GOP Home Build

Hi there I have been tinkering with a set of Plywood cat hulls and building them into a centre console fisher. I was hoping to begin this thread to get some constructive feedback in the construction process.

First question: Using Sailing hulls with a Rocker, how essential is flattening the rocker out toward the stern?

 

Welcome to the forum.

If you expect the boat to get up on plane, then you'll have to kiss off what you know about sailboat cat hulls. The shapes employed are quite a bit different. What design are you working with?

 

The hulls are two old sailboat hulls I picked up and I want to have a single power unit planing cat. I understand that I might have to build out the rocker to float the stern?

 

No design in particular, I have drafted a few plans, but I am very much an amateur with no real boat building experience to speak of. To be honest, I am pretty much winging it at this stage.

 

Making sailboat hulls act as full plane powerboat hulls isn't very practical. You'll have to reshape the after half of both hulls. The lack of building experience can be overcome easily enough, but the design portion of the project, isn't nearly as easy. Which sailboat are these hulls?

 

Gop ?

 

Goop On Plywood

 

Can't think what else it could be !

 

Years ago I encountered a couple of blokes who decided to motorize a 14' Hobie cat with a 25 hp outboard, the result could best be described as (near) Death By Hobby-horsing. Not sure if they went out more than the once in it.

 

Glass over ply smart ***.

I have started building up the aft portion of the Hulls. I am putting in a stringer from the Transom forward in each of the hulls . I only figure I have to build them up about 10 cm, so no biggie. First job is to flip the structure over now! need to get a few mates around for that, and will then start on the Aft build up, Transom and tunnel skin.

 

What is the power and desired speed ?

 

Not Sure yet about power, anywhere from 60 to 90 HP. desired speed is around 40knots?

 

You are absolutely kidding yourself at 40 knots and a home brew modification, without a clue about planing hull hydrodynamics. You'll be inviting longitudinal instability around 20 knots and 40 is well, just way out there in terms of reality. The real test will be taking bets as how much over 20 you can get, before she'll self pitch pole. Of course, the beach cat hulls (my assumption) aren't intended for this level of punishment, so maybe you'll get lucky and just stove one in, long before the sterns try to swap ends with one or both bows.

 

Ok good to know> Ill keep trucking and see how it comes out.

 

if after the whole effort it becomes a 5knot trout barge then so be it, but I'll give it a blast and see what happens.