Catamaran for Jules

[Manie B]

Hi guys I had posted this info on another site, which will close, so I am going to tranfers all the details here. The build is progressing well and I will be able to visit the site next week and post new pics.
So just for the record and for those which may not have seen this before:

Good news - very very - good news
I have been a very busy boy lately, burning the midnight oil often. I am very pleased and honoured to be able to announce a beautifull project that i am involved in for my client, Jules. He is a very hard working chap and is working spot on accurate. He owns the factory that he is building in and has lots of machinery to help with the job. He also has experienced tradesmen available to come in and help as and when required.
I am doing all the drawings and design, and I am doing it all on CAD
We share the same ideas of what this boat should be all about. It is a bridge deck cat 8m long and will primarily be used for weekends sailing on the Vaal Dam. It is designed for marine ply and epoxy/glass construction in a basket jig similar to Mas's build. The propulsion will be two 10 hp fourstroke outboards. We are hoping to finish the build within a year.

When I did my research I knew what my client wanted and the one boat that is similar is the Kelsall 27 http://www.kelsall.com/s13p.html
I addapted the basic concept for our local conditions and the availability of local materials, all of which is problematic is South Africa.
I did the hull modelling in freeship, to establish the kind of resistance values that we wanted for a hard chine design and also to get the development co-ordinates for the hull plates. I then imported the DXF files to CAD There are obviously discrepancies that creep in but nothing that cannot be fixed with a little thickened epoxy. This picture of the layout is courtesy of Kelsall

this forum SMF doesn't like all the CAD type of formats - so I printed and scanned - much easier than trying to convert the unconvertable Bitmaps BMF DXF and all the other abc's

Anyway here are the hull lines - My sheerline is insprired by Outremer cats - gives a nice old world boat look and i think it offsets the reverse sheer of the cabin top nicely

Many bridges to cross - many problems to solve - but what the heck, if you dont go for it you wont have it.

Here is some of the numbers jargon for you guys that enjoy this kind of number crunching

Length 8.1m - Beam 4.7m - displacement loaded 3000 kgs - bridge deck clearance 400mm = inland sheltered waters
Power requirements empty hulls 0.84 x 2 watts at 6 knots - hull mass in ply 182 kg each = glassed approx 250 kg each
Initial calculations indicate that we could have the bare boat dry on the water at 1200 kg's
I have gone for 16 mm at the bottom and 12 mm on the sides, it is very heavy, but our conditions is dirty water and I wanted the 16 mm at the bottom to support mini keels, dagger boards are simply too dangerous here.

Here are the different displacement values

Jules lives about 2 hours away from me by car, so you guys will understand that it is not that easy to get there, and when I do get there we obviously have to cover as much as possible in a day. Anyway I went down Saturday early and we got stuck into a sort of training session for the day - coverring all aspects of epoxy. I set up his "laboratory" for him and we went thru the whole process of laying down really good fillets. I used the "cake decorators" plastic bag tecnique, with excellent results. Then we went thru the whole process of saturating the 750 gm tri-ax glass, and the importance of peelply and then my "invention" of putting a layer of waxed paper over to really roll the layup down flat and smooth. The end result is that once the peelply comes of with the "blush" there is ABSOLUTELY NO SANDING necessary, you can paint straight away.

Long and busy day, but very rewarding.

I did the hull modelling in freeship 3.1? and then imported the dxf files into cad where i do the rest of the design and drawing. The panels are hand lofted and hand cut from the cutting co-ordinates from freeship plate developments program. We went for 12mm sides and 16mm bottom.
So far the freeship co-ordinates have worked remarkebly well as we have seen now with the "chigger" "Jarcat" "micro" and now the 8m bridge deck cat. The panels are step joined because we have found that a step joint is easy and accurate. We usually do it half depth and then 3x board thickness wide.
These boats are all glassed inside AND out because of the murky water we sail in (tree stumps - rocks - who knows what else)
The under water shape I modelled/played with for hours/days on end and it really is as effective as a rounded hull. a BIG THANK YOU for posting that drawing - it is always very reassuring for me to see that I am on the "right track" I will go down and visit Jules soon and then post more pics - he has the second hull finished, we speak on the phone regularly. Cheers boys carry on building and boating

