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Thread: Designing a new CONCRETE BOAT

  1. #36
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    Default Re: Designing a new CONCRETE BOAT

    hey guys i almost finish the canoe you want to see it? it will weight around 300-400kgs by the way just one question if i add a 20hp engine will it brake or the engine wont be able to move it?IMG_1830.jpgIMG_1832.jpgIMG_1840.jpg

  2. #37
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    Default Re: Designing a new CONCRETE BOAT

    well i felt discouraged but i gave everything i had and yes im an engineer student! and you can check out the work already is on my last post!

  3. #38
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    Default Re: Designing a new CONCRETE BOAT

    sir ! how are you doing tell me how you like the canoe! ?
    Quote Originally Posted by Ian McColgin View Post
    " . . . a heavy concrete hull." [#27] Maybe not. These are engineering students who can surely research the modern approaches to foam and such in the aggregate. Just because it's concrete does not mean it's a rock.

  4. #39
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    Default Re: Designing a new CONCRETE BOAT

    The pix are too dark for me to make out.

    At 300kg to 400kg, maybe it is a rock. But many of my sailboats and my work on tugs involved moving stuff with about one HP per ton so properly mounted and with a suitable propeller you should be able to move reasonably at something a bit below "hull speed".

    Hull speed is the speed where the boat's moving fast enough that it has a bow wave and a stern wave separated from the stern. So the boat essentially squats in the trough between her two waves and is trying to move uphill. Unlike the sound barrier, there's nothing fixed about "hull speed". It's just a range where to go faster takes disproportionatly more power. As a rough rule, "hull speed" in knots is about one and one third the square root of the waterline length in feet. That 1.333 constant is not a constant. A very narrow hull might be better represented by using 1.5 or even more while a really fat tub might be barely at 1.0.

    Marmalade, my 25' (12.5' beam) catboat does 4.5 knots on flat water at 2000 rpm. At 3500 rpm, she'll get up to 5.1 knots but is pushing a lot of water backwards and the extra speed is rarely worth it to me.

    If your canoe is "canoe shape" with the flat bilges and U sections, double ended and a bit bulbous amidships, she should move quite nicely and easily at about 1/2 "hull speed". The design evolved, after all, with the energy a person can put in the water. With power, canoes can go faster but tend to squat in a suddenly large trough. Since I can't see the pix you posted, I can't really guess at what yours will do.

    As to will the motor break the boat. Sure, if the build and installation are faulty. But there's no inherent reason for her to break.

    Maybe along with clearer pictures you could let us know what the schedule of any ReBar and mesh you arranged before plastering on the mud.

    G'luck

  5. #40
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    Default Re: Designing a new CONCRETE BOAT

    let me take more clear pictures because that was on night time!

  6. #41
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    Default Re: Designing a new CONCRETE BOAT

    It will sink.
    There will be no way to recover that thing.

    What is it for? Engineering assignment? How many students? Which university?

  7. #42
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    Default Re: Designing a new CONCRETE BOAT

    Come on. Lets let him try before you say it will sink.
    At that weight we really ought to know the dimensions to see if it will sink.

  8. #43
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by heavyweather View Post
    It will sink.
    There will be no way to recover that thing.

    What is it for? Engineering assignment? How many students? Which university?
    race , mechanics of deformable bodies and mechanics of fluids , 2 only can paddle

  9. #44
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    Default Re: Designing a new CONCRETE BOAT

    3.50m long 88 cm wide at the middle and 60 cm between middle and tip of the canoe
    Quote Originally Posted by upchurchmr View Post
    Come on. Lets let him try before you say it will sink.
    At that weight we really ought to know the dimensions to see if it will sink.

  10. #45
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    Default Re: Designing a new CONCRETE BOAT

    by the way it wont sink theoretically because buoyancy is 650kg +
    and im in the 300-400 kg range

  11. #46
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    Default Re: Designing a new CONCRETE BOAT

    It's short. Not really wide. Looks high.
    Have you calculated the vertical weight distribution?
    Done a light prototype of the hull?
    350cmX89cm with much weight high up sounds just a little tippy.
    I figured that displacement would be enough but that doesn't help when it rolls the moment it starts floating.

