Latest forum posts




Self Aligning Jig System :: Self Aligning Jig System 2

Self Aligning Jig System-Part 2

Before starting with the hull planking, we must assume that the builder is familiar with the use of epoxy and fiberglass. If not, see the tutorials at our web site or refer to the excellent System Three Epoxy book. On request, we include the epoxy book free with every epoxy kit order. The procedure and work sequence we list below is our preferred one. Feel free to adapt it to your preferences.

Once the jig is ready, cut the panels for the sides and bottom. The dimensions on our expanded panels drawings are very accurate: there is no need to use a safety margin. We suggest to start planking with the bottom panels. Cut the panels and use fiberglass splices to join the pieces of plywood. The plans or building notes specify the type of glass to use.

The picture shows a butt block (plywood) at the bottom and a fiberglass splice at the top.

Install the bottom panel on the jig and keep the stitches loose, you will tighten them later.

The side panels are next. Proceed as for the bottom panel: cut, splice and install on jig.

If your plans show overlapping topsides: (sides in two pieces), read the remark below about overlapping side panels before splicing the side panels together. If your plans show the topsides in one piece, disregard this note and what follows in italic.

Some of our boats have their topsides in one piece, others use two overlapping panels. This has several advantages: - it creates an extra longitudinal stiffener. - the smaller panels are easier to handle and in some case, allow for a more economical nesting of the plywood: less sheets to buy. - the small ridge between the panels, called a style line, visually breaks that large surface in two. It is not only more pleasant to the eye but hides small fairness problems. - it acts as a small spray rail.
To make long panels, splice the plywood parts together with one layer of the same biaxial fiberglass used for the hull on each sideone face only. We must avoid the extra thickness where the panels overlap, therefore, on the lower panel, the splice is inside and on the upper panel, the splice is outside. A second layer will be applied to the other side of the splice after assembly. Without this precaution, the extra thickness of the fiberglass between the panels would interfere .

Large panels are delicate to handle when spliced with only one layer of tape. Some builders use a temporary butt block or add layer on the other side except where the panels will join. To add the second side panel, adjust it dry first and mark the overlap area with a pencil. Remove the upper panel, generously coat the contact area with an epoxy slurry and reassemble. End of notes specific to the overlapping topsides.

When installing the side panels, beware of longitudinal alignment. If the side panels seem not to fit, slide them back and forth. A small move will bring everything in alignment.
As usual with our method, allow the panels to float. This means that we try to attain fairness first. Use as little fasteners as possible and do not pull the panels against the frames unless absolutely necessary. Ideally, no screws should be used except at the transom and maybe a few at the bow. A good tip is to use C-clamps or small temporary cleats under the sheer to support the weight of the panels instead of screwing through the panels. Some builders also wrap a line (rope) around the hull to pull the panels against the jig.
At the bow, the old trick of using a small batten inside to line up the bottom and side panels can be used. This is illustrated in most boat building books. Use such a batten just behind the most forward frame and adjust the tension with long drywall screws. It is very easy to fair the bow that way but only after proper longitudinal alignment.

Outside fiberglass: Start with some small squares of glass laminated on the chine and around bow and transom. This technique is similar to spot welding: just enough welding to keep the panels in place.

Remove the stitches and cover with one full length of tape.
Fiberglass all other seams in one length, if possible. Remove screws if you used some.

After all the seams are completed, cover the whole outside with the specified layer(s) of glass.
For hulls with overlapping side panels: the fiberglassing of the outside of the top panel is optional. The structure is always calculated without that layer. We recommend ending the fiberglassing of the side just under the top panel edge.
We recommend fairing the hull at that stage, before installation of the strakes and spray rails. Fairing and sanding techniques are described at our web site and in many messages on our message board.

At this point, most builders will want to install all appendages like spray rails and strakes but we recommend to also install the sheer clamp or rubrail. The sheer clamp or rubrail is structural in our designs. It is a longitudinal stiffener. It runs along the sheer. If it is installed inside, we name it sheer clamp. If it is outside, we name it rubrail.

The sheer clamp or rubrail will add stiffness and it will protect the edge while turning the hull over. Plain solid fir will bend easily in most cases but we prefer to laminate that part from several layers: thin battens or plywood strips. A laminated sheer clamp or rubrail is easier to install and stronger. Install strakes and spray rails. The strakes and rails are epoxy glued. Use temporary fasteners (dry wall screws) and remove the screws after the epoxy cure. Some builders prefer to mark their location from outside, drill and screw from inside. In any case, the screws must be removed and the assembly completely saturated with epoxy.

