Re: [bolger] Re: how urgent it is to seal up my new centerboard?

-Jay

On Mon, Jul 6, 2009 at 7:17 PM, Jay Bazuzi<jay@...>wrote:

A followup: I put 3 layers of epoxy on today, with 3-4 hours between coats, because that how my schedule worked out.

I originally planned to put only 2 coats, but once we were all set up it was very easy to apply, so we went ahead with a  3rd.  The end grain at the shaped edges was particularly thirsty, so I'm glad I added that extra coat.  I considered a 4th coat, but I want to save some for the next step, and buying another can of epoxy would mean most of it just sitting in the garage, waiting for trouble.

I hung the board up by 2 corners.  This mean I could get the edges and faces in one go.  I figured that having continuous epoxy around the edges would put strength where it mattered.

After it cures I'll lay it down on the sawhorses to fill the gouges and the groove at the edge of the lead sinkweight (scuffing for a good bond, of course).

-Jay

Port Townsend, WA

On Mon, Jul 6, 2009 at 9:06 AM, Jay Bazuzi<jay@...>wrote:

Thanks for your advice, Gary and David.  I have decided to seal the board before trying it out.  I bought some epoxy yesterday and did some test coats on scraps of the same wood that the centerboard is made of. Today I will buy some disposable roller covers and stuff, and start painting on the epoxy.

In last night's tests, it took about 2 hours for the epoxy to reach the tacky gel stage.  This is WEST with "Fast" hardener.  I guess the cool evening weather slowed it down a lot.  My first time using "real" epoxy, e.g. not a two-barreled syringe for fixing things around the house.

I like that idea of the leading-edge polyester rope.  The older centerboard took a beating at the lowest point, and I was worried about it there.  When shaping the edges, I left a little more material right there, so it would be stronger.  But had I known, I would have gone for the rope idea.  Next time :-)

-Jay

On Sun, Jul 5, 2009 at 8:22 PM, gbship<gbship@...>wrote:

If you take it out in salt water, make sure your rinse and dry it before sealing. The salt in the board will retain moisture and probably isn't good for epoxy adhesion even if it's dry.

Sounds like your board is one piece and not laminated of 2 or 3 layers of thinner ply. That makes it more prone to warping, and the longer it's unprotected the more likely it is to warp (and the surface to check or split). Also, in shaping the leading and trailing edges, you've exposed a lot more end grain than normal and the unprotected board will be quicker to soak up a lot of water.

I'd at least do the epoxy sealing before using it.

BTW, the best way to protect the leading edge of a leeboard or centerboard is to plane it flat and then attach and fair in a piece of polyester rope thoroughly soaked in epoxy. When the epoxy in the rope cures, it's like casting a stone in place. It will stand up to all sorts of abuse, short of dragging it on the pavement when you tow the boat home on the trailer (don't ask me how I know this . . .).

Gary

--- Inbolger@yahoogroups.com, Jay Bazuzi <jay@...> wrote:
>

> I have been building a new centerboard for my Bobcat. (The old one was
> warped, and was hard to raise and lower.)
>
> I have shaped a piece of 3/4" marine plywood: cut it, beveled the water foil
> edges, drilled the holes, cut the pivot hook. Then I glued & screwed the
> brass plates at the pivot hook, and poured the lead sinkweight.
>
> The instructions I have are to brush on 2 layers of epoxy, and then a couple
> layers of marine enamel paint.
>
> I have some questions about how critical it is to put the finish on the
> centerboard right away.
>
> - Can I take the bare centerboard out for a sea trial? Just an hour, in
> salt water.
>
> - Can I leave it bare and sail it for the rest of the summer, then dry &
> finish it in the fall?
>
> - If I don't ever finish it, how bad is that?
>
>
> -Jay
>

-Jay

Chris:
Mostly it's what I've observed. Anytime I leave a single piece of ply exposed, marine or otherwise, it eventually warps. Cheaper warps faster than expensive, though. The couple of laminated scraps I've left lying about seem to fair better.

My guess is there are two or three reasons for this. One is a single piece of 3/4 inch ply is going to be 7 or 9 layers (maybe 11?). Good 1/4 inch ply is going to be 5 layers, so a laminated 3/4 inch board will have 15 layers. The glue lines between layers also help. Also, I try to get some cross grain stiffening, that is having the surface grain run in different directions, if the layout on the panels allows for it. Two layers with a 90 degree orientation and the third with 45 degree orientation is ideal. Whatever warping stress develops in one layer is cancelled out by the others.

I've got an old centerboard laying around that's two layers, cross grained, of AC ply that's been sitting outside for years with less than perfect sealing and it hasn't warped.

