Tips For Buying A Welded Aluminium Boat
- Buy direct from the manufacturer. If you buy from a dealer, the price will include a 15-30% mark-up. If the price is comparable, the boat you get will likely be made of inferior, cheaper material. The finish may look great but you buy an aluminium boat for its durability, not its great-looking carpet, decals, and beaded upholstery.
- Ideally, for a saltwater boat the hull plating should be 1/4" (6mm) for the transom and bottom and 3/16” (5mm) for the sides. At the very least, the plating for the sides should be 5/32” (4mm). Once you have the plating established, check out how the hull is put together and how it is welded, including the spacing of the welds, whether the hull welded continuously inside and out and whether the hull has a keel and frames. Nothing matches the strength of a full keel welded into the hull plates if you hit a log or rock.
- The framing of a boat is very important. The framing should be done with aluminium parts welded in place to create a “skeleton” or “egg crate” in the hull. Instead of completing the aluminium framing in the hull, another way of finishing the hull is to spray foam in the air space in the hull. The foam expands into the space making a solid block. It is a good way to build a hull and some fibreglass boats are built in this manner but there are the following drawbacks:
(a) There are differences between spraying foam in a fibreglass hull and
an aluminium hull. The combination of the foam, saltwater and aluminium will cause electrolysis on the inside of the hull, which damages the hull;
(b) If a repair is required, having the foam backed up against the aluminium makes the welding very difficult. As the aluminium is heated, the foam burns and the gas created from the burning foam explodes out through the area where the aluminium is being welded.
(c) The foam can absorb up to 10% water so a 25’ hull could have as much
as 450lbs of water held in the foam. You'll notice some boats have a channel up the centre of the boat to help drain the water away from the foam. With a channel, there is less foam and less foam means less strength.
- Consider the alloys used in construction of the boat. The smaller boats we build (under 22’) are generally made with 5052, although we offer the option of using 5086 or 5083. We have built commercial boats using 5052 that have over 10,000 hours of use. Our larger boats are made with a combination of 5052, 5086 and 5083. With our boats over 24’, we use 5/16” 5086 plate, rather than ¼” plate used by some other builders. There are even stronger alloys such as 5383, 5754, and "Sealium" but cost and availability is a factor as these alloys are not widely used here.
- Get at least 5 references and don't stop asking for references until you have talked to 5 boat owners.
- Take one for a test ride. People will research and test-drive cars for 3-6 months before buying but will not do the same for a boat. There is no consumer reports for aluminium boats so it is up to you to learn what makes a boat durable and, most importantly, what will give you a safe, comfortable, and dry ride. Make sure the conditions are comparable when you test ride a boat.
- There are boat-building standards but, unlike cars, there is no testing agency to ensure that the boats are built to those standards. Once again, it is up to you and the integrity of the builder to make sure the standards are met or exceeded.
- Certification by the Canadian Welding Bureau (CWB) does not assure quality. A CWB certified company is allowed to employ an uncertified welder for as long as 2 years. As well, a welder can be certified for only horizontal weld to save
money but may be required to do vertical and overhead welds as well when building a boat.
- Make sure the self-bailing deck self bails. You don't want a boat that requires an electric bilge pump to keep it afloat.
- Some boats use aluminium frame windows for the two side slider windows and rubber trim for the rest. Rubber set windows leak after time.
- Make sure that you can get access to the fuel tank. When it comes time
to do a repair on the fuel system, the last thing you want to do is to use
an electric power tool to get access to the fuel tank.
- Consider the differences between a four-piece bottom and a one-piece bottom:
(a) A one-piece bottom is used to save the time of fitting and welding the chines and keel. By using a one-piece bottom, the builder is limited in the
shapes into which the plates can be rolled. A four-piece bottom gives more flexibility.
(b) A one-piece bottom is no stronger than a hull assembled out of different parts. The welding process weakens the aluminium plate because the temper is removed when you apply heat. This applies whether there is one piece or four.
- Aluminium cut using a computer-controlled cutting table produces a finer/nicer-
looking hull. Whereas a person using a saw can cut to within a .125” (1/8”) tolerance on a good day, a computer-controlled cutting table can cut the same piece to within .05" every time.