Double Hulled Boats
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Matt Gurnsey
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The Venture Series of boats (23 and 26) also use a similar interior pan arrangement as the Marinaut. I'm not sure how it's sealed in the hull, and I seem to recall seeing one with an access "pie" plate, which might compromise and water tightness of the space.
Rich,
My apology about the name-yes, I was addressing you.
You posted "Do you know that in the Northeast, there are no cost effective alternatives to the C-Dory line or Marinaut?"
You don't shop for boats just at boat shows. You research the various publications, look at used boats, do internet research, and often depend on people who have more experience than you. I am very glad you have a boat which works for you--it would not work for us, for a number of reasons.
To address your quote--and challenge that there are no other satisfactory pilot house boats on the East Coast.
There are multiple small builders who build on the down east, Sea Skiff, and similar type hulls. There are also larger builders such as Rosebrough (currently built in the USA) along with SeaWay and Eastern, Parker is extremely popular on the East Coast, Shamrock (mostly inboards), MayCraft, Steiger, and Atlas/Acadia come to mind off hand. of boats available, also some of the Nimble/Kodak type of boats meet these criteria. (and a bunch of others, which have a different hull forum--like the Adventure craft etc)...
My apology about the name-yes, I was addressing you.
You posted "Do you know that in the Northeast, there are no cost effective alternatives to the C-Dory line or Marinaut?"
You don't shop for boats just at boat shows. You research the various publications, look at used boats, do internet research, and often depend on people who have more experience than you. I am very glad you have a boat which works for you--it would not work for us, for a number of reasons.
To address your quote--and challenge that there are no other satisfactory pilot house boats on the East Coast.
There are multiple small builders who build on the down east, Sea Skiff, and similar type hulls. There are also larger builders such as Rosebrough (currently built in the USA) along with SeaWay and Eastern, Parker is extremely popular on the East Coast, Shamrock (mostly inboards), MayCraft, Steiger, and Atlas/Acadia come to mind off hand. of boats available, also some of the Nimble/Kodak type of boats meet these criteria. (and a bunch of others, which have a different hull forum--like the Adventure craft etc)...
thataway":soijch60 said:
Hello Bob. You would not believe the extent of our research we performed, which was not relegated soley to boat shows. I even read Devlin's book on boat building, as well as other designers. Not one of the production boats you listed meets the criteria I stated in the challenge, albeit most are very good boats. We actually considered the Rosoborough and Atlas Acadia, but these were larger boats, did not meet our fuel efficiency requirements, the Acadia had too much draft, and both cost over $100k fully equipped. For those people who have Rsoboroughs, though, it is an intelligent choice and a boat of superior construction. However, it was too expensive for our desired overall costs of ownership. The 23' Parker is inexpensive, but is really a fishing boat. The 23 footer only gets 2 mpg, its berth is not anywhere near as nice as on C-Dory's. It does not have a dinette. Smaller Seaway's are not as efficient or as good for multiple nights unless one gets a Coastal Cruiser, but it was over $100k and its fuel economy was not great. Larger Eastern boats are good but are expensive and not as fuel efficient. We looked at Steigers and Maycraft, but these did not meet our criteria, either. We even looked into the Nimble. While fuel efficient, it can be underpowered. It wonderfully uses space, but is not designed for rough water.
If a person wants a lot of space and economy, sailboats fit that need for sure -- if you like living in a cave.
What My wife and I found frustrating, was that virtually every boat we examined, something was sorely missing. Now I understand why qualified people design and build their own boats. Our Marinaut was the closest vision to what we wanted in a boat, albeit we would have been happy with a CD 22 if we customized it with features we desired. Indeed, the Marinaut is a direct beneficiary of ideas generated from C-Brats, particularly Dave's input and Ben's hull design. So we flew across the coast to test out a Marinaut. We fell in love with it. It met our objectives, and its total annual cost of ownership is very reasonable for the Northeast.
