Deck encapsulation and tabbing question

[Baylinerchuck]

Hi there i will follow your project im getting ready to do the same with my 18 foot wellcraft ofshore, How will you attach the new floor/deck to the boat stringer?.

You glue it with thickened resin to the stringers. If you use screws to hold it in place until the resin kicks add cleats, and screw into those. Once glued, you then bed the edges and tab it in.

 

[jim_s]

Ok, next round of questions.

I'm nearing the point of needing to start building my new stringers. I'm replacing about a 6' length of stringer on each side - the section that was wet. (I wrestled on/off with popping the top off, and doing a whole-hog, guts-out structural restoration, but the transom test holes were good, and I managed to cut forward/aft into solid wood in the stringers, so the risks of the balls-out, top-off restoration seem to outweigh my interest in doing a full-up structural restoration. (A. the time/expense; B. the chance of introducing a bend/warp in the hull that could adversely affect handling/driveability; C. the chance of introducing enough of a distortion that the top might never go back on)

So, the questions:

1. I've got the stringers cut off with a perpendicular edge at the front and back ends, and my plan is to custom fit the new stringer sections in as butt joints with reinforcing plates on both sides of each butt joint. I've seen most/many pictures and descriptions of this type of joint using a reinforcing plate on only one side of the joint. Is there any reason to not put a plate on both sides? (I don't want to waste my time/effort/materials, if its of no added value, and I also don't want to do it if it might cause a problem - too stiff at the joint?? - but, it seems that both sides make the most sense? Also, should my butt cover plates also be made of 3/4" ply, or would 1/2" ply on each side be good enough? (I'm not at any shortage for plywood - just a question of weight/stiffness in these joint areas - if triple-layered (ie, the 3/4" stringer, then 3/4" plate on both sides, we're talking 2.25" of thickness - just want to be sure I'm not overdoing it to ill effect.)

2. In addition to having to do wood-to-wood joining at the butt joint plates (ie, the side of the stringer glued to the side of the plate), I have a 3' section of the stringer that was doubled up in the original structure. (The stringers are 3/4" ply, but are doubled to 1.5" for about 3' in the middle.) This thread started about encapsulation of the floor - this question is about joining/sealing these wood-to-wood joints. For the double-thickness section of the stringers, as well as the cover plates at the butt joints - should this be direct wood-to-wood gluing? Should I coat both layers with an encapsulating layer of epoxy first (ie, let the epoxy soak into the wood), then glue them face-to-face? Should there be a layer of glass between the faces? I plan to glass the heck out of whatever I end up with, once its in place. (ie, in addition to tabbing to the hull, I'll be running glass up over the tops, to be sure all is thoroughly covered) My plan is to use a peanut-butter consistency of epoxy with milled fibers (West 403), to do these face-to-face pieces, as I've read in multiple places (to include the West site), that 403 provides the strongest bond in this type of situation. Does that sound right?

3. To Limber or Not to Limber... As noted previously, every one of the little compartments under the floor (as created by the stringer/bulkhead layout) was sitting full of wet foam, and this seems to be a large part of what led to these sections of floor, stringer and bulkheads being soaked. The 'plan', putting this all back together, is to make it essentially impossible for water to get into these sections, but its water... It will eventually get everywhere, I'm sure. With that in mind, I'm leaning toward putting limber holes in the stringers for each of these little compartments, so that if/when water does get in, it has a way out. (OTOH, that also provides a place for water to get into both the compartment, and possibly even the stringer), though I'm refilling the compartments with cut sections of pink foam board oriented vertically, so it shouldn't soak up water like the old spongy expanding foam did.) I also plan to not mount the seats through the floor, as was originally done, but to mount them to plates glassed to the top of the floor, which should cut down on what was, I'm sure, a major water entry point. SO, the question... To Limber or Not to Limber??

