Swing Keel/leaded centerboard delaminating

[Sean Seward-Katzmiller]

Swing Keel/leaded centerboard delaminating

I need some advice how to best clean and reconnect a leaded keel in which the lead on the top 2 ½” is separating/folding away from the aluminum alloy fin. What is a good way to eliminate remaining oxidation of lead and aluminum? (I have scraped out all the white crust and gook that has accumulated between the aluminum and the lead, but there is still a film and remaining tiny pockets) What is the best way to “glue” lead back to aluminum alloy fin? A primer and then epoxy? Should I consider melting the lead back to the fin? Has anyone ever done such a thing?

My plan:

First, I believe that the keel is structurally sound; only the top 2”-3” of lead has delaminated from the aluminum. My basic plan so far is just to find some sort of anti-rust like primer to stop any further oxidation and then epoxy the lead back to the aluminum; (squishing it back together with c clamps and the like). I would fill in any cracks with epoxy and filler and grind back excess lead if it does not return to original width dimensions. I will enclose the finished body in a membrane of fiberglass protecting the body from salt water and oxidation. Is this a good plan? Should I consider torching the lead to melt it back into proper position? Any other great ideas?

Details of boat, keel and cause of problem:

Boat and keel: this is a Newport Neptune 16 with a swing keel. The keel has 200 lbs of lead set onto a approx. 4 foot ½” x 14” aluminum centerboard (see photos below which show a sample swing keel and shows how the lead is attached to the fin; in the second foto, the keel is broken and shows only the upper section of the lead and how it was attached to the fin; THIS IS NOT MY KEEL).

Cause of problem: I messed up the keel when I repositioned the keel in the trunk by using a higher eye hole on the swivel axis of the swing keel and I did not reset the crib of the trailer to properly give space for the new position of the keel. The result was a boat sitting on the trailer with all rear weight resting on the centerboard. The wood ribs on the trailer were not raised enough to carry the boat and the hull rested on and squished/sandwiched the top 2” of lead on the keel. I have since changed the holding of the boat which allows the boat to properly rest on the trailer ribs…that problem solved.

THIS IS NOT MY KEEL!
Thank you for your help,
sean

 

[CloudDiver]

Pictures of YOUR keel would help. This shouldn't be too difficult of a fix and I doubt re-smelting any lead will be required.

 

[Sean Seward-Katzmiller]

here are the best photos I could do this morning.....

 

[CloudDiver]

I've rarely seen lead against aluminum causing dissimilar metal corrosion, but obviously it happens although not as serious looking as stainless steel against aluminum. I think the delamination was caused the formation of that corrosion scale which can be very powerful in its ability to expand and push outward. From your description in words I was having a hard time picturing it in my minds eye, but seeing the pictures I can now see what you meant about the top two inches of the lead ballast.
- Can the lead ballast be removed from the aluminum keel? Its not totally necessary to do this but it might be helpful to clean out all the scale and the re-bed the whole thing in thickened epoxy.
- Weather you can remove the lead ballast or not, the scale needs to be cleaned off so you get good adhesion with epoxy. Don't waste your time grinding or sanding, all you do is impact the scale fragments into the metal pores. Go to a welding supply store, buy a gallon of heavy duty metal cleaner/degreaser/de-scale. (Air-Gas is a good national chain, just Google them) The active ingredient should be phosphoric acid (it is a mild solution), a gallon should cost between 12 and 14 bucks. Get a 40 gal or so rubber-maid trash can and fill the bottom with water, hot water works better. Pour the whole gallon of de-scaler into the water and lower the lead ballast into the trash can with a hoist, the water level need to cover the lead ballast. Let it soak overnight and then rinse it very well. That should very effectively remove the white scale deposits and leave it very clean. Let it hang dry and use a heat gun to ensure all the moisture evaporates.
- I'd suggest sand-blasting to get rid of all the rest of the paint but your keel doesn't appear that big. You get away with power sanding the rest of the keel, but a quick 30 minute sand blast will save you some tedious work and leave the best surface for epoxy to grip to.
- Lead is very soft... you might be able to bend those delaminated sections closer to the keel with just some C-Clamps or gently pound it with a soft mallet. If you heat it up don't get it too hot. Even after you bend it closer to the keel there should be enough gap for epoxy to flow in between the lead and aluminum.
- Get some epoxy and colloidal silica adhesive filler. If you can bend the lead back closer to the keel where you have a smaller gap to work with, the trick is to mix the silica into the epoxy only enough so that it stays liquid and will still flow just enough. Use some masking tape to seal off one side or all sides except where you will pour from, be creative.
- if you are able to remove the lead ballast from the aluminum keel (this is the ideal situation) then you can bed the entire ballast onto the keel with epoxy thickened to mayonnaise consistency.
-Once you have lead ballast/delamination, epoxy bedding issue taken care of you can decide if you want to re-enforce the leading edge of the keel with 6 oz glass tape. You can also put a tape layer on the trailing edge, the ballast to keel joint, or any other critical areas. You'll have to using some firing compound to smooth everything out after.
- I'd highly recommend using Interlux Interprotect 2000 epoxy barrier coat. I'm willing to say a one quart kit is enough to put 2 or 3 rolled on coats on that size keel. You have to use it all up within 5 hours because its epoxy 2 part mix, so if you buy a gallon you'd want to have something else you want to barrier coat like the rudder to use up the paint. On top of this you can use anti-foul paint or if you only dry sail the boat you put on a glossy topcoat.

