Damaged Gelcoat below waterline on Westerly Centaur

[Swanrad2]

Thanks guys and sorry I disappeared for a week between posts. A bad week at work with a bad back! Update....I ground down all of the cracks in the gel coat, nowhere did they penetrate into the fibreglass. I used one of the narrow Snub nosed belt sanders/electric files, what a tool that is....compared to an angle grinder slower but with so much more control. Absolutely the right tool for the job.

That leaves me with a filling and fairing job. It was suggested I use a flexible epoxy filler but never used one before. They seem to go from Epoxy plastic padding right up to Hempel‘s system . With the fact this will be painted, undercoated and then antifiped what would the experienced offer as suggestions? I would have reached for West systems but apparently its like trying to sand steal.

 

[pvb]

Thanks guys and sorry I disappeared for a week between posts. A bad week at work with a bad back! Update....I ground down all of the cracks in the gel coat, nowhere did they penetrate into the fibreglass. I used one of the narrow Snub nosed belt sanders/electric files, what a tool that is....compared to an angle grinder slower but with so much more control. Absolutely the right tool for the job.

That leaves me with a filling and fairing job. It was suggested I use a flexible epoxy filler but never used one before. They seem to go from Epoxy plastic padding right up to Hempel‘s system . With the fact this will be painted, undercoated and then antifiped what would the experienced offer as suggestions? I would have reached for West systems but apparently its like trying to sand steal.

You still haven't said whether your boat has had the fairly essential strengthening added. Keel bolts don't simply work loose on their own, there has to be an underlying cause. There's no point patching the cracks in your gelcoat unless you work out why they happened in the first place. Initially you claimed you'd "neglected" the keel bolts and they became loose. This doesn't happen in real life, something else has affected them.

 

[anoccasionalyachtsman]

Thanks guys and sorry I disappeared for a week between posts. A bad week at work with a bad back! Update....I ground down all of the cracks in the gel coat, nowhere did they penetrate into the fibreglass. I used one of the narrow Snub nosed belt sanders/electric files, what a tool that is....compared to an angle grinder slower but with so much more control. Absolutely the right tool for the job.

That leaves me with a filling and fairing job. It was suggested I use a flexible epoxy filler but never used one before. They seem to go from Epoxy plastic padding right up to Hempel‘s system . With the fact this will be painted, undercoated and then antifiped what would the experienced offer as suggestions? I would have reached for West systems but apparently its like trying to sand steal.

For a sandable epoxy filler mic microballoons with your epoxy resin.

Like others, I'm not convinced that your keel bolts have loosened in the way that you think.

 

[Swanrad2]

You still haven't said whether your boat has had the fairly essential strengthening added. Keel bolts don't simply work loose on their own, there has to be an underlying cause. There's no point patching the cracks in your gelcoat unless you work out why they happened in the first place. Initially you claimed you'd "neglected" the keel bolts and they became loose. This doesn't happen in real life, something else has affected them.

Hi,

There are three mini bulkheads on each side between the two full bulkheads on both sides - this is the strengthening that I think you refer to. The boat was built in 1979 and I think this was standard practice by this time?. All are tabbed in and the tabbing is in good condition. I have looked as closely as I can and can see no evidence of any kind of damage to the fibreglass inside or out. I have owned the boat for 15 years and never tightened the keel bolts before last year. Six of these years have been on a drying mud berth (although the mud is over harder sand and not particularly deep). There is no water ingress through the keel bolts. My intention is to drop and re-bed the keels next winter, originally I was going to do so this winter but the weather followed by Covid put paid to that plan. This is the reason I scraped Back the anti fouling to inspect and make sure I didn’t see anything catastrophic.

After tightening the keel bolts at the beginning of last season there was no movement in the keel, movement which was evident when the boat was put ashore at the end of the previous season.

I can’t attach photos as I only have an I pad at home and the system won’t let me, but in the sample areas I have ground the cracks back to fibreglass I see no discolouration (the substrate is pinkish and clean looking with no blackening and solid as a rock when hit with a hammer). I am aware this is a common weakness with Centaurs, and didn‘t look for reasons not to do the work - I just found no evidence of damage to the fibreglass.

