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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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The following quotes are from "Boatbuilding Manual, Fifth Edition" by Robert M. Steward, 2011:

"Aluminum, compared to wood, produces boats of about equal weight and cost where an equal complexity of structure is accepted. Wood boats offer better inherent insulating qualities, both in thermal values and in the capacity to absorb noise."

"Many builders of steel boats have converted to aluminum construction with little need to change equipment except for welding, but like steel, it is not a material for the beginner. One very important problem area encountered with aluminum construction is galvanic corrosion. This occurs between the aluminum hull and dissimilar metals found in such fittings as seacocks, propellers, shafts, rudders, etc., and it also occurs when the aluminum hull is exposed to stray electrical currents in anchorages."

"Welding and the preparation of the finished surface area are also areas that require care. Welding aluminum is quite different from welding steel. It is imperative that weld areas be absolutely clean if good welds are to be made."

I don't see a compelling reason for an amateur, backyard builder, to build a Wharram catamaran out of aluminum. In fact, my research indicates that this may be classified as a really bad idea.

Omar

Even in the last 5 years big changes have been made in aluminum welding just look at some of the latest video on Youtube  and see for yourself ill try to upload my latest boat below I built it in 3 months. I am not a welder by trade.

My latest boat in aluminum Below it took me 3 months building alone. I am not a welder by trade it is 26 ft 9ft 6 in Beam 250 hp ourboard

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Alfred.....sweet boat! I know five guys personally who built 48' alum cats as first time aluminum welders and builders. Add me that makes six. Out of the six guys, three had never cruised or lived aboard. Us other three did have years of full time cruising experience. The guy that sold me on the idea was the neophyte sailor, welder and builder. His boat was beautiful and solid. It's since hadn't many miles and years of use with a second owner.

A huge mental help, and lesson, was listening to those that had actually done it. Universally the guys said to ignore the 'experts' who'd tell you a host of reasons why something wouldn't work or shouldn't be done. And it was true, you'd run into folks bending your ear of just that. You'd maybe consider their opinion, but in the end you'd look at someone and something right there in reality that proved it worked. Often, these guys just had to make a call based on their own best guess, and experimentation. If something could be done better, or avoid an issue, the knowledge was shared. All the way you'd develop an idea of doing something different and just try it to see what happened.

Omar, respectfully, I can think of three reasons for an amateur to give an ally wharram a go - it's fun as hell, it's rewarding trying and you learn something new mostly on your own initiative and dime. I'd take a guess that maybe a reason you don't see a fleet of aluminum Wharram cats is these boats tend to interest the tighter budget end people. And, they think aluminum is either too expensive or scared off by conventional wisdom or can't take the risk financially to experiment. Also, it would be a pioneering market for resell value.

I'd be interesting to see how one would address the beams and I've thought about that over the years. As I understand Wharrams are lashed and loosey goosey on purpose. Does it defeat a point to make the cross beams rigid? If not how would one go about making the deck, beams and hulls rigid enough? I had an early 35' open bridge deck Seawind cat that had three big semi oval alum cross beams that slid into heavily glassed tubes. Each had a one inch bolt in each hull holding it in place. The open bridge deck was all aluminum with two compression stays running under the center beam/mast base. The boat was not totally rigid....you could jump up and down on one corner and the whole boat would wiggle. At first a bit worrisome, but I put heaps of open ocean miles on it, some in rougher weather. The next owner used it lightly followed by another owner who has cruised extensively. This boat was launched in 1991. So it works. I wonder if something like that could translate to a Wharram cat? Or maybe keep the bridge deck, cross beams and hull lashed? If it were me and my money I'd try to go the rigid route with those compression stays under the center beam. That Seawind was a cutter rigged sloop so there was also the inner stay running across to the hulls under the catwalk. Let's say for whatever reason a person tried the rigid route and something still flexed or failed.....ok, retro fit your beams ends to be lashed or loose somehow and try that.

It sure is nice when you smack giant soaked logs in the middle of the night inside a tin can! Or run over a metal FAD, always at night, in the middle of nowhere. If you haven't seen these picture 6-12' long x 2-3' diameter metal boiler half submerged tethered in deep, deep water.

I would be paranoid and on constant alert in a marina for stray current. I once had my alum cat in a Philippine 'marina' for six months. All I noticed was a slight acceleration of wear on the shaft anodes. Things were working as they were supposed to. Otherwise, if cruising, it's so rare you are In a marina. Just eats up too much cash and really what's the point?

Just some thoughts.......

Jay said-

"Omar, respectfully, I can think of three reasons for an amateur to give an ally wharram a go - it's fun as hell, it's rewarding trying and you learn something new mostly on your own initiative and dime. I'd take a guess that maybe a reason you don't see a fleet of aluminum Wharram cats is these boats tend to interest the tighter budget end people. And, they think aluminum is either too expensive or scared off by conventional wisdom or can't take the risk financially to experiment. Also, it would be a pioneering market for resell value."

Well, when you consider that being in just 60 degree water can kill you, maybe you should rethink your reasons that someone should give an aluminum Wharram a go. Particularly, considering you may not be the only one in the water. Any time you change the design of a boat, without the knowledge to fully understand those changes and their impacts, you do so at your own peril.

You're free to do as you please. I just wouldn't recommend it as an option for an amateur builder.



Jay said:

Alfred.....sweet boat! I know five guys personally who built 48' alum cats as first time aluminum welders and builders. Add me that makes six. Out of the six guys, three had never cruised or lived aboard. Us other three did have years of full time cruising experience. The guy that sold me on the idea was the neophyte sailor, welder and builder. His boat was beautiful and solid. It's since hadn't many miles and years of use with a second owner.

