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Steel hull and aluminum superstructure
Hi to all,
I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
It used to be called "Datacouple". It's seems to have dropped off
Google's radar screen which essentially means non-existant now. The only references I see are reviews of some old boats that use it. It must still be around somewhere. -- Roger Long "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
I have just double check with my friend who worked as a welder for 35 years
in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
Sorry, but the following is completely wrong. The explosively jointed
bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
Very interesting Roger what you bring. As you said, i've searched also in
internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
That is the stuff.
For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
Roger,
I'm a fan of aluminum. My current boat is made of. I did a lot of work on it to change the gas engine to a diesel one. You can see it at the following adress if interested: www.langevin.biz/marinette34/repowering.htm I just finished today the bill of material for the Roberts 43 and here are the important numbers; Current prices: Aluminum about 2.50 CAN / pound Steel about .050 CAN /pound Since there is less aluminum than steel, but not that much, the cost of material for a Roberts 43 with ballast is the following: -Steel 29000 CAN including ballast, sandblasted inside+outside, isolated with foam for a 28500 pounds hull -Aluminum 57000 including ballast, no paint inside but only under waterline, isolated with foam for a 25000 pounds hull All in all, when the boat will be done there will still be a difference of 30 % in price even if you take into account that the gear is smaller, the engine works less and so on. I compared the resale value of several boats of 43-44 feet worldwide, and there is no significant difference in the future price of resale either. A good boat is a well designed and maintained boat and this is what ultimately command the price. Current median price for either aluminum or steel sailboat is around 197 000 for 43-44 feet. One of my friend hit a low floating container on his way to Europe ... it was a glass boat but the aluminum on my boat is so easily teared apart that i would have had the same problem - big hole and water in ... abandon ship. Since my plan is to circumnavigate, i want to sleep in peace, protected by 5/32 inches of steel at 40 000 pounds/ square inches of resistance and welded at 60 000 pounds/square inches. Every weld on aluminum diminishes the local strenght and this is the problem. Unless they decide to make containers in aluminum :) But i'll truly miss the low maintenance of aluminum. This is why, if feasible, i would like to have the superstructure built of aluminum. Your trick is very interesting, i will think on how to apply it to the design. Thanks very much ! "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
I once saw a 40 something sailboat that had gone aground on an
offshore island. The keel was torn off and one side pushed in about three feet. There was only about 18 inches of the hull that wasn't watertight. It often isn't the numbers strength of the material but the way that the entire structure deforms under load that determines how it fails. (Think of your rubber boat.) If I knew I was going to hit something like a container, I would as soon do it in an aluminum boat of similar structure weight as a steel one. Of course, that would be an expensive boat as you point out. -- Roger Long "André Langevin" wrote in message ... Roger, I'm a fan of aluminum. My current boat is made of. I did a lot of work on it to change the gas engine to a diesel one. You can see it at the following adress if interested: www.langevin.biz/marinette34/repowering.htm I just finished today the bill of material for the Roberts 43 and here are the important numbers; Current prices: Aluminum about 2.50 CAN / pound Steel about .050 CAN /pound Since there is less aluminum than steel, but not that much, the cost of material for a Roberts 43 with ballast is the following: -Steel 29000 CAN including ballast, sandblasted inside+outside, isolated with foam for a 28500 pounds hull -Aluminum 57000 including ballast, no paint inside but only under waterline, isolated with foam for a 25000 pounds hull All in all, when the boat will be done there will still be a difference of 30 % in price even if you take into account that the gear is smaller, the engine works less and so on. I compared the resale value of several boats of 43-44 feet worldwide, and there is no significant difference in the future price of resale either. A good boat is a well designed and maintained boat and this is what ultimately command the price. Current median price for either aluminum or steel sailboat is around 197 000 for 43-44 feet. One of my friend hit a low floating container on his way to Europe ... it was a glass boat but the aluminum on my boat is so easily teared apart that i would have had the same problem - big hole and water in ... abandon ship. Since my plan is to circumnavigate, i want to sleep in peace, protected by 5/32 inches of steel at 40 000 pounds/ square inches of resistance and welded at 60 000 pounds/square inches. Every weld on aluminum diminishes the local strenght and this is the problem. Unless they decide to make containers in aluminum :) But i'll truly miss the low maintenance of aluminum. This is why, if feasible, i would like to have the superstructure built of aluminum. Your trick is very interesting, i will think on how to apply it to the design. Thanks very much ! "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
