NOTES ON REPLACING FRAMES

[bob mitchell]

    I'm on frame 38, the last full frame, and it is fresh in my mind, so here are some notes on general Newporter anatomy, and the replacement of a frame without using a bandsaw. I write this now because in a couple of weeks it will all be mush in my mind.

     Let's start with this picture of my situation.

 

 

     The new scarfed in chine is the backing for the side/bottom planking. The first layer, as original,

is 3/4 ply, and the second is 3/4 doug fir. The doug fir has not been planed yet (will post an article on chine replacement soon). Perpendicular to those you can see frame 36, completed, 37 in progress (now complete), and the dark remnants of the vertical side member of frame 38. White "floors" can be seen bolted to the apron. There is a batten along the bottom with a piece of 3/4 on it to represent the bottom plywood. The batten aids in locating the frame member and fairing the boat hull's lines. Back to the left, in the upper cut out of plywood, the outer clamp, or shear clamp, can be seen. The wider board with two bolts in it, below the outer clamp, is the inner clamp. Both of these clamps run the full length of the boat. The inner clamp is what the deck beams rest on. The deck beams are bolted to the frames, and the frames are fastened to the inner clamp. The outer clamp runs in a notch cut into and on the outside of the frames. The deck edge rests on top of the outer clamp. The side plywood extends past the deck, and forms the first layer of the bulwark, with two additional layers of 3/4 ply

fastened to it above the deck  ---ALL WITH END GRAIN POINTED UP ---so it is extremely important to maintain your cap rail.

          So with that out of the way, you can see that I have frame 38 to build. Now that the new chine is in place I can use its backside to locate the joint between the upper and lower member of the frames. The other reference locations for the frame are the deck and the lower edge of the apron. The template basically represents ONLY the front surface of the frame. That is a very important point because all of the frames have bevels, and there is port and starboard, which means the symmetry/asymmetry demons will befuddle you everytime if you are not thoughtful about them (as you might see).

        The next photo shows a luan template clamped into place on  frame 37

     The two pieces of luan, precut to the correct dimension, are clamped together while the glue drys. The back of the junction is cut to fit the chine surface, while the upper end fits the deck/upper frame intersection angle, and the lower end fits the apron/bottom frame intersection angle. After it drys I remove it a take it back to the shop, mostly because it is so hot I can't take it anymore! (and some good tools are back there.)

     So not everyone has a giant bandsaw to cut these frames on, so here is a way to do it on your table saw, or with a skill saw alone if that is all you have. I crammed as much as I could into the next photo of relevant points to think about.

     First note the completed template. The flat area is the width of the chine back, as would be expected, because the plywood bottom or side must run smoothly from the frame onto the chine.

Next note the beveled nature of the frame - to get that dimension YOU CANNOT START WITH THE DIMENSION OF THE FRAME FACE - you have to start with a larger dimension. It is very useful to have a square around to project up from the surface to the edges of the frame. The one in the background of the picture is being used to line up the edges of the original and the new. If you put the square on the other side of the original, and measure to the far edge, you get the dimension of the stock you need to start with (assuming no curve, a point I will explain in a minute). Measuring from the edge of the old to the table saw guide will also give you that dimension, but the table saw blade reading will not.

     So to start the process I drop a piece of the old frame onto the table saw to set the angle. Then I run my new stock through it. (for the last time, assumiing no curve) Hard to go wrong doing it that way.  Note that the lower frame and the upper frame member may have different dimensions, with the upper frame limited by the distance from the inner clamp to the plywood sides, on an angle.

     Now I cut my template apart to layout the upper and lower frame member, assured that they will fit well when put the pieces back together.  See photo starting part 2 since I only get 3 photos per forum or blog.