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I have had a leak in the centerboard cap of my Lapwing since I got it. External caulking was not effective so I decided to seal it internally with epoxy before my first spring sail. In the process, I realized the centerboard needed work. It was worn down to bare wood in one place caused by a slight warp. After repairing and reinstalling the centerboard I began cleaning the inside of the boat. This is when I was reminded of the bubble I had seen in the paint on the side of the centerboard trunk. Well it turned out to be covering rot. I have now uncovered about a square foot of damage in three separate areas on the trunk and my spring sailing is looking doubtful.

 

I suspect that replacing the whole trunk is beyond my skills. So I am considering stabilizing the areas with epoxy, adding scraps of fiberglass to the deeper parts, filling in with thickened epoxy and then sanding and painting. I should note that the trunk has epoxy and fiberglass in the inside but not on the outside. There is probably more rot near the base of the trunk behind the seam with the hull. I don't see how to get to this without ripping out the whole thing. Is this a viable plan? Any suggestions?

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I am guessing that after 0 replies in 2 days that my boat is doomed and nobody wants to tell me. So I will probably slap a little epoxy on the exposed parts and sail her until the centerboard trunk falls out. I might also scab an additional layer of plywood over the existing sides of the trunk hoping to extend the life of the boat a little longer.

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Yes, hard to advise without pictures. It's not that we don't want to help, but we need more to go on. Don't give up on your Lapwing!!!

Here's a suggestion. If the rot is not threatening a structural failure, use a product like "Git Rot". Here is the ad:

 

"BoatLIFE GIT-Rot penetrates rotted wood and restores it to its original strength. Pour or inject this unique 2 part liquid epoxy into rotten wood fibers. It saturates fibers via capillary action and cures overnight.

Git Rot cures into a resilient adhesive that arrests dry rot by bonding wood membranes together. The result is stronger than when the wood was new. Once cured, it can be sanded, painted, drilled, and fastened. Boatlife formulated it for compatibility with fiberglass resins, epoxy, and most sealants.

Intended for use on dried out, rotted, and weather wood, Git Rot is ideal for repairing stringers, roof rot, and transoms on both fiberglass and wood boats. Non-marine applications include window sashes, gutters, and other exterior repairs."

 

Follow the directions. Briefly, drill holes it the rot, inject the GIT-rot in the holes to saturate the rotten wood, fill the holes and paint. 

You could also thin your own epoxy and use it the same way, but using Git-rot will give you the advantage of a product that is ready to use and has instructions included.

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Here are the pictures of the damage. First picture, port side, is about 40 sq in. and looks the worst. The other two are on the starboard side. The middle picture damaged area is only about 10 sq. in. The last one is the biggest, about 50 sq. in. 

Thanks for the tip about Git-Rot. Will 16oz be enough? Online it was cheaper at Jamestown than West Marine.

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GetRot is simply a "rebadged" product and about worthless in this repair. Also don't beleive the advertising fluff on the lable, it's been proven wrong many times and they've been sued several times for this wording crap. Unfortumatly, this case needs to come out, which isn't as hard as you might think. Remove fasteners as you find them and cut it free. It might be easier to build a new case which doesn't absorb much in material. Simply put you've got too much case side damage, in the worst locations to consider packing it full of goo and hoping for the best. On the other hand you could pack it full of thickened goo and fabric, then bond a second layer of 1/4" plywood over the damaged areas. Wedge the inside of the slot with a protected bit of wood, so it doesn't ooze through to a difficult to get at location.

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I agree with PAR. The damage looks to be extensive enough to have undermined structural integrity. If not feeling confident about removing the entire case, I would at least treat the rot, soak it with diluted epoxy, then fill with a fibrous filler and put a new piece of 1/4 inch ply over the area and bond that to the old ply with the the paint removed from the bonding area. Be sure to saturate the inside of the new ply with epoxy before attaching. The rotted joint and the crack are concerning and could fail under pressure from the centerboard. My two cents worth.

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I hate to see this happen. The hull must have had water lying in it for a long time for the trunk side to rot like this. It makes me wonder if there is not more damage elsewhere. 

