Thursday, 10 September 2015

Humber Speedster Project - Update # 11

The last sentence in my previous Blog entry was, 'The next job is fitting the sheet metal skin – Yikes!’. Well like most of my well laid plans it didn’t quite go according to plan. What seems to happen is that I intend to start a certain project but get side tracked and do something else, which doesn’t really worry me as it all has to be done sooner or later. While I was waiting to have the 15 mm lip folded on the sheet metal side panels by a sheet metal shop, (I was going to do them myself until I found my folder was too short and I couldn’t slide them in from the side). I started to plan the fuel tank cradle and trunk, I had not given this much thought up until now as my main concern was getting the front of the car planned and started. But after sitting beside Hubert and seriously thinking about the look of the back end of the car would really have an impact on the overall look. Maybe this is why a lot of pre- 1920’s cars I looked at have an awkward look about them in the rear section, like the builders realised, like I did, ‘damn, we really didn’t think this through, what do we do now?’ In the initial planning stages I had briefly thought of a boat tail end, but on investigation it was a LOT of work, so decided on a basic exposed fuel tank and attached trunk.  OK, back to me sitting beside Hubert wondering what was I going to do??? This was the time I took a leaf out of Svenja’s book and ‘let it speak to me’, which is an tenet she uses when designing her wondrous costumes.  A trip to the hardware to check out what timber I had to play with and what would suit. I guess the sight of me standing there with a sheet of paper in hand and a thoughtful look on my face it was inevitable I was going to be approached by one of the helpful staff.  ‘Can I be of service?’ asked a fresh faced young lady, I hesitated just for a millisecond about whether I should ask her if the sheet on ply I was looking at would be suitable for skinning the trunk of a 1916 Humber Speedster…… but decided to say, ‘no thanks, I’m OK’.
While I was perusing all the different timber products I formed a plan… yes another one ;-)  I’d use form ply for the structural parts, sides and supports then pine boards for the floor, topped off with a plywood top cover.

Making up as I go along

Trunk ready for skinning

A trial fit for of the ply wood skin.

The fuel tank cradle was fairly straight forward, the shape and size dictated by the tank side, (a re-purposed automotive LPG tank). The sides of the trunk took some design time with my co-designer Svenja with her talent at drawing curves she soon had the drop away to the rear of the chassis sorted. I had decided to make the floor out of 19 mm (3/4”) solid pine in various widths with the edges cut at angles to follow the contour of the chassis and give a sealed surface, much like barrel staves. It was then onto the ply wood ‘skin’, this had to curve to follow the drop away, so it was ‘Kerfed’. This entails numerous saw cuts made across the grain to a depth just under the outer layer which allows the timber to be bent. Getting the depth and the distance between cuts is important to allow the timber to bend freely but not to crack or show creases. This process works well but also removes a lot of the integral strength of the ply wood sheet so extra supports had to be added to compensate. 

Liam with the top skin.

Kerfing detail

Access to the trunk was also added by cutting the door hole which is supported internally at the edges by form ply braces, the lid will come later.
In between waiting for the glue to dry on the trunk floor the dash board was mocked up using a piece of ply wood scrap the same thickness as the finished piece. 
The mocked up dash

Steering column bracing

 This wasn’t just a matter of sticking a piece of ply up in the scuttle opening, the recess and angle of the dash plus the position of the gauges had to be set to suit the eye line of the driver. This done, along with welding the mounting tags to the scuttle frame, the gauge positions were measured and noted so a holes can be cut in the final ply wood dash after lacquering.

Well that’s about where I’m up to at present, I should cover the sheet metal fixing in the next blog entry – hopefully !

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