69137Re: [bolger] Re: Fiddler 3 construction and foam insulation
- Dec 23, 2012Interesting confirmation of the narrative so far. Fearless experiment and then practical track-record in more than one hull.
For meaty bulkhead attachment and selective reinforcement all over the hull, I'd still favor a ply/epoxy/glass hull that is structurally fine by itself and then add the structural detailing and then apply inside or outside the foam/ply lamination.
Incidentally in regards to hull-panel shaping, on the 39'x7'6" SACPAS-3 project (#681) I favored and executed the full-length - i.e. 39'+ - topsides shaping for curve and twist, including application of first two coats of paint. Once stored in a rack on the legs of the two gantries that lifted and moved these 275lbs panels, they were thus ready to be 'hung' once the bottom was done to the same level of completion and turned over. This just left the seam along the chine-log joint. Ergo, profile- rocker, section-flare and planview-curves were 'locked-in' during the two ply-layer plus glass and paint assembly. And no challenge scaling up or down. But always a no-drip epoxy- and then paint-surface.
Back to the Narrowboat - while his light-weight Narrowboat visuals do imitate the heavy steel/iron ancestors above-waterline, his bottom-plate and box keel shapes are not what he calls hydrodynamic, at best tolerable at modest canal-speeds - for which these are designed. Due to the unavoidable eddies along the forward edge of a perfectly flat/no-rocker 'chine', reaching towards full hull-speed would not be a happy affair without a big rudder, extra power and an alert helmsman; eddies at the bow make for lively steering. Chine- and Box keel-Rocker would spoil the inch-deep 'authenticity' of the blunt-bowed and rounded burdensome ancestors - but would make a significant difference going up big European rivers.
- thumbs-up on the materials experiment and practical track-record,- but thumbs-down on the hydrodynamics of the bow.
Susanne Altenburger, PB&F
P.S.: I would assume that 'Cousin Pee' will attempt to show him as well the error of his ways by sharing his naked-&-wet refrigerator-foam anecdote with him...
----- Original Message -----From: Tim JenningsSent: Sunday, December 23, 2012 2:49 PMSubject: Re: [bolger] Re: Fiddler 3 construction and foam insulationFor the last year I've been corresponding with Edmund Sylvester, a UK boat builder and designer, who has built several large boats (18 to 50 ft canal cruisers) with a technique he's perfected using composite panels. The panels are made up of 2 sheets of 1/4" plywood skins glued to either side of a 1" sheet of DOW blueboard styrofoam. It's a bit more complicated than it sounds: he makes a 4'x8' frame of 1"x1" clear pine battens around the perimiter of one sheet of ply, with 2 additional battens spaced across the middle of the ply, inserts foam panels to fit the 3 cavities formed by the batten frame, slathers the whole affair between layers with liberal amounts of polyurethane glue (aka Gorrilla Glue), lays on the top sheet of ply, then presses the assembly together in a home built vacuum bag press, usually overnight. The resulting panel is extremely stiff, strong, and lightweight. Edmund's designs attempt to use these flat panels for as much of the hull as possible. The panels cannot be bent to a curve unless they are layed up and vacuum bagged on a form to the desired curvature ahead of time. Constant camber decks, cabin tops, and transoms can thus be accommodated. Bows and quarters are built conventionally. The panels are joined by butting the 1.5 inch thick ends together with resin, then fiberglass taped on either side along the joint (he cuts 3 inch wide mortises about 1/16th inch deep along the seam of the panels to be joined to accept the thickness of the glass tape. Completed hulls are then glassed with resin and faired conventionally.I've given only the barest of info here on the technique. You need to visit his web site for more detailed information. I'm certain that his proven home built composite panel techniques would find use for, in not hulls, lightweight superstructure assemblies, bulkheads, decks, and for non marine applications such as camper shells. He has a number of boats banging around European canals for several years now, testament to the durability of his panels.Tim JenningsEnfield, NHOn Mon, Dec 17, 2012 at 1:45 PM, <philbolger@...> wrote:As implied, on the 'cored boat hull & deck' issue a broad spectrum of sources of particular failures apply, with 'forensics' likely ranging from case to case. And then there are the hulls without those failures...
