Maximum trailerable towing width

Discussion in 'Multihulls' started by Saylaman, Feb 7, 2010.

  1. trev0006
    Joined: Apr 2010
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    trev0006 New Member

    That is one awesome boat.





     
  2. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    You could always do it this way

    Forty 35ft catamarans, 20ft wide went past these houses (this one was mine)

    Richard Woods

    Woods Designs

    www.sailingcatamarans.com
     

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  3. Wake31
    Joined: Jan 2011
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    Wake31 Junior Member

    Saylaman,

    I am about to pull my 45' ferro up and fix a large hole in her port side. I read a relpy you made in another thread and thought I'd ask you advise. What cement mix is best to use? Some say portland III, some say portland V, some say expandable grout, some say fast dry quickcrete? What should I use? I plan to cover over the new patch of mortar with epoxy and cloth but I still don't know what cement mix to use. Can you help?

    Thanks
    Damon, Val and the Someday Lady
     
  4. Saylaman
    Joined: Dec 2007
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    Saylaman Junior Member

    Hi Wake 31
    For use in marine applications generally cement with better sulfate resistance is recommended, but that is when mortar or concrete is directly exposed to the sea water and spray. You want to protect the repair with epoxy, the epoxy will protect the mortar from sulfate. Around the world different discriptions are given for cement and I don't remember what type III and V are. I can advise though that if you're covering the repair with epoxy you won't get much water ingress, if any, into the mortar and it won't really matter whether the mortar is sulfate resistant, since sulfate in the sea water will not get to the mortar. Even if some does get to the mortar, it will be very little and won't be worth worrying about.
    I think the more important aspect is how quickly the repair gains strength. I'd use what is commonly referred to as Ordinary Portland Cement, or General Purpose Cement, or CEM I 42.5 (All names in different countries for the same cement, basically just ground cement clinker with a little gypsum to control set time). Or the finer ground version of this cement, High-Early strength cement or Rapid Hardening cement. They both set in about the same time, but the rapid hardening gains strength faster.

    At temperatures of around 24 degrees Celcius, Ordinary Portland Cement will give you about 50 to 60% of it's strength in three days, 70 to 80 % in a week and 100% in a month (if you keep it nice and damp the whole time). As you can see, even after a week you've got enough strengh for the patch to be functional.

    Rapid Hardening Cement will give you approximately 70% strength in three days and about 80 to 90% in a week (again, if you keep it nice and damp the whole time)

    The sulfate resisting type cements will generally only give about 30% strength in three days and about 50% in 7 days and I don't think you'll have any real advantage using these since the epoxy will protect whatever mortar you use. If I think back to my study days, 20 years ago....I think the Type V cement may have been the sulfate resisting.....but I stand corrected.

    Just a warning not to use chloride to accelerate setting time in the portland cement mortar. In past years, and still in some modern applications, chloride was used to accelerate setting time, but it does supply chloride to reinforcing steel and the risk of early corrosion is very high. It's not worth the risk in ferro-cement applications.
    If you want faster strength gain, you can warm the repair once it has set, but don't heat it above about 65 degrees Celcius. Steam is used in precast applications to heat concrete to about 65 degrees and it can achieve 80% of its strength in 24 hours.

    I'm a concrete technologist and know less about epoxy, so my advice is based on ferro-cement type repairs. There may be epoxy based repairs for ferro cement applications that will cure in hours and offer you better results, but you'll have to ask the epoxy guys for advice. The epoxy type mortars will be quite expensive, but then the patch isn't very big and it may pay off in less down time?

    If you go with a portland-cement type repair, make sure you get rid of all the rust on the reinforcement and treat the reinforcement with something that will passify the corrosion.

    After all that discussion....if it was mine, I'd use Rapid Hardening Portland cement, a water:cement ratio of about 0.35, and then cover it with plastic, sealing the plastic well to keep the moisture in. Leave the plastic on for as long as is practical, three days to a week would be good. In colder climates you could insulate the repair, the warmer it is, the quicker it gains strength and if you need a very quick repair use some sort of heat over night, but don't let it dry out during curing.

    All the best with your repair.
     
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  5. Wake31
    Joined: Jan 2011
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    Wake31 Junior Member

    Saylaman,

    Thank you so much for the reply! You have answered all my question and I maybe in contact over the next month with a few more. Depending on what I find once its out of the water. The tear is about 1' by 2' and it was caused by her being pushed ashore during a big storm. The boat laid down on a nice beach with 1 rock on it. Wouldn't you know, right on the rock. The pressure of her weight pushed the rock through the hull. It was patched in place by the last owner with layers of concrete, vinyl and plywood, all bolted together. My wife and I have taken her over and plan to pull her up on the weighs in a couple weeks. Also as the boat was tugged off the beach at the next high tide the rudder swung around and hit that same rock, damaging its housing. So we have a lot of work once its out. Hopefully we will be able to repair her in the week we have. It has always been our dream to live aboard and if all goes well, with a lot of work we will live our dream by June.

    A quick question! I have read also that you should not feather the patch past the damaged area. Is this correct? Or does it matter when you plan to cover it with epoxy and cloth. Some say that the thin area will crack and brake away.

