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20170627_210550_New Quay Court

Finished posts, coated with tung oil

Well progress is definitely happening.

20170622_185235I cut out my blanks for the samson posts on the bandsaw.

20170625_184644_New Quay CourtThe time consuming part was shaping the top of the post. I had made a pattern for this.

There are a variety of ways of cutting a concave curve. The method I chose is essentially the same as making a housing, but using a gouge rather than a chisel.

20170626_170958_New Quay CourtHaving marked the pattern all round, I cut down to the lines with a tenon saw. Then I cut out the waste, trimming carefuly down to the line. Having down this on two opposite faces, it was simply a matter of removing the waste between the finished lines.

The second pair of curves were effectively marked with the saw cuts. So I just drew in the curve and repeated the exercise.

The rest of the process was the same basic technique as spar making. You turn the square octagonal, then 16 sides, then sand smooth with 60 grit paper.

Of course it all takes time, and care, smoothing out bumps and getting curves that feel good. But really, like so many things, the path is simple if it is done in the right order.

Finishing off I used my favourite tool the cabinet scraper, which saves hours of sanding.

I had to glue an extra piece on the flare at the back, because the timber stock I had available was not quite wide enough. This was only a thin taper. But it is worth mentioning that when this kind of thing happens, the extra piece should be kept chunky and oversize. It is much easier to glue on a decent thickness of wood, because it remains stiff. If I had shaped the thin taper first, it would be very hard to glue it on and would bend all over the place. Glued on oversize, it was just a matter of planing flush, band sawing off the excess, and planing the taper.

The finished posts look well. I have oiled them, and tomorrow I will dry fit them. Then they will be varnished before going in place.

20170627_210550_New Quay Court

Finished posts, coated with tung oil

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20170626_121102_New Quay Court

The  knock down portable work bench

One of my favourite principles in doing pretty much anything is what I call ‘circuits’.  It’s all about getting the energy you are putting in, precisely to the place you want it.

Anyone familiar with metal cutting equipment like lathes and milling machines knows that a great deal depends upon stiffness.  The tool and the workpiece must be held rigidly.  When the tool is presented to the workpiece, any ‘slack’ in the physical path between the tool holder and workpiece will be taken up before cutting happens, causing wasted energy, inaccuracy and vibration.  The ‘circuit’ between the two must not have any energy leaks.

The metal worker, operating at thousands of an inch or less, knows that these ‘leaks’ are visible enemies, and will destroy his work.  They will cause the workpiece to deflect, set up vibration patterns, even cause ‘dig ins’ as the vibration pattern is superimposed on the force attempting to cut.

The woodworker is operating at bigger tolerances, so this problem is not so obvious. When a piece of timber moves as it is sawn, it is often just accepted.  When it bounces as it is struck with a chisel, it is accepted.  When the workbench wobbles as a piece is planed, it is accepted.

Well, not by me.  The point is that *any* slack in the system creates an enormous loss of power and accuracy.  I don’t really think many people realise how much energy is used in moving stuff around, rather than cutting, and what this actually means.

For example try this experiment.  Secure a piece of 1″ x 1″ wood in a vice so it is sticking out about 10″  Then try to cut it with a saw about 6″ from the vice.

You will instantly notice that the wood will vibrate as you cut it.  The energy you are using starts to fight against you.  The vibrating saw cut jams the saw.  It is impossible to cut a straight line because the wood always wants to bend.  The jamming of the saw causes the saw to vibrate and the wood to bend even more.

Now try the same experiment cutting very close to the vice.  All the thrust on the saw goes into cutting.  It is easy and accurate.

The difference between these two experiments is pretty obvious.  Cutting at a distance from the vice turns the wood into a spring that absorbs the energy of the cut, and then releases it in an unhelpful way.

If you properly secure a workpiece in an immovable vice, the effect is astonishing.  Cuts are effortless and take a fraction of the time. you can be stunningly accurate, paring off transparent shavings.  Everything is way, way better.

Securing your workpiece and cutting it close to the vice or clamp is second nature to craftsmen.  But how do you know your clamp is secured? What is going on between that clamp and the ground, and the ground and your feet? All you need is a slight wobble, a slight give in your bench, and all that sharpness vanishes.

A workbench is like a system of springs between you and the workpiece.  As you apply pressure to a workpiece the springs give, absorbing your cutting energy.  The more they give, the more energy is absorbed.  Only at the point that the wood you are cutting cannot resist the force of the ‘spring’, will the wood actually cut.

If there is any slack in the system, your workpiece will travel the distance of that slackness before it is cut.  So you are cutting a moving target, that springs back as you cut it.  The result is far lower accuracy and far less cutting power.  Even a small amount of spring makes a massive difference.

One question that came up some years ago was whether it was possible to construct a mobile workbench with very high stiffness, that could be taken apart easily.  Here is my solution, that is still going strong.  It could certainly be improved upon, but it is way better than most static workbenches, let alone mobile ones.

