The job of the base in building an ENVIBOATS design is quite simple. Provide a large, stable platform on which to erect the jig. (We provide a diagram and material list of the base with our kits.)
It should be roughly the size of the maximum beam and the LOA (Length Over All). Take into account the standard sheathing size is 4'x8'. So, if you are buiding a 27' boat, go ahead and make the base 28' long as this is perfectly divisible by 4'.
The base should consist of longitudinal members, transverse (crosswise) members and sheathing. The longitudinal members should be doubled for two reasons. Length and strength.
Standard construction dimensional lumber can be used for the structural components of the base. The thickness of the structural member is always "2x" material. The width (2x4, 2x6, 2x8, etc.) can vary depending on two factors:
The quality and "trueness" of the floor upon which the base sits
The size of the boat.
The quality and "trueness" of the floor upon which the base sits: Basically, the question you are trying to answer is "How much shimming does it take to make the base perfectly flat. If the floor is very flat and it will take very little, then 2x4 lumber should be sufficient for boats under 36 feet. It might even be appropriate for bigger boats. If,on the other hand, a great deal of shimming is required, then it is likely that heavier lumber (2x6, 2x8) should be used. When in doubt, give us a call. We will be happy to help you decide. Remember, the base is the starting point for the quality of the boat.
The size of the boat: For most of our boats, up to about 36' LOA, 2x6 dimensional lumber should be an excellent choice for the structural members. Beyond that length, 2x8 lumber should be used. The joints should be staggered in the longitudinals in order to create the length required. The transverse members should be on 24" centers. Typically, the transverse members will be trimmed in length so that the overall width of the base is divisible perfectly by 24" increments. (Depending on the actual beam of the boat 12" increments might also work.) When cutting the transverse members to length, don't forget to take into consideration the width of 4 thicknesses of the longitudinals. (6")
It is usually easier and a bit stronger to put the base together with screws rather than nails.
Leveling the Base:
It is vitally important that the base, upon which you setup your ENVIBOATS jig and build your boat is level and true. It is critical to level the frame or structure of the base prior to sheathing it with plywood (or OSB). Otherwise you will have a great deal of trouble removing the sag in the center of the base.
Fundamentally, the process involves:
Find the highest corner
Bring the other corners up to that level
Remove the sag from the middle of the base
There are several methods you can employ to level the base; each employing increasing levels of sophistication.
Water will always seek level. Buy some thin clear plastic tubing. The proper length would be a bit longer that the length of two adjacent sides of your base. Most local Home Improvement Centers sell this tubing by the foot. You will also need some string. Fill an old one gallon milk jug with water and add a few drops of red food coloring to make it easy to see the level of water once you have it in the tube. Next, siphon water into the tube and, with a helper, begin by verifying which corner is the highest corner in the base. You do this by holding one end of the tube against the base on each corner and comparing the level of the water at the other end of the tube held against each other corner.
Once you determine which corner of the base is the highest, shim every other corner to that level. Now use the string, stretched end to end of the base and corner to corner, and shim any sag out of the base.
Modern laser levels can greatly speed up the process.
ONE WORD OF CAUTION: Never, under any circumstance, put yourself in a position where you might accidentally look into the laser.
Use some scrap wood to make a few laser targets. A target might be two small pieces of 1x4 material tacked together at a right angle. Place them in various positions on the base such as one on each corner and one in the center. Train the laser so that it simultaneously hits each of the targets. Walk around the base with a tape measure checking distance from the top of the base to the laser line on the target. The corner with the shortest distance is the highest.
Shim each corner and the center until the distance from the laser line to the base is equal on all targets.
There is simply not much point in explaining this method. If you own or have access to this expensive device, you know how to use it.
Now, ensure that the base has enough shims to make it a solid platform and remove any springiness.
Laying Out the Base For Jig Assembly:
The frame spacing on ENVIBOATS Jigs varies depending on design. Most boats use center to center frame spacing of either 18, 20, 22 or 24 inches. The frame spacing is always halved in the bow section of the jig. These sections are under much more stress as the curves are more pronounced. The bending of the keel and skin in this area can both lift and distort the jig if not properly supported by spreading the load across more frames.
With your package of documentation, you received a jig mold station layout sheet. This sheet describes the jig spacing for your particular kit. If you purchased either the FasBuild™ floors or bulkheads, additional sheets indicate the location of these components relative to the rear edge of the base.
Begin the layout process by marking a centerline down the entire length of the jig. Continue by adding two more lines, each offset on either side of the centerline by 36 inches. We'll call these the "side" lines. These will help verify the squareness of your jig station lines. Refer to your layout sheet and mark the side lines where the stations will be erected. Early in the process, cross measure the layout marks from two adjacent stations. If the cross measurements are equal, the stations will be square to the centerline. Simply placing a carpenter's square on the side of the jig to check squareness of the station layout lines is NOT SUFFICIENT.
Continue the process marking each station position and frequently monitor the squareness. This also helps to double-check for simple measuring errors. We all make them. You can't be too careful at this point. Once you have all of your station positions marked, mark station layout lines by connecting the layout marks.
Note: One "trick" at this point is to pour out a quart of clear polyurethane floor finish and spread it over the layout. When it dries, your lines are permanent.
If your frames and any FasBuild™ options have not yet been assembled, we think that your base is probably the best place to assemble them. If they have, it is time to proceed to the next step.