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Post by superwag on Jun 28, 2020 0:43:33 GMT
Nice work. Given the cost of fabrication, I would recommend a higher grade of stainless steel. 316 grade has a fairly low pitting resistance number PREN and pitting starts at temperatures above about 10 deg c in chloride environments. Chinese 316 is typically borderline in meeting atomic constituent requirements, as Nickel and Chromium ingredients are expensive, and China aims for minimal quantities to meet the grade description, which typically has a range of a few percentage points. Their carbon content control is often dubious resulting in ferrous bleeds. As a metallurgical engineer, I frequently had to fail Chinese 316 grades as they did not meet minimum metallurgical requirements once we did atomic absorption spectrophotometry on samples to confirm quality for service. You could switch to 2205 duplex stainless or for super durable parts without any rust stains, pitting, crevice corrosion etc 2507 super duplex. It’s what’s used in naval service. Material cost would be a slight increase, but given that majority of cost is in fabrication, it would be a sensible upgrade in my opinion. It certainly worked well on my 35 footer. All the best. Looking forward to seeing some of these boats sailing.
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pete
Junior Member
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Post by pete on Jun 29, 2020 14:25:00 GMT
Nice work. Given the cost of fabrication, I would recommend a higher grade of stainless steel. 316 grade has a fairly low pitting resistance number PREN and pitting starts at temperatures above about 10 deg c in chloride environments. Chinese 316 is typically borderline in meeting atomic constituent requirements, as Nickel and Chromium ingredients are expensive, and China aims for minimal quantities to meet the grade description, which typically has a range of a few percentage points. Their carbon content control is often dubious resulting in ferrous bleeds. As a metallurgical engineer, I frequently had to fail Chinese 316 grades as they did not meet minimum metallurgical requirements once we did atomic absorption spectrophotometry on samples to confirm quality for service. You could switch to 2205 duplex stainless or for super durable parts without any rust stains, pitting, crevice corrosion etc 2507 super duplex. It’s what’s used in naval service. Material cost would be a slight increase, but given that majority of cost is in fabrication, it would be a sensible upgrade in my opinion. It certainly worked well on my 35 footer. All the best. Looking forward to seeing some of these boats sailing.
Hi, interesting points (in light of my SS bolt issue above) - can you put some data behind the observations you make please? - how much more expensive is 2205 duplex stainless per kg and are all other attributes identical - e.g machinability, strength etc? What is the supply chain for this like, is it widely available and no huge minimum orders direct from mills required? Only reason i ask is that i understood 316 was the best material for recreational boat use in terms of compromising cost vs longevity, and any corrosion you just needed to 'manage'.
Keen to see what you have made/ had made for your vessel out of this stuff. Is it only for submerged items, (i.e. the lower rudder gudgeon/pin) or for all stainless parts in service on the boat?
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Post by superwag on Jun 30, 2020 10:02:59 GMT
To save me typing a lot of stuff, here’s some info from a company called Metforce. I’ve got superduplex chainplates, 2205 pushpit and pulpit, and lots of other fancy stainless. Titanium is a practical option for chainplates nowadays too. It is difficult/expensive to weld but it does come in sheet form if using water jet cutting and laser to a lesser effect due to heat generated and the phase transformations which occur in common titaniums. But the benefit is almost endless life in marine environment. The soviets built entire nuclear submarines out of it once upon a time (from memory Alfa class, 45+ knots top speed submerged, diving to 3,000+ feet). To date, nobody has even come close to matching it. But that’s a complete tangent. What happened to your bolt? Anyway, below.
BASIC DIFFERENCES BETWEEN 304, 316/L & 2205 Before we start – Metforce assumes no risk and shall not be subject to any liability for any indirect, special, incidental, or consequential damages or for any loss of profits sustained by buyers or any party dealing with buyers in connection with the information contained in this report or resulting from the use or application of any of the recommendations contained in this report. The buyer is ultimately responsible for making all decisions and applying the appropriate technology based on good engineering practices. What type of stainless steel? 304 Also known as 1.4301, this material has a full Austenitic structure and has sufficient corrosion resistance to act as a stainless steel in most general environments. Used predominantly in kitchens, transport, hospitals, architecture, etc. 316L Also known as 1.4401 (or 1.4435 for 316L), this material is also has a full Austenitic structure and is superior in corrosion resistance to grade 304 due to a higher Nickel content and also added Molybdenum, which also makes this material more expensive. Used mainly in more corrosive areas such as marine environments or more polluted or acidic areas. 2205 Also known as S31803 or 1.4462, this material is a stainless steel which has enough Chromium to form an Austenitic crystal structure and therefore it consists of a mixed structure which is both Austenitic and Ferritic. With the controlling of Nitrogen in the composition, the structure is around 50% Austenite and 50% Ferrite. Failure to control the Nitrogen may hinder the Austenite formation which will affect the weldability and other properties. Because of its high Chrome content, it has superior corrosion resistance in most environments to grade 316 or 316L. Invented only recently (in the last 30 years) it is replacing grade 316 in many marine environment applications. How good is it in marine conditions? Let me illustrate using tables by SWCC.gov: In natural sea water at 50 deg C - E pit mv (resistance to pitting) 304L 94 316L 154 2205 629 For coastal areas 2205 is far superior to grade 304, 316 or 316L It may still stain if not maintained, but pitting will take longer to occur. What does it contain? 304 316 2205 Chrome 18% 16% 21% Nickel 8% 10% 4.5% (min %) Molybdenum - 2% 2.5% What are the mechanical properties? 304 Ultimate Tensile MPa 515 0.2% Proof Strength 205 Hardness Brinell (max) 200 316L 2205 515 700 205 570 200 290 Differences to machine and cut? Machining of 2205 is harder than 304 Cutting speed is about 20% slower on or 316 and you will use more consumables. 2205. Clamping products, such as glass clamps and spigots? From our experience, “Splaying” is around 50% less than 304 or 316/L when using 2205. Cost? Generally 2205 costs around 20% more than 316, and 316 is around 40% higher than 304.
