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NORO LIM



Joined: 24 Apr 2008
Posts: 875
City/Region: Olympia
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 23 Venture
Vessel Name: NORO LIM (sold 12/12/14)
Photos: NORO LIM
PostPosted: Tue Jun 11, 2013 12:29 am    Post subject: Reply with quote

Sunbeam wrote:
I don't mean for this "nitpick" to take away from your main point, which was that all boats are compromises and one needs to choose the best set (of compromises) for ones uses and taste. I agree whole-heartedly with that point.

chimoii wrote:
In the end I bought a C-D Venture 23. It is not unsinkable but does have some foam in the hull. That makes it heavier and less fuel efficient than a 22. Maybe it also means it rides better.


But... I don't see where a foam-cored hull would be noticeably heavier than a balsa-cored one, all else being equal; so that makes me think it's something else (other than foam core) about the Venture 23 that makes it heavier (and probably hull design that makes it ride better - looks like it's an "evolved" hull design as compared to the 22 Cruiser).


See post above. The CD has a cored fiberglass sandwich hull. That's it. The Venture has the same kind of hull, but it also has an additional sole with foam between the sole and the hull. That's not the only reason it's a little heavier, but it is one.

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2001 CD 16, 2001-2006
2006 CC 23, 2006-2014
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Sunbeam



Joined: 23 Feb 2012
Posts: 3990
City/Region: Out 'n' About
State or Province: Other
C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Photos: Sunbeam
PostPosted: Tue Jun 11, 2013 11:52 am    Post subject: Reply with quote

NORO LIM wrote:


See post above. The CD has a cored fiberglass sandwich hull. That's it. The Venture has the same kind of hull, but it also has an additional sole with foam between the sole and the hull. That's not the only reason it's a little heavier, but it is one.


But how is that really different from the post ~2006 C-Dory 22 Cruisers, which all have a permanent/flat cockpit sole which is a fiberglass/core/fiberglass sandwich? When I was boat shopping I also considered a Cape Cruiser (Venture) 23, and from what I read it's similar to a "modern" C-Dory 22, in that it has a "structurally" cored hull and then a cored sole (which is structural only in that it supports the people aboard, as opposed to being a "structural" part of the boat itself). Granted, the CC/Venture also has a flat cabin sole, but I don't see that being a huge difference in weight, and no difference in design in terms of the way the boat handles. Maybe there is more to the Venture that I don't yet understand though (as I ended up deciding to buy a C-Dory, and not only that but a C-Dory without the permanent/flat sole).

I was thinking that the differences in handling were more down to the "evolved" hull design, which seems to have moved in a similar direction as today's Marinaut (I'd guess most of the change has to do with better handling of today's heavier motors, but there are probably subtle changes throughout - this makes sense as they are by the same designer/family, as I understand it, and so why wouldn't they evolve.) I don't specifically know why the boats are heavier (presuming they would be heavier for the same length).
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NORO LIM



Joined: 24 Apr 2008
Posts: 875
City/Region: Olympia
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 23 Venture
Vessel Name: NORO LIM (sold 12/12/14)
Photos: NORO LIM
PostPosted: Tue Jun 11, 2013 1:15 pm    Post subject: Reply with quote

Sunbeam wrote:
. .

But how is that really different from the post ~2006 C-Dory 22 Cruisers, which all have a permanent/flat cockpit sole which is a fiberglass/core/fiberglass sandwich? . . .


You're right. I was thinking of comparison between the original CC Venture and its contemporary (and earlier) CDs. As far as weight difference goes, I think the Venture is marginally bigger, has a full height transom, maybe heavier built-in interior? Don't really know.
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Will-C



Joined: 21 Aug 2007
Posts: 2476
City/Region: Temple
State or Province: PA
C-Dory Year: 2008
C-Dory Model: 23 Venture
Vessel Name: Will-C
Photos: Will-C
PostPosted: Tue Jun 11, 2013 2:09 pm    Post subject: Double Hulled Boats Reply with quote

