Oratex covering.

The place to raise issues, ask questions, swap ideas and discuss anything related to aircraft engineering, maintenance and building.
NB Any opinions expressed in this forum are not necessarily those of LAA Engineering

Moderators: John Dean, Moderator

Post Reply
lauriehurman
Posts: 6
Joined: Fri Mar 23, 2018 5:39 pm

Oratex covering.

Post by lauriehurman » 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

skelly
Posts: 17
Joined: Tue Nov 27, 2018 9:15 pm
Location: Derbyshire

Re: Oratex covering.

Post by skelly » Fri Apr 30, 2021 2:42 pm

I can't really help much but I have been looking at Oratex myself.
The conclusion that I arrived at was:

I'm a complete amateur at aircraft covering, so I will use the cheaper stuff ie polyfibre.

I'll be following this thread as I may learn something.

Cheers,
Skelly.
Jon Skelson
043254

lauriehurman
Posts: 6
Joined: Fri Mar 23, 2018 5:39 pm

Re: Oratex covering.

Post by lauriehurman » Wed May 05, 2021 9:13 am

Hi Skelly
Can I suggest you look at Stewart Systems. It's a water based version of the traditional paint-on system rather than using noxious solvents.

I have no direct experience but I'm thinking of going that way for my wings.

Laurie

skelly
Posts: 17
Joined: Tue Nov 27, 2018 9:15 pm
Location: Derbyshire

Re: Oratex covering.

Post by skelly » Tue May 18, 2021 10:54 pm

Hi Laurie,

I looked into the Stewart system but I settled on Polyfibre as the guys at Aircraftcoverings who sell this stuff are absolutely spot on and have been really helpful.

https://aircraftcoverings.com

Also it does seem to be the preferred system among many people so I thought, yep, that'l do for me.

The chemicals smell nice too..

Cheers,
Skelly.
Jon Skelson
043254

Ian Law
Posts: 200
Joined: Wed Jan 02, 2008 11:00 am
Location: Devon

Re: Oratex covering.

Post by Ian Law » Wed May 19, 2021 5:16 pm

Can't help with the problem you have described Laurie, but I shall be very interested to follow your post.
I'm hoping to use Oratex 600 for the flying surfaces on my biplane project, mainly to save weight and perhaps a bit of time as well. Some mods. to the design I'm building were quite properly required by the PFA, but have added some weight.
I am considering using the Stewart system for the fuselage, only, to simplify various aspects. Light Aero, who are local to me, also support Stewart products now, which is a big help.
I assume TLAC may now be in a better position to advise? ( I hope so! )

Ian

wheelbarrow
Posts: 5
Joined: Sat Sep 19, 2009 9:01 pm
Location: Grantham

Re: Oratex covering.

Post by wheelbarrow » Wed Jun 09, 2021 8:59 am

Laurie,
I covered my Jodel in Oratex and made a reasonable job of it I think.

It is different and has it's own techniques. I went on one of TLAC's covering courses to get familiar with the methodology.

If you awnt to chat about my thoughts if you are still interested...
07715 455435
Mike Dolphin
Mike Dolphin
023440

Post Reply