Ch 8 Roll Over/Seat Belts

Once I started working out the location of the common fuel sump it became clear that the rear seat belt attachments were in the way.

I used a high wattage soldering iron to heat up the screws in the old attachments to get them out as they were embedded in flox. It took a while but they came out very cleanly. I filled the holes with micro after spending several hours removing the 7 ply layups and wooden hard points. Why carry the extra weight? Its only my time…

I located the new seatbelt spot about 7 inches aft. It still works as a good position for belts. As before I made up the plywood inserts and floxed them into position. After cure and a clean up came 7 plys of BID per plans and more peel ply. Finally I located the 2024 aluminium angle after cleaning them up and re alodining them to drill two holes for each side.

Then I went to the outside of the fuselage and ground away material with my dremel so the screws could seat without protruding. Finally I just let them sit there loose! The work is done except floxing in and I might hold off until the common sump is done. This way I can keep the angle away from all the layups that are associated with the sump.

Rear seat holes plugged

New hardpoints

Location change done

This step is securing the lower seat belt attachment points and was done over a few days.

I first 5mt epoxyed each attachment in place and used them as a drilling jig to make the 1/4″ holes.
Next using the dremel to make a flat inlaid hole for the AN525-416R16 bolts as shown in pic 1
I then tested each hole by securing the fitting to ensure I had 2 to 3 threads showing through the nut.

This was worth doing and I deepened each hole slightly ending up with three threads showing when the job was done. Its just the sort of thing that might be picked up on an inspection if there was any doubt as to the nut being in safety. As it happens I needed AN525-416R18 (1/8″ longer) which I felt was a better option than just digging out more timber.

The second pic shows the hardware. I carefully sanded the surfaces, coated them with pure epoxy and then floxed the parts into place. I torqued the bolts to 40 inch pounds. AN4 is usually 50 to70″lbs however I am only using soft spruce then plywood and then glass and this was quite tight enough. Any more would have deformed the spruce. The bolts are in shear and it is very secure.

That’s it for chapter 8. The metal rollover will happen later.

Countersunk holes

Hardware

Floxed and bolted in place

This step was done while I was waiting for other things to cure over a few days. Its 2024 T3 angle cut into 2″ strips and shaped to make the lower attachment points for the front and rear harnesses.

I’ve just bought a second hand bandsaw and already have a linisher. The holes took a while and I made them at 6.3mm which is under 0.25″ or AN4 size however this was just too tight and I opened them out to 0.25″. Not worth forcing a press fit and risking damage. All the forces seem to be in compression rather than much shear and a tiny wiggle is acceptable given then will be floxed in anyway.

I took some care to get all the scratches out so there are no stress risers. I sanded down to 600 grit and then used scotbrite to finished off. Another pretty part no one sees once the plane is built.

2024-T3 angle cut in 2″ lengths

Holes drilled carefully

Cleaned up and shaped

This step is adding the seat back and then glassing it. I first floxed in the two pieces prepared earlier and let it cure.

Then the structure was microed and again left to cure. This is hardshelling and I tried it in an attempt to improve my glassing technique when using BID.

Once the micro was sanded smooth I wet it out with pure epoxy and then did two plies on foil which I transferred across and further trimmed while wet. I spent some time wetting it out, checking for air and then adding peel ply.

Despite my best effort there was some small flecks of air again in the layup. Well within Rutan’s limits as laid out in the plans however, I need to get this technique right. It is extremely difficult to see air in the wet glass on this colour divinycell foam.

It still looks like a good job and after a clean up my seatback area will be done. I probably won’t use the hard points I so carefully made as I now intend to put the upper seat belts on the metal rollover that is still to be designed.

Flox in the glass foam pieces

Foil layup

Completed seat back

The ‘inside of the rollover is glassed with just one ply of BID. You can see this in the first pic. I have peel plied it and some timber residue is in the pic that comes off with the peel ply. I was keen on getting this straight so put some weights on the layup as it cured.

The second pic shows the bare inside roughly timmed. There is a 12 ply reinforcement pad that is to be laid up over the wooden insert from the other side. I first made up the 12 plys separately as in pic 2. This seems a lot neater than the plans method.

I then cut out slightly oversized pieces of this glass and carefully routed down to the timber inset as in pic 3. It was then easy to flox these in place.

Outside of rollover

Glassed inside of rollover

Hardpoint inlays

The front seat has a structure on it that holds the upper seat belt attachments for the pilot. I have decided to build this almost per plans but leave out the triangular so called rollover. I’ll add a metal rollover later which will give more protection in the event of an accident where the cockpit becomes inverted.

The plans ‘rollover’ was never designed for crash protection and I’ve seen pictures of a VE accident where a metal rollover protected the pilot. Enough said.

For now its just bracing in the top of the seat and this may also give some extra strength to the cockpit so worth including.. The first pic shows some foam cut to size and the second pic is a trial fit.

The third pic shows the wooden inserts that go on the inside of the seat belt attachment area. I routed out the squares and floxed the timber in with weights on the outside until cured.

Seat back foam structure

Test fit

Wooden Harness inserts

Each hard point has 7 plies of BID each. The edges are peel plied as well as the top area where the extrusion will later be floxed in place.

I cut out each of the 28 pieces on foil doing the rear and then front in two separate layups. While this took all afternoon I ended up with a neat result and used up some of my BID off-cuts.

Foil layups

Front seat hard point

Rear seat hard point

These are the lower hardpoints for the seat belts front and back. I’m not doing the ‘step’ as I’ll use an electric nose lift so all four hardpoints are the same. I used the left over plywood from the firewall.

A bit of time was spent getting them to fit nicely and I decided to flox them in and then do the layups later. I sanded the attachment area glass dull as I neglected to peel ply this area when doing the assembly tapes. Not a problem.

Using plenty of flox for the bond, I then lightly nailed the plywood in position after drilling out holes. The nails are in the same position as I’ll have to drill through later when the extrusion belt attachments are screwed in place. Easier to go this way than do it all at once and have the plywood moving around. Just a clean up with a paper towel and then left to cure.

Plywood inserts

Fitted to longerons

Floxed and nailed

These are the lower hardpoints for the seat belts front and back. I’m not doing the ‘step’ as I’ll use an electric nose lift so all four hardpoints are the same. I used the left over plywood from the firewall.

A bit of time was spent getting them to fit nicely and I decided to flox them in and then do the layups later. I sanded the attachment area glass dull as I neglected to peel ply this area when doing the assembly tapes. Not a problem.

Using plenty of flox for the bond, I then lightly nailed the plywood in position after drilling out holes. The nails are in the same position as I’ll have to drill through later when the extrusion belt attachments are screwed in place. Easier to go this way than do it all at once and have the plywood moving around. Just a clean up with a paper towel and then left to cure.

Ply wood inserts

Fitted to longerons

Floxed and nailed