Sailing a catamaran with only ONE rudder
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- Опубликовано: 18 сен 2024
- After losing one of our rudders 800nm from land, we need to make our way quickly to St Lucia. Balancing the boat to prevent wipeouts and skidding around the ocean is a priority. If we can keep the speed up the one remaining rudder can be quite effective, the challenge is to make sure we have the right combination of sails up to balance the boat.
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My problem with carbon fiber is that the epoxies have not kept up with the strength of carbon fiber. The weakness is the epoxie. I don't know how dynema compares with carbon fiber as a lay up material. I have found some interesting numbers with aluminum, and bomboo. Bamboo is a grass, and it grows to over 120 feet in five years if you cut it down it will be back to over 120 feet in five years. Aluminum strength is 30,000 psi ,but bamboo's strength 28,000 psi. So a cubic foot of aluminum rips at 4,300,000 ,and weighs 166pounds bamboo the same size rips at 4,023,000 ,and it only weighs 20 pounds. If you had enough bomboo to weigh 166pounds it would rip at 35,300,000 pounds. Bamboo is clear with no knots, and they make marine bamboo.
There are 2 elements to the composite matrix. The fibre and the resin. The fibre is the most important factor in the matrix as it is responsible for transferring all the load. The resin works by keeping those load bearing fibres in place. Yes, if the resin was stronger then there are internal stresses inside the matrix that would benefit. However it won't help make the overall part carry more tensile or compressive loads.
In terms of natural fibres there are quite a number on the market including flax, sisal, hemp and of course bamboo. They look very promising however at this stage there are still some big hurdles to overcome before they can be used on a more commercial scale. The biggest issues are price, availability and processability. The fibres are still very expensive and are not easy to source as there are not many companies producing this sort of product. The major hurdle is processability as they are natural fibres and you cannot control the variation in mechanical properties of these fibres. The flax industry is only just starting to get this under control to make it commercially viable. I (Shayne) used to run a composite R&D lab and have been watching this area of development for the last 20 years.
Great argument for a fourth reef. So the staysail keeps bow down if the asym curls under…. Great explanation.
Thanks. How's the boat hunt going?
@@youngbarnacles well, it’s a rollercoaster ride as usual. There’s a promising lead, but it’s a stretch for us, so we shall see
Good stuff. I'm a newbie to sailing. I really enjoy your sailing, carbon fiber, and trimming knowledge. Thanks, keep the vids coming. ;-)
Thanks 👍
When it comes to new or old materials some times I think the industry wants people to only consider their products. When the two Russian students made the first graphene, and won the Nobel prize for science this product is difficult to mass produce. Dynema is 9 times stronger than steel, but graphene is 300 times stronger than steel. Graphene capacitors are going to replace all batteries in the future. It is being used now on small batteries. No one is trying to use water as a refrigerant, and the chemical companies don't want us to try. A lithium bromide absorbtion system runs on water. Lithium bromide is the absorber, and water is the refrigerant. At - one bar water is 36degrees fahrenheit. With these properties we need more inventions.
Despite having rudder deficiencies with those daggerboards it looks to track pretty good.. considering.. 🙂👍
Yes. We were ok once we got the boat balanced. It was actually quite a fast sail with this set up
Great content. Do you have a follow up video on rudder post broken fix etc..?
Hopefully... we're busy building rudders at the moment
Great video including how to balance the sails on the boat (also needed without this incident). Out of interest since you have the daggerboards down they become the point of pivot. If the daggerboards where all up would the rudders then be the pivot point?
You are absolutely correct that balance is critical whether there is one rudder or two. When the dagger boards are up the pivot point moves the CLR (centre of lateral resistance) focus to the centre of the projected hull. This is quite dynamic and will move around a lot when sailing in waves. Yes the rudders do become a lot more loaded but they are not the pivot point. Having the dagger boards down concentrates the CLR around the dagger boards.
Can you explain how you get the underwater shots while sailing, I have been unable to get the GoPro to held underwater while sailing fast
We have a gopro8. Just stuck iit n the water and held on tight!! 😁😁
You have at least found a solution to weed getting caught on the rudders. Well it is 50% effective. :)
Yes we have...and it's less drag too 👍🤪
only the leeward rudder steers, the windward rudder is just drag, (on a cat) sailed hobbie cats for years and would pull up the winward rudder....
Yes this is true for smaller off the beach catamarans. We used to race beach cats mainly Nacras, A classes, Taipans etc and loved them. The larger cats are a bit of a different beastie. They do require both rudders to effectively steer the vessel.
Totally under control, are you going to replace both rudder stocks with expensive black stuff ?
That's the plan 👍
Wow! Making carbon rudder stocks is quite a job...
Yes but Shayne is skilled in the dark arts so it's something we can do. The problem is we don't have a vacuum pump on board for the consolidation (since we are sailing around the Caribbean) So in this case we'll probably outsource the job to C-tech
Would towing a small drogue with its warps on winches on both sides so you can adjust the angle of drag help lower the rudder movement ?
In our situation we still had the remaining rudder and were able to balance the boat with our sails so steering was not a big issue. If we had no rudders at all, then we would look at using our drogue.
Is the black sail, the staysail, a hank-on or roller reef or some other arrangement? Thanks.
Staysail is on a cable which we attach to mast with halyard lock.
Would it have made any difference if you had lost your windward rudder instead?
Yes it definitely would have made things easier if we had lost the windward rudder. In flat water no difference in the feel or control. In waves though a very different story, especially if sailing on an aft quarter sea. If the rudder is on the windward side and you go over the wave, and the wave tries to rotate the boat a little, the rudder is first of all loaded as it wants to turn the boat back down the wave, the second and most important is that corner of the boat starts to lift slightly. When the hull lifts slightly the end plate effect on the rudder is no longer there and it sucks air straight down and cavitates.