 

I am not a fan of Git Rot either. I would cut out the effected wood and splice in new wood. I do not think that the trunk needs to come out if what you show in the picture is all of the damage. If you are convinced that you cannot splice in new wood and the inside of the trunk is glassed, as recommended, you could scrape, grind out the bad wood and fill it back up with wood flour and cabosil  thickened epoxy and glass over the outside and it would be more than strong enough. This would take a delicate hand with the grinder as you could grind through glass in a second. I would remove the centerboard and and put a backing piece inside the trunk and wedged tight against the side of the trunk that you are working on. Tape some plastic to the backer so that it cannot get glued in place if some epoxy happens to work it's way through the glass on the inside of the trunk. If you are careful enough to remove the damaged ply down to the glass, it will not be very stiff and may dish or get wavy. You might remove the rot in strips, say 3 wide and fill it in with thickened epoxy before removing the next three inch strip. I would remove all of the damage part on one side and just put in a new piece of 6mm ply. You can butt joint the ply as long as you cover the butt joint with glass tape. It is also important to remove all of the rotten wood and go well beyond where you think that the rot ends or it will continue to rot on the other side of your repair.

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You mentioned that there was wear on the centerboard. If this is just from dragging on the bottom no problem. If this was from rubbing on the inside of the trunk then you probably have a matching amount of wear inside. Get a good light and see if you can see anything of the inside of the trunk. As Graham cautioned you might take a good poke all around the boat. There is a lot of willing expertise on the forum. If you have the time. I would bet you could do the repair.

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Two real keys to this sort of repair; first is to get all the rot out. Cut and grind until you're very sure you're back into good, solid wood. Second is the repair approuch. The down and dirty way would be to grind away the bad, replace withscabbed in wood, smooth with thickened goo and hope the transisions hold. A more robust method would add a small amount of weight (a few pounds), but the case sides would be much stiffer. Thi amounts to adding more 1/4" plywood over the case sides, reinforcing the repaired areas.

   Lastly, diluted epoxy isn't waterproof (not even close). It's usefulness is quite limited and in this regard, just not worth the bother and costs associated. On an old carvel with bashed seams, that have just been "reefed" out, there's a good arguement for penatrating epoxy, but on solid materal or plywood - zip. Essentially it's a very costly epoxy primer, for additional (neat) epoxy over coats. The net gain (using a penatrating epoxy under straight epoxy) is less then 2% improvement in peel strength. If the project lives or dies on this 2% gain, well go for it. Fo the vast majority of projects (99%+ of those here) absolutly no need for this stuff. No penatrating epoxy can change rot back into anything that resembles real wood.

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Hi RBA, I'm a real beginning builder compared to the guys who have answered your post.  I'm just getting close to completing my first stitch-n-glue boat, and not at all experienced in repair (yet).  Here's my view for what it's worth.   Doing a good job with the filling and patching also takes skills.  Also, I found that cutting and shaping small pieces of wood is only slightly less work than larger pieces.  So number of wooden pieces is probably a better way to judge the work than the size.    Of course, as you weigh things, only you can judge.  At any rate, the first step is going to be to get rid of all the rotten wood.  Then look at what's left and make a plan.

 

I'd also like to stress (Ha!) the mechanical importance of the centerboard trunk.  If you're sailing along, say beating to windward, the forces on the centerboard are about the same as the forces on the sail, and the trunk has to be strong enough to support it.  These forces also create torques that you balance by putting your body weight on the rail.  To gauge the strength that's needed, ask yourself if you'd be willing to stand on the centerboard if the boat was on it's side.  The real CB torque calculation involves ratios of mast length, beam and CB length in addition to body weight, but body weight gives you a convenient way to get a feeling for the strength that's needed for a light dinghy.

 

 

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After reading all this good advice all I should probably add is - Don't Panic!  Take it one step at a time and remember that if you mess anything up (like I frequently do) you can likely undo it with the judicious application of a sharp tool.  If you look at it as a big overhaul of a boat hull it may seem intimidating but if you think of it as cutting out a flat piece of wood and replacing it (and then doing it again until you're done) it might be less daunting.

