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Rob Denney at tthe clubnight


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Rob - we'll probably go round in circles on this so I'll cut it short and just answer your specific question to me

 

Where does it say this? Surely "Fundamentals and Definitions" apply to everything that followed? The cat 5 regs are an appendix, so presumably the F&D's are to be included?

 

No. In the preamble it says -

"** - means the item applies to all types of yacht in all Categories

except 5 for which see Appendix J."

Appendix J repeats only 1.02 from that part of the F&D.

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ScottieE,

So it does. Silly me. Not much help for the CC, or for getting out of NZ in a cruising proa. I'm happy to go round in circles on these points if you, The Rev or anyone else can add anything to the conversation.

 

Samin,

I got over W in the CC the same day Jason banned it, 12 years ago. You bought it up last week when you thought you could score some more cheap points. 18 months ago, you gave me a hard time about my version of the banning, said you would ask Jason whether my version of events was correct or not. You have piked out of answering ever since.

 

As you know, my boat is pretty much built. Took 300 hours. Less than the difference between what you thought yours would take and what it actually has. As you also know, I am waiting for a 16m infusion table to be finished so I can build the mast. Then I have to wait some more while a couple of other boats are built on it.

 

It is pathetic how you are polite to me when you want boatbuilding advice, yet can't resist the chance to put the boot in the rest of the time. Equally pathetic is that you know every little detail about your boat's weight when you want to make a point, but "can't be bothered working it out" when it doesn't suit. And how you are "off to work on your boat", then post on other threads. Why don't you just tell the truth?

 

Let me help with some guesses. Your 88 kg hull is 8.5 long, 1m high at the bows, 4m from gunwh'l to gunwh'l in the middle and 1.5 g-g at the stern. Say 21 sq m. The ply bulkheads total maybe 4 sq m, so 25 sqm all up. Not so difficult, was it?

 

rob

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Interesting, where is this boat being built? Is the infusion you are using similar to the "kelsal method" I may not have the spelling right - I am just finishing a tri out of foam glass and my end conclusion is there has to be a better way. Is there any site which has how the method/process works in detail and what shape restrictions there are?

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Interesting, where is this boat being built? Is the infusion you are using similar to the "kelsal method" I may not have the spelling right - I am just finishing a tri out of foam glass and my end conclusion is there has to be a better way. Is there any site which has how the method/process works in detail and what shape restrictions there are?

 

Sounds like you might have already seen it but there is a lot of info on the Kelsall site and he has DVDs etc available. If he ever holds another workshop here I might attend out of interest. His modular assembly method looks like a cool way to build a bridgedeck cat if one was so inclined.

 

Rob, where did you get to with the amateur build carbon masts?

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Looks a very interesting design, very light, and would be interesting to see how it would compare to our racing multis here in Auckland.

How much 'drag, is induced by having such a short windward hull?

And what sort of sail area does a 50ft cat or tri run as a comparison?

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Interesting, where is this boat being built? Is the infusion you are using similar to the "kelsal method" I may not have the spelling right - I am just finishing a tri out of foam glass and my end conclusion is there has to be a better way. Is there any site which has how the method/process works in detail and what shape restrictions there are?

 

Build is on the Gold Coast. Builder is an excellent infuser, but has peculiar ideas about time. Owner is a German, but I get the boat for extended sea trials before it is shipped. State of play is that the lee hull is now closed up, the foam glass ends and paint to go.

 

The guy is Derek Kelsall, the method KSS. One of the multihull pioneers and the most experienced and innovative foam boat builder in the world. 80 something year old pom, still going strong, currently living in Waihi.

 

I copied what he has done with infused panels, and simplified it for harryproas which have much simpler hull shapes, eg no rocker and high prismatic, plus I don't care what they look like, as long as they work, and are as light and low cost as possible.

 

There are no restrictions to shape, but the further you get from single curves, the more work you have to put in. This can be done post infusion, the way Derek does, or on the table (I have done small experimental bits, to prove the principal). Or it can be fudged, the way I do it on the actual boats.

 

There is not a lot about the technique that isn't in the video. The bits that are missing (lying carbon tow for local reinforcement, infusion tricks, bow shaping) were thought of by the builder, so are not mine to disclose. Attend one of Derek's seminars and you will learn most of what you need to know. Or buy a sheet of glass and a vac pump and have a play. For anyone who has bucket and brushed, infusion is a wonderful world. Any specific questions, ask and I will try to answer.

 

Since starting these hulls, I have changed my thinking on hull shapes. Flat bottomed hulls are quicker over 10 knots, a little slower under 5. More importantly to me they are lighter, lower and much easier to fit out. Because of this, I have altered the technique and now make the hull/deck in a single, simple mdf mould. The bulkhead and shelf landings, hull join, mast step, deck bearing, hinges, beam sockets, rudder sockets and all the reinforcing these require are included in the infusion. After the parts are infused, everything is glued together in matching male/female joins. The only fairing is a smear of bog in the tiny rebates at the joins. There is no secondary laminating apart from the 6" of foam/glass bows which are made off the job and glued on.

 

After you have learnt the procedure with the first half hull, each half takes a couple of days. Of this time, only 40 minutes per infusion involves resin, and after the resin is mixed, you don't come in contact with it again until it is cured. Assembling the halves, including installing the bulkheads is another day's work. A light sand and they are ready to paint. The weight, cost and time savings are appreciable.

