Rusted/Stuck Centerboard

Rick · Post by **Rick** » Fri Nov 10, 2006 5:25 pm

Hi all.
I've been restoring an old Aquarius 21 trailor sailor. Tim's been helpful with suggestions to repair several holes & cracks in the hull - which are completed. Now the fun is beginning. The last 2 weeks I've been trying to get the centerboard to drop - with no luck. I realize most of you aren't dropping centerboards, but I'd appreciate your expertise and suggestions.

I began with finesse, but I'm concerned that my present course may create another large hole where the centerboard and centerboard box used to be!!

I've used a hack saw blade, stiff paint scraper, aluminum yardstick,
2 lb hammer, new 3 lb hammer, now broken handled sledgehammer,
1/16"x1"x36" steel yardstick, WD-40, PB Blaster, 12" sawzall
blade, ... I've been scraping and hammering and it still hasn't
dropped an inch!

As background, she was sailed in the ocean some 9 years ago, and has
spent the intervening time on her trailer - swelling her rusty
centerboard.

Actually, I've dismantled the top of the centerboard box, which gives me access to the forward half of the box. I've removed the pivot pin
and scraped and banged all of the rust out around the centerboard,
except for the forward 6" around the pivot pin area. It's rusted so
tight there that I can't insert even the hacksaw blade between the
fiberglass and the rusted board. The board is just one mass of rust
that completely fills the centerboard slot in this forward area.

If anyone has any suggestions before I head out this weekend and buy
a bigger sledgehammer, I'm all ears!!

Rick

Figment · Post by **Figment** » Fri Nov 10, 2006 5:34 pm

Buy a bandsaw blade made for cutting metal, and break the loop.
Slip it down alongside the board and have one person work the top and one work the bottom, just like a lumber-sawing pit from days of old. That should let you get up into that "big mass of rust" in the forward part.

If I recall correctly, iron expands 10x its thickness when it rusts, so I'm sure there's PLENTY of pressure in there.

Mark.Wilme · Post by **Mark.Wilme** » Fri Nov 10, 2006 5:40 pm

We had the marina drop the CB on our Elite 32 last Spring and they sweated and grunted at it for almost half a day before they got the beast out. They even left the boat hanging in the slings overnight, that didn't help either. Even after they had drilled out the pin (2" dia Nylon) it wouldn't come down and yes it looked like iron puff pastry !!

I tried like heck before that from above to get it to swing down to no avail.

Once they got it out they did sandplast the whole keel before refinishing it (final coat = 2 coats of hard primer, not ablative) and I did the work inside of the keel trunk chipping away with a selection of modified chisels, scrapers, gardening tools etc before sloshing as much bottom paint as I possibly could back in there.

Sorry I couldn't be of more help

Good luck

Rick · Post by **Rick** » Fri Nov 10, 2006 7:36 pm

I'll try the bandsaw blade - sounds like a good idea. I'll let you know if it works! Thanks.

Rick

Rachel · Post by **Rachel** » Fri Nov 10, 2006 8:54 pm

Rick.

This might be way more information than you want (or than you need if the slick-sounding lumberjack-bandsaw-blade trick works), but there is a fellow who has recently completed a huge centerboard surgery project on his Montgomery 23 who has it well documented with photos and information.

The older Montys have a cast-iron swing keel and stub keel ballast made of steel punchings, so they've had some problems. This guy ended up replacing all his ballast with lead; the project kind of mushroomed - you know how they do. But he did get it all back together and get out sailing :-)

Here's the link:

http://pic1.funtigo.com/havasumontgomer ... 11458&cr=1

Rick · Post by **Rick** » Sat Nov 11, 2006 10:47 am

Rachel,

Thanks for the link - it's strangely comforting to see the similar suffering of others!! It appears that he resorted to the "biggest hammer I can find" technique and it worked - eventually. That will remain as plan B if the bandsaw blade doesn't work. It's also been suggested that I try the sawzall again, being very careful about cutting into the fiberglass. My "delicate" options are rapidly falling by the wayside!

