when to replace bulkheads?

[Jedediah]

Since I noticed someone else broaching this subject, kinda, I thought I'd leap in...under a new thread since it seems a bit different.

My question is this, when is replacing the entire bulkhead required and when should it just be repaired? And if repaired, what is the best way to go about doing it?

Basically the bulkhead has suffered rot in two areas, where the upper's chain plate attaches and right next to where the mast is stepped. I know, you couldn't find a worse place structurally for this to occur. Tapping and prodding on the remaining area seems to reveal that things are in better shape. It is just the 10-12 sq. inches at the upper part of the chain plate and a similar sized area near the deck step/compression post.

I know this should probably be replaced, but the boat is floating, the mast is up and I'm sick of the insulation project which is almost done and I'm ready to go sailing for a change. So, if you ground the area out and filled it with epoxy and glass in a tapered out hole would that work? Or is replacing the whole thing with new plywood (or better yet a sheet of FR4/G10 of some other pre-made structural fiberglass composite) the only way to go? Or perhaps making a bigger chain plate that goes into unaffected wood?

Here's the chain plate area, note the only area I can get a screwdriver to penetrate is halfway up and above on the outside. Below and to the outside the wood has been affected but not as badly.

[Hirilondë]

Is the chain plate really bolted through plywood? Or is it bolted through a fiberglass gusset and the bulkhead is tabbed to the gusset as well as the hull below it? Is the mast deck or keel stepped? If deck stepped is the compression post intact and does it rely on the bulkhead for support? What kind of boat is it?. LOL. I know you wanted answers and not just more questions, but these details may mean you can repair the bulkhead instead of replacing it, or that you are lucky your mast still stands.

[Tim]

It is just the 10-12 sq. inches at the upper part of the chain plate and a similar sized area near the deck step/compression post.

Hmm...only the two most important structural parts of the bulkhead!

Suspect bulkheads are bad enough, but when the suspect area is directly in way of the most critical rigging connections, I'd be a bit concerned. Now, I am not there to see the situation, and it's possible that a temporary solution will work fine--or even that the status quo is acceptable. I can't possibly say with the information at hand, nor could I ever say from a distance whether anything is truly OK.

Typically, I believe it's best to replace an entire bulkhead when the old one contains significane rotted or otherwise damaged areas. No boat is any good if her basic structure is unsound. Again, though, I don't have the information I need to give any sort of unequivocal answer in this case, I'm afraid. But rot in way of your chainplates is of course a serious concern that needs to be addressed, however minor it is.

More questions:

-Are you sure your screwdriver is penetrating punky wood, and not a gap between the actual bulkhead and the hull? Often (too often), bulkheads are cut short of the actual size needed and rely on the tabbing to bridge the gap. Maybe it's a trick of the camera or something else entirely, but at the top, just outboard of your chainplate, it looks almost like the bulkhead ends with a sizeable gap to the hull. But then lower down, below the chainplate, it looks like the bulkhead extends all the way out, so that distinct dark line at the top might be something else entirely.

-Which leads to a follow-up question: if your screwdriver is penetrating outboard of the chainplate, what does that say about the quality of the fiberglass tabbing there? It shouldn't be possible to push a tool through good fiberglass. What is going on there?

-Is that chainplate supporting an upper or a lower shroud? If it's a lower, the overall concern is much less. I suspect it's an upper, though.

-Do the chainplate bolts pass through sturdy tabbing on both sides of the bulkhead? If so, then the tabbing is providing significant support for the chainplate, which might reduce the immediate concern over the condition of the plywood. Still, this is not a situation to be ignored going forward.

-To better know how to proceed, it's really best that you do more investigation into the actual condition of the bulkhead. Maybe you can temporarily disconnect this stay and unbolt the chainplate so that you can get a better look inside the bolt holes. This will speak volumes. The lower shrouds will support the mast pretty well, and you can also run your main halyard to the rail to add some temporary support while you undo the stay. But don't do any of this if it's not something with which you're already inherenty comfortable. Too many unrigging mistakes have been made by well-intentioned folk.

-You might be able to effect an appropriate repair here. Again, it just depends on the actual conditions at hand. I don't think you can proceed in any direction, however, without performing more in the way of exploratory surgery to find out exactly what you're dealing with.