4. Is there a way to adequately glue/glass in a bulkhead to which you only have access to one side? The rear bulkhead in the interior section (there is one further back - right at the bilge area, that is solid, and seems to have been glassed like they meant it, so I won't be replacing it) lies between the currently-gutted passenger area, and the bilge. There is a section of floor here (on which the gas tank is mounted) that sits under the rear top section of the boat, and is in good shape., and that ends at this bulkhead in question. (I'd have to pop the top off to replace at rear-most section of floor). This bulkhead isn't in bad shape - its not perfect, but its far from rotten or spongy. It could be left in place (with a newly-applied layer of glass on the side I can get to, for some refreshing of its water resistance), but if there is a way for me to replace it, and sufficiently glue it into place, I might well go ahead and do that. The thing is, I can only get to it from the front side. This wouldn't be a big problem for cutting it out, but when it comes time to put it back in, the best I could do would be to lay a huge bead of peanut-butter, push the bulkhead into place, and hope that the PB all stays in place long enough to dry. (I would obviously fillet, tab and glass the front face that I could get to.) SO - do I leave this in place, do the best I can for it from the front side, and just don't stress it (again, its structurally solid - not like new wood, but not falling apart, by any means), or do I cut it out, and perform some type of circus trick to be sure its PB'd in from the rear side? (I guess the other option is, I could cut away just enough of a small section of rear floor, such that I could get an arm down in there behind it, do the best one-armed glassing job that I could from the back through this hole, and then patch in the little cut-out section of floor - I just kinda hate to monkey w/ that section of floor, as its in pretty good shape back there, as it currently stands...) The good news is, this section is under the front edge of the cap, so doesn't receive any foot traffic or such.

5. Between this bulkhead (described in question 4) and the next one up (about 3 feet forward - presently removed), is the section of the floor where anyone getting into the boat steps - whether stepping down in from the dock (which often involves a small hop, given that the boat sits pretty low), or from the rear of the boat (coming into the boat from the water - also often involving a small hop, just because lots of kids come into the boat from the water) This section had an extra layer of wood stapled/glued underneath it in the middle section between the stringers. (not up to the stringers, but in the general area between them) It was not glassed at all - just stapled/glued to the bottom of the floor - I presume to account for this being the landing zone when entering the boat. I'm putting 1/2" marine ply back down in its place (I don't believe the original floor was marine ply, but it was 1/2"), which will be encapsulated and glassed on both sides. My question is, should I replicate the extra layer of 1/2" ply in this section (glued/filleted/glassed), or would I be better off adding another bulkhead in this section, so that there was something spanning the width between the bulkheads in this landing zone? I don't want to introduce some type of 'hard' point in the hull that wasn't there, but nor do I want to go through all of this work, just to end up with a small trampoline in the middle of my boat. I suppose an alternative would be to not put in a full bulkhead, but to glass a block to the insides of the stringers on each side, and have something solid (laminated ply? some type of hardwood?) oriented long edge vertical (like a 'T' beam, or 'I' beam), and spanning the gap (glassed to the little blocks on the inside of the stringers, and PB'd to the floor underneath), but not actually touching the hull, if that might be better from a weight/stiffness/hardpoint perspective. Thoughts?

6. Lastly, I plan to use colloidal silica as filler for my fillets, and ordered some fast hardener for doing fillets and vertical surfaces, as I've read that epoxy wants to run (even when thickened) when applied thickly in fillets on on vertical surfaces. Does this sound sensible? (ie, the silical for the fillet thickening, and fast hardener for fillets and vertical faces)

Thanks Again for all of the help - Now that the guts are out and cleaned up (and now that I finally reached a conclusion on what/whether to do about removing the top), there is a faint light that I think I see shimmering at the far end of a small tunnel. (Its entirely possible that its just FG in my eyes, but I'm gonna say its a light at the end of the tunnel...)

 

[Baylinerchuck]

Wow, that is one heck of a post. Ok, I'll bite.
1. I really don't see a reason why you need a plate on both sides. Just make your joint plate long enough on either side of the joint. Glassing both sides of the joint will make it strong and water proof.
2. Wood to wood gluing is how I would go. I used Loctite PL construction adhesive throughout my project. Many others use titebond III wood glue. Both are waterproof, the PL requires additional time to gas off.
3. Forget the limber holes IMO. I drove myself nuts trying to figure out how to get water out of my cavities. Bottom line, think through how to keep it from getting in there. Seal everything up perfectly water tight you'll never have an issue. Pourable foam fills all the voids and prevents condensation.
4. If it was me, I would glue an encapsulated bulkhead of the same size right to the back of the old one with epoxy PB. It'll be new with in questioned integrity and completely water proof.
5 adding another bulkhead in that area is a good solution. Bulkheads help to stiffen the hull and eliminate twisting. Can't see where adding one would hurt.
6. I'm a fan of poly, so I can't help you. Really can't see spending more money on epoxy. I purchased 20 gallons of resin. That's a lot of $$$ if I was buying epoxy.

