Concrete launch ramp texture question

[Jonny]

Dear All,

we have a concrete boat launching ramp that runs from the boathouse and out into the sea (yes, the sea).

The lower part is quite flat and is very prone to algal growth at certain times of the year and certain tides. This makes it diabolically slippery and dangerous.

We power-wash it as often as we can, but can't always do it daily (or twice daily at times!). We have stopped using chemicals to assist with the cleaning (some work really well - but not so good for the fish).

The club is planning to do some repair and rectification works, but we don't know what texture or pattern would be best.

So I have come to the great rowing brains trust...

What, in your experience, has worked best?
- a simple rough texture
- a straight horizontal ridge every 2-3 inches (5-7cm), cast with concrete pour
- a straight horizontal cut line (like a machine cut groove), cut post curing
- a herringbone pattern in either a ridge or cut
- anything else?

Any and all wisdom greatly appreciated!

[James HS]

A subject dear to my heart as we recently built a new ramp and made it beautifully pre cast and craned into site - only to discover that the surface was too good for tideway sludge.

We partially resolved this by having grooving installed - using something called "flail grooving" (normally used in horse boxes.)

This works for all but the most sludgy if tidal deposits - when we have to sweep and wash down (water only).

Were I doing this again I think I would have had a pattern of chevrons built into the mould as then the tide would have done some of the work to wash the silt off. However, I don't think any of it would be maintenance free.


I walked most of the ramps in our part of the tideway and pas particularly unimpressed by tamped finishes, which I had thought would be really good but the pebble aggregate makes up a fair proportion of the surface and is actually quite slippery.

So the simple rough texture for me is a no no.

IMHO a deep chevron pattern and a crosscut flail would give enough grip for most footwear.

We were not allowed to use any additives while we were constructing, but I also think that some kind of surface seal to make cleaning off the algae would help!

I wanted to use something like carbo grip - but again it is not marine friendly!

Can yo put down a test section as a part of the pre-works.



James

[Jonny]

James, we might not have much time to test anything in great depth. Bit of a problem. Time pressures to ensure our works are done the same time as another project.

[sully]

On Thursday, October 24, 2013 10:18:25 PM UTC-7, Jonny wrote:
> James, we might not have much time to test anything in great depth. Bit of a problem. Time pressures to ensure our works are done the same time as another project.

Just for more opinions, but I don't feel strongly about it, don't know enough.
I've launched for years off launch ramps at the lake and nearby bodys of water, carrying a boat down concrete ramps rather than launchable docks.

They all have in common a roughly grooved surface, roughly parallel to the direction of the ramp, broken up by flat spots. By "roughly parallel" means they all go lengthwise, but at slight angles, thus water flows down, and the edged surface of them stays clean by the contact with the tires of launching vehicles.

Walking down barefoot, the foot is somewhat tender, but unless I get to a desperately low part of the year of the lake, there's little slippage.

There's no effort by the county or state to clean these grooves. I would think a stiff bristled broom every once in a while would make a big difference if I used it every day.

[Carl]

Sedimentation is a fact of life, with most flowing waters somewhat
turbid. As water flows (even if just up & down rather than across) over
your ramp, small circulation whorls and vortices centrifuge a little of
the suspended matter onto the ramp, where it is adheres to the surface,
even if dead smooth, &/or settles into its texture if rough. Then
biology takes a hand, coating the sediment with slime & maybe keying it
all to the underlying surface.

If there's larger aggregate in the concrete, chances are it's got
rounded stones which, with the sediment & slime, can be very slippery.
Some rubber soles, or bare feet, may cope with this if they conform well
to the surface but many won't.

I suspect that crampons would be unacceptable extras in your rowing kit,
but they might give you a grip ;) . Maybe a rubber sole with a very
textured surface (e.g. like Lego bricks) might engage despite the slime.

It seems what's needed is a surface covered with sharp upstands of grit,
like the stuff that's bonded to road surfaces to give high friction at
some busy intersections. These might penetrate the surface deposits,
but only where these have not built up a sufficient cushion. And a
problem there might be that the phenolic-smelling bonding agent that's
generally used may be thought unkind to aquatic life.

Short of seal-launching from the top of the ramp, which I offer only
frivolously, Id agree that a daily scrub with a stiff-bristled broom &
water is the best answer. Which means a ramp-cleaning rota and a
membership all of whom understand that it's part of what they must all
do as part of going rowing. Or is that a rather old-fashioned concept
these days?

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
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[Jonny]

On Friday, October 25, 2013 7:37:51 PM UTC+8, Carl wrote:

> Or is that a rather old-fashioned concept these days?
>

Yes, Carl...in this part of the world that is a very outdated way of thinking. Why do something yourself when you can get the 'staff' to do it all for you?