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5th Point Belt Attach Fabrication Question

L

lr172

Well Known Member
I need to get the 5th points of my harnesses installed. I have a 6A, so figured I would fab the parts, as the Van's kit may not fit well given the potential tolerance drift on the 6 series. Seems pretty easy to make. It looks like .032 or .040 stock. Can you anyone help me confirm the sheet thickness. I have .032, but no .040 stock.

Larry
 
lr172 said:
I need to get the 5th points of my harnesses installed. I have a 6A, so figured I would fab the parts, as the Van's kit may not fit well given the potential tolerance drift on the 6 series. Seems pretty easy to make. It looks like .032 or .040 stock. Can you anyone help me confirm the sheet thickness. I have .032, but no .040 stock.

Larry
Click to expand...

Going from memory I think it was 0.040. I can check this evening tough. I used the kit for the -7. I have to cut one ear off and rivet on some angle, but it wasn't a big deal.
 
Also used the -7 kit for my -6A

The passenger side fit pretty well, had to do some modification to the pilot side. Glad I did it.

R.
 
I bought the Van's kit for the 7/9, then gave up on it. The web on the ribs of my QB fuselage where not flat, they where quite bowed, and they where not square to each other, not even close. Even after shearing the flange off one side, it was still a poor fit. I have one of the first QB 6 fuselages and it shows.
I ended up fabricating my own using .063 angle for the flanges, but basically copied Van's design.
I was glad I bought the kit even though I didn't use it. It was inexpensive and a good starting point for engineering my own, but it still was a big job, much bigger than it should have been.
 
Thanks for the help here guys. I ended up copying the design that Pat Hatch used and formed the parts in both .025 and .032 and riveted them together as I didn't have any .040. Pat's design is an overlapping of two parts, making fitment easier for us 6 guys.

Larry
 
lr172 said:
Thanks for the help here guys. I ended up copying the design that Pat Hatch used and formed the parts in both .025 and .032 and riveted them together as I didn't have any .040. Pat's design is an overlapping of two parts, making fitment easier for us 6 guys.

Larry
Click to expand...

Does anyone know what thickness the Pat Hatch (Schroth) overlapping supports brackets are? Are they 0.040 or is that an estimate?

041_zpsa4333602.jpg


It looks like the easiest solution for a -6 to me.
 
az_gila said:
Does anyone know what thickness the Pat Hatch (Schroth) overlapping supports brackets are? Are they 0.040 or is that an estimate?

041_zpsa4333602.jpg


It looks like the easiest solution for a -6 to me.
Click to expand...

THey look like .040 in the picture. I couldn't find a reference to the size anywhere. I figured .040 should be adequate. I am not counting on that strap to keep me from submarining, just to keep the shoulder straps tight during turbulence.


.063 seemed like over-kill. The webs they tie into are only .032 or less.

Larry
 
Looks like a much easier install. However, it has significantly fewer rivets than Vans design and only two flanges attaching to the ribs, not four (or really three and a partial on Vans). Vans design also has flanges on top which attach it to the seat pan with four #8 screws.

The .032 ribs are in assembly with the seat pan and bottom. I don't know what forces would come into play in a minor accident, and it probably doesn't matter.
I would suspect Vans design would have significantly better torsional load strength, as well as straight line loading pulling on the belt.
Overkill? Perhaps.
I trust Vans engineering. Since I am not an engineer, I feel more comfortable with copying them.

All that said, if you are just trying to keep the belts in position.... anything is better than nothing, and I am just jealous I didn't see it done this way first. It would have saved a lot of time, but there is no way it is even close to as strong as Vans.
 
JonJay said:
but there is no way it is even close to as strong as Vans.
Click to expand...

I agree, the Van's design is much more substantial. However, the guy that designed it said that he tested it to the load spec, which is 30% of the seat belt load, and it passed.

Larry
 
lr172 said:
I agree, the Van's design is much more substantial. However, the guy that designed it said that he tested it to the load spec, which is 30% of the seat belt load, and it passed.

Larry
Click to expand...

Like I said, just jealous ;)
 
Larry - not to beat a dead horse, how does this alternate design deal with how Belt goes through the seat pan? The Vans design oversizes the seat pan slot so the strap, sandwiched between the two bulkheads, rides on the arc of the bend in the top flanges. It doesn't touch the seat pan.
You need to make sure the seat belt isn't pulling agains the edge of the seat pan. That is a pretty sharp edge and if the belt is allowed to tighten against it, not good.
 
JonJay said:
Larry - not to beat a dead horse, how does this alternate design deal with how Belt goes through the seat pan? The Vans design oversizes the seat pan slot so the strap, sandwiched between the two bulkheads, rides on the arc of the bend in the top flanges. It doesn't touch the seat pan.
You need to make sure the seat belt isn't pulling agains the edge of the seat pan. That is a pretty sharp edge and if the belt is allowed to tighten against it, not good.
Click to expand...

A local -6A flyer who added his own 5th point mount - the type that attaches to the inside of the lower skin - simply used small tubing slit lengthwise as a "custom grommet" to prevent any chafing.

The slot location and seat cushion should keep the belt angles reasonably constant.

Should be OK... :)
 
JonJay said:
Larry - not to beat a dead horse, how does this alternate design deal with how Belt goes through the seat pan? The Vans design oversizes the seat pan slot so the strap, sandwiched between the two bulkheads, rides on the arc of the bend in the top flanges. It doesn't touch the seat pan.
You need to make sure the seat belt isn't pulling agains the edge of the seat pan. That is a pretty sharp edge and if the belt is allowed to tighten against it, not good.
Click to expand...

