Severely cracked leading edge of centerboard DSII

[hectoretc]

Greetings all - Land careened my recently acquired "old" DSII today to see if the centerboard pendants were firmly attached, and fortunately found they are, but unfortunately found the CB looks like it's had a bad day (or year).


There is about an 18" crack along the leading edge which has completely seperated the two halves of the board. With my fingers I can pry it apart and see the board is hollow inside. (hoping that is normal)


Assuming I'm not looking for performance, rather looking for the most legitimate, but inexpensive way to get my boat in the water, can this crack be repaired with normal fiberglass mat & resin? I clean the wounds but basically glue it back together with resin & matting overlays, and then sand reasonably back to shape again.
Does that idea make anybody shudder with terror? Is this CB a total loss? What are my options Doc?
Thanks,

[GreenLake]

Basically, fiberglass is pretty repairable, as a rule. And, if your goal is merely functional as opposed to optimized, you have a little more wiggle room.

However, a few things are non-negotiable.

1. After the repair, the CB needs to be strong enough that you can stand on it, in case your boat capsizes (in high winds, it probably needs to be the strong anyway to withstand the side forces). That means, your repair has to be structurally strong, not just cosmetic.
2. You probably want to get the board watertight (again).
3. While you are dealing with the edge(s) already, you might want to improve their shape a little bit - full profiling probably requires a new board, but you can do better than factory built.

The first thing you'd need to do is to carefully inspect the CB for hidden damage. Are there any other areas where the laminate is weak? Perhaps the CB was damaged by being bent - that could mean less-visible damage in other places.

Second, you need to grind away all bad fiberglass - it will extend somewhat beyond the cracks. The edges you need to grind at a really shallow angle 1 in 12, to give new laminate a holding ground. Up to that point, all you've invested is sweat equity and sandpaper.

Third, you'd want to build up the laminate over the cracks. As a rough guide, three layers, cloth, mat, cloth would end up at about 1/16". Use a good laminating epoxy.

Read the Epoxy book (systemthree.com) or the Fiberglass Boat repair manuals on the Westsystem.com site, for details on working with epoxy and basic techniques. If you haven't worked with epoxy and glass before, lay up a bit of practice laminate, so you don't make all your beginners mistakes on the real thing.

If your CB is really hollow, it might be a bit challenging to get the patch supported, because you'll probably have to cut away so much bad laminate that there's a gap. If so, come back here with new photos to get suggestions tailored to your situation.

I would also laminate one or two layer of glass around the leading edge. You can improve your CB profile by making the leading edge look like a half-round with a diameter of half the thickness of the board, with a smooth curve connecting the round edge to the widest point.

I did that to an old CB by simply adding 3M high strength Marine Filler and sanding it into the kind of shape. It's not a perfect leading edge profile, but improves on the factory design which (at least for my DS1) was more like a trapezoid (for each half or the CB, see diagram in my gallery).

In your case, I would figure out a layup schedule of one or two layers of glass tape - different widths, and then get the final shape with an epoxy-based fairing compound, like QuickFair. That'll do three things:

1. Strengthen the CB
2. Make the edge watertight
3. Improve the shape of the leading edge (bonus)

So far, you would have invested in a bit more glass and epoxy than strictly required to close the gaps, but should still spent way less than for a new board.

Now, to complete the process, I would add a bit of "tail wedge" to the aft edge. Put a single layer of glass tape along the aft edge, so it extends 1" or so beyond. Do this on top and bottom half of the CB (as it's lying flat). The two layers of tape will connect 1/2" to 3/4" behind the old edge of the CB, leaving a hollow channel. Fill that with thickened epoxy. (If you have some boards wrapped in Saran wrap, you can use them as clamps to give this "wedge" a proper support and shape as it cures).

Afterwards, you cut and sand off from the rear until the wedge terminates in a nice 1/8" (or a bit narrower) straight edge. Use fairing compound to smooth out any rough spots and the transition where the tape ends on the CB. Now you have a more efficient trailing edge to your board (and it will be watertight, plus a bit stronger).

I did something similar by just shaping such a "wedge" with high-strength filler, but my CB was structurally sound. There was a noticeable gain from my efforts - where the CB had "hummed" earlier (due to shedding vortices anytime I got to higher speeds), it is now quiet at the same speeds.

Because you should reinforce the edges of your CB anyway, you don't have to do that much more work improving the shape of it incrementally. And the added work is just in putting the reinforcements on more strategically and using a bit more QuickFair than you would have otherwise.

