RV9 tip up canopy *frame* cracks

[Martino]

Hi all;

After a great flight the other day I sadly spotted various cracks around the canopy *frame* on our RV9 tip up

We’d previously noticed the gaps increasing between the frame and fuse but only just spotted these cracks - they must’ve been there for a while it seems

There are two cracks, both in existing factory welds. One at the hinge where it has a flange welded onto it to rivet to the frame. This seems to have been a common issue on RV6 tip ups, but ours is an RV9 with the stiffeners fitted. The other crack is in the weld towards the rearward part of the frame assembly

I’d like to ask please -

1) Ideas for repair solutions please? This forum and Vans themselves said weld - but the two approved aviation welders we’ve approached both independently said the material can’t be welded. I saw a bolted solution for the hinge repair on the RV6 thread but what about the rearward issue?

2) I really feel like this must be a common issue but am surprised how little information there is out there about it. Surely we can’t be the first RV7/9 tip up with stiffener with this issue?

3) Has there ever been an RV6/7/9 tip up canopy failure in flight, either at all, or specifically did this issue? I haven’t been able to find any evidence

4) Vans said to remove the Perspex to weld. Has anyone ever removed the Perspex from their canopy then reused it? (What do you do at the Sikaflex fillet etc?)

Any and all advice and info gratefully received please…

Thanks to all

 

[Snowflake]

Ouch, sorry to see this. Mine was the -6 that failed and was repaired with a bolted connection. It's still flying strong 10 years later. Did Van's admit they had seen this before when you asked? Because when I reported my failure they said they had never seen it before.

When you get it apart, you'll probably find the same thing that I did, that the weld doesn't penetrate the metal far enough to create a strong joint. Mine looked almost like someone had laid a bead of JB weld in the corner, the entire mating faces were as-machined with no weld penetration.

My canopy bubble was held on with screws and nylock nuts, so I was able to remove it and re-use it... One argument against using Sikaflex, I guess.

 

[Ralph Inkster]

Sorry to say, I would see how ‘approved’ aviation welders would shy away from a job like that. Try approaching custom aluminum or automotive fabrication shops, you might find the right guy that would take on the challenge.
Real aluminum welders are artists.
Look into the possibility of leaving the plexi in place by packing insulation (wet towels or similar) to protect it during the welding process.
I once watched friend weld a tab onto a longeron tube on a finished plane, within 1/2 inch of the fabric covering without even discoloring the fabric! Weld area was well protected with wet rags.
Last thought, look into the probable causes of those cracks. Is there a twisting motion happening when the canopy is being lifted? Are both lift props lifting equally, or is one a bit weaker than the other.
Good luck

 

[Martino]

Ouch, sorry to see this. Mine was the -6 that failed and was repaired with a bolted connection. It's still flying strong 10 years later. Did Van's admit they had seen this before when you asked? Because when I reported my failure they said they had never seen it before.

When you get it apart, you'll probably find the same thing that I did, that the weld doesn't penetrate the metal far enough to create a strong joint. Mine looked almost like someone had laid a bead of JB weld in the corner, the entire mating faces were as-machined with no weld penetration.

My canopy bubble was held on with screws and nylock nuts, so I was able to remove it and re-use it... One argument against using Sikaflex, I guess.

Thank you for the reply. Definitely looks like your bolted solution is a potential route forwards

 

[Martino]

Sorry to say, I would see how ‘approved’ aviation welders would shy away from a job like that. Try approaching custom aluminum or automotive fabrication shops, you might find the right guy that would take on the challenge.
Real aluminum welders are artists.
Look into the possibility of leaving the plexi in place by packing insulation (wet towels or similar) to protect it during the welding process.
I once watched friend weld a tab onto a longeron tube on a finished plane, within 1/2 inch of the fabric covering without even discoloring the fabric! Weld area was well protected with wet rags.
Last thought, look into the probable causes of those cracks. Is there a twisting motion happening when the canopy is being lifted? Are both lift props lifting equally, or is one a bit weaker than the other.
Good luck

Good info thank you. Will look closer at the struts. I’ve seen comment elsewhere about fitting stops to prevent the struts loading the frame when the canopy is down