Keel and G/flex and should I worry?

[High Current]

I'm looking for some insight into what I should realistically expect from G/flex epoxy and keel movement on an old Hunter 25.

My 1982 Hunter 25 came with a small keel smile. This spring, I ground it out, torqued the keel bolts (132 ft-lb), and slathered some G/flex epoxy in the gap. At haul-out last week I inspected it hanging in the travelift slings and it was still flawless. Survived a lot of sailing, a choppy harbor, and the 10 mile drive to the launch so I was feeling pretty good. But then, after they drove it across the yard and put her up on jack stands, a pair of small cracks formed at the front. I didn't see it happen, but I have 300 lb of batteries in the stern (electric drive) so I'm guessing she probably leaned back a little while resting on the keel, before they got the stands properly tightened.

Is this "normal" or does it suggest excess movement in the keel stub / bolts? Supposedly G/flex can elongate 33%, so I'm worried it may have taken considerable movement to break it. I believe the keel stub itself is solid fiberglass; my understanding is a lot of "smiles" come from wooden core. Anyone else have a smiling hunter to compare? Anyone see G/flex cracking with known-good stub + bolts? I'm trying to gauge how much risk I'm taking if I keep sailing it. I'm guessing (a) I'm overthinking it, and (b) it would be more money than the boat is worth to drop the keel for a full inspection, but looking for a sanity check.

Pictures follow.

Thanks!

Small cracks after haul-out:

Prior to my repair. She had fallen over on the hard which opened the gap; it was barely visible standing up There was what looked like a prior repair with silicone caulk and an outer layer of fiberglass that peeled off easily (you can see the second crack where this "fairing" buckled a bit). No rust stains, so if the keel bolts were corroding they did it stealthily.

After grinding, before cleanup/epoxy. The gap in front looks big, but it's only because I picked out some glass-like old resin that was loose:

Bilge side of the bolts looked fine this spring (for whatever that's worth).

 

[dmax]

The first thing I would do is try to determine if the keel is moving (excessively). This could be done by raising the bow slightly and measuring any change in the gap. I'm not sure how much movement would be too much but if it really shouldn't move much at all. If there's a lot of movement, you really should try to drop the keel, inspect the bolts and do a complete re-bed of the joint - otherwise, the crack will just come back. If the movement is acceptable, I would grind out the whole joint as much as possible (really deep if you can), clean it up and fill with thickened epoxy. Different people have different opinions on what to use for filling the (5200, thickened epoxy, G-Flex) but in this case I wouldn't use 5200 or G-Flex because you are trying to stiffen up the joint.

 

[heritage]

Your second picture shows two cracks. I can only assume that one(the lower crack) is between the keel stub and the lead keel. The upper one must be where the keel stub attaches to the bilge. Have you had any water coming into the bilge or see a crack in the forward part of bilge?

 

[High Current]

Maybe I should delete that 2nd photo. I only included it for context; it predates my repair. The upper crack was the keel to stub seam; the lower one was just the previous owner's crappy cover-up job peeling off.

Here's post-repair before launch in the spring. It still looked like this in the travelift last week (I didn't snap a picture). The cracks didn't form until they blocked it on the stands. Definitely no leaking, but that's to be expected since the seam was sealed, regardless of the condition of the bolts.

The cracks that I'm worried about now are tiny by comparison:

 

[High Current]

The first thing I would do is try to determine if the keel is moving (excessively). This could be done by raising the bow slightly and measuring any change in the gap. I'm not sure how much movement would be too much but if it really shouldn't move much at all. If there's a lot of movement, you really should try to drop the keel, inspect the bolts and do a complete re-bed of the joint - otherwise, the crack will just come back. If the movement is acceptable, I would grind out the whole joint as much as possible (really deep if you can), clean it up and fill with thickened epoxy. Different people have different opinions on what to use for filling the (5200, thickened epoxy, G-Flex) but in this case I wouldn't use 5200 or G-Flex because you are trying to stiffen up the joint.

Hmmm...not sure if this is what you're saying but...now that the G/flex is already fractured I no longer have to worry about it "hiding" any residual movement? So if I lift the boat and the crack doesn't widen I'm probably OK? Can I do that with the stands, or do I need to have someone come in with a lift?

 

[dlochner]

It is really hard to assess any damage with the bottom paint covering the repair. Remove the bottom paint. Then see how deep the crack goes.

 

[Leeward Rail]

135 ft lbs seems low. What is the bolt/stud size?

This is what MarsKeel (makers of lead keels) says:

"Regarding the bolt torque, here are the specs based on bolt size:
1/2" - 90 ft. lbs. ,
3/4" - 250 ft.lbs. ,
1" - 350 ft. lbs.
Please be careful in tightening as if the bolts are fatigued based on age
this should be taken into consideration."

I would obviously use what Hunter specs.

Do those backing washers seem inadequate? I would want some that are bigger. Square plates for example. Just my way of thinking... Someone who has done keel work would obviously have better advise.

 

[berner73]

A lot of variables here to consider, but when it comes to the integrity of keels it would seem prudent to err on the side of caution. The unfortunate reality is that you'll be left with some degree of uncertainty unless you drop the keel/inspect the bolts/rebed/glass over the joint. There are several threads on SBO documenting other owners experience with this process (eherlihy and Maine Sail have both contributed excellent threads on this topic - see links below).

It's encouraging that you didn't detect any signs of separation when she was in the slings at haul out - had the hull been pressure washed at the time you first inspected it? It's confusing that you saw such a large amount of movement after being blocked. One would think that the sheer forces on a keel associated with sailing far exceed the tensile forces with the keel at rest (meaning I would have expected any cracks to be visible immediately at haul out and not a function of blocking). I believe West System specs GFlex relative to tensile adhesion (pulling force). I don't know what impact the thickness of an application has on the elasticity of the cured bond. It may be worth a call to West Systems to understand their expectations around your repair. I've always found them to be very responsive and engaged (866-937-8797).

