Keel stub repair - a few questions.

[Kopite]

Hi,
I torqued the keel bolts on my '84 27' after seeing a small crack ( no width, about foot long) had appeared on the port side of the keel when I pulled for the winter. I found that all of the keel nuts moved before 75ft lbs, but that front one wasn't coming up to torque, so I stopped turning, but did notice the glass had cracked around it, and water magically appeared around the washer. Obviously the core is wet and/or rotten, so I'm thinking it's time to remove out the plywood core.
So, I've done my research, but I'm also hoping for some helpful advice from the knowledgeable folks on the forum..
1) Should I repair with expoxy or polyester ? I'm planning epoxy, as I want the best vs cheapest, and that seems to be the concensus. How much epoxy will I need ?
2) I need three layers of mat and roving per Catalina directions. Can I lay it all in one sitting ? I have worked with glass before many times, but not 6 layers !
3) I can heat the boat inside (electric heater) to do it over winter, and let it be warm long enough that the even the bilge should be warm, especially if I give that area a boost with my heat gun. I'd use a fast cure hardener. Assuming I get the temp above 50F, are there other concerns I need to consider with the winter work ?
4) I'm a bit concerned on what might happen when I remove all the keel nuts. The boat is on a cradle of the prescribed design for the boat, with therefore ( I assume) 70% of the weight on the keel. Do I need to worry about the boat popping up off of the keel ? In any case, I'll clean up the the plywood first in the open areas without disturbing the bolts, and do the area under the bolts only when I'm ready to glass...
BTW I'm in fresh water and the bolts are in great shape.

Any advice on this or any other points would be great !

Thanks,
Andrew

 

[richkish]

Use Epoxy. I did same repair this year to 1987 Cat 27. You will not be able to do all layers at one time. Ground out crack then filled with thickened epoxy with cabosil. Then used 2, 4, 6 and 8 inch tape.

 

[Kopite]

Hello richkish, do you mean you did the core replacement or just the keel crack ? I'm most interested in the core replacement.

To all, as an addition, to build back the depth of the material lost from the core, I've located a suitable piece of 1 1/2 inch thick G10. This will obviously be very stiff. Any concerns is using this approach ? I would plan to set it in epoxy and then do the 6 fiber layers above it.

 

[Kopite]

Update :
I took a core sample by drilling a 3/4 inch hole. The wood is wet but not rotten, although from my torque test I know it is soft.
I'm still planning to pull it out so I can prevent the inevitable issues that are in the future.
A bit of research tells me that G10 at 1 1/2" thick will be very hard to cut to shape, so I'm back to the Catalina method...will be clearing most of the core over the holidays...

 

[CloudDiver]

Kopite, can you post pics? I wasn't aware that there was any core material in the keel stub of a C-27. To my knowledge, which isn't all encompassing of course, most manufacturers stopped using core materials (especially plywood and balsa) below the water line by the early 80's... that obviously can vary between different brands. Whatever the case, for sure use epoxy in all structural repairs, it has way better strength and secondary bonding vs polyester resin. The only place I ever use polyester resin is in non-structural cosmetic repairs where new gelcoat will be needed because gelcoat does not like epoxy. I would get rid of the wet wood for sure as you plan but I think G-10 is a good idea. I've never cut a piece that thick (1.5 inch) but I don't see why it would not cut on a band-saw with a metal cutting blade... I cut 1/4" thick steel that way.

 

[Kopite]

Yes, my boat is an early '80's (actually 84) so it is wood. Catalina's recommendation is to remove the core and then replace with 6 layers of glass - i.e. No core. Most folks say G10 dulls blades quickly, unless diamond or carbide. Can be cut with a cutting wheel on an angle grinder but very dusty/smelly, and I have a difficult shape to cut. I think a diamond (tile) blade on the jigsaw my be the best bet, but is a slow process.
My concern was that the wood core is somewhat compliant, and hence spreads the bolt loads, whereas the very stiff G10 might cause some local high stresses in the existing glass work..

 

[CloudDiver]

Yes, the wood core being compromised (soft) would allow the fiberglass to flex, all around bad news. What you are saying about the G10 causing local high stress cracks is not correct, the G10 plate would distribute the load of the keel evenly through the structure it is bonded to. 1.5 inches sounds way too thick anyway. The only thickness you need to re-build is whatever is removed of core material and glass. If the Catalina 'factory fix' is only 6 layers of glass matt I hope you are talking about woven roving.... The glass I have been working with lately is 8.5 oz and it takes 24 layers just to reach 1/4" thick.
The whole point of a keel stub is to be stiff where the keel joint is. A fin keel that connects directly to a hull only works when you have a super strong floor grid in the hull... many modern yachts are making these from laser cut stainless steel. That floor grid transfers the forces on the keel into that floor grid which spreads the load to the entire hull, rather than flexing at the keel/hull joint leading to leaks and sometimes tragic keel failures. A Keel Stub design is meant to not flex at the joint at all which is 1/3rd the way down from the hull. As an integrated part of the hull laminate the keel stub transfers loads by being connected to the hull over a very large surface area. The core you find in your keel stub is more correctly call 'deadwood', which is what they called the thickest part of the keel in wood boat construction where the keel bolt holes would be drilled. Its purpose in fiberglass construction is less structural and more to spread the clamping load of the nuts and washers on the bolts. When it rots it allows movement, flex, and blah blah blah we know the rest.
The patterns for the C27 keel are all over the web. I have a 1/2 sheet of 1/2" marine grade plywood left over. If you want a new piece of core let me know and I can cut you some blanks from a template, making them a little bigger so you have room to sand and shape them as needed. You can epoxy and clamp 2 or three together to get whatever shape you need and epoxy it in place, cover with a few layers of cloth. When you re-drill the keel bolt holes just over bore size lightly and pot them with epoxy and never have issues again. Let me know, its not too big of a deal for me to zip off a few in the band saw.

