Why should never buy a Welded Aluminium Boat Trailer ?
We could answer and justify the answer to this by asking you just one simple question…
‘Have ever seen an aircraft that was welded together?'
Of course not… and that is exactly why you should never buy a welded aluminium boat trailer.
But first, let’s look deeper and explain why.
A wise man once said, ‘ Grandson, believe nothing you hear or read…... and only half of what you see.....Think for yourself and .....you will grow up to be a very wise man.’
Aluminium is an incredible material.
It is 1/3 of the weight of steel, it does not rust and generally, depending on what grade and how it is treated, is as strong, even stronger than many steels.
Used in a building, aluminium can offer a light weight solution with high structural integrity.
In windows or fridge door handles if anodised it lasts for decades and resists all types of pollution without corrosion.
There are many different types and grades of aluminium and so all grades their finish and process will deliver different results.
Aluminium can be Anodised or Mill finish.
You can easily test it by rubbing your finger on the metal.
If it is 'Mill Finish' then your finger will turn black. If ‘Anodised' your finger will stay clean.
Anodising is not a coating, it is the transformation of the base metal into a controlled oxidation, so it can never flake off like a coating could.
Anodising & Electrolysis
Electrolysis is the self consumption of a metal due to electrical currents generated by contact with another metal type and moisture.
To get electrolysis, you need to have at lease three things present.
Two metals of different nobility and a liquid.
When you have this you have a battery and like in a battery, electricity is generated and the less noble metal will be eaten away in a process called electrolysis.
However anodising the metal, not only protects it from corrosion and gives it a harder surface, it destroys the electrical conductivity.
If electrical currents can not flow then you do not get electrolysis.
When aluminium is extruded it has a hardness of T4. In this state you can easily drill it with a hand drill and it is very soft.
When hardened to T6 it can be very difficult to drill.
Grades of aluminium.
Apart from pure metal like 24 K gold, most metals are an alloy, a mix of different properties, brass, bronze, stainless steel and aluminium etc.
These different grades have different properties, and their quality of strength and corrosion resistance is identified by codes, similar to the codes used in stainless steel such as 304 or 316.
It is generally considered that Grade 6061 is regarded as marine grade and has excellent corrosion resistant properties as well as high structural integrity, if hardened.
Flex is Characteristic of Aluminium.
The most obvious characteristic of aluminium is that it flexes.
If you have ever sat in a window seat a commercial airliner and observed the wing tip on take off you will see it may flex upward to 1.5 metres before the aircraft generates lift off.
This flex is not an issue where aluminium is used in a static situation like a building, however in any mobile situation it is critically important to design and manufacture in such a way to relieve the stress of this flex.
Aline manufacturers achieve this by using a series of rivets and bolts….. never welding.
The rivets allow just enough play for the stress of flex to dissipate where as a welded construction transfers the stress to the weakest point and results in structural failure.
Most common failures in aluminium.
The most common failure in aluminium is at the welds.
There are two reasons for this.
1. Most boat trailer manufacturers buy their metal in straight lengths from metal merchants and bend it themselves. Apart from this adding the extra cost of the metal merchant, the metal is not hardened.
It can not be hardened, because if it were, it would crack on bending.
2. Welding hardens the metal at the weld, but the surrounding metal is still T4. Those of us who have seen cracked aluminium welds will recall it is never the weld that cracks, it is the metal beside the weld that cracks. This is where the soft metal meets the hardened weld.
Conclusion; A welded boat trailer suffers a similar stress and turbulence that a commercial airliner endures. When the time comes that you can board a welded aircraft, then that may be the time to consider to buy a welded boat trailer.
At Spitfire, we believe that we are the only boat trailer manufacturer in the world that manufacturers an Anodised and Hardened aluminium boat trailer. ( Please correct us if we are wrong )
The spitfire procedure for manufacturing is to extrude, cut to length, bend where desired while the metal is at T4, then brush the metal to remove factory brushing and return the production to the ovens for hardening to T6 Then finally anodise to marine grade thickness. Hardening the aluminium in its already bent shape, is metallurgically as professional as it can be.
Spitfire Aluminium Trailer Chassis, like aluminium aircraft... are not welded. The only welded part on a Spitfire trailer is the winch post and to ensure there is no mix of T4 and T6 joined metal, our procedure is to cut to size, weld, brush then return to hardening so that both the weld and the base metal are all T6, and finally anodising. This hardening process after welding, eliminates the weakness of soft and hard metal working against each other.
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