"datacouple" is actually "dEtacouple" and is very much still around
and used by everyone in that business. take a look at http://www.dynamicmaterials.com/ It seems that ownership of the product has bounced around some, but it is still available. Now, how an individual can buy it -- that's another story. Cheers, Michael "Roger Long" wrote: It used to be called "Datacouple". It's seems to have dropped off Google's radar screen which essentially means non-existant now. The only references I see are reviews of some old boats that use it. It must still be around somewhere. -- Posted via a free Usenet account from http://www.teranews.com |
Steel hull and aluminum superstructure
Hi Michael,
This is very interesting. In fact i found the specification on the page which is MIL-J-2445A http://206.124.2.9/clad/pdf/marine_p...il-j-24445a%22 Now what puzzles me is that they claim that using a bimetallic join reduces corrosion. I thought theese joint were *not* electrically bounded but they are indeed. So you have one big anode sitting on the top of your steel hull now. I think the guess they are taking is the following: A) The steel hull is absolutely and completely isolated from the sea water. Any repair is done diligently B) The superstructure is high enough not to be covered with water I'm ok with condition A but condition B is very frequent on a sail boat. We heel almost all the time and on the ocean the spray is constant. Not sure anymore if it is a good idea but still searching... "Michael Porter" wrote in message ... "datacouple" is actually "dEtacouple" and is very much still around and used by everyone in that business. take a look at http://www.dynamicmaterials.com/ It seems that ownership of the product has bounced around some, but it is still available. Now, how an individual can buy it -- that's another story. Cheers, Michael "Roger Long" wrote: It used to be called "Datacouple". It's seems to have dropped off Google's radar screen which essentially means non-existant now. The only references I see are reviews of some old boats that use it. It must still be around somewhere. -- Posted via a free Usenet account from http://www.teranews.com |
Steel hull and aluminum superstructure
On Tue, 03 Oct 2006 07:50:54 -0400, Michael Porter
wrote: "datacouple" is actually "dEtacouple" and is very much still around and used by everyone in that business. take a look at http://www.dynamicmaterials.com/ It seems that ownership of the product has bounced around some, but it is still available. Now, how an individual can buy it -- that's another story. Cheers, Michael I like their NASDAQ ticker symbol: BOOM! :) cheers, Pete. |
Steel hull and aluminum superstructure
Oh, hello neighbor. I didn't realize you hung around these joints:)
-- Roger Long "Michael Porter" wrote in message ... "datacouple" is actually "dEtacouple" and is very much still around and used by everyone in that business. take a look at http://www.dynamicmaterials.com/ It seems that ownership of the product has bounced around some, but it is still available. Now, how an individual can buy it -- that's another story. Cheers, Michael |
Steel hull and aluminum superstructure
From 2 $ in Nov 05 to about 31 $ today... it is much more like a supersonic
BANG :) "Pete C" wrote in message ... On Tue, 03 Oct 2006 07:50:54 -0400, Michael Porter wrote: "datacouple" is actually "dEtacouple" and is very much still around and used by everyone in that business. take a look at http://www.dynamicmaterials.com/ It seems that ownership of the product has bounced around some, but it is still available. Now, how an individual can buy it -- that's another story. Cheers, Michael I like their NASDAQ ticker symbol: BOOM! :) cheers, Pete. |
Steel hull and aluminum superstructure
Roger,
I'm still discussing with people at SPURIND and another company. I thought of using a joint and it would work but what if lightning strike and i don't have electrical connectivity between the superstructure and the hull ? The mast could still be interconnected to the hull but it is a risk.... Better have electrical bonding between the two. i'm currently discussing price, i'll post the findings. cheers "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
Roger Long wrote:
It used to be called "Datacouple". It's seems to have dropped off Google's radar screen which essentially means non-existant now. The only references I see are reviews of some old boats that use it. It must still be around somewhere. Detacouple or Deta-couple Evan Gatehouse |
Steel hull and aluminum superstructure
You would have plenty of electrical connection through the bolts.