We did take a heck of a clout on the starboard side just above the water line when coming into a pontoon against the tide, the stern line bit a little early swinging the boat into the pontoon....it could have been that which caused the crazing and the two issues are unrelated? Whist a little loose, the keel bolts allowed some flexing, it wasn’t wobbling around freely.

 

[pvb]

Keel bolts don't normally come loose on their own.

 

[viago]

HI,

We neglected our Keel bolts. They became loose towards the end of the season and when bringing ashore the keel flexed cracking the gelcoat over a couple of square metres beneath the antifoul. So, I need to grind it back and have been watching videos and reading blogs for a few days but thought I would check my conclusions with the great hive mind.

1. I am intending to grind the gel-coat back to fibreglass (test grinds have revealed the cracks do not extend into the underlying laminate which is sound and not discoloured) one small section at a time, say 6 inches x 6 inches to catch all of the cracks. For this I think a flap wheel on an angle grinder seems to make most sense, done slowly and carefully so as not to grind too deeply into the glass.
2. Wash down with denatured alcohol.
3. Assuming no damage to any of the laminate I may lay on a couple of layers of bi-axial glass with epoxy resin to secure the substrate.
4. Sand back slightly and use gel-coat to 'bridge' between the high points to either side of the 'trench' I have ground out.
5. Repeat.

I have no experience of Epoxy based fillers, hence I'm reverting to gel coat. I own an angle grinder (but not a long nose sander that some of the videos seem to favour) so that seems to make sense.

Am I missing anything?

Cheers

i think it highly unlikely you have got away with just damage to the gelcoat. i cant see the glass not being damaged as well, at least around the bolt holes.

still, you may be lucky.

if the rest is sound i see nothing wrong with your repair recipe it's exactly what the pro's do.
grind back with a flappy disc and glass and epoxy up the substrate then a few rollings of gelcoat and one with wax. easy job, no need to colour match or get a perfect finish.

i know we likes our centaurs because they sit on the ground nicely but forty years of four ton bouncing on the ground four times a day takes it's toll on the hull. it's testament to the original lay up that so many still exist. my hull looks like bubble wrap below the water line. floats ok though so it can stay like it. it'll outlast me.

 

[Keith 66]

In my boatbuilding career i have repaired at least half a dozen Centaurs & Konsorts whose keels had either fallen off or were about to. Cracks in the gelcoat such as you describe are a sure 100% sign that structural damage to the laminate has occured, you might not see it but its there. Often cracking to gelcoat or lifting of the tabbing on the interior is hidden or dismissed by surveyors as "cosmetic" it isnt.
Two Centaurs i worked on within the last 6 years both had survey reports stating they had been strengthened. Neither boat had been strengthened at all, the standard lay up is flimsy & weak. You need to get it done properly.

 

[Jokani]

Question When beefing up or replacing the transverse stringers, I would have assumed polyester resin, or flexible polyester resin would be the way to go, as it would adhere to the the polyester lay up/hul better than epoxy would, am I wrong in that assumption?

 

[londonpiper]

You'll most likely find the answer on the Westerly Owners Association site where there are many, many Centaur owners. If you're not already a member , I strongly recommend that you become one, the tiny yearly sub is worth its weight in discounts alone!

 

[LittleSister]

Question When beefing up or replacing the transverse stringers, I would have assumed polyester resin, or flexible polyester resin would be the way to go, as it would adhere to the the polyester lay up/hul better than epoxy would, am I wrong in that assumption?

I believe that assumption is wrong.

Its adhesive properties are one of the big advantages of epoxy resin. My understanding is that it is difficult to get new polyester resin to adhere well to old polyester laminate.

 

[Graham376]

I believe that assumption is wrong.

Its adhesive properties are one of the big advantages of epoxy resin. My understanding is that it is difficult to get new polyester resin to adhere well to old polyester laminate.

