another idiot with mad ideas, new boat build

[MapisM]

The concave shape is part of the design to help reduce drag.

Rob, do you know if the last sentence above was strictly referred to non-planing speed?
Because if he meant that such design can reduce drag also at 25 kts, that wouldn't make any sense.
I'd rather expect the opposite in fact, at anything above 12/14 kts.

 

[rustybarge]

It's called the 1300GT and you can see it on www.tryviajachten.com and then clicking on Snelvarend. It weighs 11 tons empty but,what they don't tell you on the website is that it is only the hull that is steel (thin section at that) and the top sides are aluminium

I seem to remember that the destroyers that went to the Falklands are built like that; steel strong and cheap to repair, ally light but seriously expensive.

If the performance figures on the Bonito seem to good to be true.........

 

[Robg71]

Rob, do you know if the last sentence above was strictly referred to non-planing speed?
Because if he meant that such design can reduce drag also at 25 kts, that wouldn't make any sense.
I'd rather expect the opposite in fact, at anything above 12/14 kts.

I am waiting for more reports back. What I know about hull design I can write on a postage stamp. I was hoping there may have been a more knowledgeable expert amongst our midst.
But will find out one way or the other. Off to holland in a few months to see the first one being built and hopefully some through water modelling etc. what i wont be is a guinea pig.

 

[Robg71]

Forgot to mention, the 46ft version, apparently comes in around the 17ton area.

I had a couple of emails back and forth with a Bruce Roberts, looking at a couple of his designs, and also with the started one on find a fishing boat.

His euro 14 design he reckons comes in at 88k for steel, built and 175 for Ali.
With twin 380 capable of 15 knots and 18 in Ali.
Basic steel kit price was about the same. His were 4mm and 6mm plate.

 

[rustybarge]

Forgot to mention, the 46ft version, apparently comes in around the 17ton area.

I had a couple of emails back and forth with a Bruce Roberts, looking at a couple of his designs, and also with the started one on find a fishing boat.

His euro 14 design he reckons comes in at 88k for steel, built and 175 for Ali.
With twin 380 capable of 15 knots and 18 in Ali.
Basic steel kit price was about the same. His were 4mm and 6mm plate.

Those numbers sound exactly right.
Aluminium is very very expensive, and needs an expert to weld it; worth considering if you need repairs on the hull.
My son wanted to do an ally welding course; 18 months and €18k........apparently if you over heat the weld bead the ally crumbles and cracks, so it takes a qualified expert.

So how much does a coded aluminium welder charge per hour?

Every engineering solution is a compromise .

 

[Robg71]

Dont 100% agree there. Anybody can pick up a mig welding set and weld. There is little skill involved compared to tig, gas or manual metal arc. (Not saying its easy, but for a novice a lot easier than any other form)
Even ali is not that bad. Cleanliness is the key with ali. I think once shown a few teqniques then its fairly easy to get the knack off. Mind you, the govt picked up the bill for my metal work training. Two and a half years at the royal school of military engineering, watching pools of molten ali bounce across the floor
My instructor use to cut a beer can in two and gas weld it back together. A proper craftsmen... No way could i do that... Not ever.....

If you overheat the weld bead it melts to the floor. Difference with steel,is steel will warn you, in colour change and boiling off (porosity)

 

[vas]

My instructor use to cut a beer can in two and gas weld it back together. A proper craftsmen... No way could i do that... Not ever.....

as a completely amateur arc welder, I'm very impressed by that. Would really like to see a video of that

sorry of the of topic, I guess I also wouldn't bother with ali, you can invest the 80K elsewhere...

cheers

V.

 

[Robg71]

as a completely amateur arc welder, I'm very impressed by that. Would really like to see a video of that

sorry of the of topic, I guess I also wouldn't bother with ali, you can invest the 80K elsewhere...

cheers

V.

A oxy/actylene torch that would struggle to light a woodbine.
I suppose he cheated a little, by rolling a small flange on it. Still impressive though.
Apparently coke cans were too thin...

80k goes a long way towards other gear. My thoughts exactly.

 

[Robg71]

Just found another company who has built a 46 ft bonito. Did 21 knots on a pair of 300. And came in around 17ton.
I am struggling to justify the fifty footer, to myself. I did some rough drawings and measurements, and think 46 should be more than enough.
Hopefully

 

[rustybarge]

Just found another company who has built a 46 ft bonito. Did 21 knots on a pair of 300. And came in around 17ton.
I am struggling to justify the fifty footer, to myself. I did some rough drawings and measurements, and think 46 should be more than enough.
Hopefully

Just looking at the Swift trawler 44 vs Grands Banks 42 (45' loa).....

Old classic semi-discpl. GB 42: 16 tons/twin 375......max.17 kts/2600 revs.....cruise:13 kts/2200rev

New hull shape St44: 11 tons/ twin 300...... Max.24 kts/3600 rev......cruise:14kts/2600 rev

Even with a S/D hull it's weight, weight, weight....or rather the lack of.....

