OP
OP
Genesis
Guest
Material.....
... is coming out all the way forward to very close to where the caprail is molded in (basically to the end of the core), in the outline of the pulpit's "print" on the deck. The core at the windless switches (to each side of the pulpit) is visible from below and is sound and dry, so I know that the damage does not extend beyond that point. That core area is going to get soaked with CPES and epoxy during this process, however, so it won't become troublesome in the future.
So yes, it will indeed be where you're talking about.
However, let's think this through.
Right now, there is ZERO core rigidity in that part of the foredeck. Zero. HAND pressure on the deck under where the pulpit was is sufficient to deflect the deck 1/4" or more from the top of the laminate. I don't dare STAND on it, as I suspect I'd end up in the chain locker.
That's how weak it is now.
This was NOT obvious until the pulpit came all the way off! Indeed, I thought this was confined to the area immediately surrounding the windless bore. Its not.
Most of the strength of the deck is from the truss-like arrangement of the core and two skins, and depends on the bond between each layer of skin and the core for strength. The skin itself is not flexurally strong; indeed it has a great deal of flex. While it is true that the skin provides strength, that strength is in tension - where fiberglass has GREAT strength. I am not going to butt-joint the piece when it is replaced; I am going to make a "V" joint and lay a couple of layers of cloth over and into it, epoxying the joint in place and effectively making a scarf joint with roughly a 5-10:1 aspect ratio. That joint should exceed the strength of the original piece of deck by a substantial margin as it appears that the deck skin itself is one layer of mat and one of roving, and is certainly not more than 1/4" or so in total thickness. In addition the joint can 'stand proud' somewhat since it will be under the pulpit when complete and as such does not need to be fair with the original deck surface. There's no way that's coming apart once its completed.
Further, the entire core area extending well beyond where the deck skin will be penetrated will be saturated with epoxy and allowed to harden. This sort of treatment produces a rock-hard substrate with structural rigidity all on its own, especailly if you use plywood for the replacement core and fill all gaps with structurally-thickened epoxy. The ultimate strength of this section of deck even without the top layer of skin back on it will likely exceed that of the original construction. With it, the strength will be radically higher than as originally built, as the load will be distributed over the entire deck out for a foot or more from the original mounting point.
Restoring the original design strength is a matter of restoring intimate adhesive contact between the core and BOTH skins. This restores the truss design and thus the deck's strength. The issue with deck core deterioration is as much the disbonding of the core from the skin as the rot - that's what destroys the strength.
Consider the deck as something like this...
===============
core core core core
-------------------
And its rotted end-to-end.
OK, what we're going to do is this:
=== ===
------------------
All dug out.
Then...
=== ===
plywood | plywood
------------------
Where the pieces that are fit BETWEEN the pieces of deck skin are coated with epoxy thickened with microballoons, so as to form a structural adhesive, and the plywood itself is first resin-infused. The gap between the pieces (necessary so we can insert it in the recess) is likewise filled with structural epoxy, and the plywood bonded to the sound core on both sides with filled structural epoxy as well.
Now, what we've done is re-created the original truss, and likely stronger than the original deck even without the cap piece, because the plywood, infused with the epoxy and all bonded up, is actually a structural material itself (the balsa that came out was not!) We now put it back together as thus:
___ ___
===|=======|===
-------------- <<< Cloth tabbed under edge
plywood | plywood
-------------------
That ain't NEVER coming apart. I'll bet any other part of the deck fails first. In order for that part of the deck to fail the new core would have to disbond all the way around from the top and bottom skins extending under the cut piece AND the tabbing on both sides has to fail; otherwise there's no way for it to move. That ain't gonna happen, especially using epoxy which is radically stronger than the original polyester resin used to build the thing.
The other option is to build the laminate from the inside skin to deck level out of alternating roving and mat layers of fiberglass, much as if I was laminating a hullside or bottom. If I go this route I'll end up with a deck section that will be nearly 1" thick (!) and which is effectively tabbed into the existing deck structure on all sides around, since the roving and mat sections would be inset into the deck skin on all sides by a substantial amount, and bonded to the core and skin all the way through. That would produce tank-like structural strength, but it is also radically beyond what was originally built and in fact is getting fairly close to the kind of layup schedule one would find in a hull bottom!
That would look like this:
=== ===
Gap where core removed
-----------------------
=== ===
++++++++++++++++++ << Roving/mat layers built up
-----------------------
And then we top it with the original deck
===|=========|====
+++++++++++++++++
----------------------
The latter would be crazy-strong and likely wouldn't even require the top cap to be put back on, since we've now gone from a cored structure to one of solid laminate. In other words, the top cap is now replaced more for cosmetics than anything else.
I don't think I need to go that far, but may choose to simply because it will eliminate any chance of water intrusion into the deck core from the windless and pulpit hardware ever again, as that entire sectiion of the deck would then be solid fiberglass. Indeed, if you look at how backing plates for cleats and such are laminated into the rails, this is exactly the strategy that is undertaken and WHY. You'll rip the entire rail off the boat before you'll lose a cleat.
I can cut the bottom out and do the repair from underneath (there's room in the chain locker), but that has its own problems. One of them is getting intimate core contact with both skins, without which strength is radically reduced. Voids cause structural problems and can result in failures over time. If I go with a full laminate lay-up replacement then the option to do this all in place and shore it up while it cures does not exist because laying more than two or three layers of glass at once results in overheating of the resin during the cure and great reduction in strength. As such if I'm going to do a complete fiberglass restoration, rather than replace the core, it has to be done from the top because that is the only way to insure that the laminate components remain in contact while the epoxy cures.
Gravity works against you when working from the bottom. From the top, gravity works for you.
Anyway, whadda 'ya think with the additional info and cheezy drawings?