 

[jim_s]

So Loctite PL or Titebond III are recommended over epoxy, for the wood-to-wood faces?

I hear you on the poly vs epoxy - if I had it to do over again, I might well go with poly, but I'm now sitting on several gallons of epoxy and related fillers, non-matted glass, etc, so I'm gonna stick w/ the epoxy route at this point, I think.

After the spongy foam disaster of the original flotation, and the widespread damage that it caused by sitting full of water, I'm real hesitant to take that risk again. (Plus, the expanding foam is pretty expensive stuff!) I do worry a little bit about condensation, even if the compartments are sealed well, and I'm not fully confident in anything on a boat being truly sealed, regardless of how much adhesive is thrown down... I'm hoping the pink foam sheet will at least eliminate the chance of soaking up multiple times its weight in water, whether limbered or sealed. The water-soaking nature of the original foam aside, I do think that it added some structure to the floor, just by taking up all the available space. It likely added a fair bit of sound/vibration absorption, too - it'll be interesting to see if the boat is louder w/ the sheets of pink foam under the deck, given that whey won't deaden sound and vibration like the expanding foam did. (OTOH, they also won't be holding multiple times their weight in water, which in itself also probably helped dampen noise and vibration...

I like the idea of just adding another bulkhead right up against the inaccessible one - I hadn't considered that!

Sounds like the extra bulkhead in the landing zone is the way to go - I'll definitely sleep a bit better at night with that!

Thanks!!

 

[Baylinerchuck]

Yes the pourable foam is more expensive, but it provides more than floatation and sound deadening. Since it fills in all the spaces and conforms to the exact shape of the cavity it provides very good structural reinforcement. This foam is a closed cell foam the same as the pink sheets. If under the same conditions, both could potentially become open cell and absorb water. I like the pourable foam because it fillls all the gaps eliminating the possibility of condensation forming. Yes, I recommend PL or titebond III on wood to wood applications. Once glued, and gassed off, ( if using PL), encapsulate in fiberglass. Both are completely water proof.

 

[JASinIL2006]

Titebond III is nice; has same resistance to water as the glue used in plywood, and you don't need to wait 72 hous or more before glassing, like you do with PL.

 

[jim_s]

So, in the process of removing the glass from one of the faces of a good section of stringer (so I could glue wood-to-wood, I got a bit carried away, and tore up part of the first veneer layer of the part of that stringer that I'll be glueing the butt cover plate to. (I thought I was prying away just poly/glass, but it turned out I'd pried away part of that first layer of ply veneer, as well...) So, that particular joint is not going to be smooth face to smooth face. From what I'm reading, it sounds like this might be a place where epoxy would make more sense. (It seems that PL, titebond, etc prefer a smooth/tight joint.) Is this a reasonable assessment? Am I worse-off going with epoxy than these other glues, at least on this particular joint?

 

[Woodonglass]

Epoxy thickened a bit with cabosil would be my choice for making this joint.

 

[jim_s]

Thanks, Woodonglass - that's what my reading seemed to be pointing toward, but its helpful to have someone who's actually done this stuff confirm for me. (I'm really bad at guessing correctly.. ;-)

A number of others have talked about PL, Titebond, etc, as opposed to Epoxy for these butt/plate joints in general. (Prior to my noting that I'd torn up the surface of that one particular joint.) Is the PL or Titebond recommendation based simply on convenience (no mixing of epoxy to be done), or will they provide better joint strength, or are there other real-world benefits? My base inclination is to just use epoxy/cabosil on them all, since I'll be swimming in epoxy at that point, anyway - but if using epoxy on them all is likely to present some significant drawbacks, then I'll definitely look at the Pl, Titebond, etc glues for the other 3 joints.

Thanks All!!

