Custom 19' all weather, minimalist, strip plank composite 'go fast'

Discussion in 'Boat Design' started by socalspearit, Sep 2, 2021.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I was getting that impression ! I guess it is boatdesign.net, not whatboatdoibuy.net ! However, I think if you go the right way about it, you are going to land upon something that isn't radically different from stock boats. I wouldn't think there is a lot of room to move in designing a boat that is "all weather" and "go fast", powered by just 60 hp, that needs to carry 5 people, offshore. Something will have to suffer, and given that discomfort can be tolerably accommodated by young, fit, eager people, it will have to become the "first casualty" in this case. I wouldn't be thinking slender, that doesn't offer much safety, certainly not with a raised sole, or much ability to plane easily loaded up with 5 people. About the only thing I see as meeting the specification, and accepting that it will be an ordeal in a long run over choppy water, would be a near rectangular-plan, moderate vee bottom, vee nose punt, that fulfils the requirement for self draining, with the sort of power you want to use. Something like this: 5.4 Fly - Nest C-2016 (platealloy.com)
     

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  2. socalspearit
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    socalspearit Junior Member

    For a combo fish and dive type rig on a budget that design looks okay, and the swim step is certainly nice. It would make a horrendous dive float though and tug horribly if anchored or drifting in wind. I have been in plenty of boats of similar build and the whole 'long run over choppy water' aspect is one of the main issues with most of the beamy hulls I've experienced with some being better than others. The bow design of that Fly Fisher which pushes water I have heard is surprisingly good in rough seas. There was a guy local I read about years ago that got really into building solo all-weather crafts for our waters. He built a bunch and tested them in storms and according to what I read decided the absolute best thing was that sort of a bow, with a very big engine (like a 150hp in a 16' boat) steered by a tiller. He didn't boat while wearing a wetsuit though and didn't seem concerned with fuel economy.

    My experience otherwise in the beamy planing boats is that they generally slam a lot so you have to go slow or spend weight and money on protecting passengers and at slow speed the thing squats badly and sucks gas, etc. Maybe it's Stockholm syndrome but one thing I love about the long skinny design that I've experienced on my inflatable over the years is that it stays level at all speeds and acceleration, attitude, and fuel consumption stays linear (ie nice anywhere in its speed range). Across open water we want to point in a particular direction and get there fast but once at the islands or in the area we may putter around when investigating spots.

    My inflatable doesn't really 'jump' up to plane, being more semi-displacement it just kinda cruises and depending on its loading it either planes right on the surface or kinda planes low--when just me with no gear and the 15hp engine it skips like a stone and feels squirelly and unsafe due to its handling and the fact the entire boat is cheap garbage; we're talking about 15hp pushing a total weight of about 340lbs across the water at 19kts. It runs best with me and two small people or one big guy; top speed is still 16-17 knots including in following seas and the ride is somewhat comfy. This is very much a weight issue; back in the day just me with a 6hp in the same model hull it does kinda plane at 13kts but even one more person and the speed drops way down to about 9kts and it never really felt like it was planing. A lot of my speculation this regarding new design is based on the weight characteristics which I admittedly don't have direct experience with--stitch and glue vs cedar plank, etc--so I'm going off the weight I feel in WRC and carbon fiber vs marine ply and fiberglass etc. Most all of the boats I've been in besides mine are fiberglass and foam. Most of the actual small commercial fishing boats in my marina are wood/fiberglass composites although much heavier than what I'm planning.

    If conventionally built like what I see in most of stitch and glue type plans a hull intended for a 60hp engine would likely weigh 500lbs or more. Since the inflatable still planes quite nicely with a 15hp pushing a total of 750lbs (weight of boat, engine, and 600 pounds of passengers and gear), I am figuring an ultra light stiff hull weighing under 200lbs before people, engine, and gas will do fine if pushed by a 60hp. I would expect it to be much slower with 5 people in it but I would expect it to make still at least 20kts, which is plenty for coastal seeing as I can currently carry only half as many people a slower speed.

    But then with just two people or even just me running up the coast to meet a buddy at one of the northern islands I am hoping it goes a good deal faster; something that light should actually get a little lift out of the chines, which in relation to the total wetted surface area of the bottom are significant. Since my keel piece is still roughly a 2" square I was thinking to just do less shaping of the keel and let it have a narrow delta pad at the transom. I saw plans for little bitty racers intended for up to 50hp that are true planing hulls that advertise up to 50kts but they carry one person and only work well if up on plane in calm seas.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    Well, I see a business where the safety of the customers ought be a high priority, but you need to run on a shoestring budget that cuts corners with safety to make it viable, as being an unsound business model, I think it is unconscionable to not make safety the first order of business, and that is not consistent with the type of boats you use, and envisage using. It would surprise me if you don't get people coming to the dock, saying they are not going out in "that".
     