... is coming out all the way forward to very close to where the caprail is molded in (basically to the end of the core), in the outline of the pulpit's "print" on the deck. The core at the windless switches (to each side of the pulpit) is visible from below and is sound and dry, so I know that the damage does not extend beyond that point. That core area is going to get soaked with CPES and epoxy during this process, however, so it won't become troublesome in the future.
So yes, it will indeed be where you're talking about.
However, let's think this through.
Right now, there is ZERO core rigidity in that part of the foredeck. Zero. HAND pressure on the deck under where the pulpit was is sufficient to deflect the deck 1/4" or more from the top of the laminate. I don't dare STAND on it, as I suspect I'd end up in the chain locker.
That's how weak it is now.
This was NOT obvious until the pulpit came all the way off! Indeed, I thought this was confined to the area immediately surrounding the windless bore. Its not.
Most of the strength of the deck is from the truss-like arrangement of the core and two skins, and depends on the bond between each layer of skin and the core for strength. The skin itself is not flexurally strong; indeed it has a great deal of flex. While it is true that the skin provides strength, that strength is in tension - where fiberglass has GREAT strength. I am not going to butt-joint the piece when it is replaced; I am going to make a "V" joint and lay a couple of layers of cloth over and into it, epoxying the joint in place and effectively making a scarf joint with roughly a 5-10:1 aspect ratio. That joint should exceed the strength of the original piece of deck by a substantial margin as it appears that the deck skin itself is one layer of mat and one of roving, and is certainly not more than 1/4" or so in total thickness. In addition the joint can 'stand proud' somewhat since it will be under the pulpit when complete and as such does not need to be fair with the original deck surface. There's no way that's coming apart once its completed.
Further, the entire core area extending well beyond where the deck skin will be penetrated will be saturated with epoxy and allowed to harden. This sort of treatment produces a rock-hard substrate with structural rigidity all on its own, especailly if you use plywood for the replacement core and fill all gaps with structurally-thickened epoxy. The ultimate strength of this section of deck even without the top layer of skin back on it will likely exceed that of the original construction. With it, the strength will be radically higher than as originally built, as the load will be distributed over the entire deck out for a foot or more from the original mounting point.
Restoring the original design strength is a matter of restoring intimate adhesive contact between the core and BOTH skins. This restores the truss design and thus the deck's strength. The issue with deck core deterioration is as much the disbonding of the core from the skin as the rot - that's what destroys the strength.
Consider the deck as something like this...
===============
core core core core
-------------------
And its rotted end-to-end.
OK, what we're going to do is this:
=== ===
------------------
All dug out.
Then...
=== ===
plywood | plywood
------------------
Where the pieces that are fit BETWEEN the pieces of deck skin are coated with epoxy thickened with microballoons, so as to form a structural adhesive, and the plywood itself is first resin-infused. The gap between the pieces (necessary so we can insert it in the recess) is likewise filled with structural epoxy, and the plywood bonded to the sound core on both sides with filled structural epoxy as well.
Now, what we've done is re-created the original truss, and likely stronger than the original deck even without the cap piece, because the plywood, infused with the epoxy and all bonded up, is actually a structural material itself (the balsa that came out was not!) We now put it back together as thus:
___ ___
===|=======|===
-------------- <<< Cloth tabbed under edge
plywood | plywood
-------------------
That ain't NEVER coming apart. I'll bet any other part of the deck fails first. In order for that part of the deck to fail the new core would have to disbond all the way around from the top and bottom skins extending under the cut piece AND the tabbing on both sides has to fail; otherwise there's no way for it to move. That ain't gonna happen, especially using epoxy which is radically stronger than the original polyester resin used to build the thing.
The other option is to build the laminate from the inside skin to deck level out of alternating roving and mat layers of fiberglass, much as if I was laminating a hullside or bottom. If I go this route I'll end up with a deck section that will be nearly 1" thick (!) and which is effectively tabbed into the existing deck structure on all sides around, since the roving and mat sections would be inset into the deck skin on all sides by a substantial amount, and bonded to the core and skin all the way through. That would produce tank-like structural strength, but it is also radically beyond what was originally built and in fact is getting fairly close to the kind of layup schedule one would find in a hull bottom!
That would look like this:
=== ===
Gap where core removed
-----------------------
=== ===
++++++++++++++++++ << Roving/mat layers built up
-----------------------
And then we top it with the original deck
===|=========|====
+++++++++++++++++
----------------------
The latter would be crazy-strong and likely wouldn't even require the top cap to be put back on, since we've now gone from a cored structure to one of solid laminate. In other words, the top cap is now replaced more for cosmetics than anything else.
I don't think I need to go that far, but may choose to simply because it will eliminate any chance of water intrusion into the deck core from the windless and pulpit hardware ever again, as that entire sectiion of the deck would then be solid fiberglass. Indeed, if you look at how backing plates for cleats and such are laminated into the rails, this is exactly the strategy that is undertaken and WHY. You'll rip the entire rail off the boat before you'll lose a cleat.
I can cut the bottom out and do the repair from underneath (there's room in the chain locker), but that has its own problems. One of them is getting intimate core contact with both skins, without which strength is radically reduced. Voids cause structural problems and can result in failures over time. If I go with a full laminate lay-up replacement then the option to do this all in place and shore it up while it cures does not exist because laying more than two or three layers of glass at once results in overheating of the resin during the cure and great reduction in strength. As such if I'm going to do a complete fiberglass restoration, rather than replace the core, it has to be done from the top because that is the only way to insure that the laminate components remain in contact while the epoxy cures.
Gravity works against you when working from the bottom. From the top, gravity works for you.
Anyway, whadda 'ya think with the additional info and cheezy drawings?
