Cracks around windscreen

[Guest battle]

Hey Guys,

 

I have an early jab LSA 55 built in '93, it has the cracks in the corners of the windscreen like all the early ones seem to get (i am told). Anyway i want to repair them just for the cosmetics and was curious if anyone else has done it. My plan was to mask the winscreen and sand the paint off the cracks and fill them with resin, then smooth that off and touch up the paint. Any suggestions?

 

Thanks Dan

 

 

[Captain]

Dan,

 

That is just about what you do when you build one from a kit, and I would suggest that you access one of the build procedures from the Jabiru website and read up on the full procedure that they set out for attaching windows.

 

If you can't find that, let me know and I'll send you a copy of that section for the J230 manual.

 

With mine, I went to a fair bit of trouble with resining the windcreen to the fuselage, then filling the gaps with resin and filler and mine hasn't cracked around the periphery in almost 2 years of use (2 down and 13 to go to match yours).

 

If it looks like your screen might need better bonding to the glass of the fuse in any area, you might consider getting some further advice on how best to perhaps drill a couple of holes into the gap between them and injecting some resin ..... but one of the key things about the initial bonding is to rough up the surface of the plexi to make sure the resin takes well.

 

Hope this is of some help.

 

Regards Geoff

 

 

[hfrensch]

The problem with repairing the cracks is that they will appear again because the windscreen sits on a bed of sealastic and held in by screws. There will always be some slight flexing movement. The best way to hide the cracks is to use white viynal tape same stuff as used for the striping. A pernament fix would be to remove it and fibre flock it in.

 

Cheers Helmut.

 

 

[Ross]

My J160 kit was number 14 and I presume they are scaled up versions of the LSA55 with some obvious changes.

 

One of the mandated jobs that had to be done by the kit builder for my kit as specified by Jabiru was to reinforce the wind screen pillars on each side of the windscreen and also down the backside of the door openings.

 

These reinforcements consisted of a thick strip of FRP alongside each windscreen pillars with extra glass layers on top and multiple layers of glass strips from the back of the door openings across to the next rearwards whale bone in either two places I think or maybe three. The effect on the windscreen pillars was to convert them into a more rigid closed triangle section with the windscreen lip along one corner of the trianglular section.

 

All these reinforcements would all probably contribute to the stability of the dimensions of the windscreen space under varying loads.

 

 

[Captain]

The problem with repairing the cracks is that they will appear again because the windscreen sits on a bed of sealastic and held in by screws. There will always be some slight flexing movement. The best way to hide the cracks is to use white viynal tape same stuff as used for the striping. A pernament fix would be to remove it and fibre flock it in.Cheers Helmut.

If, as Helmut advises, the early ones had the window attached via Silastic & screws, then ignore my post #2, unless you remove the screen.

 

 

[facthunter]

Stresses in screen

 

If you can repair the screen with resin would it be better to drill a small hole at the end of the crack first? this is the normal procedure in metal as well as window material, and helps to stop the crack spreading. Normal airframe flexing will tend to produce cracks eventually, especially if tight screws are used. Is the window a part of the structure in a Jabiru? Nev

 

 

[Guest battle]

Thanks guys,

 

I found that mine is actually held in with sealastic so i have no chance of stopping it and have decided to pull it out and flock it in like the newer ones and see how it goes,

 

 

[Derby]

Hi Facthunter.

 

Yes the front window is a part of the structure. (it is on a J400 anyway).

 

Rory

 

 

[icebob]

Hi,

 

Had an issue with a couple of screens where there was star cracks around the attachment screws, it appears that 4mm bolts/screws were used and the screen holes were 4mm not 4.5mm to allow for the screen to flex/move.

 

I am aware of your issue is the frame but it would be a shame to fix that and then get star cracks after going to all that trouble.

 

Bob.

 

 

[Guest Maj Millard]

It is common in the industry to drill screw holes bigger than the actual fastener in windscreens. That way stress is not being transferred to screen so much. It works !!.