My Riva Aquarama Plans

Discussion in 'Boat Design' started by classiclines, Nov 14, 2004.

  1. Pericles
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    Pericles Senior Member

    Last Xmas, I was drawn into a model shop by a beautifully crafted 40" Riva looking speed boat. Built in Vietnam, every frame and plank had been faithfully recreated and lacking only the mechanic and electronics, this boat was a bargain at £100 (or $200).

    If one were to take the model apart and use the model frames to create full size frames suitable to construct a full size boat, would the builders of the model have any intellectual property rights in respect of their shape of boat?

    A copy of almost anything is just that and criminal charges are only likely if the copy is presented as the real McCoy. Look at all the fake snake Cobra kit cars out there?

    It is also straight forward to create a craft without frames, but by the Stitch & Glue method and for it to be a dead ringer for a classic looking Riva. If such a craft were propelled by a more recent form of propulsion, http://www.yellowfin.com/VSDTechnology.asp
    then only the shape in the air pays homage to the original. One could almost claim that if Carlos Riva were building his boats in 2007, the S & G boat could even be his latest design of a Riva.

    Anyway, it's all moot, because Cudashark is, to all appearances, building a right little cracker of a boat. Well done!

    For those who would appreciate the style without the effort, try Glen-L. http://www.boatdesigns.com/products.asp?dept=778

    http://www.boatdesigns.com/products.asp?dept=252

    http://www.boatdesigns.com/products.asp?dept=242

    Regards,

    Pericles
     
  2. CaptScot
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    CaptScot Junior Member

    Hi, Since I've been a lawyer and now switching gears studying to become a naval architect; a passion and talent I should have utilized years ago I can comment here. There are patents and design patents. Patents for inventions are difficult for someone to make a close copy of without there still being a justified patent infringement. With a design patent, easy to obtain and though an architect doesn't seek a design patent for his drawing, by analogy has the same standard for infrigment or not. One's own design of anything even a logo in unique, therefore the smallest change to a design makes it a totally new creation. An architect or yacht designer can study a set of plans like Riva, redesign a new set of plans of a boat that looks like a Riva or very similiar and the new plans a rightfully his own. The designer could even say "inspired by the designs of Carlos Riva". Music, cars, boats similiar copies are designed every day.

    I like Cudashark's workmanship. Those frames look like they have a lap joint instead of the usual plywood gusset. Nice work! Cheers, Scott
     
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  3. cudashark
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    cudashark Senior Member

    Thanks CaptScot,

    Good eye.

    I'm not thrilled with plywood gussets especially when the wood you attach them to has a tendency to warp as they are cut, so for me their is too much movement in the wood.

    To stop this, I build a sandwich of material before I cut them out which minimizes any warping.

    The fabrication of the ribs are in quarter Sawn Honduran Mahogany. They are .80 " halves epoxied together. The butt Joints are fingered. The wood grain at the keel, chine, sheer and the gun wall are laminated at right angles and the wood grain along the ribs are parallel.

    Ray
     

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  4. Pericles
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

  5. cudashark
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    cudashark Senior Member

    Thanks Pericles,

    When building cold molded hulls, ( veneers over batten and stations's), are the veneers attached only to the battens?

    If so why.

    If not is their any problem attaching the veneers to both the battens and stations's?

    Thanks

    Ray
     

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  6. Pericles
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

    Cold moulding

    Cudashark,

    You mentioned "stations" in your post. On my side of the Atlantic, "stations" signify the numbered position of each frame or athwartships bulkhead as set up on a jig or cradle or strongback.

    From your photo, I shall assume the beautifully constructed frames that I can see on the strongback will be integral with the hull and that the battens will be stapled and epoxied to them. Then two layers of mahogany veneers are stapled and epoxied diagonally and then the final layer of veneer stapled and epoxied lengthways. As I have absolute faith in the strength of epoxy, I would remove every last staple because as far as I am concerned, they are used only to correctly locate the veneers on the hull until the epoxy hardens.

    To ease the task of staple removal I would use lengths of packing case binder under the staples, so as to pop them out. Staples remaining will stain and print through, no question and probably tear up your fairing abrasives as well.

