Sea Sled Madness: It's Incurable

Discussion in 'Boat Design' started by DogCavalry, Dec 22, 2022.

  1. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    As one or two people may be aware, I experienced a few challenges building Serenity. She's far from done but she's working and making some money. But we generally use our commuter Lime, because she's a more practical size for daily life.

    Unfortunately our sweet Lime is leaking a couple gallons an hour. Maybe I can fix that. Outside in the snow. But whether I can or not, we will want a new commuter sooner or later. I'm thinking a TX18 or HS18. And this time I'm allowing enough lead time to finalize a design.

    https://www.boatbuildercentral.com/product/texas-sled-18-boat-plans-tx18/
     
  2. baeckmo
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    baeckmo Hydrodynamics

    Don't start by backwards engineering from dreams now, start with a SOR!!!
     
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  3. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    That's the plan!
     
  4. bajansailor
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    bajansailor Marine Surveyor

    Can you post more details (if known) about the leaky Lime please?
    Repairing a leaky Lime in the snow is probably still easier than building a new boat...
    And folk on here can perhaps help to advise how to effect a repair, once you know where and how it is leaking.

    Re the new commuter, does it ABSOLUTELY have to be a Sea Sled?
    I can see how Sea Sledding can be an incurable affliction, but even so, there is no point in building one if the SOR suggests that another type of boat might be more suitable for your commuting purposes.
    Please do post even your initial thoughts so far re your SOR for this new boat.
     
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  5. fallguy
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    fallguy Senior Member

    I agree with the sor refinement.

    The Texas Sled 18 is not suited for a cabin as indicated by the designer. Since I am experiencing significant challenges with my boat related to the cabin weight; I think you might consider a soft top; so when the weather is kind it could be used open.

    You can also build the TX18 at plus 10% in two directions, beam and length which will help with any issues related to cabin weight if you respect weight. But it'd still need to be ultralight, like cedar strip or foam with 6 oz skins. Keeping the weight aft would be critical, and so avoiding tempered glass for example would be best. And, building low headroom and not maximizing the cabin for a larger boat, etc.

    But a softtop would allow more headroom at less weight which is perhaps a compromise. But here in Mn, we have such horrid temps, everyone uses full enclosure soft tops on the 18-20' boats used for long runs. They don't heat the inside, but the wind and splash is zero.
     
  6. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Re Lime: there's always water under the sole, even well forward. Move around and tiny fountains come up from the screw holes scattered around. Even when it hasn't rained in weeks. But our bilge pumps failed, and after about 15 hours the bilge was filled, about 2" water on the sole, fuel tank floating. That's a fairly quick leak. Anne likes to go fast, even in rough weather, so there's air time, and hard landings every couple seconds on some trips. If it's a puncture it mightbe stable, but a crack spreads faster as it covers more surface area. There's going to be one slam too many...
    I'll get her up on the stony shore tomorrow and see.

    SOR
    Less than 20' long and 8' wide 6.1*2.4m
    Seats 4 inside
    Extremely stable platform with great load carrying capacity.
    Square bow really assists hand loading and unloading operations.
    Sometimes it will be just me and my cup of coffee, sometimes 3 guys, their tools, and 15 bundles of shingles. So it needs to be a hull form that has very little planing resistance hump.
    Easily driven in an underpowered state.
    Comfortable ride on rough water. Not haulover inlet rough, but sea state 3, occasionally 4
    Must be able to close up the accomodation weather tight.
    Must be possible to get out to the bow area while under way.
    50hp outboard is the target power
    Edit: forgot range. Typical trips would be under an hour. Most common trip is only ten minutes.
     
    Last edited: Dec 23, 2022
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  7. fallguy
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    fallguy Senior Member

    power on this one is more than your wishes, but this is to show you the tops we see here all the time

    the TX18 plus 10% in either 2 or all directions would work this way
    E5B493D9-78E9-48E8-97DF-438DA2CDA955.jpeg
     
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  8. TANSL
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    TANSL Senior Member

    Preferred hull material and type of construction? Maximum load? Although autonomy is not a problem, you probably have to define if you need to have structural fuel and/or water tanks, as well as other necessary equipment.
    The square bow does not seem to fit well with the need to ride well in high waves, although it is solvable but by complicating the construction.
    In short, the first and most important step to avoid getting a frustrating boat is to carefully define its SOR and with it, the characteristics of the hull can automatically be deduced. Talking about the type of hull without having a well-defined SOR is a waste of time.
     
  9. baeckmo
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    baeckmo Hydrodynamics

    So, what's the weight of 3 guys, their tools and 15 bundles of shingles? You refer to trip time, that is nonsense without knowledge of the distance. What is the trip turnaround distance, and what time is allowed for the longest trip? What is the time rate for three guys sitting idle in a slow boat, waiting for arrival at site? That number will tell you what cost is relevant for investment in speed. What is "great load carrying capacity"....how much in kg's and how fast and how far; numbers, no gut feelings!??

    The power limit you have stated (on what ground?) will be the major design driving factor together with the tree guys with equipment and the associated max operating radius. That combination will decide what waterline length is required in order to have an adequate slenderness ratio (LWL/displacement^0.33) to avoid high hump resistance and where the Center of Mass should be for different hull shapes to trim correctly and to behave decently in a seaway.
     
  10. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Thanks @baeckmo and @TANSL and @fallguy for the tough questions. Easy questions don't perform the necessary audit of my thoughts.

    Three equipped carpenters, and their day's materials weigh ~1700#, mass 770kg
    The longest trip I foresee outside of a special occasion is 6 miles 10km each way.
    The idle rate for those guys is US$140, 120 EURO an hour
    The distances are short enough that getting on the plane at all at heavy load will do.
    I stated 50hp for local realities. Outboards are still in short supply around here, and a neighbour has a good used 50 that has been gone over with a fine toothed comb.
    The dimensions 6.1*2.4m is a hard limit. That's the only slip available to us at our marina..
    Materials: We still have enough glass and epoxy to build a boat this size, so strip plank composite or stitch and glue.
    No water tanks or other amenities needed. This will fill the role of a pickup truck.
    TANSL the square bow is a feature of a sea sled. About a third of the time I've worked from Lime, so I've come to appreciate the front deck for loading, unloading, and general operation. I really miss it when I don't have it.
     
  11. baeckmo
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    baeckmo Hydrodynamics

    Fine, that's ok for the first design spiral turn!
     
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  12. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    The TX18 and HS18 I mentioned in the first post are sea sleds from bateau.com. They are stitch and glue boats, and many TX18s have been built.
     
  13. fallguy
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    fallguy Senior Member

    Well, I'd at least push the length to the length to slip max unless the engine is included, so 18' is a real limit. I can't think of many planing hulls that'll carry 5 square of shingles.
     
  14. fallguy
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    fallguy Senior Member

    The garvey 18 has 2500# displacement and the sled is like 1800#, so not to overlook the garvey hull
     

  15. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Hi @fallguy , I downloaded the Garvey study plans. It can carry some load, but otherwise it misses all the marks. Best contender is the HS18, or a vertically stretched TX18. The wide stance is great loading heavy material over the side or bow. The usable front deck. And @baeckmo reported that his own sea sleds had very little planing resistance hump.
     
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