Restoring a Huon Pine dinghy

[grantandrews]

I'm currently restoring a clinker built Huon Pine dinghy, it's sound but has opened up considerably. I have scraped it back and pulled out as much old caulk I can, and am after advice as to whether to sink the boat in fresh or salt water, how long soaking would be enough and after that what would be the best caulking to use. I would rather not use a silicon type product, rather a traditional method.

[labr@]

Welcome to the forum Grant.

I don't know much about this kind of stuff but am wondering why you would not caulk while in the dry opened condition so that any moisture absorption would tighten the joints. Is it a case of too much pressure would cause planks to pop off?

By the way, we like photos too :).

[grantandrews]

Thanks for that. As to caulking before or after, good question. I don't know but would worry about the expansion. Also, can't post pictures as I can't find the "photo and album link", it's not under 'quick link. This mouse ain't too good in a maze!'

[labr@]

Sounds as if you want to link to photos that are already somewhere on the net. You can also attach photos direct to your post.

There are 2 threads on adding photos in the help section of the forums: "Forums info, help , discussion and feedback"

Here is a direct link to one of them:

http://www.woodworkforums.com/f36/uploading-photos-attachments-168803

[Kingfisher]

I'm not sure how you do it, but you may get better exposure by moving this thread to the "Boat Building / Repairing" forum.
Cheers, Mark

[grantandrews]

I have moved my post over to "Classic Boat Restoration" Thanks for the advice!

[PAR]

You generally don't "re-caulk" lapstrake boats. There's three types of lapstrakes builds: the two traditional types are naked seams (laps) and sealed laps (polysulfide). Naked seams are just as it sounds, there's nothing but raw wood on the lap faying surfaces. It's this raw wood to raw wood contact, that permits the faces to swell and seal against each other. A sealed seam uses a goo, typically polysulfide (the same stuff they use in teak deck seams). The third type is a glued lapstrake, which is a modern version and the faying surfaces are epoxied together. No lap fasteners are used with this method and because the planks are married to each other with epoxy, you can skip most of the internal structure too (frames, stringers, floors, etc.). Because your boat has fasteners, it's a traditional lapstrake and because it had sealant, it's probably a sealed seam build. The real question is, was it actually a sealed seam build or did someone at some point try to fix leaks with a goo in a tube approach.

A few years back I posted (long winded thing if memory serves) a piece about restoring lap strakes.

You can scab in something on that plank, but it's probably not going to hold long, especially if it's a solid timber plank and not plywood. Planking on a traditional build (carvel, clinker, whatever) is a consumable item, just like an air filter on your car. Once it done, it's done and that particular plank is done and should be replaced. It's not as hard as you might think, once you get your head around the issues you'll face. The hard part is getting the old plank out fairly cleanly, so you can use it as a template for it's replacement. This usually boils down to how bad the frames and fasteners are. Cutting the fasteners is easy, just hacksaw through the roves or clenches. Wedge open the seam, typically in the middle of the boat and using a fine tooth blade (no handle) insert it into the seam and slide it to a clench or rove. A few quick hand strokes will cut right through it and you move on the the next one. Working out from the center is best, getting to the ends about at the same time, the plank will be all but falling out by itself, when you release the hood end fasteners (usually screws). Now you have a plank that can be placed on a workbench, repaired or copied and replaced.

I'm not sure what the story is with that particular plank, but most often these failures (other than impacts) are from fasteners getting loose, letting in moisture, which causes havoc with the frames, planking holes and the fasteners themselves. Replacing the plank isn't good enough, you have to fix the structure (frames, floors, stringers, fasteners, etc.) too. This is because lap strakes like to "move", which means every contact point (clench to plank, plank to frame, stringer to frame, etc.) wiggles just a bit, as the boat transmits loads underway. In time, the fastener holes open a wee amount and this lets in moisture and a vicious spiral begins, the holes get bigger, the fasteners lose their grip, move movement grinds the faying surfaces within the laps, etc.

With luck, the rest of the planking just needs some new fasteners and a Dutchman or plank replacement on that beat plank. The well built traditional lapstrake will use polysulfide as a sealant on the laps. A trailer borne boat can live with polyurethane, though this doesn't like continuous emersion (more than a week or two). All the major manufactures started using this stuff in the early 60's and it helped tremendously increase the lifespan of a lap strake. Lastly, you'll want the hull dry as a bone for repairs and if the seams have sealant, prolonged soaking shouldn't be necessary. If it does need to "soak up" then you have issues elsewhere and should address them too. If there isn't sealant used in the laps, then yeah, she'll need to soak and it doesn't matter if fresh or salt. This is the reason the manufacturer's started using polysulfide in the laps, to remove this need to let 'em soak up come spring commissioning time. Simply put, a tight, sealed lap build doesn't need to soak and if it does, there's a problem. On the other hand, if there's no sealant in the laps, yeah it sure will need to suck up for a day or two.