DUDLEY DIX-Didi 40

[Sly]

Hi, this is my first post. Although i have been viewing the forums on this site for a couple months now i finally thought i would post my first post.
I just wanted to ask the members of boatdesign.net for there opinion on this particular design. I have done extensive research on Dudley's Designs, the radius chine plywood method of building that is used to build it. And i have red most of the testimonials, and builder’s websites that have built and are currently building the Didi38/40.

So what are your opinions on the model, the design itself? I’m located on the shores of Lake Ontario 15 minutes away from Toronto, Ontario, Canada. I would like to use the boat for racing at the local yacht club and eventually sail it down the east coast and across the ocean to Europe and finally stopping in the Baltic Sea.

Here is a link to the Didi 38 page on Dudley's website: http://www.dixdesign.com/38didi.htm
Thank you for your time gentleman.

Sylvester Sawala

[Murdock]

eventually sail it down the east coast and across the ocean to Europe and finally stopping in the Baltic Sea

Goin' deep out the ocean on a chined/ply hull? don't forget to carry a Bible...

[Sly]

Goin' deep out the ocean on a chined/ply hull? don't forget to carry a Bible...

Bad idea?...i guess its time to look for a new boat(haha)...but for all intensive purposes lets forget about sailing to Europe and just look at the other aspects of the design...the new question is...where would you sail it and where not? Would the design/construction materials allow you a safe trip down the east coast towards the Caribbean or even Bermuda or if you get caught in some ruff seas are you toast?

[DGreenwood]

#1 Chined plywood hulls have been sailed thousands of miles as safely as any other type.
#2 It is really not chined, it is radius chined which is to say it is partly developable and partly not. The part that is not is essentially cold molded...actually so is the rest of it because the flat or developable part of the skin is done in two layers of thinner ply.
#3 Dudley sailed the boat across the South Atlantic, I think maybe , more than once.
#4 Dudley is a straightforward enough fellow to set you right on what you need to do to build the boat for your purposes. Ask him.

The addition of an epoxy and glass skin toughens and strengthens the hull. This can be enchanced with more glass or aramids to really toughen it.
I am a very cautious seaman with many miles and I would not hesitate t use a properly built version of the boat to do what you suggest.

[Sly]

DGreenwood...i appriciate your reply.

Thank you.

[DGreenwood]

No problem...As I said, just e-mail or call Dudley. He is approachable and very straightforward. I don't think you will get any BS about what the boat is or what it can do.

[Chris Ostlind]

I'm just curious about Murdock's cryptic post.

What, specifically, do you have against chine ply hulls that you chose to omit from the post? It would be helpful if you can include researchable references, personal accounts, precise descriptions... I think you can see what I'm after, here.

Please fill in the blanks. I'd like to hear your full set of reasons.

[Crag Cay]

Why would more information about chined plywood hulls thelp this guy's research into the Dix38. It's radius chined with the round bit being effectively cold molded.

Dudley does a couple of scantling recommendations for both cruising and racing versions. Dudley will let you know exactly what the trade off are in terms of weight vrs longeveity, etc. He is at least one designer that has 'been there and done that'.

[Chris Ostlind]

Because Dix isn't the only guy doing plywood boats or chined hull vessels of any type, be they hard, radius or multi and I want to know what supports Murdock's comments. Is his beef with the structure, the material or what, specifically? He may or may not know something that would be of value to my understanding.

[Guillermo]

Here some numbers for DIDI 38 (I've worked with info at Dudley's pages and done some approximations from drawings and charts there. I asume a downflooding angle of 110º, which is probably lower than the real thing. So calculated numbers are not precise, but approximate)

Lh = 11,5 m
Lwl = 10,33 m
Bmax = 3,4 m
Bwl = 3,06 m
Draught = 2,25 m (deep keel version)
HD = 0,33 m
Disp = 4750 kg (assumed as being RCD's Mmsc)
Ballast = 2000 kg
Sail area = 66,67 m2
Power = 25 HP
Heeling Arm = 7,300 m (guess)
Wetted Surface = 27,200 m2

Length/Beam Ratio L/B = 3,21
Ballast/Disp Ratio W/Disp = 0,42
Displacement/Length Ratio D/L = 120,19
Sail Area/Disp. Ratio SA/D = 23,98
Sail Area/Wetted surface SA/WS = 2,45
Power/ Disp. Ratio HP/D = 2,39 HP/ton
Hull speed HSPD = 7,8 Kn
Potential Maximum Speed PMS = 9,66 Kn
Velocity Ratio VR = 1,24
Capsize Safety Factor CSF = 2,04
Motion Comfort Ratio MCR = 18,46
Heft Ratio HF = 0,7
Downflooding angle: Fd = 110 º
Angle of Vanishing Stability AVS = 140 º
Roll Period T = 2,01 Sec
Roll Acceleration Acc = 0,22 G's
Stability Index SI = 0,59
Dellenbaugh Angle DA = 17,62