    You asked if there are situations where the veneers are attached only to the battens and why? This would imply that the battens are only draped over the frames to create the shape of the hull and not permanently fixed to the frames. In which case, after the epoxy is cured, the frames are removed and the inside of the monocoque hull is smooth and free of obstructions and so much easier to glass.

    In fact, that is the method I shall employ, with a few minor modifications. The stations on the strongback where all the athwartships bulkheads are located will have the items constructed in BS 1088 Meranti. All other stations will used ordinary ply or MDF and are reusable. The battens you plan to use are replaced by 4mm BS 1088 Okume cut to shape as panels in the Stitch & Glue manner. This type of construction enables me to wire the panels together and adjust their locations to one another, so as to create the true hull shape over the moulds and bulkheads firmly secured on the strongback. The permanent bulkhead positions are marked inside the hull with pencil.Once tabbed, the wires are removed and the external fillets are completed and smoothed. The hull remains on the strongback and now the extra layers of BS 1088 Okume are epoxied and stapled in place to build up the hull to the design dimensions.

    I should mention that whilst cutting out the 4 mm panels, the 6 mm panels for cold moulding are cut at the same time, slightly oversize as you would expect, then drilled with dozens of holes to eliminate air pockets when being stapled to the hull. The epoxy that oozes through these holes will act as mechanical fasteners, when cured. Over areas where 6 mm sheets will not conform, cut strips and bond in place.

    In this manner, I can build the hull to match the storage and working conditions. Extra thickness on bow and hull bottom? Do it now, not later.:D

    To sum up, there are no problems in bonding frames, battens and veneers together. A very strong boat will be the result, but damage repair will be more expensive, because there are frames, battens and veneers to consider. The way I plan to do it simplifies and speeds construction as well as giving me the opportunity to build more than one boat, as the frames/moulds are not in the first boat.

    Pericles
     
  7. paladinsfo
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    paladinsfo Junior Member

    Riva thread

    While on assignment to Saudi Arabia I was stationed near Dammam. On the beach slowly rotting was an Aquarama, all the metal/instruments had been stripped and it was about to be dissassembled for firewood. I bought the wreck for $50 U.S. and for the next 3-4 months slowly disassembled the hull, frame etc making drawings. When I returned to the U.S. I had hired a young man to do some CAD work for me. In between his regular job we committed all my drawings to CAD and carefully faired the hull....and my intention was to build as close a replica as possible. Project was put on hold because of a heart attack. I do think it would be a neat project, especially with a pair of 428 ford engines like I had in my Cobra. Although I would not produce the boat with a Riva name on it for resale, I think it would be neat to run around Annapolis and south in it for fun and giggles.
     
  8. Pericles
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    Pericles Senior Member

  9. paladinsfo
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    paladinsfo Junior Member

    Thanks...still kicking......
    Riva used similar techniques, much of the boats were done with 12-18 mm plywood, and doubled and triple layered as necessary to get the required strength and stability of material. My intent was to build it as per original Riva framing etc, then strip plank with tongue and groove cedar, with a final layer on the outside of 1/4 inch mahogany veneers. It would be as light, or more so than the original, and a stronger hull, easier to construct, and be able to better withstand the pounding and vibration of the horsepower.
     
  10. Tad
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    Tad Boat Designer

    Hummm.......just noticed the activity on this thread, I guess the email notices are a bit spotty.

    Above I pleaded with folks to hire someone who knows what they are about before building a high-speed boat. Apparently Cuda went ahead anyway.

    Engineering a high-speed hull is not rocket science, nor is engineering a high-speed wood hull that difficult, but there are some basic principals that apply.

    By far the largest part of the loads imposed on the structure will derive from the speed of the vessel through (and over) the water. Momentary impact (point) loads on the hull bottom are also dependent on sea state, deadrise angle, and longitudinal position along the hull. A 25 LWL boat traveling at 30 knots might see a bottom pressure load of 25 psi, the same boat at 60 knots might see 54 psi. That's 8000 lbs on a square foot of bottom.

