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

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

  1. socalspearit
    Joined: Apr 2021
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    Location: Los Angeles, CA

    socalspearit Junior Member

    me + 4 for coastal. Coastal is really within the Santa Monica Bay and from my harbor getting to good dive areas within 15 miles of the harbor means we're never more than 2-3 KM from shore and our actual dive spots are mostly a few hundred meters from shore. California coastline is very steep, even on the mainland. Our islands also are even steeper so anytime I'm anchored and diving, certainly with paying customers, I'm likely 100M - 200M from land of some kind. I have run the inflatable for many miles and many hours with buddies (not paying customers) in northern Sea of Cortez which is VERY remote, help on the water is dependent on random panga fishermen, but around Los Angeles and the surrounding islands there is a lot of boat traffic, Coast Guard, and vessel assist insurance, etc.

    Yes, the boat is in fact a freediving platform among other things. That's part of the why I use this design. For very deep competitive style diving we employ a boom with a single line, weights on either end of the line, and two pulleys on either end of the boom. That's what the platform is on top of the jetski float--it's very small but competition legal. Diver goes down/up the dive line while lanyarded to the line, and the opposite line (counterweight line) is for the unlikely event of a deep blackout; it allows a very small team even one person to quickly haul the dive line up (plate pull). Seeing as competitive freedivers go quite deep these days the dive line depth can be in excess of 100M. Plate pulls though are extremely rare, twice in the last 20 years of sanctioned competition. For personal training I use my entire inflatable as the boom arm--dive line off the bow and counterweight off a pulley clipped aft off the side. It can be operated in the water which it needs to be since we of course safety each other in the water and this may be me and one other diver on a weekday, drifting 2 miles out from the coast above a submarine canyon hundreds of feet deep although still within the Santa Monica Bay (most of Los Angeles fronts the SM Bay--the mouth is 30 miles wide). We drift because if anchored in even a small current, a diver doing that kind of dive which is a true physical limit, current will complicate things because their direction of force is required to be into the current and not just up and down, and over the course of a 60M+ dive that force adds up. If we're in the water drifting with the entire rig we're drifting together so current is not felt. Larger profile boat (like the Scoota) will catch even a little bit of wind and start to pull the line. One of my buddies in Hawaii does this off a big RIB with a sea anchor and it helps but it's more to manage and he has more trusted hands helping. For santioned competition it's the same set-up but the platform needs to fit a judge (out of the water), safety supervisor monitoring on sonar and with clear unobstructed view of the water, and if necessary provide enough space for a medic to work on the diver. Typical boats are problematic here because in the unlikely even the medic needs to work on the diver they've got to be hauled out of the water and onto the platform so a high deck and freeboard is exactly wrong.

    My inflatable is also a dive float. A boat like the Scoota would be lousy for that. It's a cool boat but it's too big. By 'dive float' I mean I can pretty easily tow it around in the water and position exactly over the target on the bottom and pull and maneuver the anchor from in the water. My anchor is a 30lb kettle bell. It's really heavy but it means I can pin my boat directly over structure and only let out 5% scope on the line in absolutely any current. Since I can't stand on the inflatable it would be hard to horse a 30lb anchor but by using a pulley off the side it's easy (and I'm in the water all the time the boat is anchored) if I plant my feet against the side and haul.
    20200903-Sinclair-1118.jpg

    I am certainly more than a bit stubborn and I do want to understand my design, etc, but I've been using this long skinny boat for years believe me plenty of people have told me I'm doing it wrong simply because it's too skinny (although not freedivers/spearos who have been on my boat with me). What I do is fundamentally scandalous since 99% of boat design and choice starts with 'dry, stable to walk on, keeps occupants out of the water at all costs' but that's not part of Coast Guard regs and for my application not necessary. Stable when running in weather and seas is VERY important to me and the narrow design does actually deliver there surprisingly well. I have been on a variety of boats large and small doing this very activity and they all have pluses and minuses but at my chosen scale I haven't found anything better. So, while I will try not to be dogmatic about it I need to understand and am going to question when I'm told I'm currently doing it wrong and planning to do it more wrong since so far it's been working very well for me (I do get that there's a big difference in characteristics between the inflatable and a hard boat though). I've been on a variety of crazy freedive platform contraptions--obviously my own but also the Bote Board (this is basically a large SUP which will can be powered by a small gas engine), etc, and it's surprisingly stable.

