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  #1  
Old 03-20-2018, 09:04 PM
Jake14 Jake14 is offline
 
Join Date: May 2014
Location: Seattle
Posts: 390
Default Head hitting canopy fix

The sometime sharp-edged turbulence around the local foothills has caused my head to hit the (RV-14A) canopy fairly hard several times, even with the 5-point harness snugged up tight. The problem seems to be the location of the lap belt anchors well behind the seat. While doing a good job of restraining in the forward direction, vertical motion can easily be 4-5 inches. The solution seemed to be an extra lap belt anchored further forward.

I got some seat belt anchors from Van's and located them about 9 inches forward of the stock ones (see first pic). The mounting would have been simple during the build, but out on the tie-down, not so much. The floor beam material is quite thin, so added an .060 angle and stiffener on the side opposite the anchors using plenty of pro-seal and two AN-3 bolts (see pics 2 & 3). Pic 4 shows the installation with the ratcheting lap belt (wrong color, but hey...). This has been very effective, you can ratchet the belt down till your bones bend and you definitely become one with the airplane. My head hasn't hit the canopy since and I also really like the feeling of being glued in place even with the simple acro I do.

This is an additional, optional restraint. The primary restraint is still the standard CROW 5-point harness.
I considered using the new anchors for the stock lap belt, but I think you'd need an ok from Van's engineering








-------------------------------------------------------------------------------------------
Some recent additional info:


when I originally posted this, I commented that "This is an additional, optional restraint. The primary restraint is still the standard CROW 5-point harness"

I also asked Van's for comments on the installation. Here's what they said:

---------------------------------------------------------------------
Thanks for your concern. We test our seatbelt installations to the requirements of FAR 23. This is an involved process. Without testing and calculations it would be impossible to determine if your solution would or would not work. Note that my gut feeling is that due to load path and angles your design may fail in a crash situation.

With that said our recommended solution is a crotch strap. The crotch strap 5th point not only prevents your head from contact with the canopy but will also prevent a body from slipping out and forward underneath the belt.

Regards,
Rian Johnson
VP / Chief Engineer
Van's Aircraft Inc.
--------------------------------------------------------------------------

So this just emphasizes my original comment about the standard 5-point harness being the primary restraint, which should always be worn. I found Van's claim that the crotch strap will keep your head from hitting the canopy not to be the case for me. The aft location of the lap belt anchor points still allows one's hips to lift up a few inches. There's just no substitute for a ratcheting belt pulling the hips mostly downward

Just wanted to pass this along in case someone tries to use the forward anchors for the primary restraint. I don't know what kind of testing FAR 23 requires, but it may be out of scope for a homebuilder so I think an auxiliary install like this, which keeps the stock primary restraints is a good option

Ps I did consider another bracket riveted to the bottom skin for additional strengthening, but it seemed like overkill.. however, during the build stage, it would be quite easy to duplicate Van's anchor supports further forward, (with some adjusted angles)
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Last edited by Jake14 : 03-28-2018 at 11:06 PM.
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  #2  
Old 03-21-2018, 07:26 AM
RV8Squaz's Avatar
RV8Squaz RV8Squaz is offline
 
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Location: Senoia, Georgia
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Hi Jake. Where did you get the ratcheting lap belt from?
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  #3  
Old 03-21-2018, 09:29 AM
Jake14 Jake14 is offline
 
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got it used on VAF. It's a Hooker, but I didn't need the whole set since the Crow works fine for the forward restraints
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  #4  
Old 03-21-2018, 09:56 AM
mturnerb mturnerb is offline
 
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Jake: Do you have crotch strap, and if not do you think it would address the issue as effectively as the second belt?
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  #5  
Old 03-21-2018, 12:44 PM
Jake14 Jake14 is offline
 
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Location: Seattle
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The crotch strap helps, but it seems to be too far forward to keep you from lifting up, but if you relocated the standard lap belt to the forward anchors and then also used the crotch strap, I think it would be a big improvement
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Last edited by Jake14 : 03-21-2018 at 07:33 PM.
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  #6  
Old 03-21-2018, 08:28 PM
HSANTIBANEZ HSANTIBANEZ is offline
 
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Location: Chile, Valparaiso
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Quote:
Originally Posted by RV8Squaz View Post
Hi Jake. Where did you get the ratcheting lap belt from?
Hi, I get from Silver Parachute they have the hole 5 point harness for RV with ratchet
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  #7  
Old 03-22-2018, 07:34 AM
MED MED is offline
 
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Location: Aiken, SC
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Just curious, Jake, how tall are you?
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  #8  
Old 03-22-2018, 10:08 AM
Jake14 Jake14 is offline
 
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I?m 5? 10.5?. The headset is about 4? from the canopy
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  #9  
Old 03-22-2018, 10:27 AM
MED MED is offline
 
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Oops. I?m 6?1? (or I was). Fortunately, no mountains around here . . .
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