Or is replacing the whole thing with new plywood (or better yet a sheet of FR4/G10 of some other pre-made structural fiberglass composite) the only way to go?

Note that using any solid fiberglass panel, like G10 (an epoxy-based fiberglass laminate), would be far too heavy to use as a bulkhead replacement. This stuff weighs a ton (much more than plywood)--never mind what a large sheet of this material costs.

If you want to use something other than plywood, there are a number of options that are built using some sort of core material with fiberglass overlay. But good plywood still works fine and is the easiest and safest bet for most people. Please don't use the junk from the home center for anything structural.

[Jedediah]

First off before I get to Tim's wonderful comments. No, I haven't found a fiberglass gusset with my minimal probing. I'll look today. There is an extra peice of wood on the backside but it doesn't appear to be covering one. It is a deck stepped mast. It has a solid teak compression post that has suffered much less than the plywood. Yes, yes, I know, its on the list--somewhere on page 10... The plywood appears to provide longitudinal support to keep it from flexing too much side-to-side. But other wise very little until we get to the bottom.

At which point the compression post rests on "The Beam". This is a Cal 29, important fact at this point, which has a steel (not stainless) beam that runs under the main bulkhead. It is attached in two places to the Port side of the main bulkhead via two tabs and to the Stbd side with one tab. This takes the downward force from the compression post and distributes it back to the bulkheads and thus the hull. I guess the keel (fin) is not strong enough to take the load directly, nor is it really where you'd want it since the forces then have to be transfered back to the chainplate anyway (if viewed as a simple torque acting on the hull, which I'm guessing isn't completly correct).

Tim,

1) Yes, the screwdriver is going into the wood. The fiberglass tabing is holding up to moderate pressure although flexing due to a lack of strength below it. The wood, upon close inspection is very stringy and black (I'm assuming the symptoms of wet rot) with very little strength between the fibers in the worst areas. Lower down the teak vinear is pealing away a bit, but the wood under it is not as comprimised. Inbetween the grain is still erroded some, but not completely.

2) It's an upper shroud, lovely eh? I've had it slacked off before to replace the spreader earlier with no problems in the marina.

3) As best I can tell the chainplates don't pass through tabbing. The lower shrouds do, but not the uppers. I suspect this even further because this side (port) has moved about an 1/8" upward and the bolts are all at a slight angle now. If it is tabbed its on the backside from the picture and covered by a 1/4" thick strip of wood, but I'm doubtfull. It seems the bolts just run in the wood. Even if it was on the tab on the backside, that won't do much good when the wood can not resist compression and seems a bad idea.

I'll take the chain plates off when I finish the insulation project later this week. What do you have in mind when you say good lumber? Anything in specific?

Hmm...only the two most important structural parts of the bulkhead!

Suspect bulkheads are bad enough, but when the suspect area is directly in way of the most critical rigging connections, I'd be a bit concerned. Now, I am not there to see the situation, and it's possible that a temporary solution will work fine--or even that the status quo is acceptable. I can't possibly say with the information at hand, nor could I ever say from a distance whether anything is truly OK.

Typically, I believe it's best to replace an entire bulkhead when the old one contains significane rotted or otherwise damaged areas. No boat is any good if her basic structure is unsound. Again, though, I don't have the information I need to give any sort of unequivocal answer in this case, I'm afraid. But rot in way of your chainplates is of course a serious concern that needs to be addressed, however minor it is.

More questions:

-Are you sure your screwdriver is penetrating punky wood, and not a gap between the actual bulkhead and the hull? Often (too often), bulkheads are cut short of the actual size needed and rely on the tabbing to bridge the gap. Maybe it's a trick of the camera or something else entirely, but at the top, just outboard of your chainplate, it looks almost like the bulkhead ends with a sizeable gap to the hull. But then lower down, below the chainplate, it looks like the bulkhead extends all the way out, so that distinct dark line at the top might be something else entirely.

-Which leads to a follow-up question: if your screwdriver is penetrating outboard of the chainplate, what does that say about the quality of the fiberglass tabbing there? It shouldn't be possible to push a tool through good fiberglass. What is going on there?