 

[CloudDiver]

For reference, check this post about the same job only done on a Catalina 30;
http://forums.sailboatowners.com/index.php?threads/weeping-keel.159748/

 

[CloudDiver]

The though occurred to me last night, why not make your own fiberglass board? I use this method with scrap glass cut-offs to make backing blocks and such. I lay out plastic on a flat surface, wet-out several layers of glass, cover with another sheet of plastic and then a thick board and add the weights (I used heavy marine batteries). Once you have removed the wet core wood and have a template of the keel pocket, make a fiberglass board from woven roving by laminating several layers. It will be relatively easy to cut and trim, or at least easier than G10. Epoxy that in first, and then you go over that with a few more laminations that tab over and up the sides of the bilge. 6 layers of 24 oz woven roving should yield just over 1/4", 10 layers will be about 1/2". For laminate schedule, about .043 inch per layer of 24 oz woven roving, give or take.

 

[Elysium_Van_Isl]

Vader's got you on the right path for sure, and the link over to the C30 thread will show you all you need. I agree with building up the glass separately, then cutting it to fit the ground-out bilge. I too have done this whenever making backing plates, etc. I use a combo of chopped strand matting and heavy (17oz) biaxial cloth. Just make a big 'sheet', and then cut it and stack them. 24oz is great too, just make absolutely sure you get it fully wetted out.
Also - make sure your keel is double blocked (or at least blocked DEAD CENTRE) to ensure the pressure is even!

 

[Kopite]

Thanks all ! The core is 1 1/2 inches thick, and replacing this thickness would help me avoid the nut/keel interference issue as it will bring the nuts back to where they were originally. I don't really want to put wood back in - like the C30 owner, I want to fix the thing permanently. Catalina specs the cloth to use, I think it was 24oz roving and 1.5oz mat alternating. I could just keep going with that, a core is not mandated, just a lot of layers to lay.

 

[Kopite]

Well, work is underway and going well. For removal of the glass layer my vibratory tool with a carbide tile cutting blade works great - and my craftsman has a hook up for the vacuum, so there's not even any dust. For the tight areas I bought a very cheap Chinese "Dremel" with a flexible extension, and a carbide Dremel bit. That's a bit slower, and does make dust, but as the areas are small it's ok. To cut into the wood I'm using the vibrating tool with a wood blade, and then chiseling out.
Tools
.
Floor protected, some wood removed.

The wood is wet, smells like red wine from the fermenting..

 

[dive7mmwet]

no way is the wood core 1 1/2 thick your digging something else out not wood,get all around them keel bolts , more like 3/4" marine grade, been there done it on our web blog see it all, its a mess job do the mast post compression post block ahead in the keel area! while your at it and use starboard as we did, never will rot and anyone that uses wood in a boat today should go work for the Russian space program way old school! use Catalina's specs as found on web, and yes you will lay up all the matt/roving at once layer by layer , get err done so when it hits its all set at once no need to re prep, sand and prep over.

 

[Kopite]

Hi, just to save confusion for those following, the wood might have been 3/4 on your '82, but for sure it's 1 1/2" on my 84. I did see your blog thank you, all info. for has been very helpful..

 

[dive7mmwet]

cool Id bet from Cat 30's I have Supervised a rebuilt on some one did a lazy rebuild and dropped and glassed a mold in over top of bolts seen this done with aluminum, one boat Stainless steel plate! PO was a manufacture of SS parts ,this approach never solves the problem of water intrusions from inside and out side and the rotten original keel stub board still compresses and causes more sag and compression! good luck,,

 

[Kopite]

It warmed up here and so could get started on the glass work. First had to clean up the glass and resin around where the wood was for which I used a sanding disc on my rotozip, and carbide bits on the "Dremel" for the tight areas. Was able to get it nicely smooth.

I decided to use 6 layers of 1708 with epoxy, going 6" up the sides, and then a full layer of 5/8 G10, followed by 2 more layers of 1708 to close it all in. By cleaning up the side areas well, I was able to keep decent access to the bolts, so no issues getting the washers and nuts back on. First pic is after the first 1708 layers, then after the G10.

Two more layers of 1708 went on the top, with the washers and nuts fitted while still wet, then painted with interlux. Job done.