I am also planning to Vac bag my bulkheads but not to use prepreg. I dont
see the advantage of prepreg if you dont bake it, its hard to store unless
you have a bloody cold room. Using a vac to hold the carbon in place and
suck up excess resin is common sense. I understand that if my boat passes
min weight and swing I'm fine. Better if its just under spec weight. If it
doesn't pass I have to add lead and take a penalty of being brought up to
the spec weight (not spec minus tolerance that I might have been able to get
away with) If you have the gear I can't see why you wouldn't want to Vac any
surface that you could (especially the inside surfaces) given that this will
improve the consistency of resin coverage, reinforcement draping, core
contact as well as fibre % content. You will have to cover the outside
surfaces with excess resin to fair and polyurethane for UV resistance anyway
so its not so much an issue. However this might be easier without resin
"runs" or lots of "cloth texture" that you can get rid of by using the peel
ply.
For better or worse we can't use heat setting resins. The process is just
way too expensive for the added benefit.
Look carbon is good, PBO is good, titanium is good, boron is good,
toothbrushes are good. I would like a carbon - PBO hybrid teflon coated
monofilament bristle titanium impregnated composite toothbrush with a
paladium hydrogen fuel cell battery made from prepreg conducting gold coated
carbon/epoxy resin individually autoclaved and the lightest of 100 specimens
selected for me, but I really doubt that it would do a better job than my
old daggy one that has been sitting on my sink for a month, and that one
does not have the prepreg. But you know, these things are good so a lot of
these things must be fantastic. I'll put it with my Venus endorsed ultra
carbon tennis racket and my gortex frilly tennis undies.
Lets not use all the planets resources just because we can, some cost
benefit sanity would do us well.
On the other hand I'm vaccing because its easier than scrupulously worrying
about hand layup resin content issues and because I already have a Vacc pump
and gages discarded from my lab and because I want to try to make a good
boat and, because I can. OK I'm a paradox. But you will note, a "cheap"
paradox.
The most popular sizings either silane and volan are epoxy compatible. I
dont think the average person has problems achieving wetout with the hybrid
we are using. It's the opposite problem, as you point out, getting rid of
excess resin that serves no usefull purpose on the inside of the boat. To do
this you need to fuss over every square inch, virtually ensuring complete
wetout. You will have more problems with bubbles blowing from the core
imperfections than you think if you dont vac. Vacc will sure fix this. That
alone is a good enough reason to use it.
Polyacrylonitrile carbon is by far the largest source (90%) of carbon on
sale in the US and the rest of the world. PITCH fibres are not used for
strength sensitive requirements and, I understand, are mostly restricted to
specialist applications in high volume/cost sensitive industries like
automotive and injection moulded manufacturing. Am I Right?
Greg
USA009 -- The boat with the HIDEOUSLY EXPENSIVE Rose ensign made from 1/2
meter of pink sticky-back Insignia cloth pasted on the mainsail. My boat
will be the one with 2/3 of the surface taken up by commercial sponsors
logos to pay for the Insignia cloth design and its ultra precision
professional application (precise is good, so ultra precision CNC labeling
is sure to make it look extra good). You see it, I will be near, you can
come abuse me in person. I will do my best to show it to you on the down
wind legs. :-)
----- Original Message -----
From: "Dave Lindsey" <lindsey@xxxxxxxxxxx>
To: <BDally6107@xxxxxxx>; <Harveynestor@xxxxxxxxxxxxx>; "tom owen"
<tom.owen@xxxxxxx>; "Peter Patel-Schneider" <pfps@xxxxxxxxxxx>; "Paul
Stalker" <pgstalker@xxxxxxxxxxxx>; "Greg Ryan" <gregoryrryan@xxxxxxxxxxx>
Sent: Tuesday, November 25, 2003 2:10 AM
Subject: Swift Solo Questions
> Open letter to Bram and Swift Solo Builders
>
> This is a project I probably should not have undertaken. But I simple
> could not resist the opportunity. I love to build things and this has got
to
> be one of the sexiest things a guy could build and use.
>
> My problem is I have so many things on the go I'm finding it difficult
> to find the time to build. Run a business, finish the deck around the Hot
> tub, the fence and now to my surprise, new drain tile around the house.
> All I really want to do is build my boat!
>
> To date I have managed to rip my cedar strips and cut out the
stations.
> I have quickly read the rules and this has created a couple of questions;
> There was some question regarding the use of vacuum bags. Has this been
> resolved? At the very least I would like to vacuum bag the bulkheads and
> transom. Is this allowed? In fact I would like to vacuum bag the bulkheads
> using epoxy prepreg carbon fibre (make that FIBER for my American
cousins).
>
> I would like to consider vacuum bagging the inner surfaces of the hull
> and deck. However this would give the vacuum built boats an advantage
> because it would likely have a higher fibre to resin ratio making the hull
> stiffer and more durable. It is possible to use prepregs in a wet hand
> lay-up. This I think would not break the rules if the resin is allowed to
> cure without an external heat source, just the exothermic resin reaction.
Is
> this correct?
>
> This may sound like I'm splitting hairs but I have good reason. The
wet
> lay-ups process has a number a faults. First and foremost, it is difficult
> to control the resin to fibre ratio. When using carbon fibre, it can be
> difficult to achieve good resin penetration around all the fibre. As
amateur
> builders we generally don't know which of the two main types of carbon
fibre
> we are using (Pan or Pitch) nor do we know what type of sizing has been
used
> on the fibre. It is my understanding that a resin must be compatible with
a
> particular resin to get optimum performance. Prepregs solve these
problems.
>
> Thoughts?
>
> David Lindsey
> #47, British Columbia, Canada
>
>
>
>
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