Prime and sand: We suggest to paint the whole outside before turning the hull over but some builders prefer to stop at the primer stage and do the final paint job when the boat is complete. The ease with which you can turn the hull is the determining factor here. If you have strong roof beams in your workshop or if a cheap crane like a tow truck crane is easily available, it will be easy to roll the boat over and finish the paint later. If you have to roll the boat out of a garage to turn it over on the lawn, you will prefer to complete the paint now and avoid another rollover.

Roll the hull over: Many methods can be used from rolling the boat on old tires using levers and jacks to chain hoists or a rental crane but there is no reason to fear this maneuver. A roll over party is also a good solution: the hull is still light and can be rolled over by a small group of friends or neighbors. The molds (frames and stringers) should stay in the hull during the roll over. To secure them, you may want to climb under the hull and do some spot welding between molds and hull skin. Those small fiberglass patches can easily be removed later with a grinder. Don't over do it. Support the hull with blocks and separate the legs (uprights) from the strongbacks. Depending on the roll over technique, you may want to remove the strongbacks from under the hull. One person can move such a heavy assembly by placing some steel pipes under the strongbacks with a crow bar. Roll the hull over and load it on your boat trailer. You may want to provide some lateral support: the hull will be flimsy after the removal of the frames. You are now ready to work on the inside.

Inside lamination: The hull is made of a fiberglass sandwich and we must fiberglass the inside at this point. Instead of working our way between frames and stringers, we will remove all of the interior structure and fiberglass the inside of the hull with long, full length pieces of fiberglass. This is faster, stronger, cleaner and more economical. Prepare the inside surface. Cut the temporary fiberglass tabs between the hull skin and molds if you used them. Remove all of the molds and stringers. Grind the remnants of the fiberglass tabs and smoothen the fiberglass splices. If butt blocks were used or if your topsides are in two pieces, make a quick pass with a grinder over the edges. There is no need to make those edges perfectly smooth but a tapered edge will make fiberglassing easier. Build putty fillets and tape all inside seams first. Fiberglass the whole inside surface with the specified type of fiberglass. Pay attention to the overlaps shown on the plans: they are structural.

Inside framing: Once the whole inside is fiberglassed, the hull skin is complete. We will now re-install the frames and stringers. If it was not done before, this is when you will cut the inside of the stringers for chase tubes etc. It is easier to cut them now than when installed in the boat. Some builders keep the frames in one piece, others cut them at the cockpit sole level and add the upper part later, on top of the cockpit. This makes the cockpit installation easier. Look at the plans and you will see what this means. The stringers must go in first. Proceed the same way than when building the jig, the structure is self-aligning. Important: since you built fiberglass seams and added several layers of glass, the thickness of the hull has changed. You must grind the corners of the frames at chine, keel etc. to fit and, theoretically, shave the thickness of the inside skin off the perimeter of the frame. Since this thickness is only around 1/8" (3 mm) we can ignore it but the corners must be rounded. .

Hard Spots: Install the frames on the stringers. The mid frame first then the other ones. Watch for hard spots at this stage. The stringers and frames should bear evenly on the hull surface. If a stringer or frame pushes on the hull skin in some places and not in others, this is called a hard spot. Hard spots will concentrate loads and this may lead to cracks or even hull failure.

Some builders lift the frames and stringers away from the hull with small pieces of foam or wedges while building the fillets to be absolutely certain that there will be no hard spots. This is not necessary in most cases.
Before tabbing the inside framing to the hull, run a straight edge on the top side of the frames and stringers, where the cockpit sole will be, to verify that they are coplanar (level). Tabbing means welding with fiberglass seams.
Tab the stringers and frames to the hull. Build your fillets and seams as in any other stitch and glue boat. The plans show the specifications.
Your basic internal framing is now complete.
The sole (floor) and deck will add to the structure. In most cases, the sole and deck are epoxy glued to the structure and fiberglass seams are used on the perimeter.. Battens (cleats, nailers) are first glued to the edges of the framing to form a strong beam and the sole/deck panels are epoxy glued to those beams. The edges are tabbed with the usual fiberglass seams.
Fuel tanks, chase tubes and other parts must be installed before the sole and deck. Your basic internal framing is now complete.

You now have a well proven composite boat monocoque structure, one that has been used in fiberglass boat building ever since fiberglass boats existed. It is stronger than traditional wooden boat framing.

From there, each boat layout is different. Please refer to your plans.

If you did not find the answer to your question, please use our message board and we will respond within a few hours.
Or explore the HowTo files at our technical support web site

Self Aligning Jig System :: Self Aligning Jig System 2