Rick

Ancient Race · Post by **Ancient Race** » Sat Nov 11, 2006 12:45 pm

I'm feeling glad my centerboard is skinned in fiberglass and drops freely.

I'm sure the caution is unnecessary, but since my enthusiasm often exceeds my awareness, I'll remind you anyhow that in case it does let go suddenly, be careful you and yours aren't between it and the ground.

Greg

MQMurphy · Post by **MQMurphy** » Sat Nov 11, 2006 1:02 pm

Rachel - thanks for that link. Very inspiring to see someone doing a thorough job and documenting the steps so well. I guess it reminds me of the Triton site that I came across last year ;-)
I need to be reinspired every once in a while.

Mark.Wilme · Post by **Mark.Wilme** » Sun Nov 12, 2006 11:37 am

That is some ordeal - not just the CB but the replacemet of the ballast in the keel too- I had assumed he would be heating it and pouring it, had not envisaged he would use lead shot and epoxy.

wow

Peter · Post by **Peter** » Sun Nov 12, 2006 1:56 pm

Great link to the M-23 rebuild, Rachel. Goes to show that ANYTHING can be repaired if you really want to! .... and you do it yourself !!

Rachel · Post by **Rachel** » Sun Nov 12, 2006 2:38 pm

Peter wrote: Goes to show that ANYTHING can be repaired if you really want to! .... and you do it yourself !!

Indeed. Can you imagine how much that would have cost to have someone else do for you? <shudder>

It was kind of neat to see the surgery.

Rick · Post by **Rick** » Sun Nov 12, 2006 8:56 pm

Just thought I'd update with the progress - or lack thereof. I used the lumberjack bandsaw technique, sawzall, hacksaw, steel and aluminum yardsticks, sledge hammer, cold chisels ... aren't you glad you don't have a centerboard!! It's a 4 foot centerboard that's now rust free for all but the last couple of inches around the pivot pin area. I also used a hydrolic jack to try to lift the stern end of the board to try to get it to move. It raised the stern of the boat, which is now 1/2" off the skeg keel support with all the weight on the centerboard. Still no movement of the board! It's amazing how little jammed rust can lock up the board. I've decided to give it one more try and if unsuccessful, I'll resort to cutting the fiberglass around the board and just reglass it later.

Right about now, bottom sanding grunt looks pretty good!

Post by **Tim** » Mon Nov 13, 2006 7:31 am

I just can't understand the use of cast iron in any aspect of any boat construction. Everyone knows that it's not suitable because of its propensity to rust, and its severe expansion when it does rust. This thread is a case in point, and cast iron centerboards (and keels and other parts) cause these sorts of problems all the time. The same applies to mild steel backing plates, chainplates, and the like that I've seen on many boats, most notably a popular traditional brand. These steel plates turn into Spanikopita after a few years of leaks and salt air.

I know, I know: it's cheap and easy for the builder. But I've always thought that this was an inapplicable excuse. Builders/manufacturers should care about what happens to their product a few years down the road, not just about the cheapest way to slam the thing through production and into customer hands. This applies to any product.

Apparently I have a naive view of economics.

In any event, Rick, sorry to read of your troubles and the frustrating attempts to solve them. Good luck with the ultimate fix!

George ( C&C 40 ) · Post by **George ( C&C 40 )** » Mon Nov 13, 2006 8:54 am

Hi Tim,

If I remember correctly from when I was researching the best way to clean up the cast iron centerboard on my C&C 40, cast iron is used in centerboards because it does not bend. It either maintains its shape or it shatters. This is why they stopped making centerboards out of bronze -- too many race boats were showing up in Bermuda with bent bronze centerboards that wouldn't go back up in their trunks. Doesn't explain why anyone would make a keel out of cast iron though.

