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AppShip4 Photo Gallery

Page history last edited by Alex Finnegan 9 years, 3 months ago

AppShip1 Photo Gallery AppShip2 Photo Gallery AppShip3 Photo Gallery 5-Byker Boat Gallery 6 Joan Dixon Gallery

AppShip 4 was a shorter project with 6 participants who built a 12ft canoe in June 2011

Here are some of the photos of the build which took place in Bedlington Community High School, Northumberland, UK http://bchs.uk.net/

This canoe was built using the "stitch and glue" method of plywood fabrication where the planks are joined with wire "stitches" then glass fibre tape is applied to the interior seams. Once the taped seams have set the wire stitches can be removed and the exterior sheathed in fibre glass cloth.

A series of 3mm holes are drilled at intervals along the edge of each plank, these must correspond to the holes in the adjecent plank. It is quite easy to end up with the small holes for the wire being out of alignment so it is best to start with just a few holes to hold each plank in place, then once you are confident that the plank is accurately aligned at the bow / stern the remaining holes and stitches can be drilled and wired. The ends of the wires are a bit sharp and will scrape skin and could pull threads out of clothes, so take care.

While the planks are held together with the wire stitches the shape of the boat is very weak and unstable requiring temporary moulds fixed inside to prevent the "pea-pod" shape from closing up or sagging too low in the middle.

Inserting extra moulds will give a more fair curved shape with fewer "hard-points" (sections that are straighter), but while this gives a guide for the rough shape, it is the tensioning of the wire stitches and the careful easing of plank edges that will address any bulges where the individual planks come together. In this photo above, the bow (at the bottom of the photo) has a clear kink where the top planks are misaligned with the bottom planks. This sort of misalignment will gradually be pulled out by tensioning (and easing) the stitches, however, adjusting one plank will effect others so you may have to fix sections more than once.

The wibbly wobbly bow can be clearly seen here and while it was adjusted, if you look closely at the finished canoe at the bottom of this page a tiny kink is still there. These planks were cut by young people learning to use a jigsaw and the small wobbles in the edges of the planks tend to combine to create hollows and bulges when the planks are stitched together. This is not a problem for this particular project, but if you are building your own boat you may want to develop an interal Jig to ensure that the planks and shape has greater support during the wiring and taping the seams.

This photograph was taken after a morning adjusting the stitches and "easing" any bumps on the plank edges. Easing plank edges can be taken care of while still wired by using a pad saw (or plasterboard saw), even a hacksaw blade can be used to take bumps out of a plank edge - of course, it is better to cut a nice "fair" curve on the plank edge than to try and "ease" it later.

As the centre of the canoe is held apart the bow and stern will rise up with the tension in the planks. This movement of the boat could undo your fine adjustments so insert the temporary moulds before attempting any fine adjustment in the final shape. Also notice that the canoe is raised up on a piece of 2by4 to allow the stitches to be fixed along the bottom plank.

With little pieces of masking tape over the wire stitches to highlight their position and avoid gluing them in place, we can begin to place the glass fibre tabs on the seams. These tabs gradually take over the job of holding the planks together, towards being able to remove the wire stitches for sheathing the exterior. We are using biaxial tape here and while I find these short glass fibre tabs quite unsightful, the necessity to remove the wire stitches prevents us from using longer lengths which would look less obtrusive in the final boat (though the difference in the end boat is slight).

These three moulds (upright pieces of wood), when viewed from this angle show how "hard-points" can develop in the top plank. If you look towards the top right of this photograph where the top right plank touches the moulds we can see that the plank tends to be curved more at the mould and curved less between the moulds (it should be an even curve). These "hard-points" are partly due to the plywood planks being quite thin and while the gunnel battens (pieces of wood glued and clamped to the top edge of the boat) will "fair-out" and smooth these bumps later, it is worth considering the use of a temporary batten clamped around the inside top edge of the hull to ensure hard points are not fixed into the shape.

Here we have an oar blank, or rather it is a paddle blank. Paddles are held in both hands and are not pivoted on the side of the craft.

The paddle blades are symmetrical and this shows one paddle blank marked and another with the spoon outline cut.

The mast gauge is used to mark out the waste that must be removed to "round-off" the shaft of the paddle.

Using the Drawknife the square shaft of the paddle is gradually carved into a round section. A taper has been planed onto the grip end to make it lighter and more comfortable in the hand.

