[Public-List] Replace chainplate knees

Tue Apr 11 18:29:47 PDT 2017

Brenton,
I just did this last spring. Your plan looks good overall. Ill write some
comments below on what I did different but take my advice with a bunch of
salt... I'm NOT an engineer or rigger. My boat #414 is a liner boat so
there may be some differences.

- Don't loosen only the forward lowers. loosen all lowers, fore and aft to
prevent the mast from bending backwards if the aft lowers are tight and the
fore lowers are loose. the mast will not fall over, you don't need halyards
as long as the upper shrouds and fore/back stays are in place. The mast may
oscillate a little bit if you get 30kt of wind or so.
- If the old tabbing is not delaminating from the hull it may be worth
keeping at least some of it as a reference for aligning the new knee. I
kept part of the tabs on the side opposite the chainplate.
- I think the shelf is a structural stiffener for the hull. I would
recommend drilling out the rivets that hold it to the hull and using the
old shelf as a template to make a new one out of plywood. then bolt the new
shelf to the hull flange instead of riveting.
- I built the new knees out of 1/2" G10. no more plywood in there to rot in
case the chainplates leak (G10 is a fiberglass manufactured sheet, buy a
12"x12" and you can cut both knees)
- I did what you are planning to do and glued the knee to the hull and
tab/flange with thickened epoxy. But I read its better to leave a gap
between the knee and hull so that the tabbing is taking all the strain and
spreads the load better, reducing the dimples on the hull when you tighten
the shrouds.
- I think I did 4 layers of a bi-axial cloth for the tabbing. I did not
cover the knee completely because the cloth was too thick to turn around
the inboard edge of the chainplate.
- I did not put any sealant between the chainplate and knee. but my knees
are solid fiberglass and can't rot.

here are some pics https://goo.gl/photos/w63gRH4Zf2wk2FCy8

Good Luck with the repairs. Write if you have any questions, and please
post some pictures of your replacement knees when you are done.

Hernan

On Tue, Apr 11, 2017 at 4:43 PM, Brent Higgins via Public-List <
public-list at lists.alberg30.org> wrote:

> Hi Everyone,
> Happy spring! I have put this project off long enough. I need to replace
> myforward lower chainplate knee on the starboard side. It’s a disaster and
> I’mguilty of probably waiting too long than is safe. I posted a couple
> photos on the Facebook page along w/ this email. I’ve tried to do my due
> diligence and read as many threadson the public list/internet as possible
> and have the following plan, which I hope folkswith experience can validate
> (or correct where needed). The boat is on the hardfor this project. I am
> still a novice at boat repair and a little nervous. Herewe go:
>
>
>
>    - On deck, loosen my forward lower shrouds on theport and starboard
> sides. I may also use my halyards hooked to port andstarboard deck cleats
> for some extra mast stability (not sure it’s necessary/helpful).
>    - Remove starboard lower shroud from chainplate,then remove
> bolts/chainplate.
>    - Next, cut away rotted knee using a flat blade onan oscillating
> multi-tool.
>    - I had hoped to avoid replacing the shelf, but itdoes look beyond
> repair. So, I’ll likely cut it away entirely, salvaging theteak trim if
> possible.
>
>    - Alternative is to just use some rot repair onthe rotted section and
> glass over it for strength. Seems a little lazy butwould get me through a
> few more seasons. I have future plans w/ the v-berth, soit could be nice to
> put this off awhile if safe.
>
>    - Carefully grind away the old tabbing and cleanthe exposed material.
>    - Template out knee on some cardboard or scrap.Once it fits, I have
> some 3/8” marine plywood. I was thinking I’d laminate 2 piecestogether for
> strength.
>    - Patch or replace the shelf.
>    - Dry fit the knee and chainplate but wait todrill any holes for the
> bolts.
>    - Mix some thickened West System epoxy and apply abed of it on the
> points where new knee and deck/hull/shelf meet.
>    - Setthe knee and let the epoxy kick.
>    - Applytabbing in 3 layers, starting w/ something like 5” and working
> down.
>    - Fiberglassthe knee in completely.
>    - Fitthe chainplate, drill 5/16” holes for new bolts.
>    - Bedchainplate in 4200, bolt together, tightening over the next day or
> two.
>    - Caulkaround the chainplate on deck to seal and keep up with this
> regularly to avoid ever having to do this project again! I do not have
> chainplate covers.
>
>
>
> Thoughts? One of the main reasons I bought the boat was to learn how to do
> this stuff, but when it comes to these really important structural
> components, I definitely don't want to take any chances. Thanks in advance
> :-)
> Best,
> Brenton
> s/v Ethel Jean
>
>
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