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Old 21-01-2009, 17:42   #31
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Originally Posted by Robertcateran View Post
Aluminium is a weight versus size thing. Part of it is finding enough stiffness for the skin without going to heavy or having ribs and stringers everywhere. Dinghies get around this to some extent by having ribs pressed into the skin. Aluminium is still significantly heavier at the 40' mark but Easton in Australia seems to be doing quite a nice job of making them pretty quickly and reasonably light. There is also the problem of fatigue and electrolysis. Notwithstanding there are quite a few aluminium multihulls sailing around the world.
I was going to build a 40' Crowther motor-sailing catamaran aluminium fishing boat before the bottom fell out of fishing. In composites I would save about a third the weight .
There are other ways to go rather than foam and balsa. Polypropylene honeycomb is starting to get some traction, and there is also strip plank.
Have a look at Pacific Cats website for a comparison in using polyprop honeycomb core. If you really want to go light, have a look at the Harryproa website where concentrating all sailing loads into a relatively small area significantly reduces weight.

Much of a multihulls weight is in the beams and reinforcing to provide support for the sailing loads. The scantlings are only one part of the equation. Making heavier scantlings then introduces greater inertial forces and sailing loads.
The Alubat Cigale 16 is lighter and faster than most fiberglass boat of the same size yet is stronger. I think the same can be achieved with a catamaran. The only problem I see with aluminum is cosmetic. Aluminum does not like to be painted and if you do you have to do quite a bit of maintenance on it. Every 4-5 years a complete paint job or constant touch ups. Electrolisis can be managed successfuly and fatigue factored in at the design stage.
Anyway, let's not stray from the topic.
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Old 21-01-2009, 18:10   #32
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I'm not sure that the spirited boats have any balsa below the water line.
This link may provide interesting reading. Are balsa panels water resistant?.
Building a Catamaran.. Outgassing?
Very interesting. Epoxy does not replace poor quality control from the manufacturer. He should have sent the whole lot back. The material does not meet the claimed quality and performance. Pretty worrying !!
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Old 21-01-2009, 18:18   #33
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Originally Posted by 44'cruisingcat View Post
The 3 spirited 380's I have seen all have balsa as the core in the moulded parts both above and below the waterline.

As for the experiment conducted by TCP's editor, that has Duflex boat builders simply scratching their head. It's well known and accepted that the weave on a Duflex panel should be filled before painting. It's a simple matter of applying a runny epoxy glue mix with a squeegie or trowel. Why someone would go to that much trouble to "prove" what is already well known it is a mystery.
If the weave is not impregnated enough with resin is not only a problem of water proofness. The lack of resin may reduce the bonding to the core and could eventually result in separation.
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Old 21-01-2009, 18:40   #34
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Yes, the EC Spirited scantlings are higher and more conservative than the standard Aussie 380. The CE Duflex kit weights 300 kg more than the Australian kit (mainly in biax skins), and part of it is compensated using Superlite Balsa core. And no, the EC certification cannot be obtained for the Aussie version.

Olliric, where would you sail and what would be your typical programme (cruising distance etc) during those four weeks breaks ?
Is the kit for the Spirited 480 available certified according to CE standards? If so what are the differences in cost and weight?

I would be mostly cruising around in the tropical belt (beginning with a few years in the Caribbean). I would have to move the boat north to south because of hurricane season and relocate the boat to different cruising areas every few months. Some of these boat moves are over 1000 miles. Given the time restraint I need a boat that can take bad weather and hard fast sailing no problem. I may have to go to sea without waiting for the best conditions. Sooner or later I'll get in bad weather and get my ass and the boat's kicked.
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Old 21-01-2009, 20:39   #35
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Interesting site and articles. However, I believe that if one wants performance has to compromise somewhat. If I were interested in building a boat that can take the battering of dock pilings during a hurricane I would chose metal, no solid fiberglass like the surveyor recommends.
All I want is a boat that is fast but can take the beating of a storm or years of fast offshore sailing without problems. I am not interested in having a collision proof vessel. Multis are already pretty safe in that regard.
The article doesn't only refer to collision damage. It also shows foam cores which have been destroyed by water saturation, something we are told won't happen with closed cell foam.

Both balsa and foam cores work well as long as proper practices are followed. People seem to think because it has closed cells, foam gives a license to take short cuts. I posted the link to the article to show that foam can be vulnerable to water penetration just as balsa can.

Foam is lighter than balsa, balsa has siginficantly better engineering properties. You can build a very good boat with either.
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Old 21-01-2009, 20:51   #36
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Originally Posted by olliric View Post
If the weave is not impregnated enough with resin is not only a problem of water proofness. The lack of resin may reduce the bonding to the core and could eventually result in separation.

If there is not enough resin the glass shows an opaque white appearance, rather than the normal translucent appearance.

However there is still the distinct texture of the glass, which needs to be filled before painting. It's possible the laminate could be slightly porous, since the small gaps between the fibre bundles would only be filled by resin that was in excess of that required to properly wet out the laminate.

