Do not use hollow concrete blocks

[330DA]

Use of hollow concrete blocks (HCB) during winter lay up has been discussed in a number of threads each fall. Here is a picture of a cracked block under a 370 Sundancer. This is not my boat, but a slip neighbor's a few years back. The blocks under the keel support the boat. The stands keep it from tipping, as many have written in other posts.

HCB can fail without warning in this type of situation.

 

[88 AmberRay]

I don't think it was the fault of the hollow concrete block.
I have been using the same blocks for the past 15 years with no problems.
The picture shows the blocks on the ground with no footings. If the soil under the left block setteled a bit that could cause the block to crack!

 

[Sun Chaser]

I'm in agreement with AmberRay. We have been using cinder blocks at our club for the last 15-20 years without a problem. We use wood on top of the cinder blocks so the boat does not come in contact with the hull.

Glenn

 

[HavnFunYet?]

i would hope that the boat is always in contact with the hull!!

 

[wish2fish]

probably wouldn't have cracked if they had put some wood over the block to distribute the weight off off a single point.

amberray,
how does your boat get up on the deck?

 

[SCORPIO]

Are solid wood blocks that hard to come by? I've only ever used solid wood keel blocks and so does my yard. Pressure treated wood will last a long time. I'd be afraid of concrete blocks either shattering or damaging the hull.
JMHO

 

[rondds]

My last marina used wood blocks. Not PT. Just big old hunks of wood. Not sure where you can get those nowadays. Our new place uses concrete blocks but they lay wood at the contact points along the keel. Both marinas use boat stands laterally under the chines and aft. I would prefer wood b/c of it's elasticity - concrete has no ability to flex.

 

[rabyers1]

Concrete blocks and cinder blocks are not the same thing. Concrete blocks are significantly heavier, denser and rated to carry much more weight than cinder blocks, with far greater form strength. Concrete blocks would be a much better choice for blocking large boat hulls than cinder blocks, which are much more prone to crack under when weight is concentrated on a small surface section of the block.

 

[JVM225]

I don't think it was the fault of the hollow concrete block.
I have been using the same blocks for the past 15 years with no problems.
The picture shows the blocks on the ground with no footings. If the soil under the left block setteled a bit that could cause the block to crack!

I agree! They build buildings with the things.
The block probably cracked because it was used improperly.

 

[Carver370]

I think the first problem might be is that boat looks like its stored at Service 1.

 

[tobnpr]

I agree! They build buildings with the things.
The block probably cracked because it was used improperly.

No comparison can be made between these two applications. The loads placed on the blocks are apples and oranges- and in any case, whenever there are substantial loads placed on concrete blocks in a building application (like lintel bearing on either side of an opening) the cells of the blocks are poured solid with concrete, and reinforced with wire and rebar.

Blocks are not supposed to be used for cribbing- they're not designed for the loads, especially of larger boats. I've never seen a "real" boatyard use anything but wood cribbing uder the keel, and I imagine their insurance carrier would have a problem with it if they did...

 

[fwebster]

I continue to be amazed at the short cuts northern boat yards use for storage. It is a wonder we don't see annual posts about boat damage due to concrete or cinder blocks, not enough blocks, inadequate number of jack stands, boats falling over, etc.

Here are a couple of photos from a Sea Ray dealer and how a boat should be blocked for service:

 

[Woody]

Like all un-reinforced concrete, a blocks strength is in compression. The OP’s boat could be balanced on one 8” hollow concrete block if the block was on a proper base, meaning it has to be supported uniformly, with the total load also spread uniformly on the top surface of the block. This certainly would not be good for the boat but the block could do it.
Having said that a concrete block is to easy to misuse in a boat blocking application. They also get thrown around and abused(nicked and chipped) when not under a boat. Not a good thing for the block. I would suggest not using concrete blocks for supporting a boat. One of the problems with boat cribbing is storage during the off season. Concrete blocks can be stacked up neatly for example taking up less space than boat cradles. I can see why some yards use them. If I stored in a boat yard that used concrete blocks I would furnish them with proper wood blocking and insist that they use it on my boat.

 

[rondds]

If I stored in a boat yard that used concrete blocks I would furnish them with proper wood blocking and insist that they use it on my boat.

Fine. Which brings up the question someone asked before. Where can you got wood blocks that size.

I'm guessing that here in the north there are a lot more boats blocked at a given time (ie: winter) than in the south, where a boat is blocked for a week + at a time. Not justifying cutting corners, but it's easy to see why they use concrete up here. I'd consider wood if I knew where to get it. Also, not sure about "legal responsibility" of the yard if something happens to my boat which was blocked on my wood. Sounds like an escape clause for the yard.

How about a bean bag? Think that'd work??

 

[tobnpr]

Fine. Which brings up the question someone asked before. Where can you got wood blocks that size.
[/IMG]

Ron;

Really shouldn't be all that difficult. You're not going to find it at your local HD or Lowes, but any lumber yard should be able to special order it for you. Looks like 12" x 12"? The stuff is not common, but is used in post and beam construction and is available.

If you want, and can't locate any, feel free to pm me with what you're looking for and I'll check with my lumber suppliers.

 

[rondds]

Thanks. I could check at 84 lumber. They are definitely more hard-core than the home centers. Do you just cut it with a chain saw?

 

[Woody]

Fine. Which brings up the question someone asked before. Where can you got wood blocks that size.

I'm guessing that here in the north there are a lot more boats blocked at a given time (ie: winter) than in the south, where a boat is blocked for a week + at a time. Not justifying cutting corners, but it's easy to see why they use concrete up here. I'd consider wood if I knew where to get it. Also, not sure about "legal responsibility" of the yard if something happens to my boat which was blocked on my wood. Sounds like an escape clause for the yard.

How about a bean bag? Think that'd work??

Frank W posted pics of what you should end up with. Nothing says the blocking has has to be that size. Most lumber yards will have 4" and 6" square treated posts. There is nothing wrong with you using 4 rows of 6" blocking while your neighbor uses 2 rows of 12". I would think that the closest lumber yard to you could fix you up with the basic materials to do the job.

 

[330DA]

Wow, I had no idea that this thread would take the shape it has. Boat US's Seaworthy magazine a few years ago had an article about blocking in a winterization special. It recommended wood.

 

[Carver370]

I was thinking exactly the same thing. By the way that lOoks, it has a certain person's handiwork written all over it. But I could be mistaken.......

Sure does!

 

[88 AmberRay]

probably wouldn't have cracked if they had put some wood over the block to distribute the weight off off a single point.

amberray,
how does your boat get up on the deck?

Wish2fish,
A barge with a crane comes down the canal in the fall to lift me out and returns in the spring to put me in. Each haul is
$220.00. Alot less expensive than keeping it a the marina!