George

Duncan · Post by **Duncan** » Mon Nov 13, 2006 9:48 am

Tim wrote:I just can't understand the use of cast iron in any aspect of any boat construction. Everyone knows that it's not suitable because of its propensity to rust, and its severe expansion when it does rust.

Should I be worried about my internal cast iron ballast, then? I haven't heard any horror stories about expansion in that application (which seems like a common one), and it "looks ok to me", but now I'm wondering.

Post by **Tim** » Mon Nov 13, 2006 9:55 am

Duncan wrote:Should I be worried about my internal cast iron ballast, then? I haven't heard any horror stories about expansion in that application (which seems like a common one), and it "looks ok to me", but now I'm wondering.

Not unless there's a reason to worry--that is, if you have any external or other visual signs that there may be a problem, then perhaps you have a worry. If all seems sound and fine, though, then don't let it keep you up at night.

I've frequently had to allay fears about cast iron internal ballast in this way. I'm firmly of the belief that lead is better, but if the boat has internal cast iron that's showing no signs of trouble, then it's likely to be no trouble.

Quetzalsailor · Post by **Quetzalsailor** » Mon Nov 13, 2006 9:59 am

I recall that rust is harder than the cast iron. If you can use a 12" hacksaw blade, you can use a carbide-coated rod blade as made for ceramic tile.

Sooner or later, you'll cut to a point where the last of the rust collapses and the blade is caught between the board and the 'glass. Be sure to wedge between the board and 'glass with something removable, say a stack of steel shims long enough to get a grip on.

If you decide on destruction of the 'glass look carefully at what gives the sides of the trunk its stiffness and see whether a cut there might be easier to fix later. For example, perhaps the trunk is topped or ends in such a way that a single longitudinal slice might allow the trunk to widen.

Rick · Post by **Rick** » Mon Nov 13, 2006 2:49 pm

FYI this is my first try at answering others quotes. I hope it makes sense.

Quetzalsailor wrote:I recall that rust is harder than the cast iron. If you can use a 12" hacksaw blade, you can use a carbide-coated rod blade as made for ceramic tile.

I've used the carbide-coated blades for fiberglass. Do you think they will do a better job than the metal cutting sawzall blades? I just picked up a 5 pack of 12" sawzall metal cutting blades and the carbide ones were hanging nearby.

Quetzalsailor wrote:Sooner or later, you'll cut to a point where the last of the rust collapses and the blade is caught between the board and the 'glass. Be sure to wedge between the board and 'glass with something removable, say a stack of steel shims long enough to get a grip on.

That hasn't been a problem so far. The board pocket is solid rust at the bottom under the pivot pin and forms a triangle to a narrow top near the forward part of the board above the pin. I keep chopping out the rust and knock the chuncks to the open rear area of the pocket an force it out to the ground. I've gotten the steel "yard stick" shaped pieces I use to bang out the rust stuck, but I then insert another piece nearby and have been able to work each one free by also moving it rearward.

Quetzalsailor wrote:If you decide on destruction of the 'glass look carefully at what gives the sides of the trunk its stiffness and see whether a cut there might be easier to fix later. For example, perhaps the trunk is topped or ends in such a way that a single longitudinal slice might allow the trunk to widen.

Good idea, but I'm not sure that it would be flexible enough to give me access to the rust. The trunk wall is thinner at the top and grows to about 1/2" thick fiberglass near the sole. I don't know how thick it is when it passes from the cabin sole through the 5" skeg keel. That's the area where most of the rust is located. My thought was to cut a vertical line on each side about 5" from the front of the trunk, down to ~ 4" above the sole and then a horizontal line connecting them around the front. I'd remove the "L" shaped piece of fiberglass, work on the rust up close and then glass the section of the trunk back in place. Of course, I haven't any idea whether this is safe or sane, ... but it will give me access to the *X!*!! RUST! Any comments, opinions, ideas ... will be greatly appreciated before I grab the sawzall next week.