It is definitely more work to build. I haven't yet cut 3 or 4 perfectly matching layers but the differences have been small enough not to be a bother. One way around that is to cut the layers slightly oversized, do the laminating, and then trim to the final size -- but that's even more work. But worth it, IMHO. I had a sticking dagger leeboard and sticking centerboard early in my career and dislike the associated tussles.

Gary

--- Inbolger@yahoogroups.com, Chris Crandall <crandall@...> wrote:
>
> > Posted by: "gbship" gbship@... gbship
>
> > Sounds like your board is one piece and not laminated of 2 or 3
> > layers of thinner ply. That makes it more prone to warping, and the
> > longer it's unprotected the more likely it is to warp (and the
> > surface to check or split).
>
>
> I wonder why you say this, Gary. I don't doubt your experience, but,
> more or less, one big piece of ply *is* laminated 2 or 3 layes of
> thinner ply.
>
> Now, it's true that one of the glue lines is thicker and stiffer (epoxy
> over resorcinol), and the sometimes the individual plys are thinner in
> thinner ply (although not always). But my guess is that the difference
> is fairly modest, and the work is substantially greater, along with the
> possibility of workmanship errors.
>
>
> > "Jay Bazuzi" jay@... jaybaz Date: Mon Jul 6, 2009 9:08 am
> > In last night's tests, it took about 2 hours for the epoxy to reach
> > the tacky gel stage. This is WEST with "Fast" hardener. I guess the
> > cool evening weather slowed it down a lot.
>
> That's pretty dang slow. I was using "fast" hardener epoxy in my
> climate-controlled basement yesterday, attaching gunwales to my 22-foot
> "power teal". That stuff went off in the cup within 15 minutes (and I
> had added quite a lot of fillers--fumed silica and milled fiberglass
> fibers. Two hours to gel? You sure that it's "fast" stuff you're using?
>
> -Chris
>

Hi Chris,

> That's pretty dang slow. I was using "fast" hardener epoxy in my
> climate-controlled basement yesterday, attaching gunwales to my 22-foot
> "power teal". That stuff went off in the cup within 15 minutes (and I
> had added quite a lot of fillers--fumed silica and milled fiberglass
> fibers. Two hours to gel? You sure that it's "fast" stuff you're using?
>

If I recall correctly, the big difference between fast and slow hardener is the working time, not the time to tack-free or fully cured state. I use West fast hardener almost exclusively due to the cool temperatures at my shop, and the stuff will remain tacky for a long time after it kicks, you just can't work with it for very long. Also, adding fillers always makes it kick off faster for me, especially coloidal silica.

Jon Kolb
www.kolbsadventures.com/boatbuilding_index.htm

> Posted by: "gbship"gbship@...gbship

> Sounds like your board is one piece and not laminated of 2 or 3
> layers of thinner ply. That makes it more prone to warping, and the
> longer it's unprotected the more likely it is to warp (and the
> surface to check or split).

I wonder why you say this, Gary. I don't doubt your experience, but,
more or less, one big piece of ply *is* laminated 2 or 3 layes of
thinner ply.

Now, it's true that one of the glue lines is thicker and stiffer (epoxy
over resorcinol), and the sometimes the individual plys are thinner in
thinner ply (although not always). But my guess is that the difference
is fairly modest, and the work is substantially greater, along with the
possibility of workmanship errors.

> "Jay Bazuzi"jay@...jaybaz Date: Mon Jul 6, 2009 9:08 am
> In last night's tests, it took about 2 hours for the epoxy to reach
> the tacky gel stage. This is WEST with "Fast" hardener. I guess the
> cool evening weather slowed it down a lot.

That's pretty dang slow. I was using "fast" hardener epoxy in my
climate-controlled basement yesterday, attaching gunwales to my 22-foot
"power teal". That stuff went off in the cup within 15 minutes (and I
had added quite a lot of fillers--fumed silica and milled fiberglass
fibers. Two hours to gel? You sure that it's "fast" stuff you're using?

-Chris

-Jay

On Sun, Jul 5, 2009 at 8:22 PM, gbship<gbship@...>wrote:

If you take it out in salt water, make sure your rinse and dry it before sealing. The salt in the board will retain moisture and probably isn't good for epoxy adhesion even if it's dry.

Sounds like your board is one piece and not laminated of 2 or 3 layers of thinner ply. That makes it more prone to warping, and the longer it's unprotected the more likely it is to warp (and the surface to check or split). Also, in shaping the leading and trailing edges, you've exposed a lot more end grain than normal and the unprotected board will be quicker to soak up a lot of water.