    All this hemming and hawing aside the boat can be a little wider and still fit the space; Since I've been using a 18" wide interior deck for years, when I put this design together with double that space it seemed like so much but the console is going to take up space particularly if I'm set on rack and pinion steering. On certain calculations there is no relationship between length and stability of a hull but in practical terms in regards to weight on one edge (ie diver climbing aboard) there's most certainly a linear relationship. Five people crammed all against one edge in a direct beam sea on this vessel would be pretty bad but (1) they'd have tough time remaining there and the boat would self right, (2) if I'm in that weather I screwed up before we left the harbor, (3) I am supposed to have enough sense not to steer that way. I live in the water and understand the unexpected happens and redundant safety systems are limited on a small boat but yeah at the end of the day it's a small craft.

    As Bajansailor suggested the addition of tubes on the side I also agree would be great for ultimate stability (Zodiac type RIBs are about the most perfect mass market vessels for my application) but I don't want/can't do anything inflatable or that looks inflatable. I am going to do some beefy gunwales though. They would not offer the bouyancy of RIB tubes but it would protect better than just any gunwale and any imbecile(s) standing in such a way as to cause that much heeling would fall into the water. I might have too much faith in humanity but again, look at the photo of my inflatable, would you attempt to stand in that thing when running 16kts?? If they stand and fall while stopped big deal they're in a wetsuit and we have a laugh then they get back in. For gunwales, the specific gravity of WRC is 0.3 I was already planning on white oak clad kevlar wrapped gunwales so possibly could just go with mostly foam filled to make them even lighter. Another thing, again non-standard on any type of small console boat is to make the console truly watertight. To a certain extent this was already the plan since anything remotely like this needs the electronics protected since the entire boat is subject to lots of water in any sort of weather whatsoever, but a truly watertight console or console with signficant floatation would make the boat not 100% self righting but prevent it from floating upside down.

    I was only using Rhino since that's what the Orca plug-in ran on. I'm doing a true 3D model in Fusion 360 based on these conversations since I know that package better.
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    So design your own cat with low bdeck.
     
  3. socalspearit
    Joined: Apr 2021
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    Location: Los Angeles, CA

    socalspearit Junior Member

    I have very limited experience with cats. I do understand that I'm going from pontoons to modified V but I have thousands of hours and miles year round, day and night, in these waters on an inflatable motor kayak that I've at various points flogged, repaired, almost sank, cursed at, destroyed, improved and modified (I'm on my second hull of this model and fifth outboard) over the last 7 or so years. A cat could be in the future but I have limited time for tinkering. Even if new boat does not perform as expected it will work for my existing business and coastal runs. Even if it doesn't work to increase speed and range with more passengers and reasonable safety, it will be very fast, cheap to run, and seaworthy when loaded ultra light (like just me and a buddy) so if nothing else at least I have the option to run it to the islands on my own time in good weather.
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Socal, I appreciate that you are dead against inflatable tubes - and I can see why, as they don't take abuse well (especially PVC - hypalon should be better).

