Building Logs

Window dressing.

Posted by Paul

Now that the windows have been cut out of the turret, the boat has taken on a whole new look and feel. Inside is filled with light, especially the bedrooms. But marking out the windows and cutting them was the easy part. Now the edges need to have the outside skin removed for 50mm and the core removed to the inside skin. Then a number of layers of glass (not sure yet, between 6 and 8 ) are laid to create a solid glass frame for the perspex/acrylic to bed to using a combination of double sided tape and silicon sealant adhesive. The combination of this solid frames and the mullions should be solid enough and the structure will be rigid enough. It wont ever be as strong as it was before the windows were cut out, but its getting close. I dont have any structural need for the roof to be super strong. Cats dont have to have a cabin, all of their structural strength comes from the cross beams and bulkheads, as it does on this boat, the bulkheads all have uni ropes embedded in them and each has a uni stack each side of it, so I guess the roof is only really there to keep the elements out. Some boats secure sheets to the roof (main or genoa) ours wont. So the only workload the roof will ever have is if a green wave comes over the top, it must be able to handle the weight of that water until it runs off a few seconds later. That’s the only reason the roof must be up strongly.

I came up with a way to neatly cut the core away. My jigsaw skills are adequate but not exceptional. So I cut the windows a mm or so undersize (I made sure that I did not cross to the outside of the marked lines with the jigsaw and kept the marked line on the boat as the guide for the grinder) and used the 100mm angle grinder to trim the opening to the marked lines or more appropriately to just smooth out all the lines so that the edge looks to where it should be regardless of what the lines indicated, as they were roughly drawn in some places. At the end of the day, the eye is the judge. I asked a couple of friends with good eyes (mine are not that great, nor is my ability to judge fairness all that good) to check them out. Both found little places here and there where they were too high or low. I fixed one by grinding out the window a little more to make it the level it should have been to match the other side and its neighbour. The other I needed to lift 10mm. I did this by glassing the inside skin back up so that I had a 10mm overhang into the window opening and then not decoring to the original line but 10mm shy of it the new window line is the corrected one.

On the glassing on the inside, I have already decored the cockpit to saloon windows which were pre-cut in the kit. I did not glass the inside around the window (the plans dont call for it). What I discovered once I removed the core to 50mm to create the rebate for the solid fibreglass window frame, was that the skin on duflex may well be 600gsm (grams per square meter) but it is pressed into the balsa under pressure and when the other skin and the core is removed there is nothing supporting that pressure and it buckles under it. Either that or it is pressed really thin, so thin it loses its structure once the backing core is removed. Either way the result is the inside skin is now wavy. I have to get that wave out before I can glass the window frame in because it goes in one layer of glass at a time and follows the form of the substrate, in this case a thin wavy layer of glass. Each layer keeps following that form. If I was making the frame off the boat and glassing it in (another option that was going to be the way I did my windows) this would not be a problem but doing this way it is. I will most likely fix this by hot gluing a flat board to the inside skin to flatten it out before glassing in the frame layers.

But in the meantime to ensure that this does not happen again I have glassed each of the windows around their inside edges for 100mm and put down a layer of peelply. This had a couple of added benefits. First off it solved the issue of the wavy glass. It also gives the inside of the glass another layer of strength, cant hurt right. It enabled me to glass the 10mm skin overhang into the window to re-align it. And with the peel ply on it is a nicely finished edging ready for paint or bog  (I had not previously applied any peel ply so I had to grind the inside of each window before glassing, not super hard, but an extra hours work I now wont have to do again).

Here is a picture of the rear window wavy glass and of the side window with extra layer of glass. Massive difference. You live and learn.


The method I used to decore was after cleaning up the inside edges of each window to the point where I was happy with the opening size, shape and position I used that edge as the former for the outside edge. This was achieved by using a router with a fence made from a bolt with washers on it, through a rail attached to the router. My router does not have a fence so I borrowed Terry’s, and it worked a treat, thanks Terry, makes up for the piece of crap laser level you tried to foist on me! This bolt and washer fence controlled the router blade so that it could not penetrate into panel any further than the exact 50mm that the edge of the washers was set to. The round shape of the washers also enable the router to negotiate the rounded corners and neatly replicate them like a spirograph. I set the depth to just above the inside skin knowing that I would have to clean just a thin layer of balsa from the skin, but this is safer than cutting it too fine and going through the inside skin.

Once I had the inside line cleanly routered, I used that router to take a little more of the core out closer to the edge to reduce the amount of hand clearing with a chisel. Of course you must do the inside router cut before removing any of the rest of it, because without the core at the edge of the window the router fence has nothing to control the cut. On that issue, you need to be careful, especially if your fence is only a bolt (I only added the washers because I could not get the bolt closer than 60mm and I needed only 50mm so the washers were originally only to add that 10mm) that your router blade is not bigger than your fence bolt otherwise there is nothing to stop the bolt as you remove the core from in front of it as you cut in, the way to stop this happening is to go in on an angle rather than at 90 degrees and to be very careful not to fall into it when you complete the cut as you come around the other side. I forgot this and the rounded edge of the washers protruded into the hole cut by the router a little creating bumps here and there that I needed to sand out later.


