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  1. #1
    Join Date
    Feb 2011
    Location
    Ottawa, Canada
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    55

    Default repairing strake

    I have posted about this boat on Woodenboat form a couple of times and have had some very useful responses but I thought I would see what advice I might get here as well. There is no such thing as too much advice.

    The boat was built in Norway. It is clinker and I doubt it has spent all that much time in the water but it has been mistreated in a bad way and I think it was dropped at some point before I got it.

    I have managed to get the transom repsired but there is an issue with the starboard garstrake. It has a nasty split in it that will have to addressed and I plan to doing that this spring. The corresponding strake is virtually flat but the broken one has been deformed in that it is pushed up and is now convex when viewed from inside the boat.

    My plan is to clean out the split as best I can and to fill the split with epoxy and then to flatten the whole thing by running a couple of pieces of oak across the whole shooting match, which I hope will get things back more or less flat. I was thinking of putting the oak in before I actually glued and letting things flatten out for a while before gluing but I think the down side of that plan would be that I would close up the split so that I would not be able to get the epoxy in properly.

    Maybe I would be better off to flatten, rout out a bit of wood where the split is and glue in a dutchman.

    Opinions will be appreciated.

    The wife seems to be getting increasingly excited with the passage of time and I have to try to do what I can to get the boat out of my garage and up to the summer place before too long.

    I will try to attach a thumbnail but I am not sure how much success I will have.

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  3. #2
    Join Date
    Feb 2008
    Location
    Eustis, FL, USA
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    Default

    Generally it's best to remove the bad potions of a plank, then fill it with plastic or a Dutchman.

    The garboard is the most heavily taxed plank on the boat and often is the first requiring replacement. Frames also need to be inspected, as they too usually experience damage if she was dropped or run aground.

    What type of planking, what type of fastening system and can you post some photos of the damage, both inside and out?

  4. #3
    Join Date
    Feb 2011
    Location
    Ottawa, Canada
    Posts
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    Default

    PAR,

    Thanks for the response. The more I think about it, the better the dutchman plan seems to be. I am not great at photos but I am attaching a few pictures of the damange.

    The boat is pretty typical of construction in the part of the world where it was built. The strakes are mahogany secured by rivets. There is not all that much in the frame department and I think they are likely oak of some sort. They are quite substantial and there appears to be no damage.

    When I had the boat given to me, there were a lot of issues. It had been sitting here and there for years and the finish was pretty well shot. The transom was broken and most of the fastners holdng the strakes had snapped off about half an inch below the level of the transom itself. That was a real pain to fix. The crack and a break in the starboard gunwhale, or whatever it is called, were the other major issues apart from general cosmetics.

    There does not appear to be any rot on the boat, at least I have still to find it. I think it spent very little time in the water.

    What sort material should I use for the dutchman? I was thinking plywood because it is not apt to split.

  5. #4
    Join Date
    Feb 2008
    Location
    Eustis, FL, USA
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    Default

    I'm seeing a few things there that make me think you should scab in a short section of plank, rather then a Dutchman. The split looks to be over or just past a scarf, which is a common location for this to occur. If you scarf in a length of plywood there, you'll eliminate this from happening again in this particular location.

    You also look like you need some refastening and the garboard is almost always the first place this needs to happen.

    I see two possable quick fixes: the first is a really easy one, but you'll need to ease the compression causing the cupping on the plank. This compression is normal and doesn't hurt the boat when the plank is sound, but if the plank is damaged, then it can't act as a solid structural element and things move. With braces, jacks and other forms of "persuasion", flatten out the plank so it it looks like it's suppose to. Drill a 1/4" hole at the very end of the split (both ends). Then using a laminate trimmer with a 1/4" straight bit and a guide, plow out the split, connecting the dots so to speak. This will completely releave the pressures within the plank and don't be surprised if the 1/4" wide slot you've just made closes down a bit after you're through (this is alright). Next taper the opening on both sides and fill the 1/4" wide slot with thickened epoxy, sand flush and paint. This is a simple, easy repair that will work, assuming there aren't any additional internal stresses within the plank (not an unusual thing).

    The second is a Dutchman, which is quite similar to the above repair, except you make a bigger hole and fill it with wood, that's glued in place (epoxy again). The Dutchman can be done from both sides, using a double ended scarf, and if you use mahogany or meranti plywood, you'll hide the repair quite well (assuming good fits). It's a little more fiddly work, but you can preserve the appearance with a wooden reapir, which is especially nice if you want a bright finish.

    I'd also consider refastening. Drill the heads off every other rivet and remove that rivet. Install a new rivet and cinch it down good. When you've done a length of seam about 3 or 4 feet long, you can go back and replace the ones you skipped on the first pass. This is the easiest way to bring new life to an old lapstrake. It's not hard work, a tad tedious, but not hard and the boat will be tight again, which is what is required for lapstrake planking, to keep it from self destructing (laps rub against each other and eat each other up, if fasteners are loose).

