This dinghy design competition has been most interesting and has everyone looking for the perfect dinghy.

We all know that there is no such thing as the answer is, “Horses for courses”. Most situations that require a dinghy will probably want a dinghy somewhat different from the one available. This would seem to mean that the search on the forum is for the best all round compromise.

On one hand you start to pity the judges when they are confronted with the wide range of views expressed by the readers, but those who presented the competition were very wise in the way that they did. Not only did they get the readership exercising their grey cells, but they also made it easy for the judges to make their selections. Good exam technique requires the student to answer the question asked, and not the one that the student thinks should be asked. This means that the person marking the answers simply has to be happy that the answers tick as many of the points asked for in the question as possible.

By suggesting 9 characteristics in the competition rules the judges should not feel overloaded with information from the readership, but be able to see if a design fulfils the requirements asked for.

No doubt the search for the prefect dinghy will continue into the future.

Cheeers, Slieve.

Anonymous wrote:

I think you're talking yourself into the job of judging, Graeme! The only way to do that job properly is to build and test them all in the water, even if at model size as you're doing.

A side-by-side test would certainly be informative, but at small model scale it can't tell you much. It's too bad the JRA doesn't have a big boat-shed full of money that can be converted into full-sized copies of each boat. Then you could have a regatta, maybe switching crews a few times. I'd want to see each boat get knocked over once to see how easily they can be righted, enable self-rescue, and gotten under way again. All the dynamic stuff you can't learn from a hand-sized model in a bathtub.

I think you're talking yourself into the job of judging, Graeme! The only way to do that job properly is to build and test them all in the water, even if at model size as you're doing.

Yes David W I think you are right, and its one more of the features that I am learning to appreciate in this design. The bow is really a continuation of the bottom, sweeping up, no doubt contributing to those powerful fore quarters, and maybe deceiving the water that it is not a transom at all.

At first the whole thing looked ugly to me, but its appeal growing. Also at first I did not think the hull looked very junk-like (still don't) - but realised later that many of the junks recorded by Worcester do have this square bow transom, raked forward.

Thanks David.

I would be reasonably confident about planking the bow. When I built Havoc I did two skins, diagonal planking – but when it came to the bow, some of the diagonal planks had to be tapered to follow the cone surface around – and in that region, the second skin had to go on, almost on the same angle – the curve was too great to bend around it. In that part of the bow it had to be single diagonal (approximately radial) but doubled up, if you get what I mean - not terribly satisfactory.

On the scow I am currently building I wanted to use plywood, but there was no way it would go round that curve – and I wasn’t confident I could do it in two skins and not get voids. In the end I did it in one skin, full thickness (15mm) by making saw cuts in the outside surface of the ply, approximately along the radial lines of that cone sector. It turned out to be simple and easy. The saw cuts opened up a little. I filled them with thickened epoxy and the result looked good (looked like diagonal planking) – I was sorry to cover it with sheathing.

On the inside the curved surface is smooth and continuous, which is what I wanted. I fitted extra framing to it afterwards, although that part of the hull is very strong.

No mould is necessary, the only difficult part is lofting the panel, which I did not have the drafting ability to do. I made a model, and made the panel with cardboard to begin with, trimming with scissors until it fitted. Then, on the real thing, I fitted a 5mm panel made from cheap plywood, which I then used as a pattern for the 15mm ply. It all proved in the end to be very simple to do, and very strong, I think.

On a dinghy, I would do the bow part the same way (radial saw cuts). with 5mm ply, and leave it frameless. 

I am referring here to just that part of the bow which fans out from the fore foot, to reach that upswept fore part of the chine. The rest of the hull is either flat, or simple roll and easy to do with plywood.

The bottom and bow, well curved and "triangulated", would need no framing for a dinghy, I think. However, the sides would be flat and flimsy and I think your advice regarding stringer is a good idea, and would be simple. As for the gunnel - it also might call for some stiffening - even a narrow side deck perhaps?

 I take your point regarding beam. On that drawing I actually copied the beam (and the run) of Sibling Tender, and maybe it could even be reduced a little.

Arne - thanks too.

I like the pram bow for a small dinghy, better than the "pointy" - and I think I agree with you, except that the NZScow bow doesn't really fit into either category. The first working scows in New Zealand had transom bows, but with the short chop which is so common on our NE Coast, the model very quickly evolved into that bluff, semi-pointed bow which seems to be a compromise between sharp and square. I just thought it might be fun to try it on a dinghy - it does seem to me like a good compromise, retaining a lot of power and buoyancy at the bow, yet maybe handling a chop just a little better than a pram. It still tramples over the waves rather than cutting through them - but maybe does it with a little less fuss. I don't know, I just thought it might be worth to try but I am not interested in something as extreme as a Bolger Brick.

And thanks for suggesting to David about the measuring stick. I don't have good software here and spent a couple of hours this afternoon trial-and-error trying to scale people's drawings up or down so they come out on an A4 sheet as 1:10 scale. If they all had measuring sticks it would be a sight easier! If I make any more models, I want to make them 1:5 and use that super thin plywood I have a stack of - so it still means a trip to the print shop to get everything doubled and onto A3 then paste them onto the plywood. (1:10 cardboard is no good for my clumsy fingers). I made the KISS model that way - but did not need to do any lofting for that, and none of the others will be as easy to assemble as KISS. I wish I had time, it would be rather fun to make more of these models.

PS I can't imagine how to strike diagonals onto a NZScow hull - anyway, I suspect this type of hull follows its own set of rules - I do know that the type can sail quite well, similar to any of the old workboat types.

Edit - a diagonal on the bow section would be interesting. The waterlines are surprisingly hollow. I don't know how to do a diagonal.