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CARBON SPARS - FEEDBACK from Fireball Class 2 section masts : Repairs : Insurance
From:
Thomas Egli
To:
Peter Hinrichsen
Sent: Monday, December 02, 2002 5:01 PM
Subject: RE: Carbon Masts
Peter,
For the Fireball, and I suspect the FD, the two-section mast idea
isn't the good idea it appears to be at first glance.
The Selden/Proctor's filament wound masts have a 'step-down'
transition to go from a straight section to the tapered upper section.
The pre-preg tape on mandrel Superspar masts are tapered from
top to bottom. They have to be, or you couldn't get them off the
mandrel. The filament-wound CST masts are either straight tubes
(for cats) or tapered. None of them are two-piece.
In my mind, there are only two applications where the two-section
mast makes sense. The first is when the class mast is already a
two-piece mast (eg. Laser, Topper), and it would be a simple matter
to replace the upper section with carbon. Superspars seems to be
quite aggressive in promoting this approach for those classes (see
http://www.superspars.com/topmasts.html). The other application
is for classes (Skiffs, Int'l 14) where the mast below the hounds is
kept in static column mode by the rig tension (i.e. the shape of the
lower section of the mast is 'locked' into position by the rig tension),
and the mast above the hounds is flexible enough to shed gust loads.
On some of the older (mid-nineties) 18' skiffs, the lower part of the
mast consisted of an aluminium tube, and the upper section was a
fibreglass tip. Interestingly, carbon was not used for the tip, as it
didn't deflect enough to provide good gust response and didn't have
the toughness to resist the cyclical loading. Both problems have
since been resolved, but one must keep in mind that skiff rigs are
rigidly locked into shape below the hounds, sort of like a modern
sailboard rig, which is a 'hard' sail. You then end up with different
rigs for different conditions (18' skiffs have three rigs, sailboards
even more), not the thing to do if you want to control costs.
In any case, a two-piece mast results in a hard point which
invariably messes up the bend and dynamic properties. It is of
no concern for the two cases mentioned above, but the 'soft'
Fireball (and FD) rigs are based on masts that bend smoothly
from the gooseneck on up to allow for adjusting the rig to suit
the conditions. It would obviously be possible to 'redesign' the
Fireball/FD rig so that it acts like a Skiff/International 14 rig, but
that would essentially entail going from a 'soft' to a 'hard' rig, with
all the attendant problems such as full-length battens, additional
spreaders and higher rig tension. More rule changes coming up!
I
guess that a general rule-of-thumb would be that two-piece masts
can be used for classes with 'hard' rigs (49er, Skiff, 14), but the
one-piece masts are required for classes with 'soft' rigs.
Regards,
Tom
In passing, the Fireball class has been looking at two-piece masts,
to be able to use 20' containers for shipping. Our mast is just a bit
too long, less than ix inches, to fit into a twenty footer. But instead of
having a removable upper section, we've been looking at having a
removable lower (below gooseneck) section. That way, the bend
characteristics of the mast are maintained, you get the benefit of a
stronger mast at the mastgate (a weak point for Fireball masts), and
the mast material doesn't matter. Routing of halyards can be a problem,
and you always have to wonder how the temporary connection is made.
-----Original
Message-----
From: Peter Hinrichsen [mailto:hinrichsen@videotron.ca] Sent: Monday, December 02, 2002 09:50 To: Thomas Egli Subject: Re: Carbon Masts
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