    To design the structure you must be able to predict the highest speed the vessel will achieve. To predict the speed you must know the weight and power of the boat.

    There are two main elements in any hull structure, the skin which keeps the water out, and the supporting structure (stiffeners). The stiffener layout takes various forms, all transverse, all longitudinal, or a mix of transverse and longitudinal. The spacing of the stiffeners divides the skin into small sections called panels. The location, geometry, and area of these panels determines the load (which may be) imposed on them, and thus the makeup of the skin.

    I've found that a stiffener system composed of transverse plywood bulkheads (which become interior structure) supporting deep longitudinal stringers works well to support an all diagonal cold-molded skin in a modern high-speed structure. The longitudinals are usually a mix of solid laminated timbers and plywood webs with top and bottom flanges of solid timber. Often we cut lightening holes in the bulkheads and in the longitudinals, both to reduce weight and to aid air flow through the hull.

    Bottom planking is set at about 30 degrees off centerline and in four opposed and alternating layers. Topside planking is also in four (thinner as topside loads are smaller) layers at about 45 degrees to vertical. There are two or three times more stringers in the bottom than in the topsides.

    On structural wood joints.
    Half-laps are not very good because you only have half the thickness of the member running continuous across the joint. Thus for equal strength you need a member twice as thick as the load requires. In a high-speed vessel weight is everything and stiffeners twice the size required should not be done. This is why plywood gussets are a good (abet ugly) solution, they double the material running across the joint just in that required area and add no extra weight where not needed.

    Typical finger joints are not structurally adequate, the bond area is far too small. For an epoxy bond that equals the strength of the timber (plus a safety factor) a minimum scarf joint of 8:1 slope is required. So a scarf in a 1" by 2" will be a minimum of 8" long and have a bond area of at least 16 square inches. Finger joints can work, but they must be far deeper than usually seen in household joinery. The Gougeon's have done considerable research into this as they used finger joints in wind-turbine blades. There is a paper available from them on the subject, and it may also be covered in the newest edition of their book, The Gougeon Brothers on Boat Construction.

    All the best, Tad
     
  11. paladinsfo
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    paladinsfo Junior Member

    Thanks for your input Tad......Riva did a good job at what they did.....and their construction methodolgy was actually on the light side if one uses Dave Gerr's scantlings as a guide. I had developed a similar set of guidlines while living in the P.I. and Thailand...and applied them to hulls using about 600 hp in 21-23 foot boats.....I have never had one break.
     
  12. CKohler28
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    CKohler28 New Member

    bombigher design

    Hi Tad, sorry to thread here, but your comment was too old. Here I go: could you give some more precise information about your criticism about Bombigher designs? More than 200 boats built and beeing sailed. What is technically wrong with these designs in your opinion? I would very much appreciate your technical and detailed ideas views because I´m considering building an 18m schooner. Thank you!!
     
  13. Tad
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    Tad Boat Designer

    CKohler,

    I'd be happy to respond either privatly via email or in a new thread. Drop me an email at tadroberts@shaw.ca with a link to a new thread or your email address as it is blocked in your profile.

    Tad
     
  14. cudashark
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    cudashark Senior Member

    Hi Guy's

    My scantlings are sound and have taken in consideration the weight and speed of the vessel. The layup will be four ply of 1/4 inch mahogany with the center two plys on a diagonal. The overall "dry weight" of this 33' craft is 5800 lbs. I have weighed each component so far and have calculated the sq ft weight of the cold molded layup. The "ribs" are twice as thick as they are required to be and seeing as the hull will be cold molded as a single unit the boat will be plenty stiff.



    More pics to come...

    Ray

    PS Merry Christmas!
     

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  15. cudashark
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    cudashark Senior Member

    Hi Tad,

    With regard to your observation and comment on my ribs you are looking at only one half of a two layered lamination which overlaps at the sheer, chine across grains.

    The scantlings call for a single piece of wood .78 inches thick X 1.64 wide with gussets.

    Those ribs are 1.58 inches thick and 3 inches wide.

    They are a composit of two layers at cross grains.

    They are plenty strong....

    Ray
     

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