A proper 8:1 scarf joint is probably the strongest of all but is difficult to align
a step joint is very easy to align because you simply push the steps into each other
if you are going to glass the inside of the hull prior to any bulkheads going in and then also glass the outside of the hull a step joint is really very good

the little chigger that I built was CNC cut and all scarf joints -never again
scarf joints is a pain and getting stuff cut CNC was a job and a half, backwards and forwards to the cutters, then they dont understand this, then they dont understand that, a huge waste of time and expensive cutting to see the CNC spit a boat out in 30 minutes. Taking the meetings, discussions, travelling and other time wasting factors into consideration I can loft and cut hull panels in a couple of hours while you are stuck in traffic and drinking coffee with your CNC specialist while he is waiting for the operator to set it all up.

Lofting and drawing full size is actually enjoyable and once you are into it goes very fast
my little bosch jig saw is also amazingly fast thru marine ply

Just an update.
I am in regular contact with Jules and both hulls are almost done.
Hopefully I will be able to go and see him within the next couple of weeks.
The idea is to get the hulls side by side so that we can start final layout and planning the interior so that I can draw it on CAD
I am very blessed to be very busy at work and all my free time gets devoted to my own building of my micro. I spend sooooo much time on my build that it is a small wonder that my family still recognise me
Boatfan I have no problems sharing the data. If you are able to make head or tail of it!
Here are the co-ordinates of some of the panels. However if you want to experiment with this kind of thing you unfortunately will have to buy and learn a program like Delftship that can develop panels. Be warned it is a bitch to learn and will drive you to drink and at times suicidal - but in the end its great fun!

Hi guys, sorry that I haven't been around for a while but I am overloaded with work. Not crying, quite happy BUT my business is seriously interfering with my hobby and of course the building of the microcruiser is also suffering. Mas your boat is looking absolutely STUNNING and the good news is that I will definately be in OZ - 9.12.11 to 9.01.12 so if you are still close to the mainland / Brisbane / Great barrier reef, I will buy the beer I wanted to shoot up to Thailand to go and see the new recording studio and get to Frosty but alas no chance - no time, maybe some other time
Anyway, Jules has been working on his boat and here are some pics. The one pic is Jules inside the hull. Everything is going to plan and its looking great. I have the greatest confidence in his abilities and for a first timer he is full of enthusiasm. What obviously also helps a lot is that he owns the factory that he is building in and we all know that working in a lockup facility with that kind of SPACE and elbow room is farkin way cool dudes
So as the economy is still shrinking in Saffa at least there are these two projects still going along strongly. This small bridgedeck cat of Jules obviously has a universal appeal and the guys at the yacht club are full of praise for it. So when it gets launched Jules is going to have his hands full with many strangers coming up for a look. My micro is for the "adventurous" to say the least, but I have never been a "conformist"

[Manie B]

And here are the pics that went with it all.

[Manie B]

More old pics.

[Manie B]

The build started 29 March 2010

and I will visit the site next week to get new pics and to get the latest news

cheers

[Jeff]

Excellent!

I really enjoy following build threads and seeing projects come to life and I can't wait to see even more.

Thanks!