Routers scare me a little, they make a screaming noise and can very quickly make a mess of the job if they are not well controlled. A fence and the depth correctly set ought to alleviate the fear. It doesnt much. And ironically they make a mess with the waste they create and its almost impossible to add a dust extractor to them, they like an angle grinder work at such velocity that the parts have flown away from the reach of the vacuum before it can catch much of the waste. I cleaned up the boat before I did this work because I had some visitors the weekend before (just after cutting the windows I have had a few visitors, most of them at my invitation to show them the massive change that has happened by cutting them out) and the boat was cleaner than it has been for at least 6 months. It is now dirtier than it was the day I cleaned!


With the bulk of the core and outside skin removed by the router I proceed with a chisel (and hammer but you dont need much force) to remove the rest of the core. The glass that is still left is not attached to anything but the core that remains so it is fairly easy to remove. I prefer to proceed and finish with a chisel because its hard to do much damage with a chisel, but if you slip with the router (which gets increasingly likely as the core is removed), its the core that is stopping the router base from allowing the blade to travel too deep and break through the inside skin and the core edge that is touching the fence that stops it penetrating further than the distance set on the fence so without the core there its completely freehand and easy to slip creating holes in places you didnt want them to be and  its easy to cut a swathe through areas you dont want to  but with a chisel it takes a little longer but you are safe from making any major slips. So having got this far without mishap I prefer to bank my wins and proceed with caution. The outside edge cut with the router is very neat, the inside skin has not been compromised so all that is left is to remove the rest of the unwanted core with a chisel.

I use a combination of a blunt chisel to remove the chunks of core by tapping it with a hammer then a sharp chisel pushed by hand to clean the last of the balsa from the skin. When using the blunt chisel you want to use it with the blade upside down. If the blade is right way up it naturally wants to cut deeper with each tap of the hammer. With an upside down chisel its natural tendency is to return to the surface. With the chisel close to the inside skin and right way up its possible for the chisel to catch an edge of glass and cut its way through the skin. I caught this one before it got through the added skin but it did cut the original skin for an inch or so. Not a big problem but you want to avoid unnecessary work where you can and simply turning the chisel over wont hinder your progress in getting rid of the core but will help you avoid cutting the skin.


Once all the balsa is removed I run a sanding disk over the skin to just ensure there is no dags of glue or balsa left and to ensure the surface is keyed so that the glass layers I put on will bond well. I than ran a router with a rounding bit in it, around the corner of the balsa to round the edge s0 that the glass tapes I apply dont have to go around a sharp corner. A cove in the inside skin to balsa wall will complete the transition of the glass from inside skin to outside skin.


With the outside skin and core removed the inside skin becomes translucent and gives off an interesting effect as if it glows from the outside light being visible through it. Once the 5mm of solid glass is attached to it this effect will disappear and will be further removed when the perspex or acrylic window is siliconed to it. The silicon is black and it fills the entire void to about 30mm deep and 5 mm high between the skin and the inside surface of the window. I am not sure if they do any other color sealant, I have only ever seen boat windows done with black sealant.

The de-cored edge is 50mm wide but 5mm of that will be lost with the solid glass frame I glass in (one layer at a time) and then another 5mm or so will be lost when final trimming of the new edge is done. It will be almost impossible to glass the strips on and have that edge be perfect just from the glassing process so there will be a grinder employed to straighten that edge up and round it smooth. That will trim the overhang down to 40mm. When the perspex/acrylic (I use the dual term because I dont yet know which I will fit, I still dont fully understand what if any are the differences, I dont even know if I will use clear or black tint, all that investigation comes next) is made it is made 10mm smaller than the overall opening, which will leave a 30mm bonding surface. The window pane must have a 10mm expansion area as it can grow as much as 5mm in any direction as it heats in the sun and then contracts again each day. And you need to choose the right sealant that allows for such movement. More of that later when the windows are made and fitted.

In the meantime, I have found a new app for my phone camera that automatically stitches photos together to create panoramas. It can do a full 360 degree pic that stitches to itself and the viewer on the phone allows you to scroll around as if standing in the middle of the boat in an endless photo. Unfortunately I dont know how to post them as an endless looped photo on here, but if you click on the panorama’s below they blow up to a bigger pic than the screen allows and you can use the scroll bar across the bottom to replicate the effect to a degree. The stitching isnt perfect but its pretty neat, dont you think?

Jo has been telling me that I should not be posting super posts that take a day to read through but small bite sized snipets. So maybe I might get back into the habit I had at the start of regular small update posts. I just felt with some of the fiddly furniture build that there really wasn’t all that much progress to report but now that we are getting close to the finish, the boat will change appearance with some of these posts. Todays post was more about the panorama pics I discovered I could take!

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