Cross Indian ocean in 4 meters dinghy sailboat

I don't know. For a rough idea, look for something similar and read the statistics on the design. For a more accurate idea, you'll need to crunch numbers (using rules that go beyond my knowledge, not least because I've never designed anything with a keel), but there are too many unknowns about your design at the moment to start calculating. For example, what's your keel for? Do you still want to have outriggers too? How much weight do you want in an unnecessary keel if the outriggers are keeping the boat upright? If the heavy keel is there to right the boat after a capsize, how's it going to do that if you have outriggers? By ballast, are you thinking of ballast in the hull to do some of the work of the keel (less efficiently and weighing the boat down more, although it can keep a monohull upright if the keel falls off), or is all this ballast in the keel? How much maximum power do you expect to generate from the sails and how far over do you want the boat to lean when generating that maximum power? (This varies - when the sail's reefed, the leverage is lower, so you can sail more upright with the same power.) Where have you got to now with your overall design?

 

I can see that this spiral hasn't gotten far from the first page, but I have the perfect name for the boat......."Deathwish"

 

May I ask how much time you have spent sailing a boat with that configuration?

Have you calculated the loads? Have you worked out the sliding mechanism? Have you spent any time hiking off something like that?

 

By using the exact same logic, you could say "if a glass bottle can survive for decades buried 20m down in a rubbish tip, then I can do it".

There is simply no logical connection between a glass bottle and a human in a sailing craft. The fact that you believe there is just shows that you're going to endanger yourself before you even get into the ocean.

Why not respect boat designers enough to learn from them? What you are doing is effectively claiming that you are sooooo much more brilliant than all the yacht designers put together that you can work out something they cannot.

You don't even know how little you know. Why not respect the many years that other people have put in to the science of boat design, and learn from it?

 

The forum member Chinaseapirate had many ‘‘fantastic’’ posts, but now has left our conversation parlours forever, and as such is registered as a Previous Member on his forum posts, it could be he was kicked out of here for insulting the ones who disagreed with him.

 

Actually just about all great designers effectively say you are completely wrong about your approach to design. Like other great inventors, including Einstein and the Wright Brothers, great sailboat designers learn by RESEARCH. They learn by reading all the available information on their subject. They learn by sailing. They learn by looking at other boat designs from a viewpoint of respect, and seeing where they work and where they don't work so well. The advances are very often made by learning about new materials and by taking an idea from one part of sailing and refining it or using it in another area.

What good designers never seem to do is decide that they don't need to spend years learning how to sail, sailing on a variety of different craft, and reading and discussing all they can about design.

So a good designer, for example, would look at your little floats and know that such floats were largely abandoned about 50 years ago, and why. A good designer would know about the problems of combining a trimaran with a keel, and what it could do to the re-righting problem and to the inverted waterline.

A bad designer is one who has not respected the sea and experts enough to know how little they know.

 

Aah, thanks, I should have checked the age of the thread and posts first.

 

Regarding respecting boat designers etc. we have far cross this topic. There is no subject of competition and so on. Again, i never claimed that i am so much more brilliant, but because you mention, all the yacht boat designers 15 years ago they were making so thick fiberglass boats without can understand the strength of materials (it took only one to change this and the rest to follow, and in modern day this happened only because of the profit, less material more profit). Yet you said "You don't even know how little you know.", which i never said that i know everything, yet information and what each person knows is very relevant. However if i knew everything i will definitely not be here asking. But you that you know everything, yet didn't contribute in anything at least at this topic as far as i can read, maybe you contribute on mention the dangers as other did too, but did not contribute in the building of the topic. Keep also in mind that all far you know is from others, either books or other people, which is exactly the same. Today we using the technologies to build faster better and to know more. That's the point of a forum, that's the point of technologies.

Now for your logic, we have to respect all boat designers, just because. Either they know or not. We respect all the good people, we don't have to respect someone just because. Of course i know what do you mean, but just with this for you that you haven't understand something you comment, here it is. You said "By using the exact same logic, you could say "if a glass bottle can survive for decades buried 20m down in a rubbish tip, then I can do it"." Now probably you can understand what you said, according to your logic and the previous example. In short what you said has no connection with the topic and with what we were talking. You probably should read the replies.