    I can't impress enough, how important tight laps are on this type of build. The planks will literally chew themselves to paper, if the fasteners don't keep them tight. Both clenched and riveted boats are notorious for doing this, so consider renewing the fasteners in high stress areas, such as the garboards, the turn of the bilge and the sheer strake. If you let this issue (loose fasteners) go for very long, the damage increases at an exponential rate. This is the most common cause of death in lapstrake builds.

    Lets see some wide shots of your project, she looks to be a pretty thing, but it's hard to tell with these close ups of her spots of acme.

  6. #5
    Join Date
    Feb 2011
    Location
    Ottawa, Canada
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    Default

    Thanks again.

    The epoxy sounds simple enough, as long as it will work. The other suggestion is more appealing although it is more work. Appearance is not that much of an issue in that location since it won't be seen. The floorboards will cover it from the inside and, of course, it is below the waterline.

    I had not considered the refastening possibility. Everything seems tight enough but it is hard to tell just by looking. It certainly would be a tedious process, to say the least. I would imagine I will have a better idea once I get it in the water for the first time. If it does not take up, there is clearly a problem. I would imagine the original style rivets are likely still available.

    The main work so far has been the transom. When I got the boat that was a pretty bad area. You can see the general situation from the picture. The transom itself was split completely across and warped as well. I got the warp pretty much under control and repaired the split.

    I hadn't realized just how serious the garstake situation was until I started cleaning up the interior. At that time it became pretty clear what had happened. I first saw the boat when the first owner still had it. It was sitting on top of a woodpile in his garage. I don't recall the transom damage at time, but it was quite a while ago and maybe I just didn't notice it. I rather suspect it may have fallen off the woodpile, or maybe the stress of sitting on the woodpile for a few years was enough to the do damage. The strakes are not all that thick although they are pretty wide, and there is not much in the way of frames so I guess it all a mystery that will never be solved.

    I am attaching a few more shots of the boat. I guess the first project will be to try to get the warp out of the strake and then address the actual repair.

  7. #6
    Join Date
    Mar 2012
    Location
    Victoria BC Canada
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    Hi Bob,
    I would agree with Par but I say go the dutchman route. Cutting the slot is the biggest part of the job and you will need the slot to follow a fair line. This may require tacking a guide batten to the planking. The 1/4" slot made with a laminate trimmer is big enough. I don't taper the slot but cut it just about 1/16" shy of the full plank thickness. This gives the spline you insert a backing. I would use a softwood spline to allow for a little compression when the planks start to swell. Where you are White cedar is a good choice.
    A possible alternative to replacing the rivets is to "harden them up" with a few raps with hammer and iron.

  8. #7
    Join Date
    Feb 2011
    Location
    Ottawa, Canada
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    Default

    Hi Mark,

    White cedar sounds like a good choice. My only concern is that we are looking at a strake that is only a half inch thick. Clearly the dutchman can't be more that 7/16 if I don't want it sitting proud of the inside of the strake. This is not a problem since the area is covered by the floorboards. The problem is that the strake is somewhat distorted. The opposing strake is dead flat but the damaged one is convex by, I would imagine, a quarter inch. I would like to get things flatter before the dutchman goes in. The present plan is to blow a much debris out the the crack as I can using a compressor and the to flatten things out by sandwiching it between two or three pieces of 3/4 oak. This would require drilling a few holes but that can easily be filled later. I think the trick is to persuade the strake to stay flat once the oak is removed. Maybe wetting it or using steam would work. If it won't flatten out, there are problems in my mind.

    I can only speculate as to how the damage took place in the first place. I think the boat must have taken a fall, landed on something that split the strake, and was left sitting in that position for quite a while. I saw it a couple of times when the original owner still had it and it was not being very well cared for. It was inside but that is about the only positive thing that can be said.

  9. #8
    Join Date
    Feb 2008
    Location
    Eustis, FL, USA
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    Default

    The professional would remove the fasteners on that strake (well fore and aft of the damage), which with some luck would "release" the strains on it causing the cupping. This includes "popping" open the scarf just aft of the damage and prying the damaged portion of the plank down to permit access. The cost effective thing would then be to cut off the bad portion of the plank, scarf in a new piece (full plank width), bevel the lap, then refasten, using the old fastener holes in the adjacent planks. You'd have a couple of scarfs within a few feet of each other, but other wise the repair would be seamless. If the scarf was epoxied in place, then under paint, no one would know you've "been in there".

    Of course this is more difficult to do than plowing out a groove for epoxy filler or fitting a small Dutchman. On the other hand it does restore the complete integrity of the plank end, which is why the professional would choose this route. The Dutchman or epoxied groove doesn't address any other unseen internal defects or stresses, that may exist within the damaged area. Releasing the plank end and cutting it off, insures they can return at a later date.

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