Looking for advice on Keel repair...

[NahanniV]

Originally Posted by jimbunyard

If I'm understanding your pictures, the transverse crack that is letting in the water is about 3 feet forward of the compression post base. If that is correct, I agree that the keel had an abrupt encounter with something immovable, and was not repaired adequately.
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Yes, it's at least three feet forward of the compression post.

Originally Posted by jimbunyard

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I think the repair approach outlined above is pretty good, on the inside I would only remove enough glass to get to well saturated material, taper it well, and put in layers to equal 1.5 to 2 times the hull thickness in that area. On the outside you're kinda limited by fairing requirements, but I'd try and grind enough off to get at least a couple of layers of biaxial on, well feathered in.

The area with the crack is quite sharp and thin, the leading edge of the keel gradually gets more of a blunt round shape further down, so I think I could actually add some layers and still be able to fair it.

Originally Posted by jimbunyard

It looks like the compression post step sits directly on the keel. That is good if it is so. If you want to replace the existing one with G10 or phenolic, and make it removable, I think you might have rigidity and strength issues. If you want to build it in permanently, probably not so much, but it will need to be well thought out.

Alternatively, you could just copy the original in aluminum, stainless, monel, or even just plain steel (the one you have doesn't look that bad), and not have to re-engineer anything at all....

I don't understand your comment about rigidity. The current steel compression post base is held in position by four bolts that are welded into the bottom plate and sit in holes drilled into the floor pan. The bottom of the cup that holds the compression post is three inches off the floor pan. So, my thinking is to use three pieces of 1" material the same shape as the base stacked on top of each other glued and bolted together. To replace the cup I would glue and bolt a circular piece that would fit inside the aluminum compression post (tube). See the attached sketch. I would welcome your comments.

Cheers,
JM.

[OceanSeaSpray]

Biaxial is quite nice to work with, but it is not stronger. It is a common misconception. It is not just the fibre-to-weight ratio that matters, it is the ratio of long straight fibres to weight and in the case of woven cloth, there are only long straight fibres.
Mat acts as a cushion and blotting paper between the layers, with very little strength. Biaxial+mat can have better flex properties, but lower tensile strength. It is not as bad with heavy biaxial+mat as the mat gets comparatively thinner.

Either way would work here since there is plenty of space for building up the thickness inside.

It is more difficult not to make a resin rich laminate and still bond it properly when it is not layered in place. Occasionally access/location are so difficult that it is just about the only way, but I would keep well away from it.

[pcmm]

Originally Posted by OceanSeaSpray

Biaxial is quite nice to work with, but it is not stronger. It is a common misconception. It is not just the fibre-to-weight ratio that matters, it is the ratio of long straight fibres to weight and in the case of woven cloth, there are only long straight fibres.
Mat acts as a cushion and blotting paper between the layers, with very little strength. Biaxial+mat can have better flex properties, but lower tensile strength. It is not as bad with heavy biaxial+mat as the mat gets comparatively thinner.

by your own definition biaxial is stronger. woven roving has crimped fibers in both directions or very few straight fibers, where as biaxial is only straight fibers in both directions, yielding a stronger stiffer structure for the same volume of glass resin. biaxial in this application is much easier to work with and yeilds a better, stronger finished product for minimal extra expense. why not use newer stronger easier products to make the repair. the stitched toegther nature of biaxial makes it very easy to work with without the need to add filler at the end to fill the weave. apply the patch,cover with peel ply and smooth it out. when it cures and you remove the peel ply there will be very little sanding to do to get a smooth finish.

use the technique you're comfortable with but the WEST technique makes the job very neat and strong.

[jimbunyard]

It's something of a moot point since the hull is already cracked, but the reason I think that there is no inherent weakness in the hull at that spot is, besides what looks like general good design, the crack doesn't appear to have worsened in three years. Maybe, maybe not...at any rate, it does appear to have been previously repaired.

