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I have built several boats from Marine Grade Aluminum I very much like the Pahi 42 desine .    I do not like the idea of dagger boards,  I prefer the small keel on the Tiki desines .I was hopeing to recieves some of your thoughts on this idea . Also I have only found very little information on building a James  Wharram desine in aluminum,   just a few photos of one vessel on the internet any more info  information would be very help full.    I just purchased a new miller welder for wellding aluminum Wow it makes welding aluminum so much easyer than in the past ,   the auto settings are great .   I love building in Aluminum very fast. so light. easey to work can be cut with woodworking tools .   no painting sanding , only need to paint the interior ,   very good tensile strength many of my friends build aluminum river boats one hit a larg rock at 25 mph crumpled the bow but it did not leak he just cut out the first 4 feet and welded a new bow , I was amazed.    Some grades of aluminum are close in strength to mild steel , thank you for your interest on  this subject .

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Aluminum is so much faster and much less fuss very little sanding . painting is not required no fiberglass painting is a good idea topside and  inside because aluminum  leaves your hands and cloths black from rubbing on  it . I am sure sanding and  fiberglass work are huge in time and labor . most if not all shelving and furniture  can be aluminum as well . my self and 2 friends built 3   20 ft powerboats ready for paint in 3 weeks . you can cut aluminum with carbide woodworking tools.I just bought a Miller 211 inverter welder complete set up including Argon for 1800 dollars this will weld up to 3/8" Aluminum the welder itself weights 35 lbs previously this size of welder would be over several hundred pounds in a transformer type welder .I plan to include my welder as part of my tool kit on my boat .I learned to weld aluminum from watching videos on Youtube get a piece of scrap aluminum and spend time laying welds in a matter of hours you can be welding strong if not pretty joints .

this is the last boat I built in 2008


I see no reason not to use aluminum for all parts of a boat.   I hope to get away from useing any wood if possible even furnature . Insulation is not a problem we all fly at 40,000 ft at temberatures as low as -60F everyday in large  aluminum cigar tubes oops  do not mean to turn anyone off from flying ha ha.

Living inside a metal container in a humid salty environment without aircon might be OK for  day or two now and again, but for year after year…..no thanks.

I’m happy living inside a metal shed because it is completely lined with wood and no aircon is needed, just a fire on cold days.

Same would be true for  floating home. Of course the floating home could just move to a warm place to escape the cold, where I would still prefer to have wooden decks……like a Wharram double canoe.

In fact this idea to use aluminium hulls along with open decks offers the possibility to stay on deck and keep out of the hulls.


I much prefer  properly ventilated space in wood or aluminum but aluminum will not propagate rot, water-log or get moldy requires no maintenance because of expansion or swelling and shrinking will not splinter into a thousand pieces. O and does not require  toxic resins and glass fiber.  I have friends into aluminum jet boats that have hit rocks as big as a house at 50 mph remove there safety harness climb out a little sore and stiff get the boat home pound out the aluminum or just cut off the damage area and or weld on a new piece and yes many times they just shake it off and continue driving the boat with bow looking like an accordion. O and yes by the way no leaks .  I have one friend hit a standing wave at 40 miles an hour completely submerge the front half of the boat lost all the glass but continued on as soon as he could pump out all the water.that kind of boating is not for me . I am from Canada our silly government sell raw logs to many countries then buys back marine plywood they produce from our logs a lot of marine plywoods are more expensive than Aluminum and yes your very right all species wood  is great for heating aluminum boats as well plus the bonus it is very fire resistant except for the  missiles they use in the Falklands on Aluminum British ships

Aluminium sounds very interesting as a boat buidling material, but what about the weight of the boat for an LOA smaller than 14 m? Aluminium weighs about 5 times more than plywood and it would be unreasonable to process anything smaller than 4 mm (absolute min. 3mm) plate thickness. Has anybody tranferred the scantlings and has made a weight assessment for any of the Wharram cats?

