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Core-less deck

4K views 10 replies 8 participants last post by  wrwakefield 
#1 ·
A cored deck (balsa, or whatever) is a good way to get stiffness without a lot of weight. Obviously, the problem with having a wood core is that is turns into potato soup if there is water intrusion for a while. What about having a solid (not thick) deck with stringers?
 
#5 ·
My understanding is that CSY used a glass slurry as a core, basically troweling on thickened resin to build up depth without using a more vulnerable core material. They also used plywood in some of their boats (or in some parts of their boats) which I have seen in person.

Jeff
 
#4 ·
In the early days of fiberglass boat building, the British (and some/most Commonwealth Countries) built boats without deck or hull coring, relying on closely spaced framing instead. That is how my boat is constructed (except that there is coring in the molded glass deck hatches such as the anchor compartment and life raft compartment lid. I just had to recore the life raft compartment lid). Properly done a framed deck is not inherently heavier or more flexible than a cored deck. My sense is that it is probably more labor intensive, but even if not more labor intensive, it takes a lot more care to do well since the glass must follow the contours of the frames while remaining free of voids.

The nice thing about a well designed boat with this system is that all hardware ideally ends up being bolted in areas where there is only solid glass and no framing.

(As was done on my boat) if you combine this with a wider inward facing hull-to-deck-joint flange at stanchions, rail tracks, and cleats, you end up with very strong connections and minimize the chance of damage to the coring in the frames.

Lastly, ideally if the coring is a high-density closed-cell foam then you minimize the chance of having mush whether the entire deck is cored or just the framing.

Jeff
 
#9 ·
C-Flex was a way of producing a comparatively fair lay-up on a one off hull built over simplified male molds. Unless otherwise reinforced, C-Flex typically produces an excessively heavy hull for its strength and stiffness. It really does not inherently produce a lighter/stiffer/stronger structure that corresponds to the weight reduction, strength and stiffness advantages that comes from either coring or closely spaced framing.

That said, many of the stock designs intended for C-flex construction did not show coring, counting instead on simply adding enough laminate to reach an acceptable level of strength and stiffness.

Jeff
 
#10 · (Edited)
Also insulation from the sun and the winter cold. These can be big factors.

Condensation is greatly reduced. Since one of the leading causes of deterioration is interior mold, I might counter by saying that a cored deck increases the livablity and lifespan of the interior.

The stringers will cause stress risers, there will be more flexing, and there will be more hairline cracking of the gel coat (generally just cosmetic), assuming you do not go way up on weight. But folks hate that.

Avoiding intrusion is a matter of good design too. For example, the core should not extend to the deck edges (cleats and stanchions), some coaming areas (winches), or around the mast (hardware), below the waterline, close to the rudder post, or at the extreme ends (dock impacts). Those areas should be substantial solid glass. Then mount any other hardware mindfully.
 
#11 · (Edited)
The deck on our Nauticat is coreless, hand lay-up that averages 3/4" to 1" thick.

They bonded U-shaped fiberglass channel stringers on the underside of the deck to which the headliner panels are attached. [The open side of the channel stringers are against the deck underside- resulting in a closed rectangular beam which is good insulation- and wire channels....]

Mounting the headliner panels to the bottom of the 1" channel stringers results a 1" air gap between underside of deck and top of headliner panels. That provides adequate insulation for most climes... We are adding 1" of rigid foam board in that space to insulate further.

The insulating properties of the bonded channel underdeck stringers allowed me to map our entire deck last winter with a light snowfall and turning up the heat to 80°F.

Following is an image of the yet to be insulated foredeck area clearly showing the stringer locations, and one showing the underdeck, a stringer with headliner panels attached.

In case this is useful.

Cheers! Bill

PS: Suddenly the method of adding photos to this forum has changed to drag and drop [tedious and too time consuming...] I hope they appear in a small size as intended...
 

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