Atkin tunnel revisited

[PAR]

Many of the Atkins' designs are not available on their web site. Most of these are the customs and limited productions. NamikI (or Namika, I can never remember which) was the last of four from the same builder and converted for yacht use while constructed, with plans from John, which I've seen.

In fact very few of the larger box keels are shown and only a couple of the larger tunnel sterns and none of John's work in larger sizes for these hull types.

Fred, she takes to ground easily (quickly discovered when last on the Saint Johns river) and if you don't have a full head of steam boiling, you just back right off. She can be "parked" for a night's rest in the weeds of a nice cove, then backed out and the cruise continued in the morning.

From a "lines" point of view, her beam, especially aft is carried well into the ends (Namiki is double ended), with a relatively fine entry and substantial flare in the forward sections. The box is dead bang flat bottomed and level with the LWL and shows a slight amount of deadrise along its sides. There is a slight hook along the very aft portion of the rabbit.

[EStaggs]

I believe Pat Atkin still retains all of the plans and lines of the entire body of work, and can be reached via the website. I know she has been able to produce obscure plans in the past to those who were researching the boats.

E

[Pericles]

Via Panbo http://www.panbo.com/ I linked to Maine Catamarans. If you scroll down to 15th October 2006 update at http://www.mecat.com/indexpower.htm P-45 updates, there is a very interesting model hull that relates to the subject of this thread. The whole website is full of innovation and well worth the time.

Pericles

[TollyWally]

Very interesting site , indeed well worth the time spent visiting. I was impressed with the slippery fiberglass hull shapes. I wonder what Atkin might have created with 5 axis milling machines slicing great chunks of foam into fiberglass toolings.

[Pericles]

From http://boatdesign.net/forums/showthr...098#post179098

The Wanganui Riverboats had tunnel hulls with thin, long twin rudders mounted either side of the tunnel. There are pictures of this shallow draft arrangements about 2/3s down the page. The Wairua Story.

http://www.uniquelynz.com/whanganui.htm

I was in Ranana (means London in Maori) for the summer holidays and that's why I noticed the rudders.

"After many hard years of service, the SS/MV Wakapai ran aground on rapids near Ranana at the end of January 1951 and although holed, was salvaged and taken to Pipiriki. The old vessel was later taken down to Wanganui where it was stripped of anything useful and laid up on the slipway. A few months on, the Wakapai was sunk beside the Wairere at the foot of Quick Avenue to protect the riverbank from erosion."

http://www.riverboatsnz.com/Wakapai.html

Pericles

[CaptainAB]

How fast is fast enough ?

I have ready access to 1,500+ miles of shallow slow moving river, which deserves to be cruised gently and enjoyed.

Has anyone any thoughts about Atkin's tunnel designs at 5-6 mph instead of the usual 10-20 ?

Alan

[Pericles]

A small catamaran might do as well. It should give more stability. Twin skegs will protect the propeller on a monohull.

Mike Storer has a design you might like. http://www.duckworksbbs.com/plans/storer/tc35/index.htm

Also Mark Van Abbema.
http://www.duckworksbbs.com/plans/markv/index.htm

Commonsense Boats.
http://www.common-sense-boats.com/idaho.htm
http://www.common-sense-boats.com/sea_dragon.htm


http://www.duckworksmagazine.com/r/plansindex.htm

Pericles

[kengrome]

Has anyone any thoughts about Atkin's tunnel designs at 5-6 mph instead of the usual 10-20 ?

Alan, These boats are reported to handle fine at slower speeds. It's when they are pushed faster than their design speeds that they begin to lose it. I would want one for its shallow draft, upright beachability, seakindliness, and the *ability* to go 15-20 mph if I felt like it -- even though I probably wouldn't go that fast if I were living aboard and cruising on a leisurely basis without a deadline.

[FAST FRED]

Has anyone any thoughts about Atkin's tunnel designs at 5-6 mph instead of the usual 10-20 ?

Like most displacement boats a SL of about 1 should give great fuel milage.

The ability to take the ground , jump over the side into thigh deep water and push the boat off should be very use able .

In our usual very crowded cruising grounds , the ability to anchor just off the beach , and walk ashore , rather than dink a 1/2 mile should also be grand.

FF

[Pericles]

Here is more information about tunnel hulls.

"The operation of a tunnel boat is slightly different to other boats as the propeller is only half in the water when the boat is stationary and the water is only initially picked up and fills the tunnel when the throttle is opened well up - you hear the engine speed up then the note deepen and the revs drop as the tunnel fills and a powerful jet of water emerges from the back between the twin rudders, after that the tunnel remains filled down to tick-over. Reverse has to be done equally carefully we are told as too long in neutral allows the tunnel to empty and a burst forward is needed to fill it again before reverse become effective. It must have been interesting in the days when she was driven by steam." http://www.uniquelynz.com/whanganui.htm

MV Ohura had twin tunnels with two screws on each propeller shaft. In 1940, she capsized with the loss of three men. Below is a photograph showing her twin tunnels from http://www.riverboatsnz.com/Ohura.html

[CaptainAB]

This is not an Atkin design and I suspect it is a good example of what NOT to do.

The boat has apparently always had problems steering and going astern. In the original design the rudder on full lock would close of the tunnel- terrific! This photo was taken last week and shows the third attempt to try to get the boat to steer by fitting a new larger rudder and different shaped nozzle.

The boat is 40ft fibreglass and relatively modern, but still looks pretty basic compared with what Atkin was designing more than 60 years ago. It will be interesting to see how it performs now.

[Pericles]

Captain AB,

The tunnel you have shown is too short and too shallow. Neither fish, fowl, nor good red herring. I hope it's not your boat.

http://www.riverboatsnz.com/

The Wanganui boats were built at the beginning of the 20th century in England and worked in some cases, for 50 years. When the vessels were stopped, the propellers were only half immersed in water and thus fully protected from grounding. The twin rudders directed the propeller wash, akin to a water jet. The Hatrick boats only became uncompetitive when the Wanganui River Road was built in 1935. They'd make great narrowboats for English canals.

http://en.wikipedia.org/wiki/Narrowboat

Renn Tolman's Seabright skiff is coming along.

http://www.fishyfish.com/boards/inde...e83&topic=75.0

Regards,

Pericles

[CaptainAB]

No, it's not my boat. I just happened to see it on the slip where I work - I'm building a "River Belle". The tunnel starts at the Stem Post - more or less.....