    What calculations and trials have you done before?

  12. #47
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by johnw View Post
    Absolutely! Concrete canoe is an extra-curricular portion of a civil engineering education. Not a place for analysis paralysis, but one for getting the job done. And it looks like german... and his crew did just that!

    Not sure this is the right spot for detailed discussion, but since it is a part of my past I've got to chip in.

    We always took two to competition. Whatever we had concocted that year and a Destroyer from years past. New paint and was good as new.

    Strategy was to race hard with the new one...varied success. Then challenged all to a demolition derby afterward and brought out the Destroyer. Also the newest rig so we wouldn't seem aloof.

    We left a lot of concrete on the bottom of the lake, but the destroyer still lives! (I think).

    But no matter what, a great experience! We came back with an understanding of deadlines and reality, budget and finding sponsors. And for german... to take the initiative to engage boat builders and share his experience with us, Kudos!!! Keep it up!
    Last edited by FishoutaFlorida; 10-01-2017 at 09:08 PM. Reason: needed to punch up finale
    Please don't dominate the rap Jack, if you've got nothing new to say.

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  13. #48
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    Default Re: Designing a new CONCRETE BOAT

    THANK YOU SO MUCH FOR SUCH ENCOURAGING COMMENT! its really what i needed i was already scared my stuff will sink but according to the math this boat wont sink however it may spin like crazy i dont know !
    Quote Originally Posted by FishoutaFlorida View Post
    Absolutely! Concrete canoe is an extra-curricular portion of a civil engineering education. Not a place for analysis paralysis, but one for getting the job done. And it looks like german... and his crew did just that!

    Not sure this is the right spot for detailed discussion, but since it is a part of my past I've got to chip in.

    We always took two to competition. Whatever we had concocted that year and a Destroyer from years past. New paint and was good as new.

    Strategy was to race hard with the new one...varied success. Then challenged all to a demolition derby afterward and brought out the Destroyer. Also the newest rig so we wouldn't seem aloof.

    We left a lot of concrete on the bottom of the lake, but the destroyer still lives! (I think).

    But no matter what, a great experience! We came back with an understanding of deadlines and reality, budget and finding sponsors. And for german... to take the initiative to engage boat builders and share his experience with us, Kudos!!! Keep it up!

  14. #49
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    Default Re: Designing a new CONCRETE BOAT

    no prototypes or anything like that , by the way i just saw a brazilian team with a 500kg canoe floating and that thing was smaller than mine and it looked super heavy and mine doesnt even look half that heavy so i dont even think my canoe is even +300 kg and the shape is well defined today i will upload more photos of it!
    Quote Originally Posted by heavyweather View Post
    It's short. Not really wide. Looks high.
    Have you calculated the vertical weight distribution?
    Done a light prototype of the hull?
    350cmX89cm with much weight high up sounds just a little tippy.
    I figured that displacement would be enough but that doesn't help when it rolls the moment it starts floating.

    What calculations and trials have you done before?

  15. #50
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    Default Re: Designing a new CONCRETE BOAT

    Well, it looks like a bomb in those pictures, but that's mainly down to the color. Perhaps you could name it UXB, to intimidate the competition.

  16. #51
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by germanhiguerav View Post
    by the way it wont sink theoretically because buoyancy is 650kg +
    and im in the 300-400 kg range
    It will float in calm water with a 200 kg load and 2cm of freeboard. As long as the load is very careful not to rock the boat and there is no wind and no waves, it may stay afloat. I have two canoes, a 3.25m long, 71cm wide cedar lapstreak and a 3.5m x 71cm tortured plywood that weigh less than 15kg. With my 90kg mass, they ship water over the bow in a 15cm chop if I head at any angle to the waves. someone under 70kg has no problem. Another similar canoe that is 3.8m long does not ship water under similar conditions.

    Do the rules allow the use of surface bonding cement? It might save a lot of weight. It contains alkali resistant glass fibers and seems to have reasonable tensile strength, but I can't find that information. It is probably too late to look at Spider Lath, but if I had the time, I would hit them up for a free sample. I have spent at least 15 minutes researching this, so my advice may not be as good as your experience.