 

[CloudDiver]

I'd also recommend getting rid of that wire thimble, that is an accident or corrosion waiting to happen. Cut that thing off and clean the hole out very well. Fill the hole completely with epoxy resin. Once cure use a small drill bit and put a pilot hole through the epoxy center, careful to drill square to the keel and dead center. Keep using that small pilot hole as a locator when if you decide to add 6 oz tape to the trailing edge (the fiberglass will help make the area stronger and prevent corrosion). After you finish fairing and painting, find the right size stainless shackle and drill the pilot out to the right size to accept the pin. A smooth shackle won't dig into the keel and the epoxy liner you created will prevent the stainless from coming into contact with the aluminum and corroding.

 

[Sean Seward-Katzmiller]

CloudDiver,
Thank you for the suggestions.

My focus to cure oxidation is in the area between lead and aluminum. I believe that delamination began with a physical squish load on the keel and it probably worsened over the last two year period when it was getting exposure to salt water every few months. Thus the crusty goopy white layers (lead, aluminum oxidation or both) built up in the crevices and probably, as you say, extended the separation. I want to avoid a replay of this. Therefore, I want to purify these crevices and I will probably use your suggested stuff.

I'm not so sure I want to "clean" the entire keel. This is my reasoning; there are three sections of keel. Section 1 is the top segment (3") which consists of swivel head of swing keel and is held tight by two "L" brackets of stainless steel. I previously painted this part of the fin with an anti-rust paint but did not cover it with an epoxy coat. I believe that any fiberglass or epoxy here will just break away under heavy Swivel friction. I want to leave this as metal to metal and grease it well to facilitate easy swing. I can repaint it every few years to minimize oxidation. I can see in my photo that i acutally left the top 15" painted with anti-rust paint and not covered with epoxy. After reading your suggestions I will probably cover all of the fin with epoxy except the head (top 3"). Section 2 is the 1/2" thick blade of keel below head and above lead ballast; I previously painted this with an anti-rust paint and then covered it with epoxy. This time I did find some pockets where oxidation occurred under the paint and epoxy, but in general it has held up well. I don't need a perfect foil and the current foiled shape of the aluminum is sufficient. I'm tempted to just clean out the pockets and repaint with anti-rust paint and cover with epoxy. Section 3 is the lead ballast connected to aluminum fin. Here I want to use your plan to purify, close/glue and seal. I would move the point of transition from section 2 to section 3 about 2" above the joint where lead ballast begins. below is full side view picture of MY KEEL.

What do you think? Is this cheap way a little too cheap? Is there a much better anti-oxidant paint or perhaps it is better to just coat the cleaned aluminum with epoxy as you have already suggested. What would you do at the head, where the keel swivels between metal brackets and will experience a lot of friction and abrasion?

 

[Sean Seward-Katzmiller]

here is photo