OK, then, here is your JR.
The shown sail is taken from the Johanna-style master sail with AR=1.90 (same as on Ingeborg). Two panels have been removed. When thinking through the furling and stowing process of it, I think it will take several minutes. This is well oustide the tender rig’s specs. However, if one stores the rig (and leeboard + rudder) on the mother ship, it may be useful as a rig for occasional dinghy sailing. One may even be enthusiastic enough to make the sail with six or seven panels (0.5sqm/panel).

I would make the sail properly with well thought out camber in it and using the lightest imaginable cloth. A single (‘tacking’) leeboard would provide leeway resistance  -  and may do second duty as a fish-gutting board. In case the steering oar is tiring to use, then one must bite the bullet and make a rudder.
Be my guest...

Arne

These drawings are for manual marking out and cutting from 3 sheets of 4mm plywood, and conventional framing using 20mm sq softwood. I would have to add dimensions and more details, and write down the building sequence, but the major components are there.

Alternatively, I could add the detailing necessary for CNC cut, slot together construction.

The sail is 2.4 sq m, large enough, I think. The battens are three equal lengths of 1.66m cut from a 5m tube. The mast is 2.4m long, to act as a cover ridge pole, and the yard is 1.4m, both from a 5m x 45mm dia tube. A 3-point sheet span with single part sheet, a single part halyard and the simplest possible lifts complete the rigging. Steering by oar permits sculling through the un-sailable bits.

Graeme, I know all about the impracticability of a full-on JR on an 11ft 6in dinghy. Have a look at the front cover of JRA NL 31, 1995. My dinghy Dorothy has a mast that is the same length as the boat, so that it can act as a ridge pole for the cover, and it is the work of a moment to step it in a Yorkshire Coble type of tabernacle. The sail was another matter. I used to get into awful tangles with the sheet and lifts. Then I made a mast extender - an alloy tube that slipped onto the top of the mast to ship a taller sail - and the tangles resembled the Gordian Knot. 

So, yes, the challenge is not to design a dinghy. The challenge is to design a simplified form of JR for a dinghy, be it 8ft, 12ft or 16ft, that would be practical enough to actually get used regularly, without causing undue frustration.

EDITED

 I do own that I made the statement “8' is too small to be worth putting a junk rig on” which was a value judgement I should not have made in such blunt terms. I apologise for that, because I do sincerely support and appreciate the efforts of the committee and did not mean that statement to be as negative as it sounds.

Of course you can put a junk rig on an 8’ dinghy, as we know it has been done. In fact, I am eagerly looking forward to seeing Annie’s junk-rigged tender when the competition eventually yields a winner – in which case I might be very tempted to have a go at making one too.

(By the way, evidently the committee has thought about this and is maybe on the right track, because nowhere in the criteria is there any requirement for the JRA sailing tender to be junk rigged – merely that it should be easily reefed. Annie and I both overlooked that small point, and it makes a bit of a difference).

The sponsored JRA dinghy design really ought to be junk rigged, despite the small size of the boat and the (in my opinion) impracticality of it. Annie is absolutely right in her vision of fun and frivolity arising from a few little junks buzzing around the anchorage at a junket. That, surely, must be the main goal and point of the exercise, and is surely more fun than sitting around at anchor all day, which is what I have observed most people doing at the “tall ships” I have attended in the last three years.

Therein lies the real challenge. There are plenty of simple-to-build plywood tender designs which are known to be (more or less) suitable. But no-one has yet designed a junk rig especially suitable for an 8’ dinghy. That would be a worthwhile challenge.

The real challenge is not to design the hull, but to make a variation of the junk rig which can be carried as a bundle in one hand, spar lengths stowable, able to be set up or struck in a jiffy (or at least just a minute or two) and able to deploy while actually on the water. Then we will have a tiny, practical junk-rigged tender which will be reefable and really safe to sail away in, turn envious eyes – and actually get used.

Can it be done? Yes, I think maybe it can. 

I’m in support of the JRA Tender competition - but I am still going to pursue the junket boat idea.

You can’t have too many boats…. can you?

Edit: I've just seen Arne's latest post which popped up while writing this.

Well done, I love the 5-plank configuration. Handsome and jaunty Halibut is crying out for a little centreboard and rudder, and a bit better sail plan. Back to the drawing board Arne, for 2-minute-deployable Johanna rig!

When sailing a little dinghy you have to shift your bum around a bit - sometimes from the bottom of the boat (which is the best place) to a thwart. When you get old like me, low thwarts are the best. Its a little beauty Arne.

So far, David has produced the simplest-to-build hull shape and best arrangement of buoyancy, moveable thwart, and off-centre board (one's enough I reckon) and the best looking rig, but presumably the judging committee will need to see some more details, ie the running rigging and how quickly it can be deployed.

Graeme wrote:

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 [Golden Bay] (12'9") just sneaks in. All John Welsford has to do is modify the plan to provide an offset centreboard case and removable 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.

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, Sieve, Paul etc can come up with a suitable variety.

They row beautifully.

Here's mine

I agree, too, with the idea of having two side tanks with parallel sides that are just far enough apart to fit an air mattress of the Thermarest type in between. The removable thwart that can be slid fore and aft for rowing from different positions with one, two or three aboard, or removed for camping, is perfect. Given that, you have a versatile, easily built boat for Junkets, family pottering and minimalist dinghy cruising. Spot on. Again, there's no need to reinvent the wheel over and over again. The Golden Bay, with changes to the interior, fits the brief very well.