Courtney Thomas wrote:

Wishing to attach some [SWL 2000kg] 4-part fiddle blocks possibly mid-boom
[aluminum], probably using either 1/2 or 9/16" nylon lines, what would be
the proper technique to insure sturdy attachment and avoiding interference
with boom function ?

Mobile attachment on boom would be even more desirable if not fraught with
various perils :-)

Appreciatively,

Courtney

With roller reefing, a moveable attachment for the main tackle could
use a "claw" with wheeled fingers to reach around the boom.

Presuming you have slab reefing, a moveable attachment for the main
tackle could ride on a bridle or bar hung under the boom, or between
two pennants made adustable in position. The bridle will need
vertical room. If you can manage it, you want the boom et al to
clear a 6 footer's head, I suspect. A re-inforcement and track on
either side of the boom could entertain cars linked with a bail to
attach to the main tackle.

Reaching or running, the free running tackle will always want to
move foreward on the boom, and you may feel it could stress the boom
at an attachment and cause the boom to break in a gust.

The attachment(s) could be re-inforced with a plate inside or
outside the boom. Many rivets would spread the load, a few through
bolts may concentrate the stress.

I think you would have better results with fixed attachment, suited
to clear your dodger / bimini. A fixed yoke strap may do the job
admirably. Two triangular plates with a loop joining one corner on
each would spread the load over a large area on a thin boom.

To avoid overstressing the boom, an attachment outside of the 2/3
point toward the after end is best. End boom attachments may put a
lot of force on the gooseneck if the main is sheeted hard, as it may
pull foreward somewhat going to windward, and sideways somewhat when
reaching or running, but I feel most comfortable with it that way on
my boat.

A good boom vang will make any requirement for a main traveller
moot. A strong topping lift is good for many reasons, especially for
hoisting things like the engine or a MOB.

A preventer will be needed when running. A good vang can double in
this regard.

My vang hangs on a strong "L" hook in a strong plate under the boom
at about 1/3 boom aft from gooseneck. A small pin on the toe of the
L stops the hook from falling out when flogging, but it can be
twisted backwards to disengage it and to remove the hook and tackle,
not that it is often desirable to do so, except when de-rigging. A
snap shackle on one block of the tackle at the mast base allows
attachment to a stanction base when used as a preventer.

You have to live with your boat.

Terry K