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Carbon Fibre Telescope Finished


paul11

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Er- yes please do post images of how it was made. I have only found one other series on the weob on how to make a plastic tube. I would really like to see -

What method you used for laying up the tube and trimming the end

How you created the reinforcing end rings and any internal baffles.

If you moulded the end plate for the mirror cell, or the mirror cell on its own, what methods you used to cast the shape.

what wall thickness you went for ?

Whether you used inserts in to the fibre or just drilled later.

Lots of questions!

Cheers

Mike

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A wonderfull piece of graftmanship I must say Paul. You must be really proud of the end result. Can't wait to read all about how you built it, and your 1st light report. Here's hoping the weather changes for you, and soon.

Andy

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Thanks again for all the great comments, I will answer a couple of your questions and then I will explain how I made the tube and mirror. First of all I did grind the mirror, it is made from a 25mm x 200mm float glass blank. The glass blank came from Galvoptics in Basildon Essex. Mike (Skybadger) I will answer all your questions with images over the next few posts.

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I guess most people want to know about the C/F tube first so here we go. I have never worked with C/F or made anything like this before, so before I attempted a full size tube I bought a 0.5sqm of C/F and made a small tube. After I had made the small tube I had learnt how to work the glue into the C/F and never to drag the brush of the edge or you will pull out the fibres and you can’t put them back in. If anyone is thinking of making a tube I suggest you make a small one first. Here’s an image of the small tube it’s only 225mm x 75mm.

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Now for the real one, this cardboard tube is 1.4m x 240mm OD, I did split this tube from end to end and removed a strip 10mm wide and then replace it with a piece of wood flush with the outside. (sorry no images of this). The idea was that after the C’F was finished I could punch out the strip of wood and collapse the cardboard tube inside and remove it in one piece. It was a good idea but It didn’t work very well and still ended up tearing the cardboard out in many pieces, but it did come off the C/F very clean. In the first image here you can see the cardboard tube with 6 coats of release agent (should of used 10 lol).

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I rolled out the C/F and made sure the pattern ran good lines all the way across. The C/F is 1m wide and I cut it 1.3m long. With a good set of scissors the C/F is very easy to cut. I put masking tape across the C/F and then cut down the centre of the tape, this stops any fibres coming out.

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This is the first layer of C/F on the tube. I coated the tube in Epoxy Resin first and then rolled the C/F around the tube working more E/R in to the surface with a 50mm brush to make sure it was fully saturated. Then I covered the C/F with peel ply as you can see in the first image, the next day I removed the peel ply, second image.

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In the next two images you can see the 2nd layer of C/F going on, again I coated the coremat in E/P and put the C/F on the same as I did the 1st layer. I let this layer dry overnight without any peel ply on it as I wanted a high gloss finish, if you put the peel ply on the C/F it will give a matt finish. I did intend this layer to be the finish layer but when I looked at it the next day I could see the white from the Coremat through the C/F so I had to put on another layer of C/F to hide it and then it looked fine. As you can see in the next 2 images it’s really important to set out the C/F straight/square/parallel to the tube, if you start out like this that’s how you will finish up.

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After the final layer was dry I applied another 3 coats of E/P to make sure the C/F was well under the surface. Then it was outside on the patio with a bucket of water and wet n dry to cut down the surface to a smooth even finish. I started with 240 grit and finished up with 1200. Last post for tonight guys I will post more tomorrow,,,,Paul.

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