They could be isolated but there would be little need to since they would be inside and dry. You would probably want to use stainless bolts anyway. Even if you had the house isolated, lightning current would jump over the small gap at the gasket like it wasn't even there. The people wringing their hands over dissimilar metals forget that stainless and aluminum are quite far apart but the millions of highly stressed and critical stainless rigging fittings attached to the millions of sailboat masts out there function for years and decades without a problem. -- Roger Long "André Langevin" wrote in message ... Roger, I'm still discussing with people at SPURIND and another company. I thought of using a joint and it would work but what if lightning strike and i don't have electrical connectivity between the superstructure and the hull ? The mast could still be interconnected to the hull but it is a risk.... Better have electrical bonding between the two. i'm currently discussing price, i'll post the findings. cheers "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
André Langevin wrote: Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André There exist some bimetal strips that are used to join the steel to the aluminium. Of course, you can't weld those two together. If you want an aluminium superstructure because of its lower weight, then maybe you could also consider a plywood deck and house. -mc |
Steel hull and aluminum superstructure
Hi Roger,
Here is the quote i've received. Indeed quite costly for an amateur. My Roberts 43 would need at least 100 feet of this so about 6000 $ of material. Item Qty Thickness Width Unit Price USD /lin ft Total Price USD /item 1 12' 0.75 * 2" $62.13 $706.56 The more i think to your proposal the more it make sense. And it would but my Roberts 43 to a very high level of stability given that i would save me about 2000 pounds and the equivalent lever-arm since it is farm from the CG. Another advantage is that it is so easy to keep the rust out of the hull but much less on the decks since there is a lot of holes, fixtures and contact with items like anchor, spi pole and so on. It definitely need more reflection ! Thanks ! "Roger Long" wrote in message ... You would have plenty of electrical connection through the bolts. They could be isolated but there would be little need to since they would be inside and dry. You would probably want to use stainless bolts anyway. Even if you had the house isolated, lightning current would jump over the small gap at the gasket like it wasn't even there. The people wringing their hands over dissimilar metals forget that stainless and aluminum are quite far apart but the millions of highly stressed and critical stainless rigging fittings attached to the millions of sailboat masts out there function for years and decades without a problem. -- Roger Long "André Langevin" wrote in message ... Roger, I'm still discussing with people at SPURIND and another company. I thought of using a joint and it would work but what if lightning strike and i don't have electrical connectivity between the superstructure and the hull ? The mast could still be interconnected to the hull but it is a risk.... Better have electrical bonding between the two. i'm currently discussing price, i'll post the findings. cheers "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
Steel hull and aluminum superstructure
If you are worried about rust, I would suggest making the deck of
aluminum as well as the cabin trunk and having the flange arranged at the deck edge like a fiberglass boat. Any leaks that did develop would then be out where they would most likely just run down the side of the hull. The area under the cabin edge would be very clean and easy to finish off. A bedded guard rail would protect the edge of the gasket and keep water away from the area where two kinds of metal are in close proximity. The best thing of all would be the fact that sandblasted aluminum plate without paint is an excellent non-skid surface. -- Roger Long "André Langevin" wrote in message ... Hi Roger, Here is the quote i've received. Indeed quite costly for an amateur. My Roberts 43 would need at least 100 feet of this so about 6000 $ of material. Item Qty Thickness Width Unit Price USD /lin ft Total Price USD /item 1 12' 0.75 * 2" $62.13 $706.56 The more i think to your proposal the more it make sense. And it would but my Roberts 43 to a very high level of stability given that i would save me about 2000 pounds and the equivalent lever-arm since it is farm from the CG. Another advantage is that it is so easy to keep the rust out of the hull