[hectoretc]

Thanks Green-Lake, as long as I'm working with this, do you have an opinion about replacing the fiberglass CB with an wood one? Last night I wasn't thinking about much, and the question sort of popped into my head, why not just make a whole new one? I have a fair amount of wood working equipment and it would not be difficult to reproduce the original shape (plus your suggested changes) into a wood board, and then fiberglass it for waterproofing.
Any thoughts or opinons on that change of direction?

[GreenLake]

Hector,

most of the work seems to always be the final surface treatment, sanding, fairing, painting, polishing. This is true, even if you don't want to carry out the work to racing standards.

Because of that, I'll estimate that the additional amount of time&effort for a rebuild is going to be tolerable. I doubt that a rebuild (overall) would take you more than double the time for a repair.

So, the answer is, yes, a rebuild is feasible. You'll want to do a bit of research first. Others have built centerboards and written about it. From the selection of the wood, how to laminate strips, best techniques to rout, saw or sand it into a profile, where to add additional reinforcements etc.

One key difference to the repair project: if you do build a new CB, you should definitely give it a "real" profile (not just the "quick fix" I wrote about, which is appropriate only if you must work from an existing board).

I recently built a rudder, which is both smaller and more complex project than a CB. While I don't claim that my efforts are state of the art, you can read about them in this thread.

What I would do differently: I would use a different paint, perhaps WR-LPU from System Three, or a two-part PU. The one I used is too soft. For a CB, I would add strategic reinforcements. I would heavily reinforce the leading edge (extra layer of glass tape) because you will hit something with it, sooner or later (I did with my rudder, and touching up a rudder is so much easier in comparison). You need to plan for such extra layers of glass when you cut your blank, because you want the final profile to come out right.

(Another detail: you may want to cut off the tip and glue it back on, to provide a break in the capillaries, so any damage from grounding doesn't result in water being sucked up across the entire length of the board.)

I would also add reinforcement along the midline. One source suggests routing a shallow channel on both sides and adding strips of fiberglass there (roving, so all fibers are aligned) or even carbon (which, however, would render the CB not class-legal). As I wrote in my previous post, the CB should be designed to be strong enough that you can stand on it, probably stronger.

You'd need to think about reinforcing the place where CB axle intersects, as well as the other elements of the CB raising / lowering mechanism (different on a DSII, so I can't help you there).

Finally, if you are interested in making your CB class legal, the fine print (dimensions) are found in Chapter 3 of the DS Handbook.

If you enjoy woodworking and puzzling out things, this could be a fun winter project.

(PS: If I were to do a CB, I would probably not start with plywood like I did for my rudder. I think the result would be too heavy.)

[hectoretc]

Thanks for the link... I actually had read that posting before when I first found this forum, because my poor beatup boat didn't come with a rudder either. I'd looked at your referenced posting with interest. I'd forgotten about that, but I'll bet that might be what seeded the wood centerboard idea in my head.
In the meantime, I'd missed out on what appeared to be a full rudder assembly on ebay by just a few dollars (couldn't be there to finish it out) so as a consultation prize I purchased a wood rudder blade that is pretty close to the specs (not too close, but pretty close) called for in the DS manual, and I've been staring at it since trying to visualize how I'm going to build the upper unit. I've just printed your drawing, and tonight I'll lay it beside my new blade and see what lines up with what...
Very good timing (yet again) on your post... Thanks!

[GreenLake]

On the rudder head, one thing I didn't get right is the back of it. It's too wide, so the tiller doesn't lie flat against the rudder blade when folded back. No need for you to repeat that mistake.

[K.C. Walker]

Hector,

I vote for a new board. I think you'll have a much improved board over the original. The original hollow boards have 2 chambers with a rib running down the center. A lot of them get leaks and in northern climates trapped water can freeze and burst the seams, not unlikely in this case I would think. You may have damage that you are not even aware of and would be very difficult to repair.

Be aware that if you build a wood core centerboard and get a ding large enough to let water into the wood it will swell up. If you board fits the centerboard trunk too closely and it swells up it's going to jam, so leave some clearance. Take precautions in building your centerboard to minimize the risk, like glue up strips with epoxy as "watertight bulkheads". When I was contemplating doing this I was thinking that I would use epoxy/glass filler for the leading edge and the tip as sort of sacrificial material in case I hit something.

If you repair your old board you'll still have a crappy board and it's going to be some amount of work. Making a new board in my opinion would be much more satisfying, if you have the woodworking experience, because you will end up with a really nice board and the boat will sail more efficiently.

[GreenLake]

+1 to what K.C. says.

Plus, with fall coming, you have all the time in the world (well almost) to get this right w/o missing out on a season. For epoxy work you do need a heated work-space. That stuff works best above 65F (even if some epoxies will cure below that).

