Custom Multihulls

Discussion in 'Multihulls' started by member 76956, May 8, 2022.

  1. member 76956

    member 76956 Previous Member

    I'm not on the water yet and have been noodling with the idea of building. The cats and tris are probably more expensive than they need to be and the Harry-Proas, seem to be lacking in terms of interior space and comfort. The smaller ones really not having room for a proper cabin.

    The cats are superior for interior space and comfort and the Harry-Proas are superior for handling characteristics, and economy of construction and maintenance.

    I'd like to flesh-out some ideas for combining the best of both, according to my own vision. What I'd like is some assistance fleshing out my ideas, in a way that makes sense to yachtsmen.

    Can anyone recommend a few members who are willing to listen to some occasional brainstorming ideas?

    I'm in a white-paper phase now and that will likely be the majority of my content.
  2. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    tmz. This is a good place to discuss ideas. Many people on this general forum are professional designers or have solid building experience. You will get diverse ideas with often positive improvements. You will also get a few questions. EG what is your statement of requirements? Do you want to go offshore? Do you want cruising or racing speeds? What is your preferred build material? How many people are you long term sailing with? Etc. The reality is the bigger the boat the more time it takes to build irrespective of the style of boat. A 40 foot Harryproa may take 3000 hours, a 40 foot cat or tri may take 5000 hours but some people will take twice as long if they want perfection or half the time if they really know what they are doing and don't want perfection.

    My contribution is this. Please look at second hand boat advertisements first, get a feel for accommodation layouts versus potential speeds and the price of the boats. Be very assured a good second hand boat can be had for less money than a well done home build. Yes, there may be some repairs required but you will be on the water fast. Next study existing designers portfolio's. The cheapest investment you can make is a good designer. The structural aspects of a design are significant in a multihull and many small details are really important. The differences in hull shape over time have been significant. The perfect round bilge shape is being superseded by simple to build chine shapes for fast cruisers etc.

    Fully support you to explore your ideas. Please tell us more about what you want.
    Skyak and bajansailor like this.
  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    @oldmulti you nailed it perfectly above /\ /\
    Not just for multihulls, but most of it applies equally to monohulls as well.
    It should really be 'stickyed' - or at least made easily available to everyone who has dreams of building their own boat.
  4. member 76956

    member 76956 Previous Member

    Thank you for your kind reply

    I chatted-up Rob Denney the other day and he was generous with his time. He really knows his craft. That being said, all of his design decisions aren't perfect for me.

    I agree with you about the second-hand boat market; and, that's probably where I'll purchase from, in the next 12 to 15 months. I want to get on the water, asap, and save more money. I'm not married to building. That being said. I'm probably going to start with my idea of a Magnum Opus, and then lower my expectations as time goes by.

    For me, it's going to be offshore, as fast as possible, with as much space and comfort as possible. Maybe just myself, max occupancy two adults, two children.

    Rob's website quotes 21 knots for the C60s. I also seem to recall it stating that for Harry-Proas, a single handed sailor can drive and maintain a vessel up to 80', such as the C80 Orbiters. This seems a bit optimistic to me; but, it is an unstayed rig, that can be antifouled in knee-deep water. Not having to dive or tune rigging makes a huge difference. I'm almost willing to believe it.

    Rob's Harrys use knife-edge hulls. There's hardly any room for additional accommodations, storage, etc in these. A hull design that I liked better was on "Herbie" the Volkscruiser Proa. The designer describes this as a Sampan hull, with Aircraft-carrier decks. I liked this a lot. Plenty of room in there. Why be limited to the windward-hull. It also seems to me that the space on the beams, between the hulls can be used for another enclosed accommodation, galley, or workshop area; but, none of the designers are currently using it.

    Frankly, I'm not married to the Harry-Proa idea either; but, having a Schooner-rig on the lee hull and a superstructure on the windward-hull can create an Aircraft-carrier "like" space between the hulls, that can be used for cargo, extra accommodations, etc., as previously mentioned. This is kind of the vision I have in mind, which might require cat hulls or dual-inline windward hulls that maximize this area and make it rectangular instead of trapezoidal. I may want to add landing-ramps at both ends, or in the middle, with a tender wherever it will fit.

