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A diffferent approach to covering the Tunnel!


Captain-Dan

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Like anything there are a few ways to do it, depending how thick you want it, I'd either:

Use chopped strand mat, but only one or two heavy gauge layers, then go for progressively finer and finer weight mat to keep as smooth and tight a surface as possible, then finish with a layer or two of surface tissue. You'll still need to sand and fill, but with care and carefull attention to the overlaps you at least reduce it. A good roller will help working the resin in and assist in not overloading it.

Alternatively - trickier, but get it right and it well get you a much better surface/thinner but still strong panel, is to use woven roving type may instead of chopped strand.

A lot of (amateur) aircraft build is done this way, inside out compared to kit cars, as a gel coat onto mould + backing CSM mat isn't always used, instead, they do exactly what you intend and build the covering up from the bottom, ending up with a twill mat surface that can be sanded and painted.

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So thanks to everyone for the pointers and recommendations - it has certainly helped focus my mind and plan. I had placed my order for bits and bobs last weekend so was committed to my choice of 200g woven fabric which I thought was thin enough to retain the initial shape and hopefully light enough to go round the edges. So I arrived back from work on Friday to find a big box of very fumey bits plonked into my shed by my girlfriend who was complaining that it was stinking everything out! 

 

The first task was to use some filler to smooth out the indents where I had screwed in the top piece and generally tidy up the template.

 

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I next wanted to create a barrier between the template and the first layer of fibreglass. Now I know that there are release waxes ect which can be purchased, but I had found an american car building site which suggested using foil was a good solution. So...I gave it a go and covered the entire template with foil and put the first layer of fibreglass on. What a mistake!!! The problem is that the foil lifts from the template and makes a roller coaster of a finish on the fibreglass. So this was quickly lifted off and went in the bin! 

 

Next up I tried parcel tape and sprayed WD40 on to assist with removal. This gave a much tighter wrap of both tape and fibreglass to the model. 

 

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The tricky bits were the top corners where the fibreglass wanted to lift away on top and just below. I wanted a slightly rounded finish so I wasn't too worried as long as it was close enough. I let this first layer dry completely before adding a further 2 layers. 

 

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I then went ahead building up the layers in 2's, smoothing out any excesses of resin or high spots between double layers. I tried not to add too much resin (just enough to wet out the fibre fully) to avoid building up high spots.

 

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I also aded a pencil line under the layers (can be seen just at the bottom of the above picture) which will eventual become the cut line along the side of the piece. For the moment it is providing me the line which I need to glass down to.

 

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Piece trimmed and smoothed down ready for final single layer of fibreglass, which I have stuck on - but didn't take a picture of yet. I will put one on later. I am really pleased with the results so far and the finish (although the pictures do not seem it) is pretty smooth. By eye and touch it feels like a consistent surface, which with more work should be really good.

 

Today I am going to start with the filler to fill in any low spots and weave pattern. I will then sand down any areas to try and get the finished shape ready for the skinning process. I just ordered the skinning products this morning so hopefully they should arrive early next week. I have gone for a black and red carbon 3k twill from Easy Composites which I think should look good with the current colour scheme of my car. 

 

Anyway - thats all for now. I will provide another update soon.

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You've used the woven twill, so don't need the staggered range of sizes you do with chopped strand mat.

It's harder to work with, but gives a much better surface finish as standard, even without adding a layer of surface tissue. With some sanding and a light fill of the low spots, it should be able to supply a top class surface* without being monstrously heavy.

*ready for painting, or some other cosmetic treatment.

Great work though!

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So I managed to get the filler spread on, sanded off and the final shape of the piece cut to shape/size. I also go the holes cut for the gear and handbrake and it fitted for size into the car to make sure it fits. 

 

I am now waiting for the gaiters and skinning stuff to arrive before I continue. However I am really pleased with the results so far and the finish is really good - so should give a great finish I hope.

 

Just 1 photo I am afraid. I was covered in dust so left my phone in the house.

 

IMG_1976.jpg

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Just be aware that the fabric might just end up looking more of a wine red/burgundy when wetted as the coloured fabric mixes do tend to darken from their dry state.
I've used that particular fabric previously and it does have a tendency for the weave to shift quite easily, so very careful handling is required.

 

I'd certainly recommend doing a little test piece to begin with just to see how the fabric will behave when positioned and brushed over.

 

If you do find the coloured fabric a bit 'loose' and prone to distortion and end up opting for a 'normal' carbon fabric, the 'Pro-finish' cloth that EC sell is great for most skinning jobs, as the light resin binder in the fabric holds the weave together. This makes handling and subsequent resin application a touch more forgiving. The only downside is that it doesn't drape quite as well, so worth considering laying down two or three separate fabric pieces with an overlap where the angles change on top, which might also help with neatly covering the sides, but testing it on the shape first will let you know if it will lay down well in a single piece

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