The Melatelia: light wind dinghy

Discussion in 'Boat Design' started by laukejas, Mar 20, 2015.

  1. WindRaf
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    WindRaf Senior Member

    not complicated ... just do the stern little bit v ... and then force the panel during assembly
     
  2. laukejas
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    laukejas Senior Member

    Yeah, I know, I meant that it is difficult to do in design stage. I'm not even sure Delftship (which I use for hull shaping) allows such thing. I'll have to try.

    Messabout, still reading this? What's your take on the situation and my latest updates seen in screenshots I provided some posts earlier?
     
  3. WindRaf
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    WindRaf Senior Member

    the problem is this: more the skin is thin more must stiffen
     
  4. laukejas
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    laukejas Senior Member

    That I understand! Are there any more ways to stiffen it? I'd be great if it can be done without changing hull shape from this one. For example, add a keel timber stringer that runs along the centerline from transom to bow compartment?
     
  5. GTO
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    GTO Senior Member

    A sideways solution

    If your car is the limiting factor, could you sell it and buy a small truck?
    Seems like that would solve all your problems.
     
  6. laukejas
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    laukejas Senior Member

    Nice thought, but that is out of question due to finances. Anyway, the car I have is perfect for my needs, it's just that it wasn't designed for a boat. I have to make do.
     
  7. GTO
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    GTO Senior Member

    I thought you might find a truck for less money than for what you could sell your car. Putting a little extra money in your pocket.
    Jokingly, I must add, if your car can't transport the boat you want, it is in no way perfect for your needs. ;)
     
  8. laukejas
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    laukejas Senior Member

    If I sold that car, I'd get 200$ tops. But anyway, let's not detract from the original goal. Finding solution to make this boat work. I think I'm pretty close. It seems that some people here still have doubts if bottom panel is not supported enough. If it turns out these doubts are not valid, or if I can find a solution, then the problem is solved. Everything except that is within requirements.
     
  9. Richard Woods
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    Richard Woods Woods Designs

    I wouldn't worry about the 4mm ply floor. I would put bilge runners on the outside though

    And I'd use 4mm ply for the transom and bulkheads, in fact the whole boat in 4mm.

    But don't let kids play in it on a rocky beach. If they do, go and sit on their parents car bonnet/hood as revenge. (It always amazes me that people allow kids to play on other peoples boats but would never allow them on someones car)

    My Mirror comment concerned the profiling, not the notch to clear the kicking strap. I'd make just 12mm ply rudder and board,not solid, the glue lines and laminations make it much easier to see what you are planing

    Richard Woods
     
  10. WindRaf
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    WindRaf Senior Member

    ------

    look Argie
     
  11. John Perry
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    John Perry Senior Member

    Very true. Most people own a car, or at least know someone who does, so they are well aware how easily cars are damaged and how much they cost to repair. Most people do not own a boat and when they visit the coast perhaps they see boats as just a normal part of the seaside landscape, like the concrete sea walls or the natural rocks along the shore - so why cant they just sit on a boat to eat their fish and chips the same way that they might sit on a rock or the sea wall. And why shouldn't their children be allowed to play on a boat the same way that they are allowed to play on the swings and climbing frame in a public park.

    Reminds me of an occasion a few years back which was almost a bit amusing. We were road trailing our sailing dinghy across the country and parked in a car park for lunch with the trailer hitched to the car. While we were away a coach arrived with a party of tourists and parked next to our car and boat. Our boat has quite a large and fairly flat foredeck, I think it extends about five feet back from the stem and continues as side decks for the length of the boat. The coach driver and the trip organiser had a buffet lunch to feed the passengers and they obviously thought that the deck of our boat would serve well as a dining table. When we returned we saw that they had spread out plates of sandwiches and sausage rolls, knapkins and a basket of cutlery, even wine glasses and some bottles or red and white all over our foredeck and side deck and there was a line of people queuing up to load plates for a buffet lunch!
     
  12. Skyak
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    Skyak Senior Member

    The current state of your model IS a three plank bottom -I like it -no additional work suggested in my previous post.

    The difference between what you have drawn and what I suggested
    -the inner sides of the seat tanks would be fabric over (under) light frame, not plywood. The smartest design would be an airbag designed to fit well under the seat.
    -the bulkhead moves to the front of the daggerboard box and is no taller than the box
    -there is no front buoyancy compartment in my suggestion. the forward 'deck' would again be waterproof fabric over light frame. You never go forward, so there is no reason for walking strength deck. The only purpose of forward deck is managing splash water -a good high cowling/mast support is important.

    Another point to consider is the deck to car-top interface. The maximum stress the hull sees might be in getting to the water.

    BTW a thin transom supported with timber is a good idea. I also wonder about your plan to use epoxy coating without fiberglass and the weight you estimate for the paint. Paint is paint, epoxy is not paint. There are 2 part epoxy based paints. We can discuss later.

