Hull Construction
The hull is made in 1/8" balsa and made around the three formers fixed straight to the deck, the bottom panel requires either steaming or soaking to allow it to bend to the required curve and then the sides are planked with the grain vertical between deck & bottom.
1. Glue together two of the 4" x 1/8" balsa sheets, this can be most easily achieved by butting them together on a flat surface joining them with masking tape along the seam. Then unfold the two parts, put glue along the edges and fold back into place, return to the flat surface.
Hot tip
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I would recommend using cellotape clear rather than masking tape for joining the deck sheets. Use a few strips to pull the sheets together and then turn them over and run a strip over the whole seam. |
2. Either using the templates provided, or from cut outs from the plan carefully cut out the balsa parts to make the hull, if using paper templates it is often easier to over cut the paper and stick it to the balsa sheet, then cut through both the pattern and the balsa together.
3. Cut out the bulkheads, the centre bulkhead requires some additional supports which are shown on the plan, be careful to add each of these to the correct side of the bulkhead. The grain in the balsa should be running in the opposite direction on the support piece to the grain on the bulkhead.
4. The bulkheads can now be fixed to the deck. It is essential that the transom be supported with a temporary gusset to achieve the correct angle, this is also desirable at the middle and bow bulkheads. These can be made to the correct angles using the plan, the middle bulkhead supports should be fixed forward of the bulkhead and the bow support can be left in place.
5. Two pieces of 1/8" balsa are used to locate and support the fin and should be added at this stage, you might also consider adding a length of 3/4" x 1/8" balsa from the bow to the middle bulkhead for additional support the the jib fixings depending upon your foredeck hatch layout.
6. It is advantageous to pre-bend the bottom panel this can be done by soaking the balsa and then tension it around a drum to the required curve, which can be checked against the elevation on the plan and allowing it to dry. Alternatively the panel can be soaked and bent over the bulkheads and fixed in place, however you will need to fix the deck down to a flat surface to prevent the tension in the bottom panel lifting the deck to an undesirable curve.
7. Carefully sand a small section along the sides at the bow and stern so that they are to the desired angle and then fix in place the first sections of vertical planking, one each side at the bow & the same at the stern. It is easier if these first pieces are shorter than the full width of balsa sheet. It is important that these pieces are fixed first as they help to keep the hull rigid and to shape. At this stage check that everything is square and as it should be and adjust then if required.
The temporay supports to the bulkheads can now be removed although it is perfectly possibly to finish the hull and remove them after cutting out the access hatches.
The temporay supports to the bulkheads can now be removed although it is perfectly possibly to finish the hull and remove them after cutting out the access hatches.
8. Using a supported piece of sandpaper wide enough to go between bottom & deck panels lightly sand the edges of the panels so that the side planking makes a nice joint at the edges.
9. Now starting from the stern, vertical plank using the full width of the balsa sheets, fixing to each side in turn so as not to induce a twist in the finished hull. Place the sheet on the side and mark it top and bottom, cut about 1/4" surplus onto the piece which can be sanded off later, When you reach the bow fill in the final section by cutting a piece of balsa to fit.
10. Sand down the excess balsa from the sides, following the curve of the bottom and line of the deck, the bow can now be formed, either glue a block of balsa or 3 sections of 1/4" balsa to the bow and sand to shape, the rest of fleet will apreciate it if you try to produce the nice rounded shape to the bow shown on the plan!
11. The key with using resins and glass cloth is preparation, have everything to hand before you start. It is advisable to wear latex gloves and cover work surfaces as everything does tend to get sticky!
Cut out the two pieces of glass cloth required to cover the hull slightly oversize, if it is your first time using resin we would recommend using epoxy finishing resin (Z Power Finishing Resin) which has a longer cure time than polyester and allows you a little more time to make adjustments.
Place the hull upside down on a piece of wood to elevate it, and keep the excess cloth at the sides free of the bench. Mix enough resin and coat the bottom & sides of the hull ensuring that it is completely coated, with epoxy resin it is essential that you do not add to much hardener otherwise it will come out rubbery rather then solid.
Lay the glass cloth over the wet hull and adjust to a nice fit, now add more resin pushing it into the cloth with a stippling action to remove any remaining air pockets, once it is completely covered any excess can be removed by smoothing over using a plastic credit card.
Allow to dry, this can be accelerated slightly by ensuring the hull is in a warm dry environment, once dry sand away excess glass cloth from the deck edge.
Turn the hull over and repeat the process for the deck.
Cut out the two pieces of glass cloth required to cover the hull slightly oversize, if it is your first time using resin we would recommend using epoxy finishing resin (Z Power Finishing Resin) which has a longer cure time than polyester and allows you a little more time to make adjustments.
Place the hull upside down on a piece of wood to elevate it, and keep the excess cloth at the sides free of the bench. Mix enough resin and coat the bottom & sides of the hull ensuring that it is completely coated, with epoxy resin it is essential that you do not add to much hardener otherwise it will come out rubbery rather then solid.
Lay the glass cloth over the wet hull and adjust to a nice fit, now add more resin pushing it into the cloth with a stippling action to remove any remaining air pockets, once it is completely covered any excess can be removed by smoothing over using a plastic credit card.
Allow to dry, this can be accelerated slightly by ensuring the hull is in a warm dry environment, once dry sand away excess glass cloth from the deck edge.
Turn the hull over and repeat the process for the deck.
Hot Tip from master builder paul risdale
I always cut the deck access holes before building the hull – makes it easy to hold the hull when skinning the bottom. I suggest that it is easier – especially if you have never done any glass skinning before - to do the deck and stern first and then the hull.
I apply a coat of resin over the whole surface, lay the cloth over the wet resin and then gently smooth the cloth with a fingertip (gloved of course) working from the middle outwards. A credit card (or a piece cut from a Pringles canister lid for curved surfaces) is used as a squeegee to remove the surplus resin. Wiping the card after each pass. Any dry / white patches of cloth need a little extra resin – if it can’t be pushed from the surrounding area. Using this technique I rarely have to add additional resin.
When skinning the hull you need to cut a slit to overlap at the bow. Use a razor blade or a new snap off knife blade.
Look critically at the edges where the cloth leaves the hull. Make sure they are stuck down with no wrinkles. Keep working with the card until they are.