Aluminum Trawlers - Pros and Cons

I found the steel trawler thread interesting and thought aluminum could use its own. Seems like galvanic corrosion is the biggest con. I think bare aluminum is a compelling material for boats. My wife, not so much, so what about painted aluminum? ...and other unique to aluminum questions.

Having owned a 50’ Aluminum trawler, worked for a major aluminum yacht builder, and Captained several large aluminum boats it is my first choice for a construction material. Vastly stronger than grip, easy to work with and repair. Resistant to impact. The only negative I see is that it doesn’t like to hold paint. But then why paint it. The major maintenance item on the yachts was paint. Aluminum does not like to have a trapped combination of moisture and air remaining on its surface. Moisture beneath paint is the major source of corrosion. Second to that is a failure to isolate dissimilar metals.

I’m a fan, although I should be since I have a 42 footer built in aluminum. I’m in the bare aluminum court. My boat is currently painted but would need a complete strip and re paint to make her look good painted again so I’m just going to strip the whole thing above waterline just keep the decks painted for nonskid.

Btw my boat is from 72 and there is very limited corrosion in one spot due to some stray current. Only replacing about a 1 foot by 2 foot section then she will be good as new. Im a big fan of aluminum though, even being vastly overbuilt in have a fairly light boat, according to the factory specs dry weight is 18,000 lbs which gives me the ability to add the weight elsewhere, like the massive 1200 gallon fuel tanks.

I don't know very much about this subject. However, I can comment that the Fire Department I used to work for had 5 aluminum (approx. 40 foot) fireboats that over the years, all had large (meaning expensive) corrosion problems and cost thousands of dollars to repair (some several times). "Experts" were hired to determine the cause and rectify the underlying issues with limited success. I can't speak to "other" aluminum boats, but I can comment on the experiences of dealing with these (5) boats.
As an aside, I know several people who own aluminum pleasure boats who I think are quite happy with their boats. It seems to have worked out well for Jmarsh203.

I have owned a few aluminum boats and I love them. In my experience they do not have corrosion issues under water if they are set up right electrically, and have well maintained epoxy barrier coat system. The place they have problems is inside the hull where standing water is allowed to collect and sit. My current boat had an area in the lazarets that was not sloped properly and a small amount of sea water would sit in the bottom which caused problems that had to be fixed with media blasting, welding, and epoxy coating. The interface right at the edge of the water and air seems especially problematic. I am also a big fan of having an aluminum boat with no exterior paint. Although watching YouTube video's of Laser cleaners, makes me think paint might not be so bad in the future, if the price of these systems comes way down. For custom one off builds, I can't believe any boat is ever made out of anything but aluminum. Welding together a few machine cut panels seems so much easier than all the mold building, tabbing, fairing, painting, etc that it would take to build a one off custom boat. Different situation if it is a production boat, and all the molds are already built and ready to go.

The other huge thing I like about aluminum boats is that so many of the deck fittings, handrails, cleats, etc can be welded on and it is very easy to have a deck with zero leaks, and no maintenance to keep it that way. And if you do have a leak, there is nothing in the deck to rot.

We have our 50' aluminium powercat so obviously we like alu.
Many pros - strength for weight, impact resistance, ease of fixing dents/problems, no thru-deck fittings needed usually, no painting above waterline.
Cons are - lack of insulation, initial expense, need a floating ground electrically, treat metal contact carefully.
I think it was Jimmy Cornell I read recently say he'd not seen any actual dissimilar metal problems (the dropped penny argument) in many years of boating.

Also note there's a couple of construction methods - ours is Strongall made by the Meta shipyard in France: 12mm hulls, 6mm deck, all with no gussets or stringers.

“need a floating ground electrically”. What do you mean by this?

Anyone here have one of strongall construction?

Strikes me as interesting that both in power multi and ultra narrow power the Aussie NAs and builders seem ahead of the curve. Many of the rest of multis seems to be a sailing design converted to power. The need for reserve buoyancy aft and other power specific requirements would seem to benefit from a clean piece of paper.
Looks like a excellent boat McA.

