Mike builds a teardrop (Mega update 3)

[Mike G]

Mike, really impressive work!


Will you be having a removable cover protecting the front from stones and sand being thrown up?

Our roads have tarmac, Phil.

 

[Lons]

Phil has valid point Mike.

When we had a caravan in 2017 I had a clip on proprietory canvas cover to protect the front from stones flung up from the rear wheels of the car, an issue dispite fitted mudflaps. keep your eyes open when out driving and you'll see they're very common.

I don't know how much damage would be sustained on glassfibre compared to aluminium but worth considering perhaps if you're interested in keeping it pristine.

 

[Mike G]

Yeah, I let an attempt at humour take the place of a sensible answer. I think the sensible thing to say is that most of the lower half of the front of the teardrop is behind the tongue box, which will have a painted canvas finish. I could put a square of perspex over the exposed bottom corners , I suppose......although there is a front marker light there to get around. Or, as you say, I could make up a custom canvas cover held in place by screw-on press studs.

 

[Phil]

Our roads have tarmac, Phil.

We do have some tarmac roads somewhere in the country
Our local street out of our area (only one) is more repaired potholes than proper tarmac, and we are not even in the rainy season yet!

 

[Lons]

We didn't have problems finding tarmac in south Africa but avoiding people and cows on the motorway was a different matter.

 

[Mike G]

It's been a while. To be honest, I've been a bit fed up with this thing, which seems to be taking forever, so I had a few days off.

There are going to be 3 or 4 updates to bring us up to the present. This evenings post is about stuff I did 2 or 3 weeks ago now. I started by tackling the rear hatch........

The rear hatch slides into place on a long continuous hinge (more on that later), and so the wiring for it needs to be take-apart-able. All the driving lights are on the hatch, and one or two other things besides, so there are lots of wires to deal with. Further, it is the only place on the entire teardrop where wires run within the structure. Again, more on that later.

I started by turning a little boss from a scrap of sapele, and working out the necessary hole:







The flexy- ducting in actually a bit of waste water hose left over from the galley sink. Whilst I had a path to the lathe cleared, I turned up a quick prototype knob for the kitchen and bedroom cupboard doors, but it turned out to be too big. Now that I'm a professional turner, these things are pretty easy for me .....



I hope you get the irony.

This is the underside of the kitchen hatch, with the ducting in place, the light in place, and some cut outs for the electrical connections:



Now all I had to do was wire it:









Note the bundle of wires with the black tape around them. They are all spares. If for some reason I have to install raised lights, or a reversing camera, or anything else, this is my only chance of getting any wires into place. One annoyance was that the kitchen light had cables which weren't long enough to reach anywhere where a joint would be accessible. I decided to solder them. Here they are taped up:



The cut outs in each corner are obviously behind the driving lights, meaning that if they ever need replacing the wires are accessible:





I also inserted a couple of draw strings, so if I did ever have to pull more wires into place, at least I'd got a chance. Having finished all that, I could start on the cedar strips:



I'm trying to follow the colours of the roof down through the hatch, but as the roof is covered in epoxy it's hard to directly compare my stock with what's on the roof. I graduated my stock from light at one end to dark at the other:



.........and just carried on working in from the outsides:





Time for another batch of epoxy. If you recall, you can either build up epoxy in layers before the previous coat has completely set, or you have to achieve a mechanical bond by sanding to key the surface:





It's a horrible job.

The kitchen hatch needed fairing:

 

[AJB Temple]

One word. Lovely.

Another word. Boat.

 

[Mike G]

That meant belt sander across the grain, then with the grain, then torture boards:



Then on a nice dry warm day (ideal for epoxy work), I put 3 or 4 coats on the hatch, and a couple on the teardrop:





Unfortunately, the farmer decided that afternoon was a good day to plough up the dusty dry field, and we also suffered a cloud of little insects who decided that drying epoxy was a good place to land. Time to walk away and do something else.....

