ST21 'Skinnydip' build, and boating adventures, Noosa, Australia

[glossieblack]

Thanks for the technical tips blueflood, topwater and JM.

Jacques, the smooth but pronounced twisting in the tunnel sides and ceiling is impressive. Not sure how you figured it out! As per your design specification, will be installing a 20 hp @ 3000 rpm Kubota based diesel, a 1:1 F-N-R box, and a 10 x 10 Michigan Wheel prop. Will be interesting to see how she performs.

As Peter-C notes, while it's a pretty wild looking hull, the wild parts are mostly underwater. As a workboat that will be stopping an starting all the time, she'll run skinnier than just about any other frequently stopping-starting boat. Wild functionality perhaps?

[topwater]

What and where did you get your 1.1 transmission ? I know other people had a hard time finding a 1.1 .

[glossieblack]

The box is coming from Koysan Marine in Turkey. Its model A-1 mechanical box is available in a number of ratios including 1:1.
WM Diesel, an Australian company that marinises Kubota diesel engines and exports globally, has used Koysan components previously, and will be building this engine with the Koysan 1:1 box. How's progress on your build?

[jacquesmm]

Good news about the transmission. Koysan did not reply to our requests, tell them that other builders are interested in the gear box, they can contact me.

[CaptainAB]

An ST21 workboat. Perfect. I plan to put mine through lots of abuse. I'm interested to see how you beef up yours to handle oyster chafing, etc.. Does she have a name yet?

No Name yet JA. Oyster chafing? Looking forward to it - there are no oysters at the moment, hence our project! The boat will be moored in the Noosa River just about full time, and will be used by a variety of people who will not want to muck around with rain covers etc. So the finishes will need to be from the hard knocks school of workboats, with a self bailing cockpit and no leaky sole inspection hatches a must.

Hi Guys,

Had you considered a layer of Kevlar bi-axial cloth on the bottom? It's not as brittle as Carbon Fibre and its abrasion resistance is extraordinary. We've used it on a couple of Murray River boats which scrape the bottom on a regular basis and it seems really good.

CaptainAB

[CaptainAB]

For comparison purposes, this is an Atkin's Tunnel Stern under construction. This is his "River Belle" design from 1943.

It is 36' long and not really designed for plywood, but it actually worked very well. The bottom is 25mm thick and up to the chines, 20mm (two layers of plywood each). So, it's amazing the bends you make in plywood and get away with !! So, take heart guys!!

Keep posting.

CaptainAB

[JoshuaAhab]

Hi Captain AB,

Is that you, "Rhapsody In Glue"?

I haven't given too much thought to my hull protection at this stage. I am interested in the experts on this forum comparing your suggestion to graphite/epoxy mixtures, aluminum powders, etc..

[jacquesmm]

The River Belle is a much larger boat and a different type of "tunnel".
If you build,one, post pictures etc.

Kevlar is difficult to use: it is hard to cut and floats in the resin. You must vacuum bag or infuse. I prefer to use an extra layer of glass on the keel shoe and coat with graphite in resin.

[glossieblack]

Good news about the transmission. Koysan did not reply to our requests, tell them that other builders are interested in the gear box, they can contact me.

Koysan are extremely frustrating to deal with. About a year ago WM Diesel and I received answers from them after many email attempts and follow-up phone calls. They've now gone silent again, so now that we want to import one, it's a case of 'if at first you don't succeed, .....'.

Thanks for making contact Captain AB. River Belle is a big project. Do you know if anybody has completed an Atkins tunnel stern boat in Australia?

[JoshuaAhab]

Jacques,

Captain AB has a very thorough website detailing has build:

http://rhapsodyinglue.com/index.html

Apologies to Captain AB if I overstepped any boundaries in posting this info.