Best material for design?

[willfox]

At the mo im doing parametric research into classic yachts...pre 1960 which are all of wooden construction and comparing these to the modern classics of today. The 3 companies im looking into are Hinkley, Morris and Spirit. Spirit use Brazilian cedar where as the other use scrimp with with e glass carbon and kevlar. Spirit Yachts are definate performance yachts with high ballast ratio's (0.4 to 0.45) and Slenderness ratio's (6.5) where as Morris are much more in the Rassy, Najad, Oyster region. Hinkley being more classic oriantated with lowest slenderness, and highest SA displacement etc...


I am currently putting together my dissertation for my degree at university. I am intending to design a 'sell up and sail' classic mid 50 foot, pure cruiser intended for round the world (the right way) use. I'm really keen on designing a cold moulded vessel because I really want to learn more about the construction technique. I dont know if this is appropriate way to build this sort of yacht considering I have the option to use whatever I want! Maybe I should really be designing in composites as these have much better impact resistance which is of concern?
What would your opinion be?

[yipster]

from various yacht design books i recall material can be left to the more inner circles in the design spiral

[messabout]

And you would do well to consider marketability. In general the market will be more likely to accept composite material in spite of the fact there may be better options.

[Tad]

Well.....you are the designer so you get to decide.....steel will have even better impact resistance if that's the only criteria.

If you want to learn about cold-molded construction (or design thereof) do a cold-molded boat. As to impact resistance of composite (assume foam core) vs laminated wood.....that will depend on specific layup of each panel.

For a cold-molded world cruising boat I would go with a "thick skin" minimum framing construction method. Maximum panel length will be approximately 6.5', the length of a berth. Framing will be laminated floors, foam cored major bulkheads with laminated cleats, plywood minor bullheads (all joinery bonded or cleated to skin) laminated keelson and laminated clamp. Hull skin will be approximately 1.5" thick total, two layers of 3/8" Doug Fir inside and out running 0 degrees to CL. Core to be two diagonal layers of red cedar at +/- 45 to CL. Sheath with heavy glass outside (at least 24oz Biax), all laminated with epoxy. Deck should be thick as well, but foam cored for heat and sound insulation.

[peter radclyffe]

have you talked with, s.y.s, tony castro-was in hamble, ken latham, & maybe green marine

[Paul Kotzebue]

Originally Posted by Tad

For a cold-molded world cruising boat I would go with a "thick skin" minimum framing construction method. Maximum panel length will be approximately 6.5', the length of a berth. Framing will be laminated floors, foam cored major bulkheads with laminated cleats, plywood minor bullheads (all joinery bonded or cleated to skin) laminated keelson and laminated clamp. Hull skin will be approximately 1.5" thick total, two layers of 3/8" Doug Fir inside and out running 0 degrees to CL. Core to be two diagonal layers of red cedar at +/- 45 to CL. Sheath with heavy glass outside (at least 24oz Biax), all laminated with epoxy. Deck should be thick as well, but foam cored for heat and sound insulation.

That is a good way to build a wood boat. The numbers crunch nicely with the ABS scantling rule for offshore racing yachts.

[Ad Hoc]

willfox
"... I dont know if this is appropriate way to build this sort of yacht considering I have the option to use whatever I want!.."

As TAD noted it is for you to decide. BUT, what you need to do, is satisfy yourself with the final choice. This would go down well for your dissertation too. Since I assume you have a "nominal" structural weight form your weight estimate?...if so, then explore various methods, to see which one can be within the weight budget. If only one, then it is easy, if more than one, than you then use another design variable for your criterion. If none, then the estimates are wrong..so this is a good learning curve...