Sunday 8 February 2009

Porthole Project

Carpentry Project
Porthole Cover

8th February 2009

These long winter days get you down. I had big plans for January and February - I was going to rebuild the toilet / shower room on Wand'ring Bark in time for its Easter trip, but what with one thing and another I havn't made a start. I have therefore decided to re set my target completion date to the start of the summer holidays and focus instead on something slightly less challenging, which can be undertaken in the relative comfort of my workshop at home.

Last winter I installed a cupboard over the main bunk, complete with an archway over the porthole window, a project which was particularly interesting and to my mind, very successful. As part of this project I constructed a removable pine porthole cover and Belle has suggested something similar would be good on the other side. I mulled over the options for a number of months and finally came up with a design where a circular "plate" of wood can roll back and forth in a channel with undulations in the track to either keep the porthole covered or, during the day, to keep it open.

I cut the disc months ago but never got round to making the rest of the assembly. Well, today with snow lingering on the ground I decided to have a go and, for the sake of posterity, to take a few photos as I went along.

As with most of my projects, I only use a minimum of measurements in a workbook and then design it as I go along, following the classic maxim of making form follow function. For the uninitiated this means that before you make it look nice it has to do the job it is designed to fulfil.

Having cut the disc (41.5 cm - the diameter of the porthole plus the frame) on the bandsaw I routed a rounded edge onto the outside face.

Next I cut a template of one half of one rail (it can be turned over to create a mirror image at the other end), following the curve of the disc and using a paintpot to get the rounded end. I added a marking to this template so it can be reduced later on and help to create the "track" pieces of wood which will be fixed to the rear of the facing strips.

Because the facing strips and the track strips have to be a perfect pair the track blank was temporarily screwed in place and the entire unit was then initially shaped on the bandsaw, then planed / spokeshaved and finally sanded smooth.

With two identical pairs created, the two rear track sections had their grooves cut out, creating an undulating rebate with the top mirroring the bottom. Hopefully this will allows the disc to remain firmly guided as it rises and falls along the track from end to end. For the sake of an attractive finish the edges of the facing plates were also rounded off using the router.

A rear view of the finished item showing the undulating track, awaiting varnishing and installation.

I am not sure how best to fix this to the plywood cabin sides, but I am thinking that three brass picture fixings on each batten would probably be both neat and effective. I will post a photo of the end result in a week or so.


belle said...

Looking good, oh Captain, my Captain!

D Baynham said...

That looks fantastic.

Brian and Diana on NB Harnser said...

Looks good and with that depth of drop at the ends you will need to hit the lock gates quite hard to close them automatically. :-)