    Thanks again
    Wake31 and the Someday Lady
     
  6. gonzo
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    gonzo Senior Member

    Tilt the Moth and it will fit the 2.1 rule
     
  7. Saylaman
    Joined: Dec 2007
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    Saylaman Junior Member

    Wake 31
    I guess that is 'Murphy's law' at its finest, if anything can go wrong it will.....one rock on the beach and you'll hit it twice!

    Yes, you're right about the feathered edge. Portland cement mortar has very little flexural strength and in thin applications will break away very easily. The mortar relies on the steel rods and chicken wire for all its flexural strength. It would be better to fill these thinner areas with thickened epoxy.

    All the best with the repairs and the future plans, I wish it was me!
     
  8. Wake31
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    Wake31 Junior Member

    Saylaman,

    One more quick question. I read that ferro cement boat use straight cement. This mean straight cement and water, no sand. Right out of the bag? Is this true? Would do you suggest?

    Thanks
    Wake31
     
  9. Wake31
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    Wake31 Junior Member

    Sorry I meant "what do you suggest" not would!
     
  10. Wake31
    Joined: Jan 2011
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    Wake31 Junior Member

    Saylaman,

    I have just gone through some mix procedures and ratios and have one more question. Does the ratio of .35 water pertain to just cement or to the cement sand mix. They say to mix my cement to sand ratio at 0.4 to 0.6 and water at .35 So do I mix up my cement and sand and then apply the .35 water ratio or do I mix the water / cement ratio then add the 0.4 -0.6 sand?
    I'm so sorry to bother you with this, but I want to do it right!

    Thanks again
    Wake31
     
  11. robherc
    Joined: Dec 2008
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    robherc Designer/Hobbyist

    hmm, when it comes to building boats, I'm more a a wood+GRP or foam/honeycomb+GRP guy, but in another lifetime I did a LARGE amount of cement and masonary work. If the same principles apply to your ship as to your home's foundation, then using Portland Type I/II cement at a ratio of 1 cement to 2-2.25 sand works well, and you just add enough water to allow it to be mixed thoroughly and formed. The reasoning is that the thinner the consistency of the slurry (i.e. the more water you use), the greater the likelihood of evaporating water causing a shrinkage crack in your finished casting, or a water "pocket" causing a cavity...both are, of course, terribly detrimental to either a home's foundation, or, I'm sure, a boat. My advice as a veteran home builder would be to experiment a little with the water to cement+sand mixture ratio to find what works best in your area; air temperature, humidity, and air pressure all figure in a bit, so build a couple inexpensive plywood molds, mix your cement with differing amounts of water, fill the molds, then allow them to set for a week or two. After all of the formed chunks have set, remove the molds and do your darndest to destroy them; the one that's hardest to destroy is probably your best mixture to use for your patch. :)


    -Hope this helps,
    Robherc
    (gee, if legendary status can be acquired by absence, then I think I MUST be a legend about here by now....sorry for the prolonged hiatus guys!)
     
  12. Saylaman
    Joined: Dec 2007
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    Saylaman Junior Member

    Wake31
    Sorry for the long delay, I've been busy with all sorts. Ferro cement is always a blend of cement, water and sand. The water to cement ratio is around 0.35, you mix for example, 1 kg of cement powder to 0.35 kg of water (or one pound of cement to 0.35 pounds of water) Mix this together then add sand until the mix is about the right consistence to render. As someone else has pointed out, don't make it too sloppy, otherwise when the water evaporates too much volume is lost and it shrinks too much.
    Some cements take more water than others, if when you've mixed 1 part cement with 0.35 parts water, it is too stiff already, even without adding sand, then you'll need more water, but only add as much as is absolutely necessary. As was pointed out, about two parts sand to 1 part cement is about right, so if you add your two parts sand to the mix, then add more water until it is the right consistence to render.
    Sand also affects the water requirement, a sand that is too fine with lots of dust and clay is not good, it will take too much water, weaken the mix and result in cracking. Sand with particles varying from about 3 mm (1/8'') down to dust, but with very little dust is best to use. If the sand is too dusty you could wash it, since you're only making quite a small batch. Put the sand in a drum, fill the drum with water, stir the sand around a bit, lots of the dust will become suspended in the water, pour the water off and the remaining sand will be cleaner and more suitable to use.
    If you've got a nice clean sand you should safely be able to mix 1 part cement, 2 parts sand and about 0.35 to 0.4 parts water (all by mass) and the mix will be good. Make sure you prevent moisture loss from the patch when you've finished the repair, portland cement needs to remain moist to gain strength.

    All the best.
     
  13. Wake31
    Joined: Jan 2011
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    Wake31 Junior Member

    Saylaman,

    Thanks for you advise! I think I've got my plan all worked out! Just can't wait for it to be pulled up. All this prep and planning is making me crazy. Just need to get my hands dirty and be done with it.

    Thanks again
    Wake31
     

  14. Wake31
    Joined: Jan 2011
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    Wake31 Junior Member

    Hey guys!!! Well I got the boat up on the weighs and fixed her!!! We plan on putting back up this fall to repair a few dings in the keel that I did not know about until she was up!! anyways if you want to check it out, here is our blog!!! http://somedaylady.wordpress.com/

    Wake31 and the Someday Lady!!!
     
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