Would your keel joint survive a full speed impact?

[hellosailor]

"until things start to blow "
Yes, the I28 gets outright talkative at 40 knots, you can hear each piece of the boat as it hands off the load from every surge down through the mast to the keel. Kinda like a big dog walking through a pond, shaking it all off and saying "What?" when you complain about the splatter.
Who wants to sail in under five knots anyway? (VBG)

[Minnewaska]

Originally Posted by msmith10

I know the boat. She didn't hit sand-- she hit rocks under power at considerable speed. Impact was enough to tear the engine and generator off their mounts. Yes, it was repaired, at over $200k in costs, but it's not a boat I'd buy.
Correction: It may not be the same boat. There is a Yachtworld listing that is not the boat I'm referring to.
Same story, though.

I am told it is one of the boats out on yachtworld. Ive never seen it, but was told the story by a surveyor that I used on mine.

I cant imagine the damage if we rammed our keel into rocks at full throttle. 40,000+ lbs at 8 to 9 kts and a dead stop in inches. Says something that it reportedly stayed afloat. It had to have been towed in, but I don't know.

[SloopJonB]

Originally Posted by Faster

One of the largest factors will be keel material. Lead absorbs an amazing amount of energy as it deforms under impact. Iron keels do not and transfer the full forces to the hull - therefore internal damage is likely to be more significant with iron keels.

The designer Bill Garden said the opposite in one of his yacht design books. His opinion was that lead would crush and "form" around the obstruction and as a result, the boat would absorb the full energy of the impact. Iron, on the other hand would tend to bounce off the obstruction and not absorb the same amount of energy. He preferred iron on boats that would sometimes have to "feel" their way into anchorages.

I have seen or experienced both and I tend to agree with Garden. I hit a rock at full speed with a lead fin keel - the boat stopped dead, crew were thrown off their feet, minor injuries etc. The boat survived intact but I had an 8" square area of the toe of the keel to fill and fair on the next haulout.

On the other hand, I was looking out over English Bay one evening from a bluff in Kitsilano, watching a 33'ish wooden motorsailor motoring by fairly near shore. All of a sudden there was a very audible CLANG and the boat jumped about a foot. The skipper merely turned a few degrees offshore and just kept on truckin' - completely unruffled - no crew flying about, no drama, just an almighty CLANG, clearly audible from at least 300 yards.

I saw that long before I read Garden's book and immediately thought of it when I did - his words completely agreed with what I witnessed (and later experienced).

Also, when I was redoing the iron keel on my current boat, on the toe of the keel there were a number of 1/4" deep gouges in the toe area - the boat had been through El Caribe from New York to L.A. and had apparently hit some coral or something - 1/4" deep gouges in SOLID IRON - how much force did that take? It left a lot less damage than the lead incurred on my old boat.

As to the OP's question, I am confident my iron keel can withstand a hard hit. It has a 1' wide, 10' long flange along the top with a double row of studs spaced 10" apart laterally. For those familiar with the Thunderbird, it is not unlike how their keels are mounted. The whole thing fits up into a 1 1/2" deep rabbet moulded into the hull. The bottom above it at that point is 2" thick. On the inside, each pair of studs passes through a piece of 2" X 4" X 24" stainless channel with thick fender washers and double nuts on each stud. There are also 8" timber "floors" glassed into the bottom between every other stainless channel.

I think it can take a hit.

[Maine Sail]

Originally Posted by hellosailor

down, the I28 is built like a brick *house, it isn't easy to break one. But AFAIK there is no keel designed to take hard impacts without structurl damage to the boat. Either you tear the keel off, or the hull lets go, the amount of force involved in a "head on" collision is going to wrinkle the boat. Even if you kept the keel on, the rig would probably be damaged and the bulkheads come untabbed--on any boat.

Coming from Maine the land of GRANITE ledges we see LOTS of boats hit rocks each year. If I had to guess I'd say in the 150 -250 hard groundings per year. I know of ONE keel the fell off over the last 20 years. It was a J Boat. In one week two years ago I watched 8 boats get hauled at the same yard for "ledge damage inspection".. I'm always perplexed how so many folks find these ledges but they do..

The worst and longest repairs I see are encapsulated keels or fins on quite lightly built boats because there can be structural damage. I once watched an Island Packet drain water from the keel encapsulation (cement) for over 7 weeks and it was still far from dry when the out of state owners hauled it away on a truck. During the time the IP was drying two or three fin keelers were hauled ground, filled, faired and re-launched..

I would have to say the a large percentage of groundings in Maine result in not much more than some dents and dings in the lead.

I had two of my customers hit ledges this summer alone and both were at full tilt and one with an SOG of about 7.2 - 7.3 knots. He hit solid granite and people aboard were bruised. The keels were mashed and the keel hull joints will be ground & faired, the lead dents fixed and they will be fine for many more years. Structural damage is non-existent on either of these boats one is an 82 Sabre 34 MKI and the other an 87 Ericson 32. Both of these boats were deep fins not shoal..

Many fin keel boats hit granite here in Maine with no structural damage and only lead dents and perhaps some cracking of the keel hull fairing putty. While some do have structural damage sinkings and keels ripping off are very rare.

These folks found the ledge and had to wait out the tide..

[Barquito]

This has been an eye opening thread for me. I really don't like the idea of looking and wondering if keelbolts are rusting, and moderatly don't like the idea of replacing keel boats. Therefore, I went with an encapsulated keel design. However, I can now see the argument for bolt-on keels. What about adding a really thick 'skid plate' to the nose of an encapsulated keel?

Also, it is obvious that bigger boats are stonger, but, it seems the force of a full speed hit in a large boat would be orders of magnitude larger than in a small boat. The keel lever arm is longer, the weight of the boat is larger, and the top speed of the boat is greater. Are deep draft, heavy, big-boats built THAT strong?

[hellosailor]

A skid plate only works by deflecting what it is attached to. You'd have to run it from the bow to the bottom of the keel, so you could skid up over whatever you hit. And it would have to be built and attached strong enough to allow that shift up and over. That would be a lot of weight, and you'd probably still trash the rig and bulkhead tabbing when you hit.

Easier to just stay in clear water.

[tommays]

On my friends Tartan 372 when they hit the Ledge in Maine the biggest issue was breaking all four Volvo motor mounts as the motor is under the kitchen sink its a bit of chore

[goboatingnow]

have a look at

Crash Test - Dehler 31 yacht - YouTube

[DelmarRey]

Now I need a T-shirt that says "I survived a hard grounding".

[downeast450]

Maine,

I am amazed at that number of hard groundings / year. I spend much of the sailing season along the Maine coast and have many friends who sail here. I only know of two hard hits around MDI in the past few years. I guess I don't know as many sailors as I thought. My sailing friends are "locals". Is the carnage you mention happening to boats from "away"? There are not that many "hidden" spots if the skipper is competent.

Down