When you squeegie on a runny glue mix to fill the weave you also fill any possible pores.

For literally hundreds of Duflex boat builders before Bob Norson this hasn't been an issue at all, and almost certainly it won't be an issue for hundreds more builders in the future.
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Old 21-01-2009, 21:56   #37
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When you squeegie on a runny glue mix to fill the weave you also fill any possible pores.

For literally hundreds of Duflex boat builders before Bob Norson this hasn't been an issue at all, and almost certainly it won't be an issue for hundreds more builders in the future.

Unless of course out-gassing blows little craters through the setting mix.

Yep if one closes their eyes they will see no problem. I've just spent the weekend helping a friend cut out a couple of square meters of rotten balsa from around a "supposedly" properly sealed deck fitting. Its amazing how far the water can travel. I hope he pulls the remaining deck fittings and lifts some laminate to see how the rest are travelling, before things start to fail big-time.

As the saying goes "only a rich man can afford to build a boat with cheap materials".
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Old 21-01-2009, 22:29   #38
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Unless of course out-gassing blows little craters through the setting mix.
I got that with WRC, Kiri, and some foams as well depending on the temperature

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Yep if one closes their eyes they will see no problem. I've just spent the weekend helping a friend cut out a couple of square meters of rotten balsa
Epoxy as in duflex or a slapshot poly boat with contour balsa?

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from around a "supposedly" properly sealed deck fitting.
AH, the plot thickens

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Its amazing how far the water can travel. I hope he pulls the remaining deck fittings and lifts some laminate to see how the rest are travelling, before things start to fail big-time.
I saw at least one if not 2 44 gallon drums of water get sucked from a large foam cat at Manly, so again, not a balsa specific problem
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As the saying goes "only a rich man can afford to build a boat with cheap materials".
Like the foam boat above?


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Old 21-01-2009, 22:35   #39
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Foam is lighter than balsa, balsa has siginficantly better engineering properties. You can build a very good boat with either.
Foam also needs more glass and resin negating the weight advantage.

Of course you can use foam Kevlar epoxy, but most will need black balaclava's and shotguns for the funding.

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Old 22-01-2009, 03:17   #40
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If there is not enough resin the glass shows an opaque white appearance, rather than the normal translucent appearance.

However there is still the distinct texture of the glass, which needs to be filled before painting. It's possible the laminate could be slightly porous, since the small gaps between the fibre bundles would only be filled by resin that was in excess of that required to properly wet out the laminate.

When you squeegie on a runny glue mix to fill the weave you also fill any possible pores.

For literally hundreds of Duflex boat builders before Bob Norson this hasn't been an issue at all, and almost certainly it won't be an issue for hundreds more builders in the future.
Well, it's not very reassuring to know that the only safe barrier to stop the water from getting to the balsa is the pre-painting preparation. The coat is likely to be not very thick and could be removed by scratching against something sharp.
However, I guess that if the construction is done properly and with very careful use, water can be left out of the core.
Do you have some statistics on the numbers of boats built and problems reported? How long has Duflex been around?
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Old 22-01-2009, 13:28   #41
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There are hundreds of Duflex boats around the world. AFAIK none have had problems with wet cores. But why not contact ATL and ask them? ATL Composites - engineering resin foam waterproofing carbon fibreglass adhesive fairing boat repairs structural fibreglass
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Old 22-01-2009, 14:10   #42
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The Alubat Cigale 16 is lighter and faster than most fiberglass boat of the same size yet is stronger. I think the same can be achieved with a catamaran. The only problem I see with aluminum is cosmetic. Aluminum does not like to be painted and if you do you have to do quite a bit of maintenance on it. Every 4-5 years a complete paint job or constant touch ups. Electrolisis can be managed successfuly and fatigue factored in at the design stage.
Anyway, let's not stray from the topic.
Most fibreglass boats are not built near as light as they could be through not taking care in engineering and materials. I agree with the rest of the post
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Old 23-01-2009, 00:33   #43
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There are hundreds of Duflex boats around the world. AFAIK none have had problems with wet cores. But why not contact ATL and ask them? ATL Composites - engineering resin foam waterproofing carbon fibreglass adhesive fairing boat repairs structural fibreglass
Kit boats and insurances companies:
How do insurance companies value the kit boat to issue coverage? The fact that the boats are not built meeting recognized standards (i.e CE or classification societies') can be a reason for denial or restriction of coverage?
Cheers
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Old 23-01-2009, 01:05   #44
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You get the boat valued by a surveyor.
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Old 23-01-2009, 23:12   #45
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$350k US is roughly $500k Aus. That's probably little or no cheaper than you could have a Duflex kit boat built here in Aus. Friends had an Oram 44C built by Streamline Catamarans Streamline Catamarans: Sailing Catamarans for less than that.

A Schionning would cost more, being a more expensive kit, and more complex to build though.

The Schionning at 44 feet is a much bigger boat that an Oram44 which has a volume of a regular 38 foot boat.
Thus the kit would have to be more expensive.
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