Hard dodger materials

[cxz]

Hi,

I am planning on building a doghouse/hard dodger this Winter. I am thinking of using Divinycell H45 15mm (Is this the same as PVC foam core?) for the inside and then use bi-axial glassfiber cloth or twill. Something like this:
https://hellers.dk/shop/243-polyeste...nycell-h45-gs/
https://www.hfmarine.dk/glasfiber-bx-450-gr-br-1270-mm
https://www.hfmarine.dk/glasfiber-ew...ll-1000-mm-1-m

The full list of glassfiber is here, all in Danish sorry:
https://www.hfmarine.dk/catalogsearc...t/?q=glasfiber

The question is - what specifically do I need? Should I use 15mm or 10mm for the core? Bi-axial vs twill or something else? 450g vs 200g? I want it to be structurally sound, but still keeping weight down. I may use bits of wood or aluminium stringers to support the layup. It should feel firm and strong since there will probably be a solar panel and hand rails on it. Possibly even the main sheet and traveller in the future. I prefer it to be functional over beautiful, but with an aim to try and dress it up nicely anyway.

Thinking of making a small mould out of the Divinycell (what is Polycore by the way?) and 3 layers of glassfiber. Later cutting out the holes for the windows.

Any input appreciated.

[Allied39]

Which ever choice of the dozens of different designs/materials/processes you choose....step one is deciding if mainsheet and traveler will ever be a part of it, because that turns it into a very different animal.

If you search this forum there's loads of threads with loads of different ideas and ways different folks have approached this very issue.

[Scubaseas]

Please read Dave Gerr "The Elements of Boat Strength: For Builders, Designers, and Owners" which can answer all your questions.

My personal preference is biaxial one layer 45* one layer 90* one layer veil mat to hide print through. Repeat as necessary for loads. How much you need to calculate what your loads would be and span distances. Mainsheet traveler will immensely complicate things but is doable.

[Benz]

10mm Divinycell, biaxial fiberglass, with twill or woven cloth as the last layer.
Polycore is polypropylene, and will not be as easy to work with for the beginner as Divinycell.
How many layers of fiberglass you need will depend on the size of the structure: you should consult with some local engineer, especially if you need to keep weight down. It may be you can have targeted reinforcements to maintain the strength/weight ratio you need.

[cxz]

I've now ordered about 35m2 of biaxial 450g/m2. I calculated the total area to be roughly 32m2 with 3 layers on each side of a panel. I got some extra leftover since I don't feel like playing tetris with the cut-outs and will use the spares for a small test-run. Now I'm thinking about the Divinycell and going with 10mm as Benz said. However I do find that it can be quite expensive. Are there cheaper alternatives? Or a good EU supplier?

[Scubaseas]

Marine plywood is cheaper but heavier than foam core. Polycore (propylene honeycomb coring) is marginally cheaper at my supplier in the USA but it's more "bendy" than Divinycell. Perhaps your project is small enough that the price differential of the core material will really be negligible. The Divinycell is easy to work with and light weight. It's a boat. It's supposed to be expensive.

I like this stuff. https://www.lbifiberglass.com/produc...eycomb-panels/

[Matt Johnson]

An option that works well is to double up the core around the parameter of the top's edge along the inside. The double core makes for a more rigid structure, but it did two other things; it allowed me to run conduit within this area for lights, and it also gave a nicer edge with a larger radius (for when you hit it with your head).

You could also do it along the outside as a drip guard to prevent water pouring off the back down your jacket.

Cut 75mm wide strips with a nice inner radius. Cut a channel on the inside for the conduit, then bond those to the top. Radius the edge and then glass.

Matt