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]

Originally Posted by Sly

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]

Originally Posted by Murdock

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/...st/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

[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]

Originally Posted by boristhespie

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/