    I read about a company in Maine [probably in National Fisherman in the late '70s] that intended to build ferrocement boats commercially. They started with a study to determine the optimum ratio of cement to steel. In every category, strength, cost, whatever, the optimum ratio was 100% steel, 0% cement. They decided to build steel boats...

    EDIT There is something called ultra high performance concrete. I found one source, Ductal
    http://www.ductal.com/en/engineering/why-use-ductal
    Last edited by MN Dave; 10-04-2017 at 12:38 PM.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

  17. #52
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    Default Re: Designing a new CONCRETE BOAT

    heres the new picture we just need to make a little reinforcement of concrete in the inside a thin layer only and thats it folks! i will record a video later and upload it !IMG_1987.jpg

  18. #53
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    Default Re: Designing a new CONCRETE BOAT

    Wow, very nice! Is that a Mini Clubman behind this Trough?

  19. #54
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    Default Re: Designing a new CONCRETE BOAT

    IMG_2081.jpgIMG_2102.jpgIMG_2083.jpg
    Guys heres the new update of the canoe today i will finish the painting job its almost finish what do you think!

  20. #55
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    Default Re: Designing a new CONCRETE BOAT

    Are you going to smooth out the gunwale? Might hurt getting in.

  21. #56
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    Default Re: Designing a new CONCRETE BOAT

    Of course sir!
    Quote Originally Posted by upchurchmr View Post
    Are you going to smooth out the gunwale? Might hurt getting in.

  22. #57
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    Default Re: Designing a new CONCRETE BOAT

    https://youtu.be/IvjQb1LwcG0 THERES A VIDEO OF MY TEAM FLIPPING THE CANOE

  23. #58
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    Default Re: Designing a new CONCRETE BOAT

    ...and here is a video of a competition.

    Please don't dominate the rap Jack, if you've got nothing new to say.

    Robert Hunter

  24. #59
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    Default Re: Designing a new CONCRETE BOAT

    Concrete cargo ships were built and used during WWI. They were not economical, too much weight for given payload. After WWI many of them were scuttled as breakwaters.

  25. #60
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    Default Re: Designing a new CONCRETE BOAT

    This is a canoe by a group of college students.

    Why are we talking about full sized ships?

    Why don't we let these guys be the show, since it is their thread?

  26. #61
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    Default Re: Designing a new CONCRETE BOAT

    Guys we won the contest i will upload video soon!
    Quote Originally Posted by upchurchmr View Post
    this is a canoe by a group of college students.

    Why are we talking about full sized ships?

    Why don't we let these guys be the show, since it is their thread?

  27. #62
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    Default Re: Designing a new CONCRETE BOAT

    Congratulations.

  28. #63
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    Default Re: Designing a new CONCRETE BOAT

    Way to go. Congrats.
    -Dave

  29. #64
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    Default Re: Designing a new CONCRETE BOAT

    Lyle Hess, The designer of the Bristol Channel Cutters and the Pardy's first boat, "Seraffyn" and their second boat "Taleisin". Had another profession prior to becoming a full time yacht designer. Lyle was a swimming pool contractor! One day I asked him about the viability of concrete as a boat building material.
    His answer was, "You have two components that are excellent conductors of electricity, wire mesh and concrete, joined together in an electrolyte, salt water.
    If the wire is replaced by a non-conductive material, the boat will last longer." But, he went on to mention that cement does not have a long life expectancy when used for larger craft, especially sail boats. This is because boats of sizes larger than row boats are subjected to flexing moments and concrete does not flex well.
    I personally have seen many ferro cement boats that ended up being unsafe due to cracking of their hulls. One boat was at anchor in San Diego bay and was struck by a tug that was conned by a drunken skipper. The boat shattered, from stern to bow, like a safety glass windshield. This was sad because the owner had just launched the boat after nearly ten years of building it!
    One of the most beautiful boats, built of ferro cement, I have ever seen was a twenty three foot yawl. That was a boat that one would never guess to be concrete as it was so fair and well designed. The owner towed it from Newport Beach up to San Francisco on a trailer that was built for it with the intention of cruising the Bay. By the time he and the boat arrived, the hull had cracked so badly that it was taken to the dump and buried.