[hectoretc]

Thanks for the help, greatly - greatly appreciated... this is a good forum for new owners of old boats. Everyone is very helpful.

[dbk0630]

I came across this write-up/article a while back in the DS pdf archives and thought it had a lot of sage advice that might/could prove useful when I got around to building my own replacement cb... something I hope to do this winter as well.

http://www.daysailer.org/pdf/qtr_buildcb.pdf

[talbot]

I had the same problem and forked over the money for a new board. It was solid, thinner, and considerably heavier than the original. Expensive, like $550, from D&R Marine.

I understand that there was a whole generation of O'Day boards with funky interiors. I even have an old circular describing how you should have a hole drilled in the aft edge of your board to let the water drain out. D&R says to ignore that with new boards.

[hectoretc]

Greetings all,
Waking up this thread again to ask a question that had slipped past me (actually two).
I've seen and read lots of examples where the rasing and lower cables come through the front of the CB housing and then through a number of blocks back through the cuddy wall to the cams or cleats depending...
My cable for raising the centerboard seems to appear at the expected spot on the forward end of the cb housing in the cuddy, but the lowering cable exits the cb housing on top about 2/3 of the way back. This is fine for me as it removes one less trip over target from the cuddy, but just wondering if that tidbit is a suprise to anyone? I've never seen it referenced in that location.

But the reason for my post is, I've also seen several references to a "fix" or update to the centerboard cables paths to prevent water leakage into the bilge. How would I know if I need, or if my boat has the fix or update? Short of putting it in the water and periodically checking for water to appear in the bilge, how does one know?
Any drydock suggestions would be appreciate.
Thanks,

[TIM WEBB]

The DS2 CB downhaul normally exits the top of the CB trunk just forward of the cuddy bulkhead. Do you see any evidence that it might have been there? Sounds like maybe a PO moved it further aft?

The DS2 CB uphaul is notorious for being a problem, or more specifically, the grommet that the cable runs through did not always completely seal the void between the inside of the CB trunk and the exit point on the forward edge of the trunk in the cuddy, thereby allowing water ingress into the bilge. This is a fairly easy thing to fix, involving some common plumbing fixtures. It's been described elsewhere on this site, as well as in Roger Conrad's DS2 book ...

[hectoretc]

Thanks Tim,
I have looked and neither do I see any evidence what so ever that the CB downhaul line ever led into the cuddy, nor the passage hole that would bring the line back out.



This is one of the "Welcome home" shots from when I first brought the DSII home this summer. I literally walked circles around the boat snaping digital photos almost continuously. It has given me a good record in my computer of what is where for these kinds of discussions. Note the exceptional clean appearance (ugh!!!) but that's for a different post.

You can see where the centerboard downhaul line exits the CB housing on top, immediately behind the jib cams (I assume that's what those are). The downhaul line isn't routed correctly here,



as it should go back to the block, and then forward to the tie off cleat.
The closer shot makes it look like a fairly professional installation of a "through the surface" block (I'm sure there's a sailing name for it... I think I'm doing well calling it a block instead of a pulley).
As referenced previously in this posting, this all had started from my careening the boat to check to insure there was in fact a centerboard (at all) and that it was attached to the necessary cables, which is when I found the cracked leading edge.

The uphaul/downhaul line is a single wire cable, bonded to a single point at the top of the centerboard so the position of the up/downhauls makes mechanical sense in that respect. I wouldn't mind at all doing another retrofit to get the uphaul line on top as well to solve the leak question once and for all as well as clearing the entry/floor of the cuddy of blocks and lines. Always has seemed like a bizzare place to put them, but I guess functionality has to take priority over asthetics.

Thanks again for your thoughts...

[talbot]

Looks like a standard factory downhaul to me. I think that's the original system. It's what I have on my 1973 DS II. When I owned a '79, both lines were inside the cuddy. I would agree this this is a "drier" system that the more recent one. I would not change it.

I did modify mine with cam cleats on the aft edges of the CB trunk, routing both uphaul and downhaul lines so a person sailing solo can haul in or release either from a position at the helm. Both lines have 2:1 purchase. (I guess that's 4:1 for the uphaul, because that line already has a 2:1 inside the cuddy.)

By the way, the "notorious" uphaul line on my older boat did not have the most serious problem with this system, which is that the filler between in hull and liner falls out, allowing water from the trunk into the bilge. The older boat had very little space between the glass laminates. Hopefully, yours is the same way. I did replace the plastic through-hull with a steel-lined fitting. That put a stop to the CB uphaul cable sawing into the hull liner.