Damage from Running Aground

[bnort3]

I just read thru the "Modern Keel Strength" thread and was wondering about my recent experiences running aground. I've a new sailboat owner of a 2001 Beneteau 361. I bought it about six weeks ago and I've run aground 3 times. Each time I was able to "reverse" motor off. The first time was a very light grounding, but the last 2 were fairly abrupt where the bow went down due to the quick stop. The second one was in a muddy creek (Swan Creek near Rock Hall). The third one was fairly abrupt and could have been on a sandy bottom.

I have not had the keel or hull checked after these incidents but now I'm wondering if I should. I did inspect the keel bolts in the bilge and they looked fine. Any advice would be appreciated.


Thanks,

B

 

[Hermit Scott]

From an engineering standpoint there is a big difference stopping 15,000 lbs. up against a rock or digging into sand over a few feet. The impact energy is many times more when you stop the boat up against something solid that only takes .01 seconds.

 

[Don S/V ILLusion]

My advice is stop worrying (and try to stop going aground). That other thread seemed rather silly to me given there is no empirical evidence one way or the other to compare contemporary keel design to that of 30+ years ago and seemed to get progressively more silly with the addition of some anecdotal stories which are indicative of nothing except the one solitary case.

In all likelihood, if you managed to get off with little or no assistance and were not banged around while hard aground, your keel is fine evidenced by no leaking into the bilge. If there is a problem, it would be self-evident.

 

[seadaddler]

Go Swimming

You could take a look and go for a swim,it should be warm by now in Rock Hall.

 

[Ron20324]

Bnort3, that is the nice part about the Chesapeake Bay- it is a sand or a mud bottom. I know Swan Creek can be difficult to sailboats, but you DO have a chart book or chartplotter, DON'T YOU? Are you still in Lewes?

 

[Smitty]

I ran into a rock

in the Thimble Islands last August. We were motoring at about 2.5 kts, paying close attention to the chart plotter (up to date chart chip) and watching the buoys. We hit relatively hard and ran over it. Subsequent inspection revealed that we hit on the leading edge of the keel about 4" from the bottom. There was no visible damage including checking the keel bolts from the inside of the sump and we were not taking on any water. We motored back to Milford (our home port), about 8 miles, called ahead on the radio and had the boat hauled as soon as we arrived. The keel had separated from the stub by 1/4" to 1/2' at various points and all the filler that had been used to caulk the joint had broken away. The insurance company (BoatUS) advised me to get a surveyor (at their expense) to look it over and confer with the yard guys. The consensus was that it could be repaired to be stronger than original. The insurance company and the yard negotiated a price and the work was completed with the only cost to me being my deductible. The yard dropped the keel, cleaned everything thoroughly and replaced the keel using epoxy as the caulk. Then they faired the keel and joint and repainted everything (it was a brand new bottom job at the beginning of last season). Since then, we have been sailing, sometimes pretty hard, and seem to be suffering no ill effects.

My point in posting this here is that, if you hit fairly hard at any of these groundings, don't be lulled into a false sense of confidence just because there's no damage visible from above. Have her hauled and check things out very carefully. If I hadn't had her hauled right away, I'm sure she would have started taking water real quick. Further, the hull-keel joint would not have been solid or dependable.

The cost to the insurance company was ~$8,000.00. Thanks to BoatUS! They were wonderful to deal with as were the great folks at Milford Boat Works who had us back in the water and sailing within 2 weeks.

--Smitty

 

[Bad Obsession]

If you have a sailboat, you WILL run aground. No matter how nice your chart plotter is or how good your depth finger is. In the Chesapeake Bay region, the shoaling and shallow water will catch up with you at some point. It is no big deal as the bottom is rather soft and usually mud.

I have a draft of 3'10" and I have bumped bottom numerous times. What bothers me more than hitting the keel is hitting the rudder. The rudder on a wing keel is usually close to the depth of the keel and if you were to just hit the rudder it could cause an issue.

