CORSAIR Keel Bolt opinion...

whilec
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CORSAIR Keel Bolt opinion...

Post by whilec »

Hello all,

I am a new poster to the WOA forum, although I am on my second westerly - the first being a lovely Longbow ketch called Spring Song.

My new boat was surveyed in September and no problems were detected with the keel bolts, on the Corsair of course the majority of bolts are hidden by the cockpit table not being easily removed. Fast forward to now and a little salt water has penetrated the trailing edge keel bolt (I.e. The one most aft) as shown here...
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The reminder of the bolts (or those with significant rust colouring) are shown here;
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The outside of the keel looks like this;
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I suppose what I'm looking for is a consensus. If I can avoid the expensive cost of re-bedding so soon after purchase, that would be good. However safety if of paramount concern - no one wants to lose a keel out in the blue, of even grey-green for that matter!

All Advice great fully received...

Chris
mikebuggy
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Re: CORSAIR Keel Bolt opinion...

Post by mikebuggy »

Hi. Are you certain that you have sea water actually entering at that particular stud? If still afloat, It may be possible to make a little cofferdam around it (using any form of handy gunge), dry the area around the stud, and see if it fills back up again inside the little cofferdam.
It is not unusual for these boats to have a pretty naff looking seam at the end of the season, particularly at the ends. Common practice is to take off any crud around the affected areas, and take the inner seam material back to sound material, preferably leaving you with a good straight 'groove' in the affected areas . Take any adjacent rusty iron back to a good shiny sound surface and then prime well with many coats of primacon. Finally apply a very good sikaflex sealant to the groove, ensuring its worked well in. You may need to use masking tape either side. This sort of regular/seasonal seam filling job is pretty common stuff for most bolt-on fins of this vintage.
It is worth looking at the boat when suspended in slings. No boat is entirely rigid when lifted, and the outer ends do flex a very small amount so expect a small bit of movement there. What you don't want is a huge gaping 'smile' though.
Flaky rust crud at the extremities is not unusual, but it would not be good to have major rust streaks coming from the central areas.
Vegable
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Re: CORSAIR Keel Bolt opinion...

Post by Vegable »

If I can add to Mike's comments above,
The width of the keel at the aft end is quite thin and you'll find that if you work out where the furthest aft keelbolt is on the outside of the boat you'll find it is quite a distance from the aft edge.
If you do go ferretting around the aft end you'll also find A LOT of filler at this aft end. If you want to investigate further, I did this about 6 years ago on a Renown and the following is cut and pasted from bits I've written before on this topic from various other answers I've submitted..

I ground back the joint using a "flapdisc" in an angle grinder. A flapdisc is much more gentle than a grinding disc. The hull to keel joint looks like a sandwich when cleaned and any rust coming through the joint is very obvious by its colour.Use a notch cut in a plastic fibreglass spreader (the blue ones you get in fibreglass kits) to give you a nice bead to finish off with. Fairy liquid washing-up liquid makes a good "blocking" barrier when using Sekaflex. I bought all the "stuff" on e-bay which was much cheaper.
The following is copied from a topic called " Keel Sealant". If you put it in the search, you'll get the full topic.

I did this a couple of years ago on Annabella. I posted a request for info on the website and got 2 replys both of them saying the same thing. Below are from my notes etc. I do have pictures too if you want. I bought 5 or six tubes of sealant and only used 4 I think.

Every year the sealant in the keel/hull joint of my Ocean 33 always pulled
away from the surfaces and I was keen to keep the water out of the joint. I
noticed that Starlights have a band of sealant about 40 mm wide so I have
copied this.

In the winter 03/04 I sealed the keel / hull joint with a 42 mm wide band of
Sikaflex 291 to give it good adhesion to the hull and the keel. It is still
performing very well with the Sikaflex band intact and no rust at its edges.
The surface has stretch marks in the antifouling but this is to be expected
as the keel will move and stretch the band. After the first season there
was some stickiness which may have resulted from not fully curing the
Sikaflex before I coated it with Primocon and Micron Extra antifouling.

The procedure I adopted was as follows. First I prepared a polythene tent
that could be warmed with a fan heater. I left the existing sealant in the
joint to give a level surface across which I planned to apply a Sikaflex
bandage. I scraped, degreased, sanded, degreased again and then primed the
GRP and cast iron surfaces with the proper Sika primer and kept them above
10 C inside the heated polythene tent. I also applied 2 strips of bond
breaker tape (for teak deck joints) over the joint area to give a stretching
zone of 12 mm; this is ample for even quite large movements and reduces the
load on the adhesion zones. The band of Sikaflex is 42 mm wide - 15 mm
bonded to the keel + 12 mm over the bond breaker + 15 mm bonded to the GRP
of the hull. I applied it with a plastic spreader shaped by myself to give
the profile I wanted to achieve on the Sikaflex band - 2 mm thickness at the
edges (angled down at 45 degrees to the surfaces) and about 5 mm in the
centre. I had a top and bottom band of masking tape set back 2 mm top and
bottom to act as visual guides while profiling the sealant. It is hard to
get a neat straight band but when the Sikaflex has partially set you can
easily go back over it to fill in the hollows and other imperfections. It
was a rush as you are supposed to apply the Sikaflex within 2 hours of the
primer. In this time I had to apply the bond breaker tapes, the top and
bottom masking tapes and apply the Sikaflex to the 3 m long joint (both
sides of keel). It took about 2 tubes of sealant.