    But maybe you could consider a foam filled collar instead for your boat?
    I still think that you are going to need something extra if you do proceed to build the boat as per the hull lines posted at the beginning of this thread.
    Here is a typical builder of foam collars - Google should bring up a few more for you.
    FAST Collars - What Are FAST Collars? — FAST Collar Systems http://fastcollars.com/collars
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    BlisscraftOceaneer_Lines_LRG.jpg
    And that would legal be as a charter ? As I say, that amazes me, it would not have a ghost of a chance of passing in this part of the world. But we are a little over-regulated ! It would not be legal as a private boat even, to have 5 aboard what is effectively a quite small boat, with that 4 feet of beam. I would say something like a 17 foot Boston Whaler would be far better all round. Your 60 hp would be underpowering though. If you insist on narrow beam, then I think self-bailing is off the menu, it raises centre of gravity too much, and that combined with narrow beam, is bad news. About the only offshore capable boat I know of you could build in ply, that will run happily with 60hp, and has a self bailing cockpit, is this oldie that dates to the 1960's or earlier. But I wouldn't want 5 on board, three would be comfortable.
     
    Last edited: Sep 6, 2021
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  6. cracked_ribs
    Joined: Nov 2018
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    Location: Republic of Vancouver Island

    cracked_ribs Senior Member

    Not built for high speed and only about 15-6 IIRC but if you haven't had a look at Ross Lillistone's Fleet, you might take some ideas there.

    If I were doing something like what you're talking about, I'd probably look at increasing the beam to 5' and having fairly large internal gunwales with floatation foam.

    Completely different boat pictured below here but this is one I'm working on with gunwales about 7"x7", almost entirely filled with foam. There's nothing even vaguely RIB-like about it, but I have, basically, an internal foam collar. It doesn't have quite the effect of the RIB collar, but you get a bunch of the benefits without the visual drawbacks.

    [​IMG]

    On a design like the one you're suggesting, my thought is that an extra foot+ of beam will barely be noticeable as the boat will still be proportionally so long and narrow and low. But it would give you both a bit of extra stability, and the space to place a floatation collar inside the boat in a manner that doesn't recall RIBs at all.

    Some people are visual learners so bearing this in mind I've created an advanced pictorial guide and visual reference which covers these two alternatives and their outcomes - I admit this gets a bit technical in terms of the diagramming but I feel this forum has so many people with advanced technical skills in the marine field that this will not be overly difficult for everyone to review. If anyone needs help with the figures as presented, please let me know and I will try to scale back my encyclopaedic data presentation to a more manageable level.

    [​IMG]
     
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  7. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Since this is planned in strip planking, tumblehome would facilitate water boarding.

    Also hatches could conceal catch coolers.
     
  8. socalspearit
    Joined: Apr 2021
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    Location: Los Angeles, CA

    socalspearit Junior Member

    Even a foam filled collar is off the menu at least for now (if on execution it becomes a suicide machine I could add a foam collar and make it work) because commercial insurance here is leery of any kind of tube. I did not specifically inquire--and my own insurance co is very boutique and willing to research--but a friend of mine with a beautiful new Zodiac tried to get it insured commercially to take spearos out (as opposed to just 'freedivers') and told me she struck out because everyone she called said the tubes could be punctured by a spear. Nevermind that the Zodiac doesn't need the tubes to be seaworthy and hers are foam filled.

    I did think about the coolers but when I looked at the height of deck and scale of the boat they'd be like 3" deep so we'll stick with fish bags. I looked up tumblehome but that isn't part of the design--how would strip planking contribute to that? Because it might flex?

