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Old 13-01-2007, 15:08   #1
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Question True Cat Weight

There has been some discussion as to why Lagoon's seem to be so much heavier than other cats. Some feel its an issue of specsmanship, with vendors not making equally loaded comparisons. Others feel that some vendors publish numbers that are simply false.
Utlimately it would be nice to know the true sailing weight of all the various cruising cats. There was a chart published by Cruising World which provides a summary of various aspects of Cats, including the weight
Cruising World - Cats By The Numbers
But the data for this chart is suspect, and it is most likely right from the builders. Which gets us back to trying to determine the true weight.
Apparently Cats get weighed when they race. However, this may not be a good source since do Cruising Cats really race? It seems to me that another source would be from Marinas when they pull Cats out of the water for Hull repair or a major retrofit. Anyone have a source for real data?

An alternative to such data would be to compile all the actual draft specs. It does not seem to me that Draft would be exagerrated of falsified, as it could lead to disaster. If two boats of roughly equal length and hull widths have drafts that are a foot different, then one clearly is a lot heavier than the other.

Anyway, we just need the facts.
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Old 14-01-2007, 04:01   #2
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There’s only two weights that allow accurate comparison:
1. Wet weight, /w all tanks full
2. Dry weight, /w empty tanks (but capacities specified)
Neither weight should include variables, such as provisions or crew.
Naval Architects/Engineers can accurately calculate either weight.
Both weights are measurable, by scale.
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Old 14-01-2007, 13:34   #3
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I realized that the draft approach is not a good one. The problem is that Skeg adds to this draft and its length varies depending on manufacturer and boat size.
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Old 14-01-2007, 13:53   #4
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You might be thinking of POUNDS PER INCH IMMERSION (PPI), which is the weight required to sink the yacht one inch. It is calculated by multiplying the LWL area by 5.333 for sea water or 5.2 for fresh. The PPI usually increases as the hull sinks into the water as the LWL area is also increasing due to the shape of the hull above water.
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Old 14-01-2007, 20:43   #5
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Here is the Schionning comparison table that has immersion rates in KG.

And a converter for those that need it [like me]

Online conversion of weights and measures, measurement conversion.

I have not seen any of these go in the water over their lines and even loaded with all the toy's they still float free and sail well.

Therefore the numbers must be reasonably acurate.

It amazes me that I keep Plugging these cat's yet I am not building one.

Dave
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File Type: pdf DesignComparisonTableJuly05.pdf (158.6 KB, 180 views)
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Old 22-01-2007, 01:02   #6
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its the cost of the plans hehe
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