crack in cast aluminum

arbarnhart · #1 (**permalink**) 09-11-2007

I had a ramp accident; my rudder dropped and I damaged it only slightly, but I cracked the cast alumiunum rudder housing. Here is a picture of one (not mine, but a handy photo):

The crack is close to the lower pintle. The housing is one piece of cast aluminum, so it is still attached at the top, quite heavily. I did not notice the crack until after I got home and I had sailed with it like that all day. Between still being solid at the top and the cleavis pin through the rudder holding it tight, there had been no problem. My thought is to work some thick epoxy into the crack. I could also drill through and bolt it if that were necessary. I will be securing my rudder in the up position using a better method (I was using a friction cleat) in the future. Anyway, what would you do?

Boasun · #2 (**permalink**) 09-11-2007

You could always have it reworked at a metal shop. Or build one yourself from cabinet grade wood.

Check the crack. It may have been there for awhile and dropping it just added insult to injury in making it worst.
But at least you was ashore when it happened and can now fix it without being in a fix yourself.
If it had broke offshore you would have gained rapid training in how to jerry rig a temporary rudder.

jrd22 · #3 (**permalink**) 09-11-2007

You should be able to take it off and have it welded at a shop(find one that specializes in aluminum welding, preferably marine aluminum welding). Shouldn't be a big deal if it is in a spot that they can get to both sides of. Good luck.

arbarnhart · #4 (**permalink**) 09-11-2007

Boasun,

You may have missed one piece of info in my post - I sailed around all day without noticing it and happened on it later when I was taking the rudder apart for storage. It seems structurally sound with the crack, but I want to secure it. On further inspection, there is enough space to drill a small hol near the crack and pass a bolt through, so I am going with poly glue in the crack and a bolt next to it.

Idiens · #5 (**permalink**) 09-13-2007

There are glues specifically designed for repairing aluminium castings.

LakeEscape · #6 (**permalink**) 09-13-2007

Hard to see that as a single casting. A casting would be so much weaker than a built up part. The housings I have seen are generally made of 4 metal components, welded together, and a few pieces of wood and the rudder.

I just repaired a rudder housing on my SJ23. Like several I have seen, the original welds were so bad, I chose to have it completely dismanted and rewelds. The crack at the pintle block showed that the original weld had not even penetrated the sides. Cost all of $85 to have this done and I have no concerns now.

Those housings take alot of stress and this is a really good place to have some extra beef built in. It's a safety issue.

Fair winds,

LakeEscape
Lake Norman, NC

arbarnhart · #7 (**permalink**) 09-13-2007

Quote:

Originally Posted by Idiens

There are glues specifically designed for repairing aluminium castings.

I searched around quite a bit and came up empty, other than finding some vague references to some indistrial compound unavailable to consumers due to safety issues (supposedly had an MSDS sheet that listed a dozen or so horrible ways to die). Could you give me specifics? If there is one I could get, I would really like to know for future reference. The way this particular repair worked out, the adhesive really doesn't have much function; the bolt is securing it and it seems rock solid.

sandspur · #8 (**permalink**) 09-13-2007

Drill a small hole at each end of the crack to keep it from getting larger , Even if you have it welded they will do this to keep it from running

Idiens · #9 (**permalink**) 09-14-2007

arbarnhart - Another reason for me to get back to the boat tomorrow. I have a tube of it on board, but Altzheimer has been working on the brand name for me.
I thought I had got it from www.conrad.de but the only one in the catalogue now is number 813325-99 which is an epoxy based product. The one on the boat has to have it melted in place to bond.

Goodnewsboy · #10 (**permalink**) 09-14-2007

A crack is a serious structural defect in a metal part. Glue, even my favorite J-B Weld, will fill it in aesthetically, but it won't restore any substantial strength. If it is a fatigue crack, it will break away from the glue and continue to grow.

If you want to be sure of it, have it welded by someone who works with aluminum. The finished weld can be ground back to original contours and the part should be at or near original strength.