WEST-folks suggest roughing up the shiny surface of DOW blue foam-board.
On the foam-compression the assumption seems to be a 'naked' piece ?! We 'tested' crudely one such 1/8" ply x 2" foam x 1/8" ply x 10oz glass-cloth measuring 1'x8'. None of this is 'scientific' but certainly interesting:
- 1. Over 4"x4" blocking supporting just the ends and with the glass-cloth facing down we gingerly loaded up the piece via weights to beyond 550lbs as it just bent to touch the shop-floor.
- 2. We backed one corner of a 5500lbs vehicle over the piece supported just on its rear-end with the 4x4 upon which it first bent until the wheel got near the 4x4 and the top unglassed 1/8" ply failed by compression sliding over itself, with the separation within the foam just below the epoxy-line.
- 3. Laying flat on the concrete shop-floor we used the blunt face of a 5lbs hammer on the glassed surface and leaving a mild impression it bounced violently off.
- 4. For better control and less injury-potential we used a 10lbs sledge-hammer and it cut into the glassed surface - but by just 1/8"-1/4" and could not perforate the sandwich. Then we had at it 'something fierce' and 'made holes' - but not easily and predictably either.
We never took this beyond a basic curiosity as to how 'useless' such a sandwich would be... and it seemed to do better than we had assumed.
Surely no good reason to gamble a whole hull-structure on this. But the question here and elsewhere was posed under the assumption of having an adequate hull-structure before adding to it on the outside.
As to 'leaning with your shoulder...' the sledge-hammer exercise resolves that concern.
Installation of external foam over a sharpie-hull or multi-chine hull would be way easier if you add another chine-log and (de facto) sheer-clamp to finish the thickness of the proposed foam-addition. Then apply the foam, the lighter ply-skin and finally the glass - 'and Bob's your Uncle...' (or something)...
And as to blocking her up, there is the 'hard' keel and the hard chinelog - as before.
Plus of course enlarging each stanchion head-pad if one insisted on the 'softer' locations.
And coming alongside both chinelog and sheer-clamp will 'take the hit' - plus of course the rubrail itself.
As to 'picking poison', it is instructive to see the apparent durability of massive wooden laminations working on land and more importantly in the water on hulls from dinks and cold-molded trailer-types over 'Mega-Yachts' to 1000-1400+ tons naval vessels. Certainly, some of them go 'south' sooner than others in certain parts of their structures, likely similar in their 'forensics' to how 'soft' production solid and cored fiberglass-hulls can get, next to rusting steel and corroding aluminum hulls across all sizes and purposes.
Short of raising doubt about any and all aspects of cold/('hot')-molded wooden hulls which are painted, varnished, epoxied, glassed or epoxied, glassed, and then painted multiple layers - it would seem that we have a reasonable sense of both empirical understanding of 'the stuff' - which invariably invites exploring options to push matters further, such as via the original question posed about foam over hull on FIDDLER III.
Susanne Altenburger, PB&F----- Original Message -----From: GregorySent: Monday, December 17, 2012 11:12 AMSubject: [bolger] Re: Fiddler 3 construction and foam insulation
Cored boat hulls and decks get wet all the time, even when built to highest possible standard. TPI invented SCRIMP infusion and we've all seen plenty or Jboats, Freedoms, and other high-end, "scientifically" constructed cores fail. Of course, epoxy accepts water slower than vinylester, which accepts water slower than polyester, and many failures can be attributed to improperly made penetrations, or just, penetrations. In nature, all voids are temporary.
And, I own a cored boat and built a cored airplane.