I had sent a cutting list to a Formica supplier, and went and collected all the various pieces. Contact adhesive has turned into something rare and expensive, for some reason.....but it's the only way to stick Formica down. You may recall that the kitchen worktop was an old hollow core door, for lightness. Well, it was soon to look a bit better:







I hate trimming bits! I hate routers.....



I'd even taken the precaution of taping up the front edge so as to give myself some peace of mind.

Time to walk away and find something else to do.......

I cut away some of the depth of a stainless steel vent, as it was deeper than the tongue box floor was thick. It's to vent the box as it's a gas store:



-

It's the easiest thing in the world in Autocad to offset a line and add a radius to the corners. You may recall this drawing from last year:

Note the line inside the edge of the teardrop, following it but with rounded bottom corners. That took 10 seconds to draw......and a week to build. Here's the process.

Firstly, a ripped up some 27mm oak boards:



Then careful re-sawing on the bandsaw, and planing on the P/T, and I ended up with a whole lot of 8mm thick stock:



Those boards were about 2.6m long, and I needed a couple of pieces 3.7m long. I wasn't sure whether to do the necessary scarfs before or after steaming them, and decided to do it before. I worked out that I could keep the join out of the steam box. I decided to just do half-lap scarfs. In 8mm thickness, it just seemed to be asking for trouble to try to do a tapered joint:







Sorry that's focussed on my shoes......

So, I'd got a couple of boards 3.7m long, and a bench around 2m long. I needed a round-over on both edges. I ended up lowering the table of my pillar drill until it could support the end of the boards, then roughing off the waste with a hand-plane, and then making a scratch-stock:





I made up a steam box, and some formwork:







This is what you're up against when steaming. Here's the springback when it came out of clamps the following day:



Right, that's it for today. More in the next few days.......

 

[AndyT]

I can feel the frustration from here... but really, you are making huge progress. I'm sure we are all so relieved that you've got your physical strength back to do this sort of thing, and I'm sure you will soon/eventually have a finished article that you will be rightly proud of.

 

[Cabinetman]

It’s been a while since I did any steaming, but fairly sure the ends were tied together and left for a couple of days.
I think this is to let all the bits of cellulose and lignin settle back and solidify into their new positions.
Probably ok to just re-cook it, it looks as though it might straighten enough to go back in the box?
Ian
Edit, not sure how or just where those bent bits will go on really?

 

[Mike G]

They go here, Ian:





That's the easy bit. Next up comes the side pieces. First, I made a pattern out of ply and hot glue:



Note the little blocks so that I could put it back in the same position.

I braced it, because it needed carrying 40 or 50 metres to the workshop, and it's fragile:





I then spent quite some time on my knees working out where the individual pieces of oak will start and stop. I was going to make up a little jig to give me a right angle to the tangent at any point.......but then I saw this mitre square thingy hanging in the tool cupboard, and it was perfect for the job:



My stock is 8mm thick. I thought about doing a normal half-lap type joint.......but not for long. I decided to do reinforced butt joints. I spent rather a long time sawing and planing:



I tried a few methods of extracting the angles from the pattern to transfer them to the oak stock:



I had the method completely sussed by the time I came to doing the second side. Anyway, this is what I ended up with:



Nine pieces of oak, all with nice tight butt joints. Now I needed to join them together. After a bit of thinking, I made a router jig:



This referenced off the outer edge of the frame pieces, which had been shaped to the ply template. This meant that when adjoining pieces were offered up together, the cut-outs aligned:





I glued these up in pairs, using lots of tape for alignment, and weights to keep everything flat, and to keep the expanding PU glue from pushing the little oak loose tongues out of the joint:







The following day, I dry assembled the whole lot, and kept my fingers crossed that everything would fit perfectly. It was very close:



That's a cumulative error of 4 joints. Instead of trying to fix just at that point, I took a shaving off all 4 joints (because I didn't have much to play with in terms of the overall outline, which couldn't end up smaller than the teardrop), and it turned out well:



I glued it all up:



The following day there was still lots of work to do. I put it on horses to bring the outline to its final shape:



Note the little protuberances glued onto the inner edge (on the furthest two horses).

