strengthen the welds on the frame

I have no knowledge of how strong it might be but if your after good quality high stress welds why not make the yacht with 'tack' welds from you and once you get the shape your after take it to a professional welder to finish it off and fully weld the frame.

You might be suprised at how strong your welds will turn out.
try not to steel that is too thin. Im only an amateur but when I have a weld fail I have a good look at why.
its usually because the tubing was a bit thin to start with. when i susequently rebuild , i dont put too big a brace over the area , just enough to add to the strength , but not too heavy.
keep in mind that the type of chassis your building has to flex and twist as it travels over rough ground with no suspension other than the flex of the tubes, so too stiff will slow you down

Luca,
Which ever method you use unless you regulate your machine correctly you will blow holes in your work. I am not as good a welder as most of the other lads. Self taught. I found that talking to those that are good welders and practice have improved my work very much. Get into your Work Shop and use up any tubing and sheet you can lay your hands too and practice. Blow Holes ? Cut the power down a little until you can get the weld to run. Tack Weld ? Short bursts of weld, work your way around the job until you fill in the gaps between the welds. There are a myriad things to take into account. "Never Say Die" Keep at it and you may well surprise yourself as to just what you can achieve.

There has never been a man born with a welder in his hand. If there is a feel for his poor mother. If you can contact someone nearby to instruct you a little then so much the better.
Regards,
Ron

"Good, better, best. Never let it rest until your good is better and your better is BEST"[}:)]

You could use "Google translator" to read this.

www.mig-welding.co.uk/gasless-mig.htm

It is really important that all the flux coating is removed before you do another pass/weld over the top with gasless welding.
The multipass flux cored wires, that are designed to do this, without the flux first being removed, are much more expensive to buy.

If the weld is really aerated, you will have to grind it out and re-weld it. No amount of cap welding will improve it.

Best of luck, Chook

or you could do my trick and put a couple of coats of hi strength paint on top of the welds........