 

[Robg71]

For any intersted folks, the latest drawings I have... Hot off the 3d cad machine computer thingy

 

[vas]

hm, v. odd aft section. Thoroughly confused... What's happening there, there's an integrated bathing platform with solid hull under it, but how the hell do you get to the aft deck from the bathing platform? Steps get you further ahead than they should. Don't like the aft end of the aft deck (transom you call it, right?) Elevations are bit confusing as well...
That looks like sd hull right?

Er, it's not that it doesn't look good, just confusing on the details.

V.

 

[rustybarge]

hm, v. odd aft section. Thoroughly confused... What's happening there, there's an integrated bathing platform with solid hull under it, but how the hell do you get to the aft deck from the bathing platform? Steps get you further ahead than they should. Don't like the aft end of the aft deck (transom you call it, right?) Elevations are bit confusing as well...
That looks like sd hull right?

Er, it's not that it doesn't look good, just confusing on the details.

V.

I agree. The aft circular seat looks about 3' form the stern, all wasted space.

Why not move further back so that it forms the transom? That way you don't need the massive walkways on both sides at the stern.

 

[Robg71]

He says lots of details to be added. But i think more the overall shape is finalised. I am still unsure about the lower hull section.
There would be gates in to the aft deck from the swim platform etc. I think i prefer the more open look.

Edit
Also, these kits are pretty much semi custom. If things are there you don't like, they are easily changed. Its only a mouse klick away. Especially bearing in mind its your cash (or mine) your spending

 

[MapisM]

Er, it's not that it doesn't look good, just confusing on the details.

+1.
I'd guess that they just took a superstructure drawing that they had in their files, glued it upon the hull, and the rendering software did the rest.
There's surely a lot of work still missing, to get a working drawing.
One thing I'd ask them is if they made any actual tank test of that hull form - even if just with scaled models, of course.

 

[Robg71]

I think that a wide open aft deck, instead of the seating and an extra wooden bolt on style swim platform may be the way forward for me. As maximises all usable and outdoor space too...
Its also safer for kids, and drunk big kids

 

[Robg71]

One thing I'd ask them is if they made any actual tank test of that hull form - even if just with scaled models, of course.

I think that would be one thing i would insist on, or even consider looking at for piece of mind that you are getting what you think. Before laying cash on the table.

 

[rustybarge]

I think that would be one thing i would insist on, or even consider looking at for piece of mind that you are getting what you think. Before laying cash on the table.

I understand that you're looking for a steel boat.(i live on one)
In comparison to plastic steel is s lovely material, would you live in plastic house........?

But: well know makes of boats have good re- sale values. Look how little Bruce Roberts designs sell for, even thought they are well know to home builders, the ordinary boat owner has never heard of them.

So: did you ever consider buying a hull for home finishing from a well know manufacturer? With the recession in full swing they might be delighted to sell a hull/ superstructure. ( I've just bought a completely bare small cat hull for my latest project)

I'm no expert but i've heard of: ( just hull)
Antaris
Aquanaut
Lissen
Privateer
...err I'm struggling now!

How about an Aquastar hull?
Or:
Hardy
Seaward
Nelson Dale


Just a thought.....

 

[Robg71]

Tbh, if i build this, i wont sell it. You can bury me in it.
If i did everything in life just for resale, i would never do anything. I certainly wouldn't have done my boat how i have. If she sells now for her asking price, i will still be out of pocket. But that was not the object of it.
I totally see your point, but i don't live by every penny a prisoner...

I could take a design to Merwede and have them build it, but nobody would know who they are either. (Possibly one of the biggest dutch shipbuilders, for big offshore vessels)
I have found a nice friendly boat yard in wales, seems right up there street, and if its done to lloyds or dnv, mca spec, then to me no problem. I save a bucket full of money because it does not have a known brand name, but quality should show through anyway... If its done right....

 

[rustybarge]

Tbh, if i build this, i wont sell it. You can bury me in it.
If i did everything in life just for resale, i would never do anything. I certainly wouldn't have done my boat how i have. If she sells now for her asking price, i will still be out of pocket. But that was not the object of it.
I totally see your point, but i don't live by every penny a prisoner...

I could take a design to Merwede and have them build it, but nobody would know who they are either. (Possibly one of the biggest dutch shipbuilders, for big offshore vessels)
I have found a nice friendly boat yard in wales, seems right up there street, and if its done to lloyds or dnv, mca spec, then to me no problem. I save a bucket full of money because it does not have a known brand name, but quality should show through anyway... If its done right....

The low drag hull on the Greenline boats seems to be what your naval architect is talking about, but notice It's not a concave aft section, but it is very flat with a sharp bow entry.....

Got a very good write up in MBM, seemed to handle the chop well.
They're quoting 23 kts with twin 380/13 tons/ 45 hull lenght.

http://greenlinehybrid.com/Greenline-48-specifications