[Public-List] Bulkheads

Thu Feb 4 19:25:05 PST 2016

picture of new knee: https://goo.gl/photos/38fxQRv566GU5HwN8

On Thu, Feb 4, 2016 at 6:24 PM, Hernán Scarnichia <hernanscar at gmail.com>
wrote:

> 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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