Posted by Alan Kusinitz (akusinitz@…>)
At one point without my initial knowledge
the yard threaded the holes at the base of the mast and replaced the bolts that
go through the step collar from the smooth pins to threads. This was done after
reinforcement inside of the base of the mast of about a quarter inch of
fiberglass so the threading was through this as well. The next time I unstepped
the masts I saw some abrasion of the threading. I did not seen any separation of
the layers. This certainly is an area of high stress. This was unsatisfactory
of course but did not rip anything apart. Just one data point.
Alan
From: freedomyachts2003@yahoogroups.com
[mailto:freedomyachts2003@yahoogroups.com] On
Behalf Of michel.capel
Sent: Tuesday, July 04, 2006 1:37
PM
To:
freedomyachts2003@yahoogroups.com
Subject: [freedomyachts2003] Re:
CF Masts on 1985 Freedom 33/35 cat-ketch
I see the point in your very good explanation of why
you should use
rivets. One thing that pops up with me, is the fact that you use
tapped holes and machine screws, not selftapping screws. The latter
would indeed be disastrous for the CF laminate. If the holes have
pretapped threads, I would thing the ‘prying’ force in the laminate
would be mitigated.
I found only solid holes with good threads 5 years after a track was
screwed to my then new main mast. Nevertheless, I will only use
rivets from now on.
Michel
— In freedomyachts2003@yahoogroups.com,
“katorpus” <katorpus@…>
wrote:
My strong recommendation is that you go with Monel rivets and NOT
screws for the following reason.
The rivets are “loose” in their holes and the force applied to
the
mast is that of COMPRESSION between the track and the “swollen”
back
side of the rivet. The “weakening” of the mast which results
from
drilling all the holes is proven to be neglible.
The screws, by design, “bite” into the hole sides and introduce
an
EXPANSIVE force (multiplied by the number of screws)which is
applied
continuously (forevermore)in what amounts to an attempt to
“pry”
the
fibers & resin apart. Any subsequent corrosion of the screw
(dissimilar metal in sail track)will only increase this force over
time.
You will inevitably “lose” some of either (screws or rivets),
but
when you “lose” a rivet (usually just the head), the cure is to
drill out the remaining core with the SAME size hole you started
with originally and replace the rivet.
The “cure” for a lost screw is going to be a BIGGER screw and/or
a
bigger hole.
— In freedomyachts2003@yahoogroups.com,
“spjwpja” <spjwpja@>
wrote:
Well, we have discussed this and there are different views. In
addition to the glue we will screw through the centre of the
track
along the entire length, so this should be fine when the mast
flexes. We were looking for a track with flanges to provide a
wider
base, either for glue or for rivets/screws on either side but
had
difficulty finding one. So we have a nice but narrow track with
only
room for central screws.
I’ve gone a bit over the top and will also insert an antal track
on
top of the track we are fixing - so it should be super-slidy.
The
work is being done in the same yard that Nick Charman keeps his
boat
so you will also be familiar with the discussions on the full
batten
at the top of the mast and making a sail/track fitting that
keeps
the batten end away from the mast, so we can still bring the
main
forward of the boom by a fair way.
Thanks for the advise,
Philip
— In freedomyachts2003@yahoogroups.com,
“michel.capel”
<michel.capel@> wrote:
Hello Philip,
I can’t give you a better answer than you gave yourself; I
found
the
same layup in my 1981 original TPI mizzen and in my in 2000
replaced
Goetz MT mainmast. I think they wrapped prepregged
fibre
(carbon
and
glass) around a mandril/spindle, put on resin and hot cured
it.
In
1981, I don’t think they already used vacuum bagging.
A question: on most Freedoms, the tracks are riveted or
screwed
to
the masts (in my case: mizzen riveted with monel or stainless
rivets, main mast drilled and tapped and machinescrewed.)
Why
don’t
you just use rivets or screws? If there were any risks,
Freedom
would have found this out long ago and changed this approach.
You probably have taken this into account when deciding to
glue
the
track on, but as far as I know, there must be a fraction of
freedom
of movement between mast and track because the masts bend. The
track
has to follow this bending. Aren’t you worried that the glue
breaks
loose because of the different properties of mast and track
when
they bend?
Michel
— In freedomyachts2003@yahoogroups.com,
“spjwpja” <spjwpja@>
wrote:
Hi,
re: Freedom Express, 1985 UK freedom 35 cat-ketch (long keel)
I am gluing track onto my CF masts (and keeping the
wishbone
rig).
We noticed that the mast is not just made from CF - there
appear
to
be several layers. We rubbed the outer coat flat down to
layer
2
and
stuck test piece on the base. This pulled off we 25 lb
force
and
twisting motion, pulling some of layer 2 away.
- smooth black outer layer,
- polyester layer
- CF
- polyester
My question is does any one know exactly what the different
layers
are made from and how the masts were made up?
Philip
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