Overplating - hows it done?

[stuart]

I'm sure Yanmax did an overplating job himself - but how do you go about such a thing?

 

You've probably read the African Queen build blog. If I can get the labour + some one who can weld it all together, whats the best plan of attack?

 

I've been told so far, to cut away some of the existing floor, drop the boat onto a fresh base plate + weld that to the holes cut in the old baseplate, then go around the sides adding steel and welding to existing side and base plate.

 

Hows that sound?

Edited August 21, 2007 by stuart

[Liam]

Sounds pretty much ok to me. A friend is trying to arrange the rebottoming of his aging Harborough boat, and the welder has pretty much said the same thing.

 

I'm guessing that the base plate will need to be laid and welded into place, so that the boat can then be placed onto it. I'd think it would be wise for holes to be made in the existing hull to enable the welder to secure the new baseplate to the old to stop it from sagging etc. I'd obviously leave some of the plate overhanging, say half an inch on either side. The side plates can then be measured, folded or whatever, and then welded.

[Big Steve]

Interesting, I may have to do this soon, boat is 32years old, but it's got concrete ballast, would I have to dig that out, or can you get away with welding around the edges?

[Yamanx]

I put the boat onto tressles, about 1m high, I used four tressles but the shape of the boat meant it only sat on three of them. This was so we could get under the boat to weld the sheets together.

 

It was too rusty to try and weld successfully to the existing base plate, it would just pull away. So we slid the sheets under the boat between the tressles, blimin heavy and there was many hands. We used a jack to lift the boat off each tressle, only about 10mm high, just enough to slide in the sheet.

 

Each sheet was tacked in place, and a gap of 2-3mm was left between each sheet, before we slid them in they were prepped on the edges. This meant the first run of weld stuck the edges of the sheet to the original bottom, although it was that bad, it would not stand up structurely. Each sheet had four runs of weld, on the join. Mega strong.

 

At the edges, it was too bad to rely on just welding to the original edge. I ground off the original rubbing edge so it was flush with the sides, then welded to what was left. I left the steel sheets their stock size at this point and the boat looked like we had welded a great sledge to it. The edges were sticking out about six inches each side. I then cut some smaller sheets (I cut them at work on our guillotine) 500mm wide which were welded to the new bottom and up the sides, the sides were far more sound. So really we had created a sort of new steel shoe, which has its own strength.

 

Right at the end I went round with a cutting torch to trim off the edges, leaving plenty of edge still sticking out for wear.

 

The whole job took six or seven full days work, although this was actually spread over a few weekends.

 

I can recommend the boat yard I used to put the boat, I did all the work (with some help from some freinds), the boat yard supplied the space and the electricity. They charged me £25 per week for the space and about £30 for electricity. I shared the cost of the crane with them as we timed it with any lifting they needed to do. Oxley Marina on the S&W at Wolverhampton.

 

I cant offer to do it for you, as I just dont have the time, but if you need a helping hand and you're fairly local I dont mind mucking in.

[stuart]

The boats actually at Caggy's boat yard on the BCN. No problem with storage at the moment. He's a really good bloke there, not charging whilst were not fixing the boat - he knows the new owner got a bit stiched up with this one!There's currently no rubbing edge on this boat at all, so looking to add one - just need to keep a check on the boat width!Luckly, theres plenty of fork trucks and JCB's around the yard to move sheets of steel about. I think we'd probably drop the boat ontop of the steel rather than use tressels.Did you cut any holes in the sides for welding through or just on the base? Theres only 2-3mm of steel left on the base so probably a lot of this will need cutting out.

I cant offer to do it for you, as I just dont have the time, but if you need a helping hand and you're fairly local I dont mind mucking in.

Thanks for the offer Yamanx. If your free in a couple of weekends time for some consultancy that would be very useful! I wouldnt expect you to get your hands dirty though!!

[Yamanx]

The boats actually at Caggy's boat yard on the BCN. No problem with storage at the moment. He's a really good bloke there, not charging whilst were not fixing the boat - he knows the new owner got a bit stiched up with this one!There's currently no rubbing edge on this boat at all, so looking to add one - just need to keep a check on the boat width!Luckly, theres plenty of fork trucks and JCB's around the yard to move sheets of steel about. I think we'd probably drop the boat ontop of the steel rather than use tressels.Did you cut any holes in the sides for welding through or just on the base? Theres only 2-3mm of steel left on the base so probably a lot of this will need cutting out.Thanks for the offer Yamanx. If your free in a couple of weekends time for some consultancy that would be very useful! I wouldnt expect you to get your hands dirty though!!

 

Probably shouldnt need to cut anything out, especially if the boat is fitted out, if the boat is gutted then its easier of course.

 

Sure, I'd like to pop down, just say when you're going to be down there. (Cant make 8/9th Sept.)

[stuart]

I'm off on my travels next week so will PM you nearer the time. Once again ta!

 

Stu.

[smileypete]

Hi Yamanx,

 

A few questions if you don't mind...

 

Did you use stick or mig? And how thick was the new plate? Did the trestles belong to the yard or did you supply them? I expect they had to be pretty strong to support a NB 1m off the ground!

 

Also how was the steel bent around the bow area? I would probably try welding some kind of support to the steel and then using a large bottle jack.

 

cheers,

Pete.

[Yamanx]

Hi Yamanx,

 

A few questions if you don't mind...

 

Did you use stick or mig? And how thick was the new plate? Did the trestles belong to the yard or did you supply them? I expect they had to be pretty strong to support a NB 1m off the ground!

 

Also how was the steel bent around the bow area? I would probably try welding some kind of support to the steel and then using a large bottle jack.

 

cheers,

Pete.

 

I used 6mm plate, I couldnt handle anything thicker.

 

Mig, its complete rollox to suggest you have to use stick. mig (Or mag) is used for welding all kinds of things far more important and liquid tight than a narrow boat. In fact the most likely problem with pin holes is where you start and stop welding with stick thats every 6 inches or so and you need to knock off the slag each time, with mag you can go on for ever and no slag, infinately quicker.

 

Its easier than you think to shape the bow, just push it in a bit at a time tacking it as you go.

 

I made the tressles myself from 5 x 2 1/2 channel, yes they were very strong indeed, the boat weighed 14 tonne. I left them at the boat yard.