    This is really a paper battleship; but, the design effort is something I can learn from now; and, if ever realized, can be a very flexible vessel with utility and comfort. Who knows, maybe, I'll want to ferry bespoke cargo while cruising. In such a vessel, I may just be able to do it.

  5. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    @tmz have you built any boats before?
    If not, then it might be better to start off fairly small, perhaps with a tender for the second hand that you might end up buying in the near future?
    And see how you like it, re possibly building your own cruising / working cat later on.
    guzzis3 likes this.
  6. member 76956

    member 76956 Previous Member

    Sound advice regarding building.

    *In the meantime, while I dream about my superyacht in the sky, are you aware of any Harry-Proa "models," wooden or otherwise? I'd like to explore different hullshapes and other options, on the kitchen-table, or maybe even a lake, under-power, before committing anything to paper.

    If nothing like this exists, which I suspect it doesn't, multi-angle orthographic drawings will help give me a feel for the proportions. Then I can just kind-of eye-ball it.

  7. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    A 12m Harry requires less $ because the other hull is shorter. The trouble is the short hull is the accommodation. You get 30' cost and accommodation. The long hull probably helps motion in a seaway. Rob uses fairly light glass and includes instructions to build your own masts and a cheap rational rig.

    So a harry is a good idea, but they aren't magic. You don't get something for nothing.

    Shunting is different. I wouldn't say it's universally superior.

    Would I have a Harry ? Absolutely! Would I buy one over a cat same size condition etc ? Dunno. It'd depend on the specific boats.

    "For me, it's going to be offshore, as fast as possible, with as much space and comfort as possible. Maybe just myself, max occupancy two adults, two children."

    You are basically saying you want everything. You can have everything but it costs. If a 50' cat comes on market with 12:1 hulls a good rig, foam/glass hull, sensible layout, good fitout everyone will be chasing that boat = $$$$$

    That's fine if you have $$$ but you say your on a budget. That demands compromise. Second hand Harrys if you can find one can be tremendous bargains. Trimarans are also somewhat less sought after than cats in those bigger sizes. You can cross oceans in a 30' cat but it involves compromises.

    Cheap boats are often cheap for a reason.

    bajansailor likes this.
  8. oldmulti
    Joined: May 2019
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    oldmulti Senior Member

    Attached Files:

    ALL AT SEA likes this.
  9. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    What Guzzi said, with some explanations:
    Harryproas are designed to have a sensible layout, maximise performance, minimise cost and be easy to build and sail. There are plenty of things you can alter, but you will almost certainly lose this mix of attributes. If you can improve it, I will gladly alter the design.

    You can put whatever you like between the hulls and make the hulls above the water as wide as you like. Weight/cost and windage will go up, performance down and it will cost more time and money to build.

    I appreciate that some of the claims seem outlandish compared to other boats. I am happy to discuss them. But a blanket statement that they are bs without an explanation of why you think so makes it difficult.
    Boat speed is essentially a function of weight, sail area and length. Bottom condition, wave size, point of sail, sail shape and the size of the driver's balls also play a part. Based on the weight/sail area/length formula, 2o knots won't be difficult.

    Most boats can be single handed in steady breeze. Crew is needed to tack, gybe, reef, change headsails and cope with dramas.
    Shunting is not like tacking or gybing. It is low stress, and does not get any more stressful as the wind and waves get up. If you change your mind at any stage, you can revert to the original. It does not involve flogging sheets and sails, and the sheet loads are much reduced due to the self vanging mains. There is no getting in irons, surfing down waves or having the boom whack into the lee shrouds after a high wind gybe. You don't need speed to shunt. An 80% reef will give you steerage with none of the white knuckle stuff on an overpowered cat.
    Reefing is similar to conventional boats, except you can dump the sheets, the boat drifts and you do it at leisure. The dumped rig is always head to wind, so reefing, lowering and raising the main is easy. The same technique applies during dramas.
    Most cruising cat sailors reef at night or in squally conditions. On a Harryproa you carry full sail. If a squall hits, dump the sheet and the boat will sit while you reef, shelter below until it passes or prepare the drogue or parachute. It is a far more relaxed approach to sailing, and gives higher daily averages.
    Anchor lifting on a cat is often a circus in a blow and difficult/impossible under sail. Crew on the bow yelling and gesticulating, helmsman playing with the throttle, sails flogging. On the Harry it is all done using the sheet winches, adjacent to the helm with the sails 9m/30' away.

