Thank you , all, for the suggestions and advice. I am working on the cockpit coamings at the moment, which gives me time to consider the options being suggested. Clearly, as the saying goes, there are more than one way to skin a cat. (in this case, an ECO 6 cat :-) ) I will update you once I have something to report.

Bernard, I knew Okoume was specified throughout the boat and I would much have preferred to build the boat with it. ?However I was not able to source it locally. Only one lumber yard in our province offers marine plywood, and the only type they are able to get is Meranti. Now that I have worked with Meranti and know more about its characteristics, I would consider paying the extra cost of freighting in Okoume from a distance if I were to build another boat.?

As for birch plywood, the only birch plywood available in Canada that I am familiar with is used in cabinetry and does not use waterproof glue. It is not suitable for this application.?I learned this the hard way many years ?ago .

There is a story to go along with that - it was my first boat building experience, building a Tiki 21. I used exterior grade, good-one-side Douglas Fir for the hulls and had no difficulty. In fact the boat is still in use in West Africa. The plans specified 5/8 inch marine plywood (which I could not get locally where I lived at the time) or 3/4 inch birch plywood (which I could get) for the rudders, skegs and a few other small parts. I sailed the boat 3 summers in Canada, with the boat moored in a small lake and had no problems. At the end of the third season, the boat was loaded into a container and shipped to Ghana where I was moving to build a hotel on the coast. The boat was set up on the beach where I was building and from time to time I took people out for short day charters. On the fifth time, we came in over the surf onto the beach. I quickly realized the skews and rudder had folded over on impact - they were completely water logged and delaminated. That was Canadian birch plywood!!

Hi Rod

In my blog pages for my Duo 480 I reccomended making up a shorter test panel of rudder minus the inside carbon. I used the jig that Rodney gave me from his KD650. The angle is the same. I passed the jig on to David so I assumed he used it also on his Eco 6. Rodney had closed the angle up a tiny bit after his own earlier failures. On my blog you can seee the angle of the jig panel sitting on the table of my drop saw. Further hints were: dont over fill the epoxy in the bottom. Dont screw and glue on the interior batten or coat the insides of the blades with epoxy in advance. Do them wet on wet, which retains the the original flexibility of the plywood . I definately found it helpful to make up a practise piece first. The quality of the plywood these days probably isnt the same, and also the type of ply used may also be important (as again Bernd mentioned)

cheers
Bryan

Hi Patrick

Thank you for your update. Impressive work.

Bernd

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Impressive build. Wishing you an early finish to the sanding/painting/

Thank you Bryan and Keith for your advice and encouragement.
Fran?ois Moinet

Hi Rod
Yes, the rudders can be tricky. I broke some ply, tried cutting kerfs, then figured it out as designed. So in addition to what Bernd said, I would just add to try bending the ply in the flexible direction, which matters with thin ply. Another thing you can do is to start with a slightly more acute angle when you pour the epoxy in the leading edge. (Add thin wedges to the jig). ?You might need to make the ply pieces a little wider, and you will end up sanding away a little more of the leading edge when you fair it but you can get the same shape in the end. Make a full size drawing of the rudder cross section, then draw your more acute angle for the leading edge. This should show you how much you have to round off. I ended up making three this way, one extra.?

Patrick

Hi Everyone
I just uploaded a few new pictures to the D.R. Voyager album?here. We are done fiberglassing as far as I know. I still have to sand and fair a lot, clear coat, then sand again and then we will paint. We have also done some interior work.?

Cheers
Patrick

Hi Rod

What a pity for all the work.?
Meranti is not usable for the rudders, as you know by now.?
I specify Ocume for the whole boat. Ocume is a lot more flexible and lighter, by the way.

The start V on the bow has to be as shown in the drawing. In your sketch, the left solution.
Do not fill the bow area for more than 12 mm. A bit less is no problem.
When you can not get Ocume ply., use Birch. Birch is very flexible. For sufficient strength, use one
more layer of glass cloth. On the main stringer, use on each side one layer more of UD carbon.

Success

Bernd

Recently I made my first attempt to build the rudder blades for my ECO 6, and met with a big failure. Advice, comments, suggestions are invited before I make my second attempt. The photos show what happened. The ?Meranti is very stiff, almost brittle. ?It appears to me I put too much epoxy mix in the V. The building plan diagram for the ECO 6 specifies filling to ?a line drawn at 13mm from the leading edge. The directions call for the line to be drawn at 15mm. I was aiming for the 13mm line but I expect I added too much - it was difficult to tell. It was also difficult to keep two pieces of plywood so that they meet only on the corners - i expect the join looked more like the one in the left of my rough drawing. I am not sure how significant that might be. If that is critical, perhaps someone might suggest how to achieve that.

In one photo of the end of the blade, the epoxy appears to have failed. In my impatience, I tried bending things the morning after the pour and the epoxy was set but had not fully cured. I heard a loud crack and stopped bending and left it for 48 yours before trying again. I used a combination of ratchet straps and then clamps to close the V. Even with the trailing edges completely closed, there was still a large gap between one side of the blade and th 20X20mm spacer.. I left it over night like that to see if it would close any but it would not. To see what would happen I ?applied another clamp and of course, the plywood failed.

On my next attempt I will make the line much darker, and I will use a refillable calking cartridge (which I have and didn't think to use) to place the epoxy mix more carefully. A friend suggested that the V needs be closed some but I am not convinced that is the best solution. I look forward to hearing other's experience.

Looking forward to see your progress. Are we allowed to know your name?

regards
Bryan

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Hello everyone,
New to this site, I'm starting to build a Duo 480. I live in the south of France. I am retired but still with a lot of activities and therefore little time to devote to building the boat. But the pleasure is as much in the journey as in the arrival, isn't it ? I have already built a small rowing sail and have a slightly larger boat that I sail on a large lake near Bordeaux. Alas, one is too small to really sail and the other is too big and too heavy to be easily moved. After much thought, I arrived at a catamaran project with a single sail and more classic hulls. I however stumbled on the design of the hulls. I was going to do them approximately but, luckily, I came across the Duo's photos, Brian's blog and Mika?l's video. I really liked it and decided to give it a go. I ordered the plans in the United States. I thought Bernd lived God knows where, but sa "maison" is at Maison ;-).

I'll go see him one of these days. I started tracing and first cuts. I checked the correct dimensions by making pre-assemblies before gluing and I can say that the plans are very precise. I made my cuts to the millimeter and it falls perfectly just. Well done Bernd! I am now waiting for the weather to be a little warmer to do the collages of the large parts and move on to the construction stage of the two hulls. See you soon for the rest of the construction...?

f.moinet <f.moinet@...> added the album DUO 480 : Construction of a Duo 480 in the South France

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The following photos have been uploaded to the DUO 480 album of the [email protected] group.

• 20230315_141233_resized_1.jpg
• 20230315_191010_resized_1.jpg

By: f.moinet <f.moinet@...>

My best compliments to Rod for his suberb work

Mirko,
my builder is a retired craftman near Rome, but he is full of work; this forum is viewed by a craftman in the south of Italy; look at

/g/K-designs-Multihull-Sailboats/topic/duo_900_italy_wing_mast/95750017?p=,,,20,0,0,0::recentpostdate/sticky,,,20,0,0,95750017,previd%3D1678124736354653865,nextid%3D1666784426550126674&previd=1678124736354653865&nextid=1666784426550126674

bye

beppe_rm