Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[derekwarner]

So Bob says...... "I am having major problems with this Proxxon mini jig saw on 5mm ply"


By all accounts Bob, these Proxxon machines are capable of producing excellent cutting work.......why not call their help line & discuss your issues......

[PS..... I did mention some weeks back .....'the real issue is creating the curved template in the first place']

Derek

[Bob K]

Buhler Motors

The four big Buhler motors have arrived from Germany.  This lifts my spirits quite a bit.  They are HUGE compared to the little motor used in my armed trawler (with a Pound coin on top).   Only 1.9A each, 3700 rpm and massive torque.



Hatches

Derek:  I did get the marking out very accurate, especially the curves which I also check-measured every 75mm along the axis.  The outer profile I could fettle back to fit, but the mostly rectangular hatch openings I really needed to go a lot better as the fitted hatches were intended to be a good fit with only a max of a blade’s width gap.
Now it will need a lot of rework straightening the cut edges and gluing in strips of wood. 
At least I have managed to get the step between the two deck levels reasonable.  See below.



I am naturally reluctant to attempt to use this power tool on the 87mm barbette openings. Too tight a curve, after it’s difficulties following simple straight lines.  I would have expected a "jigsaw" to do this, it's not exactly marquetry.

[ballastanksian]

If, as presumed, the saw is of the best quality in make and material, then are all the blades that you have used from the same packet? If so I wonder if you were sold a batch that had their teeth set badly? If not then that is worrying as one would hope that the blades would be as well made as the saw they fit in.

It sounds like you would have got a better line by chain drilling closely and hand sawing the minimal ply between the holes 

Those motors are indeed behemoths Bob! I love the fact they have the polarity marked on the casing so you can get them wired up confident that all the soldering and fitting doesn't need re-doing because you weren't sure and wired them all wrong.

[joppyuk1]

Just a thought on your blade alignment problems. I haven't got this particular saw, and can't see the area in your photo, but my full size jig saw has a small guide behind the blade, which stops in wandering left or right. 

[derekwarner]

Bob....have you trialled the replaceable concentric foot plate that I had earlier mentioned?......

A model builder acquaintance has attained excellent results on complex curves which require no after sawing sanding using this concentric foot ....[the diameter or radius of transition is only limited by the diameter of the concentric foot] 

He is however using templates again as mentioned a few weeks back.....

This chap also has the Proxxon 240 volt planer/thicknesser.....this produces absolute quality planking with true thickness accuracy and timber surface finish

 Derek

[raflaunches]

Hi Bob


When I was cutting the decks out from 4mm ply for my Invincible I had some small wobbles but the biggest thing I had different to yourself is a 'Steve"! I held the deck down on a metal work bench and Steve cut down the pre-marked line. We were using my Dad's work jigsaw which is a Makita design and I've noticed that the Proxxon jigsaw is ergomentally designed differently which may lead to your wobble.


See below for the Makita jigsaw and you'll see the difference.


https://www.google.co.uk/search?client=safari&channel=ipad_bm&source=hp&q=makita+jigsaw&oq=Makita+jig&gs_l=psy-ab.1.0.0l4.2121.5662.0.7995.10.10.0.0.0.0.126.708.9j1.10.0....0...1.1.64.psy-ab..0.10.706...0i131k1.0nZPAAv0aUQ

[Bob K]

I greatly appreciate the depth of collective experience and knowledge of our Mayhem community, without which my mere six years of boat building could not have even reached where I am now.  However, I do suffer the impulse to reach well beyond my current level of experience at times.  Like my present ‘daft’ project for instance.  I do not have a big enough workshop, or the wide range of equipment needed for 2 meter plus boats.

Nick:  You and Steve make a great team.  Two is always better than one problem solving.  I did one cut at a time with the panel clamped down on the Workmate.  What would have been useful is instead of a rocker switch a simple pushbutton -  at least for stopping the cut as the blade can be hard to see.

Derek:  The power tool does indeed come with that alternative to the flat plate “shoe”.  They did say that was for working on concave or convex surfaces, rather than the flat ply I am using.  The reciprocating head, or maybe the set of the teeth, has a marked predilection for pulling strongly to the left, and I am using genuine Proxxon blades.
I will have a play with that on some scrap offcuts, always worth a try.

Thank you for your patience.

[C-3PO]

Hi Bob,

As one of the worst workers with wood on the planet (me)  I would not have approached this with a jigsaw.  I would have used the only tool I seem to have mastered 'ish when it comes to working with wood which would be a router. I would have clamped a straight edge to run the router along and stopped short of the corners where I would have used another cutting tool ( fret saw or similar) to finish the corners.

I would almost attempt to cut your 87mm openings free hand with a router!!!