but much less on the decks since there is a lot of holes, fixtures and contact with items like anchor, spi pole and so on. It definitely need more reflection ! Thanks ! "Roger Long" wrote in message ... You would have plenty of electrical connection through the bolts. They could be isolated but there would be little need to since they would be inside and dry. You would probably want to use stainless bolts anyway. Even if you had the house isolated, lightning current would jump over the small gap at the gasket like it wasn't even there. The people wringing their hands over dissimilar metals forget that stainless and aluminum are quite far apart but the millions of highly stressed and critical stainless rigging fittings attached to the millions of sailboat masts out there function for years and decades without a problem. -- Roger Long "André Langevin" wrote in message ... Roger, I'm still discussing with people at SPURIND and another company. I thought of using a joint and it would work but what if lightning strike and i don't have electrical connectivity between the superstructure and the hull ? The mast could still be interconnected to the hull but it is a risk.... Better have electrical bonding between the two. i'm currently discussing price, i'll post the findings. cheers "Roger Long" wrote in message ... That is the stuff. For homebuilding, I would just build a flatbar flange at the base of the superstructure. Bolt and aluminum flatbar to it and then build the aluminum superstructure on top. Unbolt after it's done, lift, and insert a suitable gasket material. Then bolt it back on. Being able to remove the superstructure would have a lot of advantages if you had to do major repair on the interior. Actually, I would build the whole boat out of aluminum. Stronger at the same weight, more likely to deform in a way that stays watertight in event of major damage, and easier to drill for temporary patches with hand or battery powered tools. I'd much rather go up on a reef in a far away place in an aluminum boat than a steel on unless the latter was large enough to carry a full welding outfit. Also, less compass issues with an aluminum boat. -- Roger Long "André Langevin" wrote in message ... Very interesting Roger what you bring. As you said, i've searched also in internet but there is not much reference. I will talk with a local machinist also and keep you posted. There is this company though: www.spurind.com but it might turn out very costly since it seems to be a specialty. André "Roger Long" wrote in message ... Sorry, but the following is completely wrong. The explosively jointed bimetallic strips have a long and successful history. The aluminum is welded to the aluminum side and the steel to the steel side. The strips simply seem to have become hard to locate, at least via the web. Regular steel and stainless steel are often joined. Problems can occur, especially if submerged in salt water but you'll see mild steel / stainless joints on fishing vessels that have been going for years and years. True, you can't weld aluminum directly to either. How do I know about aluminum superstructure on a steel hull? I did it on this boat: http://www.bbsr.edu/About_BBSR/Facil...herbird_ii.htm -- Roger Long wrote in message ... I have just double check with my friend who worked as a welder for 35 years in a shipyard that build commercial, coast guard vessels, battleships and drilling platforms. If you have an aluminums structure welding steel plates on or doing the reverse was not in practice. Aluminums and mild steel or cold rolled steel are not compatible. The same thing applies to welding stainless steel. What takes place is a white inter granular corrosion that is hardly visible to the naked eyes. Given time the white corrosion will cause a structural failure. Not to mention the saline atmosphere at sea that will accelerate the process. "André Langevin" wrote in message ... Hi to all, I am a newcomer on this newsgroup and you'll see me around as i'm starting the construction of a new boat. I currently have a 34 feet powerboat in aluminum and my nest boat will be a 44 or 45 steel sailboat. I'm looking at building a Bruce Roberts design and i would like the deck superstructure to be in aluminum. I've seen many commercial boat done this way and even old Coast Guard patrol boat of 30+ years old without any corrosion problem so it is something i'd like to do. But i can't find any industry that carries the special strip that isolate both metals but still permit to weld them both. Does someone ever see this ? André |
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