[Public-List] Bulkheads

[Hernán Scarnichia via Public-List]

Chip,
I just did exactly that on the forward lowers knees last weekend. cut along
the inboard edges and drilled out the rotten plywood, leaving part of the
tabbing in place to locate the new 3/4 G10 knees. as I removed the plywood
I was able to see how bad the tabbing had delaminated from the hull.
cleaned and sanded the inside of the old tabbing as much as I could to get
a better bond.
I sanded to bare fiberglass about 8 inches each side of the knee to bond
more tabbing. I cut into the flange/stringer holding the shelf to allow the
knees to extend below the shelf.
I used G-Flex toughened epoxy thickened with colloidal silica to bond the
new knee to the hull and 4 or 5 layers of 30oz cloth to tab into the hull
and to the shelf flange/stringer.
G10 is hard to cut, I used an angle grinder. I haven't tried drilling yet
but I suspect is not going to be easy.
I would suggest trying to align the new knees as best as you can with the
chainplate direction of pull, mine are not perfectly aligned and will make
it harder to install the chainplates, planning on adding some epoxy to get
a better angle.
here is a picture of the new G10 knee, not perfect but way stronger than
what was there.

On Thu, Feb 4, 2016 at 3:06 PM, Chip Dance via Public-List <
public-list at lists.alberg30.org> wrote:

> #456 has had the 5/16" bolt upgrade at some point by a PO, but she sat
> neglected for so long, much needs to be rebuilt/replaced, including the
> bulkheads (standing water up to the v-birth). I haven't test drilled the
> knees yet, but I would be very surprised if the plywood within is still of
> any use. However, the tabbing and glass around the knees still looks good.
> So I wonder if there is any advantage or concern with performing surgery on
> the knees? My thought is this:
> cut into the knee along the edge, gut out the plywood and replace with G10
> cut to fit the void and adhered with thickened epoxy or ??,  re-drill the
> bolt holes using the remaining for/aft parts of the knee as a guide,
> re-insert the chain plate, re-glass the edge of the knee and perhaps
> another layer or two over the entire knee and tabbing.
> The advantages I see in this refit process: re-using the original tabbing
> so you know the plates and knees are situated and adhered exactly as they
> were designed and built originally; eliminates the need to add new tabs (a
> concern for the neophyte); eliminates all concerns of future plywood rot
> (no plywood, no plywood rot). Of course maintaining a good seal around the
> chainplates would still be advisable, but not as critical as if the knees
> contained plywood.
> Keep in mind I am new at this, hence the sought advice, so I may not be
> thinking of everything.
>
> Thoughts?
>
> Chip
> #456
>
> On Thu, Feb 4, 2016 at 4:23 PM, Gordon Laco via Public-List <
> public-list at lists.alberg30.org> wrote:
>
> > Hello Stephen,
> >
> > I was a great believer in SikaFlex in my wooden boat days, but have
> turned
> > back to Boatlife 'Lifecaulk' for Surprise.  I think it adheres better to
> > fibreglass than SikaFlex (but not too well as with 5200)
> >
> > I've never come across a non-curing butyl but do recall the stuff
> > originally
> > used in our boats was something similar.
> >
> > Gord #426 Surprise
> >
> >
> > On 2016-02-04, 5:54 PM, "Stephen Gwyn via Public-List"
> > <public-list at lists.alberg30.org> wrote:
> >
> > >
> > > So what are people's favourite sealant? I've been using
> > > BoatLife polysulfide sealant. Polyurethane  (3M5200 and Sikaflex)
> > > is too permanent. Silicone is permanent enough and once you
> > > use it, nothing will stick to where it has been.
> > >
> > > I was reading a british sailing, which recommended a butyl sealant
> > > which stayed sticky indefinitely, meaning that when the seal flexed
> > > and split, it would just seal itself again.
> > >
> > > Thoughts?
> > >
> > > SG
> > >
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