View Full Version : Water-tight plank-on-frame at launch
06-20-2011, 06:36 PM
I have a traditionally built plank-on-frame boat using white cedar plank over white oak frames. It's 14' LOA and I usually launch it in the spring in a lake. I leave it in the water but partially beached for about a day or so to let it swell-up. It is then bailed out and is fine for the season.
This year I want to put the boat on my mooring. The opportunity to beach it for a day doesn't exist. I have a solar bilge pump but I believe the battery will die before the boat becomes water tight. Taking the boat to a lake for the day is not long enough as you really need a good 24 hours in the drink.
One thought is to fill the boat up with water while it is on the trailer and keep filling it until the water no longer leaks out and then assume it is water-tight. The boat was recaulked this spring with seam compound and bottom paint. This was done in previous years and it still took 24 hours for the boat to adequately swell-up.
Is 24 hours typically needed for a boat to swell-up or should I assume the boat was poorly constructed?
Thanks for any tips or ideas on this.
06-20-2011, 06:57 PM
More will come to your aid but be very careful adding water while on land! The force of the water usually pushes in against the frames but if you fill it on land the weight will be trying to pull the fastener heads through the soft cedar planks. Perhaps a lawn sprinkler inside the boat with the drain plug open could get you most of the way there. Then your bilge pump would be up to the job. Another trick I have heard about is to use soaked burlap against the planking to help it swell. Just spray down the burlap (or old towels) now and then and you should get pretty close.
If it stays mostly tight over a whole season then I would say it is NOT poorly constructed. Just wooden. A very different thing.
06-20-2011, 07:13 PM
Great advice - thanks. I think I will use the wet towels and just spray them every few hours to keep them wet.
06-20-2011, 09:21 PM
Let her sink at the mooring if she wants to. It does not hurt her.
06-20-2011, 09:32 PM
Cover her with a tarp, pull the drain plug and set one or two lawn sprinklers inside for a few days.
06-20-2011, 09:48 PM
Under no circumstances should you fill a beached or trailered boat with water. The stresses on frames and fasteners resulting from a full, beached boat are the exact opposite of what the structure was designed to withstand.
But allowing her to sink at a mooring will do no harm whatsoever. All you'll have to do after a few days is pump her out. In fact, if the boat is allowed to sink/fill with rainwater so the water level is the same inside as out, you can even let them freeze in place all winter without any major harm. I do it every year with several work boats.
06-21-2011, 07:17 AM
Place the boat and trailer over dirt or grass in the shade and set up a hose with pin holes to sprinkle the bottom of the boat and keep the grass/dirt wet. Maybe even tape a plastic skirt around the boat hanging from the sheer. Place burlap or other cloths inside the hull and keep them wet. Keep a canvas cover over the boat to minimize the wind's drying effects. Do this for a week and she should be well along in the tightening up process.
This is from an article in WoodenBoat, I forget the issue.
06-21-2011, 07:20 AM
On occasions I have filpped small skiffs and placed them on bare ground thats been well satuated. You can use plywood at the ends thats touching or even block the boat up inside so that it suspends across the ground as close as you can get it. I countinue to wet the ground usually from a trickle water hose when I think things are drying out, placed under readily avaliable access along the sides. I also apply old cotton towels, a couple of layers on the bottom or even burlap bags layered and wet them. Usually cedar will swell in about two days if you maintain a wet surrounding on both sides.
06-21-2011, 07:27 AM
My two cents worth -
Larry suggests using (masking?) tape over the seams at launch. It stays on long enough to slow the ingress of water until the planks swell tight.
You don't want the stuff coming off and fouling the lake so run the tape in one long run on each seam and up over the transom and secured inside the boat. Then if it comes off the underside it'll still be attached to the boat and you can collect it. If it doesn't come off, beach the boat and peel it off.
What do others think of this idea?
06-21-2011, 07:32 AM
You absolutely should let her sit swamped or sunk in shallow water for a bit. The leaking enough to sink her is telling you she's not ready to sail yet. Carvel hulls need to be a structure under compression strain plank against plank or else all the hull stresses land on the fastenings which then just enlarge their holes and move more rapidly to failure. But you can't make a boat that tight dry and expect her not to explode when she takes up. The art of caulking is enough that she's tight but neither over nor under when swollen.
If you rig or power a wooden carvel planked conventional boat that's been designed to swell this way (not all forms of what looks like carvel planking require this, especially in small row boats) and you put the sail or moter to her, you just wring the fastenings and shorten her life.
06-21-2011, 08:01 AM
My only doubt about swelling her on the mooring is wakes or waves. I think I remember Atkins (or Culler?) suggesting that the surging water in a full boat might lift the thwarts. That said, I swelled a pine skiff in a small lake once just letting it swamp. But there were no motor boats there.
06-21-2011, 09:30 AM
johngsandusky is correct about wave surge. I've seen it take a deck right off, though that happened during a poorly concieved tow but the principle is the same. The three safest ways are in a very calm spot, well down on the bottom where the wave surge does not reach, or in a cradle that wets her to the waterline or a bit below that out twice a day with the tides. With that last method the bilge plug needs to be out till the real launch.
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