Dropping the Keel

[matt2]

This looks like the sort of place where there are people that will know about dropping a keel.

I am looking advice on dropping a fin keel to inspect the keel bolts.

Background
I have a small crack in the keel which may go beyond the gel coat. There are no internal leaks from nuts, but I have decided it is time to check the keel bolts and fix the crack and also re-fare the bottom of the boat and keel at the same time.

I have seen a keel dropped and reattached before and the process looked fairly simple, provided you have a crane that can lift the boat. Searching the net for other methods used include creating a frame to support the boat in a fixed position and a separate frame to lower the keel into, but then maneuvering the keel back on might be more difficult.

To get an idea of the size of the project the boat is a 40 ft fiberglass mono hull with a fin keel attachment. The keel bolts are in line and there is what is called a deadwood stub (glassed) below this there is an external lead keel. The keel proportions are the same as the Farr 12.2 meter.

Questions
So my main question is once I have dropped the keel and checked everything is OK with the bolts and come to be reattaching the keel what adhesive should I use? I have read and heard different things, i.e. that there are special glues/sealants that are extremely powerful that are used to attach keels. One rebedding compound that is mentioned quite a lot in relation to keel bedding is 3M 5200. There are probably others...?

Another method also used by others is to epoxy mixed with micro-balloons or perhaps chopped glass fibers to produce a sort of paste that has a consistency somewhere between peanut butter and honey.

Some people also recommend adding "Pentamid" to the epoxy to make it more flexible, but not sure if I want any flexibility at all.

Apply this to the cleaned, dry roughened surfaces on both the boat and the top of the rudder. Then lay a smooth mound of the epoxy mix on top of the keel in the middle running fore and aft about an inch or more high. This mound will push out any air as the keel and boat come together.

I have been tossing up another additional protection against future cracks and leakage, but have not seen any it done anywhere else. I was thinking that I could use 5200 (or epoxy+Pentamid) in a small ring around the actual bolts and epoxy paste everywhere else. The idea is that if the epoxy cracks the 5200 being flexible will still provide a seal to prevent water access to the bolts and therefore any galvanic corrosion. I am not sure exactly how this would work in practice.

Then lower the boat onto the keel, do up the bolts. I think the the bolts then should be retorqued (using a torque wrench) to the same average toque as before they were removed. The retorquing the bolts needs to happen while the boat is still on the hard and with boat sitting back on the keel and other supports. The question here is that when the boat goes back in the water the keel will be pulling down rather than pushing up, so perhaps the boat needs to be support and some weight taken off the keel when retorquing the keel nuts. In any case the important thing in this phase is to not have the boat wobble or move before the rebedding adhesive is set. If the boat does move you could end up with a gap. But easier said than done, any ideas?

After the keel is set clean the excess epoxy paste away and wait a day or so before fairing in some new glass around the keel base. At this stage I was thinking of building up the base of the keel so the join was a bit more rounded and better supported so the keel is less likely to crack again. To do this I would sandblast to remove the gel coat around the keel and build up layers of epoxy and cloth cut to cover an increased area with each layer.
different thickness. How can I get heavy cloth to stick when applying it to the bottom of the boat? I am guessing apply a coat of epoxy wait till it starts to go off and lay the cloth on top, then paint on some new epoxy before the initial coat completely sets.

Does this sound reasonable?

Many production boats are shipped with keel unattached and it is then reattached on arrival. So I am wondering what technique and adhesives are used in these cases?

Anyone had any experience with this?

[PAR]

You don't want to use epoxy to bond your keel to the hull. Even with modifiers added (for flexibility) it's just the wrong material. 3M 5200 is the goo of choice in this role.

You don't need a crane, a travel lift will do. Have your work area arranged before hand, which requires a cradle for the boat, blocking for the keel and room to work around it.

As a rule it's easier to move the lighter of the two (the keel), then lift the boat. By this I mean it's often easier to use the boat's own weight to assist in removing the keel. So, dropping the keel, rather then raising the boat is often a better way to go. The boat will have to be on stands or in a cradle high enough to permit the keel to drop down the length of the bolts. A fork lift and some wooden bracing can handle the keel and drag it out from under the boat so you can have room to work on it.

You can employ a crane or travel lift, if you want, but I'd strongly recommend you have some profession assistance on hand. Moving objects this size and weight requires expertise, equipment and a fair understanding of how things work.

Place a bead of 3M 5200 around each bolt, bolt hole and the perimeter of the appendage. This is all you need. Tighten the nuts down to the recommend torque of the manufacture, nothing less. Once tightened to proper torque, you don't have to worry about which way gravity is pulling or water pressure is pushing.