 

[Woodonglass]

Epoxy will be the best strongest and most water resistant. I'd also recommend sistering them together with a layer of 1/4" ply on both sides. I'd use epoxy to glue the plates on with and secure with deck screws. Once the Glass and epoxy go over all this the stringer will be a TANK!!!

 

[jim_s]

Would 1/2" plates do? (I've got some extra 1/2" marine ply)

Also, would clamping the plates in place while the epoxy cures (vs screwing) suffice? I hate the idea of providing any path for moisture to enter anywhere. I'll screw them if that's really the only way to get a solid joint.

Lastly, should the plates go all the way down to the bottom of the stringer. and then be tabbed to the floor as part of the stringer, or should they sit up off the base of the stringer a bit, and not be directly tabbed to the hull? (I'm sort of assuming the first - that the plates should be treated as part of the stringer, and be filletted/tabbed directly to the hull - albeit on top of a layer of peanut butter, so that direct contact between the stringer and hull is avoided - which seems to be a thing.

 

[JASinIL2006]

Going heavier on your plates won't hurta thing. They will just make for stronger joint.

 

[Baylinerchuck]

Carry the plates to the floor. Like WOG stated it'll be a tank. I used PL because it was the most easy to use for me and I used it plenty in the past. Epoxy will be fine if that works for you. No reason to not use screws. Coat them in epoxy before you sink them. Countersink them and apply epoxy covering the head. I use exterior coated deck screws.

 

[jim_s]

Ok, screws it is, then! I've read that when using epoxy w/ cabosil on joints, you want to make them snug, but not too tight, as you'll just squeeze all of the epoxy out of the joint. So, how tight do I screw these screws in? I'd imagine I want to rely on the epoxy for the joint strength, with the screws as backup/clamping, vs squeezing the epoxy out, and ending up relying more on the screws for the strength? (Who'd have thought glueing two piece of wood together could be so complicated?!?

 

[Baylinerchuck]

I want to make sure that I see glue squeezing out from all sides. You want good coverage on both sides of the joint, so use a putty knife and spread a thin layer on both sides. Use the screws to squeeze the joint together just tight enough to get squeeze out all the way around. Predrill your screw holes so the screws don't push the joint apart as you tighten. Dip the screws in resin prior to installing. Countersink the heads atleast 1/8" so you can cover them with epoxy.

This is how I use screws in my project. I used PL mostly on wood on wood joints, so I used a notched trowel to ensure even coverage of glue.

 

[JASinIL2006]

I find it hard to believe you could screw the pieces together so tightly that you'd lose the adhesive properties of the epoxy. Every adhesive for wood I've ever used requires clamping, which is effectively what the screws are doing (in additional to providing additional mechanical fastening, which would also improve if the screws are tight). Heck, if you really want to make the joint strong, you could through-bolt with carriage bolts, but that would probably be overkill.

 

[Woodonglass]

Yeah you could just use clamps if you want. Extreme clamping pressure is NOT required. If you screw em on Predrill your holes and then try to force some epoxy into the holes as well a cover the screws with epoxy. Once the screws are covered with resin and glass you won't be getting any water in the holes. 1/2" is fine Whatever ya got!!!! Don't overthing it...It's NOT Brain Surgery!!!

 

[jim_s]

Ok, as long as I'm not likely to squeeze out so much epoxy w/ the screws, that I end up not getting a good epoxy joint, I'm convinced that the screwing approach can work. (Next overthinking question - drill the plate, and just screw into the stringer (repeat on other side/plate of the stringer), or drill the plate on one side, drill the stringer, then screw into the plate on the other side?? (the stringer is only a 3/4" piece of ply, at the ends where I'm butting it to the existing stringers, so it'll have to be an inch-long screw, if I I'm screwing into the stringer. (1-1/4" if I'm screwing through one plate, through the stringer, and into the opposite plate).

Sadly, overthinking is how I try to compensate for my complete ignorance on all of this. <

 

[Woodonglass]

If you use 1/2" plywood one one side only... I'd use 1" screws. If using on Both sides 1 1/2" screws. Clamp the sisters in place until you have screws in all four corners. Screws on BOTH sides.

 

[jim_s]

Got it! I'll be doing both sides, for sure.