-Is that chainplate supporting an upper or a lower shroud? If it's a lower, the overall concern is much less. I suspect it's an upper, though.

-Do the chainplate bolts pass through sturdy tabbing on both sides of the bulkhead? If so, then the tabbing is providing significant support for the chainplate, which might reduce the immediate concern over the condition of the plywood. Still, this is not a situation to be ignored going forward.

-To better know how to proceed, it's really best that you do more investigation into the actual condition of the bulkhead. Maybe you can temporarily disconnect this stay and unbolt the chainplate so that you can get a better look inside the bolt holes. This will speak volumes. The lower shrouds will support the mast pretty well, and you can also run your main halyard to the rail to add some temporary support while you undo the stay. But don't do any of this if it's not something with which you're already inherenty comfortable. Too many unrigging mistakes have been made by well-intentioned folk.

-You might be able to effect an appropriate repair here. Again, it just depends on the actual conditions at hand. I don't think you can proceed in any direction, however, without performing more in the way of exploratory surgery to find out exactly what you're dealing with.

Or is replacing the whole thing with new plywood (or better yet a sheet of FR4/G10 of some other pre-made structural fiberglass composite) the only way to go?

Note that using any solid fiberglass panel, like G10 (an epoxy-based fiberglass laminate), would be far too heavy to use as a bulkhead replacement. This stuff weighs a ton (much more than plywood)--never mind what a large sheet of this material costs.

If you want to use something other than plywood, there are a number of options that are built using some sort of core material with fiberglass overlay. But good plywood still works fine and is the easiest and safest bet for most people. Please don't use the junk from the home center for anything structural.

[Quetzalsailor]

Seconding the request for more information... Presumably a similar condition occurs at the other side and maybe at the other chain plates, too.

The aim would be to do a perfect job structurally and an apparently perfect job visually for the least amount of cost (time, money, new tools, etc).

I imagine that spliced-in areas of matching plywood with back-up doublers would be worth considering.

I imagine that increasing the width and thickness of the tabbing to encompass the bolt positions, and adding a covering trim piece on the show side would be worth considering.

One would have to be confident of the condition of the bond between tabbing and wood, and the degree of deterioration of the wood to be enthusiastic about repairing the edges of the bulkhead.

Drying and epoxy saturating the less competent wood is a good thing to think about as well. Saturating the edges and end grain of wood components where they abut something wet is good.

I repaired the front face of a settee using epoxy and body filler. The plywood was 95% real fir marine plywood with melamine faces (ahh the early '70s!), the remaining 5% was punky, somewhat delaminated, melamine exfoliating, or just no longer present. With the settee front out, I dried it, soaked the exposed wood with West. I retabbed it to the hull, filled the thing smooth and painted the whole surface as I painted all the rest of the faux-Teak melamine. 10 years and no evident deterioration.

[Tim]

I haven't found a fiberglass gusset with my minimal probing.

You'd know immediately if this was there; it'd be clearly visible on the exterior. Most boats like your Cal don't have this arrangement, so don't spend much time looking.

The wood, upon close inspection is very stringy and black (I'm assuming the symptoms of wet rot) with very little strength between the fibers in the worst areas. Lower down the teak veneer is peeling away a bit, but the wood under it is not as comprimised. Inbetween the grain is still eroded some, but not completely.

I'm sorry to say that doesn't sound very good. Black, stringy, wet wood is not what one hopes to find beneath their chainplates! You've a repair job ahead.

It's an upper shroud, lovely eh? I've had it slacked off before to replace the spreader earlier with no problems in the marina.

As long as you're comfortable dealing with your rigging, and know what you can and can't do as far as loosening or disconnecting things, you'll be OK. It sure seems like removing that chainplate for further inspection is in the cards. If you end up having to do major surgery or replacement on the bulkhead, you may be well served to unstep the mast anyway, so take this into consideration as you proceed.

As best I can tell the chainplates don't pass through tabbing. The lower shrouds do, but not the uppers. I suspect this even further because this side (port) has moved about an 1/8" upward and the bolts are all at a slight angle now. If it is tabbed its on the backside from the picture and covered by a 1/4" thick strip of wood, but I'm doubtful. It seems the bolts just run in the wood. Even if it was on the tab on the backside, that won't do much good when the wood can not resist compression and seems a bad idea.