Here are a couple of past threads re: keel/hull joints

A wet bilge is more than a nuisance

Weeping keel joint (unfortunately the photo links are no longer active but you could reach out to eherlihy for more details)

 

[High Current]

135 ft lbs seems low. What is the bolt/stud size?

This is what MarsKeel (makers of lead keels) says:

"Regarding the bolt torque, here are the specs based on bolt size:
1/2" - 90 ft. lbs. ,
3/4" - 250 ft.lbs. ,
1" - 350 ft. lbs.
Please be careful in tightening as if the bolts are fatigued based on age
this should be taken into consideration."

I would obviously use what Hunter specs.

Do those backing washers seem inadequate? I would want some that are bigger. Square plates for example. Just my way of thinking... Someone who has done keel work would obviously have better advise.

Interesting and thank you for that. If it's indeed low that might explain a few things.

My bolts are 3/4". Somewhere on the Hunter forums I had come across a spreadsheet that gave specs for several newer hunters (not mine) plus generic specs for 3/8" to 1-1/4" bolts, which is what I used. It seems to agree with standard engineering tables such as this one: https://www.fastenal.com/content/feds/pdf/Torque of Stainless Steel, Non ferrous Torque.pdf

As for the washers...it's a small boat. Keel is only 1800lb and there are seven 3/4" bolts holding it on. Unless there's good reason to believe there was a design flaw I'd rather not mess with it.

 

[High Current]

It's encouraging that you didn't detect any signs of separation when she was in the slings at haul out - had the hull been pressure washed at the time you first inspected it? It's confusing that you saw such a large amount of movement after being blocked. One would think that the sheer forces on a keel associated with sailing far exceed the tensile forces with the keel at rest (meaning I would have expected any cracks to be visible immediately at haul out and not a function of blocking). I believe West System specs GFlex relative to tensile adhesion (pulling force). I don't know what impact the thickness of an application has on the elasticity of the cured bond. It may be worth a call to West Systems to understand their expectations around your repair. I've always found them to be very responsive and engaged (866-937-8797).

Thanks! Yes the inspection was after they power washed it, while I was waiting for them to bring a truck around. I too would have thought the dynamic forces from sailing would exceed anything it would see on blocks (or on the short trailer ride across the yard). Maybe they were a little rough lowering it onto the blocks? Maybe there's something about the torque moment of having all those batteries in the stern? Or maybe the crack WAS there at haul-out but closed up / invisible because the load was more evenly distributed?

G/flex tensile elongation is spec'd at 32.7%: https://www.westsystem.com/wp-content/uploads/G-flex-tds.pdf But I only pretend at mechanical engineering and just learned that number includes plastic deformation.

Tensile modulus is 144,000 psi and tensile strength is 3,440 psi, so elastic strain is only 2.39%...I think? That makes it seem like less of a "permanent" fix and therefore less alarming that a small crack could develop. It will also be interesting to grind back the paint and see if the crack is primarily internal to the epoxy or its bond to the lead. I'll definitely try giving them a call.

Here are a couple of past threads re: keel/hull joints

Thanks. I've read both of those, among others, and was actually hoping not to beat a dead horse with this thread. I primarily hoped to
1) Hear other peoples' experiences, to check my (slightly skeptical) impression that G/flex should be a "permanent" fix unless things are really bad, and
2) Get a better handle on how much, if any, smile is 'normal' for a Hunter of this vintage

 

[Leeward Rail]

My bolts are 3/4". Somewhere on the Hunter forums I had come across a spreadsheet that gave specs

The guys at Marskeel should be able to confirm. They may have made the keel.

@Crazy Dave Condon should also be able to advise. I believe he was a Hunter dealer.

Unless there's good reason to believe there was a design flaw I'd rather not mess with it.

Agreed. Though with most boats, builders make compromises based on expected life and sales price point The reason I mentioned it is that I have seen a couple people use rectangular stainless plates instead of the original washers, when rebedding and torqueing their keel, as an upgrade.

FWIW I know of 2 people that used gflex to fix smiles and they haven't come back with twice yearly haulout and large temp range from winter to summer.
The boats are ramp launched on yard trailers and not craned. Not sure what other variables exist.

I plan to do the same job to our C&C30.

 

[Tally Ho]

The photos of the crack, after you “cleaned it up “ would concern me. Filling the void with G/Flex is not going to hold.

Ideally, the keel and stub should be flat and evenly spaced, bonded with 5200 as the keel and stub are mated and the keel bolts tightened.

Greg

 

[jssailem]

Ideally, the keel and stub should be flat and evenly spaced, bonded with 5200 as the keel and stub are mated and the keel bolts tightened.

Good words.
If I understand the mechanical mechanism, proper repair requires

1. removal of the keel
2. Cleanup and repair of any damage to the surface and substrates of the keel and hull areas
3. Then mating the keel to the hull for a smooth snug fit (no or minimal gaps) using 3M 5200 so it squeezes into and seals any gaps
4. Tightening the keel bolts to proper tension
5. Applying filler to smooth the surfaces and bottom painting

A considerable work process.
G flex would be a temporary fix approach to the problem in order to get by til the maintenance could be scheduled.

 

[Crazy Dave Condon]

Yes I was a hunter dealer and serviced the Old style 25’s. The boat is 40 years old and given the age, bolts have loosened up allowing the keel to flex. I am not going to comment on G Flex but concur with
@Tally Ho and @jssailem on their approach to repairs as that is what I would do. As for the washers I would use the larger plates of stainless steel if they can fit.