Wharram style in aluminum?

I don't know much about aluminum but Wharram says something about it in the design book. The only wharrams with hard chines are the smallest ethnics although most of the bigger boats have overlaps between the topside and lower side panels creating steps along the sides above the water. I don't think tikis are faster than pahis all other things being the same; people aren't very good at making observations in general. The wharrams own boat is a pahi 63 so I guess they like them fine.

Don Dodds' "Modern Cruising Under Sail"gives some material tables along with a lot of opinions which you do'nt have to accept !! Aluminium is approx. twice as good on strength/weight but only half as good for stiffness compared to ply. You cannot substitute 6mm alu. for 6mm ply. A great little book by John Teale is "How To Design A Boat". It does the math in a simple form complete with worked examples. He even does a worked example of converting a ply skin to alu.and other materials. Allocating 100% to steel the others score as follows alu 52% f/glass 54% ply 21% Applying this to a catamaran of 3 tons [reasonable estimate for 40 ft wharram] assume hulls 2 tons other structures 1ton. New hulls 5 tons plus 1ton xbeams furniture etc.= 6tons This boat certainly wo'nt be fast !!! You could widen the hulls to carry the weight but you cannot double the sail area to recover the speed. Since the sail would be both bigger and higher you meet the original stability calculations at 40% increase of sail. Alu. is a fine material there is no reason why a cat. cannot be designed to use it but there are no real short-cuts when it comes to design. You will have to learn the math or pay someone to do it for you !! My own gut feeling is that this material would be suitable for larger designs and I think James also said this in an article many years ago. After all that, you are the alu. expert . If you go ahead do please keep us posted - I would love to be proved wrong on this one.

This topic is in the old forum: http://www.wharram.eu/cgi-bin/yabb2/YaBB.pl?num=1196432162 The first 25% is written by naysayers; the remaining excellent discussion is by people who actually built in aluminum.

Thanks for the link. A great morning's reading. Best of luck to New Dawn Fades. If he goes ahead I hope he keeps us posted.

Thanks, the link is excellent as primer, for those eager to see some pics first go here: http://picasaweb.google.com/WharramAluCatamaran There is a stunning example of customized Narai called Katipo by Don, perhaps compatible with this alu-related discussion, "Basically I increased the overall beam using lashed Tiki style beams and built a Pod with seating for up to six. This has been excellent giving shelter from the sun, rain and cold with steering wheel, engine controls and dials for windspeed. log etc all clearly seen. Visibility is great and sail sheets are all at hand. It is a good social hub of the boat too especially at anchor. You can even fish while sitting in the shade!" http://www.wharram.com/forum/viewtopic.php?p=558#p558 gallery: http://www.wharram.eu/photos/index.cgi?mode=image&album=/Classic%20Desig... Some of the pitfalls and remedies for building in alu described here (need for isolation transformer, various tips for working with alu - heat distribution for welding and preheat for bending, freq. spacing of frames and stringers, insulation, ..) http://www.milliej.com/Construction_Millie_J.html The "radius bilge hull/radiused chine" construction system can be used in alu,steel, even plywood, (Sunreef's method as well?), Millie_J's designer Ted Brewer alu designs and explaining links for Dudley Dix's system: http://www.tedbrewer.com/sail_aluminum/arden_aluminum.htm http://www.smalltridesign.com/Trimaran-Articles/Construction-Methods/Rad... http://www.dixdesign.com/radmetal.htm http://www.dixdesign.com/radply.htm How far can you push it in ply? Here radiused chine example of 55' cat DH550, http://www.dixdesign.com/55cat.htm "Cheetah" gallery (no compromises): http://www.multihulls4us.com/forums/showthread.php?t=2958 http://blog.lainecompany.com/ "Spice" sister ship sank (or one hull breach) in 2010? http://www.sailblogs.com/member/inthewind/?xjMsgID=117217 Detailed step by step blog about alu construction, many tips and workflow explained: http://alemar45.blogspot.com/ CNC files/kits - also extra construction info inside the Alumar site: http://www.alumaryachts.com/ Another great option for alu, how to drop maintanace costs a notch lower again by painting only decks and antifouling, the hulls remain bare alu, however surface polished/disk sended into pattern (repeatble after accumulating marks over the years), so building scratches/welds visible no more and no need for expensive finishing/paint: http://www.metalboatbuilding.org/phpBB3/viewtopic.php?f=36&t=194 There is a set of reasons why many of the bambillionairs are building in alu (and never look back), it's simply the best. Now, these techniques are trickling down to "lower" budgets as well. However, for bluewater cat of Wharram design it's still very experimental (no direct plans support) as the info from the few builders mentioned in that link is still very limited, in any case long consultation with someone with experience of building several alu-monohulls should be a precondition. Supposedly, Narai IV, Pahi 42 and Tiki 38 designs have been build so far.. Perhaps Wharram could team up with the pros mentioned above and offer selected designs in alu/kit. Interesting tidbits from the Sunreef guys, they are building it in Sealium® and Alustar® alloys in a welding friendly environment: dust free, low humidity and temperatures close to 15°C. In terms of quality control, they use: "All seams are inspected for failures by visual tests with a special penetrating fluid. All butt welds on the shell of the boat are checked with an ultrasound scanner and areas of highest risk of welding failure are x-rayed to be sure that everything is according to high quality standards. " I gather these gadgets can be sourced from other applications, especially the ultrasound scanner shouldn't be a problem these days;full text: http://www.aeroyacht.com/sailing-catamarans/sunreef-catamarans-70-to-150... The biggest of them "CHE" 114', bare hull structure weights aprox. 31t Launch/finishing: http://www.youtube.com/watch?v=wIRS-Ktd2rA Hull roll out: http://megayachts.ru/en/news/10/884/ Built in Gdansk (Poland), yet pricetag still ~$10m http://gdansk.naszemiasto.pl/artykul/551770,superluksusowy-katamaran-pow... Homepage: http://www.yacht-che.com/

Hi everyone ! Sorry for my bad english, I learned by myself in australia ... (I m french ...) I am an aluminium boat builder, and in love with wharram design. I am at my own business, you can see it at: [url]http://www.matthieumarion.com[/url] I weld lot of boats since at least 10 years, actually I need a bit more money to start my own TIKI 46 in aluminium. I already built 2 catamaran in aluminum noanoa46 and galileo41 And I built lot of boat with big thickness aluminium plates like the switch and glue method (we called it in france STRONGALL) I am sure wharram style in aluminum is not a problem. Of course the original design need some adaptations. I think for myself the lower part of the hull in alustar 8mm, and the top of the hull in 6mm, the deck in 5mm. And no structure inside. It's very quick and easy to build and weld. I estimate about 2 tons each hull, it's closed to plywood epoxy ... If someone has questions about aluminium, (and if I understand question ...) you're welcome.