Bolts for Steel Keel - Bronze? Hot Dipped Galvanized?

[Jeff in Boston]

@Rumars

Agreed that bilgeboards would be better and dampening rolling. I don't think I will have to add those, but it is possible.

The boat was designed to rest most of it's weight on a 2200 lb keel that extends a certain length. I figure a keel that weighs 800 lbs that extends a bit farther back won't be an issue, especially if I put in some fiberglass in the rear between the hull and plate keel to avoid any bending loads. Do you think I am missing something here?

You are right that doing it in the water isn't smart. I'll skip that. But it is important that I be able to check the bolts without dropping the keel and breaking the sealant.

For the stainless bolts... you expect they will be fine as long as I keep them dry? In this design the bottom of the bolt heads are about 1.5" up from the very bottom so they shouldn't actually be wet very often.

 

[Rumars]

You are looking at it the wrong way. The boat was designed to have a 2200lbs keel suspended from the hull at a certain place, and that point is reinforced for taking bolts. You are planing to put bolts and suspend weight in parts of the boat that are not designed for it. Yes it can be done with suitable reinforcing (floors), but why? Use the whole ballast allowance for batteries and payload, and glass on a pair of bilgeboards or a skeg.
When trailering the boat will sit exactly on the original reinforced part anyway, it's the lowest part of the hull. If you are so concerned you can even fit a pad in the form of the old keelshape to the trailer. The fiberglass does not care what's underneath, cast iron, wood, rock, etc.

 

[Jeff in Boston]

I was planning on bolting *only* to the original keel reinforcement pad/recess. It is about 86" long. The original keel was about 100" long, swept back. I can't see how going to a 120" or 140" long keel that weighs less than the original would be a problem.

See: Keel and Keel Bolt Photos - Pearson 26 (pfeiffer.net) for details.

That said if I can fit enough ballast low enough your idea of skipping the outboard keel does have merit. I could bolt on a large skeg using the existing rudder hole.

 

[gonzo]

I could bolt on a large skeg using the existing rudder hole.

Where is the rudder going?

 

[Jeff in Boston]

I plan to use the motor tiller instead of rudder.

 

[Jeff in Boston]

I plan to use the motor tiller instead of rudder for a few reasons:

1) To sell the existing rudder / tiller which is worth more than the boat separately.

2) The existing rudder is way too long /deep after the keel is removed.

3) I want the space in the cockpit as the existing tiller is really long.

4) I will have a motor tiller anyways.

5) I figure (might be wrong!) that the steering authority will be higher on the motor than on a separate rudder.

 

[Rumars]

Well, you do waht you must. If you use plain steel bolts, paint them with epoxy primer and paint before installing.

 

[gonzo]

1) To sell the existing rudder / tiller which is worth more than the boat separately.

There isn't really a market for an old rudder.

 

[Jeff in Boston]

The rudder I have is a new aftermarket replacement from d & r. I'm not worried about being able to sell it.

 

[Trevor Richard Hunt]

Use Monel and be done with it forever. I have about 35 years experience of bolting big pieces of steel with Monel. As long as you keep up the coating on the steel, especially at any weld heat effected zone, it is definitely longer than your life, and most likely for several hundred years. Use Monel for the bolts (unless you want higher strength then use K-Monel) and use a blue moly grease (Bostik or Never-Seez).

Correct, but do you know where I can find cheap Monel ??

I'm rebuilding a 27ft alloy lifeboat, (Hull up project), and I'm just starting to look for parts that will pass a very detailed commercial survey done by an RNLI inspector.

I was looking for Monel plates, but will need a set of machine screws to mount Monel plates along the forward bow section near the waterline to comply with ice worthiness regulations. They will be mounted on the outside of a composite alloy hull, (4 layers of West system real epoxy and alternating fine woven and chopped strand cloth), and the USCG use Monel plating on their old CG 36500 offshore boats, and my design is based on a modified version of that great full displacement self righting boat.
Also just read that plastic seacocks are a no go unless fire proof, so will also be looking for alloy seacocks, although I think I can use stainless steel for the thru hulls that are below waterline.

 

[Rob Lehmann]

Getting back to the original question in the thread: It's pretty damn important to use the right kind of material for your keel bolts!!! Galvanic corrosion will happen if you don't get it right, and since the bolts will be buried deep in your keel you won't even see it happening. The last thing you want is to lose a keel!

People are suggesting Monel in your steel keel but I would argue against it. Vehemently. Why? The science argues against it. Simple as that. Monel is indeed a highly corrosion resistant material, but when it's touching steel you're going to have a problem. Read up on galvanic corrosion and look at this galvanic series chart for why. No doubt someone will say to you that they've had monel screwed in to steel for years and it looks just fine, and it MIGHT under certain conditions, but your keel's attachment is not something to play with and is not a good place to start ignoring the science.

If your keel is steel then you really should be using galvanized keel bolts, or (gasp) stainless bolts. I personally don't like the idea of stainless bolts due to crevice corrosion, but thousands of production boats have them and they will last for quite some time. More info about crevice corrosion here if you're interested, just scroll down a bit as that article is mostly about screws but does address crevice corrosion in stainless.

In short? Skip buying the ultra expensive monel and go with a galvanized or stainless keel bolt, it's the right thing to use AND it's cheaper.