    I honestly believe that attempting to build a large boat of ferro cement is an iffy thing to do. Small boats are ok but a big one can and will most likely prove to be a bad idea. There are other materials out there that are proven to be less problematic!
    Jay
    Last edited by Jay Greer; 10-13-2017 at 04:38 PM.

  30. #65
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by Jay Greer View Post
    Lyle Hess, The designer of the Bristol Channel Cutters and the Pardy's first boat, "Seraffyn" and their second boat "Taleisin". Had another profession prior to becoming a full time yacht designer. Lyle was a swimming pool contractor! One day I asked him about the viability of concrete as a boat building material.
    His answer was, "You have two components that are excellent conductors of electricity, wire mesh and concrete, joined together in an electrolyte, salt water.
    If the wire is replaced by a non-conductive material, the boat will last longer." But, he went on to mention that cement does not have a long life expectancy when used for larger craft, especially sail boats. This is because boats of sizes larger than row boats are subjected to flexing moments and concrete does not flex well.
    I personally have seen many ferro cement boats that ended up being unsafe due to cracking of their hulls. One boat was at anchor in San Diego bay and was struck by a tug that was conned by a drunken skipper. The boat shattered, from stern to bow, like a safety glass windshield. This was sad because the owner had just launched the boat after nearly ten years of building it!
    One of the most beautiful boats, built of ferro cement, I have ever seen was a twenty three foot yawl. That was a boat that one would never guess to be concrete as it was so fair and well designed. The owner towed it from Newport Beach up to San Francisco on a trailer that was built for it with the intention of cruising the Bay. By the time he and the boat arrived, the hull had cracked so badly that it was taken to the dump and buried.

    I honestly believe that attempting to build a large boat of ferro cement is an iffy thing to do. Small boats are ok but a big one can and will most likely prove to be a bad idea. There are other materials out there that are proven to be less problematic!
    Jay
    Because of these things, it is nearly impossible to insure an old ferrocement boat.

  31. #66
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by germanhiguerav View Post
    Guys we won the contest i will upload video soon!
    Great news!

  32. #67
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    Default Re: Designing a new CONCRETE BOAT

    I just watched the video. Glad to see that a fine time was had by all!
    Jay

  33. #68
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    Default Re: Designing a new CONCRETE BOAT

    Concrete boats have a long history though.
    There was a concrete boat shown at the world fair 1855 in Paris already.
    The Netherlands had a history of using them in canals and they were quite popular in Germany two centuries ago in times when there was a shortage of steel, saving 70%.

    Doesn't make sense for one off hulls though and all these boats were used on inland waterways (Danube). They cast them in forms.
    There are still lots of old, good preserved concrete boats in Germany, a concrete tanker built in 1919 is stranded in California.

    15m ferrocemet ship Kranich VII (2002)
    http://wordpress.ferrocement-ships.c...02/Kranich.jpg

  34. #69
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    Default Re: Designing a new CONCRETE BOAT

    I once heard that there is a cement skiff in the hippo pond at the Berlin Zoo. It is purported to be the world's oldest boat of its kind.
    Jay

  35. #70
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    Default Re: Designing a new CONCRETE BOAT

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    The advice contained in this thread is - at best - worth all of what you paid for it - no sane man, other than a historical re-enactor, is going to use a mechanical planimeter - that sort of stuff is much faster and simpler with free software such as "Freeship"....
    "That sort of stuff" it's called naval architecture. By extension you are treating people like me insane, well thank you for that.
    What a foolish and ignorant thing to say.
    As a naval architect I use planimeter and mechanical integrator for 50 years, and I didn't find the need for yacht design software. The software can be practical for the accommodation, systems and other variant's, since it is simpler to make changes with a computer then starting all over by hand. That said, I continue to design by hand, ink on Vellum or Mylar all my plans. And designing by hand, I can really choose my shapes, and control what I want.

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