Here is a Shapeoko 2 - my eShapeoko is a similar machine - cutting steel. You will see that you need a decent spindle motor, which is not surprising. But the framework is adequately rigid.

I have over-specced what I have to allow for expanding for future use. I would not be surprised to find that a machine which was limited to cutting balsa, plastics, obeche and light ply (which would cover the vast majority of marine modelling) could be sold for less than £100. Unfortunately, there are too few customers to make it worth designing such an item.

Wow - was I wrong . In the pictures it looked flimsy. The ones Ive seen here use smallish routers (bigger than a Dremel) running at very high RPM (25 To 30k) and the cross bars are heavy I beams. They make the moving bar on the laser look like a kids toy. Not one I've seen here is recommended for anything less than a 3mm cutter head

"....but would have to be a bit more powerful/stronger build even for Jelutong....."

You can cut steel with a Shapeoko (slowly!) so long as you have the right spindle and cutter. It's designed for a DeWalt or a Makita - I would use a Dremel clone when cutting something like ply - and a stronger tool. But then it would be much noisier. Using a model boat motor is unusual, but I have shown that it works with balsa...

Could think of a lot of uses for your CNC router too - but would have to be a bit more powerful/stronger build even for Jelutong and the like. Trouble is nothing like that available here - cheapest we've seen was about R25k.........
The larger ones running to millions.

You are right of course - in the UK you would also have to have a safe extractor/collector unit for the fumes/dust - however the US made table top models are self contained - BUT you only have a A3 sized bed whereas ours has an A1 and can take objects up to a foot high for engraving, plus a rotary attachment for glasses , bottles etc. The water cooler is a separate unit which now costs the better part of R10k. Better half had her aluminum tubed Universal 200 re-gassed (they run on CO2 at about 38kv - at 80w so minimal current) and that set her back about R80k some 22 years ago. Pyrex type glass tubes are only about R12k now however.
You also keep the lid tightly closed unless you are an idiot - plus they all have a safety switch to shut the laser off if the lid is lifted (which I have seen bypassed). There is always some stray laser beam about and deflection off the bed which does not do one much good. Especially eyesight. So the machine has a thick dark yellow/orange perspex inset on the lid and you should wear safety type glasses the same coloration which act a bit like polarised lens.
As a matter of interest ours ran for a year in the spare bedroom - with the extractor unit venting through a french door panel - would be severely frowned upon by 'elf & saveless'.

Other disadvantages include the requirement to add expensive safety precautions to the work area - and I believe that some of these things need cooling water?

I am happy with a self-built eShapeoko that just hums quietly behind me in the spare bedroom - I'm not so sure I would be happy with 100W of incandescent power hanging from a half-stripped bolt, some gaffer tape and a couple of paperclips in the same place... 🤑⚡

The advantage a laser has of course is that there is no stress on the head - disadvantage is you cant tilt the head other than in very very expensive models and of course you cant use it as a carving tool for relief work. Its also inherently expensive because of the laser tube - anything under 60w is a toy. There are some desk top versions from the US which could be used for components - but length is a problem with those.

"...I'd rather cough up a bit more and know that I could do something with it!.."

Quite right!

When buying, people need to understand the important features of a product, and with new technology it is easy for the advertisers to conceal these.

For a CNC cutter, stiffness is very important, particularly if you are going to cut metal. The machine must not deform appreciably when it puts a strong force on the workpiece.

It also needs adequately powerful stepper motors to put that force on. and, of course, it needs to move the cutting head to all parts of the workpiece. I was interested to see that the spec states 'max travel distance' - I would have expected it to say 'max cutting dimensions', and wonder if these are less than the figures quoted.

At least we can specify a cutting area ambiguously, so that modellers can understand what they are getting. I would guess that 1ftx1ft cutting area would be fine for most aeromodellers, while 1ftx1yd is more what boat modellers want. But it is easy for an individual to chose.