The basic principle that is essential in a mobile bench is that the circuit between the operator and the bench must be closed.  In practice this means that the bench must include a floor on which the operator stands.  The good old Workmate actually does address this, by having a platform you can put a foot on whilst using it.  But it is extremely springy, and the modern version is very poor quality.

My solution was to have a portable floor.  I made this from OSB, but I think a good quality plywood would be better,

The easiest way to describe it is to show you how I put it together.

Components are the floor, a base, three legs, the bench top/vice and three clamps.  The whole thing takes a couple of minutes to knock down and build, and easily fits in a car.  The bench part has only a single M12 bolt holding it together. The bench and legs are made from Keruing, a hard dense and heavy tropical timber, that I happened to have on hand.  I would recommend a heavy hardwood, because the mass definitely helps.  The base is softwood.

20170626_115524_New Quay Court

The components.

The base that holds the bench is made from two pieces of timber in a ‘T’ shape. The  upright of the T is dovetailed into the long part.  The ends of each part are mortised to take the bench feet.

20170626_115555_New Quay Court

Softwood base, dovetailed together

The bench itself is two pieces of hardwood, that clamp over the legs.  The legs are half-dovetailed into this, to that once the two pieces are held together, the legs and bench form a rigid structure.

The third leg is bolted through the bench.  This bolt is the only fastening holding the whole thing together.

20170626_120136_New Quay Court

The third leg.  This bolt is the only fastening!

Once the bench is fitted to the legs and the bolt loosely done up, the whole thing is placed on the base and the tenons on the legs slotted into the mortises.

Then the base is located on the OSB floor.  The floor has captive ‘T’ nuts underneath that take the bolts that go through the base.  The bolts pass through timber clamps that fit the angle of the legs, and effectively create a kind of dovetail effect.

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The clamps bolts the bench to the base and create a dovetail effect on the legs.

This structure is amazingly rigid.  With forces along the vice, it is exceedingly stuff, better than most static work benches.  There is a small amount of lateral movement owing to the flexibility of the OSB but I have got around this by putting weights on the floorboard, or wedges underneath it at the back. An updated version might include stiffeners for the floor board.  I tend to use the centre of the vice for sideways loads, as the forces are resisted very well by the rear leg.

20170626_121102_New Quay CourtIn using the bench, one stands on the board.  Thus the circuit between the user and the bench is always fixed.  You can stand in front or behind.

The vice is fairly primitive, using captive nuts and 16mm studding.  At the time I had only basic metalworking equipment.  Ideally I would have sliding bars to prevent racking of the vice, and maybe handwheels.

Some kind of stop could prove useful. You could even put an end vice on it!

20170626_121722_New Quay Court

In action, turning a chunk of oak into a Samson post

 

Eeek!

20170618_164409_New Quay Court20170618_164405_New Quay CourtFor years my lovely gaff cutter has been hanging around next to our massive houseboat project, sadly neglected.  Time to find out what is going on.

I knew that the starboard side deck and after deck had rot, so off they have come, revealing the bones beneath.  It is a painful thing running a circular saw across your boat’s deck.

Well, it’s not too bad.  The eyebrows had to shoot up at the timber selection of some of the deck beams.  My goodness, some serious grain run out, to the point where a couple of the half dovetails have parted.  Still these will be fairly simple to replace.

A bit more thought will have to go into a section of the carline, which is certainly rotten at the top edge.  I’m not yet clear how far it goes, but it may be a case of scarfing in a repair.  I certainly want to avoid replacing sections of it.

The samson posts on the aft deck have decayed sufficiently to weaken them at deck level,  One problem was insufficient clearance between them and the transom, so water has been trapped.  I’ve made a new design that gives me  a bit more clearance.

20170622_181754

The timber I have to hand does not quite fit the new pattern, but I’ve found some that’s close enough and I can get away with a small shim to make up the extra width.

It’s always fun searching around for timber that fits a shape, and then revealing the inside.   This piece is a 5″ thick board of oak I have had hanging around for about twenty years, and the grain matches quite well to the angle between the sloped transom and the more vertical post.  My lovely Sedgewick planer and bandsaw will do the rough work…20170622_185235The worst rot revealed by lifting the decks was unexpectedly in the port quarter block, a sizeable chunk of timber that connects the beam shelf to the transom, provides corner strength and holds one of the large iroko davits.  This is sufficiently decayed to merit complete replacement, so I’m fishing around in the wood pile for something that works.

Deck plywood has arrived from Robbins, and bronze nails, so I’m really looking forward to quick progress!

We’ll see…

In accurate large scale work, long straight edges are often essential.  But how do we get to an edge that is really straight over a long distance?

We can use chalk or string lines or lasers, but here is a low tech method that does the job very well and quite fast.

This came up in a project involving constructing a 12 segment yurt floor in plywood, and I wanted a straight edge 8 feet long to draw along, and also as a fence for a circular saw.  I happened to have some 6mm ply in 300mm widths, so I used a piece of this.