CE STIX STIX = 59,163 (taking some approximate measurements from stability curve)

So, Sylvester, based on this numbers I think the boat is quite suitable for club racing. About crossing oceans in crusing mode, she has a pretty high STIX, which is good, but seems to have high accelerations, so maybe uncomfortable movements, and would need an skilled and not too short crew to handle her safely in heavy weather.

Cheers.

[Raggi_Thor]

Dudley Dix has crossed the Atlantic at least twice in his "Black Cat" a Didi 38 he built himself,
http://www.duckworksmagazine.com/06/columns/guest/mcbride.htm

Dudley Dix comments:

I sailed her on the 1996 and 2000 Cape to Rio Races. In the 96 race our top speed was 18knots,in the 2000 race we topped 22 knots. In both races we took approximately 21 days to Rio. Despite the fact that the 96 race was a Spinnaker reach/run for about 16 of the 21 days and the 2000 race was a fetch for most of the race, with our spinnaker set for less than five days total time. Our best days run was 250 miles, or on average 10.4 knots. Our average speed across the Atlantic was over 7 knots.
She took 3000 hours of labour; most of it by me working single-handed.

[D'ARTOIS]

Dudley Dix is a well known designer and certainly knowledgeable in the various materials of his designs.

You may cross with any light boat oceans as long as you are aware that a light boat suffers from high accelerations as Guillermo pointed out so clearly and certainly the radius chine does not influence the seawothiness negatively.

Even single hard chine sailing boats went as far as the polar circles, so this is not really a point or issue.

[Wynand N]

Welcome back Brien:cool:

[boristhespie]

AS for plywood boats, check out

www.rm-yachts.com
www.portway.co.uk

This is a maker of Ply basded yachts, which are as nice as anything in anything else and fairly environmentally cuddly.

Check out the 12 strong points :

http://www.rm-yachts.com/en/points_fort.cfm

[Vega]

AS for plywood boats, check out

www.rm-yachts.com

Check out the 12 strong points :

http://www.rm-yachts.com/en/points_fort.cfm

Yes, a good and nice boat, but expensive. I have been recently at the shipyard. Nice work, but the RM 1200 full equipped will cost between 240 000 euros and 260 000:(

But of course, you can buy the plans to Marc Lombard and can build yourself the boat. It is a nice one.

http://www.marclombard.com/

Look at “Amateur constructions” and then at “Randonneur”.

Take a look at this one:

http://chloro.phil.free.fr/

[lazeyjack]

Hi, this is my first post. Although i have been viewing the forums on this site for a couple months now i finally thought i would post my first post.
I just wanted to ask the members of boatdesign.net for there opinion on this particular design. I have done extensive research on Dudley's Designs, the radius chine plywood method of building that is used to build it. And i have red most of the testimonials, and builder’s websites that have built and are currently building the Didi38/40.

So what are your opinions on the model, the design itself? I’m located on the shores of Lake Ontario 15 minutes away from Toronto, Ontario, Canada. I would like to use the boat for racing at the local yacht club and eventually sail it down the east coast and across the ocean to Europe and finally stopping in the Baltic Sea.

Here is a link to the Didi 38 page on Dudley's website: http://www.dixdesign.com/38didi.htm
Thank you for your time gentleman.

Sylvester Sawala

in my opinion the designs are neither fish nor fowl
you see if you are going to build a nice round bilge, do it, or nice chine boat , do it, but round chines achieve nothing
I worked it out, that to do a nice round bilge takes 4 weeks more than a chine boat
you are very limited to shape with a rounded chine

[Raggi_Thor]

I haven't seen Dudley's boats in real life, but on pictures they look good, to mee.

[lazeyjack]

what are your long term goals Raggi

[Raggi_Thor]

Just to be clear: The pictures above is not mine, but from www.dixdesign.com.

I'm not sure I understand, you mean in boating?
Now I work more with cad than with boat design and building.
One goal is to do more boat related work.
Regarding building I still have a Didi 26 under construction, but little time with wife and two kids :-)
I'll build some small dingies first, Argie 15 for example.
And maybe some from my sketchbook, M16 etc.
The B18 will at last be ready for trial sails this summer, and it will be shown in the Risør Wooden Boat show at august 2-5.
That's probably short term goals.
The major goal is to die happily, satisfied and tired at least 90 years old!
Sailing through the Caledonia Canal and south, and the round then Atlantic clockwise, return home via eastern USA, Canada, Greenland and Iceland is probably i mid term goal.

[lazeyjack]

Just to be clear: The pictures above is not mine, but from www.dixdesign.com.

I'm not sure I understand, you mean in boating?
Now I work more with cad than with boat design and building.
One goal is to do more boat related work.
Regarding building I still have a Didi 26 under construction, but little time with wife and two kids :-)
I'll build some small dingies first, Argie 15 for example.
And maybe some from my sketchbook, M16 etc.
The B18 will at last be ready for trial sails this summer, and it will be shown in the Risør Wooden Boat show at august 2-5.
That's probably short term goals.
The major goal is to die happily, satisfied and tired at least 90 years old!
Sailing through the Caledonia Canal and south, and the round then Atlantic clockwise, return home via eastern USA, Canada, Greenland and Iceland is probably i mid term goal.


I needed cheering up! you made me larf thank you

[Crag Cay]

Sly,

The Didi 40 would be an excellent choice for a 'cruiser - racer', or even a 'racer - cruiser'. You would have to decide at the construction stage which it was to be, as Dudley does offer you a choice of scantlings. I would be happy with the lighter version. It's well proven.

Your only limits on cruising area are going to be the draught. Bits of the ICW, Florida Keys, Bahamas and bits of Europe are more fun with shallow draft, but I've had loads of good times in them all with 6ft+. Again, with the other uses you have highlighted for this boat, I would go with the deeper draft option.

With plywood construction, a lot of it's strength and durability comes from the plywood you choose. They are certainly not all the same even if marked with the same 'standards'. Do some research and use the very best for the hull. It won't come cheap, however.

In Dudley Dix you have one of the best and most knowledgeable 'designer / builders' to be found anywhere and this is worth a huge amount when considering this type of project. He has, as they say, 'been there and done that'.

Don't worry about this method constraining the shape of the boat. Using largely developable panels gives entirely satisfactory hull shapes. There are loads of successful racing boats that use this method including the latest generation of America's Cup boats.

To chine or not to chine is a personal choice and one with which the sea shows no preference. In fact chines have made a come back on racing boats, with 'planing creases' appearing 15 years or so ago and now if you don't have a full chine aft you are 'dead in the water' (especially in France). But for some people, chines will always say 'home made' and for this reason, the radius chine offered on the Dix design are a good option. Basically you are just cold molding this part of the hull. The increased resale value will easily cover the extra work involved (especially when thought of as part of the total project commitment).

As has been mentioned, there are other similar designs available, but when comparing, remember to consider the complete plans / designer / support package.

See you when you get here!

[Wynand N]

in my opinion the designs are neither fish nor fowl
you see if you are going to build a nice round bilge, do it, or nice chine boat , do it, but round chines achieve nothing
I worked it out, that to do a nice round bilge takes 4 weeks more than a chine boat
you are very limited to shape with a rounded chine

If I may chine in

Have you ever seen a Dix radius chine boat out of the water:?: There are Dix radius chine and then there are radius chine in general.
Lazey, if you look at all the modern racing boats around, and more so the radical French, the general impression is that it is a radius chine hull of sorts - that is if you know what to look for....

Having built my share of Dix radius chine hulls - albeit in steel though - I can vouch for the cleanness and purity of lines of these hulls so to speak. It lacks the bulgy look of a proper round bilge hull and looks more streamlined and purposeful.

Something to ponder about. A very well known and successful NA once remarked to Dudley Dix in Cape Town, after checking out a radius chine Dix in steel; " it one of the best and nicest looking steel round bilge hull I've ever seen"
This guy designed some serious boats, including a BOC racer that once led the the race it was competing in until disaster stroke in the form of a submerged something three quarters through the race.
To save this designer some red face, I will not name him, but he since emigrated to one of those countries in the south that is so popular with South Africans

[DGreenwood]

I have been aboard a couple of his designs. They were pretty good looking boats for the simplicity of construction that Dudley seeks to deliver to the DIY types he sells to.
I tell you what, there are many other designers who sell to the same market that don't give their customers nearly the value that Dudley does.
This 65' steel boat is a damn handsome boat and relatively easy to build too.

[Wynand N]

DGreenwood, I actually built that Dix65 you pictured during 1991. In this photo we were at the stage of shotblasting and epoxy prime coating her.
She was built in Despatch, South Africa and can be seen at Dix website on the water and is named "Lorrigray II"

And looking at her in profile, one can see what I tried to get over earlier about the hull form....