I think the main functional component of the repair is going to be inside. If it were me, on the inside, I'd go with 18 oz roving laid in piece by piece, wetting out and rolling the air bubbles out as I laid them in. Tape over the crack on the outside to keep the resin in the roving before you start. On the outside, get as many layers of biaxial on as you can, but don't thin the existing glass excessively. You're probably gonna need some silica mixed in with the resin to keep the biaxial saturated until it kicks.

Forgot that we're talking about a compression post and not a mast. My concerns were that you were going to try and fabricate something like the existing step out of G10 (which would be a nightmare), and also that you'd be dealing with deflection at the base of a mast. Your diagram shows a better than original all round solution, and I think it will work very well.

[Nicholson58]

Your one-stop shop for roving, heavy stich-mat, fillers and epoxy. This is all I ever use any more. Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.


I buy the 3-gallon sets of 635 THIN epoxy resin 2:1. Get the pumps. Excellent wet-out. Use stich mat for high conformability to extreme shapes. On vertical and up-side-down (hanging) applications I find two max layers of heavy matt is all you can do without loosing it. Use high cuff rubber gloves to apply a pre-buttered sheet of glass. Smooth out against the surface to make it tac in place. Apply a layer of release film (lay flat a garbage bag). If you use a thing, white or clear bag you can see the work under the film and can see to smooth out bubbles. The film also keeps air from getting back in. A dry cleaner bag works too. The 635 resin is marine grade. No blush, very slow cure. You can clean it from your skin with FAST ORANGE hand cleaner until it begins to cross-link (2 to 6 hours)

I used this to repair damage to our encapsulated keel from a rock. It took many layers to fill a 2-1/2" thick chunk ripped off the bottom of the keel. You can see the film applied to seal out the air.

[Don C L]

All sounds good but I was thinking about your original post where I believe you said that when you applied the compression force, the crack began to leak. I am a little skeptical that even a well-made patch will sustain the forces on it, but I certainly could be wrong. I know it is a small crack. I understand the mast base is 3 feet from the crack, but it sounded like the force was great enough to flex the hull and open the crack, (which may have initially been opened by a hard blow, but it didn't look like a blow had been repaired there.) I'd probably still want to be sure the compression force is not still able to cause any movement of the keel/hull joint area. As I look at your photos again, it seems there is a lot of compression load being taken up by the hull/keel joint, not the hull as a whole there, partly because the keel is pretty narrow and the compression post goes so deep into the keel to the top of the ballast. If that whole hole was filled and the post base was above the hull/keel joint I think it would be a lot stronger.

[Don C L]

Originally Posted by NahanniV

Cutting away some bad laminate on the inside revealed more of the cracks.
Some of the laminate (roving) seemed to have been never properly laid, it was just laying over the "V" of the keel, hard, but not attached, as if it was unable to conform to the sharp bend or the keel.

Also, I noticed some red filler or possibly paint in the crack.

This photo especially looks to me like it is showing the hull cracking from internal compression force. But I could be wrong! I have been once or twice.

[NahanniV]

Originally Posted by Don C L

All sounds good but I was thinking about your original post where I believe you said that when you applied the compression force, the crack began to leak.

That is true, no rig tension, no leak.

Originally Posted by Don C L

... I am a little skeptical that even a well-made patch will sustain the forces on it, but I certainly could be wrong. I know it is a small crack. I understand the mast base is 3 feet from the crack, but it sounded like the force was great enough to flex the hull and open the crack, (which may have initially been opened by a hard blow, but it didn't look like a blow had been repaired there.)

There was certainly some kind of filler pushed into the crack from the outside, but no sign of new laminate. The inside had never been touched since the boat was built, I had to cut the floor pan to access it.
It was certainly not a good repair job, I hope I can make one that will be stronger and more flexible than the filler that was there before.
Perhaps it was an impact to another area,as depicted in the attached picture, that originally opened the crack ?

Originally Posted by Don C L

... I'd probably still want to be sure the compression force is not still able to cause any movement of the keel/hull joint area. As I look at your photos again, it seems there is a lot of compression load being taken up by the hull/keel joint, not the hull as a whole there, partly because the keel is pretty narrow and the compression post goes so deep into the keel to the top of the ballast. If that whole hole was filled and the post base was above the hull/keel joint I think it would be a lot stronger.