I think the main weight differences are that the foam weighs more than the balsa core, A Venture 23 is taller longer and wider than a 22'. The forward section of the bow is a little sharper/deeper as that helps break the chop. The v continues back and it has pretty wide chines until well aft then it's flat like a 22' The Venture's had insulated interiors that don't sweat like a whore in church as compared to the non insulated boats. They had two aluminum 30 gallon fuel tanks. They also came with more standard equipment, shore power, battery charger, refrigerator, interior grab rails, hot water heater, electric fresh water pump, raw water wash down, shelves, the forward dinette seat came be set up to face front or rear, tilt helm. All this contributed to a heavier boat. The C.C. and the Ventures were the evolution boat with changes Mr. Toland thought were in order. The Ventures were brought out right when the bottom dropped out of the boat market in 2008. I would have bought a 22' but the ours came from a dealer who had lost his floor planning so it was priced to move.
D.D.

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Will-C



Joined: 21 Aug 2007
Posts: 2476
City/Region: Temple
State or Province: PA
C-Dory Year: 2008
C-Dory Model: 23 Venture
Vessel Name: Will-C
Photos: Will-C
PostPosted: Tue Jun 11, 2013 2:20 pm    Post subject: Double Hulled Boats Reply with quote



The picture is our 23' Venture right across the dock from Jay's Hunky Dory 22' at a campsite on Yellowstone Lake. It even looks heavier.
D.D.
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C-Nile



Joined: 09 May 2008
Posts: 638
City/Region: Connecticut
State or Province: CT
C-Dory Year: 2012
Vessel Name: Betty Ann
Photos: C-Nile
PostPosted: Tue Jun 11, 2013 8:55 pm    Post subject: Reply with quote

Sunbeam,
The bow on the Marinaut is so sharp that it cuts through waves like a hot knife through butter. But to do so, I need engine trim and trim tabs set down all the way to keep the bow down. We can go through three footers at around 11 knots in a head sea, and hit an ocassional four footer without being jostled too greatly. In a following sea with waves that height, we can go close to 18 knots, and if we overtake the wave in front of us, it slices through that wave, too, with little difficulty. I could not move through waves like that with the bow of my CD 16. So in my opinion, the Marinaut is an evolutionary improvement over past designs. Unfortunately, my only reference point is the CD 16 cruiser we had for four years, but I have been on a 23 Cape Dory ( My Lee ) and a CD 22 ( C-Gnome ), and they were both very beautiful and well-fitted cruisers that we would be proud to own had we not had the Marinaut as an option. Ironically, it was not performance that was the main reason for our getting the Marinaut. My wife Betty feels clostophobic in enclosed berths. She wanted an open berth similar to our CD 16 cruiser, so we can thank Dave for that (important to us) innovation.

Rich

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CD 16 Cruiser "C-Nile" Sold 06/2011
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Foggy



Joined: 01 Aug 2013
Posts: 1518
City/Region: Traverse City; Northern Lake Michigan
State or Province: MI
C-Dory Year: 2014
C-Dory Model: 26 Venture
Vessel Name: Boatless in Boating Paradise
Photos: W B Nod
PostPosted: Sun Aug 11, 2013 9:08 am    Post subject: Re: Double Hulled Boats Reply with quote

Will-C wrote:
I think the main weight differences are that the foam weighs more than the balsa core,
D.D.


Sorry, but this is not true. There are many different "foams" out there in composition, thickness and weight. Baltek makes most of the end grain balsa for boat construction. The main weight difference in a "cored" hull, balsa or foam, is not determined by the core but by the skin - the outside resin and fiberglass layers; i.e., how many layers of what kind of fiberglass, hand laid or vacuum bagged, builder expertise, etc. Balsa excels in compressive and sheer strength over foam. For foam to equal that of balsa, thicker foam is required. Don't take my word for it, read it here:

http://www.boatdesign.net/forums/fiberglass-composite-boat-building/balsa-core-vs-foam-core-9882.html

I have had both balsa cored and foam cored boats. Most of the differences for the sake of comparing weight are academic/theoretical, not practical. If you must have one over the other for "peace of mind", by all means go for it. Once underway, you simply cannot tell the difference.

