Dutch couple found dead, their sailboat found upturned

[robert sailor]

Do glass boats flex when the keel is hit absorbing some of the shearing load on the bolts? Does the additional stiffness in metal add to the load on the bolts?

[captlloyd]

Originally Posted by robert sailor

Do glass boats flex when the keel is hit absorbing some of the shearing load on the bolts? Does the additional stiffness in metal add to the load on the bolts?

Yes and Yes. Fiberglass flexes much more than steel. Steel does flex slightly. Bottom line, when any material or combination of materials reaches a certain stress point, something has to go. Sometimes structures have fail points engineered into them to prevent failure to the overall structure. For example, the lower unit on an outboard motor, it has a shear-pin that fails before damage is done to the whole lower unit.

[unclemack]

Originally Posted by robert sailor

Do glass boats flex when the keel is hit absorbing some of the shearing load on the bolts? Does the additional stiffness in metal add to the load on the bolts?

+1

I was about to post that it seemed to me very likely that hull stiffness would make keel bolts extremely vulnerable on a steel boat.

J-bolts presumably wouldn't be needed though so no reason not to use bolts capable of removal one at a time for inspection.
Bit puzzled as to why that apparently wasn't done.
Also why more and larger bolts wouldn't have been used by design to make a non-issue of it.

[Polux]

The keel bolts on a steel hull will be subjected to a huge "cutting effect" when the heavy boat grounds hard. Much less or almost none on a GRP boat where the material to what the bolts are bolted is softer than steel.

Steel against steel with a big cutting force applied on groundings by a relatively thin steel plaque to a bolt at 90º seems really a bad idea unless some absorbing system is used to prevent direct impact.

Bolted keels on a steel boat seems more and more a bad idea unless the bolts are much bigger than on GRP boat and probably they are not calculated regarding this grounding cutting effect but regarding the stress the boat will be subjected on normal use.

[Brob2]

Originally Posted by captlloyd

Yes and Yes. Fiberglass flexes much more than steel. Steel does flex slightly. Bottom line, when any material or combination of materials reaches a certain stress point, something has to go. Sometimes structures have fail points engineered into them to prevent failure to the overall structure. For example, the lower unit on an outboard motor, it has a shear-pin that fails before damage is done to the whole lower unit.

I like it. Draw it up and patent that puppy. CaptLloyds snap-on keel extensions.

[boatman61]

I have not seen my boat dried out yet though it seems I have external 'Doublers to the front of my keel.. can I assume its a welded keel..??

Ignorance about steel showing.. lol

[DumnMad]

Originally Posted by robert sailor

Do glass boats flex when the keel is hit absorbing some of the shearing load on the bolts? Does the additional stiffness in metal add to the load on the bolts?

Exactly, fatigue failure is caused by cyclic loading and ocurrs faster at higher stresses.
Overload the bolts a few times from grounding reduces the fatigue life by leaving residual stress in the steel, then cyclic loading from wave action can finish it off.

[unclemack]

Originally Posted by boatman61

I have not seen my boat dried out yet though it seems I have external 'Doublers to the front of my keel.. can I assume its a welded keel..??

Ignorance about steel showing.. lol

Hi Boaty, a doubler used as part of a keel-to-hull attachment scheme wouldn't make much sense really.

More usually used as an economical way to repair rusted or damaged areas.
Front of keel might suggest a minor traffic accident. Maybe a PO nudged the kerb a bit?

Adds character if anything

If the welding is carried out competently there should be nothing to worry about for years.

Keep an eye on it, sound with a hammer once in a while at haul outs. Checking for any "ripple effect" damage wouldn't hurt first time she's out.

There's an old Clyde Puffer still in steam and sailing that was saved by doubling around the whole waterline many years ago.

[hpeer]

While no expert in all the metal boats I've looked at, and all I've read about in Metal Boat Quarterly, and all I've seen on Yachtworld,Apollo Duck, and elsewhere this is the FIRST time I have heard of a bolt on keel on a metal boat. My guess is it is in 1% of the boats that have this feature. Could be wrong, it's my best guess.

[boatman61]

Originally Posted by unclemack

Hi Boaty, a doubler used as part of a keel-to-hull attachment scheme wouldn't make much sense really.

More usually used as an economical way to repair rusted or damaged areas.
Front of keel might suggest a minor traffic accident. Maybe a PO nudged the kerb a bit?

Adds character if anything

If the welding is carried out competently there should be nothing to worry about for years.

Keep an eye on it, sound with a hammer once in a while at haul outs. Checking for any "ripple effect" damage wouldn't hurt first time she's out.

There's an old Clyde Puffer still in steam and sailing that was saved by doubling around the whole waterline many years ago.

Thanks for that.. kinda suspicioned that as it is suggested the Stbd doubler be replaced.. or the doublers removing and fresh plated.. only look to be 2" x 18" strips.. in the survey pic

[clockwork orange]

In a grounding, most of the load is on the forward pairs of bolts and is tensile loading but can certainly become shear as you try to extricate yourself. Shear strength is only about 60% of tensile. Most keel bolt will be type 316 SS. Stainless steel alloys are subject to crevice corrosion which is not usually an issue but can become one if groundings cause the bedding compound to let go causing seawater to get at the bolts and left unrepaired, this is not an uncommon scenario when the grounding is minor, you dive down and don't find anything "serious" so opt to leave it until next haulout. You will see many examples of this any time you walk around a storage yard, there are some brands that are famous for the crack at the joint at the front of the keel, ie, the C&C smile. In a hard grounding we often see the fwd edge opened up and the aft edge driven up into the bottom.

[Lizzy Belle]

Originally Posted by hpeer

this is the FIRST time I have heard of a bolt on keel on a metal boat.

Neither had I, to be honest. I'm not a big fan of steel myself, for my use of a boat, so I'm far more familiar with plastic boats. I just kind of assumed steel boats don't have a bolted on keel ...

Guess it really is time to add "Never mind me, I'm usually wrong and assume too much" to my sig

[estarzinger]

^^ as I mentioned way above . . . . The reason for the bolt on here is the combination of the hard dodger and deep keel make the boat too high to truck (under highway bridges). Not many cruising boats are that "tall". That is a limitation that may or may not be important - but I guess the designers say that the bolt on is perfectly safe and gives you the trucking option.

The bolt on also gives you the option of switching keels - as in a deep one for round the world and then a shallower one for home waters after cruising retirement (Dutch waters can be shallow). But I think this is a less common reason than the trucking rational.

[clockwork orange]

It is surprising to me as a boatbuilder that the designer or builder would opt to make the keel removable rather than the hard dodger removable for over the road transportation, especially on a metal boat where a welded keel joint is clearly so much better.

Steve.

[estarzinger]

^^ well the keel removes +2m of height, while the dodger under 1m (there is a well in the cockpit which allows the dodger to be quite low profile) . . . Don't know that is the rational but it might well be. I don't know Europe highway bridge clearances.

The designers here had an already designed bolt on keel because this boat is also offered as a glass strip planked cored model.