house boat

[daedong]

I intend to build pontoons for a houseboat,the design i have chosen are hexagenal 3mm steel, baffled every 1200mm and fabricated in 1200mm sections. To achieve the hex shape i will have steel sheets 1200mm x 1800mm folded with two folds per sheet @ 60 degrees then will weld two sheets together to make the hex making 600mm sided hex, i will then weld these sections together to make 12mt pontoons.My question is this when welding these sections togther what is the best sequence to weld them together. I assume i tack each corner first, then do i weld one side then the opposite side and so on.

[egon]

The fellows I've watched welding pipe would tack the two pieces in several places and then run a continuous bead. Chances are after the first section you will find what works best for you.

Sounds like an intriquing project.

Egon

[GaryM]

I recently visited a company that manufactures, among other things, monopoles for cellphone antennas. Now some of these are 5-6 feet across the base. These are received in two half sections that are prebent to form half the finished shape. I don't remember the number of side, but it was more than six.

But anyway I noticed that that they had welded eyes on the inside of the sections and had a turnbuckle installed on the diagonal across the joint. They used the turnbuckle to bring the joint into alignment prior to welding the seam. After the seams been welded, the turnbuckle is removed.

You might want to consider a similar arrangement.

[gsganzer]

When you make a long weld on a large piece like that, you need to watch out for deformation. Usually you tack it in multiple places and then use a "back step" approach. If you just start the bead at one end and try to run it continuously the length of the piece, the metal will deform. When you back step, you start your bead approximately 6" ahead and work backwards to the previous bead.

I'd probably alternate between welding the two sides, that way you keep the heating to a minimum and the distortion more uniform.

[daedong]

Hi
Sorry about the metric measures in the first posting [img]/forums/images/icons/confused.gif[/img]

Thanks for all the ideas, i'm taking them all in, so keep them coming for me to chew on.
I went to the city yesterday, Adelaide, about 170 km (100mls)away and ordered all the steel and organised the cutting of the baffles and the folding of the plate. forty sheets 6'x4'x1/8' (1200x1800x3) and 10 sheets 8'x4'x1/8 (120x2400x3) It should be here late next week.
I have also bought a new mig welder 220 amp and my old mig I am having it set up for welding aluminium and also treated myself with a new automatic shield [img]/forums/images/icons/grin.gif[/img]

[gsganzer]

You'll love the automatic shield. I bought one a few years back and love it. They don't work too well outdoors though. The sun makes them trigger. I have a cheap one, the better ones may have a sensitivity adjustment that eliminates the nuisance.

Make sure you post lots of pictures. It sounds like a big undertaking. It'd be interesting to watch the progress.

[GaryM]

I have a automatic helmet I bought at Harbor Freight. It works fine outdoors in the sun.

A friend just bought a cheaper one from CeeKay Supply, don't remember the brand, and it triggers if the direct sun hits the sensor. It hasn't triggered from reflected sunlight, yet.

[daedong]

I will bore you all to tears with lots of photos from start to finish of the houseboat. The steel for the pontoons has not turned up yet, i rang the supplier yesterday they said it will be here next week. By the way this project is a 2.5 year one.

[daedong]

The steel arrived today and i started straight away here is the first photos
http://f1.pg.photos.yahoo.com/ph/vin...ns&.view=t

[GaryM]

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