Hi there,
I am looking at getting some repairs done to my TB20 GT roof section as the paint is cracking around the windows. The paint work is the original from the factory. Being the GT model it has a Composite roof.
I have approached a paint shop who tell me that the rear windows will need to come out to complete the repairs. I am not keen to take them out as they do not leak and it is quite time consuming and costly process to do this. The plane also lives outside and is exposed to the elements, as there are no hangars. Taking the windows out poses a real risk that leaks could occur in the future.
It has been suggested that the cracking is being caused by the roof section itself rather than the paint coating, which is why the paint shop insist that the windows have to be removed. Has anyone had a similar problem with composite and paint. Cirrus operators for example, may have come across this.
Does anyone know how the TB20 roof section is constructed and what materials are used? Is it GRP or Carbon Fibre?
Based on my own experience the different layers would consist of;
GRP – Matting/Resin, Gelcoat, Primer, Paint colour basecoat, and lacquer.
Carbon Fibre – Matting/Resin, Primer, Paint colour basecoat, lacquer.
The main difference being that there is no gelcoat in the carbon fibre system. If the roof section is GRP then it is possible that the cracking could be caused by the Gelcoat and not the paint. However any cracking in the gelcoat or resin systems would I suspect result in a water leak into the aircraft now, and this is not happening. There are no water leaks today and the aircraft is dry.
The repair process for carbon fibre and GRP would be different, one being Epoxy based and the other Polyester, so it is important to establish the original construction.
It is also possible that the failure is in the paint coatings and not the composite. If it is the paint coating then I see no reason to remove the windows.
Any thoughts or suggestions would be appreciated.
Photo attached.
I think that is just cracking paint.
The composite roof is not carbon fibre or anything exotic like that. You can see some pics of the underside surface here and it is some sort of woven material. Socata specialise in these parts. I think it is basically fibreglass with a gelcoat which is painted over.
If your plane is parked outdoors you should definitely get a cover for it. Bruce’s Custom Covers do nice lightweight ones. It also stops people seeing what headsets etc you have inside.
I suspected that it was GRP as it would be more economical in the production process and it certainly does not look like Carbon in your photo. Thanks.
The aircraft is kept covered, although this does act as a moisture trap if the aircraft is not used regularly, as the water runs down aerials and under the cover. I have also heard good reports about Vertigo covers as well.
IMHO UV damage to the paint, the windows, and the sun heating up the cockpit to some huge temperature are the biggest factors.
On the subject of covers, I have a Cambrai cover for my Slingsby which I use all the time (even though it is in a hangar). The main reason is to preserve the canopy, but I bought a heavy duty cover suitable for outside use. I would heartily recommend Cambrai.
I would agree with your comments. Heat and UV damage even in the UK’s climate is a major contributor to this kind of damage. It also does the same to a cover over a number of years. In summer a dark coloured car’s panels can reach 80C when parked in the sun. An aircraft will be similar although we tend to use light colours on the top surfaces which reduce temperatures slightly.
I also had a Cambrai cover for my last aircraft which was very good. Again the elements gradually attacked it, despite it being retreated and repaired every other year. IMHO they last and work well for about 8 to 10 years if maintained properly.
I have just been informed that the composite roof panel is actually Carbon Fibre.
That’s a minor flaw in the paint, i am sure. To get that fixed nicely you’d have to removethe windshield, but i would never do that for THIS, because you’ll damage more than you will fix … Just leave it alone and watch it
Peter wrote:
The composite roof is not carbon fibre or anything exotic like that. You can see some pics of the underside surface here and it is some sort of woven material.
This coarse weave material looks like Kevlar to me: Roof Photo From Peter’s Site The part could be a combination of CF (or anything else) and Kevlar. FWIW Kevlar is commonly used in otherwise carbon fiber composite aircraft where antennas are buried in the composite to streamline the plane.
If that window is bonded into the roof, probably the only way to get it out without damaging the roof is to cut it out with a saw or grinder just inboard of the bond, then grind the plexiglass material out of the frame until reaching the bond line. Then repair the roof, then install a new window. A huge job not justified by the damage shown. Its probably more reasonable to fix it cosmetically with the window left in place.
I have just been informed that the composite roof panel is actually Carbon Fibre.
I saw the post on the Socata group. It may be CF internally somewhere but I have never seen any evidence of the typical black material. Once, at Socata at Tarbes I saw a complicated repair they were doing on a GT whose door was opened in a strong wind and it cracked the roof. They exposed layers of the material and none of them were black. They looked brown to me.
But IMHO the cracks are not “structural”. I have seen such cracks elsewhere on my plane. I would let them dry out and fill them in with an epoxy or some other 2-pack filler.
If that window is bonded into the roof
That is a side window and it is stuck in with silicone, or possibly PR1422. It is designed to be kicked out from the inside (there are placards saying so). So it should come out OK. But not worth doing for this.
