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Side Tipping Canopies - Hold-Open Devices

David Paule

Well Known Member
I've seen three RVs in the last couple of weeks that had ways to keep the canopy from opening too far but none had any way to keep the canopy from blowing shut accidentally if a gust caught it on the ground.

These are all RV-4s and RV-3s.

Isn't this an issue with operating these airplanes? Having flown into plenty of windy airports, I sure thought it might be.

Dave
 
I've seen three RVs in the last couple of weeks that had ways to keep the canopy from opening too far but none had any way to keep the canopy from blowing shut accidentally if a gust caught it on the ground.

These are all RV-4s and RV-3s.

Isn't this an issue with operating these airplanes? Having flown into plenty of windy airports, I sure thought it might be.

Dave
I’ve seen a -4 that had a gas piston that would go over center when closing. No pictures though, sorry
 
Gustbuster geomety

David,
The sexy gas springs I have seen tend to push on the canopy at a location creating relatively high structural stress (canopy closed) compared to cable or string fastened to the left side of the canopy skirt. That said, the simple 2 flat straps with a pivot functions as rope under tension without some sort latch feature requiring pilot intervention to reverse. I am sure can design an elegant solution.
 
I have a simple 2-bar linkage with an off center pivot that goes from the roll cage to the canopy frame on my -4. All made from scrap and 3 bolts. To open you unlatch the canopy and rotate it over. The over center feature keeps it open against gusts. To close, you tap the pivot point upward and fold the canopy over. Simple, cheap and has worked great for 11 years. I'll try to get a photo of it this weekend.
Alan
RV-4
 
Non-pressurized strut/absorber.

On my -4, I installed a non pressurized strut I liberated from an airliner overhead bin door. My particular strut has no lifting capability, but has some damping effect if the canopy is blown closed. It wont prevent closure, but it does slow the slam shut scenario, similar to a screen door damper. I have toyed with making a U-channel that I can put over the strut rod when canopy is open that would prevent closure, however, I'm not a big fan of my canopy sitting open in any wind.
 

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simple 2-bar linkage with an off center pivot that goes from the roll cage to the canopy frame

+1. Had the same manufactured from some angle bar, works perfect.
 
I totally agree with your concerns David - the RV-3 canopy is a pretty big sail attached to a pretty flimsy structure (the hinge). One of the advantages the RV-4 guys have is the mid-cockpit roll-over structure - that grabs the canopy in the middle of the hinge. In the case of the -3, you have to grab it ahead of or behind the cockpit, so you end up with twisting loads. Even with a relatively stiff frame/skirt, you still are transmitting those loads to a pretty flimsy piece of piano hinge. You can make a perfect hold-open device, but it is still attached at a corner, so those twisting loads are going to be present on the hinge.

I have TWO airplanes with large (compared to the attach hinges) tip-over canopies, and I simply will never leave the airplane’s side with the canopy open - if I walk away, the canopy gets closed. It’s an operational control to an engineering problem that should have a good engineering solution, but like the many thousands of operational controls we had in place in the old heavy glider program, you have to weight the cost of the operational control versus the cost of the engineering solution......

Paul
 
Hinge canopy strut

On my -4, I installed a non pressurized strut I liberated from an airliner overhead bin door. My particular strut has no lifting capability, but has some damping effect if the canopy is blown closed. It wont prevent closure, but it does slow the slam shut scenario, similar to a screen door damper. I have toyed with making a U-channel that I can put over the strut rod when canopy is open that would prevent closure, however, I'm not a big fan of my canopy sitting open in any wind.

1+ for that. That is exactly what I have. Works very well. Mine is shorter than this picture: about 6 inches when collapsed. Attached to the cockpit rail roll-over structure mounting area by an "L" bracket. No stress on the frame when the canopy is closed. Is mostly to hold it open. AND: If the canopy is open, I am standing next to the airplane. Wind: it gets closed.
 
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