Forum -
October 7, 2022
A few questions
I would like to discuss the weight savings vs. cost of moving from interior constructed from plywood vs. constructed of veneered composite material. It seems excess could make their own plywood substitute with a layup of veneer/fibre/foam/fibre.
1) Massive, flushed in solar panels on the cabin roof top (ETFE type) providing over 3KW of solar power - like the H&H 44
2) Solar Powerd air conditioning. To make this a reality you need #1 above plus highly efficient AC. The two most efficient marine AC systems I know of are:
The Frigomar BLDC units:
https://www.frigomar.com/en/products/self-contained-unit-inverter-bldc/
and even better the Termodinamica Marine systems:
https://www.termodinamicamarine.com/en/system-advantages/
The advantage with the above system is 1) even greater efficiency over the Frigomar and 2) quieter 3) far, far fewer through hulls.
The idea is that you can AC the sleeping cabins at night for < 2kwh total per hull, so 4khw for both hulls without running a generator - nice a quite, no need for a generator. And if you have 3KW solar on catamaran, you can even run it during the say off solar - no generator needed, no generator noise, weight, maintenance, cost. Supplement with 200ah altenators on the engines as factory standard for when the sun doesn't shine.
8
comments
It can indeed bring some savings but those are strongly reduced by the manufacturing process:
In order to accommodate the hulls rounded shapes, the core is traditionally cut in small rectangles (typically 30x40mm). During the infusion process, the cutouts between those rectangles are filled with pure resin. This resin adds weight whichever the core material, so the ‘theoretical’ gain is highly affected by this ratio of pure resin in the final sandwich.
Apart from weight influence, in order to get structural characteristics comparable to balsa, we would need to use PVC foam, this is as costly alternative to balsa.
On the Excess range, with the complex hull side’s shapes we have, the gains of foam core would be quite small, compared to the over cost.
If the hull sides were straighter, we could consider using non-cut PVC foam core, and the gains could then be significant...
Last, but not least, PVC is a synthetic material, compared to the FSC balsa we use, and the environmental impact is also a parameter we take into account while making those decisions.
They are indeed solutions to replace the plywood by composite / foam sandwich materials. We actually do this on a some of the Excess 15 woodwork.
The weight savings can be really significant, but the cost increase is quickly very high.
The main over-cost does not come from the bare materials, but from the complexity to assemble low density panels.
In most cases you need to add some high density inserts in the foam, to ensure you can properly fix the various hardware… Those inserts make the whole process more complex, expensive, and they affect the weight gains.
On the Excess 14 accommodation, we made the decision to stick to plywood, but to reduce it to the bare minimum (reduced thickness, less pieces, hollows, etc..) (Mettre un lien vers l’article ‘modules’ des Excess 14 series)
This is an efficient way to reduce the weight, the environmental impact, and the cost – all together.
Off course this is a first step, and we keep investigating into -affordable- lighter composite alternatives…
Regarding solar panels : Yes ! On the Excess we have no flybridge, hence a huge free space for solar panels on the roof top. We have to move towards more solar panels onboard!
Running the AC without genet is indeed a smart objective!
Hard to achieve on big volume boats, but there is a size where the equation ‘volume to cool / power needed / cost of the green solution’ looks attainable indeed, at least for overnight AC…
Thanks a lot Robd for all your inputs !
Hervé