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  #1  
Old 07-27-2005, 09:36 AM
Kiwi100 Kiwi100 is offline
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veneer racing shell restoration

I am starting to restore a 55 year old single racing shell and want to better understand the relationship between lwl and speed in such a rowing craft.
It is a veneer shell measuring 8.5metres long. If such a craft was built longer could it travel faster? What is the theory?Any on-line info. that would clarify this?
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Old 07-28-2005, 08:06 AM
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It could travel faster, but would need more power.
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Old 07-28-2005, 08:27 PM
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Typical shells are what we call displacement forms. They, by their shape, available power or both are limited to a speed governed by their waterline length (LWL) They lack the shape, power or both to overcome the resistance and wave system they generate as they move through the water. Provided enough power they can partly or fully climb over this wave train system and travel at higher speeds. Generally they are not shaped very well for doing this and if were over driven would likely become unstable and capsize. Speeds over the theoretical max hull speed (the square root of the LWL times the speed to length ratio) are met with a dramatic increase in resistance, generated by her shape and the wave train she's dragging along with her. To over come this the craft will need more power and or a different shape.
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Old 07-31-2005, 01:52 AM
Kiwi100 Kiwi100 is offline
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ok - will a twin shell rowing catamaran of the same length(but narrower) as a single hull (8metres) be faster with the same power input?
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Old 07-31-2005, 02:07 PM
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No. It will have more wave and surface resistance.
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Old 08-01-2005, 01:45 AM
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Rather then a lengthy dissertation on the principles of hydrodynamics, one question at a time, how about telling us what you'd like to do and we can address the possible issues that may arise in your efforts?
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Old 08-01-2005, 05:52 PM
Kiwi100 Kiwi100 is offline
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While working on restoring my racing skiff,I began to question why are single racing skiffs generally constructed to the same proportions of length(roughly 8m) to beam(roughly 300mm) and have been for many decades.
Why 8m long?Why not longer? Why not shorter?Is this dimension "traditional" due to a physical construction reason(in timber), or a physics law?
Is the 330mm beam decided by the minimum width that will comfortably accomodate the rowers rear-end, or is their another reason?What is the most effective theoretical length and beam in a single racing shell?
I am not a naval architect but am simply trying to understand "why".
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Old 08-01-2005, 06:31 PM
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I use to row a four. The hull shape is determined by the crew. A burly crew needs a beamy boat which requires more power to move. A skinny crew can have a narrower boat which needs less power. It ends up balancing out nicely.
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