Catalina 30 Keel Stub/Smile

[sastanley]

John...stainless studs? I can't confirm with your pics, but it looks like they are not..My #511 does NOT have stainless studs and they are heavily corroded due to P.O. leaving the bilge wet. I hear that once you knock the old nuts off the threads underneath are usually in pretty good shape, even on mild steel. I have a die, and some SS nuts to go on the studs if I ever do all the work you've done.

I do not know at what hull number they went to stainless. That info is probably available on the C-30 website.

[jbsoukup]

The keel bolts are not stainless steel.

The old nuts were pretty badly corroded on the outside but with chasing the threads before removal and a little heat from a torch, they spun off with no problem.
The threads under the nuts were in what I would call 90-95% condition so, obviously, they're made of a good grade of steel.

Core 10?

She's been in fresh water her whole life and I'm sure that has helped.

So, new stainless nuts and washers and hopefully She's good to go for another 30+ years.

When I get a chance, I'll post some pictures of my bilge in "as is" condition (referring to another thread)

[RUSSELL]

Question as regards materials to use for this repair. I used some Flame-Retardant Garolite (G-10/FR4) from McMaster-Carr for another repair. Very impressive material, quite expensive, difficult to use hand tools on (need diamond tipped blades).

I assume I would tear into this and remove the plywood from both the keel stub as well as the plywood mast compression post block in the bilge.

I was thinking I could use Structural Fiberglass (FRP) from McMaster-Carr rather than the G-10. It is not as strong, but is less expensive and much easier to use hand tools on.

Opinions?

[tenders]

Diamonds are nice but G10 cuts pretty well with carbide-tipped blades. I've used it for lots of stuff - backing/mounting plates, replacement deck after core repair, centerboard handles on a Dyer Dhow - and find it entirely worth the price.

You can buy miscellaneous pieces from Norva Plastics on eBay. Pro tip: you can also call them directly at (757) 622-9281 (Norfolk, VA).

[ndutton]

I think it's important to replace the plywood shoe with another backing plate in the laminate to spread the load of the keel bolts. Fiberglass by itself does not fare well with localized stress points (see winch, cleat and stanchion installations for examples). The Garolite material mentioned is fiberglass cloth based and because of that I think it might not be the best choice for this application.

Worst case, assuming the original adhesive between the hull and keel is no longer a factor after 40 years, you're counting on the eight bolts for everything. The loads are leveraging loads when the boat is heeled under sail and the force upon them is significant. You're looking at 4300 lbs. on a moment arm of at least 2 feet. In making the repair you're considering I suggest a steel plate, maybe even stainless, of say ½" thickness cut to the dimensions of the bilge bottom. In other words, I'd replace the plywood shoe with a steel one.

My 2¢

[hanleyclifford]

2 cents more

Whenever I replace a keel bolt on my wooden boat I always fashion a steel plate to spread the load.

[tenders]

I'm pretty confident that replacing wood with G10 of similar dimension anywhere on a boat will be a structural improvement as long as it's properly bonded to the surrounding area (which may not be a trivial task). G10 is pressed layers of fiberglass cloth and epoxy in an optimal ratio with no voids - it is very tough stuff. Not steel to be sure, but better than wood for all except termites.

[RUSSELL]

Here is my initial (rough draft) plan:

Step 1: Cut fiberglass skin in bilge and dig out all wood down to the fiberglass keel stub floor (same thing goes for the mast compression block). Sand all the area of the bilge with a rough grit sandpaper (e.g., 36 grit). This will be somewhere between 1.5 inches and 2.5 inches of depth of material from what I have read on the web from others doing this task.

Step 2: Layer alternating woven roving and the heaviest weight fiberglass cloth I can find wetted out with epoxy across the keel stub floor and up the sides of the bilge (i.e., inside the boat). Do enough layers to get a thickness of one-quarter inch or so.

Step 3: Make cardboard template of bilge floor and cut the G10 or FRP to shape, including holes for the eight keel bolts. The longest G10 or FRP I have seen is four feet in length, so may require two pieces. If two pieces are required, then alternate the seams. Lay the G10 or FRP into the bilge in a bed of thickened epoxy and weight down evenly, scraping off the excess thickened epoxy.

Step 4: Repeat step 3 until approaching the original bilge level, making sure to sand the surface of each layer level so that there are no lumps to make voids in the next layer. This should take either three or four layers of one-half inch thick G10 or FRP. The mast post compression block in the bilge will be rebuilt in the same manner.

Step 5: Layer alternating woven roving and the heaviest weight fiberglass cloth I can find wetted out with epoxy across the stacked up layers of G10 or FRP to make the new bilge bottom. Do enough layers to get a thickness of one-quarter inch or so.