I only asked because tabbing on both sides of a bulkhead would help hold the chainplate bolts against the shear load that is placed upon them. But you're saying that your chainplate and bolts are showing obvious signs of upward movement. This confirms that your bulkhead is mush in that area and will require repair or replacement. Chances are I'd replace the entire bulkhead if it were up to me, unless the damaged area was very small and easily (and completely and safely) dealt with. Replacement is the best way to repair it, though not the quickest or cheapest.

What do you have in mind when you say good lumber? Anything in specific?

By "good plywood" I mean any void-free, multi-lamination plywood. I don't believe that the typical 5-lam 3/4" plywood found at the lumberyard is much good for any structural use on a boat. I am fond of Meranti marine plywood, a 9-lamination (3/4") exterior plywood with void-free interior laminations and rated to British Standard 1088. You'll probably find it at a local hardwood supplier.

Yes, you bet it costs more. But anything worth doing is worth doing right, or at least as right as you can with the information you have at the time.

Since you have this problem, please take time to inspect all your other chainplate locations for similar issues. It it happened in one spot, it could very well have happened elsewhere.

Aren't boats fun?

[Hirilondë]

Okume marine plywood meets the highest of standards as well. It is lighter than meranti (in color and weight), but costs more as well. Both of these cost so much because of the manufacturing details and because neither is made in the USA. You get to pay to have it imported as well as manufactured to exacting specifications.

[stone]

Mine are on the sketchy side and wasnt really planning on doing this at this time but since I am waiting for the sixty degree temps its supposed to be to redo my roof .I thought I would try to keep the cause rolling. Today was actually sixty so I knew if I removed yesterday I could re-install today. Also for me since I am redoing my roof I Have cut out a liitle extra where I can fit down the whole bulkhead. I btw just used 3/4 fir marine ply that I will be putting a teak veneer on top.

[Jedediah]

Thinking more about this and looking at it more I'm beginning to think replacing it would be a good idea.

The only way I could see saving it would be to cut out the outboard 8" and make some form of a cored fiberglass tab off the hull. The remaining bulkhead could then be tabbed onto this. This however does not answer the question of what to do right below the mast step at the top nor about replacing the beam down below.

So, now that replacement is the idea, how is the best/easiest way to go about it? Is it better to totally remove the current tabbing with something like a sawzall? Or is it better to only remove one side of the tabbing with something like an angle-grinder so that you have a reference where to put the new bulkhead? Reassembly on the second option would be something like sand the remaining wood off and put a layer of epoxy down and clamp/screw the new bulkhead in place, then retab the otherside like normal.

Since I'm talking about replacing the bulkhead anyway, how can the chain-plate area be made stronger and more rot resistant? Would it be better to cover that entire area in glass (like a heavier mat like that covers the small bulkhead/ribs for the lower shrouds)? Or just put it back like it is and keep it from leaking?

As for the wood side, sorry wood working really isn't my forte, I have a few more questions. The bulkhead is 4' wide, the companion hatch is only 44" on a diagonal. This probably means it will have to be cut in half vertically since I don't think it would flex enough to get in. What is the best way to rejoin it? Biscuits, dowels, epoxy/glass strips? Or do I take the sawzall to the compainway hatch and make it bigger? Oh, why does that sound like another long project unto itself? I mean really, shouldn't boat builders think about things like this when they're building boats?

Now imagine that the bulkhead is back, glassed onto the hull, has a huge strip of glass down the middle where its joined back together, how does one make it look pretty? If only I didn't care about looks this would be so much easier...but I'd like it to look reasonable. Do you fair the entire bulkhead and glue a veneer of some sort onto it? If so, where does one find 4' wide sheets, which is what it looks like is on it? Or is there a trick I don't know for using the smaller strips that I can find locally(10" or 2')? Or can it be installed in such a way as I can simply use a nice sheet of plywood for the final surface?

[Tim]

Is it better to totally remove the current tabbing with something like a sawzall? Or is it better to only remove one side of the tabbing with something like an angle-grinder so that you have a reference where to put the new bulkhead?

I would typically choose to remove all the old tabbing and install the new bulkhead with all-new tabbing. An angle grinder with a thin cutoff wheel will work much better than a Sawz-All, but if you do use a Sawz-All, be sure to get some carbide-tipped blades.

