supagal vs hot dipped - f/up from post 13927 on campers

Submitted: Friday, Jun 25, 2004 at 16:46
ThreadID: 14128 Views:17927 Replies:4 FollowUps:0
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Noticing that there are more camper trailers advertised now than makes of tyre I thought some bias research on supagal vs hot dipped gal needs to posted and archived.

Supagal is galvanised inside and out by BHP at the steel mill. In other words the galvanizing is integral to the product and not relying on a coating. The other thing is that Supagal is HIGH TENSILE as different from most camper trailers makers who I understand use a mild steel chassis. High tensile is MUCH stronger and will flex where mild steel will break.

Some makers use a laminated (i.e. double layer) chassis because it is stronger than the same size in a single beam, e.g. a laminated beam in timber is always much stronger in a roof or floor support situation than a single beam.

You should not use a laminated chassis in blue steel and then have it hot dipped galvanised as the liquid gal will not flow between the two chassis laminations. They will eventually rust out as water enters the area between the laminations.

Some supagal chassis are also progressively laminated, i.e. it is thicker in the middle where the suspension is and thinner at the front and rear where the weight is less. This way the chassis is as light as it can possibly be but also very, very strong and totally rust free.

Yes it is quicker to make a single beam chassis and then ship it off to the galvanisers but the down side of this is that the galvanising adds weight, sometimes over 50kg. You may notice that these trailers are sometimes smaller in body size than a supagal build but weigh the same.

On most supagal built trailers the body is welded to the chassis which creates a very rigid structure. Usually with a galvanised chassis the body is usually bolted on thus creating a weak point. Also used on some supagal trailers is an upper chassis, similar to monocoque construction in motorcars. The internal baffles inside the trailer supply rigidity to the sides and body structure eliminating flex in the box section. This ensures the seals do not shift on one another. Once the seals start moving, dust can get in.

Most campers today are built in the same way as they were designed 25 years ago. Comparing a supagal built camper to hot dipped campers is like comparing a 25 year old car to modern design. While this may sound like a bold claim a debate re gal and supagal chassis may not be worth bothering with as you or something on your vehcile will prob die first before the chassis on your camper goes!

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Reply By: Member - Ron H (Int) - Friday, Jun 25, 2004 at 17:07

Friday, Jun 25, 2004 at 17:07
hi oddy
my understandingis that supagal may be a electroplated type of coating and is hard to weld, the coating needs to be ground off to prevent weld contamination this means the weld which is the weakest part is then only painted over which can then be chipped and rust also the supagal can be chipped of by stones therefore needs painting on and off forever !!!! sorry but give me hot dipped galvanising everytime
regards
Ron
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Reply By: Lone Wolf - Friday, Jun 25, 2004 at 17:21

Friday, Jun 25, 2004 at 17:21
Thanks for the post.

I am still worried about using C350 or C 450 over C 250.

Trailers are dynamic, not static.

Good post.

Cheers

Wolfie
AnswerID: 65081

Reply By: Member - JohnR (Vic) - Friday, Jun 25, 2004 at 17:29

Friday, Jun 25, 2004 at 17:29
Sounds like a marketing pitch to supagal rather than a heavy duty approach which would last. I know though it is difficult to galvanise some high tensile steels. One guy locally had sections just crack out. Was a good way to understand what happens when you heat sections of steel. Literally exploded even though was not hollow.

It would be interesting to see a comparison in the thickness of the zinc on the comparitive products. Gal would be thicker and more durable for an anti rust finish.
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Reply By: Member - Mik - Friday, Jun 25, 2004 at 18:27

Friday, Jun 25, 2004 at 18:27
Hello oddy, sounds like you have spent some time looking into this subject and you have some very good points, but i must agree with Ron concerning the grinding prier to welding. All these pre galvinised hollow sections ( duragal, galtube, supergal) contain at least 10% aluminium and 10% zinc. If the coating is not removed prier to welding it will produce a low grade weld. In the end the trailer will rust. Hot dip galvinising is the only real sure way of protecting steelwork.
If anyones interested, www..smorgonsteel.com.au/tubemills/ content/brochure/docs/MSDSSupaGal.pdf

Cheers Mik

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