Aluminium Spar Repair Welding?

ccscott49

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Dont know, but the only repairs I see are rivetted ones, unless it's a crack, maybe weld it.
A cautionary tale. I watched a man trying to weld up a crack in the transom of a racing boat, aluminium, started welding at one corner, chased the crack right across the transom, never was right. The ally was work hardened, then the heat just drove it nuts!
 

Bejasus

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hmmmm, my spars and masts are heavy aluminium, not the lightweight modern stuff. The connection to the gooseneck is via a pin going through two webs welded to the front of the spar and passing through the goosneck. Whilst changing out the bolt that was through there, which was worn, I inadvertently caught the web on the opposite side from where I was tapping the new pin through, and cracked the weld. I am hoping to have these webs removed and rewelded at some point during layup in a month or so. As I said these are heavy spars and not the usual thin walled type.
 

Bejasus

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on this occasion, yer not wrong...... /forums/images/graemlins/blush.gif /forums/images/graemlins/frown.gif
Lashed up the spar and just thought I would drift out the old with the..............bugger!! /forums/images/graemlins/mad.gif
 

DaveS

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That's interesting. I wonder if there's any connection with an odd experience I had some years ago?

The Etap 22 has an aluminium rudder blade made of plate about 10mm thick. After coming through a heavy squall (F7 gusting 8) I discovered that the rudder was bent through about 30 degrees. On removing the GRP fairings a crack was seen where the bend had occurred, extending for about 3/4 of the width of the blade. It looked old (no idea of the cause) but certainly explained why the rudder had bent where it did.

One small problem was our location when the problem was found: Loch Scresort, Rum, which is not over endowed with repair facilities. However, SNH were most helpful and gave us the use of a workshop that had a big vice and a blowlamp. After a lot of heating we successfully bent the rudder back straight, then through bolted 2 pairs of field gate hinges to it which ensured that everything stayed together. This temporary repair did for the rest of the season. It didn't look too pretty, however, so once the boat was laid up I took the rudder blade off for welding.

I went to a very reputable outfit who duly welded it. In the car taking it home I heard a sort of "boing" noise and saw that the weld had parted: the crack was back. Back at the welders there was much embarrassment and the job was re-done, and this time seemed to be fine. I sold the boat a year later, but presume it's still OK. I have never really understood why the first weld failed, however.
 

GMac

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Of course you can weld up alloy spars. Most are fully welded these days.

Repairs by weld is also not un-common but wether it's the best to use depends on the fix-up being done. Sometimes a few rivets can do the job. You don't say what your particualr problem is so it's hard to say.

Have a chat to your local sparmaker and they should be able to tell you.
 

William_H

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Yes spars are welded. My tapered mast has had the front tof the stock aluminium extrusion cut out and the front welded to make a taper from the hounds to the top. In addition the bottom is welded to form a specialised pivot for the mast base. This is a common procedure by mast specialists.

The welding however will change the heat treatment so that is is not necessarily so stiff when welded. TIG welding is prefered as it heats up a smaller area of aluminium. (I think)

The actual location of weld repair is important. ie you can weld without concern at the base or at the top. The biggest stress in a mast is in between the points that are supported by stay wires.
So a repair at the point where the spreaders are attached and the lower stays meet is not so much of a problem. But in between is where it is likely to bend and crumple in compression. In the case of fractional rig mast the real load comes from the forestay and sidestays pulling down.

However for many repairs a sleeve rivetted in is better and there is no concern about the heat treatment. (or temper). And in my case it is DIYY.

As for the weld repair on the Etap rudder. The best repair would have been to recut the rudder blade so that ony good uncracked metal was at the point of major bend.(ie shorten the balde) Usually at the bottom of the supporting cheeks. The broken off piece could have been welded back onto the bottom of the rudder where there is less bending moment and you still have some rudder if it falls off.
Clearly if the original plate cracked then chances are the welded joint will be even more prone to failure. I was assuming here that the rudder was a deep blade only supported near the top.

With mast repairs, sailing is no fun if you are concerned about mast integrity so that may dictate a new mast even if the old one is probably OK.
anyway good luck olewill
 

ccscott49

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Might be a good idea to mention, "of course you can weld up, NEW aluminium masts".
Old ones with work hardened stresses, which are not uniform, are not as easy to repair. Think about the old comet aircraft!
Maybe with the rudder blade it might have been better to anneal it first, achieved by heating, until a match stick leaves a brown streak when rubbed on the aluminium, then allowing to cool.
 

savageseadog

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Its a crack in a boom near the kicker fixing, I'm trying to replace my own (undamaged) boom with a slightly longer one.
I'm well aware of mast tapering by welding, I have a taper myself. The taper isn't subject to a point load though. I'm aware of stress hardening of metals but do't have any idea of whether this occurs in yacht spars to the extent it would jeopardise a welded repair. Masts are repaired by sleeving simply because a but join would be too highly stressed, they are always pop riveted at least all the sleeves I've seen are. Would sleeved and welded repair work ? I've no idea. I have seen welded tangs on yacht masts and always wondered if they are OK.
What I'm trying to work out for myself is if a 1.5 inch crack in a boom could be just tigged up. I'm talking about a 12ft yacht boom here.
 

ccscott49

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As I said, give it a go, but if it starts to propogate, watch out! Might be and idea to see where the crack ends and drill a hole at that point, to stop the crack propogating, it may help, does in some other metals and wood!
 
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