LOOKING AHEAD: CLYDE AND I MAKE PLANKING PLAN

[bob mitchell]

      One of the areas that concerns me is replanking the areas that I have been repairing, so naturally I have been discussing that with Clyde (actually I discuss about everything with him). So this forum is an attempt to summerize the information and ideas that we have come up with. Clyde has further presented some historical information about how Newporters were originally planked.

       A couple of factors had to be considered as we made a plan. The first was that the very ends of the frames in the bow area were rotten. In each bay between those frames is a "cheek" piece that adds additional fastening for the planking (3/4" plywood in the Newporter's case). These were shot as well. In the photo below you can see four cheek blocks. The doubled frame with plywood is frame #4. Right below them, not visible to barely visible, covered by fiberglass, is where the rabbet would be.

So to kill two birds with one stone we decided to cut back the ends of the frames, and instead of cutting individual cheek pieces, we would cut one long piece (two at the most) that would be strongly attached to the lower forefoot for most of it length, serving as a continuous cheek as well as a fastening point for the cut off frames. If that is to much to visualize here is a graphic from Clyde, with the original on the left and new on the right. The next photo is looking down the new lower forefoot with the frames cutoff. The new continuous cheek will go in between. One extra positive for the new cheek is that it will span the lower/upper forefeet junction with one one each side.

"On "Old and New Rabbets" note that the new cheek block has a beveled top.  This is to do away with a possible water trap.  Though you are building so as to prevent water from entering the boat you still need to build with an eye on the probability that water will get in, so allow for quick drainage to the bilge pump.  One such block to a side is likely impossible, so, where needed, butt them between the frames with a close fit and glue well to prevent water penetration."

The rabbet can be seen as the grove in the upper stem piece that has not been removed. The rabbet is the grove where the planking intersects, in this case, the forefoot. You can kind of visualize that if you extended the outside surface of the frame downward like a piece of plywood planking would do, you would intersect the forefoot at the rabbet. In fact, that is probably the main technique I will use to locate and cut the rabbet, as well as measurements off the old forefoot. Clyde describes it as follows.

       " Extend that line from the outside surface of the frame down to the stem using a short piece (5 or 6 inches long) of ¾ inch plywood no wider that the thickness of the frames, .   The angle of the piece against the stem is the angle of the rabbet; the corner that touches the stem (inside surface of the plywood piece) is the bearding line.  If you can hold that piece in place (1” brads should hold it, heads driven flush) place another piece like it on top and slide that piece down to the stem.  The corner will touch the stem at the “rabbet line.”  Mark the stem at both places where the inside corner of the “tools” touch the stem.  With both the bearding line and the rabbet line marked below each frame, spring a batten from point to point for the length of the rabbet on each (separately) and scribe a line connecting each point as marked.  This will give you a long sweet curving line for both the bearding line and the rabbet line.  The angle formed by the lower end of the frames will give you the angle of the cut at each frame.  If the angle changes from frame to frame the angle must change as you proceed from frame to frame while cutting the rabbet.  The angle formed at the “middle rabbet” is 90 degrees for the full length of the rabbet to match the 90 degree edge of the plywood planking.

 

        A second factor to consider is that the bow is an area of compound bending for the 3/4" plywood planking, adding great stress to the fasteners.  "This area has a double curve in it, adding much stress to the 3/4” sheet (the first curve being the wrapping from a wide section of the boat to a "point" at the stem; the second curve is vertical—the frames have a curve sawn in)." Actually, to really appreciate the stresses and how they were overcome in planking a Newporter, it is worth reading a brief description from Clyde. "

We clamped the planks on by drilling holes through the planks through which bolts were passed, and using full 2 x 2’s (or larger, white oak) long enough to span two frames, clamped the whole plank (about 40’ long) in place.  The frames, inside clamps, and chines were outlined with pencil inside.  Then the aft end was released and swung away from the framing and pilot holes for boatnails drilled (at least at top and bottom of each frame so a line could be drawn outside to locate the frame, or some other way of marking the location of the frames was used).  This should be done from the after end to frame 18 or 19.  Then glue was applied to frames and plank (between pencil lines showing the frames) and reclamped in place.  Nails were then driven starting at frame 21 or 22 and going aft.  Frames 18-20 are not yet glued but are drilled so when the forward end is swung out from the framing the next area to be drilled will be far enough away from the framing to allow the work to be done.  Then the forward end was glued and reclamped as before, and nailed going from the middle of the boat forward.  Ten or twelve clamps were all that were needed per side.  More were put in on the bow to get that double curve pulled in.  At least that’s how I remember things; and how I now would figure it’s to be done." Below is an early construction photo showing some of the bolts used to pull the bow and other areas in.

  

     So considering the stresses in the bow area, and the fact that it would be tough to make scarf joints into the old planking, we decided to use two sheets of 3/8", which would form to the curves much easier, and once the epoxy between them dried, they would have the curve laminated in. To join it to the old plywood planking I will rout the 3/4" old to 3/8" thickness for about 6", which will be overlapped by the outside sheet of 3/8". With the planking off in the repair areas it will be easy to add additional frames to make sure the joints are backed up by framing. Alternatively "Adding frames behind your overlap will work well.  In fact, better than any way I can think of.  I would have the first layer stop at the middle of a present frame and butt the next piece to it.  You may have to scribe a line and cut to it so that the first edge will be in the middle of the frame.  Then the next piece can be temporarily fastened next to the first and the shape of the first piece scribed and cut so that they mate.  It may take more plywood, but you can do the same with the top layer one frame removed from the first.  You will have about 12 inches of overlap that way, but no extra frame to put in.  Check in your book concerning scribing with a compass and holding the pencil point in the proper position so the two edges match when you bring them together. These are roughed in details subject to change if new factors emerge.

        One factor that I really worried about was the fitting of the new plywood planking. I had scribed lines often, but never a curved surface. Clyde had a ready answer.

     "Planking pattern: We had two almost full sized (about 1 inch short on all sides) 1/4" "planks" (1 ea, side and bottom) that was nailed in approximate position, and a scribing tool made of sheet metal (I'll picture that on the attachment that I'll send when I get to the computer on which it resides).  Basically, it is about 6" long, 1" wide, one end turned sharply up (about an inch) and the other end turned sharply down (just a wee hair under 1/4" or whatever thickness your pattern is).  You place the scribing tool (It had a shorter name than that) so the short end hooks down over the edge of the pattern, push it out so the short hook end is on where you want the edge of the plank to be, hold the tool in that position and scribe a line around the three sides of the tool on the pattern.  A lot of words to do what you probably have already figured out.  But I continue.  When you do all the marking on the pattern that suits your fancy, remove the pattern and lay it over the plank blank, nail or clamp (clamping is best--no holes) the pattern to plank, hold the tool in each of the U shaped marks and scribe a short line on the plank where the hook lands.  I think every author has a different way with a different tool for doing this; every way demands that whatever tool is used to mark the pattern is used to mark the plank.

 

How do you fill in a hole in the side of your boat?  Same way, except the good wood left on the boat is cut back to where you want it, then the pattern is cut to undersize and nailed in the hole.  Then you do the rest.  The amount of curve in the pattern when it is nailed in place has the curve you are worried about already in it.  All you are doing is adding an inch or so all around the pattern, so when the patch is put in place the curve material is there. "

So there's the preliminary plan.