Access Hatches – it’s not easy to do it well

IMG_0121.JPGHere’s the transmission tunnel buck, and I have the moulds from it, after some finishing. It’s a split mould, one top, and two sides. Now I have to start thinking really hard about just how many access panels I put in, and how to make them.

I’m replicating the recess and access panels so wherever I need to fit them on the tunnel, they will all fit to each other and be interchangeable.



IMG_0120.JPGHere is the closer up view of the access hatch, or at least the recess for it. I want the finished panel to both fit flush, and be bolted through. This recess on the right will be cut out, apart from leaving a 12mm rebate all the way around to allow the panel to fit an bolt through (into the rebate).

I will reinforce back of the rebate, and use 5mm nutsert flush fitting thread things to receive the socket-headed cap screws. The recess is 5mm deep, as is the head of a 5mm cap-screw. I’ll bond the nutserts in from the back, and use my friendly neighbourhood cad package to get the spacings right.

Today, I’ve made a mould from the positive mould part made from the recess (gel-coat and three layers of 450, poly resin). This means I’ve now replicated the recess above, and I’m using that to make a trial CF part.

The plan to make the flush fitting panel is:

  • 3 layers of 350gsm CF to capture the back of the panel, and this should be a perfect fit into the recess
  • drill the panel for the mounting holes.
  • Bond some 1mm washers to the inside of the base panel to spread the load of the cap screw. I wish I had better washers that were a larger washer size with still a 5mm hole. Araldyte will be fine for this.
  • cut some flat CF sheet I have spare to the profile of the top of the part. It should sit totally flush with recess above.
  • mix some epoxy with glass micro bubbles to act as an adhesive and core material all in one go. The micro bubbles reduce density by adding air, in essence. When they’re in the box before they’re mixed, they’re like an ultra-lightweight fine powder. Definitely not something of which one wants a lung-full.
  • put the panel-back in the mould, and fill it with the epoxy/glass bubble solution and put the top on. Let it set.
  • Crack it back out of the mould again, and drill through from the back right through the front.
  • Drill through from the front with a drill the same diameter as the cap screw with a mm or two to spare. This needs to be done carefully to countersink the cap screw head. I think I’ll be setting the depth gauge on the pillar drill.

There we have it – one flush panel, with recessed bolt heads and some structural strength. I’ve spent quite a while today thinking about how this would work and I think it’s a good plan. A bit of a faff mind.


2 thoughts on “Access Hatches – it’s not easy to do it well

  1. It will be interesting to see how the hatches turn out. However I don’t think i understand how you are bonding the washers in, will they be visible. I’m working on hatches at the moment but in alloy.

  2. If you imagine the hatch is a bit like the shape of a house-bath, but with a lid on (i.e. it’s a three dimensional hatch shape). The washers will be bonded to the upper-facing part of the base (the bit you sit on in the bath). then the whole bath gets filled with … filler, and the lid gets glued on.

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