I wouldn't worry about it. A few times I have dove on the boat after I bumped bottom or ran aground and checked it only to find nothing more than an area where I knocked the barnacles off of it! LOL

 

[Dragon]

After picking up my 1988 Hunter with 4'9" draft I went agound HARD. Hit a rock and required a power boat to pull us off. A dive shows that the the leading edge of the bulb at the bottom of the keel and a soft ball size dent in it. No major leaks into the bilge. I am wondering it I should get it hauled out now or wait to the end of the season (in October)?

 

[Ross]

I have a dock neighbor with a Starwind 27?(maybe) he hit a submerged log out on the flats and the impact pulled the forward end of the keel away from the hull and pushed the aft end up. No leaks but he had broken furniture inside and some serious hull damage to have repaired.
Much of the nature of the damage will depend upon the shape of the forward edge of the keel. If it is rounded then the impact will cause the keel to ride upon and over the ledge, or log, or bump, But if the leading edge is an acute angle it may grab like a good anchor and dig right in. My long keel meets the ground at about 30 degrees and when we hit the bottom we get a lift which slows us very quickly and sticks us a little bit tighter.

 

[Bill Roosa]

Congrats

Welcome to the club of gunkholers.
FWIW Rock and Stoney creeks are aptly named. Anywhere else in the Bay it is mud or sand and unless you hit it going full speed you should be fine.
My first year at Middle river on my 5' draft Catalina we ran aground EVERY time we went out. Kinda got to be a running joke when we did not run aground till late in a trip.
Course having a depth gage that worked only in 30' or more of water did not help.

 

[bnort3]

Thanks all. I'll take a swim and check it out and I may have it hauled out to clean the bottom anyway. I'm in Lewes, DE right now and I'm not real sure they have many qualified folks to assess hull/keel damage. It is not a huge sailboat town.

 

[Don12364]

I recollect reading somewhere that the ABS had discovered that yacht hulls could be built to their standards but which were significantly too thin to withstand normal use.
I Googled it and the following item was revealed.
Yes, you are right to be concerned but probably only if your boat was built before 1994.

BTW remember that what hits the bottom is several tons of lead or cast iron - but with a relatively fragile GRP hull attached. The deceleration is not normally so bad as to transfer destructive stresses to the GRP - unless you steam straight into a rock!

Item from www.boatdesign.net
The rules are not infallible and have underestimated both the dynamic loads and the fatigue failure of hulls and fittings in the past. This has happened to vessels across the design spectrum.

Yacht keels are of particular concern since their failure is so catastrophic to life and vessel. ABS have erred in the past particularly with GRP.

The 1986 revision of the ABS OSRY does not properly account for the keel attachment shear loads. Hulls built to the minimum FOS under that rule will have inadequate hull shell thickness in way of the keel attachment. This was remedied in the 1994 edition after some catastrophic failures.

GRP boats built to this 1986 rule with a minimum FOS need their scantlings beefing up with extra laminate.

Adopting a higher FOS allows for errors in both design and construction.
__________________
Mike Johns.

 

[Ross]

Consider that a hundred pounds of added weight in the bilge will not be a detrement. Further consider that fiberglass Chopped Strand Mat weighs 2 ounces per square foot and heavy woven roving weighs 24 ounces per square yard and that a reasonable resin/glass ratio is 50:50 You could add 5 plies of CSM and 5 plies of woven roving well compacted with resin for a width of 3 feet each side of the keel and for 6 feet along its length. Overlapped at the bolts this reinforcement would add nearly 5/8 inches to the thickness of the hull at that area. We are looking at a cost of material of less than 400 dollars.

 

[Brian M H23]

Hey Ross,
Have you seen an old J-24? They actually poured some sort of concrete type of material in the bilge and drilled the keel bolt holes through. Unfortunately, the chosen material softened with prolonged exposure to moisture...most any boat made with it has had it replaced with glass...but it's a neat idea!

(It was cement with vermiculite base, to be a little more technical)