CORRECTIIONS ON THIS POST-MEASUREMENTS AND SHIMS, TEMPLATE FOR APRON, LAMINATING FIRST 8' OF NEW APRON TOMORROW

[bob mitchell]

     JULY 14, TWO WEEKS AFTER THIS ARTICLE WAS WRITTEN - NOT SURE ABOUT THE HEIGHT DISCREPANCY - i MIGHT HAVE EASED THE WHOLE CABIN UP, OR REDUCED THE DOWNWARD FORCE WITH THE CRADLE SO THAT WHEN THE FOORS WERE UNBOLTED THE FRAMES OR CABIN STRUCTURE ROSE 1/4 TO 1/2 ". tHE CURRENT PLAN IS TO BOLT THE FLOORS, NEW AND OLD, BACK INTO THE ORIGINAL FRAME HOLES, AND THEN EASE DOWN ON THE JACKS AND CRADLE. SO TAKE THIS ARTICLE WITH A GRAIN OF SALT. Yesterday I was caught off guard by apparent shims or spacers under the apron. The bottom area of the apron was in such bad shape that the shims were immeasurable mush. The reason that this is critical is that when the 4.5",  6 layers of 3/4" plywood apron is put on top of the deadwood, the floors need to rest on it solidly to distribute the weight the frames carry. My test fit of the floors showed them basically 1/4", more or less, above the apron. I was freaking, but by 3 in the morning I had come up with several solutions. But how could I confirm the discrepancy and find all the shim values short of installing all the floors, Or was the whole thing my imagination?

     Well fortunately one of the things I did before I went on the destructo rampage was take a lot of measurements and record them on a photo.

One of the sets was the vertical height from behind each floor from the apron surface to an arbitrary but reproducible taut line stretched between the top of frame 6, which stayed, and a point 28" above the apron surface at frame 16, which stayed. Not even a level line, BUT REPRODUCIBLE. So this morning I stretched that line again, and the difference between the original and the today gives me the thickness of the necessary shim at every floor, which turned out to be a consistent 1/4"  (assuming no space for glue and bedding compound in the 6 layers and bottom respectively. Boy did I feel better.

       But it really doesn't matter that much because when I laminate the apron in place tomorrow I will not fix it to the deadwood (except by clamps and the keel bolts serving as clamps) .Once I install the floors, and remove the bad sheathing temporarily left in place - its all part of the boat fabric, shape and movement data base - ( and while we are on the topic of sheathing Clyde and the boat building world refer to it as PLANKING, so I will adopt that lingo from now on) I will be able to shim the apron so that it supports the floor, and then put expanding bedding underneath. Below is the template for the plywood. The bevel is mostly in the bottom 2 sheets and is easily reproducible on a table saw. As you move forward the bevel increases a little by floor 8, and there are some tricky parts to the at the stem intersection, but I saved the apron chunk from there for a guide. I am getting AC Douglas Fir Marine Plywood for $75 a sheet - probably take 6 to do the whole keelson if necessary. Will use west system epoxy for this critical lamination. CORRECTION - THE DOUGLAS FIR WAS 5" WHERE I MEASURED IT, BUT IT ACTUALLY TAPERS DOWN TO 4" AT THE STEM JUNCTION OVER (FROM 5 1/2")

THE LAST COUPLE OF FEET SO THAT THE VERTICAL PLYWOOD ON EACH SIDE OF THE DEADWOOD CAN TRANSITION SMOOTHLY INTO THE FOREFOOT. (CORRECTION MADE ON JULY 14, 2010)The Douglas fir deadwood is 5" wide, with a vertical layer of 3/4" Doug Fir on each side, so the bottom lamination starts at 6.5" and widens with the bevel. Top of apron is 12" across.

          Here is some more fastener documentation. As I moved forward and the planking got a little better, but still bad, it was easier to use my side grinder to cut these nails than to try to pull them through. Once again, I am impressed with the holding power of these boat nails.