Building Form

So I have four of the five frames built, and the next logical step is to build the transom, which includes a mahogany frame as part of the finished assembly (labeled frame '0' on the plans). The transom is the very back (aft) of the boat on which the motor is mounted. The transom will be made out of a 3/4" sheet of (expensive) meranti plywood. I started reading various sources on how to build the transom as I simultaneously looked at the plans. The transom is required to "lean back" 12 degrees (per the plan) from vertical in order for most motors to hang properly and this is obtained by cutting a 13 degree angle on the bottom edge of the transom assembly. It seemed that the more I thought about the transom, the more difficult it appeared to me. I know that I was over-thinking the situation, but I decided to put the transom on hold and to work on setting up the building form.

 The building form is a structure typically made up of construction lumber on which the hull of the boat is built upon. The structure cannot just be thrown together in a willy-nilly fashion and expect the shape of the hull to come out as the designer intended. The form is the reference structure on which the hull frames and stem are accurately placed. It should be noted that the hull is built UPSIDE DOWN on this form. This form must be fastened to an immoveable structure such as the concrete floor of my shop and must be immoveable as I push, pull, tug, hammer, etc as I put the hull together.

The fore/aft reference point used to set up the form is the very front tip of the boat - the breasthook point. The vertical reference point is the blocking on which the breasthook sits. Before getting started on referencing, I first secured a base for my form to the concrete shop floor using anchor bolts. The base is 16' long and is comprised of two 2 x 6s butted together. Upon this base, I attached 2x blocking on which the breasthook will sit. Under normal circumstances, this should be very easy and straightforward. However, the concrete finish work done on my shop floor was horrible and my floor has dips, high spot, and is not level. It took me some time to get the base boards somewhat true and to get the breasthook blocking trued up. Shims became a necessary material for me.

With the base and blocking in place, I needed to come up with a way to easily transfer measurements from the breasthook references as noted on the plans to setting up the two main stringers that make up the building form. These stringers are 12' 2 x 6s and must be parallel and level to each other. In order to achieve this, I made a reference frame out of scrap wood that was the exact height as shown on the plans. for a fore/aft reference, I just attached a board to the front of the breasthook blocking and I used the face of the board as a 0 reference. The assumption of course was that when I set the stem in place, the breasthook point would just touch the face.

Reference framework and vertical board

Stringer set up

With the reference framework in place, I then use a 6' long level and place it on top of the framework and have the other end of the level sit on top of a stringer. It was a bit of a challenge getting the stringers set up due to them being heavy and cumbersome. Once one stringer was set, I then had to ensure that the 2nd stringer was not only at the proper reference height, but also stayed level and parallel with the first stringer.  Again, this appears relatively easy on the surface, but I admittedly struggled with getting the form set up where I felt comfortable with its accuracy. I believe a lot of this has to do with my shop floor inaccuracies, but I eventually got it.

Once the basic form was set up, I then set the frames on it and added braces which will also double as mounting blocks to hold frames securely to form once I am absolutely sure all frames in proper position. At this point, no frames are locked down.

Frames loosely set on building form

This all was accomplished by November, 2013. Due to a really cold winter, work has come to a standstill in my shop for the last several months. Next up.....my transom challenges.