A good width for a straight edge is very useful.  It makes it much stiffer, and also offers clamping opportunities well out of the way of the business edge.

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Laying out the stock on a surface

To check whether an edge is straight or not is really quite simple.  Lay the piece on a surface and draw down the edge.  I used the back of one of the plywood floor sheets. I use weights to hold down the ply, otherwise the pencil can creep underneath and give a false edge.

IMG_0153

Draw tightly down the edge.  Use weights to avoid any gaps

Then flip it over and match it up with the drawn line.  If the edge is straight, it will perfectly match the line.  If not, the actual edge and the drawn line will be mirror image curves.  My edge was not straight, but convex.

Now I can use the drawn line to help mark a proper straight line on the stock.

I aligned the stock with the drawn line, closing the gap as far as possible.  In this case the edge was slightly convex, so the stock touched the line in the middle, leaving gaps at the ends, which I equalised.

IMG_0154

Transferring the line

Then I set up a gauge to the widest gap.  Moving along the drawn line I transferred the drawn line at regular intervals onto the stock.  You don’t need anything fancy, a piece of wood with a 6mm notch cut out of it would do.  The main thing is to have something set up to the fixed distance. This is much better than repeated measurement.

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Near the centre at the widest bulge

This left me with a line of marks on the stock that was a mirror image of the actual edge.

Then at each transferred point I marked, by eye, half way between the point and the edge.  This new line of points had to be a straight line.

IMG_0157Then it was simply a matter of joining the dots with a batten,

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The straight line is half way between the edge and the transferred points

and planing down to the line.

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When I retested it, the edge was spot on straight.

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The drawn line fits the flipped straight edge exactly

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A clearer view of the flipped line, shifted sideways

A simple but effective way of creating an accurate straight edge!

Points to remember are:

  • make sure the edge of the stock is firmly down on the drawing surface
  • use a sharp pencil for a clean line
  • use some kind of gauge to transfer the line.  A piece of wood with a cut out the thickness of the plywood would do.  The great thing is to have a fixed reference.
  • a long soled plane will be quicker and more accurate.  Clamp the stock firmly.  I just clamped it to the stack of plywood, because it was more convenient than taking it to a bench.
  • Label the straight edge!  It is easy to forget which edge you have straightened…
20170414_162433_New Quay Court

Oh dear.  The old sack barrow stripped of its metalwork.

I don’t remember when or where we got it, but hanging out in the garden for years we’ve had an old sack barrow, made from timber with a forged frame. It was worm ridden when we got it, but I’ve always had my eye on it. One day, I said to myself, I will bring you back to life.

20170414_142008_New Quay Court

Brought back to life!

Having had an epic day tidying the timber pile, sorting through and reminding myself of the contents, and having ‘spring cleaned’ the workshop, my gaze fell on the sad remains of this antiquated object.

“Perhaps we can stick it in a corner and train sweet peas up it?” was Martine’s suggestion.

I don’t think so. My journey though the wood pile had revealed a board of oak that had straight grain except for, at the end, a curve around a shallow knot, which was exactly the right shape for the handles. It was providence talking to me. It had to be done.

20170412_132008_New Quay Court

A bit of luck, straight grain and then exactly the required curve at the end

I stripped off the old metalwork. Everything was sound except the wheels. I happened to have some spare pneumatic types in the shed, although the axle bore was 20mm, rather than the chunky 1” axle on the old ones. Various thoughts occurred to me about that, possibly making a new axle, or swaging down the old one on the forge to 20mm. But I didn’t really want to change the old one. I really liked the way the square section had been housed into the wooden frame and through bolted to the carrying fitting. Good design. So I decided not to think about that yet. Something would turn up.

Having ripped up the board and planed the pieces, I located the curved grain I would be using for the handles and worked from there. I clamped the pieces together and marked the cross strut locations on both at once. Then to get the angle of spread I screwed the metal frame to the stiles.

20170412_131938_New Quay Court

The old version had through mortised stiles and wedged tenons. But the cross struts had no shoulders. This did not make sense, because the frame would be held in compression with the steel tie bars, so properly the struts should have decent shoulders.

To mark the joint locations I laid the stiles on the cross struts, aligning them with the marks on the stiles and checking the angle was the same each side. Then I scribed the stiles onto each cross strut, and the cross struts onto the stiles.

Because of the spread of the handles, the mortises were obviously angled. These I marked in the usual way with a mortise gauge. I always knife in the ends of the mortises to provide a register for the chisel. I removed the waste on the drill press being careful to leave a margin to avoid the hidden undercut. Then it was chisels to cut to the lines.

20170414_141910_New Quay Court

I like to cut tenons by knifing in the shoulders first and cutting out a V groove with a chisel for the saw to slide in. This method is very quick, and so accurate that I rarely find any tuning of the shoulders to be necessary.  I have found that for this to work really well, the knife cut must be perfectly vertical.  If it is inclined the cut does not provide an accurate enough surface.

