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This Aluminum Hull: Is it Thick Enough?

Discussion in 'General Yachting Discussion' started by StuartT, Oct 6, 2015.

  1. olderboater

    olderboater Senior Member

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    Click on their name and then on Start a Conversation. PM's here are called conversations. If you can't find their name to click on, just go to your inbox at the top and Start a Conversation and it will allow you to enter a name.
  2. StuartT

    StuartT New Member

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    I got a reply from rmjranch.

    "I could have my Naval Architect do it but they charge $250 per hour."

    Probably best to stop worrying about this and if I do make an offer, I will have plenty of opportunity to have a surveyor do the analysis for me as part of the purchase contingencies.

    Thanks for your thoughts and input everyone.
  3. tristanrowe

    tristanrowe Member

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    Times are certainly changing, but its not all bad - there are still highly skilled and passionate boat builders out there and RH is no exception.

    Back on topic, there are plenty of much larger sailing yachts out there bouncing off rocks at speed (all be it mostly the keel) with the same plate thickness and they are not littering the bottom of the deep blue sea.
  4. StuartT

    StuartT New Member

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    For those of you interested in the steel vs. aluminum comparison, Michael Kasten of Kasten Marine Design has written an extensive collection of articles on boat building and design. Many of you might find his website very interesting. http://www.kastenmarine.com/articles.htm

    Of specific interest to me is this article. http://www.kastenmarine.com/alumVSsteel.htm. It detail the subject of alloy vs. steel. Plus it summarizes making choices between the two metals. My take away from reviewing his material is that while the 72' aluminum trawler I am interested in with 1/4" hull plate might very well be adequately designed, the other 60' steel trawler I am considering with a combination of 1/4 and 3/8 plate should be a considerably stronger boat, albeit a lot heavier. And that coincides with what I do know. The specs show the 72' at 50 tons, the 60' at 70 tons. Factoring in the lengths, that makes the 60' weigh the equivalent of 84 tons if it were stretched to 72', or 68% more. No question here in my mind as to which boat is stronger unless one of the designs is poorly engineered.
  5. Capt J

    Capt J Senior Member

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    Yes and no. The steel boat will be stronger when built and much heavier. Usually steel is only used for displacement hulls where speed is limited by hull length and design. Aluminum typically for faster vessels where weight is a concern. That being said, how strong are the 2 boats 10 years/20 years/30 years down the road when you factor in wastage.
  6. StuartT

    StuartT New Member

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    Your second sentence is the point I am making, and that is definitely a yes. There are a lot of reasons in the article by Michael Kasten to choose aluminum, not the least of which is resale value. The article I included on alloy vs. steel addresses my original question, the answer to which I think I now have.
  7. Capt J

    Capt J Senior Member

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    Plate thickness as everyone else has mentioned depends on the amount of ribs and reinforcement behind the plates. I am not the authority on Aluminum hulls, but do know that if the aluminum hull is too stiff it will cause cracking so there needs to be some give and flexing there. I did manage/maintain/run a 58' Striker SF and it had a plate thickness of 3/8" and was considered over-built. I also have some 90-105' Browards and they used 3/8" mostly (If I remember correctly) with some 7/16" and larger in high stress areas like near the props, engine beds etc. The main thing you need to be careful of with aluminum hulls is not to drop any copper/brass/steel parts/tools etc. in the bilge and forget about them. Standing saltwater is not a good idea either.
  8. karo1776

    karo1776 Senior Member

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    StuartT... sounds like rmjranch has dwg files or another format that needs a drafting program to access, and cannot access himself. Well it was worth a shot for you, and the owner got a little attention for his boat on the market too. My guess is the aluminum boat is stronger but not as forgiving for inexperienced repairs.

    If it was me I would nearly always pick an aluminum boat over steel... except if the size was much larger than here I think Aluminum is the most perfect of the practical metals to build boats.
  9. karo1776

    karo1776 Senior Member

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    A final comment. I do not think as a user you will normally be able to tell the difference between and aluminum and steel boat day to day. Perhaps the steel is more abrasion resistive and better at taking grounds and the like. Perhaps the aluminum might be better for day to day resistance to hard bumps against the dock or something without dents. The aluminum will be easier to maintain inside like bilges as usually they are not painted and the steel on the outside or bottom... but day to day it will not matter.