I also had the curved pieces in the workshop, to glue on a right angle at the bottom end. Working on them wasn't easy:

 

[PAC1]

You are getting there Mike. It is looking very good and is going to be the centre of attention where ever you go.

 

[Cabinetman]

Wow, that’s a brave thing to tackle Mike, but it’s going to work, obviously, I like the reinforcing bits routed in, and when it’s all epoxied together to form a capping around the edges it will be really strong. Just waiting to see how you cramp it all in place!
The sealant used in these sort of ares on caravans is non setting and flexible, slight worry that the stresses of road travel may break joints ? but tbh you’re building it really well with lots of overlaps so should be ok I think.

 

[Mike G]

Wow, that’s a brave thing to tackle Mike, but it’s going to work, obviously, I like the reinforcing bits routed in, and when it’s all epoxied together to form a capping around the edges it will be really strong. Just waiting to see how you cramp it all in place!
The sealant used in these sort of ares on caravans is non setting and flexible, slight worry that the stresses of road travel may break joints ? but tbh you’re building it really well with lots of overlaps so should be ok I think.

Yeah, I ummed and ahhed about how to stick this in place, but it has to be epoxy finished, and I can't do that anywhere other than in place. To get epoxy over seams of a flexible sealant just seemed like a potential disaster. My thinking is that this teardrop is so small and so strong that it won't be flexing. It's a bit of a monocoque, really. If I get cracks in the epoxy around these capping pieces I'll know I was wrong! For such an insignificant little part its construction is enormously complicated, with all sorts of questions like this involved. As I said, drawing a simple line on the drawing 2 or 3 years ago has led to an awful lot of work, and thinking. I think it will be worth it.

 

[Malc2098]

I was think about how you might clamp the capping in place. It occurs to me that the fit and process is not too dissimilar to the binding of a guitar, albeit a tad bigger.

One of the ways luthiers bind their binding to the instrument body is to continually wrap a material around the body, thus holding the binding into its rebate. Some luthiers use strips of tyre inner type wrapped around the binding and the body, so the whole thing can then be tensioned.

Do you know anywhere where you can obtain redundant inner tubes so you can make rubber strips to wrap around?

 

[Mike G]

I was think about how you might clamp the capping in place. It occurs to me that the fit and process is not too dissimilar to the binding of a guitar, albeit a tad bigger.

One of the ways luthiers bind their binding to the instrument body is to continually wrap a material around the body, thus holding the binding into its rebate. Some luthiers use strips of tyre inner type wrapped around the binding and the body, so the whole thing can then be tensioned.

Do you know anywhere where you can obtain redundant inner tubes so you can make rubber strips to wrap around?

One side is in and done, Malcolm, and went well enough. I have learnt from that how I might do it better, and will be doing it the new way on the other side in the next day or two. Although I can see how giant rubber band might do the trick, I have a simpler solution.

 

[Cabinetman]

Yeah, I ummed and ahhed about how to stick this in place, but it has to be epoxy finished, and I can't do that anywhere other than in place. To get epoxy over seams of a flexible sealant just seemed like a potential disaster. My thinking is that this teardrop is so small and so strong that it won't be flexing. It's a bit of a monocoque, really. If I get cracks in the epoxy around these capping pieces I'll know I was wrong! For such an insignificant little part its construction is enormously complicated, with all sorts of questions like this involved. As I said, drawing a simple line on the drawing 2 or 3 years ago has led to an awful lot of work, and thinking. I think it will be worth it.

Re the small and strong- I quite agree.