Rich
I talked to Oldgrowth Dave extensively about the Marinaut design and also took a good look at it at EQ. As Rich correctly points out, the bottom of the boat does have a "double hull" feature. E.g. the outer hull is constructed very similarly to our C-Dory's (with foam instead of balsa core. After the hull is complete a floor liner is added and glassed in all around. The floor liner has a gap between it and the main hull and the gap is considerable in the center of the boat, under the berth and under the risers one which the seat sit. That ENTIRE area is closed off and sealed. To my knowledge, there is no foam between the one-piece floor liner and the hull, but there is a considerable volume of air there (Dave or Les - correct me if I'm wrong on that). There are no holes whatsoever floor liner and part of Dave's design was to assure that none would be needed. The attachment points for the seats etc. are molded into the floor liner in such a way that no through holes penetrate the liner. I seem to recall that either stainless or aluminum plating was molder in where it was needed so that one can drill into and tap a threaded hole without compromising the flooring integrity (again I could be wrong with my memory here). The plus side is effectively a double hull and a liner that won't leak even if the outer hull is penetrated.
The down side is a loss of storage space in the void areas. E.g. if you cut holes to put hatches in under the berth, you penetrate the liner. Also the storage space on the bottoms of the cabinets and under the area where your feet are while seated at the dinette, is also "lost" to gain the sealed liner. Another potential issue is that if the hull is compromised (and if the void is not foam filled) the volume below the floor liner could fill. This might actually be beneficial and provide some balast that would keep the boat from turtling - I don't know but I suspect it might be helpful. Again, this comment depends on what is in that void.
To my mind, the loss of storage area in places that I had a lot of things stored in my CD22 was a poor tradeoff for the benefits of a double hull, but that's my personal choice and not one with which everyone would agree.
The down side is a loss of storage space in the void areas. E.g. if you cut holes to put hatches in under the berth, you penetrate the liner. Also the storage space on the bottoms of the cabinets and under the area where your feet are while seated at the dinette, is also "lost" to gain the sealed liner. Another potential issue is that if the hull is compromised (and if the void is not foam filled) the volume below the floor liner could fill. This might actually be beneficial and provide some balast that would keep the boat from turtling - I don't know but I suspect it might be helpful. Again, this comment depends on what is in that void.
To my mind, the loss of storage area in places that I had a lot of things stored in my CD22 was a poor tradeoff for the benefits of a double hull, but that's my personal choice and not one with which everyone would agree.
Of course you do have a choice with the Marinaut, Les would be happy to modify the 215 and add hatches and storage, it's the customers choice if they desire to forgo the sealed air space between the sole and the hull by adding storage. I'm not sure why they weren't molded into the sole mold in the first place. Seems like you could mold in the storage and retain the air thight space.
Jake
Jake
Jake":1tya5cry said:
Hello Jake,
It's nice to hear from you again. Roger did a fantastic job of describing how the Marinaut floor pan was put into place, which was much better then I did. I agree with him that the CD 22 has more storage space if one takes into account only the cabin. However, if you take into account the space under the splashwell, the Marinaut has quite a lot of storage space. I have been honest with people in saying that my wife and I have all the space we need. That may not be true for others who fish and have other activities requiring more space.
Over a year ago, Les and I discussed adding hatches and storage into the sole area so long as high quality hatches that were water and air tight were installed. Les tends to be conservative as I am, so he leaves it up to the customer. "Primetime" Steve showed me pictures of his hatches, and I've got to tell you it is tempting to do what he did. I'm sure he will be posting pictures for the group. I don't see it as compromising the security of the enclosed space so long as a person is vigilant to ensure that the hatch is secured when underway.
I would like to also point out that not having a portable toilet in the cabin frees all that space in the V-Berth for storage that would otherwise be used for the Portable toilet.