The ballast is internal, not bolted on; It's lead and seems quite solid. The rusted metal step you see in the picture sits on the floor pan which is bonded to the top of the encapsulated ballast. I could not bring the step up much higher without changing the fuel tank.

[jimbunyard]

Well I'm still of the opinion that the inside and outside skin repair would be strong enough, but if you were worried, it wouldn't be difficult to make a short stringer, as shown in red in the attached drawing, glue it in with milled fibers and resin after you cover the crack with roving (or biaxial, it really doesn't make much difference), and then tab the well-faired-in stringer in all around, to both half-bulkheads and hull. Seems like overkill to me, but not much more effort and it certainly wouldn't hurt anything...

A piece of 3/4" coosa board, glassed on both sides before installation would do the trick, but since you're already buying some 1" G10, using a piece of that would make it kryptonite proof.

[NahanniV]

Thanks for all the input !

One question I have is if I should tension the chainplates and possibly put an extra jack stand under the bow of the boat during the repair ?

Cheers,
JM.

[Don C L]

Are you saying you want to open the crack before repairing it?

[hamburking]

Your pictures and description of the problem, and your determination to solve this leak are all very impressive. Thanks for documenting it so well, and sharing with the rest of us.

[coastalexplorer]

I see lots of professional advise here plus a plethora of alternative ideas, BUT
I Just wonder why? every time a repair is contemplated there seems to be a quest to make it so many times more special than the rest of the boat. It seems to me that there is a mind set that it has to be an absolute miracle or its just no good. IF stainless steel is in contact with regular ferrous metal that can rust: The stainless steel will also rust. If air is excluded from it so that the chrome cannot oxidize it will corrode? So to use it in every case is not a miraculous fix when mild steel could be either adequate or other alloy steels even stronger and more suitable.

Why does every fiber glass laminate repair automatically have to be epoxy resin? Polyester resins are much easier to work with; they can more effectively 'wet out' a wider variety of glass mats. especially chop strand mat that can most effectively form to any shape. and surely If the preparation of the area to be repaired is done correctly, the repair should be equal in strength to the rest of the hull?

Now of course that would be predicated on the method of the layup. Yes resin first and glass second to purge the air is absolutely correct, metal finned rollers are much more effective for this when using polyester resins than they are with Epoxy resins. So excluding air from the layup which affects its strength is easier for the handy man to achieve when using the same material that the boat is made from?

[chris95040]

Originally Posted by coastalexplorer

Why does every fiber glass laminate repair automatically have to be epoxy resin? Polyester resins are much easier to work with; they can more effectively 'wet out' a wider variety of glass mats. especially chop strand mat that can most effectively form to any shape. and surely If the preparation of the area to be repaired is done correctly, the repair should be equal in strength to the rest of the hull?

The bond strength of a repair is no where near the strength you get when the polymer is crosslinked throughout the structure (which is the case with new builds.)

You are right that the actual repair material, if made in polyester, will be similar in strength to the rest of the boat.

Its that the attachment of this repair material to the rest of the boat will never, ever, ever be as strong as if it were chemically crosslinked to it. We work around this by having huge bevels to maximize the contact area the repair has with the surrounding hull.

Another thing you can try to maximize is the bond strength of the repair to the hull. That's why people use epoxy, because it's superior to polyester in this regard.

Adequate bevel or not, that repair interface will always be there, and especially in this case where the repair area is loaded by the rig, I'd feel comfortable maximizing my bond strength so that the repair doesn't slowly tear / work itself out.

But in the end, I bet you are right. Polyester would probably be more than adequate. I'm just armchairing / explaining the rationale for using epoxy (which I would definitely use in this case.)

[NahanniV]

Originally Posted by Don C L

Are you saying you want to open the crack before repairing it?

Just wondering. With the rig off the weight of the boat is reversing the forces.

So, are you saying just do the repair as it sits ?

Thanks,
JM.