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Ideas for Better Seat Harness?


FlyingMonkey
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I'm finally getting too annoyed with the factory belts to want to keep using them (it only took 8 years!). 

I know some of you have gotten custom harnesses made, and I'm looking for a good, more-or-less drop-in four point replacement solution that won't break the bank.  An anti-submarine belt is not a requirement, but I'm not opposed to one either if it's easy to install and not a PITA to put on and off every time you use it.  I prefer a "hook and latch" style closure to the "circle camlock" style.

Let me see those harnesses! 

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Thanks guys.  I have a local drag racer who recommended Racequip racing harnesses.  I looked at them in person and they are well made and pretty inexpensive ($100 each).  I ordered one to try, I will let you know how it works out.

For $100 I don't mind taking a chance, and if they don't work out I can always go with something else and not be out a lot of scratch.

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10 hours ago, Jim Meade said:

No crotch strap 

The stock harness doesn't have a crotch belt either.  I'm not saying there is no benefit, but it's a tradeoff.  It restricts movement and makes it impossible to pee on a long flight without unbuckling the belts.  I also think the nature of the angles involved in a CT makes sliding under the lap belt less likely.

The harness I bought has a crotch belt.  I'll install it and try it, but I don't think I'd use it all the time.

Here's what I got:

https://www.summitracing.com/parts/VMS-809009

Make sure you order a harness with 2" straps (standard automotive seatbelt size).  I tried a test with a 3" strap and it doesn't fit the attach points in the airplane without bending/folding the harness.

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The crotch strap is called an anti-submarining strap. It's designed to keep the belt from riding up in the event of a head on collision, which severely damages internal organs.

There's not really a good place for them in our aircraft, because the seats have to be designed for them, otherwise they wont be effective much at all, and in a lot of cases, make it worse.

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3 hours ago, Anticept said:

The crotch strap is called an anti-submarining strap. It's designed to keep the belt from riding up in the event of a head on collision, which severely damages internal organs.

There's not really a good place for them in our aircraft, because the seats have to be designed for them, otherwise they wont be effective much at all, and in a lot of cases, make it worse.

What are the seat design criteria required for the anti-sub belts to be effective?

Can you suggest some references for the assertion that in our aircraft they won't be effective and in a lot of cases make it worse?  That raises serious concerns and of course we're all interested in learning more of the evidence behind this statement.

In particular, how would the crotch strap reduce or impede the ability of the four point part of the harness to work?

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Anti-submarine strap installation:

Reference 1: http://crowsafetygear.com/Pages/Install.html

Reference 2:

 

Note that straps should be designed as to pull the safety harness down where your upper pelvis will ride against it.

If you strap it in a way that it anchors in front of you, it will not hold it down; it will hold it out and away. Your shoulders will press against the harness, pulling it up, and your unrestrained waist would slide forward in the seat. You're gonna have a bad time with injury to your manhood/womanhood.

Without any strap at all, the shoulder harnesses will pull the belt up into your abdominal area. It's a far shot from being as bad as 3 point harness submarining, as the shoulder harnesses will not allow it to ride too deeply, but it's still not ideal.

Dangers of submarining:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4776614/

http://www.speedhunters.com/2017/12/think-you-know-everything-about-racing-harnesses/

The factory shipped harnesses we have are not terrible; it's unlikely to end up in a situation where we will have a direct forward impact, most likely it will be down and forward.

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I view this as more of a model specific topic.  SW = upright seats, LS = reclined (and most every LS I've seen has the seats laid back)

Being a SW driver the ability to recline seat is limited, and beyond that I use a more straight up angle which the first link shows as preferred.  

Those in an LS who recline the seat way back would be more susceptible to submarine issue.  And I suppose it's the taller & heavier guys that have the seat all the way back reclined.  That has one balancing space from the head hitting the spar box v/s reclined in the less ideal belt situation.  I'd keep the head clearance, and ensure the belts are adjusted to be as low as one can keep them on the lap belt.

 

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On submarining.  The Toyota pickup example featured a cantilevered seat plan.  Our FD do not have that seat plan.  I don't think the citation relates directly to our situation.

The Schroth advertorial recommends 5 or 6 point harnesses but doesn't differentiate between them.

My understanding is that the function of the anti-submarine belt is not to compress your gonads as you slide into it but rather to keep the lap belt low so it is in the correct position over your pelvis.  I don't have a citation for that.  If the lap belt is kept in the right position, submarining is unlikely.

According to the cited documents, a tilted back seat absorbs a considerable amount of the force and should add to seat belt restraint.

Of course much depends on proper installation, adjustment and use of seat belts.  Don't wear them loose.

Thanks for providing the references.

Let the discussion continue.

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1 hour ago, GrassStripFlyBoy said:

Those in an LS who recline the seat way back would be more susceptible to submarine issue.  And I suppose it's the taller & heavier guys that have the seat all the way back reclined.  That has one balancing space from the head hitting the spar box v/s reclined in the less ideal belt situation.  I'd keep the head clearance, and ensure the belts are adjusted to be as low as one can keep them on the lap belt.

I think it may be more that they don't know how to use the seat support strap properly. I have had airplanes come in the shop with damaged seats ans loose support strap, and owners who were never taught that the strap needs to be tight and supporting the seat.

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My references were just to show what submarining is, and shows the proper installation of a belt with an antisub strap.

Just as you said, you need to fit the belt properly.

Adding another strap along the bottom that does not fit properly is not going to be any better than having no anti-submarine strap at all. Adding a strap in our aircraft will pull the waist belt away from you. The seat needs to be designed for the antisub strap to tuck the waist belt against you. Don't use an antisub strap if it's not designed for this, or some other accommodating method.

4 point harnesses aren't widowmakers like this all might sound, but modifying the belt design might make it one.

EDIT: there are 4 point harnesses which don't need antisub straps. The issue in our CTs is that the anchor points are far behind, rather than angled downwards, which is why you can't make the shoulders very tight without it riding up.

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6 hours ago, Tom Baker said:

The earlier airplanes used a webbing material that was soft and slick, and they do not stay tight when adjusted.

That is my issue.  Mine literally require adjustment every 3-10 minutes.  I have tried friction tape and other fixes with various yet unsatisfactory effects, and it's time to give up on my factory harnesses. 

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