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pete
Junior Member
Posts: 56
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Post by pete on Jun 30, 2020 10:22:20 GMT
Globe 5.80 Chain plate and Rudder gudgeon SS package: After considering the manufacturing options and the critical nature of Rudder hardware, we have decided that CNC machining those components from Stainless Steel solid Block, rather than welding offers the best quality, reliability and less corrosion risk. Assessing three different suppliers, a decision has been made to use a Chinese engineering company to produce these components. World class engineering at a reasonable price is the result. Price is Fixed on the first 50 units. The first prototype set for checking will be delivered the first week of July. Items in the 5.80 SS Package include: 1. Top Rudder Gudgeon and pintle set, Fully CNC machined from solid 316 Stainless steel stock, including machined lock Bolt drilled and pinned. Globe 5.80 Engraved individual HULL number. 2. Lower Rudder Gudgeon and pintle set, fully CNC machined from solid 316 Stainless steel stock, including machined Lock Bolt drilled and pinned. ..... Hi Don,
Few questions about this - looks good in general, pricing for machining that amount of stainless seems pretty keen.
1. Reviewing the drawings, I may be missing something obvious, but the hull portion of the rudder pintle/gudgeon - which part is this in the drawing pack?
2. I notice you have a lot of 8.5 and 10.5mm holes - 8 and 10mm bolts are the norm in the EU (can't comment for other areas), finding a 8.5mm stainless bolt in a suitable grade seems challenging - 0.5mm seems a large amount of clearance for a bolt hole (with no centering forces from a countersink for example), any chance this can be reduced to a more precise fit?
3. The attachment detail for the inner forestay, how is this done? through deck into the bulkhead E as per the drawings from Janusz? If so that chainplate might need additional features to be able to seal it effectvely. i.e. a horizontal plate welded below or at the bend line that would allow the slot through the deck to be sealed effectively under the plate. A better soltuion might be possible with a bit or redesign that only has fastening bolts through the deck with a backing plate that hits the bulkhead E instead?
let me know if this makes no sense and i'll try to do a quick sketch of what i mean instead!
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Post by Admin on Jul 1, 2020 1:39:29 GMT
HI....super wag....thanks for all the input...Jane and I have been deeply involved with China boat building on the Pearl River Delta for 15 years. this is the boat building centre of China...we will use the same 316 SS as all the other multi million$$ builders that is great for a little Globe 5.80..so no high tech metals..just 316..the last boat we delivered was 24mt US$3.5mill covered in 316SS PETE...I have attached the Rudder gudgeon pintle drawings..the top set has the flat plate bolting to the transom...the bottom set has the long piece onto the rudder and short piece onto the rudder skeg...both are SMALL SHEET drawings......for bolt clearance .5mm is a standard and used by Janusz and perfectly fine for the 5.80 engineering..The INNER FORESTAY through bolts the double deck beam and you will not lift that off the deck . You would lift the deck any other way. Easy to cut a sealing deck plate so we will,and weld that on, mainly cause it will look good so thanks ..you can see that in the new drawing...Very cool SS8.pdf (162.18 KB)
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pete
Junior Member
Posts: 56
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Post by pete on Jul 1, 2020 11:01:46 GMT
PETE...I have attached the Rudder gudgeon pintle drawings..the top set has the flat plate bolting to the transom...the bottom set has the long piece onto the rudder and short piece onto the rudder skeg...both are SMALL SHEET drawings......for bolt clearance .5mm is a standard and used by Janusz and perfectly fine for the 5.80 engineering..
Hi Don, regards the hull portion of the gudgeon/pintle - ignore me, its in your original drawing pack on google drive, I just completely missed it! Clear now, thanks.
Yeah the strength was not my concern here - just being able to effectively seal it. (to protect all the expensive plywood now sitting in the shed once its in a boat shape!) The sealing piece welded on sounds like a good solution, thanks.
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brucel
Junior Member
Posts: 54
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Post by brucel on Sept 29, 2021 2:06:21 GMT
What was the specification for the 12mm keel bolts? I have seen it some where 12mm * X stainless steel 316 did we need a certificate or some thing on what they are?
I commented here as i feel this thread needs a bump for the talk on compulsory stainless steel packs (still waiting for next discount round don..), cutting and welding the keel and bedding the keel.
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Post by captdan on Oct 1, 2021 0:41:36 GMT
What was the specification for the 12mm keel bolts? I have seen it some where 12mm * X stainless steel 316 did we need a certificate or some thing on what they are? I commented here as i feel this thread needs a bump for the talk on compulsory stainless steel packs (still waiting for next discount round don..), cutting and welding the keel and bedding the keel. Hi brucel, From my understanding, we need to supply the manufacturers engineering specs for the bolts. This would include their minimum tensile strength and grade etc. You can find the documentation that is required where is says "Download Keel PDF instruction sheet here…" Here is the link: www.classglobe580.com/class-registration/
Cheers
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Post by Admin on Oct 5, 2021 14:30:25 GMT
What was the specification for the 12mm keel bolts? I have seen it some where 12mm * X stainless steel 316 did we need a certificate or some thing on what they are? I commented here as i feel this thread needs a bump for the talk on compulsory stainless steel packs (still waiting for next discount round don..), cutting and welding the keel and bedding the keel. We need to wait until the next group of builders are waiting so we can order many sets to get the price down.. ....but also not hold up builders ..THNX!
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