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There are a number of ways to install a mast
ram.
There is a Z-Spar mast ram kit that
includes the car, the track, the tube, two ends for the tube and a fitting for the
foredeck. A sheave for the ram up control is already installed in the track. I believe
all/most UK 505s have this. The foredeck fitting and a similar fitting on the car, have a
"T" cross section, while the ram tube ends have a slot. I think people who use
this ram kit screw or rivet it to the mast. While I have never bought this kit, if I did,
I would make a Delrin backing plate to go inside the mast and tap it, so I could use bolts
to hold the track on the mast. Rivets are not strong enough in my opinion. I am not a fan
of screws either.
In the US we normally use a Waterat mast ram kit. These are available with several
different ram cars and corresponding tracks. We've used Harken (at least two sizes) and
Frederiksen ball bearing cars, as well as a Ronstan car with four rollers. The ball
bearing cars apparently work well in tension, but not so well in compression, so I suggest
the Ronstan car and track if you go this route. Waterat uses an aluminium ram tube, which
is available with reinforced ends. A carbon fibre ram tube with reinforced ends is also
available from Waterat. Waterat uses a different fitting on the ram car and foredeck than
that used by the Z-spar kit. It is a "U" in cross section, and wide enough that
the entire end of the ram tube fits inside the U. Waterat drills holes in this fitting to
match the mounting holes on the ram car. The Waterat ram kit normally includes a plastic
(probably Delrin) backing plate with tapped holes that match t! he track, so it is easy to
install and very strong. The kit also includes a block to turn the the ram up control line
down. With either kit, rigging the control lines, getting the correct mechanical advantage
(I like 8:1 up and 16:1 down for my high tension rig) , but many have 4:1 up and 8:1 down)
and figuring out where to lead the control line tails is up to you.
Some 505s need to be reinforced where the fitting on the foredeck goes. We put them
directly over the watertight bulkhead. At least with the high rig tension North sails rig,
we get considerable compression load on the mast ram tube, which can push the deck fitting
into the deck (creating a depression in the deck) if it is not built strong enough.
There is a detailed article about how to rig a mast ram
using the track on the mast, in an issue of Tank Talk from Spring 2001.
Tank Talks are available on the web at:
Cheers,
Alexander Meller |
What to Do With Mast
Rams