Rick

Quetzalsailor · Post by **Quetzalsailor** » Tue Nov 14, 2006 10:03 am

I would not have thought rod saws would be useful on 'glass. Surely they'd fill with resin(?). I thought folks had bought carbide toothed blades for their sawzall, which I read with great interest. I destroyed two bandsaw blades and a new carbide radial saw blade on my layups of 3/8" fiberglass which I'd made for through-hull backup blocks.

I don't have any idea what the construction of your 21 footer is or whether the top of the case is open or closed. As the bottom of the hull of our 38 footer is about 9/16" thick at the turn of the keel, and the sides of the keel itself are about 1/2" (I installed three new through-hulls and closed two), I doubt you're gonna' be anywhere as heavy as that. The trunk might be a separate molding which was tabbed to the hull which would give you locally thick areas; even so, adjacent flattish areas will absorb the flexure if the tabbing is resistant!

The disadvantage of cutting areas out is that you get to put them back by scarphing or using lots of extra material.

cantstopnow · Post by **cantstopnow** » Wed Nov 15, 2006 9:34 am

Has anyone tried using an application of diluted Muriatic acid (I think 10%) to free up a stuck centerboard? This works great for freeing up rusted tools. Just drop the rusted unusable pliers into a plastic bucket with 10% muriatic acid and 90% water, leave it over night and in the morning add baking soda to the mix till the fizzing stops and the acid is neutralized. Then just dry and lubricate. It seems to me that a fiberglass hull would not be bothered by the acid but that the expanded rust should be reduced sufficiently to free the board.. Warning! I have never tried this method on a stuck centerboard. You do have to be concerned with good ventilation as the fumes speed up rusting on nearby surfaces. Neutralizing with TSP or baking soda is also very important.

Rick · Post by **Rick** » Wed Nov 15, 2006 11:43 am

It's been suggested that Phosphoric acid and/or muriatic acid may be helpful in removing the board. I'm hesitant for three reasons. First, I'm not sure if the acid may remove some rust but convert the remaining rust into something even harder. Second, I'm not sure that the acid could get far enough into the mass of rust to have an effect. Third, I don't like the idea of returning under the board to continue cutting, banging, etc. after I've added acid to the falling rust.

I got a look at a picture of the skeg keel of a similar A23 and it appears that there is about 1/2 inch of fiberglass surrounding the keel. Assuming the same thickness inside the trunk where it passes through the skeg keel, my next plan of attack is to trim some of the glass on each side of the rusted board. This will be much easier to remove, and apparently has sufficient thickness to avoid exposure of the ballast.

What do you guys and gals think of this idea?

Rick

Duncan · Post by **Duncan** » Wed Nov 15, 2006 1:24 pm

...buy a bigger sledgehammer...

In all seriousness, that might be just the thing. I think you're basically overcoming friction, and I'd hate to start cutting into the structure of the boat before giving it a few really persuasive whacks with a big sledge. Once she gets started, things may speed up from there.

(This comes from my own experience with a skeg which had been knocked partway out of its slot. I tried to jack it back in, but all that did was lift the whole (5000 lb) boat. Then I gave into local advice, and found that steady sharp whacks with a good sledge seated in just right, with no collateral damage.)

Or as a friend said on another occasion, when I tried to wimp out by using a rubber hammer -
"No, no, what we need here is IMPACT" :)

Rick · Post by **Rick** » Sun Nov 19, 2006 11:06 am

I've finally got the board moving. I started with the hacksaw blade in a saw handle that held one side and allowed me to fit almost the entire blade into the trunk. I cut about half way into the remaining rust on one side (~ 2") and then used a sawzall blade to bang the rust free. I alternated using a sledgehammer to try to get the board to drop and a hammer on the bottom to try to loosen the rust. Eventually I got some rust to drop and when the remaining rust was about 2" around the pivot pin area, the sledgehammer finally moved the stern of the board down. I worked it up & down eventually getting the board to drop about a foot in the stern. The front is rotating, but the sledgehammer still can't get it to drop. That's my goal today. Thanks for all the advice.

