Scaling plans

**cjbfisher** · 15th December 2011, 11:52 AM

I've heard that plans can be scaled up or down by about 10% in length, but not in width. I'm looking around for a S&G kayak design at about 10ft in length, but what I'm finding is that most plans (that I like) start at around 13ft. Is it possible to reduce the length by 10% without changing the width, or is it more complicated than that?
Over to you, learned gentlemen.

**anewhouse** · 15th December 2011, 12:30 PM

When you reduce the length of a kayak, the stability drops (if all else remains the same). The width of a kayak is not the only thing that gives it stability.

Reducing the length of a 13ft kayak by 10% will still leave it a bit over your target of 10ft. Reducing it to 10ft would have a huge effect on stability. You would need to significantly increase the width to get some stability back. That would make it uncomfortable to paddle and would make it harder to keep going straight.

Once a kayak gets below about 13ft, its potential top speed drops dramatically. Once it gets down around 10ft, the effort required even to maintain a leisurely cruising speed begins to increase too. That may be part of the reason that few S&G kayaks are designed to be less than 13ft. In fact 15ft is a really good length for a recreational kayak for an adult.

When you shorten a kayak, as well as affecting the performance, you will probably also affect the ease of construction. The bends become tighter as the length reduces and increasing the width adds to that problem.

One way to look at the effect of modifications to a design is to download free software such as the excellent program available on this site.
Blue Heron Kayaks

Then create a design a bit like the one you are interested in and notice how the stability and the drag change as you modify it.

**Seafarer** · 16th December 2011, 05:19 PM

They are probably more canoes than kayaks, but Paul Fisher has a couple of S&G designs around the 10 foot mark. He does have a small kayak at 12 foot 6 though.

I have built one of his 10 foot "Sophia" canoes. It was very easy to build and is as light as a feather.

If you have not found the SFD website already, have a look here: Selway Fisher Home Page

Cheers, Cameron.

**cjbfisher** · 17th December 2011, 07:49 AM

Thanks for the reply guys. My current build is a 15ft SOT for fishing open water with surf launches and retrieves. Initially I had intended to fit a Hobie Mirage Drive to this kayak, but have changed my mind. So now I want something small for fishing in creeks, and I'll fit the Mirage Drive to it.. Speed isn't a big issue here, but I don't want to end up with a pig either.
Cheers,
Chris

**redreuben** · 22nd December 2011, 12:45 AM

Little Auk Kayak Plans | Guillemot Kayaks

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Google is your friend !

Enjoy,

RR

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