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  4. socalspearit
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    socalspearit Junior Member

    Safety is a huge deal, that's why I'm still in business and am busier than I want to be. I don't advertise boat tours in the yellow pages, it's not that kind of a thing. I'm not just a charter captain, I sell a service and it sometimes involves a boat. I'm busy enough that I don't need to take just anyone out. There are plenty of boats and captains in my same harbor who sell charter tours on a big, dry, mostly idiot proof boat to anyone who will pay them $1200 a day. That's not my service. I started lifeguarding in the summers when I was 14 years old. I swam competitively for over a decade and have a long silly freediving resume with a smattering of national and world records, and years of spearfishing photos and videos. My clients have a great deal of faith in my ability to keep them safe in the context of our activity (which does not involve being dry on a boat).

    I only take out certified/trained freedivers, not snorkeling tourists or inebrianted fishermen and children. All my students have some water experience, some of it quite serious. If they're not comfortable with the ocean they don't come to me. This is a coastal city. Most people here drawn to formal freedive training grew up in and on the water. I mean they all have some surfing, or are already spearfishing and want to do it better/safer, competitive swimming, triathlete, ocean lifeguards, ex-military or aspiring special forces, USCG rescue swimmers who want to get better with breathhold, scuba divers and instructors, stunt performers, the occasional actor who needs training for a part, etc. Those are just the students who are taking our 'Level 1' type class. The Level 2 is mostly people who work IN (not ON) the water as part of their job including military/law enforcement or are least incredibly dedicated and passionate about it: tournament spearos, or aspiring competitive freedivers.

    If/when they finish the level 1 cert they will have swam 1/2 to 1 mile in open water just to get to the training rig off the beach, dove on a breathhold to at least 30' - 40' with good technique (ie not freaked out and panicked), held their breath for at least 90 seconds in a pool, and learned and demonstrated numerous surface and subsurface rescue techniques which are specialized for our activity but are comparable to most of the water skills of a Red Cross basic pool lifeguard class. Those are the minimums; most of the students have achieved 3+ minute breathholds actually and may have dove 50' - 60' during the class. If they discover over the course the of the class they aren't as good as they thought they were or that this stuff is a lot harder than it looked on youTube then they've at least done the swimming, pool breathhold, surface rescues but maybe not the depth, plus I've spent at least 18 hours in two days with them and five others so I've vetted them. To get in the water with me and a loaded speargun there's more vetting.

    So, to board my boat they've done all the above with me or the equivalent with another reputable freedive agency, plus they're in a freediving wetsuit which is like an incredibly warm, head to toe, watertight lifejacket. They aren't worried about being wet, or falling into the water, or some waves, and I'm not worried about them in that regard. Most of them have seen photos or videos of my stupid inflatable and heard stories so they're looking forward to it. Currently I am within a mile or two from shore, still inside the bay when running paying customers, and I don't take anyone out when there are small craft advisories. At this point, after many hundreds of students on my boat nobody has ever gotten to my slip and said they weren't "going out on that".
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Yeah, well on several occasions I recall boats go missing with champion swimmers and lifesavers etc on board, with people saying he is bulletproof , he will show up, and of course never seen again. You don't ever want to put yourself or anyone else, in a situation where such abilities are put to the severest test, because a boat failed to handle conditions.
     
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  6. socalspearit
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    socalspearit Junior Member

    Very much agreed. I'm not trying to design and run a boat that's an all weather rescue boat (leave the harbor in a storm), and I'm not proposing that this boat is something I'd want to run in other seas. I want a comfortable weather margin especially for my own personal use, although comfort's obviously in the eye of the beholder. This boat, as with any boat, would require the operator make sound judgements in regards to weather, loading, passenger experience together with a healthy breadth of experience in the region of use. Most of my time on boats has been spent in SoCal but I've been on various small craft all over the world. I would not care for this design around Florida Gulf Coast for instance where you aren't island hopping (ie shooting the channel to get from one sheltered spot to another) but maybe out 15 miles in the open sea where the dive spot is, and where normal weather includes sudden, unpredictable squalls and wind where visibility suddenly goes to zero in a sideways rain with some very dramatic lightning to boot. This is not a boat intended for our local offshore bluefin hunting which is much closer to traditional 'offshore' hook and line fishing--some of the most successful small boats for that kind of spearing are catamarans. I'm in the Pacific, southern California. We have very consistent prevailing swell direction and wind and a coastline that is dotted with harbors and a large island that breaks weather. Catalina for instance is 25 miles off the coast but it's 22 miles long so it functions as an enormous breakwall for most of the Santa Monica Bay. We get storms but they build very slowly and obviously over the course of days. Our winter weather is less predictable but once weather conditions get even unpredictable (not necessarily even bad yet, just less predictable) the Coast Guard issues a small craft advisory. For students the boat is off the menu and we end up shuffling the schedule towards pool or dry work or just reschedule open water. Luckily our weather is good enough--in Southern California mind you--that it's very rare that I have to reschedule due to weather.
     