A 2 part polysulphide sealant such as Thioflex 600 (made by Fosroc) would be
an even better sealant than Sikaflex 291 for continuous immersion but
unfortunately it has to be bought in larger quantities and the mixing adds a
further difficulty to the process. I understand that the later Westerlys
had their keels bedded in Thioflex 600 and Starlights used a similar
product.

All a bit complicated but considering how long it has lasted without any
work each winter I think that it was time and money well spent and it is
reassuring that water cannot get at the keel bolts.

( The above was a pasted answer to me)

My Notes.

Based on the advice given to the other respondant by Tony Stanton Davis (wrote book on osmosys & treatment in the 1980s)

6mm Teak Deck Joint Tape goes underneath teak decks. (Bond breaker/Separation Tape) Sikaflex Breaker Tape 6mm x 50m Roll

Sikaflex suggest 292 is better than 291as it's stronger. 291 is a general sealant whereas 292 is for chain plates and for bedding the keel onto the hull. items that'll take a lot of stress. 291 costs around £8 for 310mls, 292 costs around £22 for 310mls.

See the Sikaflex Marine Handbook (.pdf) for details. First pages and page15

Grind back to clean fibreglass. Be careful of the ends as they are just filled with filler to blend the hull in to the end of the keel casting. The ends are flexible because of the taper so the keel bolts are a good way back. The ends will vanish if you are too agressive with the angle grinder!

Tape over the crack with the 6mm tape. (I used 2 strips side by side with a slight overlap)
Then form a Sekoflex bead all the way round approx 30mm x 8mm took a few tubes. Then paint over with primer etc.

Use Sika 205 cleaner once cleaned out and then use Sika 206 Primer before using the 292. (Got slightly out of date tins cheap from e-bay. It's now 2016 and I'm still using them!)

As a general note you can also use Fairy Liquid to block the Sikaflex from screw threads etc etc. Also use it to tool off where it's squeezed out of joints.

Somewhere I read that this has to be done at temperatures above 10C

I'm very grateful to 2 members who answered my initial query back in October 2009. Geoff Mills, who took the trouble to phone me and discuss it in detail and John Clarke who answered with the first description I pasted above which was a very similar recommendation.

Come back to me if you want more info. Somewhere I took photos of what I did, but they're at home and I'm in Oz till mid April (2016). I should add that I did this in a warm October day in a boatyard and it took (say) a couple of hours only to do. I'll also say again that it's as obvious as a wart on the end of your nose where seawater is penetrating once you get to the joint.

Hope this helps. One day I'll put it on the Wiki.......one day!
Mike
"There is nothing worse than running ashore, unless you are uncertain as to which continent that shore belongs"
tallchris66
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Re: CORSAIR Keel Bolt opinion...

Post by tallchris66 »

Hi Mikebuggy, I'm pretty sure it's seawater. Did a test by dipping little finger in, was VERY salty - although on reflection it could have been the iron in the rust.
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Re: CORSAIR Keel Bolt opinion...

Post by tallchris66 »

Hi Vegable, many thanks for your reply, lots of very good information. I'm going to have a good read through, get the materials together and hope for descent weather over the Easter break!
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Re: CORSAIR Keel Bolt opinion...

Post by jim1945 »

Vegable, what is the idea behind using the bond breaker tape? When I look at the Sika site this tape seems to be used instead of a foam backer rod in certain situations where there are wide joints. In your case was there a wide joint that required the use of the tape?
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Re: CORSAIR Keel Bolt opinion...

Post by Vegable »

I haven't a clue. Two separate people told me the same thing, one of them backed by a respected Yacht Surveyor so I followed their guidance to the letter. The gap at the keel joint was about 10mm wide. At the surface after grinding out it was close to 30mm wide. If it's any help the tape is used for putting underneath the joints of teak decks before caulking.
Mike
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Re: CORSAIR Keel Bolt opinion...

Post by jim1945 »

Vegable wrote:I haven't a clue. Two separate people told me the same thing, one of them backed by a respected Yacht Surveyor so I followed their guidance to the letter. The gap at the keel joint was about 10mm wide. At the surface after grinding out it was close to 30mm wide. If it's any help the tape is used for putting underneath the joints of teak decks before caulking.
Mike
Those gaps( 10 mm and 30 mm) are huge. Did you grind those out that much and if so why?
mikebuggy
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Re: CORSAIR Keel Bolt opinion...

