Building Logs

Engine bay lid cut out.

Posted by Paul

After another 6 hours of sanding then re-bogging, sanding and re-bogging over the 4 weeknights this past week I think I have the steps fair. By wrapping a flexible batten around the step fronts I could see the hollows. Strip planking does not create a curve, it creates a series of small straights and bends that from a distance looks curved, but to finish the curve completely you need to bog the surface then sand back to the base glass effectively building a little part of the curve between each kerf. Eventually you should have a series of lines where the bog is removed to the glass and a series of bogged sections. In places the bog is continuous but very thin in parts, a little thicker, as much as 2mm in other.

In all I think I applied bog and sanded it off again about 5 times before I had what I thought was a fair enough surface on the step risers. I then repeated this on the foam front edges. As I went I also back filled small pocks and marks, air bubbles and various other blemishes to now have a pretty smooth and fair surface. Apart from edges that still need to be finished (rounded off where they are round, squared off where they will be square) the fairing is almost complete.

Marking out the engine bay lid was easy enough. Cutting it out was much much harder. I dont have an expensive jigsaw. I am told there is a big difference between a good one and a cheap one. I have never been much good with a jigsaw and they say a good tradesman never blames his tools but my jigsaw technique often sees the blade wandering all over the place. But today cutting out the engine bay lid I made a couple of mistakes as well as the poor wandering of the saw blade. The first mistake I made was to cut with the jigsaw flush against a curved front instead of square to centreline, meaning I was following the line on one side but missing it completely on the other side because of the angle the blade was cutting at.

Fortunately I did not cut much at that wrong angle and glue will fill the line that I cut out wrongly. I also had a number of corners that the jigsaw could not reach into, but I figured that I could just cut some from the inside and some from the outside to cut into all of the places. I had marked the lid on both sides of the step set. But cutting from one side to the other meant not all cut lines met exactly to the mm. That is not such a big concern and I will be back filling the edges on both the lid and the opening and overfilling them before sanding them back to neat and square everywhere. So in effect I will need to make the gap between them oversize so that they don’t bind anywhere. I am not so concerned about these hatches sealing well (although I will be making sills) as the engine bay is a wet area and there will be more water inside than out!

Once I had the lid completely cut out I attached plates under the steps so that the lid would sit in it and I braced the front so that where the hatch lid was removed leaving a void I wanted the 2 halves to be braced to each other so that the part would not twist or easily break as I mounted it on the boat. This part will come off and go on a few times before it is finally glued and glassed in so I want it to be robust until then, and when fitted it cannot be twisted in anyway or else the lid wont go back on fair. I then lifted the part onto the boat again to see that the cut-out worked.

open motor hatchmotor hatch lidengine hatch egde decoredengine lid edge filled

I was satisfied that the cut out worked well but I realised I may have made another small mistake, I curved the corner of the lid when cutting it out but I may have been better off having a square corner, I am not sure yet. A square corner is a weak point in that at the corner cracks can start whereas on a curved corner cracks cannot start but I may have difficulty with the lid binding with the curve whereas that could not happen with a square corner.

Next job was to de-core the edges of the hatch lid. This is a fairly easy task but must be done correctly and well to be sure of a good seal for the balsa core. I run a router around as much of the edge I can close to the glass with a special blade for cutting a line down into the balsa close to the glass. I run it each side, although being steps there are many places the router wont reach. This is not a big problem because getting the core out is not difficult. Once the slots are cut I use a chisel to push through between the glass either side cutting the core out. You can drag the chisel or push it, the core just comes out in clumps at first. You dont need to worry about it being too neat in there but you must get every last trace off balsa off the glass each side. There are 2 reasons for this. First you want a glass to glass bond for the backfilling you will replace into the trench and secondly anywhere that balsa stops glue it is an ingress point for water. It wicks in through any balsa you leave on the edges into the core inside. Even though the balsa is edge grain (the grain goes from one glass side to the other not along the board) and theoretically water cannot travel across it only along it, you must seal the edges completely to be absolutely sure. To not do this properly would be like putting deadlocks on the doors then leaving the window open. All you need to do is run a sharp chisel along the glass both sides chiselling off any balsa residue. Not hard at all.

With all the balsa removed, I mixed up a thick mix of a combination of coving material and glue mix, the glue to add strength, and back filled the edges packing the mix in tightly and over filling it. Once it sets I can sand it back to a neat square edge, and finish the fairing, including cleaning bog from up inside and under the foam groove that the LED strip will be siliconed into and then fitting the rope light. I will then mask it over and start the painting (which includes more fairing of the highbuild) process.

I am running out of time before the boat show. I only got 2 hours work done yesterday as Jo and I went to Groovin the Moo, a rock concert at Maitland show grounds. We saw about 10 bands, the highlights being the first and last bands we saw. The first band we got to (the 3rd for the day) at around 1.30pm was called Children Collide. They were fantastic. There were a number of good bands after them, Jo likes Little Birdie, we both liked the energy of Mammal, we both liked The Grates. At first I didn’t much like the Drones but they grew on me and the last 2 songs they did were good. Neither of us liked the US bands Okkervil River, we didnt like them at all, De La Soul were ok but not much new, they played their hit from the early 90’s Hey how ya doin, sorry you cant get through….just about everyone used that as an answering machine message at some point, in the days before mobile phones. Neither of us liked Architecture in Helsinki, they were just a bit weird and maybe we were (well I was) getting impatient for the highlight for both of us and the reason we went, was to see the Hilltop Hoods. They are Australia’s best hip hop group and they didn’t disappoint us. They were fantastic. We skipped the last band, The Living End, we like them but did not want to stay. We had a great day among all the teenagers.

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