Aluminium Boats -Info Needed

[afro]

I am currently completing my final year thesis in my civil engineering degree. I have chosen to do some investigation into aluminium boats and require information from those people who have had trouble with their aluminium boats. Any stories about cracks or other problems would be appreciated. If you have had any repairs done could you give a basic description of the repairs and there sucess. Thanks Justin.

[mackmauler]

Justin, Im pretty good at cracking aluminium boats ??? Its not just 1 either ::)

Basic description of repairs, cracked welds - welded again and cracked again, same reason first cracked I guess, doesn't address the reason for the cracks.

Rob

[BS]

Justin, I think Rob understated his feats of destruction a little - his record is almost unbeatable.

To add to Rob's post.....

After seeing all the failures which he and I (younger brother) have been associated with, I think that the main cause of failure of welds and splitting of aluminium in small boats (say under 6m) is that the structural bracing simply is not up to the task. I would assume that with cad design, computer cutting of sheets and further advancement of welder's, that the problem doesn't lye in the machinery or the processes used.

The amount of flex that some ally boats have due to a lack of bracing ribs on the hull is shocking and it would seem that the level of build quality varies greatly from one builder to another (from excellent to well below average). It's one thing to know how to weld aluminium and another to design, and then build a boat to last!!!!

The repair jobs that I have seen done vary from solving the problem completely to being a bandaid from willing repairer's that fail repeatedly.

Most problem's do reoccur and this can only be put down to one thing - original design failure, oh and bit of torture by the owner. ;D ;D

Brian.

[davo]

I think another major cause is some bloke off the street could be learning to weld on your new pride and joy. All I know is that once the fatigue cracks start you chase them around the boat.

[dazza]

Hi Justin,
I had trouble with cracks in my tinney. I solved the problem by welding a 4mm plate bottom in it.
I believe the cracks were caused by 2 things.
Firstly.
I used to live up on Cape Youk and we would go on extended trips in the boat. We would probably have up to 300kg of gear up the front. The continual pounding i believe stressed the alloy and caused the cracks. You could see the alloy depressing (stretching) between the ribbing. I also used to store my fuel under the front deck as well which added to the problem.
When I took it to the guy to get it welded up he said he sees this all the time and he believes it is from carrying too much weight. You have to remember that up in those parts the god old tinney is one of the main forms of transport.
Secondly is trailer set up
My trailer had those polly skids on it. After awhile they bowed and there was 2 pressure points instead of even weight distribution. I believe this had alot to do with the cracks down toward the transom. One was a star shaped crack and the other 2 were lenghtways.
I fixed the problem by welding in a 4mm plate bottom and bracing the poly skids with a piece of heavy angle and adding another cross member and roller to the back of the trailer.
Hope that helps. I have some photos with the bottom cut off of my tinney which gives a good view of the ribbing. Havent got them developed yet.
Cheers
dazza

[Kerry]

With some things it can cost the same to build it right the first time as to build it wrong and keep repairing it.

One problem is that many things are built "down" to a cost, relative to a production quota and not "up" to a standard.

Experienced alloy welders (people who really know what they are doing) are rather difficult to find these days and any welder who simply welds a crack then it's time to find another welder.

Alloy is a funny stuff but most of its problems are people related (in many different ways).

Cheers, Kerry.

[clutter]

Trailers are a biggie when it comes to cracking, not just roller and skid set-up but also suspension.

Another cause of cracks when trailering is overloading out of the water. While a boat might be designed for 400kg in the water, it most certainly is not meant to carry this sort of weight in it on a trailer scooting down the highway full of bikes and crap for a holiday. (from experience)

Most boats seem to be designed reasonably well, however as a boaty becomes more familiar and confident with himself and his craft he will no doubt push it past what it was originally designed to handle. Even the top of the range "built to a standard" boats will crack-up when used outside what they were designed for.

Cheers, Clutter.