20170414_154929_New Quay Court20170414_154938_New Quay CourtTo work the handles I drew a ‘progressive’ template on hardboard. I needed to take the knot out, so I drew a curve that did that, cut it out of the template and drew it on the stock. I removed the waste with cross cuts, a gouge and a spokeshave. Once I had a fair curve, I drew in the other side of the handle on the template and cut that out. Then I copied that to the stock and cut out. This all looked good, so I faired up the end on the template and copied that to the stock. Once that was looking good, I flipped the template over and drew it on the other handle and cut to the lines. Then it was smoothing up and rounding over until it felt good.

20170414_141922_New Quay Court

Go on, you really want to grab it.

My new tyres were a little bigger than the old ones so I adjusted the size of the timber axle bearers to suit. I fastened these using big screws, predrilling the clearance holes and screw head hole on the drill press. Later they would be drilled for bolts to hold the axle, but I could not do this until I had located and housed it.

Before going further I decided I would clean everything up and put in the finishing touches. I used a trimmer with a chamfer bit, held in the vice, to cut the stopped chamfers on the cross struts. Then I went around the whole frame with a 1/8” round over bit to take off the sharp edges.

20170414_162536_New Quay Court

Stopped chamfers thin down the appearance in the middle, but leave a sense of solidity at the ends.

I always clean up with a cabinet scraper. It’s much faster than sanding, and leaves a fine finish. It is really worth learning how to sharpen these quickly. The cabinet scraper is one of the most useful tools – if it is sharp.

The tie bars were in 12mm hot rolled steel. I turned the ends of these down to 10mm on the lathe and cut threads on them. The holes had to be drilled carefully because they are angled relative to the stiles, and the rod has to fit through both exactly. After inserting the ties and pulling it all up tight, I cut off the protruding tenons flush with the handles.

20170414_141855_New Quay Court

With my thoughts on the lathe, it occurred to me that I could deal with the discrepancy between the 1” axle and the 20mm wheel bore, by knocking out the wheel bearings and making some delrin ‘top hat’ bushes to fit the hub. So I turned those on the lathe to a nice driving fit.

20170414_141831_New Quay Court

Housings cut.  The white delrin bushes are visible in the hub.

I located the axle on the chocks and scribed the edges of the housings, cutting them out with a tenon saw and chisel.

When I knocked the axle into place that gave me my hole location. The other side was an existing hole on the metal frame. So some careful drilling from both sides gave me an 8mm hole to take a long coach bolt.

The rest was just a final sand over and a coat of tung oil!

One rather nice thing about this project is that it was entirely made from stuff I already had lying around.

20170414_142141_New Quay Court

New and old!

So having half lapped the rubbing post stock, shaped it and tidied it up a bit, it was time to bore some holes.

The posts were to be bored through the width (about 6”) with a 13 mm hole to take a length of 12mm stainless studding. The outboard edge needed to be counterbored so the nut and washer were below the surface.

Jig showing guide plate and 'legs', screwed together

Jig showing guide plate and ‘legs’, screwed together

The procedure I used for boring the holes is very familiar to boatbuilders, but with a couple of refinements.

Having set out the locations of the holes, I squared a line across the face and both edges. I found the centres of the edges, and punched the hole location on both sides. I almost always punch holes I’m going to drill. It ensures that the hole is spot on.

The principle of drilling a hole that is perfectly square to the edge and parallel to the face is to construct a guide jig that will support the drill some distance above the hole. This guide is a small piece of wood drilled to the same size at the hole. By positioning it exactly over the punched location of the hole, it will guide the drill along exactly the right path.

To construct this jig, I took a small offcut of 18mm plywood and ripped it to the thickness of the post. By sliding the post up to the circular saw blade, and the fence up the post, the exact thickness was captured on the saw. The offcut was ripped to this width.

Then I found the centreline on this guide piece, and then punched a mark in the middle on that centreline.

This I drilled out with a 13m drill.

I found two more long offcuts and screwed these to the edged of the drilled guidepiece. The jig is pretty obvious from the photographs.

The other requirement was two spacers, made from another offcut about 5 inches wide, with parallel sides, which I cut in two.

Jig initial set up

Jig initial set up

To align the jig, I lightly clamped it in place and slid the 13mm auger bit I was planning to use, through the hole, with the tip resting in the punched mark.

Spacers set up. The idea is that, because the spacer edges are parallel, the squareness of the square is 'transmitted' to the drill bit.

Spacers set up. The idea is that, because the spacer edges are parallel, the squareness of the square is ‘transmitted’ to the drill bit.

With the combination square resting on the edge, I placed the two spacers in position, one sitting in the edge and the other on the top of the jig. By pushing the jig towards the combination square (a light hammer tap maybe), the whole thing aligned perfectly.

A big gap - the jig and square are pushed together to square up the drill bit.

A big gap – the jig and square are pushed together to square up the drill bit.

A hammer can be used gently to tap it together

A hammer can be used gently to tap it together (terrible photo!)