    Maintenance of the boat is less than most cats. Less surface area, shallow draft, no rigging, no internal motors, no skin fittings, no holes below the waterline for daggers or rudders, 2 winches, minimal deck gear and no extras.

    8 people living on a 50' cat for more than a fortnight will lead to mayhem. Harryproas sleep 2 adults in a queen size double with ensuite toilet and shower, with a spare for guests, plus 2 or 4 bunks and a bathroom in the lee hull. Randoms can sleep on the salon seats. There is dining table space for 12, plus 6 more if they use folding chairs. And seating for 30 outside, adjacent to the saloon, under a shade if required.

    Buying second hand will be cheaper than building, but "offshore, as fast as possible, with as much space and comfort as possible, with utility and comfort" and doing it safely will put it in the million plus range, and require endless maintenance.
    Building a Harry is easier than a cat. Less material, less fitout and far easier technique. The cost and time effective way is to hire a shed, buy the materials and employ labour as required. You and the family help when you can, learn from the experts and when launched you will know everything that is in your boat, and be on first name terms with the guy who sold you the non working electronics. This approach saves you the profit margin, materials mark up, office and advertising expenses, warranty allowance and contingency money that a pro builder includes in his costs.

    Please keep us informed on the progress of the Opus. It is an enthralling process, should be a lot of fun for you and educational for all concerned. Anything I can help with (doesn't have to be Harryproa related), please ask.

    Thanks for the compliments.

    the Kelsall proa was built in Peru for Seabatical Charter Co. Contact Ballotta for costs and a sailing report. Ask them for a quote on a C60 while you are talking. The Kelsall dropped it's rig shortly after launch and afaik is still for sale.

    bajansailor likes this.
  10. member 76956

    member 76956 Previous Member

    Hi Mr. Denney

    I didn't expect you to visit my humble little thread. We are all honored.

    One thing I wanted to ask; but, felt it a bit too trivial, was about some photos from different angles for model building, strictly kitchen-table stuff, or maybe for the lake. Cut some sticks on the table-saw, then glue them up. That sort of thing.

    I'm kind-of wanting to flesh-out Opus in solid 3D (wood), with different options. You know, paint it up, take some photos, and start getting feedback, in terms of what will work and what definitely won't.

  11. member 76956

    member 76956 Previous Member

    Ooh Pretty!

    Thanks for the photos. This does capture some of what I want to do. Personally, I'd like to keep the sailing-rig, on one side, like the Harrys; but, the larger accommodation is definitely moving in the right direction.

    I'm sure I want the aircraft-carrier LST fit-out, to give the vessel the ability to carry vehicles, pallets, light-weight containers, etc.
    I might even categorize the vessel "type" as an LSCHP (Landing Ship Cargo - Harry Proa).

    Please humor me, it's a paper-battleship. I'm sure I'll find a practical design in their somewhere.

    Thanks for the reply
  12. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Seem to be missing the trade off aspect of boats.

    Small, inexpensive and fast is not going to be great accomodation.

    Great accomodation and fast is going to be long and not cheap.

    All boats have tradeoffs. Once you appreciate this fact, you budget money and time to build.

    Then you determine the boat.

    If you start off with the fanciful notion of any boat; you are just doing mental gymnastics which is the polite way to say it.
    bajansailor likes this.
  13. jamez
    Joined: Feb 2007
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    jamez Senior Member

  14. member 76956

    member 76956 Previous Member

    Thanks for the Notification.

    It's a nice boat and the price is good. If I were purchasing today, I would definitely consider it.

    Right now, I'm still traveling and looking for a place, close to the water, where I can afford to rent a shed, for a build, if I go that route. I have a few places in mind; but, a purchase is still 12 months away. Good find though!

  15. member 76956

    member 76956 Previous Member

    I've thought about this a little more; and, while the comments I think you're referring to seemed harmless to me and weren't intended to be disparaging, they can still have an affect, because even tech-support forums are globally indexed and can sometimes have great influence depending on what's being discussed and how.

    I tend to think of myself as having little influence; but, modern social media algorithms have made that perception out of date.

    If I owe you an apology you have it.
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