Attach point for secondary lap belts?

Howdy all,

Since I'm planning on doing sustained inverted and other acro in the -7A, I want a secondary lap belt for both pilot and pax. The queston is: How to attach it to the airframe? The primary belt uses those nice steel angled brackets and I'd like to do something similar for the secondary belt, but after a bunch of head scratching I still don't have a good spot to use as a mounting point.

Anyone have any good ideas for how to do this? Pictures would be wonderful.

Thanks!

Huh...?

I've never heard of anything like this, and judging from the lack of response I guess no one else has contemplated it either. Seems like a lot of confusing clutter to me.

Oh really?..

Actually I do have a backup lap belt...For me only I think its overkill to have one for the PX.

I think the underwhelming response is more due to the fact the very few RV's are flown negaitive G.

The fact remains if you examine the latch mechanism of the Vans belt there is precious little holding you in the airplane when hanging in the harness...It won't take much for you to fall out and lose control of the airplane.

I simply threaded my backup belt through the exisiting buckles that are bolted to the existing lapbelt.

Yes its a single point of "failure" but the bolts downs really are not going anywhere.

Personally if I were doing it agian I would use a different 5 point harness...But the backup lapbelt works OK too.

Frank

Open cockpits...

.....were one of the big reasons for a backup belt, not so much the closed cockpits. P-51's and others didn't have two belts for the pilot.

Regards,

Mike,
Got any photos of the structure in the belt attach area?

Photos

Hi, Dan.

Here are some photos of the structure. This is the pilot's side of the rear spar bulkhead. You can see the white seat belt attach brackets on either side.


A closeup of the left bracket.


A closeup of the right bracket.


As you can see, it's pretty crowded in there.

I hadn't considered it before, but I like Frank's suggestion. It could be argued that the chance of failure is directly related to the complexity of the component. If that thought process is a good one, assuming the seat belt latch is 10x as complex as the belt itself or the attachment points, then just by having the secondary belt and latch I've addressed 90% of what I'm trying to accomplish with a completely redundant system (including attach points).

Hrm...gonna have to let that one roll around in the noggin' a bit.

If you have any thoughts Dan, I'd love to hear them. I've got a lot of respect for your analytical mind.

If you really intend to hang from the belts, the second lap belt is best mounted forward of the original, and should incorporate a ratchet to tighten the belt after latching.....standard acro stuff.

Might want to consider an aluminum doubler on the floor rib (black lines) and a steel attach tab for the belt (red lines)...actually two tabs, sandwiched, so the belt bolt is in double shear.





Hookers, sans ratchet....you really did want double belts to acro this one <g>

The solution...

Thanks Dan for the great idea. After seeing your sketch, I thought about it some more and this is what I came up with.

I'm posting a pic in case anyone else feels the need to implement something similar.



They're not complete yet, but this should give a good enough idea about what the finished product look like.

You can see that I've added an additional rib close to the new bracket. The crosswise pieces are doubled up .032 aluminum that will be riveted to the ribs on either side, the bottom skin, and the seat floor panel. The steel brackets themselves were laser cut and bent on a press brake. I'll get them powder coated white to match the others before installation...or maybe I'll just paint 'em with a rattle can.