Where to start?

No, re-sizing a set of plans don't work because proportions don't move up or down proportionately. In other words a small boat scaled up will have too much beam or the reverse a large boat scaled down will lack stability.

 

Oh, you mean length to beam ratio or something like that? I was thinking of thickness of the hull, based on the reading I have done so far.

Interesting.

 

The bottom line is it's not as intuitive as it seems, as I mentioned in a previous post. The "Law of Mechanical Similitude" rules the roost and there's no way around this.

In a nut shell an example. Lets say you want to double the size of a boat. Wetted surface increases by a factor of 4 not 2. Hull volume and weight increase 8 times, stability 16 times that of the little sister ship and finally the length, draft and beam double in size.

It's simple, the general dimensions increase to a power of 1 (linearly), volume and mass are cubically increased (3rd power), stability is to the 4th power and surface area (hull, sails, etc.) the 2nd power.

It becomes quickly apparent that if the size differences are very despairing, simply scaling it up or down just doesn't work.

There are a number of these engineering principles that can toss a wrench into "design change" ideas of the novice and why you might have noticed considerable resistance to suggestions of such. Guess what happens to structures when you make changes.

 

The rules of scaling were already something I had come into contact with. I have some stuff which is used to make a scale model which supposedly lets you predict full-sized behaviour. The linear/square/cube part based on number of dimensions is not too difficult on the surface. I didn't know about the stability part though.

I'm not planning on diving off the deep end here. I'm just trying to learn what I can before I buy plans and build. I already tried to build a hovercraft by the seat of my pants, I have no intention of doing so again with a boat.

The whole idea of scaling came up in the beginning of this thread, where someone (you?) had recommended lengths of boats to look at, and then the models I was being pointed to were too small for that. The scaling idea was simply to get the equivalent size for my more-than-average weight.

At the moment, my current inclination is for a wood boat with strip plank construction, perhaps with the Lord method or the variations you suggested, although I don't know exactly what those are yet. It would be good to have something that LOOKS like a wood boat if I could. I don't know how much of the grain shows through on these non-glass skins though.

One thing that came to mind is that the Lord method seems to be the ideal case for vacuum infusion.

Again, thanks for your time.