One thing I am thinking about doing this year is to make a separate berth extender. When we are docked or anchored, it would be nice to leave the dinette cushions in place and use a separate berth extender in its place. The extender could double for storage of clothing or small items. BTW, it would also extend the storage space underneath. The advantage is that we can leave the bed made up and ready for use without as much exertion. I don't know how well it will work, but I intend to give it a try. So you see, there really is a lot of storage on the Marinaut.
Rich
Les Lampman
New member
starcrafttom":3sdjfwm9 said:
Gosh, I'm sorry I missed this at the time, I must have had an awfully lot going on.
Okay, first of all, I don't market the Marinaut with the idea that it's a "double bottom" boat, or unsinkable, etc. Since we have a very strong hull (and the boat is light) the biggest advantage I see to the owner/user of the M215 is that the one-piece liner keeps water from getting down into the under deck spaces (as long as it's not compromised by running screws and such through it that are not properly bedded).
The "floor" or "liner" in the Marinaut 215 sits on a "shelf" that's a step molded into the hull. The liner is one piece from the bow to the transom. It's placed in the hull while the hull is still in the mold and bonded in place on the "shelf" or "step" that's part of the design of the hull. At this point (as long as the part has been bonded properly) we have a watertight and airtight compartment between the liner and the hull. The Coast Guard says that we can NOT call or consider that a buoyancy chamber because part of it is made up by the hull itself.
Most of the time, in a typically loaded M215, the "step" in the hull (where the liner is bonded) is above the waterline. If one managed to breach the hull below the level of the liner whatever water entered the hull would remain below the liner and would not compromise the cabin and/or cockpit spaces. That's making a lot of assumptions, like: the impact doesn't compromise the liner-to-hull bond, and that holes haven't been put in the liner by cutting open a portion of it for storage, or by running fasteners into it that aren't sealed, etc.
This has nothing to do with hull construction per se. The hull is of typical sandwich construction with an outer layer of fiberglass, a core of foam, and an inner layer of fiberglass; in that respect it's no different than hundreds of boats. The only thing in the M215 that (maybe) gives it an edge if one happens to breach the hull is the bonded-in liner providing (hopefully) the effect of a "double bottom" by keeping whatever water makes its way into the breached hull out of the cabin and cockpit (as long as the bond remains intact and the liner has not been compromised previously by holes). In this regard it's completely different from a C-Dory (and a lot of other boats as well).
To me, the idea that the Marinaut has some resistance to filling up with water if I hole the hull below the waterline comes along as a perk; it's not "the" selling point of the boat and I don't want folks to think they're getting an "unsinkable" boat because of the bonded in liner. I do think it might be helpful in the right circumstances and if it was my day to experience those circumstances I'd be happy to stay dry. That said, it's a pretty unlikely scenario in the first place and the strong cored hull helps keep it from becoming a reality.
I have learned long ago that every boat is a compromise. Do we want space? mpg? Light weight? Unsinkable? Usually one has to trade off one feature against another. I loved my Boston Whalers in a previous life partly because they were unsinkable. I know Bob may disagree on that point but once they shifted to the current foam recipe, about 35 years ago, the foam stopped absorbing water and they could happily be cut in half and driven around as two pieces, even after time in the water. The military tested a few with machine guns below the water line and were convinced. I swamped mine a couple of times and was grateful for "swamped capacity". Have a look at the BW website if you don't know what that means. No other builder publishes those numbers. I did things with my whalers that I would never do with any other boat. 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. It's a compromise. I use it very differently than I did the Wahlers. The boat and the sea have my confidence and respect.
Don't worry whether your boat is double bottomed or double hulled. Whatever it may be it is only as good as the man or woman at the helm.
Don't worry whether your boat is double bottomed or double hulled. Whatever it may be it is only as good as the man or woman at the helm.
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.
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).
chimoii":1rl94kpo said:
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).
NORO LIM":3mbspciz said:
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).
Sunbeam":314k4qat said:
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.
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.
D.D.
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
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
Will-C":3h1v5knv said:
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/fiberg ... -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.
journey on
New member
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
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
journey on":386wfoy2 said:
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
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.
"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.