If you have some laminate issues at the fin root, you should determine what caused it. It's very likely the cracks you're seeing are a result of a keel that has been working back and forth (if an ever slight amount) for a number of years. You can reinforce the laminate, but it has to be done right or you're inviting trouble. From the nature of your questions and general understanding of the tasks involved, you should have a surveyor come out and look over the keel joint. Once the extent of the damage is understood, you can form a plan of attack for an effective repair schedule.

[matt2]

You don't want to use epoxy to bond your keel to the hull. Even with modifiers added (for flexibility) it's just the wrong material. 3M 5200 is the goo of choice in this role.
Ok great. Would you think that this is a one off job, or the type of thing I will have to do over and over?
You don't need a crane, a travel lift will do. Have your work area arranged before hand, which requires a cradle for the boat, blocking for the keel and room to work around it.
As a rule it's easier to move the lighter of the two (the keel), then lift the boat. By this I mean it's often easier to use the boat's own weight to assist in removing the keel. So, dropping the keel, rather then raising the boat is often a better way to go. The boat will have to be on stands or in a cradle high enough to permit the keel to drop down the length of the bolts. A fork lift and some wooden bracing can handle the keel and drag it out from under the boat so you can have room to work on it.
Yes that may turn out an easier way. I was going to weld up a frame and stick it on wheels. I had it in mind to use are car jack or two to lift the keel back into position. The getting the keel back on in this case might turn out to be quite difficult to do in a controlled way.
You can employ a crane or travel lift, if you want, but I'd strongly recommend you have some profession assistance on hand. Moving objects this size and weight requires expertise, equipment and a fair understanding of how things work.
Yes good advice. I feel confident that I can get the support I need. However, they don't have a keel frame, so I guess I will just have to create one. The travel lift crane solution looked very simple and was very quick when I saw this done on a similar yacht about 10 years ago. It was one guy (who had done this before) and the boat was carefully craned onto the keel and nuts tightened in half an hour. He used a brown paste-like mix of stuff placed on the entire keel surface & also on the hull in conjunction with a mound of the mix down the fore and aft center line of the keel.

My preference is not to use a crane or travel lift but only struts and lower the keel on to my platform. The crane is quick but expensive the frame method is cheaper and y ou have more control on when you do it.
Place a bead of 3M 5200 around each bolt, bolt hole and the perimeter of the appendage. This is all you need.
You don't mean I should leave air gaps do you on the join?

If you have some laminate issues at the fin root, you should determine what caused it. It's very likely the cracks you're seeing are a result of a keel that has been working back and forth (if an ever slight amount) for a number of years. You can reinforce the laminate, but it has to be done right or you're inviting trouble. From the nature of your questions and general understanding of the tasks involved, you should have a surveyor come out and look over the keel joint. Once the extent of the damage is understood, you can form a plan of attack for an effective repair schedule.
Yes I have had a surveyor look before, but his position was do nothing until you see a leak inside. However I want more confidence. When I did the rudder I saw what happens to stainless in saltwater.

The fin root looks pretty solid, no delamination that I can see. I think the crack was caused when the previous owner hit a rock. :eek:
But cracks in keels like mine are very common. Mostly if the crack does not weep or cause a leak inside you are ok, but I just want to check the keel bolts.

Thanks again for your thoughts.

[PAR]

A continuous bead of 3M 5200 around the perimeter of the fin, should keep out all the water. The ring around each bolt and hole is just added "insurance" in case water does get past the perimeter bead. The adhesive aspect of 3M 5200 is redundant, it's the sealant qualities you're after, which is exceptional in this case.

It's not uncommon to have stress cracks at fin roots. The surveyor is generally correct, in that don't worry about it. If truly concerned check the ballast bolt nuts in the bilge for tightness. If they're tight, then you're in good shape.

What many times happens is one or two bolts for some reason (like hitting something hard) gets stretched or other wise loosened. If these bolts aren't tightened right away, the ballast fin will exert increased loads on the remaining bolts. Now they're stretched a little with each hard slosh to windward, eventually getting loose themselves. This is the point leaks develop and keel bolts break (from flexing).

If the bolts are tight (all of them) they can't flex.

Each boat requires a fresh approach to dropping the keel. I've done a fair amount over the years and much prefer to drop the ballast then lift the boat.

If you're looking to just renew the bedding (3M 5200) and inspect the bolts, then the keel doesn't have to drop all the way off. Lower it down until you can see the threads appear at the hull/keel joint. This way you don't have an alignment issue jacking it back into position. I've had to remove and work on damaged keels and trust me, alignment can be a real pain in the butt when trying to manhandle a few tons of lead back into position so it can lift straight up, hit the holes and not bind half way up, etc.