Just my tuppence to chuck into the melting pot

Regards
C-3PO

[Bob K]

O.M.G.  Just watched a video demo of a router.  For model work it looks like a pneumatic drill for glass engraving.
The ship is big, but a full size one.

I should also mention I do have one of those full size Black & Decker "Jigsaws".  Used it once on floorboards, useless, put in back in the box where it has since stayed.

I do not think I would use power tools for this kind of task again.  Accuracy is made harder by the recess filling up with a mountain of sawdust faster than you can blow it away, making the actual position of the cut hard to see, having to visually rely on the notch in the plate.

I should have use a fine tennon saw to rough out, then a hand fret saw.  Would have taken longer, but a better job.
A pity my vibrosaw cannot handle this size of the work.  That is very controllable.

I will chain drill the 87mm cutouts.

[C-3PO]

Bob
There are routers and ROUTERS


Would this not help you cut your 87mm holes?? or am I missing something?


https://m.youtube.com/watch?v=JHPNOrMgr3E


C-3PO

[Bob K]

Nice kit, but £80 just for the special adaptor plate.  I don't really have room to wield something like this, and nowhere to store it after a single usage of seven holes.  But thank you for the kind suggestion.
I am much better with electronics and a soldering iron.

I am now coming to realise that with the hatch cuts looking naff and very visible I should clad the horizontal areas with half mil styrene, using the ply as a supporting structure.  I know I can get that very accurate as an overlay, and no saw blade gaps.
It's a solution I should have considered before.  All a learning process.

[Colin Bishop]

Why styrene and not 0.5mm birch ply. Lovely material to use and cuts very accurately. Will also glue better to the sub deck.

Colin

[gingyer]

I will chain drill the 87mm cutouts.

you get nice 86mm Diameter hole saws or hinge cutter would that not be of use?
and a small sand of the edges?

[dreadnought72]

+1 for the birch plywood idea. It's lovely material to use.


Andy

[Colin Bishop]

Also, sticking large sheets of styrene could result in problems due to thermal expansion, the plastic will want to move much more than the underlying wood. Using ply will avoid this and it will bond better to the existing wood.


Colin

[C-3PO]

Hi Bob,

Forget the expensive adaptor plate - make your own jig/adapter plate out of a sacrificial piece of ply and simply screw / bolt the router to it.

Likewise - cutting straight lines - fix the thin ply to another sacrificial scrap and you will get great results.

I think because I am so bad at using most wood working tools I have found that the router can achieve many things and is something I have come familiar with using and abusing.

You get some amazing "bundle" deals with cutter attachments/adapter plates etc on new routers - clearly the Makita's are Rolls Royce's but even own brand like Wickes etc can be big bang for the buck

As I am sure you are aware you get some very small foot print routers right up to pieces of kit that even with soft start want to take yours arms out of their sockets

Great build - which ever way you jump we are all watching with interest.

Regards
C-3PO

[Bob K]

I really appreciate you all taking the time to offer advice.  As I am very unlikely to build anything this huge again I am reluctant to keep splashing out big money on more equipment I may never use again.  I am disappointed in the Proxxon which cost a fair bit including the special power supply unit.  Ships half the size have always been constructible without needing such equipment before.

So, looking at damage limitation:  The outer profiles had the "wobbly extra" on the outside edges, so I could trim them back to fit.  All the hatches have cut inside my lines as I went anti-clockwise. Two may be usable with a bit of fettling.  The third, and by far the worst, has it's really duff 5mm-out wobbly lines mostly under the aft superstructure.  I can hide that with care. The forward parts of it are not too bad, and I think I can fiddle that.

The Proxxon mini jigsaw looked ideal, not much larger than a Dremel.  I was not expecting it to pull to the left as it cut.  We live and learn.

I have now got the casement insets constructed, using 1mm styrene, which is some positive progress.

Seven barbette holes to cut . . . . .

[ballastanksian]

I did the deck on the destroyer in styrene over ply because it created an effect I wanted to try and I reckon it worked. But for a vessel with wooden decks over an immense area, and I assume you are going to use individual planks, I would go for a thin ply layer to tidy up the irregularities which will be a good basis to plank onto?

Laying large areas of styrene onto wood requires adhesives that will not damage the styrene such as epoxy or cyano. and it will require time to position the styrene in place correctly, something cyano will not give you, and I was not fully pleased with how the epoxy worked on my deck, especialy as a customer rang while I was laying the epoxy and he was gracious enough to hang on while I spread it on and did not have time to tape the edges down as well as I liked (Hooray for strategic aplications of cyano around the edges!)

Alternatively, plank directly onto the deck, first defining the shape and edges of the openings and epoxy well to give the strips on the edges strength.

[Bob K]

I would certainly agree that thin styrene over wood works, having successfully laid it before, but with the size of this is it is more like applying Formica sheet to a kitchen worktop - a would become problematical at this size.
I am trying to see what I can do with what I've got.  The worst areas are under superstructure or can be fettled out with wood strip.  I need reasonably straight lines to plank against.