I'd at least do the epoxy sealing before using it.

BTW, the best way to protect the leading edge of a leeboard or centerboard is to plane it flat and then attach and fair in a piece of polyester rope thoroughly soaked in epoxy. When the epoxy in the rope cures, it's like casting a stone in place. It will stand up to all sorts of abuse, short of dragging it on the pavement when you tow the boat home on the trailer (don't ask me how I know this . . .).

Gary

--- Inbolger@yahoogroups.com, Jay Bazuzi <jay@...> wrote:
>

> I have been building a new centerboard for my Bobcat. (The old one was
> warped, and was hard to raise and lower.)
>
> I have shaped a piece of 3/4" marine plywood: cut it, beveled the water foil
> edges, drilled the holes, cut the pivot hook. Then I glued & screwed the
> brass plates at the pivot hook, and poured the lead sinkweight.
>
> The instructions I have are to brush on 2 layers of epoxy, and then a couple
> layers of marine enamel paint.
>
> I have some questions about how critical it is to put the finish on the
> centerboard right away.
>
> - Can I take the bare centerboard out for a sea trial? Just an hour, in
> salt water.
>
> - Can I leave it bare and sail it for the rest of the summer, then dry &
> finish it in the fall?
>
> - If I don't ever finish it, how bad is that?
>
>
> -Jay
>

If you take it out in salt water, make sure your rinse and dry it before sealing. The salt in the board will retain moisture and probably isn't good for epoxy adhesion even if it's dry.

Sounds like your board is one piece and not laminated of 2 or 3 layers of thinner ply. That makes it more prone to warping, and the longer it's unprotected the more likely it is to warp (and the surface to check or split). Also, in shaping the leading and trailing edges, you've exposed a lot more end grain than normal and the unprotected board will be quicker to soak up a lot of water.

I'd at least do the epoxy sealing before using it.

BTW, the best way to protect the leading edge of a leeboard or centerboard is to plane it flat and then attach and fair in a piece of polyester rope thoroughly soaked in epoxy. When the epoxy in the rope cures, it's like casting a stone in place. It will stand up to all sorts of abuse, short of dragging it on the pavement when you tow the boat home on the trailer (don't ask me how I know this . . .).

Gary

--- Inbolger@yahoogroups.com, Jay Bazuzi <jay@...> wrote:
>
> I have been building a new centerboard for my Bobcat. (The old one was
> warped, and was hard to raise and lower.)
>
> I have shaped a piece of 3/4" marine plywood: cut it, beveled the water foil
> edges, drilled the holes, cut the pivot hook. Then I glued & screwed the
> brass plates at the pivot hook, and poured the lead sinkweight.
>
> The instructions I have are to brush on 2 layers of epoxy, and then a couple
> layers of marine enamel paint.
>
> I have some questions about how critical it is to put the finish on the
> centerboard right away.
>
> - Can I take the bare centerboard out for a sea trial? Just an hour, in
> salt water.
>
> - Can I leave it bare and sail it for the rest of the summer, then dry &
> finish it in the fall?
>
> - If I don't ever finish it, how bad is that?
>
>
> -Jay
>

Jay,

Assuming you are, indeed, talking about Marine (hardwood, no voids) plywood (and not exterior softwood plywood) you can try it out without sealing it. When you're done, just make sure you dry it out slowly, evenly, and thoroughly before proceeding with epoxy and paint. If it has voids, you can still do it, but it'll take a good long time to completely dry out.

One thing I frequently recommend is to use 2-part polyurethane paint for the foils. Very slippery and very tough. Foils often take some abuse, and this paint helps shed the hard knocks.

David G
Harbor Woodworks

"Life's a tough proposition, and the first 100 years are the hardest" -- Wilson Mizner

*********************

--- Inbolger@yahoogroups.com, Jay Bazuzi <jay@...> wrote:
>
> I have been building a new centerboard for my Bobcat. (The old one was
> warped, and was hard to raise and lower.)
>
> I have shaped a piece of 3/4" marine plywood: cut it, beveled the water foil
> edges, drilled the holes, cut the pivot hook. Then I glued & screwed the
> brass plates at the pivot hook, and poured the lead sinkweight.
>
> The instructions I have are to brush on 2 layers of epoxy, and then a couple
> layers of marine enamel paint.
>
> I have some questions about how critical it is to put the finish on the
> centerboard right away.
>
> - Can I take the bare centerboard out for a sea trial? Just an hour, in
> salt water.
>
> - Can I leave it bare and sail it for the rest of the summer, then dry &
> finish it in the fall?
>
> - If I don't ever finish it, how bad is that?
>
>
> -Jay
>

-Jay