Keel bedding is a job that needs to be preformed about every 20 years or so. Most wait until it starts leaking, but at this point you're risking other issues, such as bolt corrosion, keel movement mashing the surround laminate to bits, bent bolts, etc. I've seen keels that haven't been removed for 40+ years, but it's a risky game to wait it out. It doesn't happen often, but bolts can become so compromised that the damn thing can just fall off. Of course this will not happen while you're sitting having a beer at dock side, but rather while you're much father from shore then you can swim back to and heeled way over, in a freshening breeze with the rail well under. That's when the damn thing will let go. Fortunately most boats will float quite well on their flanks without the ballast trying to drag them to see Davie Jones. Lets just hope you can get out a distress call before the batteries flood so the USCG can come and drag your soggy butts to shore.

So, to answer this question, it's likely you'll not have to perform this task again. This assumes you don't bash it into hard stuff or other wise pick up some damage that can break the seal or stretch the bolts.

As a rule, which your surveyor suggested, if the bolts are tight, it's likely not to leak and if it's not leaking, it's probably tight enough to serve well.

If a boat needs a bunch of work or will be stored on the hard often, I like to see a nicely built steel cradle. If it's just going to have some repairs, maybe a new paint job, cutlass, etc. then stands will do. They do create some point loading, but for short amounts of time, they work fine. The yard will try to use as few stands as possible. Talk them into extra stands. On a boat like yours, it should have 5 stands down each side, with one under the stern and possibly one under the bow as well. You can't use enough stands, but you can easily damage laminate by using to few. Place them on internal structures, like bulkheads, center line, under chain plates locations or other wise the locally stiffened areas of your yacht.

The stress cracks on the fin root are a cosmetic issue and easily handled with some thickened epoxy. Grind down to good mat (yep, that's right, through the paint and gel coat) and feather the area back away from the cracks at least a few inches in every direction. Smear on a mixture of thickened epoxy (I'd use 50% milled fibers, 30% silica and 20% Q cells). This forms a dense, but fairable mixture. Apply is as smoothly as you can, but not quite flush with the surface, you want to be just a hair (literally) shy of flush. Next is a the cosmetic filler which can be micro balloons and some silica to add thickness and prevent sags. This mostly balloon mixture is smeared on to be slightly proud, then sanded down flush. With this type of repair and finish, the cracks will likely not reappear.

[matt2]

I Really appreciate your advice PAR, I think I have a much better idea now how to approach this task, thank you.

It's not uncommon to have stress cracks at fin roots. The surveyor is generally correct, in that don't worry about it. If truly concerned check the ballast bolt nuts in the bilge for tightness. If they're tight, then you're in good shape.
Yes the surveyor and I checked the nuts on top and they were all tight and dry. However, as I understand it being dry does not mean your bolts have not corroded since there are instances where people have sealed the washers and nuts on the keel bolts.
Each boat requires a fresh approach to dropping the keel. I've done a fair amount over the years and much prefer to drop the ballast then lift the boat.
I will use this method, then.
If you're looking to just renew the bedding (3M 5200) and inspect the bolts, then the keel doesn't have to drop all the way off. Lower it down until you can see the threads appear at the hull/keel joint. This way you don't have an alignment issue jacking it back into position. I've had to remove and work on damaged keels and trust me, alignment can be a real pain in the butt when trying to manhandle a few tons of lead back into position so it can lift straight up, hit the holes and not bind half way up, etc.
Yes, moving the keel and getting it back on was big worry. Having a frame that is strong enough to hold the keel but also allows me to move it up and down etc. So good suggestion not dropping it all the way.
Keel bedding is a job that needs to be preformed about every 20 years or so. Most wait until it starts leaking, but at this point you're risking other issues, such as bolt corrosion, keel movement mashing the surround laminate to bits, bent bolts, etc. I've seen keels that haven't been removed for 40+ years, but it's a risky game to wait it out. It doesn't happen often, but bolts can become so compromised that the damn thing can just fall off. Of course this will not happen while you're sitting having a beer at dock side, but rather while you're much father from shore then you can swim back to and heeled way over, in a freshening breeze with the rail well under. That's when the damn thing will let go.
I have been preparing the boat for some long term crusiing and some offshore stints so I want to make sure the keel bolts are A OK. The boat is more than 20 years old now, so good time to check the bolts. Checking them will also mean I can have full confidence in the keel.
So, to answer this question, it's likely you'll not have to perform this task again. This assumes you don't bash it into hard stuff or other wise pick up some damage that can break the seal or stretch the bolts.
Ok, that's great I would not want this to be a regular thing.
The stress cracks on the fin root are a cosmetic issue and easily handled with some thickened epoxy. Grind down to good mat (yep, that's right, through the paint and gel coat) and feather the area back away from the cracks at least a few inches in every direction. Smear on a mixture of thickened epoxy (I'd use 50% milled fibers, 30% silica and 20% Q cells). This forms a dense, but fairable mixture. Apply is as smoothly as you can, but not quite flush with the surface, you want to be just a hair (literally) shy of flush. Next is a the cosmetic filler which can be micro balloons and some silica to add thickness and prevent sags. This mostly balloon mixture is smeared on to be slightly proud, then sanded down flush. With this type of repair and finish, the cracks will likely not reappear.
Would you suggest applying any finishing coat or sealant over the lot once faired?

