speed boat design

This is boat i have oprtunity to test, and in many ocasion whatch on heavy sea hovi is riding, and like i say for our sea seams to be good. In our adriatic sea tha wave are shorter for the same wave height. Si this tybe of boats proven to have very good sea keeping for waves that come from bow. Yes they are litle wet riding, and have some broaching problem but nothing that i can handle

 

And i test and see this fjord also, and this colnago

 

It isn't necessary to put up with wetness and broaching, both are avoidable, and without compromising performance. And to my eye, the kind of boat you appear to favour, is not as stable as it might be, with its triangular plan shape.

 

But how do you know that it will weigh 6,000 kg?
Have you done an initial weights estimate, and have you also come up with a rough initial estimate of your scantlings required - you might well find that the boat becomes heavier than initially expected.
It is very easy to add structure weight to a boat, and very difficult to remove it.

 

We do all weight estimation hull and srtucture 2100kg
Engine with drive shaftx2 1500kg
Pasenger 1200kg 14people
Interior 80kg
Windglass 80kg
Fuel 700kg
Paint and kit 150kg

 

Litle bit less than 6000kg

 

A 7.5m planing boat, 350 HP of power, in GRP, should weigh around 2.4 tons when empty. Multiplying that weight by the ratio (10 / 7.5) ^ 3 would give us a weight of 5.7 tons. Add the fuel and the passage (1.9 tons) there and we would obtain a total weight of 7.6 tons

 

Maybe for now with all reinforcment, Aluminum welded Will be Around 2100kg we Will sea, what efficency in max surf you sugest i use for the calculation for inboard Engine. 60%?

 

I Will try put 7000kg in maxsurf and i sea. If i get 2litres per nautical miles at 23, 24 knots i Will be very happy

 

Yes, I think that's correct.

 

How do you do a hull and structure weight estimate if you don't have a design? For example, the slamming loads on the bottom will determine what the scantlings and framing. The hull resistance will determine the power needed. You can't simply pick up engines at random. What you propose is a recipe for disaster.

 

We have all srtucture from this version of our design, calculeted and all srtucture. Now we Will change for my blue design. Will be slight diference but not to much in weight, maybe less. I Will send you that picture of the Frame later. My naval engineer is very skiled in srtucture. But as i said less in planing hull hydrodynamics. What you think of this slight change in lines on this picture?

 

Your hull is all developable surfaces ?

 

Yes, most of them

 

3d model 1:25 it is over and welded, tomorow towing tank test