Aluminum use

[surprise]

I have been looking around for various materials to use for structural support, specifically for a stand and hood frame. I know that in the boating industry aluminum is very common. Besides the above average welding abilities are there any reasons that aluminum is not used more?

[Letmegrow]

It is not strong enough to hold up a tank I would imagine.
It can also rust.
Metal reacts with salt, usually in a negative way.

[laverda]

Aluminum I plenty strong enough to hold up a tank if your stand is designed properly and it does not rust. I does Oxidize/corrode with salt water contact.

[BeanAnimal]

"rusting" is oxidization :)

Each metal oxidizes differently... but the reaction is one between the metal in question and oxygen.

[BruiseAndy]

I would say expense is the reason it is not used more frequently. Expense of the raw materials, engineering, and welding vs expense of wood.

[laverda]

"rusting" is oxidization, but oxidization is not always rusting!

[hahnmeister]

Aluminum is usually a fraction as hard and strong as Steel unless you start using them in freezing applications... then Aluminum looks like a better material. But for reefing, Steel stock seems to be the best, and to avoid rust, get it powder coated or porcelain glazed.

[Conano]

If you look at those aluminum boats carefully. After they have been out in saltwater for a time, you will start finding pits in the shell that looks like spots where the metal has started melting. This is caused by electrolisys.

[douggiestyle]

aluminum is used heavy in the off shore boating industry. it is more resistant to corrosion than stainless steel (salt spray test). those tests are using anodized aluminum.

[hahnmeister]

aluminum, even raw, doesnt react as much to salt and other corrosives. Raw Aluminum is used in many areas like this, the outer layers are oxidized (making it look not as shiny as new), but this layer protects the inner layers from exposure. It sort of coats itself. Engineers just take this into account and make sure they have something thick enough that if the outer layers oxidize, there is still enough material underneath for strength.

The big reason you see aluminum in boats and aircrafts though it not because of its corrosive resistance, but its strength. Think TITANIC. When Steel freezes, it gets brittle, not so with Aluminum.

[BeanAnimal]

Sorry... gotta call BS on this one. The steel of the Titanic WAS NOT brittle.... nor was it cold enough to become brittle.

Among other things... I am very interested in TITANIC and the science of why the ship is on the bottom.

here is a good link and a good site: http://www.titanic1.org/articles/brittle-steel.asp

I also suggest tracking down the latest Discovery HD documemtary regarding the reasons why the titanic sunk.

Ocean going ships ALL have steel shell plates and/or armor bands. Not aluminum. Aluminum is used for it's light weight... not because steel gets brittle. The same holds true for aircraft. It is a weight issue. Titanium is also used on aircraft.... Titanium is more brittle than steel...

Anway back to your regularly scheduled programming.

[BeanAnimal]

<a href=showthread.php?s=&postid=8488779#post8488779 target=_blank>Originally posted</a> by douggiestyle
aluminum is used heavy in the off shore boating industry. it is more resistant to corrosion than stainless steel (salt spray test). those tests are using anodized aluminum.

Yes anodizes aluminum has a high resistance to corrosion... it add cost and creates a brittle zone on the aluminum faces that can crack off under stress.

[hahnmeister]

Hmmm... every documentary, and even some materials professors I had used to say that the reason why the Titanic's hull didnt hold up as well as it should of was because the steel was too brittle in colder temps.

Perhaps those profs were full of it though. The curve for Steel puts its transition to brittle at about that of liquid nitrogen... and I doubt that the water was that cold.

[BeanAnimal]

There is a LOT of nonsense that is spewed daily about the TITANIC :) No the water was not THAT cold. Actually the water was nearly as cold as it could have been.

Sadly a large portion of or "profs" have no idea what they are talking about.

I am a surfer and a skater. I used to skate vert... I had a high school physics teacher that said there is NO WAY that you you can generate enough momentum to "catch air" on a half pipe. He want as far as saying that any photos of such phenomenon were fakes. That is one of a hundred stories... I used to get a kick out of showing college science profs why they were wrong :)

However if you want to lean on the other side of the fence... there are plenty of people that will line up and tell you that cold water and brittle steel is to blame for hundreds of liberty ship mishaps.... for example http://shippai.jst.go.jp/en/Detail?fn=0&id=CB1011020&

Here is a site that shows the actual test of the the steel. http://www.tms.org/pubs/journals/JOM/9801/Felkins-9801.html Not that it is not to todays standards... but was also not brittle enough to fail at the then water temperature.

So yes there is a LOT of science that shows that TITANICS steel was more brittle than todays... but again, the failure was that the plates were pulled from the hull when the rivets were torn free.

The Charpy tests (notch hardness tests) done on the steel opened up a whole can of worms that has been largely taken out of context when looked at in perpective of the entire TITANIC collision event. The ship did not "glance" off of an iceberg... it plowed into a HUGE one at a high rate of speed. Modern steel would not have saved her!

Have fun at that site.... it is fairly well put together with many GOOD articles and references to back them up.

Honestly hahn... your assumtions on TITANICS brittle steel were well founded in what you have seen and learned.... the aruements will never be solved. However Today's steel has a much lower ductile to brittle tranisition temperature... so the point is moot with regards to "modern steel" vs aluminum.

[douggiestyle]

most large off shore vessels are steel hulled, with most non ferrous underwater parts being a copper nickle alloy. aluminum usually is used above the water line in things like masts, booms, rigging and other fittings. and are not always anodized but still give good life.

bean i had a half pipe 8' radius with 1' of vert. want to build one for the kids/me. thinking about 36"- 42" radius and no vert. it will be funny to see my fat but in a pipe.

[douggiestyle]

your physics prof was thinking that gravity alone propelled the boarder up the opposite side. in which case he would have been correct. without doing it, its hard to imagine anything else.

[BeanAnimal]

Ohh I know what he was thinking... and there was no convincing him that you could generate enough momentum with your legs... EVEN AFTER sighting the swingset example. Just because you have a Doctorate does not make you "smart".

WAAAYYY OT:

I had a quarter in the driveway with an 8' transition... I regularly skated a steel clad monster that was 10.5' radius with 3' of vert and 32' wide. My own half was 9' radius with 1' vert and two 3' tombstones... steel coping of course :)

Too old, but still drop in now and then. Still skate my Dogtown Malbe with Rat Bones 97As and Bone Swiss Bearings... rip grip and all. When I slam I get hurt bad and it kinda takes the fun out of it. I never remember it hurting that bad.... and I used to slam bigtime on a regular basis. I was not smart enough to wear a helmet most of the time.... got kncoked out twice in 1 day trying to pull off backside boneless ones over a 4' channel.

I showed up at a local bowl over the summer and had all the kiddies stoked. I am not what I used to be, but can still tear up backside airs, inverts, lien to tails, texas plants, and of course big fat alley oops, cess slides and the rest.... "wow look at the old guy rip.... yeah!".... "man thats some old school stuff... yeah". "wow did you see the old timer slam, that had to hurt... dude look at him bleed". "dude how OLD are you?" When I tell em 36, they all can't believe that OLD guys can skate like that.

Bean

[BeanAnimal]

In any case... back OT. I would check with Randy Farley regarding the toxicity of aluminum oxidization and your tank inhabitants. I seem to remember reading that it is NOT good for them.

Bean

[douggiestyle]

bad for softies i believe.
i dont think they where planing on putting the al in the tank.

[hahnmeister]

Randy was critical of Aluminum based phosphate binders, like Seachem's phosguard. FWIW, I have been using it for 2 years now w/o problems, and Im growing mostly SPS.

I dont think there was anything bad about Aluminum equipment, other than the salt being bad for it. If I remember correctly, the dust from the phosguard was what aggrivated the SPS. With solid Aluminum, you get no dust. When it 'rusts', it doesnt dissolve into the water, but rather forms a brittle outer layer on the outermost layers of the Aluminum. Granted, there is SOME Aluminum that will always get into the water due to dispersion, but that is negligable.

[douggiestyle]

mine had a roll in, in the center. pvc coping. also had a sweet pool. 12 foot deep. required us to break in to the local cc. but they didnt care.

keep in mind this was 1981 in pittsburgh. everything we did was pretty much cutting edge in our eyes.

had a 10" krypstick with independent trucks. kept breaking the king pins had to cary some in my pockets. sad thing was one year later i was driving and the board went in the trunk. sure i still would skate but not often enough. so i just missed the big craze.
ide say two or three years younger and i would have learned to do all the big air moves. stacy perralta was my hero. think lords of dogtown.
miss all my old fiberglass boards from the 70s. bigfoot. everything i had was ordered form the back of magazines.

[BruiseAndy]

<a href=showthread.php?s=&postid=8490455#post8490455 target=_blank>Originally posted</a> by BeanAnimal

WAAAYYY OT:



Too old, but still drop in now and then. Still skate my Dogtown Malbe with Rat Bones 97As and Bone Swiss Bearings... rip grip and all.

