[Public-list] Tabernackles on AL30s

[Don Campbell]

Hi John;
    I take the  mast down every year to trailer the boat home for the
winter and thus have to raise it every year if I want to sail. The
easiest by far is a mast crane to lift a mast, safest too in the end.
The second way is with an A frame and you can see what they do in the
Chesapeake in the files on A frame/ mast raising. I find that it helps
if one can support the legs of the A with some dock lines at the
couplers .
    As for a tabernacle, the deck is not all that well supported for
loads fore to aft, particularly since the AL30 mast is as heavy as it
is. From experience raising the mast on Alberg 22s, which has a hinge on
the maststep, (but the mast only weighs about 40 pounds) it is necessary
to lift the mast past 30 degrees to horizontal before there is any easy
pull and real gain from a tackle on the head piece at the bow. The worst
thing that has happened with that mast is that it has been very easy to
get it off centre and then easy for it to fall to one side. A gin pole
helps considerably with changing the direction of the lift, even though
the vectors remain lower.  Even with this rather light and small mast,
there is a tremendous amount of loading forward at the hinge with low
angles of elevation. The other situation is that the turnbuckles will
easily bend as the mast rises, and so having the stays as either guides
or safety factors is a somewhat false sence of security. If you do bend
the screws in the turmbuckles and have to replace them before setting
out, it does get expensive.
    I also have an A frame for the 30,  since I was ticked that the only
game in town raised their crane rates to $3.00 a foot for raising masts.
3 lifts more than paid for the frame and lines. Just to prove that I
could do things with much fewer people than they use in Annapolis, my
wife and I raised the mast with the A frame. It took about 6 hours to do
so but I was being extremely careful as there were not a lot of choices
if we had an accident. Lowering is a much easier chore and far faster.
That system worked really well but depends on a straight lift to the
block at the top of the A frame. It takes a bit of adjustment to get the
lifting point and balance point directly below the block. (I use a 26
foot leg on the A and I think the Chesapeake one is a 24 foot leg so
there is a bit more wobble in the longer leg). Having a 4:1 lifting
system and a self tailing winch made things relatively easy from a
strength and loading on the arms point of view,  and the ST meant that
slippage and fatigue were not an issue.
    I don't think this boat was made for canal trips where masts need to
go up and down like a yo yo nor do I think it reasonable to modify the
deck to allow for such a system because it would change the weight and
balance so negatively,  unless you went with a temperature cured epoxy
and carbon fiber system. That being said, Ted Brewer thinks that deck
stepped masts are a weak system because there are two pivot points in
the design, one on deck and the other at the top of the mast. Any
weakening of the lower pivot by bolting it to a tabernacle just
increases instability and decreases safety.
    I'm filing this idea of tabernacles under K with all the other
Kingsland design modifications so loved by Lehman!
Don #528