6061 aluminum has a tensile strength of about 38,000 lbs per sq in mild steel 40,000 psi  but aluminum weights about 60%less it is amazing the stresses aluminum will take aluminum will bend and stretch much more than steel with out tearing   just look at videos of aluminum jet boats in action on You Tube there is so much information about aluminum online . I have seen sailboat as small as 15 ft built of aluminum the thickness of the aluminum I do not know  most of my experience is with 20 ft and larger power boats bottom 3/16 "sides 1/8" in   that take so much stress and pounding  that the human body gives up before the boat does.  Repairs are fast simple much faster and simpler than Wood or Fiberglass you can look up mig pulse welding process online it is so fast precise  easy . look for your self do not take my word for it but even regular mig welding has gotten so much easier in the last few years . even my 26 ft power boat with 250 hp outboard i have a photo on my page on this site bottom was  1/4 sides 3/16  I had Air Ride Seats and seat Belts for travel at 45 mph in big seas  the boat would lift completely out of the water slamming into the next wave was great fun for about 5 min even with Air Seats. I never worried about the boat but my body was a different story. As for weight I think you can use much smaller thickness of Aluminum sheet than Plywood . a 5ft x12 ft x1/4 in sheet weights not much more than the same size sheet in  Hard Wood  look at a drawing of the construction of a wood boat to the same size Aluminum boat the material thickness is so much less, the boat I last built was 26 ft x9.5 with  250 HP engine and 300 liters of fuel weighed 5000 pounds.Why are all the biggest and best sailboat  builders going to aluminum ?

 O and one more thing  I think  James Wharram Catamarans should look at making plans and drawings for there designs in aluminum. if you take a 2 ft sq sheet of 6061 Aluminum and same size in Plywood you can beat on the aluminum sheet all day you may make some  minor dents or scratches but I can tell you the plywood sheet will be destroyed I am not talking about pure Aluminum but high tensile Aluminum Alloy 6061 T6 . You can also use less expensive aluminum like 5052 for areas the require less strength .

I was thinking about using 10 in exuded aluminum pipe OD is 10.75 id is 10 in so that is 3/8in pipe wall x21 ft weight is 294 pounds294 lbs for  the  beams,  I believe these are very strong beams and could be used to store water from rainfall.  These heavy wall seamless pipe that cost 1500 each I am sure a large order for most of the boat would allow a incentive for a discount . so fare we have a total order for a complete 40 foot aluminum Catamaran at about 1000 dollars per foot for a total of

 40,000Canadian dollars or 30440 us dollars for 50 sheets of1/4in and3/16in  Aluminum plate for  2 complete 40ft hulls 4 beams and 2 aluminum masts and 2 bottles of beer I read somewhere wooden beams weight was 300lbs well 10.75 x21 ft seamless  beams aluminum 6061 pipe weight is 294 lbs each

I realize 1/4 inch aluminum  is to heavy for the topsides and shelving etc but even sheet metal formed can make very strong light furniture,  when I built jet boats we use 3/16 in for bottom 1/8in for sides and same for the  cabin. perhaps in a 42 ft catamaran one could use 3/16 for the hulls 1/8 for topsides and 1/4 for the frames . I have see  some very large dents cause from hitting rocks dents as large as  24 inches across hammered out fair in a very short time .just watch some video on Youtube of jet boat races you will be frighted and amazed at the abuse these boat can brush off.

I just found a Petral 12ft sailboat on You Tube  so there is proof you can build a small sailboat under 40 ft also mini jet boats less than 10 ft in length just look up 12 ft Petral sailboat youtube I could not upload it here and mini jetboat .

Well sure. a 12ft ballasted keelboat was built by Serge Testa, which made a record circumnavigation.

This was a monohull though,for very good reason,since aluminium was the construction material.

An outrigger canoe or even a proa might be an equally good option to build in ally.

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