[Manie B]

Well - finally an update -

I got around to going down south to visit Jules
(nice lunch and beers thanks Jules)

the build is coming along fine and now he is into the painfull stages
sanding and more sanding
the hulls are fair and looking good
wont be long now and he can start on the interiors which is fun building again

enjoy

[Manie B]

Hi Guys,
I am sure many of you guys were thinking that we got "lost" somewhere along the way. We are all fine and plodding along ok.
Jules is still at it and doing a fine job.
This is a big boat AND a lot of work.
The hulls are perfectly smooth on the outside, Jules employed a professional auto guy to come in and flatten and sand. The results are simply stunning.
I went down there for the first time in many months and I am very impressed. One thing is sure - a cat of this size is HUGE
Jules is working on the interior to suit his own personal needs and I must add that he is not going overboard and thinking about Golden taps and other ridiculous ****.
The boat is strong and will be a wonderful cruiser for friends and family.
He struck a bargain and bought a full rig cheap. Mast, winches and sails. I saw the rig and it is vitually brand new. What a bargain. He also picked up a 40hp Honda fourstroke that is as good as new. Fantastic!

[Manie B]

Well I finallly had a chance to get down to Vanderbijlpark to see Jules.
He is coming along fine. An 8m cat is a bucket load of work, but he is chipping away at the block on a regular basis.
8m - (4.8m beam) is relatively short for a cat with 600mm bridge deck clearance and 1,8 headroom in the cabin but the real bonus is standing headroom in the hulls.
As a weekend cruiser she will be very comfortable and she will fullfill her intended role with style, definately a fun boat coming together nicely. Jules is building the boat to fit his own requirements and his families needs.

The factory is relatively small so the problem is I cant stand back far enough to take pics. So the pics are a little "close-up" but you get the general feel.

[boat fan]

I like it Manie.

Multies are a lot of work, there is so much surface area.

Is he using 3/8 ( 9mm ) plywood for the hull skins ?

[Manie B]

Boatfan thanks for the PM - dont know why but I cant send messages to you or reply - it says you have blocked PM's and mail.

Anyway your pics look good and I suppose you can start a thread later.

You are right when you say cats are a lot of work - and you are still going to be very busy for a long time to come with your boat

Just on the Mini - Cat 5m I donated the hulls to a friend and dont know what happend after that. It was a crazy way to discover that I really wanted a mono-mini. Glad that I got out of it at the time. Today I know that the hulls are the easy part - fitting a boat out and decking it - is a HUGE amount of work. So better be a 100% sure that you really know what you want.

And as you have seen from my blog and my YouTube channel I am having a ball cruising around our local dams. I must just advise you as well get the boat on the water so that you can motor around and have fun, mast and sails can come later.

[Manie B]

sorry forgot to answer your question
16mm bottoms
12mm sides
9mm interior

[antoniekruger]

Hi Guys,
Met Jules today at AMT - a face to the boat. Thanks for the chat. Hope to meet you soon Manie - let me get away with my Carolina and we'll have a get together. I want to look at the house-boat as a follow up. Sitting in my floating caravan appeals to me.
Thanks for the links, Manie. I'll follow up on the ply. Have you used any exterior ply in your builds, and if so, where can I find good grade exterior ply? Same guys?
Antonie

[Manie B]

small world

In South Africa we dont have the variety of products like elsewhere in the world. So most of the time we get "interior" OR "marine" ply's

The joke is that I consistently bought marine ply from Schallies much cheaper than "interior" from the regular suppliers.
The only product that stands up to water is the so-called "shutter-ply" that is usually 18mm thick. It is very poor quality but has got that black waterproof glue that is used on marine ply - I cant remember the name of that glue.

Bottomline is that for us here in Saffa - dont touch anything but marine ply - the other stuff doesn't work - we have tried many times.

[Manie B]

Oh and welcome to the Boatdesign.net family - Antonie

[Manie B]

I want to look at the house-boat as a follow up. Sitting in my floating caravan appeals to me.

I can assure you with knowing what I know today my next boat is the "River cruiser"
River / House Boat Design Exercise.
without a shadow of a doubt.
I am one of the very few guys that have done these "exploring" trips
Manie's Microcruiser

A small, light, "cabin cruiser" is THE answer for our conditions and useage here in Gauteng.