Given the rarity of aluminum-hulled boats frequenting salt waters, ... ???

Weight is the most prominent feature of the rec trawler type.

So it would seem that a heavily built aluminum trawler would not suffer from being too light do what trawlers do. But a light trawler wouldn’t perform best out on the water. Yawing tendencies and inertia tendencies will limit the ability for the boat or occupants to gracefully continue long trips. Long passages in light boats frequently are less than ideal.

The ease of welding steel (if the trawler does part time work as a passagemaker) may make steel more desirable for such applications.

Otherwise if an aluminum trawler is heavy (like other trawlers) it should be fine.

Edit;
Another thought is that most aluminum boats are probably spec'ed for aluminum to save weight. Weight for performance. Some trawlers could gain from being light as when you get close to hull speed lightness is a good thing. But many boats light enough to benefit may not be trawlers.

Eric what do you think of the new breed of super efficient Aluminum power passagemakers? Their safety factors in terms of AVS, Gz curves , down flooding risks far exceed what was commonly available in older grp designs imho. Add in major improvements in efficiency, impact resistance, light ice capabilities what’s not to like? I’ve not had the opportunity to travel on one but the reviews are outstanding concerning quality of the ride in a seaway. Yes it’s a change in paradigm. Weight (other than dedicated ballast) is non productive in this way of thinking. It’s not considered to add to comfort, efficacy, seaworthiness, available payload or other favorable attributes with these designs. I agree with you that a 50,000lbs 40’ trawler is a thing of substance and beauty. Even that with solid grp hulls prior hull designs the substantial weight of some rec trawlers is reassuring but the opportunities Al presents allows you to explore a different way to think about weight and design.

markpierce said:

Given the rarity of aluminum-hulled boats frequenting salt waters, ... ???

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Rarity? Most of the fishing fleet in the PNW appears to be aluminum. Anything from 12' to 80' or so and less than 20-30 year old. Tens of thousands of them at least. Lots of aluminum sailboats too.

The problem I have is that it is difficult to keep paint on, and if you leave it bare, if you touch it, lean on it, sit on it, you will pick up oxides.

Aluminum is the material of choice of larger boats, although the largest tend more to steel hulls and aluminum above. However, in boats being sold in quantity as production boats, especially moderately sized boats, fiberglass composites are just less expensive to build than aluminum.

Now, forgetting the cost efficiency of duplication, I find aluminum to be a nice material. Like any boat, I'd want a very careful survey of older models by surveyors skilled in aluminum. Simply their condition would be very highly variable based on maintenance and care.

I'm curious about the thread title being Aluminum Trawlers because my preference for aluminum over steel is a very non-trawler reason. I want the speed. I want the planing ability.

The majority of the A-List of yacht builders, build in aluminum. Fiberglass construction has extended to over 170' though and likely 200' not far behind. However, most buyers of very large boats want them totally custom.

So, I guess my feeling is I have nothing against aluminum for a trawler, but I'd be hesitant to pay the extra cost over a production fiberglass model. Now as the cost of aluminum vs oil swings back and forth, when oil and fiberglass return to peak prices and if steel and aluminum prices were to normalize without tariffs, then that entire equation would likely shift.

I think it's good to see this thread with happy aluminum owners. Of course there are many happy fiberglass owners. As a fiberglass owner, the nicest thing I can say about aluminum is that I've been on aluminum boats that I would have never known were aluminum. We may one day own an aluminum boat. There's nothing that would discourage us from doing so. In boats up to 130' or so there are far more fiberglass than aluminum, but over 130', I can only cite two or three builders of fiberglass boats I'd consider and dozens of aluminum builders.

