My husband and I are re-building a 26’ racing yacht. 

The below deck hull is almost complete;

• three bulkheads, 9 mm marine ply
• 9 layers of biaxial glass 420g/m² from the water line to the topside
• 8 layers of carbon twill 650gsm on keel floor
• 6 layers of carbon twill 650gsm through the center line up to the water line
• The strengtheners and longitudinales are foam core with six layers of 300gsm biaxial carbon and 10 layers of unidirectional carbon tape

All the carbon (with the exception of the unidirectional tape) is vacuum bagged.
Here is where we can use some advice:

We are preparing to build a plug to lay the deck.  We are anticipating using 4 layers of 300gsm carbon with a 10mm foam core.

Our initial idea is to build a wooden frame to act as a skeleton (see photo) and cover in polypropylene sheeting to act as a mold to lay the carbon foam sandwich.   Although we would love to use the resin infusion process, we don't have the experience on such a large area.  So feel we will have to vacuum bag.   My initial thought is to bag one layer of carbon with the foam to get a curve and then repeat the process to add the additional layers of carbon.  

If anyone has done something similar your advice is appreciated.

Hi Kittie,

I've just emailed you to the same effect but the principle of the deck moulding is certainly sound, however, if you are going to resin infuse the final product, you need to ensure that you have a full vacuum and this means ensuring a good seal between any sections of the Polypropylene sheet (assuming it won’t be done in one piece). As long as there aren’t any gaps between the sheets of polypropylene, you could achieve this with a strip of Flash Release Tape; this will span the seam whilst ensuring the same release properties as the PP itself.

Infusing such a large area comes with some issues but nothing insurmountable – the Palmer Johnson Supersport 48m yacht was fully infused after all – the first will be ensuring you have a pump which is suitable to maintain and indeed draw vacuum over a large area; in addition planning the resin inputs (You’re likely to use multiple resin feed points) and the runs of spiral will all need to be pre-planned to ensure a successful infusion but we should be able to guide with this.

I note you say a foam core; don’t forget foam doesn’t have great crush/compressive strength and so you may need to consider hard points in any through-bolting or loaded areas; with the foam decks I used to plan, we would have hardwood pads in place of the foam in any areas that we knew fixings would pass through (such as cleats, etc.).

Its certainly right to be apprehensive given the scale but with planning, it should be more than achievable.

With such a clean simple deck camber you could do this part by laminating one side (underside) of your foam core off the job. Let this cure.

Then lay your foam over your deck frames shown and fix down temporarily, then laminate the top side of the foam which will lock in the deck shape.

Fill and fair.

No molded surface needed. You might also add a few longitudinal stringers to the frames/jig also?

+x

 

Fasta - 3/10/2019 1:20:31 PM

With such a clean simple deck camber you could do this part by laminating one side (underside) of your foam core off the job. Let this cure.

Then lay your foam over your deck frames shown and fix down temporarily, then laminate the top side of the foam which will lock in the deck shape.

Fill and fair.

No molded surface needed. You might also add a few longitudinal stringers to the frames/jig also?

Fasta, thank you very much for the advice. I will let you know how we go.  We are currently putting wheels on the cradle to move the hull out of the workshop to give me more space to work.  I'll let you know how we go.