Steel Boat Build

On reviewing your posts I see that you started out with a drawing of a boat that resembled a displacement hull. A slower displacement boat is suitable for 1/8" steel and possibly a frameless design as the panels can all be curved and convex. You have shifted to a planing design. This means alum or ply as best choices, for lighter weight. I think a smaller hull, 5 metres, is best for a start. A badly welded alum boat will never sell, so get it right the first time. Boat #2 will not plane off as well as the longer #1, all else equal. Stability??? You need to define exactly what you mean, and discuss it with the designer. If you are on smallish Irish lakes and rivers, the requirements are quite different than open ocean. You have had lots of good advice from some experienced guys. Spend a lot more time deciding what you really need, and what you are capable of doing. Get a proven design from a designer who you can communicate with. Do not diverge from the plans without consulting the designer. Most of all, have fun. Nothing beats building a good boat!

 

Thanks for your comments Kenora Kid.
What I mean regarding stability, is a boat that does not rock all over the place
at the slightest movement of the sea, I also understand thumping, and would rather be thumped a little as slowing down helps this.

Agreed that inland waters are a bit different, but not when your talking about Loch Corrib, terrifying waves that swamp have swamped and unfortunately lives have been lost there.

I sent the designer of the boats #1 and #2 an email, I guess he is the man with the most intimate knowledge of them and their abilities, would be nice to build both and compare them on the water.

Hope to hear more comments

Thanks, john

 

It is difficult to tell from the picture and description
Boat number one, appears to have two chines, ie slightly rounded as per the plywood example. This is not a good planing design.

Boat 2, APPEARS to be a single chine, at least from the picture. Though the description suggests 2 additional planks

If Boat 2 is a mono hull and the chine width is the same as the outside chine width of the multichine boat number 1, Boat 2 will plane easier than boat one.

Of course the deadrise will make a difference as well so it is hard to define "all else equal"

It is sometimes worthwhile to sit back and consider at the millions of planing hulls in the length that you are looking at.

Single chine, monohull, I would guess 98-99%
Multichine, as Boat 1, the rest.

Hundreds of designers build planing hulls in a mono style. Follow their lead.

 

Hi Barry
All points taken, I will be keeping an open mind and am not in a hurry
to invest until I am happy I have done my homework.
I stepped out the dimensions of the two boats above and am leaning
towards the smaller one, as I am a one man band getting time to
attend to every nut and bolt will make the build a long one, which will
be governed mostly by how fast the welding proceeds.

And in that regard, why does no one use stainless steel mig wire to weld
aluminium together.
I know they are dissimilar, but so is mild steel and stainless and they can be
easily welded together, I once tried a stainless rod on aluminium, just to see,
it turned out extremely smooth, did a test to pull it apart, the aluminium
tore and as expected the welds were intact.
I guess the very different tensile and other properties of the two metals
will result in extra stress where they do not bend together but instead the weaker one tears gives out.
You would think by now too that someone has not designed a control able wire feed system for tig welding,
even it only used the current filler rod lengths, would make long runs a dam sight easier when one can
move along without worrying about keeping the rod in the zone.

Regards, john

 

psst!If you can join aluminum to stainless using a stainless rod don't tell anyone. PM me and we will get rich, haha
I would imagine that if you struck a mig arc with stainless on the aluminum that the aluminum would just melt out as its melting temperature is much lower than stainless.

Stainless to steel is easy as stainless just contains nickel and chromium in small amounts depending on the alloy.


There are a couple of automatic tig feeders.
One that is "hot" ie there is some current running down the wire but still takes a tungsten electrode

and the other is a "cold" which is just a tungsten electrode and you wire feed the aluminum into the puddle

I saw them at Fabtech a few years ago. Aluminum, stainless and hard surfacing wire were the target processes

 

Hi Barry, when I get some stainless wire I will have a go at welding aluminium, but for real, I can't actually remember whether the rod I used was 312 or 316 or other, but the weld was like the best of the mig stuff, I don't think a mig set for small stainless wire will be set high enough to melt aluminium away,
as far as I know in most cases you require more current to spray aluminium, would a stainless steel set up for .8 wire wire not run cooler.
After hearing about the hot and cold feeders, I see visions of a tig torch in one hand,
a mig gun feeding wire in the other.

Had a look at a few online videos of mig welding aluminium, and I give in to the fact that this is the way to go where possible, and again I am reminded that so much actually rests on the hardware used, and I could kick myself, I sold a Sebora mig, that I was not using, and with it went the spool gun I also never used other than for testing, and that particular welder had thee most stable arc I ever witnessed, and could spray so precisely.
It was actually designed for the coach building industry, welding alloy chassis and structures in buses etc.
After that I bought some bigger welders for the next job, and none of them were much good at aluminium, lesson learned and am afraid I will have to find another welder of similar ability.

Regards, john

 

The company was tiptig international . You had a tig gun, and the wire fed over top into the puddle.
One hand operation, but I cannot remember how the arc and feed was controlled

 

I might have solved my hull/boat design queries,
Self righting test, great hull pictures, https://www.youtube.com/watch?v=Y2i1fOJ-itw
Sea trials, https://www.youtube.com/watch?v=N134TJlFjsU
I must say this design looks like the ones I created and lost, not that modern,
but I will take function and safety any day, he must have spent a lot of time looking at the Irish Naval vessels,
his design has a military look about it.
Anyone care to guess what one costs.

Regards, john