The Tongass!
Step 6) Building the Jig
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Not seeing any obvious hints in Renn's book or addendums, I decided to do a little homework to determine at what height the top of the jig should be from the floor. It has to be high enough so that when the sheer shelves are pushed down by the stem, that the point of the bow misses the floor, and high enough to be allow working on the bow without power tools hitting the floor either. The top of my jig turned out to be 16-1/4" off the floor when built as shown, and the drawing shows that this does provide enough space (Renn said 16" were required ...his rule works for all 3 of his boat designs, as I've shown.) My jig is built from 9.5"x2" LVL Versalam, 1/2" plywood gussets, and 2x6 pieces to support the wheels. The wheels are 4" casters with brakes. |
| Here I've cut the lumber to length with my 12" compound miter saw (Bosch Rocks!). The long jig pieces are cut to 16' exactly, and the short pieces (ends) are cut to 4' exactly. Note that Renn's jig design was originally 16'x4', but that Jumbo builders have become aware of the fact that the Jumbo's jig needs to be a couple of inches longer in order to carry the Station #11-1/2 mold at the stern (or the Station #3 mold at the bow end if you started measuring aft and went forward.) Rather than screw on a 2x4 to make the jig longer like everyone else has done, I put my end pieces on the ends of the long side pieces rather than in-between. Since the long pieces are 16' exactly, this produced a jig that was 16' 3-9/16" long ...perfect! Against the wall, you can see my new table saw ...sad to say, but I broke the rule on this one. The rule is "If it's from Sears and has a motor, then don't buy it!" But Grizzly messed up my order and lied about it, I needed a saw, I didn't want to drop a mortgage payment on the table for one, and I got this saw on sale, further discounted because it was a floor model. For free, they tossed in a router-table wing extension and the mobile base. This is Sear's 1-1/2 hp belt-drive saw w/cast iron table ($500), the over-priced cast-iron router-table extension ($100) and the over-priced mobile base ($100). I paid $372 for the set ...oh well, guess I'll give Sears another chance. Glad they were remodeling and had to clear out a bunch of space. |
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Here's the finished jig. Note the structure at the corners, showing how I put the short pieces on the ends of the 16' long side pieces in order to make the jig longer. Turned out pretty nice. The corner-to-corner diagonals measure to within 1/32" of each other and the jig turned out very solid. The piece in the middle is a 2x6 intended to be a landing for a couple of 4x8's that I'll screw down on top of the jig. I'll be using the jig, aka table, as a platform for scarfing the long panels for the boat. I may leave the extra 2x6 in place too, since it adds a little more structure and helps the middle of the jig stay at exactly 48" wide. Due to my tight building conditions, I will have to do a lot of jig rolling and maneuvering in order to get around the shop and work on different parts of the boat. I wanted the structure to be very stiff and strong so it would stand up to the extra abuse. |
| And here's a close-up of the corner and end structure. The LVL was screwed together at the corners with 4" deck screws, the 1/2" plywood gussets with 2" deck screws, the 2x6 for the wheels with 3-1/2" deck screws, and the LVL was lag-bolted to the 4x4 supports with 3-1/2" by 5/16ths lag bolts. The mitered 4x4 pieces in the corners were installed to add additional strength, but if you aren't going to be rolling your jig around a lot like I have to, then you can go lighter with these pieces. Probably a 2x2 would work fine. Note the centerline carefully measured and marked on top of the end piece. I double-checked the centerline marks by measuring diagonals from the corners at the opposite end of the jig ...El Perfecto in both cases! Ready to start scarfing and building the boat bottom... |
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© Copyright 2004 Brian Dixon
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