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Date: Wed, 23 Apr 2008 13:11:59 -0400
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Subject: Re:  Tourque tube latching system
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Gerard -

You can't simply swap the latching system for the parallelogram canopy.? You can, however, switch it over to forward-hinged.

The problem is that there is nothing to hold the front of your canopy down.? On the forward hinged canopy, the hinges do that. On your aircraft. that is what the four latches do.? As a simplification, you could think of the front latches holding down the front, and the back latches holding down the back.? The torque tube latch only holds down the back.? The front of the canopy would fly open.? The forward hinges keep the front of the canopy down.

It is possible to retrofit the canopy.? There are three main projects -- the front hinges, the gas struts, and the torque tube latch.? Here's essentially what you do, and where any pitfalls may await.? All the parts you need are in the kit available from Lancair.

1)? Put hinge brackets?on the back side of the header tank. ?Make a "pocket" in the header tank to hold the hinges.? Don't have a header tank?? Then you need to put something there to hold the hinges.? If you do have a header tank, be aware that there were two styles.? The early style had a flat aft surface and would have to be modified.? The newer style (and my 1994 kit has this, so it's not *that* new) has pockets built in.? If you have have a new-style header tank, it's pretty easy.? Sand off the gelcoat locally and flox on the hinges with a multi-BID cover.? A very easy job.

2)??Cut the canopy side rails?thinner.? Yours are about 1.5 inches thick between latches to provide stiffness.? They need to be thinner for the gas strut to fit.? Put some BID over what you cut off.? Mount a ball-fitting on each side of the canopy.? The gas strut anchors to that.

3)? The canopy was stiff until you cut the side rails.? Add 80 feet of carbon uni to the front of the canopy (on the inside) to make it stiff again.? It's really not that hard to do.

4)? Make BID angles on the front of the canopy to hold the hinge brackets.

5)? Cut two slots in the glare shield for the hinge brackets to move through.? (Oh, and there better not be anything in the way of those -- you may need to reconfigure stuff behind your panel.)

6)? Put aluminum brackets on the fuselage sidewall?on the front side of the instrument panel to hold the other ball-fitting (the front end of the gas struts).? You'll need to bond in a phenolic piece for the bracket to bolt onto.? My instructions called for drilling a three screw-holes thru the fuselage, so some paint repair migiht be needed.? I'll bet you could work with the Lancair guys to determine an adequate BID layup to hold in the phenolic strongly enough?so that you didn't actually have to drill through the painted fuselage -- studs embeded in the phenolic would do the job.

7)? Modify the glare shield so that there's adequate clearance for the gas strut between the glare shield and the canopy.? It's pretty tight.

8)? Bond end fittings for the torque tube onto the fuselage interior sidwall behind the seat.

9)? Cut a hole in the side of the airplane for the latch handle.? Build up a smooth glob of micro on the outside to blend the handle into the airplane outer surface.? Fix the paint.

10)? Cut slots in the aft face of the canopy for the latch hooks to engage.? There's some hardware that goes here but that's part of the kit.

Oh, and when you're done, the front edge of the canopy will probably sit a little higher.? Some body work may be required.

In principle, it's not that complicated.? In practice, it may be a significant project on a finished airplane.? It's definitely easier to do when you're building, but?I think a good aircraft build support shop could do the job for you for a fixed price.

Me, I'd leave it as is...

- Rob Wolf

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<div>Gerard -<br>
<br>
You can't simply swap the latching system for the parallelogram canopy.&nbsp; You can, however, switch it over to forward-hinged.<br>
<br>
The problem is that there is nothing to hold the front of your canopy down.&nbsp; On the forward hinged canopy, the hinges do that. On your aircraft. that is what the four latches do.&nbsp; As a simplification, you could think of the front latches holding down the front, and the back latches holding down the back.&nbsp; The torque tube latch only holds down the back.&nbsp; The front of the canopy would fly open.&nbsp; The forward hinges keep the front of the canopy down.<br>
<br>
It is possible to retrofit the canopy.&nbsp; There are three main projects -- the front hinges, the gas struts, and the torque tube latch.&nbsp; Here's essentially what you do, and where any pitfalls may await.&nbsp; All the parts you need are in the kit available from Lancair.<br>
<br>
1)&nbsp; Put hinge brackets&nbsp;on the back side of the header tank. &nbsp;Make a "pocket" in the header tank to hold the hinges.&nbsp; Don't have a header tank?&nbsp; Then you need to put something there to hold the hinges.&nbsp; If you do have a header tank, be aware that there were two styles.&nbsp; The early style had a flat aft surface and would have to be modified.&nbsp; The newer style (and my 1994 kit has this, so it's not *that* new) has pockets built in.&nbsp; If you have have a new-style header tank, it's pretty easy.&nbsp; Sand off the gelcoat locally and flox on the hinges with a multi-BID cover.&nbsp; A very easy job.<br>
<br>
2)&nbsp;&nbsp;Cut the canopy side rails&nbsp;thinner.&nbsp; Yours are about 1.5 inches thick between latches to provide stiffness.&nbsp; They need to be thinner for the gas strut to fit.&nbsp; Put some BID over what you cut off.&nbsp; Mount a ball-fitting on each side of the canopy.&nbsp; The gas strut anchors to that.<br>
<br>
3)&nbsp; The canopy was stiff until you cut the side rails.&nbsp; Add 80 feet of carbon uni to the front of the canopy (on the inside) to make it stiff again.&nbsp; It's really not that hard to do.<br>
<br>
4)&nbsp; Make BID angles on the front of the canopy to hold the hinge brackets.<br>
<br>
5)&nbsp; Cut two slots in the glare shield for the hinge brackets to move through.&nbsp; (Oh, and there better not be anything in the way of those -- you may need to reconfigure stuff behind your panel.)<br>
<br>
6)&nbsp; Put aluminum brackets on the fuselage sidewall&nbsp;on the front side of the instrument panel to hold the other ball-fitting (the front end of the gas struts).&nbsp; You'll need to bond in a phenolic piece for the bracket to bolt onto.&nbsp; My instructions called for drilling a three screw-holes thru the fuselage, so some paint repair migiht be needed.&nbsp; I'll bet you could work with the Lancair guys to determine an adequate BID layup to hold in the phenolic strongly enough&nbsp;so that you didn't actually have to drill through the painted fuselage -- studs embeded in the phenolic would do the job.<br>
<br>
7)&nbsp; Modify the glare shield so that there's adequate clearance for the gas strut between the glare shield and the canopy.&nbsp; It's pretty tight.<br>
<br>
8)&nbsp; Bond end fittings for the torque tube onto the fuselage interior sidwall behind the seat.<br>
<br>
9)&nbsp; Cut a hole in the side of the airplane for the latch handle.&nbsp; Build up a smooth glob of micro on the outside to blend the handle into the airplane outer surface.&nbsp; Fix the paint.<br>
<br>
10)&nbsp; Cut slots in the aft face of the canopy for the latch hooks to engage.&nbsp; There's some hardware that goes here but that's part of the kit.<br>
<br>
Oh, and when you're done, the front edge of the canopy will probably sit a little higher.&nbsp; Some body work may be required.<br>
<br>
In principle, it's not that complicated.&nbsp; In practice, it may be a significant project on a finished airplane.&nbsp; It's definitely easier to do when you're building, but&nbsp;I think a good aircraft build support shop could do the job for you for a fixed price.<br>
<br>
Me, I'd leave it as is...<br>
<br>
- Rob Wolf</div>
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