More info on my design - changes too.

This is the boat I want to build for myself. I didn’t give enough info in my last post so I thought I would give people a little more to go on and not have them think I was looking for someone to do my work for me. It sure looked that way when I re-read my post today.

I made some changes so things are a bit different but not much.

The hull was designed with Greg Carlson’s HULL program. The attached doc contains design pictures.

Off Shore fishing boat - Center Console (head under center console for the missus who loves to fish as much as me )

Criteria – Dry. Smooth in a rough chop and able to handle 4 to 5 foot seas. Self-draining cockpit. Upright and positive floatation (I know, not required in this size but I want it)

Specs:

Max Beam – 9’ 6”
Length – 31’ (not including drives)
Disp. – 8389 lbs @ 134.62 ft3
LWL – 305”
Center of Buoyancy - 208.9”
Center of Lateral Area – 208.5”
Lateral Area – 40.65 ft2
Prismatic Coefficient – 0.74
Power - Dual GM 6.5L diesels (170 HP?) jackshafted to Bravo stern drives.
Props - ??????
Fuel – 200 gallons
Water – 30 gallons
Expected max speed – 30 to 35 knots (more would be fine )

Proposed build:

Hull bottom:
2 or 3 layers of 3/8” plywood (I’m not sure if 2 layers of ply is sufficient) laminated together with epoxy and with 3 layers of tri-axial cloth (3400), inside and out.

Chine flats have almost 3 degrees downward angle and are 2 layers of 3’8” plywood.

Hull sides:
3/8” plywood with 2 layers of 3400 tri-axial cloth inside and out.

Keel joint and chine joints will have 3 layers of 6 oz. biaxial tape.

The outer and inner epoxy/glass laminations will be in one lay-up and vacuum bagged.
That is, the joints will be taped and all glass layers placed and vacuum bagged before the epoxy begins to kick. I have been working on a 1/6th scale model and have perfected the technique to do this.

All joints will be filleted and have 3 layers of tape. The diagonal created between the hull side and the inner chine joint will be filled after being filleted and glassed. The fill (not sure what to use yet) will then be glassed over.

2 longitudinal stringers on each side from laminated plywood or laminated hardwood. The stringers will need to support the cockpit sole. This means the inner stringers will need to be 20” deep and the outer ones 15” deep. I’m not certain on the width but I am thinking 1 ½”.

Transverse frames will be spaced every 60” and be 1” by 3” from laminated plywood or laminated hardwood.

The deck and gunwales will be 3/8” plywood with 1 layer of 6oz. cloth on the top and 2 layers of 6 oz cloth on the bottom.

Questions:

I am I over or under building? I may be doing both, over in some under in others.

I am not sure if I have the displacement correct. I tried to calculate my weight as best as I could. If the displacement is different the stringer height will change since I want the sole 4 to 5 inches above the water line.

Will 2 layers on the bottom of the hull be enough or should I go with 3?

Is 1 1/2“ sufficient for the width of the stringers?

Will it be stable?



Any and all opinions and comments are welcome.


Vince

 

Vince, I only skipped through your post, and I'm not really the one to give advice on construction details - However, I would suggest that you get hold of a copy of Dave Gerr's book - The Elements of Boat Strength . It should answer all the above questions, and any more that you might have as your design progresses