Here we can see the drawknife being used with the sharpened side up, this risks the blade digging in too much, but as the flat of the blade rests against the wood it also offers a continuity of cut if the shaving is being taken off the correct area.

The temptation is to step in and say "use the drawknife the other way up", however, we believe that everyone must discover the tools for themselves and while we all stay safe these insights are an integral part of the learning process.

These are two oars which we were making in parallel to the canoe paddles.

With the Glass Fibre tabs inside we can begin to take the wire stitching out by cutting the wire and pulling it out.

These sort of repeditive tasks allow us to develop techniques and try out different formats of team working.

There will always be elements of a task which involve exceptional difficulty, here we can see the team take on the problem that there is not enough room inside the bow to snip the wire. The answer is to unwind the wire, cut both ends on the outside and pull the remainder from the inside.

While some participants were unwinding the stitches, others were snipping the wire on the inside, then a third set were pulling the ends out and finally the ends were cleared off the floor. Teams naturally find these shared processes where everyone has a purpose. This sort of team working is also important as hands and fingers get tired using pliers and jobs can be rotated so that no one is left with all the work.

The canoe shape can be more easily seen with all the stitches removed. This allows us to begin to place glass fibre tape along the remainder of the interior seams where the wire stitches had previously been.

With our "Space-suits" on we are ready to tape up the interior seams.

One participant begins to cuts the lengths of glass fibre tape.

While the epoxy resin is measured and mixed.

Then we "wet-out" the tape with (well mixed) epoxy resin.

A third group "wets-out" the areas of the plywood where the tape will be placed.

And finally the the wet-out tape is applied to the wet-out plywood seams. This photograph above shows a piece of tape which is translucent at the bottom (wet), but is still white (dry) at the top edge. When applying Glass Fibre tape the brush is mainly dry, pressing the tape into place, don't be tempted to smother the tape in resin, you should be able to see the weave of the cloth through the resin.

Epoxy resin sticks to just about anything - except itself! Well that is not entirely true, Epoxy resin can bond to a wide range of materials, however, Epoxy will not bond to waxy materials and many plastics such as High denisty Nylon or Polyeruathane -this is why we cover our moulds with plastic packing tape to stop it sticking. When Epoxy resin cures it releasing "Amines", which form a waxy "amine blush" on the surface of the cured Epoxy. The waxy Amine blush must be washed off before any further Epoxy is applied to that area or it will not stick.

Within commercial boat building facilities a special cloth called "peel-ply" is placed directly onto an area of epoxy and wet-out during the process. As the peel-ply is made from nylon or polyester it does not bond to the glass fibre, but the Amine blush rises through the peel ply and once the assembly has cured the peel-ply is ripped off to reveal a surface free from amines and ready for a secondary bond.

We had to shut the garage door as the sunlight was heating up the boat, this heat would "kick-off" the resin, making it set much faster than normal. The thermo setting properties of Epoxy can even be seen when holding the bottom of the mixing cup in the palm of the hand. The heat of our hand will accellerate the curing process resulting in an "exothermic reaction". Always hold the epoxy cup around the rim, or set it down to avoid an "Exotherm".

Appyling the resin to the tape in advance allows the Glass Fibre a few moments to absorb the resin. When the next piece of tape is layered on top it draws the excess of resin from the first piece which is absorbed into the second piece. The glass fibre cloth should all turn translucent with no areas remaining white, but we don't want so much resin that it drips or runs.

Here we can see all the interior seams applied.

The interior seams are washed (to remove the amine blush), allowed to dry and then given a light sanding to remove any sharp edges.

With the interior seams fully cured and sanded the boat is carefully rolled over ready for sanding back the exterior seams.

With the seams sanded back and a small amount of filler applied to any hollows the hull is ready to be sheathed in glass fibre cloth.

With the hull fully "wet-out" with epoxy resin, the glass fibre cloth is stretched over the hull.

Epoxy is sticky stuff, so we try to pull the cloth tight to get the wrinkles out.

With the glass fibre cloth laid upon the "wet-out" hull we go over the cloth pressing it into the epoxy on the hull. As the Glass fibre absorbs the resin from the hull it will gradually go translucent, but more resin may need to be carefully applied. We have to cut the cloth around the sides and ends to ensure there are no wrinkles, fewer cuts are better and a special weave of cloth called "twill" is able to adjust more easily to the compound curves of a boat more readily than standard glass fibre cloth.