    I will make a little rough sketch of what light framing might look like and pull out the sailplan case. I am sorry I am not keeping up with the discussion but the market is quite volatile and bizarre at the moment. It seems the machines are trying to scare the humans into a stampede/crash.
     
  13. laukejas
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    laukejas Senior Member

    Looks like Argie does it with bilge runners too. I added them to my model. 3x1cm timber strips. Here's how it looks:

    [​IMG]

    Hopefully I can forget about the bottom and move on...

    Great. So I can stick to 4mm. It seems that this boat can be done with 3 sheets of plywood (larger than 4x8 US standard, though) with only two of the chines needing scarfing. This will make the boat much more easier to build.

    As for people with kids and their attitude to boats... Well, that's horrible. But you're right: very few people own boats, so it's hard to expect the rest to understand. It seems common sense to us, but to them... Well, I'll be sure to keep my boat away from any strangers.



    When I wanted to make plywood rudder and daggerboard earlier in this project, people on this forum went berserk on me, saying that plywood is very poor choice because of grain orientation. So I went with glued timber.
    But anyway, if I were to make boards from plywood, I'd have to either buy a 12mm sheet, or glue a lot of layers from my 4mm. That's a lot of work and epoxy. And I don't think I can fit that in my plywood sheets.
    Maybe this time I'll go with timber boards. But thank you anyway for this advice. I'll try to think of something when I'll round and tapper the edges.

    Okay, that's a relief. Sorry, I just misunderstood you. Thanks for clearing it up, Skyak.

    I see. Well, that's possible to do, but it seems that if I go with seats that are lower than sheer line, I'm within weight limit. So maybe it's not worth it complicating it with fabric (which is very hard to get here, as I've searched for when I thought of making skin-on-frame boat). But anyway, that's a good idea. I'll write it down, just in case.

    That implies that the daggerboard becomes very close to the mast. That would really screw up CLR/CE balance with my current rig (standing lug). I'd have to switch to balanced lug, sprit with jib or bermudian rig. Or significantly lower sail area of my current rig. None of these options seem appealing. As I've said, I need a lot of sail area with my 4 meter mast. Some say that lug isn't as good as bermudian rig when going to windward, but people still sail with lugs. So I guess if I make a good sail, it will work.
    So, how would you solve balance problem if you were to move bulkhead to the daggerboard?

    Since car roof racks are narrower than the boat, I'll have to make some transporting beams which attach to gunwales so that boat can be secured on the roof rack, and taken down without damaging anything. I planned for this with my original design (check out the last pages in Building Manual), but I'll have to re-think this now, since it will be harder to attach transporting beams to a simple, non-spaced gunwales.


    Well, for now, I thought of gluing a shape of plywood onto the transom to make it stronger and look better. Take a look:

    [​IMG]

    I don't know if I need to add anything else there. 4mm transom + 4mm reinforcing "wing" seems enough for me, but please tell if I'm wrong.

    I'd like to discuss epoxy and paint question. I plan to buy 5 liters of epoxy (not sure of the ratio, but that is 5 liters in total). I don't think I'll use up all of it. Maybe 2-3kg. Another 0.5kg for thickener (wood flour).

    As for paint, I calculated that there is up to 14.5m^2 of area to cover, if I'm to paint insides of tanks too (I think I should). Boards - another 1m^2, so maybe 16m^2 in total to be on the safe side. 3 coats result in 48m^2, let's round that to 50. Considering 10m^2 per liter, that adds up to 5 liters of paint. Is that correct? I did my research and found out that depending on type of paint, a 30-70% of it's mass is solvent. So I guess I'll take 50% as a middle ground. So paint will add 2.5kg to my boat. Maybe 2kg if I paint interior parts with 2 coats instead of 3.

    I'm reserving another 1kg for hardware.

    So, I estimate (hope) that epoxy, paint and hardware will add no more than 5-6kg to the weight of the boat. Are my estimates realistic?



    Thank you! Looking forward to it. Don't give up with those machines :)




    Oh, and another thing. I thought I could bevel mast partner timber block, and extend bow deck piece on top of it, like Tom suggested. Here's how it looks:

    [​IMG]


    P.S. BTW, this design (in pictures in this post) weights 24.4kg. I personally like it, but maybe it still has flaws.
     

    Attached Files:

  14. laukejas
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    laukejas Senior Member

    As a side topic, I'd like to ask about paint type. I've just researched types of paint for 2 hours, and I'm still not sure.

    Enamel, acrylic or latex?

    I red that enamel is oil based, so it has good water-resistant properties. However, it doesn't bond well with epoxy, and you need to paint it several days after epoxy coating has dried - no earlier, no later - to have decent grip between the two. Is that true?

    I couldn't find much distinction between acrylic and latex, but it seems that many people favor it over enamel. I even red that there are paints that combine the two, and I searched for such paint in my country, but all of acrylic-latex paints are rated as interior grade.

    Can somebody clear this up a bit? Which paint should I use?
     

  15. Richard Woods
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    Richard Woods Woods Designs

    I hope you just got in your car and drove away

    RW
     
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