Hi, Ben, and list,
Compressing your stuff, left below for reference by others if needed, I
think I understand you to say that you tie (secure, however done) two lines
each to the INSIDE of the dinghy, at the lifting points.
These are used to put pressure on the tubes (inflatable in this case) which,
as you finish lifting, forces the forward tube downward as you pull upward
with the lifting points.
My tackle actually is two points of lift, on 2 spread/bridles (currently not
safe, in my opinion; awaiting reply from Walker Bay) from 4 points on the
floor system. Extrapolating, assuming I get the risk factor successfully
dealt for my particular setup, I'd attach those 4 points to the straps/large
laid line?
I see nothing to prevent side-to-side movement in this setup; my current has
crossed ratchet straps from the transom (outside on the far side of the 2
interior factory lift rings, accomplished by a ring nut on the outside of
the interior eye bolt) and the bow eye, going under the dink, providing some
lift security as well as very strong pressure both inbound and against
side-to-side.
My arch frame is probably closer to 60* than 45; due to mis-execution of the
plans, the davit tubes are at about a 10* angle upward at the stern (plays
hell with the solar panels getting the best they can!), and, with the joint
of the support tube being about 15" lower than that, a resultant angle of
perhaps 15* obtains after accounting for the hoisting blocks not being at
the bottom of the dink floor. The angle gives good compression against
movement, as well, as it forms over the inflatable tube.
Not having the impressive welding setup you do, let alone any skills if I
did :{/), I'm unable to attach cleats permanently, other than those I use
to tie off the hoist lines (which were one of the few things the welder who
did my arch did well), so I'm further in trouble, there.
As long as I have your engineer's mind engaged, perhaps you could speculate
on how to overcome the lifting challenges I have:
When I designed our arch about 5 years or more ago, I used our current
dinghy's hardpoint mounting setup to determine both spread and depth. As it
was a fiberglass dinghy, with extended (moreso than our current) stern tubes
and hard-point mounts at the bow locker, there were no safety issues nor fit
difficulties.
Our present dinghy has only a bow-eye back-end (a pad eye mounted to the bow
eye bolts) and the transom eyes. That's way longer than the spread on our
davit tubes. The inflatable tubes are also smaller diameter than our
original, so that necessitated bringing in the hoist points from the
original, in order to achieve the jam-fit in the corner between the arch and
the support arm mentioned above. There's my graph-paper sketch of our arch,
as well as lots of pictures, in our gallery, if you're interested...
Walker Bay's factory solution to my dilemma, apparently common, as it's
plastic, and not fiberglass, making it impossible for hard points inside the
tubes area, is to put eye bolts in the removable-paneled floor system ("the
bilge" feature on the Genesis models), make a lifting bridle, and haul away.
They claim full safety in a dinghy filled with water; we have nothing other
than the seats in ours when we hoist. However, there has been significant
deformation of the floor system, and damage at the front where there's no
forward latch for the locker section, due to the lifting stress on whatever
type of plastic it is that it's made from.
Our dinghy hangs out notably from both sides of the arch, so there's no
practical way to hoist using the davit arms, using their hard points,
without a significant angle as it's raised (our lifting points are much
closer together than theirs), or using a bar (making it impossible to lift
high enough to prevent swing) to accommodate that difference (never mind
what we're supposed to do with it when it's not slung!)...
Does this presentation "parse" sufficiently?
Thanks.
L8R
Skip, yours below, not my usual practice
PS What's a "pinxit"?
Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.yahoo.com/group/TheFlyingPigLog
and/or http://groups.google.com/group/flyingpiglog
"You are never given a wish without also being given the power to
make it come true. You may have to work for it however."
(and)
"There is no such thing as a problem without a gift for you in
its hand. You seek problems because you need their gifts."
(Richard Bach, in Illusions - The Reluctant Messiah)
----- Original Message -----
From: "Ben Okopnik" <[email protected]>
To: <[email protected]>
Sent: Sunday, August 29, 2010 1:00 PM
Subject: Re: [Liveaboard] davits and security (was)
On Sun, Aug 29, 2010 at 10:30:40AM -0400, Flying Pig wrote:
> Ben, could you expand on angle of secured dinghy methods?
Sure, Skip; I'll just give my favorite method here; I like its
simplicity and minimal extra gear.
Assuming that you want the dinghy angled 45° or so, you'd measure its
width and calculate one side of the right triangle that you'd be
forming, where the width of the dinghy is the hypotenuse (damn, it's
been a mort of years. I actually had to stop and think about this...
right, that'll be sqrt(width^2/2), or about 2'10" for a 4'-wide dink.)
Anyway, at that height below your davit arms, mount a cleat (mind the
lead and where the tips are!) to each of your uprights, or on your
toerail if it's at the appropriate height. You'll also need a cleat near
the inboard end of each of the davit arms. Next, make up four pennants
in large-diameter soft-laid line or flat strap, with a shackle at one
end. That's it for the hardware.
To secure the dinghy, snap the pennant shackles into its lifting points;
if you have three points rather than four, then the single one gets two
pennants. Hoist the dinghy up to the level of the lower pair of cleats,
grab the pennants that are closest to the big boat's stern, heave them
up tight to the cleats, and secure them. Last, hoist the dinghy the rest
of the way, grab the remaining two pennants, heave them in toward the
inboard end of the davit arms, and cleat them off.
/Voila/, angled dinghy. Adjust the pennants and arrange anti-chafe to
taste, then stand back and admire your beautiful creation, "Still Life
with Davits". Don't forget the fancy pinxit. :)
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