Thank you for your thoughts and despite my answer i understand what you mean to say. However we wasting our time with such replies. You can read the topic from beginning to end, and if you think there is something you can and want to contribute will be very appreciated. But read before you speak, i do not need to reply to the same and same pointless things again and again. You can find answers in the previous replies and you can contribute if you like.

 

@David Cooper here is my finalizing approach. The boat gonna be about 6.5m long and 2m wide in it's "beam" point. It will be made on plywood bulkheads and frames reinforced with wood. It will be multichine, 4 on the bottom and 2 in in the sided. In the upper hull of the boat i will attach core foam, while below i ll make water tanks as ballast, and also if i need to heel the boat for a repair lets say. I am thinking of longer outriggers, that can be screw in and out and be moved or removed. These outriggers can provide stability in calm waters, while can be closed in in choppy waters. The keel with be a lifting keel with a bulb made by aluminum, the bulb can contain leads and the keel water. That way i could pump the water out, leads too and i can lift the keel. This will be very useful on visiting reefs or if you want to bring the boat out. Yet the main purpose of this boat will be a crossing, the visiting can happen later. The keel will be used for stability, self-righting mechanism, and especially to balance the wait of the mast which i consider important as i don't know much about. I think of an autopilot for the rudder, free of electricity, it will be powered by the wind, so it needs wind. In additional i can make this fully electronic by using only 0,1% of that of an electric autopilot. But this is something to think in the future and not now. Now what im thinking it is mainly 2 things. First the pressure of the keel to the hull and how exactly i will blend the keel with the hull. It will be definitely separated from the interior, just if it breaks, then there will be backup the tanks on the bottom of the hull for ballast and the outriggers too. Second im thinking the mast and the sails. I got an idea how to do it but im still thinking of it. What bothers me most is the mast weight, how it gonna affect the boat. For a mast i am thinking 3mm aluminum, 10cm diameter (round mast). The mast and "boom" will be filled with core foam inside. Back to the outriggers, because they will be light, they could be used as spare masts or extra masts (something to think further). Regarding the shape of the boat, it will be look like, when see from top view, almost matches the Amel 55 lines, on the bottom it will be look like something like RM890. Weight full loaded im expecting to be 2t, but i ll prefer if it could be 1,4t. That's depends on the supplies. I have tried all the calculators and did the calculations myself too regarding ratios of sailboat etc. All ratios are in very good numbers, except the sail area as i given a small sail area. And the so called hull speed for displacement boats it could 6.2 knots. This is how far i have go.

 

I still don't understand your outriggers. Why do you need them for stability in calm waters if the keel/ballast will keep the boat upright and steady anyway? The only purpose I can see in having both outriggers and a heavy keel would be if the keel's weight is there solely for righting the boat, in which case being able to retract an outrigger could make sense of the design (and create a safer multihull than normal), while the keel need only be just heavy enough to right it without also having a significant role in countering the heeling forces from the sails.

You don't need much keel weight to balance a mast. If the outriggers are just decorations, you can get a reasonable idea of keel weight by looking at how much boats of similar size have - it will relate to their sail area and to how deep the centre of mass of the keel is (because a deeper bulb doesn't need to be so heavy as it has greater leverage), though the shape of the sails is relevant too if you aren't doing something standard - for a proper analysis you need to add up the forces for different areas of the sail at different heights as they all apply different amounts of leverage. If your outriggers are doing this work though and the keel only has to be able to outdo the weight of the mast plus sails when righting the boat, you just need to know the weight of the mast and the height of the centre of mass of the mast; then you can counter it with a bit more weight at the same height (depth) below the boat, or twice that weight at half the depth, or four times the weight at a quarter of the depth, etc. However, that would depend on retracting an outrigger to the point where it is fully out of the way so that the keel's weight can stand a reasonable chance of righting the boat, and I don't see how that's going to happen without detaching the outrigger completely (letting it float away on a long line, and reattaching it afterwards, but that won't be practical during a storm). You need to work out exactly what your plans are for this first to make sure your design is viable.

 

This is a long trip in a small vessel being sailed single handed. It might be nice to keep things simple (K.I.S.S.) so you can achieve your goal. ... or at least have a chance.

