: Hi. I'm thinking of building a shortened Guillemot, 15ft 6"

: I live 50 miles south of London UK so the boat will be used mainly for
: exploring inland water, some tidal.

The Guillemot is a very manoeuverable boat already, and like many loose
tracking kayaks, will turn very quickly to a lean. If you shorten the
boat, even with the scheme you suggest, you will lose some volume, the
boat will sit lower in the water which will lose some of that turning
ability. Another consequence is that you will lose some stability, which
reduces your abilty to put the boat on edge, which means you lose more
ability to turn quickly. There is some chance that the shorter boat will
end up no more manoeuverable than the full length one, whilst losing
other advantages of the original length. At 165lb, plus the weight of the
boat, you only have 10 lb for the weight of clothing, paddle, buoyancy
aid and lunch before you are nicely at the design displacement on the
17' boat. Any gear for an overnight trip, along with the reduction in
volume, is going to leave you a boat sitting very low ...

: ... some
: weight reduction as I am likely to have to put it on the car roof on my
: own.

Unless you have a very high car, you are likely to find that a strip boat
goes on a car roof pretty easily. I can lift all my boats on the car without
difficulty on my own - and that includes commercial fibreglass boats, which
are heavier. You are four inches taller than me, so it should be easier...
Whilst I wouldn't say it is without difficulty, I can usually get both our
own double fibreglass boat (at 33 kg) and our club double (at 40 kg) on the
roof on my own - and have done so in a force 9 :-) From that and other
experiences, I can say that the difficulty in getting a boat on the roof
is more likely to come from its wind resistance than its weight :-)

Do remember to put the boat on the roof empty - if you are using it as a
roof box for all those light, bulky (and wet) things like spraydecks and
buoyancy aids, put them in after the boat is up there. This can be a very
useful means of adjusting the trim of the boat on the roofrack, since most
modern cars have the forward roof bar well back from a very slanting
windscreen, so you find that it is not that far from the middle of the car.
To keep the weight of the boat between the two roofbars, it is useful to
load the part of the boat towards the aft of the car, thus enabling you to
keep the boat well forward and avoid illegally overhanging the back of the
car by more than one metre (the you need a light on it).

Of course, a short boat would also help here, so it's not all bad ... I built
a shortened version of the Cormorant at 14.4 ft. - this is not a highly
rockered boat like the Guillemot, and is not particularly more manoeuverable
as a result of this shortening. It cannot carry a lot of gear, but I can
lift it onto the car with one hand ... I suspect you don't need a boat
that light. My reason for building a short boat was down to workshop length!

Andy