BTW, I knew she hadn't been in the water for at least 8 years, so I thought that was why the board was so bad. When I removed the board winch, I noticed that the wire had sawed through the wood, enlongating the hole to the board. It seems that a balky board had been an issue even when she was being sailed. A little maintainance then might have saved someone alot of time!!

Rick

Ric in Richmond · Post by **Ric in Richmond** » Mon Nov 20, 2006 8:46 am

What about spreading the trunk?

Most EMT's (Hudson....a little help here?) would know about them.

Like a pillow that is inflated. The pressurized air can lift cars off limbs or trapped people.

Might give you a bit of room or break the grip of that rust.

Something like this!!

http://matjack.com/hipress.htm

Rick · Post by **Rick** » Mon Nov 20, 2006 9:29 am

Ric in Richmond wrote:What about spreading the trunk?

The board is now easily going up and down in the back, but it's still got a little rust near the pivot pin that's preventing it from dropping completely. I've got to keep hacksawing the front area to get through the last inch or so. Thanks for the suggestion to expand the trunk. I don't know if it would work since the area where it's sticking is at the bottom where the skeg keel surrounds the trunk. I think a little more "finesse" with the hacksaw and sledgehammer should do it.

Rick

Summersdawn · Post by **Summersdawn** » Mon Nov 20, 2006 1:08 pm

I think a little more "finesse" with the hacksaw and sledgehammer should do it.

Sledgehammers just exude finesse!

Rick · Post by **Rick** » Mon Nov 20, 2006 5:06 pm

The key is not to hit the overhead on the gentle upstroke!

Rick

stone · Post by **stone** » Mon Feb 05, 2007 5:48 pm

Sounds like I just did the same thing.Is your board re-usable? Mine is pretty spent ,but still not bad for 40 years in saltwater. Are you sure its cast iron? Mine is 3/8th steel. I am just going to buy a new sheet of steel (4x8) and find someone with a plasma cutter and have a new one cut out.

Rick · Post by **Rick** » Mon Feb 05, 2007 6:52 pm

Congrats on getting the old CB out! I can relate to how much fun that is!

I don't know if my old CB is reuseable yet. The original owners manual states that its original dimensions were 2' x 4', constructed of 1/2" steel and weighing 165 lbs (although some website info suggests that it was only 3/8" and probably lighter). Mine weighs ~120 lbs now, so it may have lost 45 lbs of steel to rust. I don't think that weight loss will be too significant. Also, my old CB has some nice aerodynamic lines ground into its leading and trailing edges that the new one wouldn't contain. I don't know if that matters.

What I also need to find out is how much it costs to sandblast the board, weld new steel around the pivot pin hole, redrill the hole, and weld new steel where the wire rope attaches to the CB. I've identified some welders, but haven't gotten any quotes. I did find a seller on the internet who sells CBs for my make and model (Aquarius 21). The CBs look good, but I need to compare his price with shipping to a potential repair.

Let me know if you want to know the cost info I get.

Post by **Tim** » Mon Feb 05, 2007 7:11 pm

I think any centerboard needs to have a foil shape in order to provide the proper lift. A piece of sheet steel without some shape is probably not a great idea if you want to maintain the performance of your boat. A centerboard is a lot more than just a hinged appendage; when lowered, it provides significant additional lift that helps the boat perform as designed.

Rick · Post by **Rick** » Mon Feb 05, 2007 7:39 pm

Thanks for the info on the benefits of the airfoil shape of the old CB. The seller of the new one suggested that the plain shape of his new sheet metal CB wouldn't have much effect on performance. My instinct suggested that if the builder put in the effort thirty years ago, there must be a reason.

