concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

[superduperest]

Hi, ive been given permission by our harbour master to dig a mooring in our local estuary and was wanding if a concrete filled tyre would be heavy enough to hold a shetland 535 on a mooring dug into sand and mud?

The boat+engine+stuff weighs about 600kgs I think and its location is pretty sheltered and is only for the warmer months

And as for the set up, is it just a concrete filled tyre with a bent metal bar through it leading to some chain and off to a swivel and then some mooring rope with a clip at the end with the pick up buoy?

And how deep does the tyre need to be sunk?

Any advice would be appreciated

Thanks, Chris

 

[pevaguy]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

It would probably help to know a bit more information. Are you talking about a wheelbarrow tire or an earth-mover tire? It would make a difference.

 

[superduperest]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Hi and sorry for being a little vague, I was thinking of using a normal sized car tyre as the boat is only 18ft. Do you think that would be heavy enough to resist the pull of the tide?I could always upgeade to a tractor tyre

Thanks for your time

Chris

 

[ddefendi]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Here's another idea. Use an empty 5Gal paint bucket full of cement/concrete. If one's not enough, add another and another till it holds...

 

[Chris1956]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

I do not think that is be a good plan. Weight is not what you want, and that is not nearly heavy enough. Also the tire will slide acrodd the botton with little effort. You want something to dig into the bottom and provide a solid hold. A lot of moorings use mushroom anchors. The dig them selves in real deep due the the action of the waves. I would recommend you see what everyone else uses.

 

[rallyart]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Some rebar sticking out will help it to resist movement

 

[Fireman431]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Most boat moorings are not based on weight (think of how light an anchor is). They are based on whatever is holding the boat to be buried in the sand. Most moorings are actually placed in the river/lake bed and not just dropped overboard. When a concrete mooring is placed, the diver goes to the bottom and uses a water jet to bury the item (say a concrete block 4'x4'x4'). The sand is blasted away from under the mooring until it is sufficiently buried to eliminate dragging.

If you want to try a different approach, use an emptied out V-8 engine block and drop it over. Wait 3-6 months and the local currents will bury it for you, but it's always a good idea to dive it and verify before mooring to it.

 

[UncleWillie]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Depending on your bottom, the Tire will slowly bury itself, but not if you keep pulling it up!
Drop it and leave it alone until it is buried.
Think anchor, It needs to be ANCHORED, not weighted.

You stated you are going to bury it.
Depending on the bottom material ....
One tire diameter, ~1 meter down might be enough.
Ask what everyone else has done, and what worked!

The concrete is not going to weigh a whole lot under water.
If the rubber in the tire doesn't float, it is close to floating. Think, zero weight for the tire itself.
The water in the concrete weights nothing underwater.
And the 50Kg lbs of dry concrete will weigh 50Kg minus the amount of water it displaces.
Your 50Kg tire might weigh only 25Kg on the bottom.

On the plus side, it is a dirt cheap 50Kg, 1 meter Mushroom anchor!
Make one with 3 meters of chain cemented into the middle.
Make another 2 or 3 with a piece of 100 cm PVC in the middle.
Pile them up like a stack of donuts with the chain through the holes.
Four 50Kg tires will be a lot more managable than one 200Kg Barrel.

How deep is the bottom'? Sand, Mud ???
What kind of seas would you see in a 100 year storm?

 

[roscoe]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Steel frame work or small engine block would be a lot better.

More dense, less water displaced, more likely to settle and dig in.

 

[Ned L]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

I'm thinking that the original poster was making reference to burying the tire, and even asked how deep it needs to be sunk. If you can get it 1/2 -1 M down in the bottom it will not be moving and will work fine. It would be best to fasten the chain so that it comes up through the center hole of the tire and not from around the outside.

 

[jeeperman]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

When you were "given permission by our harbour master", were there not specific guidelines to let you know what he/they will allow?

I would be surprised if they still allow whatever junk people have laying around to be used to clutter up the bottom of the harbor.

 

[cymru]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

The standard model used in our estuary is a homemade square molded concrete block shaped like a truncated pyramid roughly 3ft side. The idea is the tidal flow makes it dig in.

 

[Willyclay]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

If you want to try a different approach, use an emptied out V-8 engine block and drop it over. Wait 3-6 months and the local currents will bury it for you, but it's always a good idea to dive it and verify before mooring to it.

I helped a bud with the engine block approach for his 27ft Catalina sailboat. It worked well in our area's six foot average tide range, strong currents and occasional tropical storms. He moved the boat up the river for full-blown hurricanes. Good luck!

 

[Part-time]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

I used 2 pick up truck tires (245/75/16) filled with concrete to hold the end of my dock in place in the river, with 3 boats moored to it.
And trust me, concrete does not get any lighter under water and that flat side of your weight will suck itself right into the bottom.
Just make sure your chain is in the center of the tire and you will be fine.
I would try to find an off road tire apx 35"x14" and you'll be set.

 

[UncleWillie]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

... concrete does not get any lighter under water and that flat side of your weight will suck itself right into the bottom.

I agree that the real holding power of the anchorage is the attachment of the object to the bottom, and not the brute force of gravity.

Concrete does indeed get considerably lighter under water.
It takes about 100 lbs of dry mix to form a 140 lb, 1 cubic foot block of cured concrete.
1 cubic foot will displace about 62 lbs of water.
The 140 lb block of concrete will "Weigh" about 78 lbs under water. A 44% lose of weight!

CYMRU's concrete pyramid weighed about 3500 lbs on shore, and about 1950 on the bottom.
It is still plenty heavy, but Archimedes is not a man to be ignored.

 

[Frank Acampora]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

Hey unk! It is nice to see someone who really understands why their boat floats. Right on with the concrete.

 

[superduperest]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

OK, thanks for the advice. I will seek out the biggest tyre I can find and follow your advice. Our tides have a range of about 6ft and as I am in the South West of England (Devon), big block V8 engines and (especially) tropical storms are few and far between.
I intend to get there at low tide with a few friends and shovels and drop it as deep as possible

Thanks for everybodys input, much appreciated

Chris

 

[Scott Danforth]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

what is the bottom structure? in sand, we make mooring anchors out of a 6" x 12" x 12" chunk of scrap iron with a few pieces of angle iron welded to it. It held my boat in strong winds, however we do not have tides to contend with here.

Another option, check with your local concrete place. around here, they use their left over concrete and make stackable forms for weights and barriers. they are about 4' x 2' x 1.5' and only cost about $25

 

[smokeonthewater]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

I was just thinking that a person could ditch the tire portion and just use the crete.... pretty easy to make a form on the ground with plywood and stakes

 

[BonairII]

Re: concrete filled tyre heavy enough to hold a shetland 535 on a mooring?

I was just thinking that a person could ditch the tire portion and just use the crete.... pretty easy to make a form on the ground with plywood and stakes

I agree. The Op can make an anchor is any shape/thickness/weight he wants by making his own form out of scrap plywood.

If he makes the bottom of the form out of plastic sheeting(or something soft), he can push rebar thru the bottom of the concrete and into the ground. Once the crete is set, he'll have an anchor with spikes in the bottom to grab the bottom of the river.