Sorry to be so late responding to this thread - I haven't built a boat for a number of years and don't read the forum every week like I used to...

I built a sea kayak for my daughter, then aged 7. Having looked at her birth weight, and later weights, and consulted child growth charts (and looked at her mum:), I concluded that her adult weight would probably be no more than 45kg, at least whilst she was active...

Back then (she's now almost 23) sea boats for kids or even light adults, seemed to be off the commercial builders' agendas, so research led me to Nick's forum. I duly built a Great Auk, but scaled 5/6 of its design size.. Obviously displacement scales as the cube of the linear scale, and given Nick's design displacement of 216 lb (if I recall correctly), the smaller version would displace 125 lb, or 57 kg. The boat's own mass would scale as the square of the linear size, but I reckoned that a shorter boat with a light paddler didn't need quite the same strength as a full size boat, so I used thinner strips and lighter glass (5mm and 4 oz).

So, sixteen years on and we still have the boat (Geyrfugl), and Sarah does indeed still fit her quite well, and could even carry a fair bit of overnight kit. As my first boat, I made some mistakes, the worst of which were not building a cockpit recess nor any decent way of bracing inside. Reasoning that she would just keep growing, I couldn't devise a way of making knee braces adjustable, and my daughter, who is nowadays a very competent white water paddler, finds that the inability to "lock" herself into the cockpit is a bit limiting. A rebuild of the cockpit may be on the cards.

However, experience with the boat shows that she is an excellent match for Sarah's weight and build, and also can be paddled by someone (myself) who is way over the design paddler weight (I'm 85kg). Whilst I'm too big for stability in rough water, in calm conditions, despite the short waterline length, I maintain 5 mph with ease. Smaller paddlers find the low windage is particularly beneficial.

I wouldn't want to suggest a particular design, but ** do ** consider taking a design and scaling it to get a smaller boat - the results really can be worth it !

Hmm, I've lost track of how to post links here, but see if this gets turned into a clickable link:

http://waddingtons.info/kayak/geyrfugl-building.htm