Canopy crack and replacement canopy struts

[Bob Redman]

G'day folks,

Over the past month or so our struts have been losing the ability to keep open our tip-up canopy. The struts were purchased from Vans in 2006, fitted in 2010, and have been flying since 2011.

Just as I sat in the right seat (RV-7) a moderate breeze blew the canopy closed. I caught the right side on my upper arm/shoulder, but the left side bounced off the nylon block canopy guide fitted to the front of the baggage compartment canopy frame (bow) at the cockpit longeron rear left.

Now I have joined the cracked canopy brigade. The crack started at the rear most screw left side of the tip-up. The crack is about 100mm (4 inches) long, and parallel to the rear canopy frame.

First action - used plexiglas bit to drill a stop hole.
Second - search Mr Reeves magic treasure chest for VAF corporate advice.
Third - search the web for suppliers to compare price/availability in Australia vs same elsewhere.
Fourth - went for a flight to compensate for the disappointment - no, I did not notice the crack, and it now seems like fair wear in exchange for much fun.

Vans price is US$33 each for the accessory catalogue C-690 struts - Stabilus Lift-o-Mat, PN #752619 rated at 100 newtons. A search of the forums revealed other manufacturers/suppliers in the USA.

Unusually, I sourced a 'home brand' (probably Chinese) equivalent here in Newcastle from Ovesco for AUD$25.70 each (inc tax), Ovesco PN #4060125, 125N x 406mm Gas Stay. I opted for an increase in stiffness from the standard 100n to 125n - ovesco.com.au: in Newcastle New South Wales, and the Gold Coast in Queensland. Ovesco will ship Australia wide, but check first, often freight is cheaper & quicker direct from the US.


Note that I have added bolts to stop the canopy being forced forward by the struts when closing. The stop bolts are fitted to the longerons each side and protrude rearward through the sub-panel. Therefore I am prepared to risk the stronger strut force.

Tomorrow I plan to fit the new struts and then use WeldOn to treat the canopy crack. My plan is to:

1. apply electrical tape to the inside of the canopy covering the crack and stop hole.
2. apply electrical tape to the outside of the canopy covering the crack.
3. use a medical syringe to try to wick WeldOn #3 into the crack.
4. use another syringe to fill the stop hole with WeldOn #16.
5. when all cured, use the micro mesh kit to dress the repair.
6. follow advice from others on VAF and replace struts at the first sign of ageing
rather than procrastinate.

Advice on crack repair welcome.

I hope this helps prevent injury or another cracked canopy.

Regards

[Bob Redman]

G'day folks,

I replaced the Vans supplied struts, and the extra newtons (125 vs original 100) in the replacement struts damp motion and hold position much better than the original struts ever did ( Note: subjective opinion based on memory). I have not noticed any distortion of the tip-up canopy due to the stronger struts - possibly due to the fitted stop bolts preventing the canopy from shifting forward while closing.

I repaired the crack using Weldon #3, and the stop drill holes with Weldon #16, as per the first post. The #3 did not wick very far in the crack, so I applied it along the length of the crack using a fine point syringe while trying to hold the plexi even along the crack while the #3 cured. Then I used a larger tip syringe to fill the stop drill hole with #16. The repair looked adequate.

Following advice on an Australian forum (SAAA - Sports Aircraft Assoc of Australia), I re-did the repair using Acrifix 192 (Acrifix 1R 0192, go www.evonik.com/acrifix-1r0192). The repair was a definite improvement helped by: the lessons learnt using WeldOn; and easier application using the Acrifix tube (think toothpaste) vs the medical syringes used for the WeldOn (pint tins).

I dressed the repair on the outside of the canopy using a MicroMesh repair kit from Aircraft Spruce. The crack is too close to the left rear canopy bow, so I will dress the inside of the repair next time I remove the canopy - probably I would cause more damage if I dressed the crack while the canopy was on the aircraft.

The MicroMesh systems worked well.

Although the crack is obvious to me on the ground, I do not notice it in flight, and can not see it with a passenger in the left seat.

Regards,

[eddieseve]

Hey Bob,

I know this is an old thread, but I have just ordered the same struts, as mine are also on the way our and are not assisting very much in opening the canopy, thanks for the info

Cheers

[Bob Redman]

G'day Eddie,

Glad to hear that the information helped.

I flew last Wednesday for the first time since January - too long !

All well, and the new radio worked.

Regards,

Bob

[eddieseve]

Good stuff Bob, we will now have to try and catch up before Narromine?

Cheers