Thanks for that detail, that is exactly what I need to know.

[marshmat]

Hi Matt,

Once you're done fairing and sanding, I don't think you'd need much more than a solvent scrub and a couple of coats of primer (use the prep technique and primer recommended by your bottom paint supplier) before you paint the new antifouling on.

Do keep safety in mind as you do this. A couple of tonnes of lead can really hurt if it lands on your foot, and will put you in either the hospital or the morgue if it falls over. So always have a lot more supports than you think you need, and have a few safety straps tied back to something sturdy to catch the keel if it does decide to get away from you.

[michael pierzga]

Hi ...Ive removed and remounted a few keels in my time. Epoxy and microfibre is always used. Let me clarify....
To properly seal and distribute loads into the structure your boat, the top surface of the keel must precisely match its mating surface on the hull. Think of an engine and its cylinder head, a perfect machined fit with each headbolt under the same load.
This is your goal. ..... Mounting the keel is a two step process... the top of the keel and bolts are prepared in such a way that the epoxy will not adhere to them ...only to the boat. cover the top of the keel and elongated boltholes with this epoxy bedding compound, rest the boat on top and let it kick off.
Naturally you cleaned and prepared both mating surfaces and were careful in aligning the keel horizontally and vertically.
then lift off the boat from the keel again and now seal keel bolts and flange with bedding compound. Be careful with 5200. its an adhesive, next time you drop the keel.... expect damage to your perfectly prepared mating suface at the keel flange caused by this adhesive..
Every keel that I have removed was under the supervision of a naval architect...You should do the same...the job of removing and re-bedding a keel is not hard.
Small mistakes can have bad consequences.
Understand the correct keel bolt torque.... understand why your present configuration is not working.....CONSULT A Naval Architect. They are cheap compared to crane costs and double done jobs..

Mike

[matt2]

Thanks Mike, it is good to hear a different perspective.
Hi ...Ive removed and remounted a few keels in my time. Epoxy and microfibre is always used. Let me clarify....
To properly seal and distribute loads into the structure your boat, the top surface of the keel must precisely match its mating surface on the hull.
Yes this sounds reasonable.
Mounting the keel is a two step process... the top of the keel and bolts are prepared in such a way that the epoxy will not adhere to them ...only to the boat. cover the top of the keel and elongated boltholes with this epoxy bedding compound, rest the boat on top and let it kick off....then lift off the boat from the keel again and now seal keel bolts and flange with bedding compound.
Ok, I think I see what you are getting at here. You are saying you want a keel to hull joint with no play, i.e. that is completely snug so the any keel forces are distributed over the widest possible area. To do this you are suggesting creating a keel landing platform on the hull. To achieve this I think you suggest using a barrier (say gladwrap plastic or ...?) on the top of the keel. Then applying a layer of epoxy paste over the entire top of the keel say 2 inches thick. Push the keel up into the position you want and I guess tighten the keel bolts to approx where they will be. Wait for the epoxy mix to go off, and drop the keel again.

Ok then I think you suggest sealing the keel bolts with 5200, I suppose by placing a ring of 5200 around the base of each bolt, yes? You then mention using the bedding compound (5200) on the "flange", what is the flange? Is the flange the entire top of the keel?
Every keel that I have removed was under the supervision of a naval architect...You should do the same...the job of removing and re-bedding a keel is not hard.
A naval architect, do you mean surveyor or accredited yacht designer or someone with a degree and working in Naval architecture?
Understand the correct keel bolt torque.... understand why your present configuration is not working.....CONSULT A Naval Architect. They are cheap compared to crane costs and double done jobs..
This is not a production yacht, so there is no manual on the correct torque. So I was going to use an enormous torque wrench to measure the current torque and then match that. If I cannot get a large enough torque wrench then maybe a scale applied at a fixed length or by strapping say a broom stick to the base of the wrench and measuring the difference between the broom and lever at a specific distance.

