Efficiency: Submerged transoms

Actually, will be starting out in Corpus Christi, TX, mostly using the intracoastal waterways to make my way over to south Florida, then cross to Bimini and on from there.

 

Yeah, well that is open waters, I doubt some super slim, super lightweight boat will be much fun

 

It would seem to me length could be beneficial from a pitching standpoint if the majority of the weight is centralized. And I imagine the shape of the hull is a large factor in pitch damping.

 

The slenderness of itself makes pitching a potential problem, and especially if with fine ends.

 

Seems a lot more comfortable than the planing powerboats buzzing all over the bahamas

 

I have considered this, and this will come into play later in the design process, right now trying to nail down principles concerning efficiency. And I know that I cant have everything, but you can have a lot if you are willing to make sacrifices in living space, etc. I am more concerned about pitchpoling with too fine hulls.

 

The problem comes when you are heading into the waves. You might get away with 16:1, probably better 13:1

 

Correct.
And with a high L/B ratio coupled to your L/D ratio... the waterplane inertia is lower..so it shall be "less stiff" than a conventional lower L/B ratio cat...so its response will be more benign.

 

Shortening the hulls while maintaining a similar displacement would seem to have a lot of consequences, almost seems like it would be more uncomfortable in smaller waves because you are just bobbing up and down, not penetrating. For instance my friends pontoon boat would cut right through large wakes of other boats, while his planing boat would get practically airborne and he would have to back way off the throttle.

 

You haven't got to shorten the hulls. Just don't have flat bottom up forward or slamming could be a problem

 

Hulls will be semicircular, gradually becoming sharp towards the front. There's just no way to maintain the length at that displacement without changing the shape of the hulls to something with significantly more wetted surface area.

 

very slender hulls = sensitive to longitudinal weight shifts = sensitive to increased loads ( increase in wetted area)

 

I thought initially you were talking a river or lake, the open sea is a different matter, to hell with maximising "efficiency" at the expense of reasonable comfort

 

You and me might consider becoming friends. I plan to move there.

And despite Ad Hoc's correct analysis that many of these posts fall into polemic nonsense; I try to avoid it and be as helpful as possible.

My issue was definitions. I don't know if there is a definition of semi-displacement vs displacement.

I still wonder if you will have trouble getting enough displacement at 20:1. And that doesn't require being a NA to ask about.

 

If you prioritize ease of propulsion to an extreme extent, there will be a price to pay in various other ways.