Slippery Anne update

[Mark Atkinson]

Hello Paul,

I suspect that the methodology of attaching, tightening and doping linen is a subject not usually covered in motoring forums! 

I have used linen which is manufactured today to the British standard of the inter war period. it is attached to the structure by glueing, for which there is a dedicated adhesive, I chose not to use this on the car. I simply used the clear Nitrile Dope that was also used to paint the fabric with.
As you will see in the attached pictures a paper paternities was made for the linen, which was then laid out on a clean floor for marking up and cutting.

The cut linen is then offered up to the structure, trimmed and once the desired fit is achieved, all the edges are frayed, a relatively easy but tedious task of teasing out the fibres. On an aircraft linen tapes with frayed edges are used to strengthen edges and across ribs and stringers, I did not do so on Slippery.

The edges of the linen are then glued to the structure whilst pulling it as tight as possible. Once this is dry and secure the linen is thoroughly  wet with distilled deionised water, which as it dries shrinks the linen. then after it has dried repeat. 
At this point the linen is still not tight, but the first coat of Nitrile High Tautening Dope with 25% thinner is applied with a cut down brush (about 1" is perfect) used to work the dope into the linen. subsequent coats are not thinned and are applied until the dope has filled the weave. By this point of the processes the linen is drum tight.

on an aircraft, such as a Mosquito, the plywood skin is not normal covered in linen, Cotton Madapalin is the material of choice, but, for Slippery Annes her plywood skin areas I could see in the period pictures they had used linen on Slippery, so his is how I did it.

Irish Linen has excellent tensile strength, but has several disadvantages, particularly that it is damaged by UV, so she will need to have a coat of Silver Dope to protect it, which will be done with a Butyrate dope, Butyrate is less flammable than Nitrile, but not as effective at the other things described above, so the combination of materials is the way to do it.

Thats about it, there are modern heat shrink fabrics which require no dope which are easier, cheaper and fire proof,  but they just look wrong on period aircraft and on the odd occasions you see them, on fabric covered cars.

Regards, Mark.


               
  5306D90C-7E0B-4F35-9B63-412C552CB55C.jpg (Size: 299.41 KB / Downloads: 570)
  D7443F4E-8D47-49D9-8C1D-7076FC5BC541.jpg (Size: 189.7 KB / Downloads: 572)        

[Ivor Hawkins]

Absolutely fascinating and great work!

[Erich]

Most impressive, Mark. Your attention to detail deserves a lot of praise. I'm fascinated by the similarities and differences of covering with the linen and the canvasing of wood and canvas canoes. In the latter, which I have done, the structure is more robust, but still flexible. An envelope of sorts, is made of the canvas with the wooden frame within it. A "a come along" winch is used to pull the canvas tight around the wood. The canvas is then tacked to the gunnels and stems. A torch is used to burn off the fuzz off the canvas surface. A filler is used to create a relatively smooth surface. Traditionally, this was a white lead solution, which had the added advantage of keeping the canvas from rotting, though with obvious health issues. Today, fine silica and latex paint is used. And finally couple of coats of paint. The result is a watertight and flexible envelope. Of course, this system adds considerable weight, accounting for about half the weight of the canoe.

[Paul N-M]

Hi Mark,
Thank you for taking the time to explain is so much detail. Very interesting indeed.
I am aware of modern heat shrink coloured material for light aircraft frames but I take your point re period looks.

Regards,

Paul

[Jays]

I’ve always loved WW1 aircraft and their construction and I’m finding this all very fascinating.

[Mark Atkinson]

Hi Eric, It is interesting how similar the approach is/was! Of course given that this is an aircraft covering method, it is very light weight. The practice on aircraft is also to make a linen bag with stitched seams, I chose not to do this on Slippery as it is pretty clear in the period pictures the they chose the more direct and less finessed option I described above, If I remember correctly they called it 'bed sheeting', but that may be wrong!

All the best, Mark

---

Thank you to all for your kind comments.

I have gone ahead with the Castrol D140 for the rear axel and today for the first time drove the car, amazingly everything worked, albeit, the Mag timing is way out, I have given up on the BLIC, which appeared to be timed perfectly, but just ran out of spark at 4000 rpm. I have put in a Scintilla M4, which hopefully will work better, but, I am rather struggling to make it work properly at the moment.

The plan for the car is to slowly work her up to be ready for Curborough in early May.

It was fantastic to see her out of the garage and in the sun, my first opportunity to stand back and appraise her from a distance as a finished car.

After all the challenges of making the cockpit large enough, she proved to be easy to drive and surprisingly comfortable.

It is a funny old world, sometimes with happy coincidences in it; whilst manoeuvring her on the drive, our Postie arrived with her shiny new Buff Form freshly approved by the VSCC Eligibility Committee, how is that for timing?!

All the best, Mark.

   

[Ian Williams]

She is looking really good Mark, can't wait to see her painted, is the plan still the green from the section of surviving panel? I hope that you eventually upload a video of her in anger for those of us too far way to witness it in the flesh. I still hope that I might get the opportunity to visit in 2022 possibly even bringing my own car, but the costs and logistics of that may be prohibitive.

[Erich]

Mark, I'm curious if the doped fabric adds some stiffness to the frame. In the case of canoes,, the fabric is only attached at the gunnels and stems. The result is that the canvas and frame act as two separate units. I have gone over rocks and watched the bottom of the boat flex and found only a slight scratch on the canvas. Sometimes, W/C canoes are covered with GRP in order to eliminate the work of recanvasing. But this results in a stiffer boat with the consequence of more damage occurring to the frame and canvas in rapids. In a car, I would expect that the fabric could add stiffness to the body, which would be an advantage. Any idea of the finished weight of the body? As I recall, some early Austin Seven racers(Gordon England) weighed in at only 40 pounds.

[Mark Atkinson]

Hello Ian,

Yes, that curious almost apple green on the surviving panel is my plan, probably not during this season though. I am also thinking of making a second, long tail, body, which if I do one or the other will be left in the clear doped linen, probably just for vanity, but I really do like the look.

It will be great to see you in 22, and if it works out, fantastic to see your car over here gracing the paddock.

All the best, Mark.

---

Hello Eric,

Doped Irish Linen coverings are really quite flexible, and also subject to rapid variations in tension due to temperature and humidity.

If you look at the wings of a modern airliner, you will see the considerable amount of 'flex' they go through, aircraft have always needed to deform in this way, in the early days of aviation, they also often used 'wing warping' as an alternative to hinged ailerons (flaps if you like) to induce roll by differentially altering the lift from the wings, this was achieved by taking additional advantage of the coverings flexibility - flight control and a resilient flexible structure all in one!

In respect of the weight, I did not weigh it, but guess about 30 lbs is probably about right for the wood frame, I did use mostly Ash for the structure, so that has possibly added weight. I am just looking at my phase two job of building a 'long tail' body for Slippery, my intention is that I will use Silver Spruce, with just a small amount of Ash for critical areas of the structure, such as attachment points. I imagine this approach will save several pounds of added lightness, of course the body of Slippery Anne is much smaller than any GE, save perhaps the JoJo cars!

All the best, Mark.

---

   

[Austin in the Shed]

Looks a fantastic job Mark,Hope to see it in the metal,or wood at Curborough.