I have attached rough computer drawing of the keel set up as it is now. I think the landing platform you mention is already part of the set up, but perhaps I need to check that there is an exact match between the surfaces and if not build up the landing platform in the way Mike describes.

Thanks posters, different opinions are very helpful in teasing out the important concepts.

[michael pierzga]

Well Matt, its possible that an experienced marine surveyor is good for your job...I prefer naval architects. They understand the "numbers ", have had keels installed on many of their own designs, have made many MISTAKES and can have a good look at the internal structure to recommend detail changes. A good shipyard will have the experience. Removing keels is a typical job. Your keel detail looks straightforward.

As for a mold release on top of the keel...well once the surface is cleaned and primed I like to use that transparent, 2 inch wide, Mylar packaging tape that you can buy at any hardware store, you can also wrap it around the bolts. a fibre glass TUBE fabricated to the diameter of your keel bolts and slipped over the threads is a very elegant and professional way to keep the threads clean and form a nice epoxy bog keel bolt hole.. Plastic sheet can work, it just messy and slippery to work with.

Almost always the damage that must be repaired is on the INSIDE of the boat from one or more keel bolts compressing the inside of the keel flange structure. Pay close attention to this area. Remember the engine cylinder head analogy. The surface of the inside should be parallel to the backing plate...washers.... and perpendicular to the keel bolts..
Depending on the inside details of your boat. this could be an oversize metal backing plate bedded into epoxy bog. The boat is lowered onto the epoxy covered keel. you go inside, epoxy microfiber the bottom of you backing plate, washer assembly. Gently lower in place and then gently tighten the keel bolts to squash the epoxy out and create a perfect bed.
If I remember correctly. Gougeon brothers.... in one of thier books has a very good article on mounting keels .
You will be surprised with how little torque is applied to keel bolts. A keel HANGS from the bottom of a boat.
When you remove the keel CLEAN the keel bolt threads perfectly...the nut should spin onto the bolt.
Be careful with strong adhesive 5200. I removed a 12 ton keel from a racing yacht. with keel bolts freed up and the boat suspended in the travel lift.... the keel was still hanging from the bottom of the boat. Very much work to free this adhesive bond.
The keel must be supported once it is free of the boat. We make a box frame around the keel, out of scaffolding steel pipe, using those nice scaffold pipe clamps to hold it all together.
With the boat out of the water standing on the hardtop you might consider building a 8 or 12 inch deep plywood box around the keel bulb and on top of the shipyard hardtop... then pouring cement into this box. This will form a nice little cement shoe that will hold your keel in the same for and aft trim while your keel is standing in the shipyard. when your finished just hit the concrete with a hammer and it will fall to pieces.

Mike

[michael pierzga]

mold release via Gougeon brothers

http://209.20.76.247/ss/mold-release-pva-and-hairspray/

I couldnt find the keel mounting article online...perhaps look harder Mike

[matt2]

Mike, just want to clarify my understanding. Are you saying that your technique is to prepare a epoxy mix landing pad on the hull but then once that dries you use 5200 to as the sealant between the keel and the hull? Or do you mena that entire keel - hull joint is epoxied?

Gently lower in place and then gently tighten the keel bolts to squash the epoxy out and create a perfect bed.
If I remember correctly. Gougeon brothers.... in one of thier books has a very good article on mounting keels .
I did a search and found these two books.

The Gougeon brothers' book looks promising and is very popular:
WEST System - The Gougeon Brothers on Boat Construction
The Gougeon Brothers on Boat Construction, 5th Ed.
http://www.jamestowndistributors.com/userportal/show_product.do?pid=4340&familyName=WEST+System+-+The+Gougeon+Brothers+on+Boat+Construction

This one could also be interesting "Frame, Stem & Keel Repair" by Peter Spectre.
http://www.jamestowndistributors.com/userportal/show_product.do?pid=2522&familyName=Frame%2C+Stem%2C+and+Keel+Repair
The keel must be supported once it is free of the boat. We make a box frame around the keel, out of scaffolding steel pipe, using those nice scaffold pipe clamps to hold it all together.
With the boat out of the water standing on the hardtop you might consider building a 8 or 12 inch deep plywood box around the keel bulb and on top of the shipyard hardtop... then pouring cement into this box. This will form a nice little cement shoe that will hold your keel in the same for and aft trim while your keel is standing in the shipyard. when your finished just hit the concrete with a hammer and it will fall to pieces.
So do you lift the boat or the keel? If you lift the keel how do you do that?