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N44VY · 5 November 2009, 12:51 AM

Vet and Gang:

Couple of questions about the elevators and horizontal stabilizer:

1. Replicas I've seen have the hinges on the top, mostly, but one has them on the bottom of the mating spars. Good practice says place the hinges on top of the spars, but I wonder if there is an overwhelming reason not to? Also, I have seen three sets of hinges used per elevator and I've seen 4 hinge sets on one plane. The Schultz drawings are not clear. Looking at the elevator design and rib placement, I suspect three hinge sets were originally used. Place the center hinge in line with the center rib that carries the elevator control arm to strengthen the stab and elevator spars at that flex-load point. Then place the other two hinge sets mid-way between the two outer ribs for a symmetrical match. With the 4 hinge set up, there is no hinge at the elevator control arm. Anyone have it on good authority how many were used and where?

2. The Schultz drawings show both the elevator and stab spars as flat cut boards with slightly rounded edges. This causes clearance issues between the elevator spar and the stab spar with the hinges placed on top or bottom. Let's go with the best choice and put the hinges on top for this example. If I want the elevator to move up and down without hitting the stab spar, I have to move the elevator aft to open up a rather large gap, otherwise the spar binds on the stab spar at the lower-mid point of down elevator throw. I am not happy with the large gap mainly because it reduces the hinge bearing surface on the spars, and secondarily because it is a high drag problem. It seems to me that an elegant solution would be to slightly bevel the elevator spars to allow more down elevator movement and thus enable me to close the gap. Was that what Curtiss did, or am I missing something with the Schultz drawings?

As always, I thank you for any input you wish to add. Bob C.

5 November 2009, 12:51 AM	#27 (permalink)
N44VY Observer Join Date: Mar 2009 Location: Shenandoah Valley Posts: 58	Elevator Hinges Vet and Gang: Couple of questions about the elevators and horizontal stabilizer: 1. Replicas I've seen have the hinges on the top, mostly, but one has them on the bottom of the mating spars. Good practice says place the hinges on top of the spars, but I wonder if there is an overwhelming reason not to? Also, I have seen three sets of hinges used per elevator and I've seen 4 hinge sets on one plane. The Schultz drawings are not clear. Looking at the elevator design and rib placement, I suspect three hinge sets were originally used. Place the center hinge in line with the center rib that carries the elevator control arm to strengthen the stab and elevator spars at that flex-load point. Then place the other two hinge sets mid-way between the two outer ribs for a symmetrical match. With the 4 hinge set up, there is no hinge at the elevator control arm. Anyone have it on good authority how many were used and where? 2. The Schultz drawings show both the elevator and stab spars as flat cut boards with slightly rounded edges. This causes clearance issues between the elevator spar and the stab spar with the hinges placed on top or bottom. Let's go with the best choice and put the hinges on top for this example. If I want the elevator to move up and down without hitting the stab spar, I have to move the elevator aft to open up a rather large gap, otherwise the spar binds on the stab spar at the lower-mid point of down elevator throw. I am not happy with the large gap mainly because it reduces the hinge bearing surface on the spars, and secondarily because it is a high drag problem. It seems to me that an elegant solution would be to slightly bevel the elevator spars to allow more down elevator movement and thus enable me to close the gap. Was that what Curtiss did, or am I missing something with the Schultz drawings? As always, I thank you for any input you wish to add. Bob C.