Composite Hand Layup

Hi All. First post here. Im working on my first build; a basic 16’ S&G design. Also in the process of designing my own deep vee center console around 25’ that is in its infancy, as are my small craft design skills at this point. Im clearly years away from bringing anything into fruition. I would like to build it out of composite but am wondering if a hand layup on an open mold is plausible. If so, are there any composites that lend themselves more to a hand layup?

If I were to pursue vacuum infusion, is this a fool’s errand for someone not making production boats? Without a mold, is there any feassible way of accomplishing this?

 

It's not necessarily a fool's errand but it takes a lot of effort, mental, physical and financial to travel down that road, not for the faint hearted or easily distracted. Over several decades I've designed/built a number of watercraft and enjoyed the journey; it's been a rewarding hobby. Of course I've been blessed with a tolerant and patient spouse who has usually tolerated my madness.

To actually answer your question yes it's possible to make a composite craft without molds particularly if it's mostly foam core construction. If you need the finish to match the stuff out of a showroom you are starting two or three lifetimes too late.
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Thanks, Skip. Very interesting read and appreciate your thoughts. I have been using Gerr’s Boat Strength as the basis for general sizing of members before I get into the weeds of more prescriptive guidances such as ISO or the likes. He suggests 5.5lb foam for my application. Is foam your recommendation? I also see honeycomb come up in forums as well. Price for foam surprised me at about $300 per 4x8’ equivalent sheet.

 

The first thing to consider with infusion is that it depends on a vacuum being achieved.I wouldn't recommend trying the main component of your boat as a first vacuum bagging exercise.....You could do as many others have and lay your foam over stringers while you glass the outside and it will work quite nicely.Then you get to learn how much work goes into getting a respectable finish.

Honeycomb has it's uses but keep in mind that the ratio of bond area to panel size is quite small and in the last few months the IMOCA class has decided not to allow the use of honeycomb in future boats as there have been several instances of bulkheads or other panels delaminating.Another challenge is to cover the honeycomb while not filling the cells with resin.The two families of honeycomb I have some experience of are Nomex and aluminium and they can both work very well in the correct application.They do conform best if you have a developable surface,but can be nudged a little and over-expanded honeycomb will be much more amenable.as with foam there are a range of densities and the higher the number-the stiffer the honeycomb.The good stuff won't be cheap and in that respect it is like foam and foam has the same need for more or less developable surfaces.You can find scored foam for a bit more shape freedom,which is a side benefit of the grooves as well as allowing resin to travel to a new destination.Good and suitably thick foam may be expensive,but if the need is there,you may have to buy it.

 

There are a lot of different foams out there, various materials and densities. For real structural usage the standard for years was pvc based foams divided into rigid (klegecell, divinlcell) and semiflexible (airex), I've no experience with the latter. Then san based foams were developed (corecell) and became the gold standard in more ways than one. Today the new kid on the block is pet based foam, the same stuff plastic water bottles are made of. Almost as good structurally as the pvc and san based foams and considerably less expensive. What you should use would be based on specifics of use, types and quantities of load....etc. but unless it's close to aerospace quality pet will do just fine. There's a lot of sales videos for mega million yachts under construction with pallet loads of green pet foam in the background.