to handle loads from the high aspect ratio jibing centreboard loads.
The boats are painted after coming out of the mold as apparently the carbon pre-preg does not stick to gelcoat sprayed into a mold particularly well.
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| A Van Munster being measured Note forward thwarts |
Aft end of the centreboard case on a Van Munster |
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| The Nicholsons' Van Munster forward thwart and jib sheeting |
The Nicholsons' Van Munster aft thwart |
The Nicholsons' Van Munster shroud and rail |
Van Munster started with a Kyrwood shape and Fremantle started with a Van Munster, though I'm not sure if it is the current Van Munster shape. YMS also started with a Kyrwood shape. Everyone is happy to tell you how they faired and improved what they started with. I have never worked on a plug, so am not sure how much shape change and improvement can be accomplished without going through the outer skin into the core in places, if the plug is an actual hull.
Both Windrush and Van Munster remove the core in a strip of the seat tank area running aft of where the thwart emerges from the seat tank. They simply fill the space with carbon. The idea is that a lot of heavily loaded fittings are mounted there and rather than deal with the core crushing, they put solid carbon there. They may even tap into it rather than using nuts (I am not sure about this).
The South Australian YMS boat has the thwarts angled forward as they go from the centreboard cap to the seat tanks, which I liked, but they retained most of the aft face of the forward thwart, cutting away the forward face, when I would prefer the reverse. The Van Munster forward thwarts go straight across the boat from the centerboard cap to the tank, while the Fremantle 505 forward thwart goes straight across the boat from the centreboard cap to the seat tank floor join. The South Australian YMS boat starts out very narrow in the bow, and then goes out to maximum waterline quite quickly. Apparently the idea is to get the boat to plane early.
I am not sure what difference a stiff hull has in performance from a very stiff one. Even the softest hulls being built now are far stiffer than those being built in partly cored polyester. I wonder if a 505 can be too stiff.
One of the "problems" that both Van Munster and Windrush have is bringing the boats up to weight. They are building them way light, and are loath to add carbon pre-preg material to add weight (a VERY expensive way to add weight). This seems like a no brainer to me. They could wet layup (and possibly vacuum bag) resin-rich glass to the central areas of the boat after the pre-preg layup cures. More material on the cockpit floor, CB trunk sides and aft thwart cannot hurt.
Krister noted that the Van Munster hull shape was noticeably different than that of his Rondar. He notices spray coming off the hull at different places at different angles, and that the stern wave looks different. I'm not sure if mere mortals would notice this. He also noted that the inner and outer centerboard trunk design used by both Van Munster and Fremantle results in a lot of CB trunk for the skipper to step over or around when tacking and gybing. Krister mentioned preferring the American boats in this respect, and told me he had cut away portions of the centreboard trunk structure on his new Van Munster. He also pointed out that the limber holes were not very large and not all the way to the floor, so the boat would collect some weight in water that would be hard to drain out.
Nigel Lott, an engineer who was having a new Windrush built (the guy who ordered the Windrush/Fremantle with thicker skins than standard), described an interesting CB construction approach he had used. He created a numerical model of his CB, gave it to a shop with a 3D cutting capability, along with a core he had built up, asked them to increase the cuts in various places by the thickness of the carbon cloth skins he was using (skin thickness varied from the top of the blade to the bottom), and for not very much money got his machined core back, and then vacuum bagged the skins onto it. His first blade was substantially overbuilt with a heavy core, but the potential for machining a CB blank with different core materials such that the loads where the CB emerges from the bottom of the boat are handled while keeping the rest of the blade core very light, intrigues me. Nigel thought he could have these cores built for little enough in Australia that it would be cheaper for me to have him do it for me, than if I tried to have it done myself in the USA.
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Pip Pearson's rudder head You take it off the boat by unbolting and removing one of the transom fittings. No shockords, split rings or clips for Pip! It is also VERY strong and seems very unlikely to break. |
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Upper spreaders with upper shrouds the upper shrouds may run through the lower spreaders |
upper shrouds running through the lower spreaders |
long swinging upper spreaders with upper shrouds |
A Goldspar with upper diamonds? |
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Upper spreaders, with upper shrouds going to the mast tip |
Upper spreaders with upper shrouds |
Waterat spreader extenders with upper shrouds |
Trapeze wire twings or tweakers |
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| Trapeze wire twings or tweakers |
Upper shrouds may be deadended on spreaders |
Pinnell's halyard lock and reinforcement |
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| Carter Jackson hangs from a prototype carbon fibre mast |
Simon Lake hangs from a prototype carbon fibre mast |
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As can be seen from the Top Ten Gear and Crew Information Table, the trickiest anyone in the top ten got was high trapeze wires. However a number of other teams were working on various systems, some of which are pictured here.
Carter Jackson brought a carbon fibre mast for everyone to look at. While no one sailed with it, it was subjected to some rather agressive testing in the dinghy park.
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| Slot gasket rubber detail on Thad Lieb's 505 |
Thad punches a round hole at the front end to avoid a stress concentration |
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| A double pole launcher system | Deck detail for the double pole launcher |
Most Aussie's don't use the Spiro or Proctor fitting |
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A number of teams had paid close attention to the slot gasket rubber. Some used two separate rubbers. Thad Lieb had a nice simple slot gasket rubber with a stress relief hole at the front of the cut away.
Ali