Fibreglass layers for 16-foot recreational fishing boat

Hi there,

Firstly, I apologize if this has been covered somewhere and I just couldn't/didn't find it and, if it has, please point me there and I will go and check it out.

The real reason for my post is that I have been given a 4-piece female mold for building a 16-foot recreational fishing boat that could be powered by up to a 15hp outboard motor and will be suitable for 2/3 people to fish in. The first part of the mold is for the hull itself, the second for the gunwales, the third for a cuddy/cabin and the fourth for a hatch for the cuddy/cabin.

I want to make a boat to use myself and have some experience of molding fiberglass having built components for other boat projects but have never built a hull. My real question is what layers are appropriate for layering up a boat like this? My initial thoughts were as follows:

Layer 1: Gelcoat
Layer 2: Gelcoat
Layer 3: Fiberglass Tissue Matting
Layer 4: 450gsm CSM
Layer 5: 600gsm Woven Roving Matting
Layer 6: 450gsm CSM
Layer 7: 450gsm CSM

I may reduce to 1 coat of gelcoat, I haven't really decided yet, but opinions or advice on my initial thoughts would be appreciated.

This is the mold for an idea of scale.

 

The layers farthest from the neutral axis should be stronger than the ones closest to it, that is, the opposite of what you have foreseen.

 

I'd say that woven roving won't be much use to you, with that "clinker", you won't get it to follow the contours. Stick with mat, and being a displacement type hull, weight saving isn't that important. Looks like a nice little boat !

 

Hand layup in that mold would be a nightmare due to all those lapstrakes.
It is very difficult to roll out air from a series of depressions, pressing the material into one valley pulls it out of adjacent ones. (The one you just completed!)
Maybe someone on here knows a technique for doing this without vacuum bagging, but IMO even bagging it would be dicey.
Cool boat, though, what’s the cabin look like?

 

Mat should be OK. You might be able to use some unidirectional rovings as well, depending on how sharp the corners are with that clinker. I guess chopper gun would have been the method used to build them. But woven rovings, no hope.