Boat ramp 2

[scottiesei]

I am looking for some info regarding concrete boat ramps and how the erosion at the bottom is handled. One of my friend's HOA is considering putting one in and was asking questions about how to treat the edge and how far in the water it should go. I would assume a gravel base near the end a few feet past the edge of the concrete would help. Anyone have any experience with this?

 

[WMO]

Try google.

http://www.usace.army.mil/publications/eng-manuals/em1110-2-410/c-4.pdf

 

[concretemasonry]

Every one is different, but the basic engineering priciples still apply. - Assuming a normal range of trailered boats (15 - 21' and 15 to 125 hp.)

The major factor is the slope of the ramp and the depth of the water beyond the end of the ramp.

The second is the "bottom" beyond the end of the ramp.

Ramps with shallow ramps mean more prop wash on and off the trailer and more scour. This means more coarse materisl that will not wash out.

Short ramps that require the trailer wheels off the ramp should be avoided at all costs because of the abuse to the ramp and the bottom beyond the ramp. In this case you really need some rock for stability. - There is always someone that will try to go in too far.

If you have a "soft" bottom beyong the ramp there will be a lot of errosion from the bigger boats, dur to the volume of water moved and the prop depth.

I wish there was an ASTM, ACI, DNR piece of boilerplate, but it just boils down to looking and applying engineering priciples. Remember - gravel looks good and very stable out of the water, but once you look at the real weight and size, rock looks much better. Bigger is better unless you hit it with a prop.

Dick