DIY Boat Hardtop Build Part 1: Planning, Nidacore, and Building the Base
This is the first part of my DIY series on building a custom hardtop for my boat that will eventually hold solar panels, lights, and even help with capturing rainwater. In Part 1, we go from idea to structure: planning the design, buying the materials, and building the base and underside of the top.
If you want to watch the full build with all the details, you can see the video here:
👉 Watch Part 1 of the Hardtop Build on YouTube
Road Trip for Materials: Picking Up the Nidacore
The project starts with a run down to Fort Pierce with my buddy RJ to pick up the Nidacore panels and supplies I needed for the top. Nauticore is a lightweight composite core that works great with fiberglass — strong, rot-resistant, and perfect for a hardtop that needs to stay light but stiff.
While we’re there, we talk with the shop guys about:
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The thickness of the core
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Using epoxy vs polyester resin
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Picking up a bag of silica to thicken resin for glue and fillets
The goal: build a top that’s light enough to handle, strong enough to walk on, and solid enough to support solar panels and rails.
Laying Out the Design and Frame
Back at the shop, I start laying out the overall shape and size of the hardtop:
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Measuring the boat to decide how far forward and aft the top should extend
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Making sure there’s good coverage for shade and weather protection
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Planning where the stainless uprights and support points will eventually land
A strong base is everything, so I build a framework to support the Nauticore panels. This frame helps:
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Keep the top flat where it needs to be
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Allow a slight bow for water runoff
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Give solid edges for attaching trim, glass, and hardware later on
Cutting and Fitting the Nauticore
Once the frame is ready, it’s time to start cutting the Nauticore sheets:
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Marking and cutting panels to match the shape of the frame
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Dry-fitting everything first before committing with resin
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Making sure joints and seams land in smart places for later fiberglass work
The panels are glued down with resin thickened using silica, forming a solid, bonded core. This becomes the “skeleton” of the hardtop.
Glassing the Underside
Before anything else, I focus on the underside of the top, because that’s what you’ll see every time you’re standing at the helm.
Steps include:
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Applying fiberglass over the underside of the Nauticore
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Making sure seams are well-covered and smoothed
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Building up enough layers for strength without adding unnecessary weight
I take more time on this side because:
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It’s visible from inside the boat
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It needs to look clean and finished
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It will eventually get a carpeted or headliner-style finish for a nice interior look
Adding the Underside Finish
After the glass cures, I install the carpet or headliner material on the underside:
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It helps hide minor imperfections
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Gives the interior a softer, more finished look
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Provides some sound deadening and a bit of insulation
By the end of Part 1, the underside is fully built, glassed, and finished, and the structure is ready to be flipped so we can begin work on the top surface — which is exactly where Part 2 picks up.
Why Build a Hardtop Like This?
This hardtop isn’t just about shade. It’s being built to:
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Carry solar panels
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Support lights and future tech like Starlink
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Help manage rainwater for collection
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Change the entire look and function of the boat
Part 1 lays the groundwork. The frame, core, and underside have to be right, or everything else is a fight.
Continue the Build in Part 2
If you enjoyed this breakdown and want to see how the project moves forward, check out Part 2 where I:
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Finish the top side
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Install the edge trim and water ridges
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Run wiring
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Fiberglass and paint the top
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And finally, get it lifted onto the boat and supported with stainless uprights
