Arne wrote:

PS: Talking of which  -  maybe you should try to pull-scull your inflatable in coracle-style?

Yes, I've tried it. It's the same problem as with a kayak paddle - there is no skeg or keel, the bottom is dead flat, so the boat rotates very easily on each stroke and I don't get much forward motion.

Maybe I could glue on a bunch of these? 

Davit Tyler wrote:

As Len hints at, you seem to be very close to reinventing the wheel, Arne. eg the Bolger Brick and Tortoise, PDR...

I think that in your S 8, you've succeeded in designing a dinghy worse than any inflatable, unless equipped with a motor large enough for planing. Add some rocker, to get the transom out of the water, and it becomes tolerable, but still not good. The one I built like this had a beam of 3ft 6in (I think), which was plenty for stability and load carrying, and permitted the use of 7ft oars that would stow inside the 7ft 9in length (important).

Yes, an inspection hatch in each tank is vital, or at least a drain plug.

Well...

how was that saying about ‘horses for courses’? My needs are very different from yours. With no currents or tidal height to speak of, and with the seabed sloping fairly steeply from the shore, we both can and should anchor quite close to it. All I need then is that my box tender will carry me and my 1-2 passengers ashore, being reasonably sure of arriving with dry butts. A dragging stern would be my least worry. For a distance of 100 meters, I could row a dead cow  -  at least in the shape of a coracle...

Arne

PS: Talking of which  -  maybe you should try to pull-scull your inflatable in coracle-style?

Buoyancy for the sailing tender

I am thinking about buoyancy tanks right now, as I am currently retrofitting fore-and-aft tank sides in a Golden Bay, and trying to decide how to do the tops. I am thinking of lift up lids – at least for the tanks which will hold buoyant things, like sleeping bag (in a waterproof bag), and inflatable mattress (I’m wondering if a loose stow, and putting a bit of air in the air mattress might be OK for one of the tanks.) Any suggestions?

I don’t much like capped over buoyancy tanks, and the little round plastic ventilation ports are often awkward if you need to inspect, or have to get in there with a sponge. I'm dealing with that right now in the little buoyancy tanks provided in the Golden Bay at the bow and stern. The for'rd one didn't have a drain hole, and it had water in it.

Still, I do think a little sailing dinghy ought to have full buoyancy, and if plywood tanks, perhaps they should have drain hole AND ventilation/inspection port.

Also, keen to see some further construction details for David's –"wuban" -  is she to be fully decked at thwart level, leaving just a foot well?.

Wuban would be nice name – as a word in Chinese it means “Dancing Partner”.

舞 伴 wǔbàn

If you want it to be “five-plank” (which I don't think is actually a word in Chinese) the characters and intonation are:  

五 板 wǔ bǎn

Without the characters, you can enjoy the ambiguity.

Anonymous wrote:

“Simplicity”, the ultimate 8-by-4 feet box tender.
(..just a little break from the Halibut..)

Now I found I needed a break from curved lines.

When David Ty. showed us his inflatable tender for sale, I thought to myself: “How bad can one make an 8-foot plywood tender and still make it row better than an inflatable?”

So I started with a clean file and drew up a box measuring 2.4 x 1.2 x 0.4m. Obviously, that thing would protest if towed at speed, so I adjusted the front panel a bit, but that was all I did. For the sake of strength and

...

Question:
Should such tanks have a sort of ventilating or should they be completely sealed off?

Arne

PS: Back to the Halibut B...

I built such a boat, when my now 36 year old son was 8. We did not add sails as it was meant to be a skimmer, add a 6hp OB and it planed much quicker and easier than any inflatable for sure. It rowed well even without very much rocker... maybe a bit hard to turn but compared to a blow-up dingy it was lighter and much easier to push through the water. It's biggest problem on a plane was if the square bow dug into a wave at all. I would imagine even off plane, this could be a problem with a sail too. Ours had three skegs that also acted as stringers. Definitely car (or in our case, truck) topable though. Look in Paysons plywood boats for the one we built and probably don't spend too much time redesigning something that is already done :)

The problem with this concept is "tender" vs "sailing dingy". Almost all inflatable dingies and RIBs are designed to plane, even if they are not designed for a motor big enough to do so. It seems to be a tender these days, it must mount a motor and sailing qualities are never thought of at all. They tend to be heavy, almost double what a wood or wood/glass boat would weigh for the same size. (our 8x4 skimmer has had 4 or 5 adults in it with no motor) As such, I do not think it takes much to make plywood boat that out performs a blow-up anything...

An atmosphere of friendly collaboration spurs me on to do better than I can do on my own, and has got me thinking about how to combine the better sailing and rowing qualities of Arne's 5-plank Halibut with the stability and practicality of my 3-plank.

So I've used the transformation tools in Freeship to make the original SibLim form into a dinghy with a bow resembling the bluff bow of the Northern China junks. The width of the flat bottom is not as great as my 3-plank, but is enough to give a flat area to stand on over the whole of the non-tanked area.

Here's my Wuban 

It's 2.335m long with 1.04m beam and a draught of 0.2m when laden to 250kg displacement, which just immerses the bottom of the transom. I can nest the components onto three sheets of 4mm or 5mm plywood. There is enough surplus plywood to make a daggerboard case, when I figure out how and where it goes. The lines drawing shows a pretty stable midship section.

Stitch, fillet and tape construction, with some locating tabs and slots in appropriate places, would be used. The building sequence would start with laying down the tank top, upside down, onto a flat surface, and assembling onto it the tank sides, stn 1 and stn 4 which would be made to slot together like a # - that would make a stiff structure ready to receive the bottom panel, then the middle panels.

It will of course be fitted with the Halibut rig in due course.