I never specifically set out to be a member of Club Aluminum, and I'm still fairly new to it, but so far I'm quite happy. Mine's a 1985, and I have yet to find any corrosion issues anywhere. I had the hull sonogram tested with the survey, and she's still as thick as the day she was launched. She's painted, but there are a few places on deck where the paint has started flaking away. I'll eventually repaint her, but it's not terribly high on my list of priorities. She's a little lighter than glass or steel boats of the same length, but she's still around 30,000 lbs. with all my junk aboard.

Aluminum boats are ubiquitous around here (Campbell River BC); sportfishers, water taxis, rec boats, commercial fishboats. you name it. The commercial vessels tend to be bare whereas the pleasure vessels are covered with decals along their sides, and within the last year a couple have taken residence at the dock that are fully wrapped from the waterline up.
I like the simplicity of the bare hulls, but do find that they disappear in a number of lighting conditions. One relatable example was a few years back when we had 3 Dashew FPB64's cruising the area. Every time I saw them out on the water they just suddenly appeared up close out of nowhere.

SeaLion said:

“need a floating ground electrically”. What do you mean by this?

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I'm not best, but others have commented. I quite like
Morgan's Cloud.

Hippocampus said:

Anyone here have one of strongall construction?

Strikes me as interesting that both in power multi and ultra narrow power the Aussie NAs and builders seem ahead of the curve. Many of the rest of multis seems to be a sailing design converted to power. The need for reserve buoyancy aft and other power specific requirements would seem to benefit from a clean piece of paper.
Looks like a excellent boat McA.

Click to expand...

Thank you .
There are not many Strongall boats around. The Banana cats are from ProMeta (a Meta yard offshoot), and there are a number of oneoffs. Inautia and yachtworld and others have various monos and multis for sale as well.

The powercat market is pretty solely for the charter markets (Leopards and FPs). Most others are one-offs. Although it sticks in an Australian's craw angel NZ has a pretty amazing track record (Malcolm Tennant, Roger Hill, the FPB's, Pachoud, etc).

I agree about the clean piece of naval architecture paper - we have 2x135hp Perkins. Fantastic NA diesels on straight shafts. But they weigh 600kg each without oil or gearbox or all the other paraphernalia! You want to design that weight to be in the right place or your boat isn't going to float well .

Friend is stripping/grinding/sanding the paint off of his Al trawler down in Indian town Florida. Says it’s a bear to do it but looking forward to having zero maintenance topsides.
Says it actually pretty. Awaiting snaps to see it.

Alu is wonderful. Here are a few things one can do if youre worried about: galvanic corrosion.....apply the measures that prevent it. Paint: apply 'best in the art' inatead of juat slapping on paint. Hull thickness: inatead of buying a thin alu hull boat, get a thick one , like the Stongall ones, or have one made half an inch thick. Insulation: most already have good insulation, and various insulation systems can be done.
Basically , there are no valid cons about alu boats.

mcarthur said:

We have our 50' aluminium powercat so obviously we like alu.
Many pros - strength for weight, impact resistance, ease of fixing dents/problems, no thru-deck fittings needed usually, no painting above waterline.
Cons are - lack of insulation, initial expense, need a floating ground electrically, treat metal contact carefully.
I think it was Jimmy Cornell I read recently say he'd not seen any actual dissimilar metal problems (the dropped penny argument) in many years of boating.

Also note there's a couple of construction methods - ours is Strongall made by the Meta shipyard in France: 12mm hulls, 6mm deck, all with no gussets or stringers.

Click to expand...

Regarding insulation, I saw a few Dashews being built. Very early in the build process they layered in a black thermal product for not only insulation but condensation mitigation. Can't do it as easily with steel as the insulation becomes a moisture trap.

Condensation is an issue in FRP hauls as well thus our need to run de-humidifiers.

Sunchaser......Yes, one should apply the system that works, and indeed, for humidity there are de-humidifiers, airhandlers, etc. All hull materials have good and bad points, including wood and cement, carbon fibre.