 

[Mike G]

One of those curvy pieces curved up, and one curved down, giving me the opposite problem:



Nonetheless, I achieved the joins I wanted:



The inside line of the frame couldn't be done until the outside was finally shaped, simply because the two shapes are parallel. I spent a long time with the frame held against the teardrop, planing down to a true fit with a block plane. Once it fitted, I offered up the awning brackets to mark their final position, which enabled me to shape the oak around the foot of the bracket:







Only then could I cut out the inside line:



Again, there are complications. Of course. This whole thing is just one big complication. The joint for the lid (hatch) splits the black stuff in half, so part of the frame would be cut away in due course. However, it had to be there at this stage so I could use it to mark out the inner edge.

Sometime whilst cleaning up the inner edge, or shaping it for the scratched round-over, I had a catastrophe. It fell off the horses and broke:



Damn. More time.......

Right, the corner detail. This paint lid felt about the right size. I used it to make some templates out of cereal packets:





I used those templates to make the corner pieces. Fixing them in place involved hot glue whilst I marked with a knife, then jig-sawing away the bulk of the waste, then chiselling to the knife lines, and then a final fit, and glue:

















Note the frame clamped securely to the horses! I didn't need another catastrophe.

Once the glue had set I could do the finishing and the round over:



And here's the protrusion around the bracket foot:



I then sponged it all down to raise the grain:

 

[Mike G]

After raising the grain, I smoothed it back down with some sandpaper before applying some incredibly strong tea. When this dried I brushed on my steel wool and vinegar ebonising mix:



....and it all turned nicely black:



Great! I went in for a cup of tea. When I came back a while later, it had turned mauve:



I tried cleaning it off with white spirits:



But that only worked whilst the white spirit was wet. Once it evaporated away......mauve again. I asked on the forum, and did a series of experiments, leaving this phase of the job on hold. I moved on to the tongue box.

I started by levelling the top edge, and adding some thickening in the coopered corners:



After working out where the hinge was going to put the lid, I could then trim the lid to its final shape (above), which allowed me to groove for the flipper seal (router table for the straight bits, and scratch stock for the rounded corners:



Softwood isn't great with a scratch-stock.

This box is going to be finished with an old boatbuilding technique with a variety of names. It is essentially glue-and-paint-and-canvas, and this has been used as "house" roof covers on yachts forever, and as a hull on framed canoes for centuries. Of course, nowadays people think it is a new idea and it's now called "poor man's fibreglass" (PMF).

It starts by gluing some dust sheet (scrim/ hessian/ coarse muslin....) down to the thing you want to cover using a waterproof wood glue:










This will then get painted. However, before I could get onto that, I discovered the answer to my ebonising issue (wipe away the excess solution moments after brushing it on), and could get back to the main job in hand:





Before I could stick those in place permanently, I had to do a rebate for the hinge. When I had built the lid I didn't have the hinge, and so had left the normal penny-gap. When I got the hinge, I realised it need to be much bigger, so whilst the roof was still flat I clamped on a sheet of ply to act as a guide for a trimming router (yes, I should know better!), and routed a rebate in the roof lower edge:



This suited the hinge nicely:



The hinge is a couple of continuous aluminium extrusions, known variously as a snail hinge, a hurricane hinge, or a catering hinge (because burger vans etc with a lift-up lid in their side always use them). Correctly fitted, it's waterproof.

 

[Mike G]

Here it is with the other part of the extrusion:



The screw is there to balance it to hang roughly in its closed position, showing the large gap required. The gap is useful, because it means that screw heads have plenty of room without fouling the closed hatch. It is also a potential route in for water at each end. More on that when I fit them.

Somehow, I missed a line of photos from my previous post. Here is the curved corner piece being added to one of the steam-bent capping pieces. Note the bit of arris I had to cut to give me some sort of surface to work on:





Yeah, I know. Completely nuts. I had designed the 90 degree corner inserts without considering this truncated pair. They're short because they finish either side of the tongue box.

Here's a photo of the world's strongest tea:



....and said tea being spread on the frame prior to ebonising: