I'm running into technicalities regarding welding alumi

File: metal.04.jpg (94KB, 1196x616px) Image search: [Google]

94KB, 1196x616px

Or is it a good thing it loses half its strength?

This is an aluminum sailboat after collision.

Does the annealing make it more malleable and less likely to crack and fail?

Why not do it the old fashioned way and rivet it?

Why does a boat even need hardened?

>>1175645
>I plan to build a live aboard sailboat and I'm considering aluminum.

why?

if the answer to this is that you just have to much money and dime that this seems like a good idea then OK. But really you will be able to buy a boat for a 10th of the cost it will take to do this and all the kinks will have been worked out along time ago, well before you show up.

assuming because you are asking 4chan you are a first time boat builder, building a small plywood glassover skiff is probably more your speed.
Also if you plan on salt water that aluminum will corrode like fuck if it as much as looks at iron/steel tools,

>>1175651
OP will probably think he can rivet and fuck it all up.

Plus then it wouldn't even be water-tight.

>>1175645

Aluminum??? I wish I had your budget. Planning some high lattitude sailing? Definitely be a tough hull if designed right.

I can't speak from experience but quenching should work. Strange, but when I see pics of aluminum boats being welded I don't see any suplemental cooling going on. btw, I thought keels are bolted on now a days.

If you don't get a satisfactory answer here you could always try the 'Construction Maintenance, Refit' forum on CF.

>>1175645
>Anyone have any ideas about how to fix this?
Engineer for heat-affected zones or budget for heat treating the hull after it's welded.

>Would that work?
No. For welding to happen, the metal has to melt, and spraying hydrogen-containing water around liquid metal is a good way to cause cracks and porosity. But generally, cooling metals while welding (there are various ways that actually work) can reduce but not eliminate the heat effected zone. There's no getting rid of the loss of strength because the annealing temperature is lower than the welding temperature, but that does reduce distortion.

Anyway, aluminum corrodes in salt water, and there are other choices for structural material. Why are you considering aluminum? Steel is cheaper, stronger, far tougher, and welds much better. Fiberglass resists corrosion, and is easier to form into sleek shapes. Aluminum has its advantages, but what are you looking for here?

>>1175650
>Or is it a good thing it loses half its strength?
Annealed aluminum has lower strength but typically higher toughness, Which is more important depends on the design.

>>1175651
>Why does a boat even need hardened?
Structural aluminum is almost always purchased and used in a (at least somewhat) hardened state because it's a lot stronger than the soft state. Aluminum is expensive, so even in situations where weight itself isn't a major concern, stronger aluminum reduces the amount and therefore cost of the material required.

righto lads, im an apprentice at a alloy fabrication workshop we build two things (mostly) boats and bridges
alloy boats are for the most part worse than fiberglass boats for a lot of reasons but the big thing about them is they are tough as fuck, but for that you need to chose the right tempers of alloy so it dosen't get too fucked welding it
if you go the alloy rout i hope to god you're not gonna sleep in it bc it is fucking loud in there
if this treads still up in the morning ill post a few pics of the boat were working on at the moment

>>1175645
>Anyone have any ideas about how to fix this?
harden it.

>Would that work?
Can't see why not. The temperature is about right.

>>1175734
>loud

Install some sound dampening.

File: Screenshot_2017-05-11-23-30-03.png (631KB, 1440x2560px) Image search: [Google]

631KB, 1440x2560px

>>1175645

The post above yours has the right idea.

>>1175657

I want a /diy/ project that will educate me about a massive number of things like welding, fabrication, math, electrical systems, etc.

Plus a boat is the ultimate mobile home.

And aluminum boats HOLD their value harder than death holds his scythe so its a damn fine investment of a project.

>>1175720

I'm dirt poot but building a sailboat all by yourself is a years long process. Because aluminum won't rust I figured it'll be fine to add a little to it whenever.

Ballasting the keel can be done with many ways.

Honestly if I was rich as fuck I'd use osmium instead of lead.

Now THAT would be a boat that'd hold value.

>>1175730

How much does aluminum distort when welding? Can you even heat treat it?

I want aluminum because it resists corrosion better than steel. An all aluminum ship in salt water will never corrode. Using dissimilar metals will cause electrolysis though and that corrodes fast as fuck.

>>1176075

Holy shit, what?

>>1175651
> What is parasitic drag

>>1176107
>1175720 here, I hear ya about the construction timetable. A very neat project to undertake. The day you put her in the water you'll be thinking 'holy sh*t, I finally did it.' :-)

My dad restored a 27 ft sloop with a grf hull in the mid-1970s. Many weekends for 3 years before he splashed her in the water. I still remember watching the travel-lift lowering her into the water that day. Dad with a shit-eating grin after stepping the mast. I like to think it was a bit more satisfying than buying one all ready to go.

>>1176135
>accidental greentext
woops... fucked up there .

>>1176135

Nice!

Also, no I'm not "planning" sailing in arctic conditions but god damnit what's the point of having a sailboat if you can't go on a penguin safari?

I hear GRP and carbon boats get brittle in cold seas.

>>1176107
>How much does aluminum distort when welding?
That depends greatly on fitup, technique, and settings. Much more for continuous oxyfuel welds than spray MIG stitches, for example. Generally a few times as much as mild steel steel of the same thickness. For a complex project like this, it's generally best to tack all the structure solidly together before doing any proper welding so that it can hold itself in place against distortion.

>Can you even heat treat it?
Most structural grades of aluminum achieve their strength with precipitation hardening, which is a particular kind of heat treatment. This is not something you will DIY. It would be possible in principle to heat treat a welded boat to restore the HAZ to full hardness, but it would be a gigantic hassle. Heat treating complex weldments is generally not a thing that is done, and instead they are designed to accommodate the weaker areas adjacent to the welds.

>An all aluminum ship in salt water will never corrode
Depends on the alloy involved. High strength alloys often sacrifice a degree of corrosion resistance. And different alloys have different redox potentials, though that's probably not enough to matter for galvanic corrosion. If you're using it in salt water, use zinc sacrificial anodes.

>>1175645
You can pre-heat it, so the heat wont transport away to easily. This will prevent cracking from the weld cooling down quickly and will remove any hydrogen. Pre-heating wont prevent strength loss.

It is possible to temper the material after welding to regain strength however, this would be a massive pain in the ass to do even on a small boat. Unless you have the budget to putt the entire hull in a oven and then have it quenched.

the trick is to select a base-metal and filler-metal combination that even after welding still meet the mechanical properties required.

5083, 5086, and 5454 are commonly used base materials in ship-building.

You can download datasheets from filler-metal manufactures, that will show what mechanical properties different combinations have. Or just call them up and ask for advice. Companies like licoln or bohler have run many test with different materials and fillers.

inb4 Tin Can 2.0

>>1175645
I work at sea in mostly smallish aluminium boats. The guy I'm working with has a small 7-8m aluminium boat he made "himself", meaning that he got all the parts and had a guy welding it. All other installations he did himself, I believe. The boat had eventually a price tag of something close to 200k€. Yes, to hire a guy costs a lot but there was a serious amount of parts and labour needed.
It truly is the best work boat I have had the pleasure to work in so the end result is really good as you get to plan everything yourself and have it just like you want it.
But. I know you are on the "I just want to love in a boat"-phase but there are bigger concerns than aluminum structural strength! If it truly is going to be a liveaboard the first thing is to find a nice design, then you need to check out a ton of other boats and talk around so that you know what works and what doesn't. Preferably live in a boat for a while (I for certainly did, I was dreaming of boat living also in a stage). Then the material comes eventually. Aluminium have been used for boat building for ages. It's really no biggie.

So I think this dream of yours goes in the same category as the underwater dwellers' of shipping container bunkers or mad max car guy's or other ridiculous big projects. I think it is not going to happen as you ask the wrong questions.
There are forums, Web pages, even organisations that are solely for people living in boats. And the same goes for boat builders. Even boat builders in different materials! You need to research first where you want to be going...

And one design that seems common enough is the Bruce Roberts 53 (56? 57?). I have seen several of these and been in a few. There are at least fiberglass and steel versions, so why not aluminum? But I'd go for steel or fiberglass also as it truly is cheaper and easier to work with...

Do some proper research first!

>>1176153
>If you're using it in salt water, use zinc sacrificial anodes.
This is true even in brackets water! As with other multi-tasking structures there will be other metals with different electronegativities so there will be corrosion anyway. Zinc is cool for all metal boats.