Bean

Making me sad that I ebayed my winterstick longboard that had my first set of rat bones on it. Damyou.

[polaraligned]

Pound for pound, aluminum is 5% stronger than steel.
I would use steel for the stand and aluminum up top.
Give the steel a good enamel paint job and you will not have
any problems. If you could, have the aluminum top frame
anodized. After all, many light fixtures are made out of an
aluminum frame. I have not heard storys about fixtures
falling into the tanks.
As soon as a new surface of aluminum is exposed, it immedietly
starts to oxidize. This aluminum oxide surface protects the
aluminum from further corrosion and enhances it's durability.


Scott

[BeanAnimal]

I still have plenty of Rat Bones... My ramp was in Indiana PA.

Circa 1980-90 Ramps around here...

The steel monster was owned by P.J. Kelly in Altoona 1988 or so (very dangerous ramp due to corners of steel sheets sticking up like razor blades... that ramp doled out plenty of stitches!!. The other steel monster was At PA cheapskates (North Versailes, PA, still there but chopped down to a ditch ramp) and nearby was the Haymaker Ramp which is long gone I guess... The Reagan Ramp (owned by friend John Ritter in Delmont, PA which is also long gone but not before Hosoi, et al visited). The Juvie ramp in Johnstown PA (which rocked, but was splinter city, I had several the size of pencils and toungue depressors), My ramp (Dead Fly ramp in Indiana PA).... and another dozen close by ramps :) Including the skate park at altoona (also splinter city but had a decent shallow pool). I am one of the sick freaks with a 2' mohawk that was launching method airs over the car (padless) at the mon warf in the street contest back in 88' or whenever it was. Bunch of bands played if I remember correctly... Half Life just did a reunion show a year or so ago at the old "upstage" lounge... what a trip seeing them after all these years. Yes my old butt still goes to shows.

Ziggler and the gang still skate here... Zig has a ramp at the slovac club... all the old timers still skate there I guess. I am to embarassed to actually show up. Those guys are throwin 540s and other sick stuff. They bust backside airs that make mine look like 70's air.


Anyway back on topic. I have looked into some DIY anodizing kits. It is something I would like to try. I still think I read someplace that aluminum oxide was not good for the tank (other than the article by randy about the alumina based binders).

Don't get me wrong... My DIY light bar is made out of aluminum. I don't really see a problem with using it as long as it is not submerged or water allowed to accumulate on it and drip into the tank.

The ideal way to treat a stand would be powder coating. The price depends on where you live I guess. That is also something I would like to try at home, but I don't have an oven big enough to cure anything more than small parts. I will add that to the list of want to dos that I will never get around to... like aluminum casting.

In any case an aluminum stand would be fine. The problem will be finding a way to attach the pieces in a simple and strong manner. If you plan on "skinning" the tank, then you can use a bolt up method. The only reason I could see doing this would be to save a few pounds worth of weight.... otherwise I would use steel and weld it up. As Scott and other mentioned, Aluminum is fine for the hood. If you want to be fancy then get it anodized :)

Bean

[douggiestyle]

wierd how things go around. never liked half life much but did get my first mohawk at mikes lavellas place '84 ? maybe i was 15. at the electric banana on sundays, sometimes the new group theater in the strip. the underground railroad was a favorite. nothing like partying with dri, the dead kennedys and coc. those were messed up times. im lucky to be alive.

its funny went off to school moved got a job etc. and came back 5-6 years later. im talking to some college teens about boarding and they go off talking about the "shiner" ramp how its over 10' high and all, im like cool lets go and they take me to my ramp. im like, this my ramp, i dont ever remember naming it. surprised it was still around. then they start telling me about a pool they drained and started skating in...

yeah 70's air ha ha, like man i got three wheels out of the pipe. geting three out of the pool was a big deal. about 5' of vert. catch a truck and it was a long way down. broke my arm in it. nothing like diving head first into an empty 12' deep pool, with no pads or helmet.


oh yeah
i think you put together a ccouple heat lamps or an old bake element in an insulated box to get the job done.
whats the temp needed for powder coating?

[surprise]

Wow great response. I appreciate all of the responses. I think I will do some local research and see the cost of anodizing the aluminum parts. I am also thinking about looking into some plastic material, like Acetal.

[Conano]

titanic sunk cause it hit a freekin iceberg. simple as that.