Post by mikebuggy »

It sounds like a very thorough and comprehensive scheme, but also seems quite elaborate and complicated. Most boatyard shipwrights just rake out any unsound material, clean back and prime all the surfaces and apply sikaflex straight to the seam. If done properly it lasts well.
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Re: CORSAIR Keel Bolt opinion...

Post by Vegable »

Jim,
Have you read my copying above?
The original instructions to me (the indented bit) clearly states why the tape and how much bonding to the keel, the breaker tape and the hull he deemed necessary. He had a 42 mm gap. What's so horrific about my 3O mm gap?
If you're not going to read what's written, then nobody will be able to advise you.
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Re: CORSAIR Keel Bolt opinion...

Post by jim1945 »

Vegable, when I look at the Sika site I see they are using backer rod or tape for wide and deep joints. So I assumed you were grinding a deep joint as well as wide joint, because of using the backer tape. And in your answer to my first question you said there was a 10 mm gap in the stub/keel joint. That's one centimeter and is a wider gap than normally seen. Normally you see just a "knife edge" type separation at the keel joint. My second question probably wasn't stated properly. I wanted to know your thoughts on why or how the 10 mm gap developed. I was just trying to understand what you had to fix and the fix itself.
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Re: CORSAIR Keel Bolt opinion...

Post by Vegable »

The 10mm gap was the width of the trench cut in the filler to get to the joint, NOT that I had a gap of 10 mm between the hull of the boat and the keel. The trench was 8mm deep because Westerly's faired the hull to the keel with filler and in my boat's case it was approximately 8mm thick. I didn't touch the actual joint at all. And I certainly didn't do any grinding. If you read above again I used tape only 6 mm wide.
"6mm Teak Deck Joint Tape goes underneath teak decks. (Bond breaker/Separation Tape) Sikaflex Breaker Tape 6mm x 50m Roll". And before you ask, no I didn't use all 50 metres.
The reason I redid my boat was for the same reason as the o/p, The boat had an unsightly crack along the keel joint. Nothing more, nothing less.
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Re: CORSAIR Keel Bolt opinion...

Post by tallchris66 »

Well, here's the latest.
I decided after examining a few nuts to replace all the nuts with new A4 Stainless ones, Half, Full and washers. 6 came out allowing me to pull up the reinforcing plates, 4 didn't allow this so I just bedded the washers down and fitted new M24 items.
Nut 11 however is a problem.
I had to cut about 15mm off the top of the bolt to allow the deepest socket I could find to fit. I apply my bfi and voila! The nut turned! Sadly, so did the bolt.
Air bubbles then proceeded to exit from under the reinforcing plate, which I think means there is access to the outside world from the bolt cavity!!
I set about the bolt with an angle grinder, being as careful as I could, but still the damn but lives - corroded in to the bolt. I know this because a previous person used an A2 nut instead of A4!

Advice on removing very large nuts welcomed!!
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Re: CORSAIR Keel Bolt opinion...

Post by Vegable »

Hi Chris,
Can you get to the stud/bolt with an open jaw spanner or a ring spanner. If so you have a number of options. Lock the stud with stilsons whilst trying to turn the nut, saw a slot in the top of the stud and use a screwdriver F.E. ( where E stands for enormous!) to lock the stud. Apply heat to the nut and plumbers pipe freeze spray to the stub to break the corrosion. Be VERY careful when using heat. Fibreglass doesn't like a lot of heat at all.
If none of those options are available, use a penetrating fluid. Make a coffer dam around the stud and nut with putty/plumbers mate etc and soak for a good while with penetrating oil. A good while means days not minutes! I've never tried olive oil and vinegar mix but I've heard good reports about it. You could also try brick cleaner from B&Q which is Hydrachloric Acid in a dilute form but still can sting your hands. Another very good penetrating fluid is a home made 50:50 mix of Automatic Transmission Fluid (ATF) and Accetone which I got from the Hydrovane site. Be very careful with this as accetone disolves fibreglass. You'll only need a small amount so your wife's nail varnish remover will do nicely. Wait till she goes out though! Might be worth drilling 6mm holes into the nut and stub to get right at the treads.
Failing all that, get the boatyard to do it and go off to the pub so you can't see what they are doing to your boat!
Hope this is of some help. Good luck
Mike
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Re: CORSAIR Keel Bolt opinion...

Post by tallchris66 »

Hi Mike,

I went for the grinder method!Image

Eventually after much wailing and gnashing of teeth, the nut capitulated!

Now have 7 bolts which have had nuts removed, strengthening plates out, cleaned and re-needed and torqued to 150 lb/ft. The remaining 4 I could not get out the strengthening plates so had to make do with bedding the nuts and washers.

HOPEFULLY, once I've followed the advice of putting a band of mastic round the keel joint, the bilge will be dry on re-launch...!
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