Thursday, November 30, 2017

Ratios of Bow Length to Stern Length - Kayaks

At the risk of spreading misinformation – this might be of interest to some, see tables below.  Been talking to a friend about various boat options he’s considering buying. So, I made these very approximate measurements simply using plan-view photographs available online to help that discussion. They show the ratio of bow length to stern length for select SKUK and Tiderace kayaks. The numbers mean nothing in themselves (I measured in centimeters with a ruler on the computer screen) – but assuming the photos were all well-centered when taken and assuming my measurements are fairly accurate (two big “if’s”), I think the bow/stern length ratios say something about the behavior of these boats.  The bigger ratios have more length in front of the cockpit as compared to behind the cockpit, whereas the smaller ratios are more balanced fore and aft.

So for example, the Romany is at the higher end of the bow-to-stern ratio with a 1.64 and behaves that way – its comparatively short stern is very maneuverable when planing on a wave and the boat remains straight-running in following seas, resists broaching more than some. But when paddled forward aggressively on flat water its short stern (and therefore lack of volume behind the cockpit) can cause the kayak to “sink” in the rear, especially with a heavier paddler (like me at my 185 lbs former weight).  At the opposite end of the scale, the Explorer and Latitude are more balanced fore-and-aft, coming in at the lower end of bow/stern ratios – 1.50 and 1.41.  Having owned an Explorer, this makes sense – it glides better, resists “sitting” in the stern and is good for distance paddling. 

This “method” can’t be used across kayak manufactures – I think it only says something when comparing boats of very similar hull design.  The SKUK hulls are all “variations on a theme” with roughly similar distribution of volume, rocker, etc.   Comparing these ratios for SKUK boats against ratios for Epic kayaks, for example, would be meaningless as these boats have strikingly different shapes. Most significantly, the Epic hulls are based on surf skis and so are strongly swede-form, so can have very high hull volume behind the cockpit despite having a comparatively short stern.

I did the same thing for some Tiderace boats I’ve paddled – separate table below.  It too supports my impressions of these kayaks.  The Xtra is designed for playing in rough water and sure enough has a comparatively high bow/stern length ratio of 1.58. Whereas the touring purpose of the Xplore has a lower ratio of 1.36.

Just something to think about.