My question is if I have to purchase a new CB, how do I recreate its airfoil shape? Is that something I can do with a grinder or some other tool with a reasonable amount of effort? I love the PC 7335 that Tim recommends, but I've been working on fiberglass, not steel. I have a small 4" grinder, but how effective would it be on steel plate?

Rick

stone · Post by **stone** » Mon Feb 05, 2007 7:57 pm

The quote I got for mine was $600. (way to much) A 4x8 3/8 thick plate steel is around $250.00. I figure a hour charge with a machine shop to have it cut About $50.00 to have sand blasted and then whatever it costs for four coats on Interprotect. Where are you located ? I am going to have alot of extra metal? You can easily grind an edge on the board but a foil doesnt really matter until you start getting into 3/4" and above. That being said I will probally grind an edge on mine. I am also going to check the Community college tomorrow and see what I can get done there. We have alot of boat building/welding classes etc.

stone · Post by **stone** » Mon Feb 05, 2007 8:24 pm

Edit Dont think a foil matters much until you go 1/2" thicker or above.

Jason K · Post by **Jason K** » Mon Feb 05, 2007 8:44 pm

My question is if I have to purchase a new CB, how do I recreate its airfoil shape?

I would try to find the same model boat with a CB in good condition and make some plywood templates.

Rick · Post by **Rick** » Mon Feb 05, 2007 9:11 pm

I'm on Cape Cod, Mass. I imagine the shipping charges for steel make sharing a sheet unrealistic. I'll check the prices around here and let you know what I find out.

The price for the precut 2' x 4' CB I found was $250, without shipping, but it included the wire rope and stop plate. It isn't shaped at all. Do you plan to grind an edge with a hand grinder?

stone · Post by **stone** » Mon Feb 05, 2007 9:50 pm

Cape Cod? You must be freezing!!!Thats sounds like a good price. Are you saying the shape is already cut it just has no edge? Yea I was just going to grind a trailing edge on mine with a hand grinder. (four inch makita)

Rick · Post by **Rick** » Tue Feb 06, 2007 1:07 pm

We're freezing - but imagine how Tim and the gang in Maine are doing!
You're right that the CB is already cut, but has no tapered leading or trailing edge. I also have a 4" Makita grinder, so if I get the precut CB, I may try to grind the edges. First, I want to get some steel prices locally to compare.

Rick

Quetzalsailor · Post by **Quetzalsailor** » Tue Feb 06, 2007 2:03 pm

Plenty of boats were born with plate centerboards. The Finn dinghy has a 1/4" thick aluminum centerboard so there's not much opportunity to form a foil cross section. The rounded leading edge extends aft only about 3/8"; the tapered trailing edge extends forward only about an inch. The Flying Dutchman rudder and centerboard were originally (1950s) made with 3/4" thick wood but were shaped about 3" back from the leading edge and about 4" forward from the trailing. FD now are allowed rudders of about 1 1/8" thickness and are truly foils in section. The allowable centerboard case width sets the board thickness for the FD as well as this boat.

Several hours with an angle grinder will do wonders with the raw steel plate, paying strict attention to symmetry and leaving, say, a nice square trailing edge of about 1/16" thick.

Post by **dasein668** » Tue Feb 06, 2007 2:48 pm

Rick wrote:We're freezing - but imagine how Tim and the gang in Maine are doing!

I haven't seen anything less than -6 this week. And 40mph wind gusts. T'ain't no thang! ;-D

Rick · Post by **Rick** » Tue Feb 06, 2007 3:42 pm

I haven't seen anything less than -6 this week. And 40mph wind gusts. T'ain't no thang! ;-D

We've had lows in the 5 - 10 deg range - warm to you guys. I'm looking for volunteers to walk my 2 yr old Irish Setter @ 6 AM in these warm temps - anyone want to venture south to balmy Cape Cod?

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