Don't forget to come back here with pictures and questions.

And you thought nobody was listening :)

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If they can put a Sprint Cup car back together for next week's race, after plowing into a wall at 190 MPH, there's absolutely nothing that you can't fix or repair on your boat. Trust me and our fellow wood butchers, you got this . . . and under putty and some paint, no one is going to know a thing.

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On 4/26/2017 at 9:48 PM, Ken_Potts said:

After reading all this good advice all I should probably add is - Don't Panic!  Take it one step at a time and remember that if you mess anything up (like I frequently do) you can likely undo it with the judicious application of a sharp tool.  If you look at it as a big overhaul of a boat hull it may seem intimidating but if you think of it as cutting out a flat piece of wood and replacing it (and then doing it again until you're done) it might be less daunting.

Don't forget to come back here with pictures and questions.

And you thought nobody was listening :)

I'm probably the king of panicking and I second this advice. 

 

Trust me, if I can get most of the way through a boat build you can put in a new centerboard trunk.  

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I bought the Lapwing in 2012 and (with the exception of two) she has spent every night dry on a trailer mostly in a garage. I suspect that the centerboard trunk was not made of marine grade plywood.

 

I have pulled the centerboard, wrapped it in package tape and reinserted it to maintain the space. I am still scraping paint looking for more rot. Looks like I am going to have to cut away the taped seam between the centerboard trunk and hull. I am not sure what to do if the rot extends under the mizzen bulkhead.

 

After cutting out the bad wood I plan to fill in with 4mm Okoume, glass and epoxy which I have on hand. If that goes well, I will add a new layer of 4mm plywood on the outside of the trunk and and make a new taped seam between trunk and hull.

 

This is going to take a while. Thanks for all the comments.

 

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Thanks for the update. Good luck on the work. Photos and updates may help others deal with this problem or better yet avoid it.

 

Marine Plywood is not necessarily rot resistant. Okoume has almost no natural resistance to rot.

 

One of the keys to making plywood epoxy boats durable is keeping the water out.

 

Ideally any penetration through the plywood for a fastner or whatever should be drilled oversize and filled with epoxy then redrilled so the fastner is going through an epoxy bushing.

 

One very important place to do this is at the centerboard pin. The pin should be surrounded by an epoxy bushing 6mm or more thick so there is no way that water can get into the edge grain of the plywood. 

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I'm afraid that your Lapwing has had some serious issues in either building or maintenance in its earlier life.  Since you bought it in 2012 and it has not been stored in any exposure to the elements since then, it had a pretty short lifetime to incur all that damage.  Probably no more than 5 years and likely less than that.  Good plywood just doesn't go bad that fast even if it was only painted.  I'd venture that someone owes you an explanation. 

 

I'm the owner/builder of the original Lapwing which has been simply protected by a tarp cover for its life of a bit less than 10 years and it has no such problems at all.  Its very distressing to see this kind of damage on a S&G boat and even more-so on one so young. There is a ply/glass/epoxy Windmill sailboat sitting alongside Lapwing that has not had the level of protection as Lapwing and it does not have anything approaching this kind of damage although it is 24 years old. 

 

I think that at least a new DB trunk is in order

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I have uncovered rot all the way to the bottom of the trunk. It appears that all that is left in that area is one ply of the 3/8” plywood with the glass epoxy glued to it (very flexible). The hull seems okay. I don't think the inside of the trunk to hull joint has a layer of glass tape as I can see heads of screws going into the keel batten.

 

I'm over my head here. It is likely that most of the bottom edge of the centerboard trunk is as rotten as Hamlet's Denmark. It not likely that I can successfully clean out the space between the keel batten and the glass inside the trunk and slip in new wood (although the other side of the trunk would not have that problem). Anyway, this would put me back to a whole new centerboard trunk. Looks like that will require removing the thwarts, trunk cap, mizzen step and mid bulkhead just to get the trunk out. Anything else?

 

Still thinking about stripping and burning the hull, and starting on a new boat maybe a CS17 mkII

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