  7. socalspearit
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    socalspearit Junior Member

    This is with a big guy (likesay 6'1" 230lbs) in it. It's a surfboard with sides and gas engine. The hull sides at the fore could be built up a bit higher (strip plank this should be easy in execution, just add another strip or two) and safety rail could terminate right into the edge of the hull there. It would certainly make a sick RIB. Safety would be very much a function of loading; I've been on a carbon fiber racing yacht tender RIB that had probably the same actual waterline area but 10 people stuffed in it (this is inside protected waters in the Bahamas, and not for hire, just somebody shuttling freedivers across the bay). Subject to testing but I think 5 avg sized people inside the bay at the most and 3 people in good weather on a island run. Less predictable weather, running out to the northern Channel Islands from the Santa Monica Bay probably no more than two people, and not done commercially.

    SpearIt_One_v2 v13_a.jpg
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Yes, I appreciate that local knowledge of conditions is a huge factor, and if you don't push your luck by going out when things might become marginal, you are starting from a much more sound position.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I'm not a diver, but normally someone stays in the boat when (scuba) divers are out from what I have seen, is that not the case with you ? It certainly seems prudent from a safety viewpoint, but that is not the same as freediving.
     
  10. fallguy
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    fallguy Senior Member

    That boat is just slightly more dangerous than the jon boats or narrow aluminum boat of years ago that resulted in so many drownings in northern america.

    The problem with them is a 2' chop makes them rock like mad and a 3' wake makes them go over.
     
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  11. Mr Efficiency
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    Mr Efficiency Senior Member

    I wouldn't venture out in it, I know that, call me timid, but I was a professional gambler for many years, and I know the value of putting the odds in your favour. But as the OP says, local conditions may give more latitude. You better be able to read them very well. I was caught out once by a severe storm, and would not be chatting here if it had been a lesser boat than it was.
     
  12. fallguy
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    fallguy Senior Member

    I believe a way to deal with a narrow boat and increase the stability might be to add a deep keel which is also heavy. But I have no idea about the limits in a planing craft. The best way to do things would be to find a way to get the big barge out of the slip or modify the barge to go under or be a part of the main vessel. But I don't have creative ideas.
     
  13. socalspearit
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    socalspearit Junior Member

    My vessel and passengers are not covered under commercial insurance if I'm out of the boat, but I'm only out of the boat when my divers are in the water in which case they're covered under my divemaster policy. So, if I lose the boat when I'm in the water, well I'm SOL and it's on me, but particularly with students we are usually within a hundred meters or even closer to the boat. In open water and certain spearfishing situations DEFINITELY somebody should be in the boat but that isn't typically what I do with students. We're always diving coastal or next to an island, anchored with a 30lb kettlebell on a bottom I know well, etc, god forbid if somehow I should entirely lose the boat we're likely a few hundred meters from shore (even at the islands). Safety wise I need to 100% be in the water with the freedivers, not on the boat.

    I'm not building a boat to sell to the general public, and in my case we're further assuming sober experienced operator and sober passengers who are very difficult to drown given they have proven swimming skills and are highly bouyant in a wetsuit. Even wearing their weightbelt they're still bouyant at the surface if unconscious--that is the first weight check everyone does when we start teaching them, first in the pool and then in the ocean (on a shoredive).

    Rocking in a wake certainly matters and my inflatable probably does that but we barely notice since we're sitting on the floor which is only 3" off the waterline, and as a sober experienced operator I am supposed to notice wakes and steer for them so the boat doesn't slam. My dad had a little flat bottom aluminum boat that we used to take fishing in freshwater when I was kid. This was a long time ago and we could both swim well but I don't remember that boat having any sort of foam or floatation whatsoever. I doubt it would be legal for sale anymore in North America.

    A flipped or swamped boat is no good for anyone but conservatively (including generous allowance for 'structure') this design has 15 cubic feet of foam in it to provide about 850lbs of floatation, and per USCG calculations my max passenger/cargo weight with a fully rigged boat of this design and full tank of gas comes in around 900lbs (20% of total displacement if submerged to the freeboard edge). Again, per the calculations on the USCG regs I'd need to have minimum 245lbs of floatation and float level if swamped.