I thought Van's design was clever in this regard. I am yet undecided how to set this up. I have the choice to mount the belt attachment as low or high as desired. My initial thought were to mount low and use a rubber edge treatment (I have some left over from the edging the glare shield). I had also thought about attaching the belt attachment fitting a bit proud of the seat pan skin, so that the webbing is just above the skin. It really depends if I have enough space in the "U" opening of my seat cushions, as I would have about 1/2" of metal sticking up.

Larry
 
lr172 said:
I thought Van's design was clever in this regard. I am yet undecided how to set this up. I have the choice to mount the belt attachment as low or high as desired. My initial thought were to mount low and use a rubber edge treatment (I have some left over from the edging the glare shield). I had also thought about attaching the belt attachment fitting a bit proud of the seat pan skin, so that the webbing is just above the skin. It really depends if I have enough space in the "U" opening of my seat cushions, as I would have about 1/2" of metal sticking up.

Larry
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Sounds like you are close to having it dialed. Most cushions I see that incorporate the crotch strap have a "slot" stitched in so the belt goes through the cushion. I chose to mount mine far enough forward so the strap will mostly clear the cushion. However, lightning holes prohibit moving it too far forward. I butted the rear bullhead up against the lightening hole flange. The forward bulkhead straddles the lightening hole. (Pretty much what they do on the 9). This moves the belt as far forward as possible. I will be able to sintch the belt down with only a bit of deformation of the cushion. It also puts the belt at an angle so the crotch strap doesn't become a jock strap. Ouch! This location is really close to how Vans shows it for the 7/9. It is also at a similar angle that the Bucker crotch strap is and that is very comfortable and works well. I may have to put a pocket in the cushion yet, but I am holding off to see how I like it the way it is first. My stick slightly rubs the cushion as it is when fully aft, so I think having the strap pull it back a bit might be ok.
You might consider modifying the design by putting the belt on the forward side of the bulkhead. You could probably even put a few spacers in and move it even farther forward without compromising too much. It wouldn't take a lot to put a flange on the top of the bulkhead also, but pretty soon, you are almost back to Vans design.
Fun stuff.
 
JonJay said:
Sounds like you are close to having it dialed. Most cushions I see that incorporate the crotch strap have a "slot" stitched in so the belt goes through the cushion. I chose to mount mine far enough forward so the strap will mostly clear the cushion. However, lightning holes prohibit moving it too far forward. I butted the rear bullhead up against the lightening hole flange. The forward bulkhead straddles the lightening hole. (Pretty much what they do on the 9). This moves the belt as far forward as possible. I will be able to sintch the belt down with only a bit of deformation of the cushion. It also puts the belt at an angle so the crotch strap doesn't become a jock strap. Ouch! This location is really close to how Vans shows it for the 7/9. It is also at a similar angle that the Bucker crotch strap is and that is very comfortable and works well. I may have to put a pocket in the cushion yet, but I am holding off to see how I like it the way it is first. My stick slightly rubs the cushion as it is when fully aft, so I think having the strap pull it back a bit might be ok.
You might consider modifying the design by putting the belt on the forward side of the bulkhead. You could probably even put a few spacers in and move it even farther forward without compromising too much. It wouldn't take a lot to put a flange on the top of the bulkhead also, but pretty soon, you are almost back to Vans design.
Fun stuff.
Click to expand...

Thanks for sharing your experiences and ideas. I'll probably protect the opening with seal so the belt can fold under the cushion. My cushion is pretty close to the stick when full aft also. I'll try to snap some pics when I rig it up this weekend.
 
JonJay said:
...
This moves the belt as far forward as possible. I will be able to sintch the belt down with only a bit of deformation of the cushion. It also puts the belt at an angle so the crotch strap doesn't become a jock strap. Ouch!
.....
Click to expand...

Some of the race car folks suggest that the 5th point be mounted rearwards, just like the jock strap effect you are avoiding...:)

safety_belt_installation.gif
 
az_gila said:
Some of the race car folks suggest that the 5th point be mounted rearwards, just like the jock strap effect you are avoiding...:)

safety_belt_installation.gif
Click to expand...

Thanks Gil. Interesting.

While the anchor point is behind, the position where it goes through the seat is actually forward, or nearly so. Those seats are hard plastic and designed with a reinforced cutout for the belt specifically for racing. I have driven a race car set up like this and, while uncomfortable, they don't crunch your peanuts.

Not sure how you could execute what is shown in the drawing in an RV. You could position the anchor point well back and fab some kind of belt guide forward like they show in the racing seat. Otherwise, with a soft compressible cushion, ouch! El nutto compressio.

Like Larry, I put the mod in less about safety and "submarining" and more for comfort keeping my lap belts in position and from riding up. Frankly, I have never heard anything about belts contributing to injury or death in any of the RV accidents reported. RV accidents seem to be of two types, survivable, or, pretty much not.... However, having a crotch strap doesn't hurt, or does it? Ha!

Always learning.
 
Like Larry, I put the mod in less about safety and "submarining" and more for comfort keeping my lap belts in position and from riding up.


Yes, that's my view too... however having the lap belt not ride up is also a safety improvement. It also somewhat depends on the size and location of your beer enhanced middle regions... :)
 
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