"John C." wrote in message
...
This crazy...........a three day haul in NY costs a couple of hundred
dollars. It take 30 minutes for the boat to go from floating to blocked.
Its on dry land the entire time and can be replaced in the water at any
time. Your truck can be a few steps away electric and water is often
included. Why do people always try to reinvent the wheel??

John



"Bruce in Bangkok" wrote in message
...
On Sun, 30 Mar 2008 10:34:40 +0200, "Edgar"
wrote:


"Bruce in Bangkok" wrote in message
...
On Sat, 29 Mar 2008 17:06:05 +0100, "Edgar"
wrote:


"Bruce in Bangkok" wrote in message
om...
On Sat, 29 Mar 2008 01:12:17 GMT, Jere Lull wrote:
The tide and sling rig isn't logical and I can't believe ever
existed.
If you are working on the boat at low tide just prop it up on the
beach. Heck, they been painting lobster boats that way for a couple
of
hundred years, or more. Probably been cleaning those oyster tongers
down your way using the same scheme.

There is some logical use for such a device if you plan to do some
major
work which you might not be able to finish on one low water session.


Look, if you are going to hang a boat in a sling then(1) you use a
travel lift or crane device and pick it up, or (2) you position the
slings and float the boat into them at high tide and when the tide
goes down you can work on it.

However using method (2) every high tide the boat has sufficient water
around it to float it. so why not just put it on the beach? Lash legs
in place and you have exactly the same situation - at high tide the
water covers everything up to the water line.

The slings also have the disadvantage of being rather costly. Have you
prices 15,000 lb. capacity slings recently? Better yet price 17,000
lb. slings, I want a bit of a safety factor on this project. Another
problem is what are you going to tie the slings to? Have you got a
couple of strategically located trees available? Or are you going to
build something?

Bruce-in-Bangkok
(correct email address for reply)

No, sorry,I did not make my scheme clear.
My idea was for a floating dock supported by air tanks so it could float
with a yacht in it.
Position the empty dock over the beach and flood the tanks so it sinks.
Side supports stick up above water so you can correctly position the
yacht
above it.
Next low water the yacht will be sitting on it and you close the valves
on
the tanks so the whole issue floats on the next tide and continues to
float
the yacht on every tide until the job is finished.
Then you flood the tanks again and the yacht sails away.
You could build a thing like that comparitively cheaply as there is
nothing
mechanical on it at all.

You are talking about fairly significant tides. If, at low water you
have the dock situated on the beach just above the tide line (you need
it above the tide line as you are going to drain all the water out of
the tanks at the next low water) you are going to have a device that
is two or three feet thick, say 3 feet. So, to get sufficient water
over it to load my boat you are going to need in excess of 9 foot
tides, say 10 foot tides.

Next, this is not going to be some little dinky device. You are
talking about a 40 ft. boat with a breadth of, say 12 feet, and a
draft of 6 feet. Your tanks and cradle is going to be a fairly
significant structure and of course you are going to get caught in a
trap. Every time you make it bigger or stronger it becomes heavier and
thus needs larger tanks to float it and that makes it heavier and it
needs to stronger and that takes more tanks that make it
heavier...........

Another point is that a certain number of modern, bolt on keel, boats
won't stand on their keel so you need an even more substantial cradle.

Basically what you are talking about is called a floating dry dock and
is in fairly common use, except that you aren't pumping the tanks so
it will only work in areas with fairly big tides.

I still think it is a bad idea. Redesign it to pump the tanks with an
air compressor (remember to do all this heavy maintenance you are
going to need a generator to furnish electrical power so why not an
air compressor) and make it into a real floating dry dock and it will
be rather more useful.

Bruce-in-Bangkok
(correct email address for reply)


Because lots of places that boats cruise do not have travel lifts, etc.
Drakes Bay here in Northern California is where Sir Francis Drake careened
his ship to repair the bottom. So every 6 hours they dealt with the water
and tides. Unless they built a coffer dam around the boat.