    I know of no one purposefully banging into things or running aground (usually that will take out the running gear and props before other damage) or any of that. And, I don't see you would notice much difference in fuel consumption. Nor, are you racing and don't really need to shave a .1 or .2% advantage between first and back in the fleet. So I would pick the boat that you think best serves your needs and you like best... the one that gives you that satisfied feeling and forget what it is made out of.
  10. Lenny

    Lenny Member

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    Just happen to see this old post so I thought I would reply. I am the owner of "Grand Cru" a 80' all aluminum Jongert Motor Yacht. I have owned the boat for six years. I had the boat for sale several times when we were looking for a larger vessel. Had firm offers but could not find another boat to suit our needs.
    As my naval architect, from Murray and Associates says, when I have him look at a possible newer boat: "Grand Cru" is a ship, not a yacht. Impossible to build anything like her today for any reasonable cost. He will always talk me out of a newer used boat. Yes you must pour money into refits but you have a battleship. (Grand Cru has crossed the Atlantic 7 times on her own bottom)
    I have been on "Impossible Dreams" multiple times now called "Halcyon Days". I am an engineer by education.
    We have traveled extensively with our boat. Per the hour meter on the injection pump, which was rebuilt when we bought the boat, about 2200 hours or about 20,000 miles at 10.3 knots. We have been in seas 14 feet, going into them. Great ride, boat just slices thru no pounding. We were on bridge, wife reading a book, me drinking my tea. (plastic mug not a proper cup & saucer).
    Anyway we are now on our third MAJOR refit. Boat needed nothing but we are going to the Med for two seasons and wanted to get ahead of the curve. Boat on the hard. We survey the boat twice a year for our own information. Anyway NO issues with the aluminum hull. Inside or out.
    "Halcyon Days" has been for sale for quite some time. Owned by a charity. It is my understanding that the last possible buyer did a survey and there were problems with the steel, beside other issues. They did not buy the boat.
    This is NOT a fair comparison of aluminum vs steel, since the original owner of my boat was a super yachtsman and I have an open checkbook on the boat. "Halcyon Days" might not have had the same care but hard to tell.
    Bottom line, if I am in the middle of nowhere, and have an accident, with a hole in the hull, I could fix it myself if steel or find someone anyplace to fix it. Aluminum harder and doubt I could fix it myself and harder to find someone. Either way it might not look pretty but could be underway in a few days. Fiberglass impossible to fix yourself.
    Looking for a newer boat, have to buy steel hull / aluminum top, since very few all aluminum boats, too expensive to build today.
  11. Capt J

    Capt J Senior Member

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    Lenny, you could always fix aluminum enough, even if you had to 5200 an aluminum plate over it and a bunch of self tapping s/s screws for an emergency repair.

    But, generally people donate a boat because they cannot sell it and usually that is because it has been let go and unmaintained for so long. So generally donated boats 9 out of 10 times, need EVERYTHING.
  12. Danvilletim

    Danvilletim Member

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    I was aboard Halcyon Days. I called the previous broker before Bradford and he told me run not walk.

    I think there might be some corridor in the integrated tanks. If someone is up for a project you would have a timeless boat.
  13. Lenny

    Lenny Member

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    Thanks Capt J. I have no experience fixing aluminum. I saw another boat in the yard with an aluminum hull being fixed.Took them forever. Saw a steel boat being fixed and it went much faster. Will do my homework on fixing aluminum.

    As to "Halcyon Days" formerly "Impossible Dream" I have to agree. From my review of the information that the possible buyer sent to me, after the survey, the boat is very tired. It will take a buyer with deep pockets. That being said, they will have a special boat. Problem is the the market for real trawler boats, that can cross the ocean, or cruise in difficult situations, is VERY limited. People say they want to cross or cruise, but when they hear 9 to 10 knots they pass. Want a "White Boat" that can go 20 Knots. Some really good trawlers sit on the market for years.

    Buy their 20 Knot boat and go to the Bahamas.
    #1 4 foot in the gulf stream will not cross. No kidding. Had an 80 foot fast boat next to us in the marina. We were crossing and he would not go. Good captain said he had to slow to 8 knots in anything over 3 foot and boat would pound like anything. Afraid it would break something. Over 5 million dollar boat.
    #2 Get to the Bahamas and anchor. Realize they do not have enough food for more than a few days. Anchor will not hold if it gets rough. Zero speeds - good luck. Have you ever seen Zero speeds on this kind of boat?

    People want marina boats. OK with me and the dealers love it.
    We left Florida, went to Washington DC, cruised to Maine, and back. 4 months. Filled the tanks with 5,000 gallons. Almost made it round trip without fuel.
    Have friends with a 100 ft Hargrave. Use that much fuel to get to Newport and have to stop multiple times for fuel. Don't get there any faster since we leave Florida and go nonstop at 10 knots.
  14. Capt J

    Capt J Senior Member

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    Well. To fix it properly you'd have to cut a piece out and weld a piece in and just need a good welder who is knowledgable in welding aluminum that's all.
  15. JWY

    JWY Senior Member

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    I was the broker who had the buyer under contract on Impossible Dream, now Halcyon Days. I recommended aborting the survey after the third day. Beautiful yacht but requires a buyer with deep pockets and perseverance to restore her to her former glory. With even deeper pockets, she could be upgraded to the level of Grand Cru.

    Judy

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