There will be a clear indication of where the bulkhead was, so relocating it won't be difficult if you remove all the tabbing.

Retaining part of the old tabbing like you suggest is possible, but only if the old tabbing is in very good condition and sturdy. And even though the bond would still be epoxy to wood, whether you "glue" the old tabbing to the new bulkhead or install brand-new tabbing, I'd still rather see new overlapping width tabs in place on both sides.

...how can the chain-plate area be made stronger and more rot resistant?

It won't hurt to extend your tabbing out beyond the chainplate area, so that the chainplates will then be bolted through the tabbing as well as the wood. If you do this on both sides, then in theory the bolts are held by the tabbing, not just the wood, and there will be less tendenancy for the bolts to start pulling through the wood from the shear loading.

If you do this, you'll need a way to hide the tabbing if the area is exposed in the cabin. I guess you could also wrap a piece of glass over the top edge of the bulkead and down over the chainplate area, to encourage any water that entered the deck slot to run over and past rather than soak into the plywood end grain.

But mainly, you just need to stay on top of the sealant in the chainplate slots. Because of the dynamic loads, you really need to renew this frequently. If the sealant remains in good condition, leakage won't be a problem.

The bulkhead is 4' wide, the companion hatch is only 44" on a diagonal. This probably means it will have to be cut in half vertically...

There are a number of ways to make the seam. Maybe the easiest way is to build your bulkhead of two thicknesses of 3/8" plywood, with the seam staggered. Epoxy them together once they're in place.Then you end up with a laminated bulkhead of the original thickness.

Or you can use a single thickness and rout a shallow dado on either side of the seam, into which you secure your tabbing to attach the halves together. This will make the end product flush.

Or cut a 12:1 plywood scarf on both halves and epoxy them together once they're inside the cabin.

There are other ways too. It all depends on your skills, ingenuity, space to work inside the boat, and your desired result.

I don't know much about veneers and will let someone else tackle that part of your question.

[Hirilondë]

The bulkheads in my Renegade were cosmetically a mess and there was a little rot at the sole in a couple places. As none of the rot affected any structural demands on the bulkheads I had but 2 issues to address:

1. stabilize the rot
2. cosmetically rejuvenate them

The way I dealt with the cosmetic aspect may be of interest to you Jedediah.

After I stabilized the rotten spots, or in your case after you install the new structural bulkhead (pieces tabbed together, scarfed together or whatever you decide upon) I made a pattern of the entire bulkhead. I used 2" wide strips of doorskin plywood (it is about 2 mm thick). I would fit strips along all of the edges of the bulkhead, shaping as necessary each piece and hot gluing them together as I went. I had previously painted the interior of the boat and the tabbing as well. So I made the decorative cover piece a couple inches from the hull and exposing the painted tabbing. Because the cosmetic layer is so thin it looks quite good. I eventually ended up with a perfectly fit skeleton of shaped strips that made up the exact shape and dimensions of the bulkhead. I then transferred my shape onto a piece of 3mm Okume marine plywood. My interior is mahogany, so this was a nice match. You would use a very thin plywood with whatever veneer is appropriate. I then glued this over the old bulkhead using thickened epoxy. The gluing phase is somewhat tedious and messy, but the result is quite good. I used many brass escutcheon pins nailed through small pieces of scrap plywood and then through the new finish ply into the bulkhead to hold it tight together while the glue cured. Then removed them the next day (the tiny pin holes conceal easily). In your case you may have to cut the finish layer in half to get in on board, then glue it on as 2 pieces.

Here is one of my covered bulkheads being varnished:


If you choose to go this route you can concentrate on building a sound structural bulkhead first without worrying about finished looks. Then make it pretty after.

[Tony]

On Solace I had to replace one of the main bulkheads. I used a Sawzall and a Dremel to do the cutting, braced the hull & deck with 2x4's crosswise to keep it's shape and then ground off most of the tabbing, leaving small 2-4" sections every couple feet on one side the bulkhead. These little pieces made it fast and easy to locate the new bulkhead by propping it on the old stuff while I tabbed the other side. Once one side was tabbed with new stuff, I ground off the little bits I had left and tabbed that side with new stuff. It went much faster than when I just ground off all of the old tabbing for a different bulkhead.