The drill bit is now aligned to the spacer

The drill bit is now aligned to the spacer

The spacers press against the side of the auger bit and the edge of the square, the jig swivelling until everything is touching. Clamp up hard in two places.

Checking to ensure that the guide is on centre. As it was ripped to the same thickness as the stock, the straight edge should align with the the face of the stock and the edge of the guide.

Checking to ensure that the guide is on centre. As it was ripped to the same thickness as the stock, the straight edge should align with the the face of the stock and the edge of the guide.

To ensure that the guide plate was directly on centre, I set the straight edge against the face of the stock, which just touched the guide plate. If it hadn’t, I would have slackened the clamp and pushed it sideways slightly.

Rather than risk moving anything, I removed the bit from the jig to fit it to the drill, and then re-inserted it carefully. Then it was simply a matter of squeezing the trigger and letting the drill do the work.

Right through the hole...

Right through the hole…

I actually bored from both sides, first counterboring the outside with a forstner bit. But I probably didn’t have to because the holes were so accurate that you couldn’t see any join where they met.

This method is pretty good. For boring really long holes there are better ways, as any bit will tend to wander off course, diverted by the grain of the wood. A good way is to use a boring bar rather like you would bore out a cylinder on a metal lathe. This is often used for boring the stern tube hole in a boat, which has to be very accurate over a long thickness of timber.

The sides of our houseboat are vertical, and make quite a good ‘dock’ for smaller boats. I have my gaff cutter moored alongside, and also we regularly bring boats alongside. Some kind of permanent fendering seemed like a good idea.

I happen to have in my garden a large stack of keruing, which I acquired a few years ago and have been using for various projects ever since. Unfortunately the pieces, although good section at 150mm x 45mm, are only 900mm long, so are often slightly short!

Keruing is a very durable wood, often used in docks, and so I have decided to make up some longer lengths, which will be bolted edgeways and vertically to the side of the houseboat. A horizontal carpet covered board, hung from the side of boat alongside and long enough to bridge two or more of these, will ride up and down these heavy battens.

This is not precision joinery, just a means of connecting two pieces with reasonable strength. I decided on a half lap joint of 100mm. The material was left rough sawn. I cut out the waste using half depth cuts on a chop saw, 100mm from the ends, and the bandsawed to approximate depth. The idea was to plane up the joints with a router.

Some years ago I made a scarphing jig for my router. This involved a base with two rails at a 1 in 8 slope. On this rode an extended baseboard for my router. So I decided to use this baseboard to finish the half lap joints, by building a different jig with parallel rails rather than a slope.

The new jig was cut from 18mm marine ply, 12 inches wide, on the table saw. Some spare 6×2 stock was edge planed, and then ripped into two 2.5” strips. These were screwed to the plywood plywood, ensuring they were parallel.

The extended router base, showing the stiffening battens

The extended router base, showing the stiffening battens

A small piece of plastic tube prevents the router from cutting into the rails

A small piece of plastic tube prevents the router from cutting into the rails

The router base was originally made from scrap 12mm ply. The holes for machine screws to fasten to the router base were located by using the detachable router base as a template. The hole for the bit to go through the base was cut with a hole saw to the outer diameter of a piece of plastic pipe, glued in place and extending 5 mm through the base, to serve as a stop and avoid routing the rails of the base by accident! The whole thing was made more rigid by screwing edge fastened battens along it – to avoid the router’s weight causing it to sag in the middle of a cut.

When making this router base, ensure that it is long enough – it has to be surprisingly long to ensure it is well supported and stiff across the whole cut.

Squaring off the router base

Squaring off the router base

Setting the end stops from the squared router base

Setting the end stops from the squared router base

The accurate positioning of the timber to be planed is simplicity. First, the location of the shoulder of the rebate has to be set. I did this by positioning the router on the jig in a suitable location for the length of timber I was planing. Then using a square, the router base was aligned exactly at right angles to the two jig rails. Two small clamps were fastened to the rails to serve as stops. I checked that this all worked by moving the router away and then relocating it against the stops, and rechecking with a square.

Here’s the procedure to align the stock:

Aligning the router cutter

Aligning the router cutter

Set the router bit by hand so that the cutters are parallel with the rails. Lower the router to a few millimeters above the depth of cut required.

The router base is aligned to the end stops

The router base is aligned to the end stops

Set the router base against the end stops

Two plastic spacers used to align the stock parallel to the rails

Two plastic spacers used to align the stock parallel to the rails

The stock is slid into position along the plastic shims

The stock is slid into position along the plastic shims

Take a parallel edged shim and, placing it against the back rail, slide the stock along it until the rebate touches the router cutter

Take a parallel edged shim and, placing it against the back rail, slide the stock along it until the rebate touches the router cutter.  Clamp the stock in place.

The rebate in the stock touches the router cutter

The rebate in the stock touches the router cutter

If your rails are parallel, and the clamp stops are set accurately, this will locate the stock in exactly the right place to plane off the surface of the lap joint, and clean the rebate shoulder square.