Barbette holes.

I did manage cut these big holes, keeping the direction anti-clockwise and aiming well inside the scribed circles.  A lot of filing afterwards, but all the cuts remained inside the markings. 

Toggle Latch

An 18 mm ply support will run between the two bulkheads, with 9 mm stiffeners at right angles underneath.  This base needs to be strong.  I am planning 25 mm high styrene side faces to limit water ingress, although the latch bar enters well above the waterline.  Can't make this coffer dam too high as it is right under a turret. 
Even so the big toggle latch, fully opened flat, is 20 mm longer than the space between bulkheads.
Lifting the three turret hatch will be necessary, both for accessing the latch, and the turret innards.

[Bob K]

Toggle Latch Box,

I managed to simplify this since my earlier idea.  18 mm platform & 9 mm supports.  This is to mount the big toggle latch that engages with the notched bar in the after end.  The supports acts as bracing, giving an “H” section fixed between bulkheads and the bottom of the hull.  M5 blind nuts on order as once epoxied in the underside will not be accessible.  The side supports also act as a coffer dam in case of water ingress. although 30 mm above W/L.



Deck Fitting

The seven barbette holes did not come out too bad in the end, keeping the jigsaw well inside the marked circle, then finishing off with half round files. The casement insets came out reasonable, although some very fiddly expoxying awkward faces and angles.  Lots of tape and clamps.



I will not trim off the rear edge of the deck until after it’s final fitting.  I want the inter-hull join as seamless as possible.  The fibreglass hulls fit together nicely with the interconnecting stainless tubes slid into place.

A lot to do before the decks get stuck down, besides fitting the motors, shafts, secondary armament, and batteries etc.  Underdeck support flanges and magnetic hatch fasteners.  No rush, but progress is being made.

[dreadnought72]

Lovely job! 


Andy

[ballastanksian]

You are flying along now Bob, I mean really flying! With the toggle latch almost in place, the tubes all aligned as intended and the big holes in the deck cut and finished, she is starting to look like a Dreadnought.

Are you still planning to have flexible barrels for your secondary armament?

[Bob K]

You are flying along now Bob, I mean really flying!
Are you still planning to have flexible barrels for your secondary armament?

Thank you.  Yes.  I plan to learn how to do rubber moulding along this path.  Twenty 6 inch guns, mostly arranged for maximum vulnerability in a model - sticking out over the sides.  I am less likely to get them broken off as rubber castings, and easier to replace.  Most dreadnaughts and pre-dreadnaughts have hull-overhanging armament so I am surprised "bendy" versions are not available.

Rear Hull

Meanwhile, work continues on the after end of the ship,  Remaining four barbette holes in place.  The upper deck is here being fettled to fit.  Note the darker hardwood strakes set into the upper deck hatch.  This is where the cutter did its worst drunken meandering.  Basically I cut out the worst of the wobble edges and glued in hardwood fillets.  All hatches now have mounting flanges underneath, some of which will be fitted with pairs of Neodymium magnets.
7 dia x 5 thick.  Pairs will be one each embedded in the hatch and in the mounting lug underneath.





Picture also shows the 1/2 inch square brass latching bar for the toggle clamp in the forward end.

It is really handy when working on very large models to have only one half on the workbench at a time.   

[derekwarner]

Bob......I understand the ... 'the 1/2" [12.5 mm] square brass latching bar for the toggle clamp' as shown for securing the two halves together......does this require any over centre moment  [with an extension arm] to secure it...[just like load chains on trucks] ....or is thumb & forefinger OK?

From this we understand the toggle is always in tension when secured......but obviously the weakest part of the device is the surface area of the undercut yoke of the toggle which appears to be about 3.5mm high x the 12.5 width [= ~~44 square mm?]

So what is the rated restraining or holding force of the toggle?

Derek

[Bob K]

Interesting question Derek.  I am trying to find the invoice for it, but I recollect it was rated at 190kg.  In fact the one I am fitting is rather overkill, but I like to make sure.  It is basically an over centre lever, in that when the lever is latched down the clearance between the two "hooks" is zero.  My brass bar replaces the pressed steel catch plate it comes with, and I think is stronger.

Types of latches:  https://www.youtube.com/watch?v=nUY9kJTVBOw

The hull halves slide together on telescopic tubes.  The latch holds the mating surfaces together.
It is the telescopic tubes that are supporting the load, the latch stops the hull halves floating apart.
In fact you could still lift the boat with the latch undone.  The 3 sliding tubes are nearly a meter long.

Such latch mechanisms are used in applications from suitcases to truck rear doors.
The amount of tension / clearance is adjustable.  ie:  Just enough so it is tight.