Motor power requirement is harder to define - it depends so much on the leverage designed into the mechanics. Screws have more advantage than belts, for instance. And if you are only count to cut softwoods you can get away with much less power than cutting steel! Usually I would like to see the steppers having between 5000 and 10,000 gf·cm of torque - though that is a 'piece of string'.

Rigidity is even harder to estimate. You can get some feel when the seller says that this machine will not cut metals, or 'is an engraving machine'. The other indicator is weight - rigid machines are going to be much more massive. If the frame is light it will bend under stress. Though if you are using a laser...

My son has a couple of 3D printers and has made me several slot car chassis, guides and even gears, a motor pod for an RC glider, a camera pod for a flying wing model and a dummy Ford Model A engine and radiator for a Peitenpol high wing model aircraft. Painted and attached that today. Motor pod is on the glider, waiting to go.
I just wish I could design in CAD for him. We have to go with free files off Thingiverse.


Martin

My thoughts exactly DG.
I'd rather cough up a bit more and know that I could do something with it!
(Still got a few bob left in my savings fund😊)
Think I'd better get the hang of my 3D printer before lashing out on another machine though!
😎

There doesn't seem to be any complaint about the machine fundamentals in those reviews - their problems are with understanding how to use it, and the quality control and packing. In fact, one said that the quality of the parts was 'very good'.

Nothing was said about some of the most important aspects of the machine, which I have extracted below:

Max travel distances:
X: 160mm
Y: 100mm
Z: 45mm
Repeat positioning accuracy: 0.1~0.05mm (no load)
Max material depth: 30mm

Something that can only do 4" max dimension parts is very limiting! That positioning accuracy would be ok for load, but they spec 'unloaded'? I know that will depend on the material and cutter, but I would like a better understanding of the stiffness than that...

You can get machines with cutting beds of 12" for between £100-200 on ebay - but I think boat modellers would be better off getting a 36"x12" Eshapeoko or similar. Base cost of that would be £300, plus £100 for motors and controller...

Haha, a real example of "you git what you pay for", then, eh?
I thought as much.

Martin

HobbyKing CNC mill-
Hmm!
Seems a bit "cheap and cheerful"!
Only two reviews, which aren't very encouraging🤔

"Great price nearly impossible to use
mill

Packaged great, arrived fine and nearly fully assembled. Documentation and software is horrible. I spent two full days trying to see if I could trick into working. The supplied software won't move the Z or moves Z but won't turn the tool. I needed to get back to work so it sits in a box waiting for another couple days to find some other way to make it useful. When I have a real need for it, I'll spend the time but for now, not worth it to me.

Falls short - just a touch
Dave

The machine arrived exactly as shown, but had to be completely disassembled and reassembled as every nut and bolt was loose. Neither the table nor the motor assembly were straight. It took about 2 hours to make sure everything was zero-zero. One of the two plastic angle supports was broken. Instead of making another (all plastic parts are 3D printed) I opted to use aluminum angle. The overall quality of the parts is very good. See Community Discussions about the failure of the software."

https://hobbyking.com/de_de/t8-diy-3-axis-cnc-milling-machine-w-arduino-and-grbl.html
Cheers, Doug 😎

Yep, that's what I thought. OK for formers or bulkheads on airyplanes, but useless for a boat without a considerable extension. Anyway we should be encouraging people to make stuff conventionally and just use machines to save time perhaps when they get to be our age! But come the glorious powercuts, brothers and sisters, they'll all be f***ed and we'll all be knifing away happy as Larry.

Martin

A brushed 775 motor? Standard 'Johnson Can'. Cheap and powerful, for power drills - a bit more powerful than I am using. For cutting curvy balsa shapes, as aeromodellers do, it would be ideal.

Most modellers cut shapes that are long and thin. The only problem for marine modellers is that we typically require shapes that are about 36"/1m long, while aeromodellers rarely look for aerofoils which are longer than 1'/30mm. And the longer the base of a cutting machine, the more it will cost...

