THis topic got me curious about how commercial builders scale their designs. The following chart is based on data from the Eddyline Sitka series of kayaks. Eddyline (and Delta) manufacture kayaks using thermoformed ABS. They are very rigid, tough, and relatively light. These boats are in the $2500 range so less expensive than composite hulls. The Sitka line has 3 hulls and started with the SitkaST model. The following table (cm units) shows how this series of hulls was scaled. Interesting things to note is the LT scales up the ST by about 5% in all dimensions but that the XT scales the depth more than the width - possibly because the 62.2 CM width translates to 24.5” which is already pretty wide for a touring hull. I assume that the capacities listed (in kg) are the maximum safe load capacity and not the target for the hull’s DWL.
Hi David,
interesting question you posit here. as Lazslo pointed out in the post on scaling, one of the designers he highlighted says when you change it, its no longer what it was.
i think when we use the term ‘scaling’ we are typically referring to trying to make a ‘true’ copy at a different size.
but i am not sure i would frame what eddyline is doing here as ‘scaling’ as much as understanding that they have different size customers that they are trying to retain under a brand/model that they have invested in…. with certain key features that people like….and brand/model equity…. and they wanted to capture market share by having an offering for three typical body sizes.
so did they ‘scale’ or have three fresh designs from the hand of single designer that they wanted to build with the same general mission profile and key design characteristics that are tied into the ‘Sitka’ family/model name?
i think its the latter…..
if you look at Guillemot Kayaks, for example, he has families such as the Guillemot Family which all share some common characteristics/looks but includes 8 individual family members.
in the night heron family he has 13 seperate designs (including all the petrels) that all share some common attributes and offerings to different sized paddlers and slight variations on mission.
anyway, i thought i would just put that out there…..i think that is what they are doing…but i would not describe it as ‘scaling’.
h
i thought i would add a bit more to the idea above….
one of the things that is also very common, as well, is a well regarded hull but with different decks….typically a low volume version and a higher volume version. in this case, the different market may be folks who need a bit more room or knee bend, or mission capabilities….the high volume version for those who need to pack a lot of gear and the low volume version for folks who maybe are just day paddling or a single overnight….
exampes of this approach include the chesapeake 17 vs the 17LT (light touring). or the many variations of the night heron (high deck, low deck, rolling version) that all basically sit on the same hull profile/dimensions below the design waterline.
even joey schott’s manufactured petrel has an addition 3/4 inch added to the deck hight becuase (as i understand it) the petrel as designed, he thought, would have too limited a market as a result of its relatively low deck/tight fit for a lot of people.
again, i would not describe these as ‘scaling’ approaches but leveraging well proven designs and brand loyalty to different people sizes and mission profiles….with, depending on the approach, something less than a full unique design…..
the attached two pictures show some of my explorations of these ideas:
the first picture is a modified petrel play where volume was taken out of the ends but preserved in the middle…..the objective was to leverage the hull but make the boat lighter and more svelte becuase it was going to be used mostly for paddling in protected waters…and thus the extra volume in the ends was not needed: the approach ended up shortening the boat from 14 feet to 13’ 8 inches and took about 3 square feet of surface area out of the design.
similarly, in this picture of a modified microbootlegger sport, the entire deck was lowered 1 inch and the back deck had volume taken out as i just wanted a more stealth looking machine and i was not going to go camping with it. it also took about 2.5 sqaure feet of surface are out of the boat so it only weighs about 27 lbs fully rigged:
