The original JT-5

Plug Construction
Click each thumbnail for a larger pic.

19th Feb. We've actually begun the mould with the first (and second) application of Gelcoat. I've started a new page to cheer myself up.
JT-5B Cockpit Mould Construction

16th Feb. Last night we moved from 180 to 400 grit paper and are now sanding wet. The finish is coming up OK but is taking correspondingly longer with the finer paper. We were initially sanding by hand as we didn't like to use the orbital sander wet. However, in light of the amount of progress we made in an hour we've moved back to power and the progress has improved markedly. Current estimates (and you know by now how accurate my estimates are) say that we'll be finished with the 400 tonight. I haven't included any pics as there's really no point, they look just the same.

12th Feb. Due to family commitments, I didn't get to the laminating stage yet. Still some sanding to do before polishing. Onward and upward (hopefully)

9th Feb. Things never seem to go just as planned. Since I last updated these pages, we've had a strange effect, where the timber ribs or bulkheads in the form seem to have shrunk relative to the plasterwork. Whether this is a temperature or humidity effect, I don't know but the end result is that they are visible as indentations in the surface of the plug. The effect seems to take some time to appear as we just noticed it when the plug was left for several weeks over Christmas. The current plan is to sand back flat and spray several coats of the primer, wet on wet. Following this we will sand and polish as quickly as possible, fit the parting boards and start laminating. We think that if we can get the mould done within a week of the final painting, we should be OK. The consequences of our guessing wrong are just too horrible to contemplate.

19th December.
Some more pics of the final undercoat with the proud parents standing by. We just need to remove orangepeel and spray some coats of finish now before more sanding and AT LAST - Polishing. These pics were taken (by Ken) with an Olympus digital. You can see in the centre pic, he's using the neato remote to trigger the camera. The results are clearly much better than the ones below although it's probably an unfair comparison, as the pics below had no flash.

30th November.
The long promised images of my (poor) paintwork. I took these using the still image function on my new SONY which has no flash. I was tricking about with the exposure which produced the different colour cast on the last image. If anyone out there has a flash which will work on the Intelligent Shoe (other than the specified SONY accessory), I'd be pleased to hear about it.

9th November.
No pic here yet but we've got two coats of Acrylic Latex on the form and it's looking good. Lots of small imperfections but the general body is very satisfactory. More paint tomorrow and I'll add the first painted pic then.

7th November.
Here's the last stage of filling before paint. You can see the piebald effect caused by mixing in colours to show the last layer of plaster. I'm applying the very last skim here. I can't say how pleased I am that the plaster stage is complete. My hair and beard will be delighted, not to mention the ol' nasal passages.

28th October.
I've been waiting until I had a decent new photo of some real progress before making this update. However, despite having spent the last six weeks sanding and filling, and sanding and filling, and .... well, you get the picture, I'm posting this update. It's principally to assure folk that I'm still working and haven't given up the ghost. The cycle takes about three days and goes as follows; sand the previous sessions filler until all of the high spots have been reduced and any remaining (ha, ha) low spots are revealed. This takes about two hours for two of us. Then mix up some Board Finish plaster and fill the low spots, another hour or so. Then we wash up and retire for a cuppa. The plaster takes about 48 hours to harden fully and we're off again. Currently we've got about 90% of the total area sanded to shape and 10% as roughly filled low spots. Each low spot now is about 4 square inches. Hopefully (I've given up predicting) another session will bring us to low spots of less than a square inch and after this we'll be ready to paint. I'm going to post an update once a week from today whatever the progress.

15th April.
After the last bout of sanding my wrist has given out again. Nevertheless, we're almost ready for the first coat of primer. We've been using the timber sanding splines about 24" long and they've worked quite well. I stopped midway and fitted small timber blocks which helped a lot. I'm now going to replace them with small timber knobs because the edges of the blocks are quite sharp and due to the heavy pressure necessary during sanding, are quite uncomfortable on the little ol' hands.

5th April.
I decided to wait until the entire plug was finish plastered before painting. Here's it is, inverted again and with a first coat of finish plaster applied. Due to an error in my sections, we had to build up an area almost an inch near the centre. The thicker patch is taking longer to dry out and the darker colour shows up clearly.

25th March.
I've been out of the workshop for most of last week and today was devoted to making a pair of light stands. The section of basement I'm using is not well lit and I was finding it quite difficult to see the surface contours. Finally, I forced myself to suspend work and solve the problem. I decided that the quickest way was to modify my water level by making a pair of plug-in extensions to carry the lights. I'm very pleased with the results and just sorry I didn't stop much earlier to make the mods. The original stands are made from 3/4" x 1/16th alloy tube fixed into old engine flywheels. The extensions are 5/8 x 1/16th with the bottom 2" reduced by .015" to allow an easy fit. The top has an alloy plug Loctited in place, drilled and tapped for a bolt to attach the lamp. The lamps are a pair of cheap ($20) 500W security floods with the PIR motion sensors disabled. I may modify the tube joints to provide articulation later if I think it's needed.

15th March.
Here's the first pass at shaping the nose-cone. I've got a coat of finish plaster on and have started sanding. The advice on finishing was to make flexible sanding splines from timber and use Aluminum Oxide abrasive. For the princely sum of £27+tax (about $40), my local industrial abrasive supplier sold me a 50M x 50mm roll of red AlO abrasive tape. I cut some timber strips, about 30x6mm and fixed the tape with spray-on contact adhesive and proceeded to sand. It's quite tedious as the plaster clogs the abrasive quite quickly and I have to wirebrush after every dozen or so strokes. Luckily, the plaster is quite soft and progress is fairly rapid. After 15 mins the nose has reached the stage where the high spots have been removed and low spots have been revealed.

11th March.
Last night I successfully inverted the assembly and I'm glad to be able to report that there was no damage. In the absence of anyone else, I enlisted the assistance of my old friend Archimedes and between the two of us the task went very well. When dealing with heavy, unweildy items, it's best to plan ahead carefully. I'm working at one end of my workshop and as you can see in previous pics, the clutter is extreme. I had to do a little tidying to make some space. I positioned the trolly so that when I jacked up each end ( to remove the trolly ) I had enough space left to rotate the mass about the pod axis without fouling. Having checked all about for potential interference - several times, the actual turn went extremely cleanly. The 3D cockpit shape is becoming clearer now. My younger daughter enquired whether it was going to be uncomfortable sitting in among all those things!

9th March.
Back in action, wrist much improved. Having had a couple of weeks to think about it, I realised that finishing the forward deck section of the plug to the required standard would be almost impossible while upside down. This means turning the whole shebang through 180 degrees. Because the forms are not actually fixed to the beam and the total weight is now about 100 Kgs (220 Lbs), this is a little risky, so I decided to do it now, before any more effort is invested. Any damage caused should be relatively easy to repair, as the surface is still unfinished. In order to facilitate the move, I made a cradle as you can see in the pic above. I made paper prints of sections 6, 13 and 20 and stuck them to some old cupboard doors I had. This made it simple to cut out the female sections using a jigsaw. The plug is sitting on a trolley on top of an old solid door. My plan is to strap the cradle to the door using baggage straps and rotate the lot. This will ensure that the plug is supported in the best way possible during the turn. The cradle is 36" tall and will hold the plug securely, at a good working height. Once the forward section is finished, the plug will be inverted again for finishing the main body. Also, when it comes time to laminate the mould, the cradle will become a permanent fixture, doing dual duty as stand and stiffener. Waste not, want not.

As an aside, you can just see my homebuilt Timber Bensen blades, with the stainless noseweights, hanging on the wall in the background.

6th March. Unfortunately there has been no progress since the stage above. I injured my right wrist and have had to - temporarily - hang up the trowel. It's improving daily but it'll still be another few days before I get back in action. In the meantime, I'm assembling materials and planning the next steps.

27th Feb. The Rocketeer.
Plug with transom and fin faired with two part foam. The foam has been sanded roughly to shape. The plug has had a coat of finish plaster to fill most of the small irregularities. There are still some hollows between the sections which need to be filled out to allow final shaping. I'll be using 'board finish' which is a much softer and easily sanded material. I've used half of a plastic container at the transom end so that I can produce a smooth flange in the mould. The intention is to produce a flange of 3 to 4 inches wide, all around the mould. A large smooth flange facilitates the vacuum bagging process by providing lots of space to attach and seal the various layers involved. More on this later.

24th Feb.
The plug is now completely filled with bonding plaster, a total of 60 Kg having been used. The fin was a pig to shape but with perseverance it's turning out OK. We resorted to stuffing in some chicken wire to hold up the plaster. If you look closely you can see the rear section is incomplete. I really should have shaped it sooner but now I've decided to fill it with two part urethane foam and just use the finishing plaster. I hope it'll be OK. There's a small amount of shaping to do behind the fin also and I'll also use the foam here. You can see the 12 mm dowel protruding through the fin part of section 19. That'll be sawn off tonight. Total time so far is about 30 man-hours, including the AutoCad work. Mixing plaster wouldn't come high on my list of enjoyable pastimes. The plastering so far has occupied three sessions, each of two hours. I was helped with this by friends - Paddy who has a KR-2 under construction and Ken who flies gliders.

23rd Feb.
The plug partially filled. My daughter calls it my Armadillo. I used 'Bonding Plaster' on the foam. Scraping this off, flush with the sections, leaves a segmented shape, allowing room for the finishing coat which will be sanded to a fair curve. The form above contains 30Kg of plaster so far. Jukka suggested (too late unfortunately) that I could have laid up a glass skin over the wires, leaving just the 10 mm to fill thus giving a much lighter structure. If I were to do it again, that's the approach I'd take. At this stage, I'm very glad I used the aluminium because the weight would certainly have distorted a timber 2 x 4.

19th Feb.
The sections spaced using 96 mm foam blocks, giving the overall section spacing of 100 mm. Section 1 is a 40 mm disc fixed on a 12 mm stainless rod. I'll use a larger tube over this rod, to leave the correct aperture for the pot pitot I'll be using. Section 2 is fixed to the front of the tube with Isopon (Bondo) taking care to have it square in all planes. The remainder are set from this, and squareness was checked and corrected about every four sections. The wire reinforcement is 1.6 mm copper coated welding rod threaded through holes drilled roughly 10 mm from the edge of each section.

17th Feb.
The framework for the plug at an early stage of construction. The individual sections were drawn up in AutoCAD and lasercut from 4 mm MDF, to fit tightly on a 100 mm square Aluminium tube. Aluminium was chosen over timber for straightness and dimensional consistency, also 'cos I had a length hanging about cut to length for the building beam of my Hummelbird. I'll recover it afterward so it can resume waiting for its true vocation.

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