Apparently the machine uses a brushed 775 motor.

Martin

".... I have also been looking on utube at DIY CNC Machines using old DVD Drives and an Arduino board...."

You can probably make a machine for nothing out of scrap if you know what you're doing - but I wouldn't advise a beginner to learn that way!

The issue is getting the precision of movement together with enough stiffness to be able to apply adequate force when cutting and not have the structure bend.

For modelling, we have an advantage in that many of our materials are thin and easy to cut, compared to typical professional requirements. A common cutting tool is a Dremel - which we often have, and you can see that a model boat motor can easily cut balsa - and probably light ply...

HobbyKing are doing a CNC mill for a ridiculous 85 quid! (or thereabouts). And you can replace the head with a laser cutter if you wish. Beyond that, I know nothing of such alchemy.

Martin

Hi DG,
I have seen your thread on your CNC Machine and I have also been looking on utube at DIY CNC Machines using old DVD Drives and an Arduino board.
I will have to do a lot more research in to it as it is a good way to cut bits out for model making.

Martin555.

DG could I suggest we start a new thread for those Points you made - each ones a topic on its own

"....I am looking forward to the next stage....."

There will now be a short intermission while I sort out other things, and I suspect that a build will start sometime in September. Or later!

In the meantime, this thread has introduced a number of issues apart from describing the egg-box structure that Ernie Webster used in the KK EeZeBilt series. It suggests that if CAD packages are used for model boat design then the plans created can readily be shared with other modellers over the Web, and shows that personal CNC machines costing a few hundred pounds are a useful supporting workshop tool for this process.

Any comments on the above points would be read with interest!

Hi DG,
Thank you I have a much better understanding of the process and I am looking forward to the next stage.

Martin555.

All the hard work would have now been done, if I had got the waterjets and had finished designing the stern. We will have to wait for that, as well as a delivery of balsa... But I have a couple of spare sheets of balsa and a few final parts, so I can give you a short sample of how things will go on from here while the machine is cutting them.

We want to cut parts out of a 4"x36" balsa sheet so I draw up the boundaries, and fit the parts in at appropriate places (fig36). The sheet is oriented vertically, because that's how my CNC machine wants to see it, and the top right corner is positioned at 0:0, so I know where my origin is.

Then I remove all the lines that I don't need to cut. Because I have lined up the long straight edges with the edge of the balsa, I don't need to cut along them. I don't need to cut the boundary lines either - so I have a rather odd drawing for final cutting as at fig37.

From now on we don't need to look at any more drawings. I save just the bits I want to cut as a .DXF file - which is a standard CAD drawing format. Then I take this file and input it to a free software package called 'DXF2Gcode'. Which, you will not be surprised to hear, outputs instructions for cutting those lines in G Code, which is a standard language for controlling cutting tools. The language looks like this - my comments in brackets:


G90 (Absolute programming)
G21 (units in millimeters)
G17 (We are working in the XY plane)
G40 (Cancel automatic tool radius compensation.)
G49 (Cancel tool length compensation.)
G28 (go to the pre-programmed Zero position directly over the balsa sheet)
G92 x0y0z0 (Set this position to Origin Zero. All distances will now be measured from here)
G0 Z -10.000 (drop the cutting tool to height -10mm - just above the balsa)

(** LAYER: Layer1 **)

( SHAPE Nr: 2 )
G0 X +0.000 Y -68.551 (go to the first place to start cutting)
F60 (set the feed rate to 60)
G1 Z -15.400 (drop the cutting tool through the z axis to height -15.4 - this cuts almost completely through the balsa, leaving just a thin web underneath to hold the part in place)
G1 X -25.258 Y -68.525 (Move the cutting tool along the x,y axis to cut the first line)
G1 X -25.255 Y -65.350 (Move the cutting tool along the x,y axis to cut the second line line)
G1 X +0.000 Y -65.350 (Move the cutting tool along the x,y axis to cut the third line)
G1 Z -10.000 (raise the cutting tool along the z axis out of the balsa)

You can easily learn the basic commands - but you don't need to as DXF2Gcode just creates a working cutting file for you.

Next, you put some balsa in the machine, turn it on and send the G Code commands to it. This is done with another free software package called 'G Code Sender'. The names are quite descriptive! I enclose some photos of what happens next, and a 'media file' (video) which, as you know, you download by clicking on it, and then clicking on the miniature little blue square on the top left of the screen. As you can see, there is very little dust with a thin cutting tool, and the sound from a 12v motor running at 10v is low. This was recorded with a camera within a foot of the cutting tool...

After that, it's just an evening of taking the parts out of the balsa sheets, assembling them and gluing up...

Hi Red,
"Am I being paranoid or is there an easy way to seal removable decks ? "

The only suggestion that I can come up with is :-
If you shave a bit of material off of the hatch all the way around then glue an elastic band around the edge so that it is a snug fit in the hatch opening.
It will be tricky to do but this will prevent a lot of work now that the boat is finished.

Martin555.

"Perhaps DG is the best one to answer this -"

Dunno why - my boats will sink like anyone else's if they fill up with water.

Partly it's horses for courses - don't sail a boat with a low freeboard on the choppy side of the lake where the waves break over the bow. Fast boats which deflect water away might get away with it - slower displacement hulls where the water creeps up the side won't. Google 'Coandă effect' for a more technical description of the reason water sticks to surfaces. Tugs usually have heavy ballast and are more likely to have waves breaking over them than to ride up and over them. And sealing a deck effectively is going to depend very much on the way it's designed to fit on the hull...

Adams of Adamcraft fame in the 1950s used to stretch clear plastic 'clingfilm' over the decks of his open boats (it was invented in '49!) to keep the water out, and you might find that trick useful if you have to have a removable deck. The clingfilm would go underneath the deck, of course...

Sinking is less of a problem with EeZeBilts (though the Beaver with its heavy ballast would go down). They are made of many watertight compartments. If your boat doesn't have such flotation support, try using expanded foam in all the spare cavities. I do this in my boats, partly as a safety measure, partly to deaden the motor sound and stop the decks from 'drumming' and partly because I mount batteries and radio equipment in it. Here is a shot of a PT Boat with removable centre deck, which is happy in heavy waves - you can see the foam blocks...

Perhaps DG is the best one to answer this -
Having had one boat which took months to build disappear for ever due to flooding through a removable deck now have a distinct aversion for those. Since that occurrence have always tried to use a coaming type approach for any removable item - touch wood no losses since then.
Problem occurred when kitting a "Sunny" tug for my grandson (MB magazine A3plan) have had to extensively redesign due to that having a removable deck. Tugs are notorious for being wet boats since they have very little freeboard at the stern and it seemed that it would limit the boat to calm conditions only.
Am I being paranoid or is there an easy way to seal removable decks ?

Rotten luck Red 😭

Well at least you still have your memories at the moment LOL!

Martin555.

Hi Martin - Join the club - if you look at the parts for my original model products kit - they are named & numbered by the same method.........Wish I still had one. Unfortunately when away as a student in UK parents moved to a much smaller house and sister disposed of almost all of my treasured possessions.....Including a Hobbies Tug kit with mighty midget motor etc , a Basset Lowke ally hulled cabin cruiser powered by a Taycol Star and for a final insult boxed Dinkys given to her kids to play with in the sandpit!

Oi ad wun o dem 2 😁
Why was it almost impossible to get all the letters on the same level?🤔

This was my first printer LOL!

Martin555.

My first printer was an ICL line printer, in 1979 http://www.chilton-computing.org.uk/gallery/ral/orig/r18088l.jpg

Rather like this one, but orange, since I was working on an ICL 2900 system https://en.wikipedia.org/wiki/ICL_2900_Series

When I started with this stuff I had to use an A3 plotter for decent sized hardcopy.
Seemed to take all day - just to find there was a goof somewhere 😝😠
B/W copies on the dot matrix - what a racket 🙉
Boy was I glad when the Laser colour printers and driver adaptors arrived 😊😀

"...You can create the element, or Icon (also known as "Shapes" in some programs), by grouping the vector objects...."

Luxuuury! Now we used to have to draw the vector on the CRT with a graphics pen, move it with a tracker ball to an analysis section, change it into an EBCDIC file and print out the resultant data on a dot matrix. Then our project manager would beat us to death with a daisy-wheel before we went home...

And you tell this to the modellers of today and they won't believe you...!

You can create the element, or Icon (also known as "Shapes" in some programs), by grouping the vector objects. It can then be easily moved around in one lump 😉
When I have the object I group it, write the Part name/version into a box then group that with the object. If you have the Element, Icon Shape (whatever!) sidebar open you can copy your new "thing" straight into it for future use / reference.
The program then stores the shapes associated with that particular drawing or drawings where they are used. Separate shapes files are created which enables their use in new drawings. Sets of particular types of shapes can thus be created. You'll be amazed how soon you have a comprehensive library 😊
Of course you can use all the normal aspect, scaling, modification functions as usual when you add a basic shape to a new drawing. Update the label and away you go again!

In the 80s they built software to last! Cue 4 Yorkshiremen sketch...

In 1988 they did not have much concept of elements - only vectors...unfortunately the current version of my package (which I am sure will do everything) would set me back around £1,500 for the cheapest item...

The only way I could handle this would be to manually type text comments at all places. Which would involve writing a book...

I think the original version dates from the early 90's.
I first used it in the mid 90's while working on the Niteroi Frigates (Vosper Mark 10) in the Naval Arsenal in Rio.
Jolly times 😉

Surely it must be possible to add a text box to each element in your package?

"...Each element can also be labelled with this reference..."

Ah - you are using a CAD package developed in this century. Mine has the copyright date '1988-1995'.... I am a vintage enthusiast...😀

"I got multiple different drawings with no clear idea of which one had the latest version of which feature..."
That's the reason for the for incrementing number / date stamp.
Each element can also be labelled with this reference.
Then you can mix and match to try several variations until you get one you like the look of.
If it looks right ....!

That sorts the version issue brilliantly. You only have one result.

The advantage of doing things with CAD is that they are infinitely replicable and amendable, and can be converted into physical entities with no work. But version control with things which can easily be reproduced with slight differences is something that is rarely appreciated until you are drowning in the swamp...

This is all above me I just use paper and pencil.
If it doesn't work out then rub it out and redraw LOL!

Martin555.

"....or multi-page drawings with an incremented dwg / variation number...."

I tried that. I got multiple different drawings with no clear idea of which one had the latest version of which feature...😭

Actually, what I do is not too bad. I work across the screen, left to right, adding stages developing the plan. At each stage I am working on several varying features - these get developed down the page. So you can look at a page and say "I'll have one of those bows with that stern.." - but if you don't keep to this positioning things become difficult and you end up going to a new version...


"...I thought you meant at the stage of assembling to prove the drawings ..."

The advantage of doing it on CAD is that there is little need to prove the drawings - if it fits on the screen it will fit in real life. Ideally, I should learn 3-D cad and then I can virtually assemble and look at clearances without any need to cut materials at all...

I put variations into separate layers or multi-page drawings with an incremented dwg / variation number. Reduces the change control staff costs! 😁
Most drawing programs have an icon or element function where you can store variations and pull them out into a drawing to play "what if?"
AKA "suck it and see"!
Cheers, Doug 😎

Sorry I misunderstood i thought you ment at the stage of assembling to prove the drawings

Martin555.

Ah - the great advantage you have there is that you are dealing with physical items. There is only one final output.

I am working on a screen where there are going to be multiple versions of many items - all fairly indistinguishable without careful measurement.

In a proper software development environment there are rigid procedures for making changes, specialist packages for storing and controlling them, and a whole department of staff for change control.

My rule is that I usually work from top left to bottom right....

Hi DG,

"It's at this stage that I usually confuse myself completely, since I will make numerous slight alterations to put bulkheads and formers in better positions for several reasons - internal layout, better strength and balance.... and I end up with several dozen slightly different hull designs, each of which are slightly incompatible with numerous slightly different bulkheads, and I then lose track of which parts go with which others..."

What I do is tape a few bulkheads in place then cut some paper or card strips then tape them to the bulkheads to see if everything lines up as expected.
Then repeat this at all stages.
You will then see if something is wrong, then that bit could be put right, then on to the next.

Martin555.

Now we are on the home straight! We have a drawing, a reasonable structure, and we can start pulling out the detail.

It's at this stage that I usually confuse myself completely, since I will make numerous slight alterations to put bulkheads and formers in better positions for several reasons - internal layout, better strength and balance.... and I end up with several dozen slightly different hull designs, each of which are slightly incompatible with numerous slightly different bulkheads, and I then lose track of which parts go with which others...

However, here are some examples of the output from this stage. The superstructure base(fig32) is going to have to be made from parts as I mentioned earlier. The bulkheads (fig33) can now all be drawn with their slots and tabs, ready for assembling into the classic egg-box on the sub-deck (fig34). The front formers and the keel are taken off the drawing, again with tabs drawn (fig35)...

There will be quite a number of other parts to be drawn and made - the transom and other flat sections of the stern, the triangular bulkheads under the subdeck, the trapezoid plates which go to make up the funnel and mast, and other details like the anchor well. Almost all of these parts will be uninteresting rectangles with dimensions taken off the drawing, so I am not going to list them all down here.

The full set of parts, however, will be needed when it comes to the cutting stage, because we will be trying to get as little wastage as possible from the balsa, and sneaking little triangular formers into all available gaps on the sheets. I will take a bit of a break now, because I need to get the water-jets delivered before doing the final stern design - and I am running short of balsa, so I will need more of that!

I may cut a few parts on a sheet of 1/8" inch as an illustration. To do this you simply arrange the parts you want into a 4"x36" rectangle, load the cutter with a 4"x35" balsa sheet and send a file describing the parts to the cutter over a USB link. We will cover the software used and the stages of converting the drawing file to cutting instructions at that point...

Hi DG,
The drawings are coming along nicely.
I used most of the aft deck and superstructure so that I could get at everything and had a little lip that hooked under the aft end and magnetic strip tape at the forward end.
I kept the centre part of the deck for strength.

Martin555.

A little aside now, for the superstructure.

We can now draw a bit more detail on the superstructure, and shift it onto the hull to check how large an access cavity we have. If it looks too small we can always use part of the deck, but this looks as if it should be big enough. See fig27. I still don't know how I will hold it on - magnets perhaps, with a locating dowel?

Then we start measuring in just the same way as we did the bulkheads - base and height. This will give us the angles at which the superstructure walls are placed - most boats have these vertically upwards! Fig28 shows the cross-sections of the superstructure at 4 places, where the joints are.

Now we have a base shape and a top shape - we can draw these in as fig29. The vertical lines mark where the walls change their angle - these have to be in line top and bottom. How easy to check with a CAD package!

Imagine the superstructure base and top - held apart by those cross-sections. measuring on the diagonal line gives us the shape and size of the sheets which will be needed to cover it. Here they are drawn as fig30.

Finally, we have the roof with the bridge wings, and the upper roof of the bridge proper. They are drawn out as fig31, and immediately you can see that they are too big to be made from a 4" wide sheet of balsa. We may need to add parts on - or make them from plasticard? The base is also too big for a single sheet - that will need building in parts...

I still need to think about the actual construction, but now I have the shapes I can work out how they will be assembled and attached to the hull...

I am really looking forward to this especially the drawings to the CNC.
I have never done this side of the model making before.

Martin555.