Aye.
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journey on



Joined: 03 Mar 2005
Posts: 3593
City/Region: Valley Centre
State or Province: CA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: journey on
Photos: Journey On
PostPosted: Sun Aug 11, 2013 12:22 pm    Post subject: Reply with quote

The purpose of the spacing between the two hull layers is to provide beam strength. It doesn't matter what the material between the hulls is for structural reasons. The lighter the better, because it doesn't offer strength, just spacing and vibration damping.

Certainly it shouldn't be crushed, get soggy, rot, etc, but it only spaces the hull fiberglass layers out. One could do the same by using a fiberglass web.

Spacing the hull structure layers apart is the sole purpose of the foam. Greater rigidity with less weight. Such a hull isn't double hulled in any sense of the word, it's just a (good) way of building a structural member/hull.

Structures which flex gain strength as the outer layers are spaced apart. An I-beam is a great example of that. The two flanges provide the rigidity/strength. The connecting flange is to hold the outer flanges apart. Though I don't remember much of my Strength of Materials course, the strength increases at least as the square of the distance, since the moment of inertia is used to calculate stress. Tubes in torsion are another example.

Boris
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Sunbeam



Joined: 23 Feb 2012
Posts: 3990
City/Region: Out 'n' About
State or Province: Other
C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Photos: Sunbeam
PostPosted: Sun Aug 11, 2013 12:32 pm    Post subject: Reply with quote

journey on wrote:
The purpose of the spacing between the two hull layers is to provide beam strength. It doesn't matter what the material between the hulls is for structural reasons. The lighter the better, because it doesn't offer strength, just spacing and vibration damping.


While I think that holds true for our sized boats (which in the grand scheme of things are relatively lightly stressed), I don't think that's always true. Reason I say that is I have skimmed articles wherein they speak of the various properties of the different coring materials (balsa vs. various different types of foam). In higher stress, "more engineered" boats (usually larger) various specific cores are chosen for various characteristics.

Maybe you were just speaking of C-Dorys or Ventures, in which case I agree that type of foam is not really going to make much difference, as long as it is well-bonded. But I couldn't tell if you meant boats in general too.

Sunbeam
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thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Sun Aug 11, 2013 4:40 pm    Post subject: Reply with quote

From the article Foggy linked to:
"but to get the same stiffness from a foam core requires a thicker laminate, or a thicker core, or both, and results in a heavier panel. ATL in Queensland make Epoxy/balsa/epoxy panels, as well as epoxy/foam/epoxy panels. They have comparitive data for them on their website. www.atlcomposites.com.au"

There is a lot of homework to do to compare the weight of various core materials--and the amount of glass necessary to make the same stiffness (deflection)-but there is also the impact resistance and compressability involved, as well as adherence of the core to the outer laminates.

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Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
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journey on



Joined: 03 Mar 2005
Posts: 3593
City/Region: Valley Centre
State or Province: CA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: journey on
Photos: Journey On
PostPosted: Sun Aug 11, 2013 5:44 pm    Post subject: Reply with quote

Sunbeam, I was speaking for structures in general, not just boats. You space the load carrying elements further apart, and they become stiffer. Remember I-Beams?

I'll say that the core properties are relevant, since the outside elements flex, warp and twist, flexing the core, but that's a secondary factor. They are there to provide spacing between the structural elements.

Remember that C-Dory sterns have structural foam in them. This is foam designed to carry a load and it does that well. On the other hand, what load do you expect end-grain balsa squares or non-structural foam to carry? The compression strength is low, the tensile strength is even lower, etc, etc.

So the characteristics we ought to be discussing is resistance to water intrusion, flexibility, ease of manufacturing and other non-structural properties. Strength doesn't count. All the spacing materials are about equal there.

Boris
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Sunbeam



Joined: 23 Feb 2012
Posts: 3990
City/Region: Out 'n' About
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C-Dory Year: 2002
C-Dory Model: 22 Cruiser
Photos: Sunbeam
PostPosted: Sun Aug 11, 2013 8:02 pm    Post subject: Reply with quote

Boris,

It seems like I must have misunderstood your previous post (the one I responded to). Sorry if I mis-spoke on account of that.

Sunbeam
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