Small alloy hulls ARE heavier.
It takes plenty of ribs to support the skin. This makes most of the weight. Same size (small) grp can be build in sandwich-foam - and thus are lighter than a grid built alloy
hull.
But it is not a huge difference and in specific cases may be reversed too - at times with very unpleasant visual after-effects.
For alloys, the interesting material is called (I think) strongall, which, if I am not mistaken, allows to build no frame alloy hulls.
I have seen such a
hull in NZ. And I did like it.
b.