cinder blocks

[Chris1956]

Re: cinder blocks

Gee, I do not know what boatyards you guys visit. Here on the Jersey Shore, cement blocks are the blocks of choice for boats stored on land. They are immensely strong when laid webbing up, and much cheaper and more weather-resistant than any wood. If you double block the boat, as I described, it will be real stable.

 

[Bayou Dave]

Re: cinder blocks

Looks like I opened up a can of worms. lol..... After reading all the opinions the first thing I will do is see how high I need to go. Weather is not permitting that today. Block keel first and then under the chines. 18"-24" 4x4's or 6x6's, stacked like cribbing seems to be the better choice. Next choice is concrete blocks, if I can keep it to no more than 3 high. Stacking them 2 wide and alternating direction, with a piece of 2x8 on top and bottom. If I use concrete blocks at least I can reuse them elsewhere. Not sure where I ever would use small pieces of 4x4 or 6x6 in the future.

 

[smokeonthewater]

Re: cinder blocks

http://forums.iboats.com/boat-topic...-your-small-boat-ground-5-minutes-527592.html

 

[bruceb58]

Re: cinder blocks

Gee, I do not know what boatyards you guys visit. Here on the Jersey Shore,

Just drove by one in Marina Del Rey yesterday. Not a concrete block in sight. Lots of wood though.

 

[steelespike]

Re: cinder blocks

If you must use cinder blocks, Tie port and starboard sides together with a board to help stop sideways movement.

Just put stern blocks 45 degrees to the keel and each stack 90 degrees to each other.Amazingly ridged.

 

[MarkSee]

Re: cinder blocks

Just drove by one in Marina Del Rey yesterday. Not a concrete block in sight. Lots of wood though.

Yep, as Bruce is saying, here in SoCal those big blocks of wood is what the pros use for temporary blocking.

When the boatyard hauled my 27 Sea Ray for the pre-purchase inspection, big 'ol wood blocks at the back corners then 1 with a V cutout underneath the keel about 3/4 of the way up.

Mark

 

[Chris1956]

Re: cinder blocks

Cal probably outlawed cement blocks. Just like those fascists to do that..

 

[Scott Danforth]

Re: cinder blocks

"cinder"blocks do not have great compressive strenght. any point loading and they crush. they are porous, and not really good building material other than they are cheep.

Having watched open web concrete blocks crush under the weight of a shed, and under the weight of just the tongue jack of my trailer, I can not recommend them unless they are filled with concrete and supported with rebar.

now wood on the other hand has excellent compressive loading.

 

[sphelps]

Re: cinder blocks

Blocks of wood are great if you have them and so are concrete blocks if you use common sense setting them up . I have never seen a mobile home ever set up with wood blocks . They are not poured with concrete and rebar . Years ago most all off grade houses where built on blocks . Now mostly stem walls but they are made with blocks also . Just be smart on how ya set them up ..
Now we just have to decide which boats are easier to block up . O/B or I/O ?

 

[GA_Boater]

Re: cinder blocks

Now we just have to decide which boats are easier to block up . O/B or I/O ?

Chevy Mercruisers and Merc O/B's. of course.

 

[tpenfield]

Re: cinder blocks

Since I have got a 'big boy' boat, I have switched to wood blocks instead of cinder blocks. I get those 8' 8 x 8 landscape timbers and cut them on 16" centers . . So I get 6 blocks per 8 footer.

I did use cinder blocks padded with wood on my smaller boats . . .

 

[Chris1956]

Re: cinder blocks

Scott, Cement blocks are used for the foundations of massive multi-floor buildings. They have great compressive strength, even if hollow. If you watch a mason install blocks, they do not put Portland cement across the webs, just on the long edges of the block. They have far more strength then is needed.

If a shed or your trailer tongue is crushing blocks, there is something very wrong...

 

[tazrig]

Re: cinder blocks

As is the general consensus... if you know what you're doing, cinder blocks work. That being said if this is your first, second or third go around with them be sure to bring an extra pair of underwear as you may well need it if they let go. Been there done that :facepalm: For what you've already invested in your boat not to mention your body, limbs and fingers just use wood and don't worry about it.

 

[Bayou Dave]

Re: cinder blocks

"Looking at HD the compression strength of open concrete blocks is 1900 psi. That is pretty strong.

16 in. x 8 in. x 8 in. Concrete Block-30161345 at The Home Depot

I will only use them to stabilize the stern at the chines and use stacked 6x6's for the keel and 2 spots down the center towards the bow.

 

[jigngrub]

Re: cinder blocks

I'd use wood, but if you're going to use CMUs (concrete masonry units or "cinder blocks") I strongly suggest pouring them solid with some Sakrete first.

Hollow CMUs are only used for partition walls, foundation and bearing walls must be poured solid with grout per building codes.

 

[sphelps]

Re: cinder blocks

All bearing walls are not poured solid . They do pour some cells but not all .That depends on the structural engineer . Usually foam is pumped into the remaining cells. The top couple of rows are poured solid with rebar .
After thinking about it if I was propping up a really large boat I can agree the solid wood blocks would make me feel a bit safer crawling around underneath... :yield: :watermelon:

 

[smokeonthewater]

Re: cinder blocks

"Looking at HD the compression strength of open concrete blocks is 1900 psi. That is pretty strong.

16 in. x 8 in. x 8 in. Concrete Block-30161345 at The Home Depot

I will only use them to stabilize the stern at the chines and use stacked 6x6's for the keel and 2 spots down the center towards the bow.

Your choice on the blocks.... probably be ok but be CAREFUL... on the multiple spots down the keel... WAY overkill..... Two 6x6 blocks (or two three block pyramids) for the stern and ONE 6x6 block under the keel about where the windshield is are all you need

look at the pics in the link in my last post above.... don't over think a really easy job

 

[Ned L]

Re: cinder blocks

As has been mentioned by a couple of people, there is a BIG difference between cinder block and concrete block (both are the same size and shape). Let's be sure which is being spoken about here.

 

[Scott Danforth]

Re: cinder blocks

Scott, Cement blocks are used for the foundations of massive multi-floor buildings. They have great compressive strength, even if hollow. If you watch a mason install blocks, they do not put Portland cement across the webs, just on the long edges of the block. They have far more strength then is needed.

If a shed or your trailer tongue is crushing blocks, there is something very wrong...

as I stated. they are used because they are relatively cheap.

while they have a compressive strength of 1900 PSI per ASTM. they have very little impact resistance

minimum compressive strength of white wood found in cheap dimensional lumber is 4500psi Oak is close to 7500psi

BTW I never said it was under my shed. I used 5000 PSI concrete footings and aluminum blocks under my shed.

my trailer on the other hand had a tongue weight of 450# and with the diameter of the wheel on the jack, the resulting point loading on the 1/2" diameter area (0.2 square inches) of contact would be 2250psi (well above that of a CMU's capability of 1900psi). sure it worked for a few weeks, however a bit of rocking with me walking around in the boat and the CMU crushed

 

[Chris1956]

Re: cinder blocks

Gee, A piece of wood between the pointy steel tongue of the trailer and the block would have prevented that. Blocks are brittle. I thought everyone knew that. They crack easy with a hammer. They are also very square unlike wood and stack really safely on flat solid ground.