 

Greg,

Amateur mast building plans $500. Well worth it with carbon cheaper than it has ever been. We are also making them professionally, starting with the beams and masts for the Toro 34 and, more interesting, 6 unstayed wing masts that hinge just above the booms for 12m biplane rigged cruising cats.

 

John,

I am busting to see how it goes against other multis, both here and in NZ. Maybe a trip over will be part of the sea trials.

 

The ww hull has a beam/length ratio of 1/12. Until it is going reasonably fast, (maybe 10 knots), it has less form drag than the lee hull which is 1/37 (Edmond Bruce, Design for Fast Sailing). Once it is going this fast, the crew sitting to leeward will fly the ww hull, so the form drag is not an issue. My experience with much less extreme differences in the hull widths is that it makes no practical difference. In much the same way as you do not notice any huge change in helm when you go from 2 hulls in the water to one flying.

 

The Classe 50 multis (Crepes Wahoo, Prince de Bretagne, etc) which have a circuit consisting of round the buoys and short handed ocean races (Route de Rhum, etc) typically have

- LOA 15.24 m / 50 '

- Beam 15m / 49.2'

- Displacement 4.2 tonnes

- Height above water 23.77m / 78'

- Draft 3.5 m / 11.5'

 

Sail Area

- Main Sail : 100m² / 1076.5 ft ²

- Gennaker : 150m² / 1615 ft²

- Solent : 73m² / 786 ft ²

- Staysail : 45m² / 484 ft ²

- ORC : 22m² / 237 ft ²

 

About all they have in common with the proa is loa and high speed. Take your pick of the numbers to decide which will be quicker. The proa will be sailing for well under $100,000. The tri for well over $1,000,000. Maintenance on the proa will be a similar order of magnitude less than the tri.

 

rob

Beam 2.jpg

Beam 1.jpg

2011-10-28 Mast Mould.jpg

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"After you have learnt the procedure with the first half hull, each half takes a couple of days. Of this time, only 40 minutes per infusion involves resin, and after the resin is mixed, you don't come in contact with it again until it is cured. Assembling the halves, including installing the bulkheads is another day's work. A light sand and they are ready to paint. The weight, cost and time savings are appreciable."

 

Nice beam, wouldn't mind a flash new front beam like that for the VB.

Admire the work Rob, but having heard the kind of statement above a lot of times and seen a lot of boats built, I still haven't seen it happen as easily as predicted.

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"After you have learnt the procedure with the first half hull, each half takes a couple of days. Of this time, only 40 minutes per infusion involves resin, and after the resin is mixed, you don't come in contact with it again until it is cured. Assembling the halves, including installing the bulkheads is another day's work. A light sand and they are ready to paint. The weight, cost and time savings are appreciable."

 

Nice beam, wouldn't mind a flash new front beam like that for the VB.

Admire the work Rob, but having heard the kind of statement above a lot of times and seen a lot of boats built, I still haven't seen it happen as easily as predicted.

 

A beam with the "carbon look", 5.5 metres long, trampoline tracks, stainless inserts and compression tubes (the works), for a boat with righting moment of 7000 kg.metres is a paltry $Aus9500. ;-) $8,000 if you can live with it being painted.

 

The "easy build method" statement has been made a lot of times, including by me about the system in the video. Do you know of a quicker way of building 95% of a hull, deck, bunks and cockpit than folding it up out of 3 sheets of material that took a week to lay up and laminate on a flat table?

 

A bit more detail about the the moulded hulls statement above:

1) setting up a half proa hull and decks for infusion in a couple of days.

This involves wiping a layer of release wax on the mould and and hot melt gluing the rebates in. Then cutting the foam and glass, using the hull as patterns. Then locating , and adding bulkhead/shelf landings, local reinforcements, mast step, beam housings, join blanks, etc. Then peel ply, vac bag and the infusion plumbing (2 vacuum lines along the edges, and a feed line down the middle).

This all happens with dry material on a mostly horizontal surface, working downhand with little tailoring required for odd shapes and a wide flange on the verticals to tape the various dry layers to, so they stay in place.

It is easy work compared to wetting out and bagging a conventional one off laminate which would normally be done in three stages (inner skin, core, outer skin), plus fairing on a male mould. Or stripping, fairing, glassing, fairing, turning over, fairing and glassing a strip plank hull. Then installing the bulkheads and fitting out and building and bonding the deck on.

2) 40 minutes to infuse the laminate,

That is how long you have (with vinylester, can be more with epoxy, but it is a pretty big job that takes more than 40 minutes) before it starts to gel. If it doesn't happen within this time, you have not paid attention and need to do some repairs.

3) no contact with the sticky stuff after it is mixed. One of the wonderful things about infusion. The wet out is all done by pressure and is uniform, optimal and perfect.

4) a day to glue it together. Again, this is all you have as it must all be glued in one shot. This will involve contact with the sticky stuff, but only pumping it into male/female joins and wiping off the excess afterwards.

5) the fairness of the finished job. The hulls have no compound curves, so the lines all fair automatically using butt block joined mdf.

6) weight, cost and time savings. No secondary laminating, filling or fairing, no unnecessary doubled up laminate on any joins and all the laminate consolidated under vacuum will be lighter than conventional builds. These savings and maybe 5 kgs of wasted resin per infusion, almost no wasted cloth or core and mdf moulds will be cheaper. Weeks instead of months is certainly faster.

 

Please let me know which steps you think won't happen as easily as predicted, and why. Ideally based on some of the builds you have seen.

 

 

rob

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