 

Here is the hull design i came with so far, the keel is only cosmetic as of now. I need serious information or any other help regarding the keel design, thickness and material and in relation with the mast and sails and how the boat is heeling in the wind. To make an overview, this is a sailing boat ply/fiberglass 6.5 meters long and 2 meters wide on its peak point. Also suggestions for the mast, im thinking 3mm thick aluminum with diameter of abut 10cm, 9 meters tall above the deck so 8 meters will be surface for the sail and 3 meters boom maybe?! The mast bar only, i believe it will weight about 25 kg. This is a small boat for a long offshore adventure.



@David Cooper thank you so much for all the info, i considering everything you said. About the outriggers and how im thinking of everything let me explain. I want a keel that i can lift, the keel will fill it with lead on the bottom and water on top, the keel will be screw it on the hull, if i want to lift the keel, im thinking that might i can pump the leads and water in another tank in the hull, keel will be then light to be lifted up and screw it in another "step" while the top part of the keel count also be unscrewed and removed as it will be aluminum or steel bars with foam and so it want be a problem for the mast and boom too. The keel will have no contact with the inside of the boat it will enters from the top of the hull and will goes down to the water. Once the keel is lifted up, then the outriggers can be deployed and screw them with some system further out (manually). Outriggers could be used also as an alternative mast just in case the mast been destroyed. This is the concept im thinking of, yet im really thinking all this in the relation with the mast as you mentioned in your previous comment. The mast could go down to the bed of the hull. I will place 3 steel or aluminum rings in the area at sides of keel and mast. so if mast or keel moves, then the whole rings moves which will be attached to the hull as frames (so i call it rings), i believe in that way it will be less stress to the ply/fiberglass hull. Definitely i don't say that what im thinking is right, or i believe it is right, but it is the concept and what im looking into.

@JSL i agree with you, and i will love if you like to give me any ideas or examples for "k.i.s.s."

 

That looks viable, so long as the transom doesn't go too deep - I don't know the rules for that, but I'd have thought it shouldn't go further down than the waterline.

Why do you want to lift the keel? It does no harm to leave it down unless you want to park the boat in shallow water, and any mechanism for raising and lowering it will add a lot of weight and make it more likely for the keel to break off in a storm. You'll also need lateral resistance, so raising the keel will lead to you needing to deploy another foil of roughly the same size and shape while the heavy keel is needlessly stored higher up. Just keep the keel down all the time. The only reasons I can think of for being able to adjust keel height are for taking the boat into shallow water, for easier transportation behind a car on a trailer, or for lowering the keel to a much greater depth than normal to amplify the righting force if you've capsized - this last reason would fit with a multihull idea where you have a relatively light keel which is just heavy enough to right the boat if it is extended to give its weight more leverage while an outrigger is retracted, although your hull is so wide that I can't see how you're going to be able to retract an outrigger far enough for that to work. You've designed a monohull which doesn't look well suited to work with outriggers.

As for the mast, you won't regret making it more robust rather than lighter, and you can either step it on the deck or run it right down to the bottom of the hull. Either way, you need to put reinforcement into the deck and hull to spread the load across a wider area, perhaps by having a bulkhead there with a doorway. Look at what other boats do and make sure yours has at least as much structure in the same places. Your priority for now though is to work out what you're doing with the outriggers, because they still don't make sense.

 

How are you going to "pump lead"?

 

@David Cooper Yes i want a lifting keel so i can go in shallow waters. Im going to design the "lifting" keel system and will re-think the idea, a fixed keel is much better as i have read online. However all the keels are attached only down bellow the hull with some bigger screws. Im only thinking that i can do the same but with a system that will be attached somewhere that i can take the screws out and re positioning the keel higher. The lifting keel wont be an option on the go, but it will take some screw unscrew work, raising the keel higher and feel it again with leads and water. Indeed will need much more weight for the surrounded walls and frames. I will design it first. But hopefully i can search more also technical details, for shapes, size etc. Regarding the outriggers, as far as im looking at it, outriggers seems more and more useless practically. The waterline is not in the straight line as it looks line. The point in the bow, the corner and the last point in the middle of the transom are on the same height and then they form a symmetrical curve down the hull, in the exact middle is the keel. I could add another section at the back which from that point will be out of the water. The curve straight bellow from that to points bends at 40cm depth while the section above that it is 75cm at the back and 80cm at front.

@JamesG123 im thinking of this kind of leads: Spherical form or little pieces or powder, i think it could be pumped out but yet not sure :-D