When I beefed up the keels on our Berwick, the surveyor specified polyester and he'd previously been yard manager for a well known repairer so I trusted his judgment.

 

[sailaboutvic]

I'm not going to suggest any way to repair it , so many good advise given I think by now your getting mix messages, why not get a bît of advise before going any further from a local boat yard who know what he looking at rather then all the guessing with such an important issue.

 

[Refueler]

+1

Centaurs lose keels when the bottom falls out of the stub, usually the exact shape of the keel top. From what's been said, the keel needs to come off and the internal area needs cleaning off and reinforcing with small bulkheads across the stubs, the new layup needs to be carried well outside the stubs. The outside needs grinding back over the complete area to the depth of the cracks and may need some extra layup as well. I had to reinforce the stubs on a Berwick which is the same design, fortunately before the keels fell off.

When I used to survey years ago ... it was nicknamed the Cats cradle .... because it resembled a couple of H 's laid alongside each other ...
The other bit was to get rid of any penny washers and use something a bit larger !!

 

[Refueler]

When I beefed up the keels on our Berwick, the surveyor specified polyester and he'd previously been yard manager for a well known repairer so I trusted his judgment.

If not prepared well - old polyester is a right s*d to adhere to ....

The old trick was to use something like Oven Cleaner to really get the crud away and it spotlessly clean ... water rinse that of and then acetone wipe to get the surface to 'grab' the new.

Epoxy was an alternative because it had ability to grab after cleaning. It also had less tendency to moisture pickup as standard Polyester is osmosis prone.

 

[C08]

In my boatbuilding career i have repaired at least half a dozen Centaurs & Konsorts whose keels had either fallen off or were about to. Cracks in the gelcoat such as you describe are a sure 100% sign that structural damage to the laminate has occured, you might not see it but its there. Often cracking to gelcoat or lifting of the tabbing on the interior is hidden or dismissed by surveyors as "cosmetic" it isnt.
Two Centaurs i worked on within the last 6 years both had survey reports stating they had been strengthened. Neither boat had been strengthened at all, the standard lay up is flimsy & weak. You need to get it done properly.

Yes when I moored in N Wales there were 2 Westerly Pageants in my club that developed cracks between the keels and were only saved from sinking by being on tidal moorings. Also one Centaur lost a keel and a Westerly 33 owner came over the mud to ask for advice "as his keel was coming off". He managed to limp back to Pwllheli before he sank.

 

[pvb]

Yes when I moored in N Wales there were 2 Westerly Pageants in my club that developed cracks between the keels and were only saved from sinking by being on tidal moorings. Also one Centaur lost a keel and a Westerly 33 owner came over the mud to ask for advice "as his keel was coming off". He managed to limp back to Pwllheli before he sank.

Makes you wonder why old Westerly yachts seem so popular! Maybe buyers don't research known problems.

 

[Refueler]

Makes you wonder why old Westerly yachts seem so popular! Maybe buyers don't research known problems.

Given the sheer number of them ... vs the number with keels dropping off ??

I would suspect that today - the average boat punter wouldn't know what to look for to know if work had been done or not. Its not like the 80's ... early 90's ... when they were really popular and every yard literally was beefing up keels on one or two ... I can remember going round yards and seeing so many with keels dropped for work ...

 

[Mister E]

After you tightened the Keel Bolts did you reset the resin around them?
If not then the flexing involved in a drying mooring could possibly have caused them to work loose again.

 

[pvb]

After you tightened the Keel Bolts did you reset the resin around them?
If not then the flexing involved in a drying mooring could possibly have caused them to work loose again.

They'd surely only work loose if the laminate is breaking down? Nuts don't unwind themselves.

 

[Keith 66]

I have seen 2 Centaurs that had been fibreglassed straight over old oily filthy danboline bilge paint, nothing is going to stick to that! If you grind back to clean glass Poyester will stick perfectly, or Vinylester which approaches epoxy in performance but with ease of use of polyester.
One thing people who advocate epoxy often dont realise is that the glass reinforcement should have an epoxy compatible size (adhesion promoter), Glass intended for poly or vinylester has a different size.