Then it’s just a matter of moving the router away, dropping it to the full depth of cut and carefully planing off the remaining waste.

I had twelve of these to do. Setting up for the next cut was dead easy, as the end stops and parallel shims make it a no brainer!

Another win for Sketchup here with a framework to support a tarpaulin during work on a 17 foot launch I acquired some years ago, but has been hanging around waiting for attention.

The job was to construct a strong framework, high enough to work under but easily demountable and easy to store for future lay ups.

Frames for such structures are a generally bit of an inconvenience. They are always the wrong shape, bulky and awkward, difficult to remove once up.

A couple of years ago I made some supports for a ridge using two struts bevelled to fit the ridge, and pivoting at the bottom edge. By holding the legs of the strut outward, a sort of pincer action clamped them to the ridge. It worked pretty well, and had the advantage of being easily removable (just release the legs and the pincer effect releases) and easy to store – as they fold up.

Thinking on those lines I designed a set of five supports holding a ridge. They would hinge on a cross brace and pinch the ridge. They would be held vertical by packing pieces screwed to the ridge, and braced downwards against the gunwales.

This would mean a ‘dog leg’ design, the struts running out at 30 degrees and then dropping vertically onto the gunwale. The problem of course was that the boat varies in width and also has a sheer, so the lengths of the struts and the dog legs would be different for each frame.

It could be made on the boat.  But it would be a lot more work fiddling around. Much better if possible to make it in the workshop.

There was no getting out of it, I had to pick off the heights and widths at each frame.

So the boy and I scavenged the garden for materials, and found four 10′ lengths of 5×2 in the wood pile. Two of these would be ripped in half for the struts, and two joined to make the ridge.

A rough but effective splayed scarph, through bolted,  creates a nice long ridge.  The timber thicknesses are uneven, but the joint was scribed to fit lengthways with a saw cut, and snugged up with bolts driven through slightly offset holes.  The undercut timber resists bending forces.

A rough but effective splayed scarph, through bolted, creates a nice long ridge. The timber thicknesses are uneven, but the joint was scribed to fit lengthways with a saw cut, and snugged up with bolts driven through slightly offset holes. The undercut timber resists bending forces.

First we cut the ridge joints. We use a splayed scarph. The undercut at the ends adds support to the joint. These were though bolted with slightly offset bore holes, to snug the whole thing together.

Having done this, we took it down to the launch in pieces, together with a straight, wide batten, a tape measure, a square and a notebook and pen.

To pick off the gunwale heights and widths, we set up the ridge on the boat, running from transom to stem, ensuring it was straight. Then we selected suitable stations and marked them on the ridge, together with transom and stem positions.

Then we set the batten across the width of the boat, locating it with a square on the ridge, and using the rib locations to position the batten square to the centreline. The end of the batten was aligned to the outside of the gunwale. Then we took the height from the batten to the ridge, and running the square on the batten picked off the inside and outside of the gunwales. We did this for each of the five stations, and then it was back to Sketchup.

The picked of points from the gunwale stem and transom mapped out

The picked of points from the gunwale stem and transom mapped out

Armed with this information, it was a simple matter to draw a 3D grid and mark off the offsets we had measured. The thickness of the batten was added to the stem and transom positions and the ridge set up a further 500mm. Then a standard frame was drawn, copied, and adapted to length and height at each station. A cutting list was prepared from the Sketchup measurements.

The frame, built in Sketchup on the measured points

The frame, built in Sketchup on the measured points

The aim was to make the whole thing off the boat, and take it down and assemble it. Theoretically the only work we would have to do on the boat was screw the packing pieces on the ridge that hold the frames vertical.

Details of clamp, ridge removed

Details of clamp, ridge removed

Details of clamp

Details of clamp

Details of brace

Details of brace

This was a job that really benefited from setting up machinery and doing ‘runs’. The ‘feet’ at the bottom of each leg were identical , as were the corner braces on the dog legs and the cross struts joining each leg together, and the packing pieces on the ridge.

An hexagonal arrangement of three braces speeded up cutting these.

An hexagonal arrangement of three braces speeded up cutting these.

The small pieces were cut from plywood on the table saw, and drilled with clamped fences to locate each piece easily. The corner braces took a bit more thinking, but eventually I cut them in threes. A rectangle 233mm x 200mm contained a hexagon of three braces. So I cut seven identical rectangles, drew out the hexagon and the three dividing lines to the centre, and stacked them with the marked template on the top. I cut the corners off on the chop saw set at 30 degrees, and then bandsawed the whole lot at once along the three lines.

The struts and legs were cut on the chop saw set at 30 degrees by measuring and cutting from the Sketchup cutting list, and then rotating 180 degrees for the next cut Similarly the ten cross braces were cut off to length and the bevels at 60 degrees on the chop saw, then repeat drilled using locating fences on the drill press.

A simple arrangement to hold the foot on the gunwale, connected with an M8 bolt and wing nut.