    @Mr Efficiency All the USCG regs and best practices for home built boats regarding engine size, etc, are based on area and ratios instead absolutes like beam width, and there are some very very small allowances for 'vessels of special manufacture.' The stern light on my inflatable for instance is a 270 degree light pointed backwards which would actually indicate a 'sailboat under motor power' but since a 360 degree light would blind me at night it's allowed. Also, I'm under 20' which gives more flexibility even for commercial use. Regs for COMMERCIAL SALE and mass market are much stricter. Comfort is also very much in the eye of the beholder, my typical client is 25 - 40 yrs olds, a good to great swimmer, and wearing a wetsuit that provides floatation on par with a life vest. The wetsuit won't float a unconscious wearer mouth out of the water but in our waters most people for most of the year would be rolling the dice on death by hypothermia after 6-12 hours in street clothes regardless, with problem solving ability for half that if even. In a modern freediving wetsuit I think most of us would have at least 24 - 48 hours of conscious swimming and problem solving ability. As for self bailing this design is emphatically not 'dry' self bailing. My kaboat is self bailing but the inflated deck is about 1.5" above the waterline if empty. It has a tiny scupper hole about 1.5" that is open to the sea at the bottom of the transom. When we climb back in it usually settles with about 2-3" of standing water that quickly flushes from venturi forces as soon as we're underway then starts to plane nicely. This would be misery for anyone not in full dive gear of course but I actually like that the boat deck is constantly flushing since it washes pee and any fish smutz off constantly. A big commercial charter that has a full load of spearfishermen reeks like a chemical portapotty by 5pm. Also, one thing I've found is that the faster the vessel the less comfort matters. A jetski at 50mph is punishing in the open sea but you don't have to put up with it for long if you're just racing home.

    @cracked_ribs Yeah, I did decide on a beefy internal gunwale, I think that's smart. I am making it a little wider/taller also. A lot of my slip neighbors are small commercial fishermen and lobstermen and while their boats are nothing like mine, they lean towards an inboard V with a high self bailing deck with enormous scuppers and usually giant inwales that are almost certainly foam filled. Beefy inwale doesn't provide the same ultimate stability as external rib tubes but would certainly help and would absolutely guarantee level floatation (USCG does care about this for small boats). This is actually their 'backyard boat builders' best practices: https://newboatbuilders.com/docs/backyardboatbuilders.pdf

    Here are some current renders, with the sections 6% wider and taller, and beefy inwales intended to be mostly internally WRC (which is SG .3) and foam. The nose is a little blocky since I was importing sections from Rhino and didn't want to spend the time making this model look perfect. I will put a person in for scale for reference so realize the helm seat is only 11" off the deck which for a 6' guy means they're virtually kneeling on the deck, so it is tiny. I also just blocked in a console, the final shape will change but those would be basic dimensions. Console I am also thinking to make watertight with foam filled sections to provide a little bit of catastrophic righting ability.

    On the gunwales the plan is a metal safety rail on the starboard side extending 2/3 way back from the cowling and one extending halfway back on the port side. The last render shows the nose section (foam filled and watertight), 18gal fuel tank (compartment built around the tank vented to internal bilge), battery compartment (totally watertight and piped in under the console with pipe terminating high off the deck under the console), and internal bilge. Every other space under the deck will be foamed and wires/cables likely in PVC pipe unless there's something that is supposed to be better. It has a 'well' in the back and I haven't drawn in the scuppers but I'm thinking two or three 3" holes at the bottom of the transom. Based on the initial Orca sims and my experience with loading, weight, and waterline water area on my inflatable the deck should still be 4+" above the waterline with 4 people in it, and then underway venturi forces take care of draining the boat very fast provided there's no fancy plumbing. Internal bilge and fuel tank cover would be engineered 100% watertight and theoretically only get water in if the entire transom submerges. I'll likely also have at least one giant bilge at deck level there in the well that shouldn't see use except in catastrophic boarding seas. Forward holds are for anchor and lifejackets. I'd like a dedicated spot for a DAN O2 kit and was originally thinking to put it under the helm seat but the case is too big. It will likely just be strapped to the hull near the transom.

    SpearIt_One_v2 v12_a.jpg SpearIt_One_v2 v12_b.jpg SpearIt_One_v2 v12_c.jpg SpearIt_One_v2 v12_d.jpg
     
  9. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Tumlbehom's slope towards the water could be a ramp for re-entry. Having a sharpish angle on the inside would be a handgrip.

    Tumblehome is almost impossible without strip planking. There are compound curves that sheet material can't accommodate easily.
    Trying to do it in fiberglass requires multiple joints in the mould.
     
