6.08.2021 Shutters open mock-up.

 *

Friday 6th 58-74F, bright and breezy but increasingly cloudy. Thunder storms forecast for this evening and overnight.

It seemed sensible to have a proper mock-up with the shutters wide open. Just in case I had overlooked something important. First I trimmed and fitted the triple layer, zenith board. Then I screwed it between the slit ribs with two, perforated, roofing plates. 

Externally, I used a long length of slotted angle iron for top end, [temporary] shutter support. This had no real thickness but was very stiff. So matched reality better than I could have hoped. 

I started off using the ladders as outboard props. They soon proved to be getting in the way of the shutters. So I used blocks of 2x4 for support from the dome and pulled the ladders clear. The shutters were balancing themselves equally. So the forces were minimal. It was interesting how the support at the bottom affected the straightness of the shutter ribs. There will have to be narrow cross ribs to keep everything straight.

The images show the arrangements. Note that the temporary, 2x4, slit rib, cross braces will be removed once the dome is finished. I will have to complete the fibre-glass work first. Nor can I fit the drawer slides yet. I want to glass over the outside of the zenith board and down onto the dome for a weather seal and maximum load spreading.

With the ribs and dome now properly supported I should have started glassing over the observation slit ribs. However, I now lack laminating brushes. Even if I try to clean them with acetone they will become too stiff to use. So the brushes become disposable. With ordinary paint brushes costing serious money this would increase the cost dramatically.

I need a source of cheaper 1" brushes to paint on the resin and stipple the wetted glass mat. The bristles are usually neutral in colour. So lost hairs do not show up glaringly in the lamination. I still have suitable laminating rollers from my past fibreglass exercises.

Luckily I just found a boating shop which sells disposable 1" brushes for laminating. Duly ordered but the weekend gets in the way of delivery. I should have checked properly when ordering the resin and glass mat. I never noticed the tiny size [10mm.] 

They used a product code on the website instead of a size and I never noticed! Showed three sizes in their product sales image but sell only two. 

I can use the time constructively to abrade the surfaces to be laminated. Adhesion would be poor unless the surface is keyed with coarse abrasive paper. I'd better wear a dust mask under my visor. 

There are some spare fibreglass off-cuts on which to practice. To see if I need power tools to make an impression. There are two very different surfaces involved. Rough interiors and shiny smooth, gel coat exteriors. The inside is not cosmetically important. While the outside is. Fortunately the dome will be raised well out of reach for close, visual inspection. Though, naturally, I shall be doing my best to achieve an acceptable finish. There is always car body filler to improve the appearance.

I spent the afternoon working on the geometry of the shutters and slit ribs. Repeatedly sawing off the bottoms of the ribs. They were much too high and need to be brought down even more. At the moment the shutter ribs are resting on the slit crossbars. Which are flush with the top edges of the slit ribs. Which provides no [weather seal] overlap between the ribs. I shall have to unscrew the crossbars and fix them lower down on the slit ribs. It feels very hot working in the sunshine.

I removed two crossbars and lowered them on the slit ribs. Thunderstorms are due in a little over an hour. So I have closed the shutters again and tidied everything away.

*