Step 6: This is where I am not quite sure I am following the conversation above. I think what has been pointed out is that at this point I want to make another cardboard template and then cut a piece of stainless steel to shape with holes for the eight keel bolts. Or, did I want this plate embedded down between the layers of G10 or FRP? Also, are we thinking that this plate needs to be one-half inch thick? This plate would get embedded down with thickened epoxy, evenly weighted.

Step 7: Let everything harden up well - couple of weeks at least. Torque keel bolts to factory specs. Use stainless steel nuts/washers the length of the bolt.

Step 8: I could also add additional stainless steel lag bolts at this point.

Step 9: If the Dutton bilge arch becomes available, then add at the next winter haul-out.

Opinions?

[ndutton]

It's interesting that Catalina's published remedy does away with the plywood shoe and replaces it with only glass work. It begs the question, what was the plywood shoe about in the first place?

You never know what lies beneath the line of vision once you start digging into the bilge. Be prepared for a plan B just in case. Here are a few pictures to disturb your sleep:

[RUSSELL]

Ok, thanks for the nightmare fodder, Neil!

To your point, yes, why was there a big plank of wood there? The Catalina factory fix makes me think it was just to save money rather than using more fiberglass. I am not enough of an engineer to know otherwise.

Regardless, I like the idea of the metal plank. Can stainless steel be wholly encased in fiberglass? How about 3/4" or 1" aluminum?

By the way, with your nightmare pictures, would you not be S.O.L., even if the Dutton arch was readily available?

[ndutton]

By the way, with your nightmare pictures, would you not be S.O.L., even if the Dutton arch was readily available?

The floors - arches as you call them - do not attach to the existing bolts. They are bolted to the keel with 3/4" x 12" stainless lag bolts, 2 per floor except for the forward most, it gets only one and it's a little shorter. The floors system is completely independent and supplemental to the original factory attachment scheme.

The holding strength of the lags into lead was calculated using 10" lags embedded 7". It turns out 12" lags are less expense than 10" so in practice I'll exceed the calculations by roughly 28%. Further, the calculations were based on pure lead and external keels are typically cast with 5% antimony making the lead even stronger. Calcs exceeded again.

The wood shoe was there to spread the load as I described earlier. They weren't the only manufacturer to do it either. The bigger question I think is why is a backing plate not included in the repair? Stainless can be fully encased but I'm not sure there's an advantage to doing so. The ½" thickness was merely a seat of the pants suggestion by me. If considering aluminum, you're getting into dissimilar metals and galvanic cell territory with the steel keel bolts because there's little reason to expect this area of the boat to be dry.

[RUSSELL]

Well, the factory repair sheet may contain opportunities for improvement.

OK, so a steel plate. The keel bolts are not stainless steel, so galvanic concerns would arise, would they not? However, if not expected to be dry then steel other than stainless would rust, correct?


I seem to recall there is a metals interaction chart - the goal would be to get the metals with the least interaction, correct?

[edwardc]

... Here are a few pictures to disturb your sleep:

Its pictures like these that make me so glad my keel has an internal encapsulated ballast!

[ndutton]

Correct on all accounts. There is no clear solution with the various metals involved so you have a decision to make after gathering as much information as possible. We have a galvanic series reference in the ABYC/USCG Standards forum category. I reviewed it this morning and it looks like an aluminum plate with careful attention to alloy selection may be your best option.

Regarding Catalina's aging boat repair directives, I recall we've been there before. And as we deal with a factory installed rotting plywood shoe, please remember it has served its purpose for nearly 40 years. I'm not suggesting it but we could put a fresh plywood shoe in there - eliminating the metals issue - and get another 40 years out of it. Where will we be in 40 years?

Its pictures like these that make me so glad my keel has an internal encapsulated ballast!

True dat but it limits keel design. The move to external ballasted boats in favor of refined keels was driven by racing afficionados who carried the boating industry for decades. That said, when it came to building a boat for my personal needs I chose an ultimate full keel cruiser with internal ballast, 7,000# of it on a 32 footer.

[hanleyclifford]

Well, the factory repair sheet may contain opportunities for improvement.

OK, so a steel plate. The keel bolts are not stainless steel, so galvanic concerns would arise, would they not? However, if not expected to be dry then steel other than stainless would rust, correct?


I seem to recall there is a metals interaction chart - the goal would be to get the metals with the least interaction, correct?

One way to beat the galvanic rap is to encapsulate the stainless bolts in thickened epoxy (before assembly) and then carefully install them to maintain the isolation except at the threads. I have also successfully used schedule 40 PVC as a "sleeve" to isolate a keel bolt in the plank.