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Shoulder Belts on a Baby Ace

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Little Scrapper

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I’m at a point where I need to figure out the seat belt attachments for the Baby Ace. I want shoulder belts.

Anyone familiar with doing this on a open cockpit airplane like the Ace? I’ve seen people run a cable to the rearward fuselage (anchor point) so that’s something I’m trying wrap my head around but I’m also trying to figure out that nasty downward angle after my shoulder because I know I need it high.

Anyone want to have that conversation? Lol. Lots of options I guess. I just know I need to buy a belt and get to work.

Mike
 

TFF

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How high do you think you are going to sit? If your shoulders are proud the rear deck, that does make it hard to get a best angle. Is there going to be a headrest?
 

don january

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Mike. I arranged my shoulder belts coming out of the seat back bulkhead at bottom of cross member and with my seat it places the exit of belts about 2" below the top of my shoulders and in my thoughts this will hold me in position if inverted or in a nose over. I think that the pressure point should be on top of the shoulders and not the front area only. In other words the belts should hold you down and not just back against the seat.
 

Riggerrob

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Dear don January,
Shoulder harness design is a bit more complicated than that. If shoulder strap attachments are below the tops of your shoulders, they tend to compress your spine during forward impacts.

To prevent falling “upwards,” Aerobatic pilots depend upon two sets of lapbelts, the second belt double-wide with a ratchet.

Returning to the Corbin Ace, I recommend routing the shoulder straps over a steel tube cross bar that is welded into the turtleneck. The higher the better. Ideally above the tops of the pilot’s shoulders. Route a steel anchor cable back to a hard-point near the tail wheel.

If you still want to depend upon shoulder straps preventing you from “falling” out the top, add a second set of shoulder straps and anchor them near the lower, rear corners of th the seat. If you enclose both sets of shoulder belts in the same “sleeve,” you will vastly simplify the strap-in procedure.

For more formal reading: see the FAA manual on seat-belts (FAA TSO C22) written by Simula, a couple of years ago.
 

don january

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Dear riggerrob, Thanks for your clarification on belts. I shared with Mike what I had to do for such a small plane. Other then some turtle deck former's the only thing above my shoulders is air. FAA TSO C22 along with AC 43.12 chapter 9 are a great place to start and to get an idea but each plane has its own requirements and lets not forget mine is a all wood experimental aircraft from 1954 so options are limited
 

Little Scrapper

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I think a few people put a cross tube in the cabane like my awful drawing shows?

Would this be a good idea? The height needs to at a ideal position which I’ll read about.
65834177-E6D2-441A-AC9F-2B628376D335.jpeg
 

Vigilant1

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When looking at the frame, the cabane looked to be at the right height and location. But, I couldn't tell if they are triangulated/ braced to take fore/aft loading. If not, the straps/cables could be anchored at the rear hardpoint you identified earlier, then route them over guides on the cabane crossbar. That gets them above your collarbone, but the cabane isn't loaded in the forward direction.
 
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Mad MAC

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What type of harness, single or dual shoulder attachment points. The later would reduce the bending loads on the cross member. The design load is on the order of 1600 lb (20g & 200 lb pilot). The Titan T51 fatal in NZ a couple of years ago was due to failure of the cross tube welds. Cross tube needs to be stiff and have a good weld connection (gussets maybe).

Edit: I forgot the fitting factor of 1.33 which applies to "each seat, berth, safety belt, and harness, its attachment to the structure"
 
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Little Scrapper

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Still working on this. I reached out to a builder and this is how he approached it.

D1AFFF83-EA5D-453E-B881-B5397E712576.jpeg9178C1AD-C282-400D-82F7-BC83410AEE92.jpeg59969EF9-B364-49EE-B839-05DD82127C51.jpeg76C1262E-06C0-4B0F-970C-9A3679288F43.jpeg
 
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