A simple arrangement to hold the foot on the gunwale, connected with an M8 bolt and wing nut.

Details of clamp.  The two legs pivot on the bolts.  Spread and held on the gunwales, they firmly grip the ridge, which seats itself on the cross braces.  The two packing pieces screwed to the ridge inhibit  racking.

Details of clamp. The two legs pivot on the bolts. Spread and held on the gunwales, they firmly grip the ridge, which seats itself on the cross braces. The two packing pieces screwed to the ridge inhibit racking.

Front view

Front view

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And as you can see from the pictures, it all fitted perfectly, literally to within a few millimetres. The frame is extremely strong. Each frame can be easily removed by swivelling the feet up from the gunwales, and pulling the legs inwards. This unclamps it from the ridge.

Compare this with the finshed view

Compare this with the finshed view

Compare this view of the completed frame with the Sketchup perspective.  It is one great advantage of 3D drawing that you can see exactly what it will look like.

Compare this view of the completed frame with the Sketchup perspective. It is one great advantage of 3D drawing that you can see exactly what it will look like.

With the tarp on, a snug and roomy space.  Maybe I'll get a stove and a sleeping bag...

With the tarp on, a snug and roomy space. Maybe I’ll get a stove and a sleeping bag…

What is quite nice is that despite it being extremely strong and locked together, removing it does not require undoing a single fastener.

Including the design, and visits to the boat to measure and build, the whole project  took about two days

I had intended part 2 of this to be about planes, but I’ve been overtaken by events.

The job that came up was cladding the side of the houseboat, 114 planks of tongue and groove fitting between a horizontal plank mid way up the wall, and a continually changing curved skirting at the bottom.  So variable lengths, variable angle at the bottom – oh, and just for fun, a 20 degree undercut on the bottom as well, so a compound bevel.

Hmm.

Various ideas floated through my head.  What was I going to use to make the compound cut?  A chop saw seemed the obvious solution, but I would still need to pick off the height and the bevel angle, transfer it to a heavy stationary tool that could not be used the side platform (so a 20 metre walk), set up the tool, cut, bring it back, fastening it – it would take days and days to do that 114 times.

Makita circular saw

Makita circular saw

What about the portable Makita circular saw?  This cordless tool is a must buy.  Buy one now, go on.  They are brilliant.  Portable, fast, handy.  And I could set a 20 degree angle on it.

But what about the bevel?  It would need to run on a fence that was set to the bevel.  I don’t have one of those.  And anyway, I would have to transfer a measured bevel angle to it, which allows inaccuracy and wastes time.  And even then, there was the height to pick off.

Then it occurred to me that I could make an adjustable fence that could itself pick off the bevel *and* pick of the depth.

But the problem there is that the saw does not cut at the fence.  There would have to be a spacer exactly the right width.  And the pick off distance was around 1.3 metres.  Did I want to be lugging something that long around?  Not really.  And how would the adjustable bevel square up against the plank?  If I put an edge on it, it wouldn’t sit easily on the surfaces being measured.

So what could my bevel run on?  Well, I could make up a long board with an upstand at the edge.  That would locate the edge of the board and the edge of the bevel.  And I could put an end stop for the plank, and another end stop for my adjustable depth gauge – in different locations – and use a large spacer when picking off the bevel.

Sounds complicated.  But actually it was a fairly simple jig, and it worked brilliantly.

Depth gauge - thick walled stainless tube drilled and tapped, brass rod, stainless rod with elbow, threaded.  I used BSF thread to minimise the risk of destroying the thread when tightening.

Depth gauge – thick walled stainless tube drilled and tapped, brass rod, stainless rod with elbow, threaded. I used BSF thread to minimise the risk of destroying the thread when tightening.

First I made the adjustable depth finder, using a piece of 10mm thick walled tubular stainless steel and a brass rod that fitted the tube, ground to a point at the end  I drilled the tube at one end and tapped it for 3/16th BSF thread, then cut a thread on a small diameter stainless rod to fit, bent it and chamfered the ends.  One depth gauge.  rather amazingly I had all the materials hanging around in my workshop, in a collection of tubes and rod I bought on ebay a couple of years ago.

Bevel fence with depth gauge

Bevel fence with depth gauge

Components of bevel fence

Components of bevel fence

M8 T nut recessed (rather roughly!)

M8 T nut recessed (rather roughly!)

The bevel fence was a back plate of 18mm ply, bored with a 9mm hole and fitted with an M8 ‘T’ nut.  I recessed the nut in the back of the plywood.  The fence itself was 6mm ply with an 18mm strip, drilled with an 8mm drill and fastened by an M8 bolt with a wing nut on it.  So the whole thing sat perfectly flat.

I drilled a 10mm hole in the end of the back plate and pushed in the depth gauge.

A bit of rough measurement suggested that a spacer of 600mm would work pretty well.  So that was cut out, ensuring that the top and bottom were parallel.  This would rest on the top of the skirting and effectively transfer the skirting angle up 600mm.