A huge mental help, and lesson, was listening to those that had actually done it. Universally the guys said to ignore the 'experts' who'd tell you a host of reasons why something wouldn't work or shouldn't be done. And it was true, you'd run into folks bending your ear of just that. You'd maybe consider their opinion, but in the end you'd look at someone and something right there in reality that proved it worked. Often, these guys just had to make a call based on their own best guess, and experimentation. If something could be done better, or avoid an issue, the knowledge was shared. All the way you'd develop an idea of doing something different and just try it to see what happened.

Omar, respectfully, I can think of three reasons for an amateur to give an ally wharram a go - it's fun as hell, it's rewarding trying and you learn something new mostly on your own initiative and dime. I'd take a guess that maybe a reason you don't see a fleet of aluminum Wharram cats is these boats tend to interest the tighter budget end people. And, they think aluminum is either too expensive or scared off by conventional wisdom or can't take the risk financially to experiment. Also, it would be a pioneering market for resell value.

I'd be interesting to see how one would address the beams and I've thought about that over the years. As I understand Wharrams are lashed and loosey goosey on purpose. Does it defeat a point to make the cross beams rigid? If not how would one go about making the deck, beams and hulls rigid enough? I had an early 35' open bridge deck Seawind cat that had three big semi oval alum cross beams that slid into heavily glassed tubes. Each had a one inch bolt in each hull holding it in place. The open bridge deck was all aluminum with two compression stays running under the center beam/mast base. The boat was not totally rigid....you could jump up and down on one corner and the whole boat would wiggle. At first a bit worrisome, but I put heaps of open ocean miles on it, some in rougher weather. The next owner used it lightly followed by another owner who has cruised extensively. This boat was launched in 1991. So it works. I wonder if something like that could translate to a Wharram cat? Or maybe keep the bridge deck, cross beams and hull lashed? If it were me and my money I'd try to go the rigid route with those compression stays under the center beam. That Seawind was a cutter rigged sloop so there was also the inner stay running across to the hulls under the catwalk. Let's say for whatever reason a person tried the rigid route and something still flexed or failed.....ok, retro fit your beams ends to be lashed or loose somehow and try that.

It sure is nice when you smack giant soaked logs in the middle of the night inside a tin can! Or run over a metal FAD, always at night, in the middle of nowhere. If you haven't seen these picture 6-12' long x 2-3' diameter metal boiler half submerged tethered in deep, deep water.

I would be paranoid and on constant alert in a marina for stray current. I once had my alum cat in a Philippine 'marina' for six months. All I noticed was a slight acceleration of wear on the shaft anodes. Things were working as they were supposed to. Otherwise, if cruising, it's so rare you are In a marina. Just eats up too much cash and really what's the point?

Just some thoughts.......



Alfred Archibald Linthorne said:

Thank you for your reply the photos I found online I believe they are from down under ill try to down load them here 

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Omar M. Rashash said:

Actually, that's only part of the answer. Even in an aluminum boat, with no electrical systems, any metal in contact with the hull, except for aluminum, zinc, or magnesium, will cause the aluminum hull to corrode. More info is available here- Aluminum hulls

Omar

Thank you for your great information but the aluminum electrical issue was resolved many years ago, yes there were problems when aluminum was first used for boats.  Spending my days siting in a marina is not my Idea of a pleasant life I prefer to anchor out . There lots of way to resolve and fears about electrolysis this a very old problem easy to resolve and boat even wood ones must have an anode to protect any metal or else .I do not know about your countries but here in Canada good trees are getting harder to find, if there are any,  they are shipped as whole logs to other countries.I get a sick feeling when I go to a specialty wood seller one piece of some foreign hardwood and not a big piece one board 2 inches thick about 4 square feet in all,  1200 dollars Ouch ! Thats a lot of aluminum 5 sheets 5ftx12ftx.250 that will never rot .I remember a time when Oak toilet seats were very popular, until they cracked and you sat on it and you jumped up so fast leaving your flesh embedded in the seat. From that day forward you always looked very carefully of what kind of material the seat was made from if wood you rather lift seat  and sit on the cold porcelain that warmed up so gradually.  

Alfred,

Check these vids out if you have time. Part one was lost. That had the bulkhead setup and bottom plate forming. Might be some ideas there for you. There's still six or seven vids of the build. YouTube sailpalauutube user ID

https://m.youtube.com/channel/UCZtq6T_kvOzyr_NsBnMQGfQ

- Jay

Aluminum is an option that might be suitable for some people.

But the numbers posted here  are goofy!!

"one piece of some foreign hardwood and not a big piece one board 2 inches thick about 4 square feet in all,  1200 dollars Ouch ! Thats a lot of aluminum 5 sheets 5ftx12ftx.250 "

 

LOL, you noticed that. I can get as much Sapele as I want locally for $5.50/bd. ft. I can get Goncalo Alves for $5, $10 if I want stripe. The only boat wood that's expensive is Teak,  starting at $30. All of this also ignores the Tiki range was designed to be built using sustainable softwood, which should be readily available, especially in Canada. After all, it grows on trees.

Omar


boatsmith said:

Aluminum is an option that might be suitable for some people.

But the numbers posted here  are goofy!!

"one piece of some foreign hardwood and not a big piece one board 2 inches thick about 4 square feet in all,  1200 dollars Ouch ! Thats a lot of aluminum 5 sheets 5ftx12ftx.250 "

 

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