Hope this helps.

[feetup]

Jedediah;
Lots of great information here. All I can add is the idea of drilling the holes for the chainplate fasteners considerably oversize and filling them with epoxy, or epoxy chopped glass mix. When it comes time to fasten the chainplates locate the holes from the chainplate and drill a very tight hole, or if there are threads on the bearing portion of the bolt (which there really shouldn't be!) drill and tap. This will give MUCH more support to the plates which are loaded in pure shear, not allowing the plywood to compress above the bolt from the chainplate load.
Perhaps I could add that the loading on the chainplates can easily equal the actual displacement of the boat and the loading of the mast step will be the same, in the form of compression. If you would not be comfortable lifting your boat from the chainplates they aren't sound enough.

Feetup

[Jedediah]

Thanks for the wonderful thoughts. After long thought and a bit more research I think I have to replace the bulkhead--no ifs ands or buts about it. Here's why: On most Cal's (Lapworth) there was this ingenious beam under the main bulkhead instead of stepping the compression post (or mast on some models) straight onto the keel. This did two things that worked incredibly well (except the beam was made of plain steel...). It transfered the loads from the mast back through the bulkhead to the chain-plates. This allowed the keel area to be much thinner and of lighter construction (lighter boat). That means however, that my lovely rotted bulkhead is more structural than normal from what I can make out--read "oh great". I came across some lovely pictures of the bulkhead failing under the sheer stress of the chain plate on a Cal 34 I think--impressive failure I hope to avoid.

So, I started thinking of trying to calculate the loads in this area and decided it was a lot. Without knowing the exact center of mass of the boat and of the keel and the weight distribution and max expected rotational acceleration forces from the mast I prefer to accept FeetUp's approximation of it's a lot--see I knew I was on the right track... So what is the strength of plywood? I'm guessing that Lapworth worried about this at one point, but not being a wood expert it seems a rather weak link for a very integral part to me. Or is a sheet of plywood stronger than I give it credit for?

Off to get an angle grinder and start tearing into this. Will put the pictures up as it goes...hopefully shorter than insulating a boat...

Oh, and thanks for the suggestion for leaving a few alignment tabs Tony. Seems like a great idea.

[Hirilondë]

So what is the strength of plywood? I'm guessing that Lapworth worried about this at one point, but not being a wood expert it seems a rather weak link for a very integral part to me. Or is a sheet of plywood stronger than I give it credit for?

Meranti or Okume marine plywood is incredibly strong when installed appropriately for the loads it will be subjected to. I don't know how much credit you give it, but I suspect you don't give it nearly enough.

When plywood is used as part of the system to deal with compression loads from a deck stepped mast additional support (compression posts) are called for as plywood has a tendency to buckle as it is a 2 dimensionally stable material. But when it is in tensil load it does an incredible job of drawing strength from its entire surface and transfers the load over a large area. Couple this characteristic with a good tabbing joint to the hull and the strength is quite amazing.

[Gary M]

Jedidiah, I had the same problem last spring on a 30 footer that I had just purchased. I replacedthe entire bulkhead at very resonable cost and it is now like new. I used a sawsall to cut out the old and then did a lot of grinding to smooth out the hull where the bulkhead had been glassed to it.
I also of course had to grind off the paint about 1 foot back on each side so it could be glassed over.

I used a large sheet of cardboard to make the new pattern and then took this to a boat yard where they cut out a new 3/4" piece out of teak covered marine plywood. They had a pro come down and do the actual glassing in which I helped with.

When the bulkhead was out I cut out the bottom portion of deck around the chain plate which had wet coring in it. We then glassed in some new corring and fix it properly. Actual cost was less then $500 but the boat yard treated me pretty well.
Here is a picture with the under deck repaired and ready for the new bulkhead.

Did I mention how much fun all that grinding on the hull was. :)

[Jedediah]

Thanks for the info guys. This was indeed an easier project--except for the dust everywhere...

A few additional bits of info:

Wood Strength Specs: here

Project picts (most are up): here

I didn't end up leaving any tabs of tabbing behind for later alignment and still managed to get it back within 1/8" for the chain-plate alignment--think my sheet was warped slightly different than the one used 35 yrs ago. Angle grinder was faster than my thinking...