I sent this in a message to someone a while ago:

Aluminum is amazing but not painted; painted aluminum is fine until the coating is breached, then you get runaway corrosion under the paint, a bunch of white powder and the metal is disintegrating. Paint over a seam and the boat flexes in a stiff sea and the coating is breached. Even attaching something to aluminum, with the salt air, the attachment acts like a coating (keeping oxygen from contacting the metal) and it will corrode too.

There are only two choices: rigourously chase the cracks, remove the coating, sand away all the corrosion and repaint. Or get all the paint off. Aluminum, uncoated, turns a gloomy grey colour that many owners want to "fix" but if you polish, blast or use chemicals to remove the top grey coat, it will immediately turn grey again. It's that grey coating that protects the metal.

If you use fasteners, aluminum nuts and bolts (I have some) are just not good enough structurally so you'll end up using stainless steel. Use 316 anywhere outside and coat the bolt with neverseize (there is another product that protects from corrosion but the name escapes me) otherwise it will make a corroded mess and the bolt may permanently gall.

Insulate all aluminum that appears in the inside of the boat as it will collect condensation and soak the interior. For example, if you mount something through the finished ceiling and don't insulate the fastener, it will drip like a tap. I had a hatch that was lined with carpet. I thought it was awful and I pulled it out. When I returned the next day, my bed was soaked as the condensation had dripped on the bunk.

Wet aluminum decks are lethally slippery in bare feet. Al decks get very hot, bare feet will burn.

Al water tanks are hard to service, you should NEVER use chlorine in them.

You need to be very careful of the anodes, you will need more of them than a glass boat and they have to be welded on. I buy aluminum strap/aluminum anodes, they last about 30% longer than zinc and are still cheaper. I have 18 and 2 shaft anodes on my boat.

You should have an isolation transformer for your shore power so you can't put stray current in the water and you are less likely to electrocute someone.

Bottom paint: unless you have an epoxy barrier coat, no copper!

I love the aluminum on my boat but it will never have a "yacht" finish. I'm good with that.

There are other things like foamed bilges...



If I think of anything more, I'll pass it on.

Xsbank......Yes, and thank goodness that Garcia Yachts and ALL othe alu boat builders took your advice on your points and mine. And indeed, they even thought of non slippery deck plating. I like the kind with the criss cross pattern.

Aluminum has quirks but I personally will never have a glass or wood boat again, although steel is still in the running. Once you get to use the boat and understand her uniqueness and it finally sinks in that you can throw away your paint brushes and varnish (maybe useful inside?) and you only need a product like 30 Seconds to clean the entire boat, you get used to the strange noises it will make as it flexes in a rough sea, you will realize why an aluminum boat is probably twice the cost of a fibreglass boat.

An isolation transformer is essential.

It will be very difficult and time-consuming to keep a "yacht finish" on painted aluminum; I urge you to chase corrosion whenever you see it. Also, any copper used on board should be inside insulated wire or on the bottom of pots. If you use Neverseize, make sure it's not the copper one.

I spent a long time redoing plumbing, electrical, removing bunks and putting in beds, lighting, painting inside, you name it. Outside I rebuilt the windlass and did some rigging but largely the outside has remained untouched.

Look for a pro welder with a good reputation as you will need to attach anodes and repair things. I have a cracked weld on a handrail that I'll fix in the Spring. I did do a welding course or two but finding 240 volts on a dock is rare (you need lots of heat to weld aluminum, my welder won't do it on 120) and getting an argon bottle to the boat is a chore too.

An advantage of a scruffy finish on an al boat is that you become the bull in the China shop. Because I am a single, no thruster boat, I have been known to place the bow of the boat against the dock and just power around to switch directions. I have also put the bow on a smooth rock outcrop, left it in gear with the autopilot on and disgorged passengers over the bow. Once, while leaving the fuel dock in Nanaimo in a 30 knot wind I lost control of the bow and it swung into a steel piling. Clang! I woke up the guys on the fuel barge, who subsequently pushed me off but despite my acceptance of the first mark/dent/divot I expected to have my name on, there wasn't a mark!

