Oratex covering.
Posted: Tue Apr 27, 2021 10:39 am
Does anyone here have a lot of experience of Oratex?
I’m trying to cover my SSDR microlight with Oratex 600 but it’s difficult to do and I’m in two minds whether to continue with this material. I would welcome your experience and input. I have so far covered the tail surfaces which are 1” Al tube.
To illustrate the problem I’m having let me give a couple of facts that appear contradictory;
The Oratex Hot-Melt-Glue is activated between 50 and 100 deg C. The fabric shrinks at temperatures between 100 and 200 deg C. It shrinks by 1% (of fibre length) for every 10 degs above 100 to a max of 10% shrinkage at 200 deg C. Quote>> “150 °C (302 °F) for more than 5 sec initiates adhesive cohesion failure” so there is a temp above which I dare not go when wrapping the fabric around the tubular frame.
All of the videos that I’ve watched on Youtube have shown the use of a heat gun at much higher temperatures than that sustainable by the glue. All my attempts with the calibrated iron at temp up to 130deg C have resulted in poor wrapping around curves and corners. In these circumstances the overlap between top and bottom surfaces is much less than that demanded by the manual. As you can see 130 deg C means a max of only 3% shrinkage around a metal tube curve.
Despite being a woven fabric Oratex will not “drape” in the 45deg direction. It appears that the
coating fixes the warp and the weft to be perpendicular to each other and prevents any draping (in which the warp and weft fibres cross at a more acute angle). Heating the fabric shrinks the warp and weft uniformly and does not seem to alter the crossing angle.
My (amateurish) analysis of the path taken by the individual fibres when wrapping around a curve leads me to believe that it is not possible to wrap around more than a 45 deg change of direction of the tube structure. In my experience of trying to wrap around 90 deg curves the fabric will not lay flat much beyond the centre line of the tube.
TLAC who are the source of Oratex in the UK normally run training sessions for prospective purchasers but this is understandably not possible at the moment.
Any thoughts or advice you have on this are welcome.
Laurie
I’m trying to cover my SSDR microlight with Oratex 600 but it’s difficult to do and I’m in two minds whether to continue with this material. I would welcome your experience and input. I have so far covered the tail surfaces which are 1” Al tube.
To illustrate the problem I’m having let me give a couple of facts that appear contradictory;
The Oratex Hot-Melt-Glue is activated between 50 and 100 deg C. The fabric shrinks at temperatures between 100 and 200 deg C. It shrinks by 1% (of fibre length) for every 10 degs above 100 to a max of 10% shrinkage at 200 deg C. Quote>> “150 °C (302 °F) for more than 5 sec initiates adhesive cohesion failure” so there is a temp above which I dare not go when wrapping the fabric around the tubular frame.
All of the videos that I’ve watched on Youtube have shown the use of a heat gun at much higher temperatures than that sustainable by the glue. All my attempts with the calibrated iron at temp up to 130deg C have resulted in poor wrapping around curves and corners. In these circumstances the overlap between top and bottom surfaces is much less than that demanded by the manual. As you can see 130 deg C means a max of only 3% shrinkage around a metal tube curve.
Despite being a woven fabric Oratex will not “drape” in the 45deg direction. It appears that the
coating fixes the warp and the weft to be perpendicular to each other and prevents any draping (in which the warp and weft fibres cross at a more acute angle). Heating the fabric shrinks the warp and weft uniformly and does not seem to alter the crossing angle.
My (amateurish) analysis of the path taken by the individual fibres when wrapping around a curve leads me to believe that it is not possible to wrap around more than a 45 deg change of direction of the tube structure. In my experience of trying to wrap around 90 deg curves the fabric will not lay flat much beyond the centre line of the tube.
TLAC who are the source of Oratex in the UK normally run training sessions for prospective purchasers but this is understandably not possible at the moment.
Any thoughts or advice you have on this are welcome.
Laurie