Found some "cheap" teak veneer at Rockler in 12"*19" sizes and will try installing that tomorrow--the rotary dug fir just doesn't look right with the rest of the teak in there... Ok, so I should just paint it, I know.

Who puts a 3/16 bolt in a chain-plate drilled for 3/8? Was amazed to find no hole elongation.

And most importantly, any ideas on the best way to remove dust? Besides not generating it in the first place? :)

[Tim]

That looked pretty painless. So it seems that there was no problem getting the whole bulkhead out and in in a single piece, despite the earlier concern? That's good news.

Three layers, staggered by 1", of 6.5 oz 4" fiberglass tape.

If your widest tabbing is only extending 2" onto each surface (you say you used 4"), I would suggest that some wider tabbing might be prudent. Perhaps you're just replicating what was there originally, which I can't really fault. From the photo of your old bulkhead, it looks like the original tabbing was pretty minimum.



Still, on a structurally important piece like a chainplate bulkhead, it's nice to extend the tabbing a bit more. A nice laminate schedule is layers of 4" width, 6" width, and 10 or 12" width as a final piece.

6.5 oz. cloth is pretty light, so a couple additional and wider layers wouldn't hurt here. Also, in a 90? material like the cloth you used (with fibers running perpendicular to each other), only half of the material is actually spanning the seam between bulikhead and hull, since half of the fibers run in line with the seam. For future reference, a 45? material, such as 1708 biax (I think you guys on the left coast often call it Xnytex or stitch mat) is a better choice, since when it's installed all of the fibers are spanning the joint and make it stronger.

Did I mention I hate dust?

Dust is an ever-present misery in jobs like this. If you can stand the awkward vacuum attachments on tools (I can't), they definitely help reduce the dust, but nothing will eliminate it. And the attachments often get in the way in tight areas, meaning that they can't be used at all. When working in a specific area, with other semi-finished areas around, it's usually worth it to segregate the work area with plastic to keep the dust relatively confined. Fiberglass dust is extremely fine and gets everywhere.



It's amazing what you find in boats!

Sure, just grab anything that sort of fits.

[Jedediah]

The bit of modification to the companionway hatch was well worth the effort. Didn't realise you were that serious about pictures Tim, could have saved you the effort of linking them if I'd have known.

The tabbing extends about 3 inches on either surface--staggered an inch per layer and three layers. It was a good deal more than the original tabbing, and everywhere on the bulkhead unlike the original. I thought about the 45? cloth issue at one point thinking I might try to put some pieces of 90? cloth in at a 45? angle, not realising that such a product was made, but forgot by the time I was installing it--need a memory upgrade.

It seemed strange to me that the main bulkhead was glassed in so lightly while the lower shroud bulkheads were glassed in with something more like 24 oz cloth. My guess is that the hull is fairly thin there and the bulkhead itself should be taking the tension load up to the chain-plate, not the hull with the beam below. However, that logic does not sound a foolproof as yours Tim of making it bulletproof. The good news will be I know how to fix it when it fails...

That looked pretty painless. So it seems that there was no problem getting the whole bulkhead out and in in a single piece, despite the earlier concern? That's good news.

If your widest tabbing is only extending 2" onto each surface (you say you used 4"), I would suggest that some wider tabbing might be prudent. Perhaps you're just replicating what was there originally, which I can't really fault. From the photo of your old bulkhead, it looks like the original tabbing was pretty minimum.

Still, on a structurally important piece like a chainplate bulkhead, it's nice to extend the tabbing a bit more. A nice laminate schedule is layers of 4" width, 6" width, and 10 or 12" width as a final piece.

6.5 oz. cloth is pretty light, so a couple additional and wider layers wouldn't hurt here. Also, in a 90? material like the cloth you used (with fibers running perpendicular to each other), only half of the material is actually spanning the seam between bulikhead and hull, since half of the fibers run in line with the seam. For future reference, a 45? material, such as 1708 biax (I think you guys on the left coast often call it Xnytex or stitch mat) is a better choice, since when it's installed all of the fibers are spanning the joint and make it stronger.