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Cash prize of 250 GBP - Dinghy Design Competition

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  • 21 Mar 2021 23:40
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    Reply # 10222130 on 10211344
    Anonymous member (Administrator)

    I put up a long-winded post advocating the Welsford "Setnet" or "Golden Bay" (same hull) but took it down again because it does not match the "1 sheet of plywood" criterion and is not really suitable as a tender.

    (The reason I put it up was because Marcus has one, I have just bought one - and there is another for sale on Trademe at the moment and I thought the third one might appeal to another JRA member in NI NZ.)


    I agree with David (and Arne) that 8' is too small to be worth putting a junk rig on, and certainly too small if the purpose is to be able to compare junk rig variants in any meaningful way. 12' would be minimum I think, but this will be too large for a tender for most people.

    I wonder if a more practical set of criteria would be not for a TENDER, but instead for a "JUNKET BOAT" - a general-purpose sailing dinghy which does not want an outboard, and which can be easily transported for those who are unable or for whom it is inconvenient at the time to travel to a junket under sail. Ideally it would be transportable on a car top (just) or with a very light trailer, and able to accommodate an air mattress/sleeping bag/canopy arrangement (just).

    These two almost contradictory criteria intersect at about 12'.

    Swapping boats and rigs at a junket, and letting bystanders have a go, would be rather fun.

    The Welsford design (12'9") just sneaks in. Here is one Marcus built many years ago:

    Here's the one he currently owns, with the old Pungy rig and an improvised leeboard.

    I haven't tried mine out with a junk rig yet, but it sails beautifully with its little western lug rig. Marcus has "cartopped" his, but I am still pondering the practicality of that, for most people. The one currently for sale has a good little trailer. I have trailed mine very easily with a light, domestic, general-purpose trailer.

    All John Welsford has to do is modify the plan to provide an offset centreboard case and removeable thwart. Marcus reckons narrow side buoyancy tanks and short centre thwart which just drops into place for rowing. The ideal for me would be a single off-centreboard case incorporated into a side buoyancy tank, with a long swinging board for sailing in shallow bays, and for variable CLR.

    We don't need a sail plan. I am sure people like David, Arne, Slieve, Paul etc can come up with a suitable variety.

    They row beautifully.

    Here's mine

    Here's the one for sale

    We could have a fleet of three straight off!

    Last modified: 22 Mar 2021 09:27 | Anonymous member (Administrator)
  • 21 Mar 2021 18:57
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    Reply # 10220966 on 10211344
    Deleted user

    That suitability for being able to be rowed, or sculled is very important. It seems that here in New Zealand almost no one rows their dinghies anymore. Admittedly inflatables now outnumber hard dinghies, and most inflatable don't row well. But I can never understand the people who have a hard dinghy which would row well, yet even at my mooring area I watch people lug the outboard from the car to the dinghy, go through the whole process of clamping it on, trying to get it started, all just to go a distance of a couple of hundred meters to their boat. They seem to go to an awful lot of trouble just to avoid a little exercise. Still, I guess it is the same as all those very good sailing yachts which motor downwind in a perfectly good breeze without even bothering to unroll the furling headsail, which is something I see very often.

    David Tyler's comments about the difficulty of finding a generic design that suits every one are very true. Maybe it should be a design which can be scaled up or down to suit the size of mothership.

    Last modified: 21 Mar 2021 19:01 | Deleted user
  • 21 Mar 2021 18:42
    Quote
    Reply # 10220902 on 10211344
    Anonymous member (Administrator)

    Designing a ‘one-size-fit-all’, ideal dinghy is outside my capability, for sure. I have drawn a couple of box-shaped dinghies between 7 and 8’, only meant for towing behind my boat, and then be able to transport two people ashore, safely. No ambitions with respect to sailing or easy rowing.

    However, yesterday Oscar entered my idea generator , with a LOA of 3.00m. This is the biggest dinghy which can be kept freely in my boat club. Now, probably inspired by David’s SibLim design (..plus Phil Bolger’s designs..), I found I would try my hand on a double-chine design. This lets one get away with a narrow waterline and still have a generous beam overall. I have mainly been dealing with the outside dimensions and displacements. Structural stuff must be dealt with later. Priority is on easy rowing with 1-2 people on board, but still with half-safe capacity for four people.

    I even drew up a sailing rig with a big rudder and bowboard providing the lateral resistance. Priority is on fast setting and furling of the rig, including lowering the mast. Since the sail is only 5.2sqm, about the same as one panel on my Ingeborg, I would not bother with using a JR here. The mast is meant to be free to revolve so that one can let the sheet go and even stream the sail straight forward. This adds safety in a strong windgust, and also lets one sail (drift) slowly downwind onto a beech.

    Obviously, there is no use in competing with a design which has not been built and tried yet, so I leave the competition to those of you who already have a few dinghies under your belt.

    Good luck!

    Arne

      

    Last modified: 21 Mar 2021 20:49 | Anonymous member (Administrator)
  • 21 Mar 2021 09:21
    Quote
    Reply # 10219562 on 10211344
    Anonymous member

    My initial thought was that this design competition is based on two entirely false premises: 

    1. That there is any such thing as a generic "ideal tender". There might be a tender that is ideal for one particular mothership, with a particular ship's complement and a particular type of cruising in mind; but change just one of those, and that tender would probably be entirely wrong. A boat the size of Weaverbird cannot entertain the thought of a hard dinghy, only an inflatable of some type will serve. FanShi is about the minimum size of boat that can carry a hard dinghy in davits, but the diminutive dinghy that suits Annie wouldn't suit two large people for use in rough exposed waters. A boat of 35ft LOA is of a size that can carry a dinghy on deck, but the size and design of that dinghy will need to be considered very carefully so as to fit the space available. And so on. One size certainly doesn't fit all.
    2. That a dinghy under 8ft LOA can carry a meaningful junk rig. Scaling down JR to that size involves compromises that make it nothing like a cruiser's rig. If the intention is trying out various forms of JR on the same basic dinghy, then the minimum size is a dinghy designed around one and a half sheets of plywood scarphed together, just under 12ft LOA, but better is two sheets of plywood scarphed together, just under 16ft LOA.
    But I don't dismiss the idea entirely. Instead, I think of it in the same terms as the initial design brief for SibLim: given a very particular set of requirements, what design will best fulfil them? So I'm imagining a dinghy for a SibLing, a sistership to FanShi, planned to have davits and a complement of two people of average build who will require a workhorse of a tender that can carry them and a reasonable payload to and fro in anchorages that may not be entirely sheltered; and occasionally, will put a simple sailing rig aboard, just for fun. Alter any of those requirements, and a different dinghy is the result. Take away the davits, for example, and the dinghy must be an inflatable, stored on the foredeck.

    Not that there is any need to reinvent the wheel: the likes of John Welsford, Paul Fisher, Joel White, Phil Bolger and Iain Oughtred, and a host of other designers both professional and amateur, have already made good designs for plywood dinghies that if laid end to end would stretch from here to infinity. 


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    Last modified: 21 Mar 2021 09:39 | Anonymous member
  • 18 Mar 2021 23:14
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    Message # 10211344
    Anonymous member (Administrator)

    Get your thinking hats on, sharpen your pencils and with poise hit the drawing board.  This competition closes on 31 April 2021. 

    See a full spec in the attached file or on General forum

    Send your designs to Mark: 

    chair@junkrigassociation.org 


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