Another advantage of the grey look is at anchorages, most boaters are not at all sure what sort of denizen might emerge from the wheelhouse so most choose a spot well away from us, which is perfect. When I enter an Anchorage and do my thing, the surrounding boat owners all stand somewhere obvious with their hands on their hips and a "there goes the neighbourhood" expression because the lump is unusual.

Messed up

Xsbank..........Cost? If one cant afford any particular boat, thats not the boat for him. Paint? Already dealt with....no paint needed, or if you want it,,,then do it the correct way. All your other points already dealt with too, and are taken into account by all those aluminum boat builders like Meta Yachts, etc.

Checker plate is awful on bare feet and will still be slippery when wet. Work boots are fine. We are talking recreational boats? I vapour blasted my decks and they are non-skid now, wet or dry and good with bare feet. They are still as hot as running to the water across a sandy beach in the tropics. I burnt the soles of my feet last summer and it took ages to heal.

I don't care about builders and if anyone is contemplating building one or having one built, do your homework.

Painting aluminum is great if you have deep pockets (or a crew) because the consequences of a coating failing are much more dire than plastic and even worse than a wooden boat. Paint is fragile and will fail, plan to repaint as often as you would a crappy set of lawn furniture. Or get a crew. I cancelled an order for a very nice al runabout that would have been ideal as a tender for my boat, but the manufacturer would not sell me one unpainted.

One of the main virtues of aluminum is the low maintenance, so why paint it and ruin your leisure?

David Ess said:

Alu is wonderful.
Basically , there are no valid cons about alu boats.

Click to expand...

Xsbank said:

I sent this in a message to someone a while ago:

Aluminum is amazing but not painted; painted aluminum is fine until the coating is breached, then you get runaway corrosion under the paint, a bunch of white powder and the metal is disintegrating. Paint over a seam and the boat flexes in a stiff sea and the coating is breached. Even attaching something to aluminum, with the salt air, the attachment acts like a coating (keeping oxygen from contacting the metal) and it will corrode too.

There are only two choices: rigourously chase the cracks, remove the coating, sand away all the corrosion and repaint. Or get all the paint off. Aluminum, uncoated, turns a gloomy grey colour that many owners want to "fix" but if you polish, blast or use chemicals to remove the top grey coat, it will immediately turn grey again. It's that grey coating that protects the metal.

If you use fasteners, aluminum nuts and bolts (I have some) are just not good enough structurally so you'll end up using stainless steel. Use 316 anywhere outside and coat the bolt with neverseize (there is another product that protects from corrosion but the name escapes me) otherwise it will make a corroded mess and the bolt may permanently gall.

Insulate all aluminum that appears in the inside of the boat as it will collect condensation and soak the interior. For example, if you mount something through the finished ceiling and don't insulate the fastener, it will drip like a tap. I had a hatch that was lined with carpet. I thought it was awful and I pulled it out. When I returned the next day, my bed was soaked as the condensation had dripped on the bunk.

Wet aluminum decks are lethally slippery in bare feet. Al decks get very hot, bare feet will burn.

Al water tanks are hard to service, you should NEVER use chlorine in them.

You need to be very careful of the anodes, you will need more of them than a glass boat and they have to be welded on. I buy aluminum strap/aluminum anodes, they last about 30% longer than zinc and are still cheaper. I have 18 and 2 shaft anodes on my boat.

You should have an isolation transformer for your shore power so you can't put stray current in the water and you are less likely to electrocute someone.

Bottom paint: unless you have an epoxy barrier coat, no copper!

I love the aluminum on my boat but it will never have a "yacht" finish. I'm good with that.

There are other things like foamed bilges...

Click to expand...

If there were a perfect boat building material, you would not see boats built of anything else.

I was cutting and pasting some p.m.s so I might have become repetitive. I figured that 7 years of owning an aluminum boat might provide some useful information for someone but I guess that person isn't here.