  10. socalspearit
    Joined: Apr 2021
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    socalspearit Junior Member

    Okay thanks. Yes, when I rotated my cut section guides to look at righting arm etc I noticed that about the shape, although in my boat with such low sides it would be virtually impossible to stay in the boat when heeled that far. Seas and freesurface effect of course complicate things but while I want a very good weather margin I'm not actually taking customers out in that weather. The weather that my friends and I are happy and comfortable diving in is more than my typical student. The fatty inwales though provide *a little* extra safety there especially since the sides are so flat--if the hull rotates and the freeboard edge nears the water it's generally going to be the entire length of the edge which provides some ultimate stability, moreso than a lot of more circular designs. I am certainly realizing that for my hull shape I could do plywood, but the WRC is just so so light which for my SOR is a big plus.
     
  11. socalspearit
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    socalspearit Junior Member

    Re: sharpish angle The boat is intended to be boarded mostly portside, aft of the safety railing. I might angle the gunwale inwards there or even router in a finger trough. I was thinking of that; the gunwale can't be so wide that it's impossible to grip. I felt like this thickness is something that a mans hand can quite comfortable grip but an internal sharp angle right there would improve it.
     
  12. Blueknarr
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    Blueknarr Senior Member

    I hate diving off of inflatables because there is nothing to grab to assist re-entry.
     
  13. Blueknarr
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    Blueknarr Senior Member

    Excuse the draftmanship
    20210907_115552.jpg
     
  14. socalspearit
    Joined: Apr 2021
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    socalspearit Junior Member

    All this talk did make me realize, boarding for freedivers wearing fins is much easier and I take that for granted. My inflatable is low to the water with helps immensely but with longfins on I can breach almost to my hip bones with a few kicks (even easier if I've taken off the weightbelt), so we basically kick/pull ourselves over the side with the safety ropes and flop into the boat. Even very junior students do pretty well unless they have zero upperbody strength and don't understand how to kick the fins but those are very much the exception. If I was running more 'snorkel tourists' I would be dealing with that constantly but I make it a practice to only take out freedivers who have some formal training/cert. Vessels with a high freeboard like a typical fishing boat I can still easily heave over the side but then I'm trying to balance on the gunwale to keep from crashing onto the hard deck while I'm swinging the cumbersome longfins over the side as well.
     

  15. socalspearit
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    socalspearit Junior Member

    Small Whalers and Parkers are great boats and very popular here for my application, but they are pricey and heavy (so expensive to purchase and run at speed). They make certain compromises (or advantages depending on who's considering) though because they also double as good H&L fishing vessels and family boats, which again isn't necessary for me. I didn't ride it but once on an island run we basically raced my friend's tiny Whaler in a Zodiac RIB of the same size and engine and we couldn't keep up due to the pounding. From what I've seen though the problem is they really aren't engineered for hard commercial use. They are tough boats but they get destroyed or at least very quickly lose any luster because they're fiberglass so it chips when somebody drops a weight belt on the deck--your friends know better than to do this but not a seasick student. Cushions are comfy but quickly get stained and need repair, etc. You can lay mats on the deck to protect the fiberglass but I suppose I just want to reinvent the wheel.. I have a buddy that used to run bluewater spear charters off a beautiful 26'ish foot Whaler. He offered an incredible trip but had to price himself out of much of the market due to the fuel cost, and his lovely boat very quickly started accumulating chips and stains, etc, and he quit doing it since it just wasn't worth it to him. If I was doing that I'd look at a beater boat with a little bit of life in it and a new motor, or maybe build a plywood tank like many of the offshore fishing designs I see. Or you scale up to inboard diesels and 50' boat that was built to take a beating and run slow but cheap and provide enough room for your passengers to sleep while you putter to the island (like pretty much every single successful operation here). I'm not actually offering a standard '6 pack' nor do I want to do but at that scale it's kind of tricky. I do know a guy that has about a 26'ish aluminum commercial fishing boat that he bought from a guy in Alaska but while it's virtually indestructable his fuel cost is high and it cost a fortune.
     
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