Fishing boat cabin rebuild - reshaped

Starting this project I had no experience with fiberglass whatsoever and that is why I have to thank everyone that takes time to share their knowledge and experiences online. This forum has taught me most of the knowledge I have today on boatbuilding and helped me get through some tough step on this project. So im sharing my project with everyone and hope someone finds it useful like i have many of your posts on this forum.

Ok so I decided to do some mods on my boat and decided to change the shape of the cabin as the one fitted on the boat didnt quiet suit my needs and was leaving much unused valuable space, but most of all I wanted to learn about boats and do this as a learning project.

So heres my project boat its a 18 ft fiberglass half cab unknown make powered by 2002 Yamaha 85 hp



I believe on a smaller boat every inch is precious. And as you can see from the pic I had to crawl to the access hatch just to pull the anchor in.

And heres a pic of a cabin on a seaswirl stripper, this is roughly the shape I was after to suit my needs.

 

After a lot of research I decided to build a foam form and lay fiberglass on top.

 

The suspense is just killing me !

 

I had to cut out the old cabin in order to mark out the shape for the new one.
I was left with a giant tinnie !

Things looked very scary at that point but there was no going back.

 

love the hull, looks like a greywell commando built in melbourne. they have a good reputation.

 

After I had the shape I wanted to build plywood sides about 5" tall just for extra support. Than I realised that standard plywood boards would just snap if I tried to bend them in angles I needed. So what I did was (jump on the forums and read read read) got myself 3mm thick plywood sheets and using a jig I made steam my sheets and epoxy them together.




I steamed 4 sheets here (I found that ply sheets this thin dont really have to be steamed getting them wet with hot water was enough) and just slowly bent them. If you are using too much force to bend the sheets chances are your wood is not wet enough, just keep steaming until you can bend it with ease. Clamp them into shape and allow to dry thoroughly. When dry they should pretty much be exactly the same shape when unclamped. I used epoxy mixed with cabosil to bond all the sheets together. Ply sheets were sealed with a layer of straight epoxy before applying cabo. Than Clamped together and allowed to dry.

 

Im from melb too, Ive been trying to find out the build for ages with no luck. I love this hull, on the water handles amazing.

 

Using the jig I made 2 halves and joined them together using a scarph joint.




Than I built a frame to keep it all in shape.

 

From there I decided to go with rigid expandable foam and build a rough shape of the cabin. I did this using plain old cardboard to build walls and pour the foam in. When pouring foam use any sort of pva sheets or tape to cover areas you don’t want the foam sticking to, this stuff will stick to almost anything and the only way to get it off is to sand it off. Once the foam was poured and dried I went around the edges with a hand saw and roughly cut the shape I was after.

 

I went back and forth deciding how the shape will look with the rest of the boat.

 

Next step was adding draft to the sides of the cabin this was for aesthetic reasons as well as construction reasons, as at this point I haven’t decided how I was going to fibreglass the whole thing. I was tossing between constricting it using a mold or just build a moldless form. If I decided to go with the mold having draft to the side would help me pull out my part from the plug. Anyhow I got a little creative and constructed a little CNC like jig powered by a drill.

 

By pressing the jig against my plywood laminate and sliding the drill up and down I was able to get pretty smooth, even and consistent draft along the whole form.

 

Getting interesting ! Looks like a dry hull that one.

 

Length of the cabin was important in order to get the proportions looking right but this was difficult without having the windscreen.

 

I tried making a wooden frame substituting a windshield to give me a rough idea how it would look but that didn’t work too well. So I went out and bought one.