Dow Blue may not rot, but its glue lines will likely fail (right along its slick surface). Wood rot happens quickest within a narrow range between totally dry and soaking wet, but trapping water in a "closed" wood system is a bad idea. It's at the core of the argument to encapsulate the interior or let it dry. Pick your poison.
Balsa will rot, but it offers mechanical strength. Balsa is used end-grain; meaning the fibers "T" against the skins, with a compressive strength of about 2000 psi.
Dow Formular High Compressive Strength Rigid Foam Insulation has a compression strength of about 25-40 psi. Their failure criteria is interesting:
"Compressive resistance at yield or 10 %
"deformation, whichever occurs fi rst (with skins 40psi
"intact) min, psi (kPa)
So, if your survived rot and shear failure, imagine what's going to happen when you sling your boat out, block it with stands, set it on trailer bunks, bump against a piling, or even lean your shoulder against it in the boatyard. At least outer skin will stop at the inner skin.
Seems like a lot of work to avoid insulating the interior ;-)
--- In email@example.com, <philbolger@...> wrote:
> Regular home-center DOW blue-board has very low water absorption-rate if left afloat/wet. As an inside-part of a laminate here, it would remain bone-dry !
> Good thing that with a structure solid enough to live without the foam-belt, the outside addition of closed-cell blue foam-boards won't constitute any of the challenges quoted such as 'creep', water-absorption etc. Ergo low-cost upgrade of the hull without serious drawbacks, as long as matters are well-bonded and glassed over.
> And any weight added via 1/8" skin in this case plus 'paper-weight' foam, plus glue/epoxy/glass will only add very modest weight on the trailer. In the water however, the hull floats up some as it would have gained more buoyancy than net weight. She could carry extra load before immersing to the same waterline as before...
> Susanne Altenburger, PB&F
> ----- Original Message -----
> From: Gregory
> To: firstname.lastname@example.org
> Sent: Sunday, December 16, 2012 2:46 PM
> Subject: [bolger] Re: Fiddler 3 construction and foam insulation
> I don't like it, but it's more of a material complaint.
> It doesn't matter if you build from the inside out, or the outside in - your goal should be light weight skins, both stressed and well bonded. If you build a boat with sufficient (stand-alone) interior skin strength, it doesn't make sense to add adhesive, foam and a heavy second skin - you would be smarter and lighter to insulate the interior.
> The floatation is the same. (The argument to be able to fair the exterior skin is ~OK, but there are a lot, lot better methods - like
> Still, unless you build a significant set of structural skins, your core will get wet.
> Of course, there are lots of cored boats (and planes), but none with styrofoam. Have a look at Jamestowns cores:
> All those foams and balsa have mechanical strengths 2-3 orders of magnitude better than styrofoam - which essentially has none. Your skins will move, and they do, your foam will fail in shear. You'll likely have a boat sitting in a bucket. But, those materials are expensive. Long and short of it, don't use non-structural (weak) materials in a structural sandwich.
> Having said that, I similar idea about building a dinghy from extruded styrfoam, where you might waterjet the panels and shape the edges for a nice joint. But, My idea was to cut holes every 6" or foot and insert a transverse wooden dowel, balsa, or some rigid element to transfer shear across skins. You might estimate the period knowing the properties from testing, but still, I think the skins would delaminate eventually. I wouldn't risk it on a big project.
> --- In email@example.com, "daschultz8275@" <daschultz8275@> wrote:
> > So now I am thinking to head back toward Bolger's construction scheme for Fiddler 2 and adding the box keel on to it, with the 2x2 bottom timbers cutaway over the walking area not under the berth. The width of the box keel would be to match the fore/aft keelsons that form the cabinetry.
> > I am thinking to clad the OUTSIDE of the hull (not the bottom), on the sides and top, with 2" pink foam and wrap that with glass/resin, possibly over 1/8" ply for fairing. Anybody tried the foam this way? I know PB&F suggested such a scheme for one of the big ASxx cruisers. Insulation, floatation, and it gets the water that much farther away from the structure.
> > Whatcha' think?
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