The chopping board was a 1.3 metre piece of shuttering play with an up stand and end stop.  The depth gauge stop was a piece of plywood, which I screwed to a location that seemed about right.

(photos taken after the job was done!) Spacer sits on the skirting where the new board will go, thus transferring the angle of the skirting up 600mm.  The cleat was to hold it against the face o fthe previous board

(Photos taken after the job was done!) Spacer sits on the skirting where the new board will go, thus transferring the angle of the skirting up 600mm. The cleat was to hold it against the face of the previous board

Bevel fence on top of spacer.  Unfortunately I did not take any photos untill we finished!  Obviously, in use, there would be no boards behind the jig, and it would be hard up against the previous board

Bevel fence on top of spacer. Unfortunately I did not take any photos until we finished! Obviously, in use, there would be no boards behind the jig, and it would be hard up against the edge of the previous board

Positioning the saw for the cut

Positioning the saw for the cut

The complete jig

The complete jig

To set it up, I placed the spacer on the skirting, positioned the fence on the spacer, and with the wing nut loose slid it along the spacer until the edge of the back plate was hard up against the previous plank.  Then I tightened the wing nut. This captured the skirting angle on the bevel fence.

Then I extended the depth gauge until it touched the underside of the horizonal plank.  I tightened the gauge screw.  Now I had captured the length of the plank.

I set a piece of Tongue and Groove stock on the chopping board, and the bevel gauge on top, with the depth gauge against the plywood stop.  Then with the saw at a 20 degree angle, I ran it along the fence and cut the stock.

Holding the stock up to the wall, we could see that it was slightly too short – about three sixteenths.  So we shifted the depth gauge end stop that distance towards the saw end.  The next cut was perfect.

So we kept the whole jig on the side deck with a pile of stock.  As each piece was fitted, the jig was set up again – about 10 seconds – and transferred to the chopping board.  No thinking required, just direct transfer.  Provided the plank was located on the chopping board against the end stop, and the bevel fence located against its stop, it worked perfectly.

A really good example of how thinking about how tools run on surfaces works to your advantage.  The spacer ran on the skirting, the bevel fence on the skirting and the previous plank, the depth gauge on the top plank; then the stock and bevel against the chopping board, and the saw against the fence.

This is, I think, the essence of toolmaking – no thinking required to use it. The tool captures the desired outcome in its design, and cannot help but produce the right result.

Brackets2Last year, with the benefit of our new Solar Power system, I built a platform off the side of our houseboat for maintenance.  The details are here:  Solar Powered Welding.

Briefly, I made up 13 large brackets from 2″ angle iron, which are bolted by two studs each to the hull.

At the time I thought that a trestle arrangement could be used to access the upper part, but on reflection it seemed more sensible, in view of the alarming drop into the mud, to build a easily movable but sturdy higher level so that a section say, two scaffold boards long, could be worked on at a time.

Two extremes of height and distance

Two extremes of height and distance

'Shoe' that fits over existing platform bracket

‘Shoe’ that fits over existing platform bracket

Details of suspension brackets

Details of suspension brackets

So it was back to Sketchup, wondering how best to do this.  Eventually I settled on a right angle bracket, standing on the existing brackets, and hanging from adjustable brackets fixed to studs along the central timber panel.  When not in use, the studs will take a stainless steel eye nut, through which a hefty hand rope will be run, and allow access down the narrow side deck when the whole maintenance platform is demounted.

I wanted all the new brackets to be the same and interchangeable, so I needed to allow for horizontal and vertical adjustment because the distance to the wall, and the elevation upon platform level, varies.  The solution was a sliding ‘shoe’ that fits snuggly over the lower bracket, and a threaded rod suspended from a bracket.

I made up a prototype, which seemed like it worked fine, so the boy Robin and I got together to fabricate the rest, he with grinding and prepping, I with cutting and welding – this time the rather faster, although messier, stick welding.

Robin on the prep work - homeschooling in action

Robin on the prep work – homeschooling in action

The studs to hang the brackets are bolted through the walls, with plates on the sinde and A2 half nuts and washers on the outside.  The hanging bracket (and the eye nut, when I gets fitted) fixes on top of the half nut.

The shoe is clamped to the existing bracket.  The result is an extremely sturdy structure

One issue that I had wondered about was racking of the outboard ends.  But I counted on the twist being resisted by the flat surface of the angle iron pressing against the scaffolding board.  This appears to work.  I’ve only put three boards up so far, but there is very little movement, and it feels very secure.

To remove a bracket just requires loosening the shoe clamp and unscrewing the suspension bracket nut.  Then the whole thing comes away and can be relocated.

Alas, not painted yet as we seem to be needing them pretty much now, but they’ll only be up for a few weeks while the soffits, fascia and painting is done, so then they will be wire brushed and painted.

The five movable brackets erected

The five movable brackets erected

Shoe

Shoe

Suspension brackets

Suspension brackets

Suspension bracket detail

Suspension bracket detail