    In my experience with my inflatable, loading is a big deal. It's actually rated also at 900lbs capacity. At about half that weight it gets very sketchy in bigger seas, not what we get on a daily basis but 'moderate' winter storm conditions--6'-8' swells and 20 - 25 kt gusts. Admittedly it was very stupid but years ago I took off in a gale (steady 30 kts with bigger gusts), just me and the fury of the new 6 horse outboard. I got about seven miles across the bay before I turned around. Again, I'm perhaps too comfortable in the ocean so I wasn't worried for my safety but was pretty sure I was going to lose the boat and more importantly the outboard. If I'd had more weight in the boat, despite steering the bow into the waves, it would almost certainly have foundered in such a way as to render the engine inoperable and I'd be swimming to the beach and making some embarrassing phone calls. Again, this would be stupid and not anything I'd repeat, but a bigger engine in those seas would have been so so much better (part of why I use a 15hp now). If that boat is not moving (ie stalled or sputtering engine) it behaves very poorly in weather because the scupper loses venturi effect and drains slow, so my confidence in the design is very much predicated on a reliable engine.

    For the narrow boat and low freeboard I've found direct beam seas together with high wind that creates short period, high breaking waves to be a very, very bad combo as you might expect. That's not our typical weather though, and again I know it's different but the inflatable does superb in following seas, fine in any type of quartering seas either coming at the stern or bow, not unsafe but quite the sluggard when running directly uphill, and fine in beam swells but again very bad in chop coming right up against/over the side. Catalina island is SW of my harbor and our prevailing winds and swells mostly come out of the south and/or west so returning in the afternoon we're usually in a combination of following seas with morning or after dark being mellow.

    One advantage also to low freeboard and low profile boat is it doesn't get pushed by wind. Again, the experience is not for everyone but if the boat can't/won't sink and the occupants aren't averse to buckets of cold seawater, not getting shoved around by wind can be quite nice. I've been on plenty of big tall style center console fishing rigs that are heeling alarmingly in the combination of strong wind and waves and I'm still being drenched.

    It took me forever to find this but if anyone reading this thread is looking for the actual USCG federal regs for all this: https://www.uscgboating.org/images/514.PDF

    Understood, I've been caught out offshore in some squalls in Florida and it's not fun but again, where I'm at they call it the Pacific for a reason...

    ---

    While I may not agree with all the opinions I do appreciate them, it's forced me to study and do formal calculations and consider things which I either take for granted or don't really have much experience with.
     
  14. socalspearit
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    socalspearit Junior Member

    I realized a while ago that I was basically designing and wanting something more similar to the original Cigarette racing boats before tunnels and steps, or some of the modern military/SAR types, but done on a much smaller scale with an engine that's very conservative by those standards, even for the size/displacement of the boat. There aren't a lot of public resources for those designs and specs. Compared to what I'm building, I've been on some South American island water taxi's which are maybe the closest thing at this scale I've been on---usually very long and narrow by most people's standards, conservative engine, wood construction and little to no deck or floatation but generous freeboard to contain passengers, can feel very 'tippy' when boarding but very stable once underway. I was never in one in a storm but the operators said they're super solid when running in weather and I'm inclined to believe them since in those kind of places vessel assist is not a cell phone call away.

    The self righting boat designs (these are the high end military and SAR) seem to all incorporate a heavy keel which makes sense. I don't think there is a way to keep an outboard operational if the boat rolls. These are so far beyond the scope but these are incredible--stable attitude at all speeds, self righting, no pounding, displacement hull with a kind of planing ability: Rafnar Maritime https://rafnar.com/
     

  15. fallguy
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    fallguy Senior Member

    9C696430-C584-4B84-A35C-AA6B53A21369.jpeg
    The reason the rib doesn't roll over is the buoyancy chambers are to the outside and loading them only occurs with some counterweights.

    An extra narrow vee hull behaves differently; more like a pencil.

    Did you ever see anyone board a jetski from the side? They can't. The reason is the jetski beam is too narrow and the center of mass is too high. Your drawing looks awfully close to a jetski; thus I mention. I feel a bit like a fly for you at this point, but I am hoping you rethink.

    Here is a simple test. Take two pencils and tie them together. Put them in the water and try to capsize them.

    Now, take one pencil and see if it will spin.

    Can a Boston Whaler 13' fit in your slip? That'd be a lot better hull than a 4' wide vee. Here is a picture of the bottom of one. Probably could even load from the side.
     
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