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Author Topic: Racundra  (Read 44160 times)

dreadnought72

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Re: Racundra
« Reply #50 on: June 05, 2011, 08:07:28 PM »

"More soon", huh?  :embarrassed:

Well, it's June - as I'm sure you're all aware - and the work since then has been "occasional". I'm too busy trying to earn a crust at the moment, and can't forge ahead on the boat with alacrity and aplomb.

However, last night I faced up to my impasse on the build and took the following action:

I drew up A List Of Jobs Needing Done.

I ordered this list into What Needs To Be Done First. Always a good way to organize yourself out of a bind. This took time, not least because it's a long list, and much thought was spent on moving jobs up or down the pecking order in order to ensure things like "strengthening pieces for the shrouds" would be attached to the hull sides before such minor tasks as "planking the entire deck" commenced.  :-))

Armed with this finalised list, today saw the boat brought back out of the cupboard, ready for such things as these strengtheners, bracing for the samson post and fore hatch, and mast-shaping (got two lovely bits of wood ideal for the masts). I measured, checked, and measured again. All was good. As usual, I suprised myself that measurements and planning made months ago were shaping up fine. I headed down to the storage shed to set up the workmate and all the necessary tools, and then ... it started to rain.  <:(

There are some who are apparently complaining of droughts in south England at the moment, but our "summer" up here in the Scottish Central Belt has, so far, lasted precisely two days, nearly reached 22C (but didn't quite) and now the BBC weather is saying "rain for the next four days".

 >>:-(

Grr.

A new list. I need to pick one of the three:

1/ I should move.
2/ I need to get a decent, covered, working area.
3/ Take up a pastime less messy & therefore not so reliant on working outdoors.

Bum.

Andy
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dreadnought72

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Re: Racundra
« Reply #51 on: June 22, 2011, 02:41:51 PM »

Following a couple of posts to the electrical corner of MBM - you know, that section with bits of wire stuck in the carpet, and a faint smell of solder in the air - I'm pleased to announce that Racundra's main power wiring has been completed!

And it even looks relatively neat!!!  %%

Here's the diagram:



The green highlighted bits are all available under the forward circular hatch, enabling me to switch on/off and/or charge without removing the cabin roof. The LED bits of circuitry aren't completed yet, but me and, more importantly, the LED wizard think those values are about right.

Flushed with success following my soldering and cable-running, I just had to try the power/radio side of things. Unfortunately the only spare spade fuses are in the car. As in "literally required in the car", and - since it was raining once again - I did the next best thing. I checked all the wiring with the trusty multimeter.

...I stuck wires across the fuse terminals*... :o

...connected the battery.  ;)

And then switched on the main power and the ESC.  O0

All works.  :-))

I then spent (a particularly 'flu ravaged) twenty minutes wondering if I was being stupid by plugging the BEC cable into the "battery/option 7" slot of the RX (the word "battery" kind of made sense at the time) and only finding the motor control on some pot far removed from my fingers on the radio. But of course it can plug into any socket - the ground/positive pins are common across the sockets, and only the signal pin outputs vary. D'oh!

The other issue that I need to investigate is with regards to the sail winch. It feels immensely underpowered and very slow: yet the BEC claims to deliver 1.2A and the Hitech BB 725 should only draw 0.23A when running, more when under load. Do I have a potential problem here?

Onwards - a cam has been cut for the servo which'll operate the lighting microswitch, and my next stage is to get the final servo mountings in place. At which point I'll have some photos of the layout.

Andy, basking in electrical goodness.

*Don't try this at home, kids. Remember: I am old and stupid. You are possibly not!
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andrewh

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Re: Racundra
« Reply #52 on: June 22, 2011, 09:25:43 PM »

Ahoy. Andy the Basker

Sounds pretty successful, the whole setup (notwithstanding the 'flu)

I think you are running the winch*  through the receiver.  The tracks and wires are not capable of passing the oooomph the winch needs to accelerate and Hitec literature, at least recommends driving it straight off the battery with only the signal lead from the Rx.  I have the Hitec leaflet somewhere, but I think you know your electricery

AAAArgh - and you are running the winch off the BEC!  You must not believe the numbers - they lie!  Also you are only feeding it a bit under 4.8V  - and anaemic diet for winches, they prefer 6V

I have not researched the servo, but it it draws 1.25A running then the instant inrush when it is stationary is about 8 times this.  The volt drop will cause the Rx to lose count of its fingers, amongst other things.  You need to run the winch off its own 6V - suggest a home-made 6V BEC on a bit of veroboard with good wiring

Hope this helps
andrew
Gathering himself for a footy square-rigger


*Definition of "wench"    Something to turn the head of a dolt
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dreadnought72

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Re: Racundra
« Reply #53 on: June 23, 2011, 02:03:12 PM »

Hi Andrew!

To bring my currently anaemic winch up to a more sanguine state the options would appear to be:

1/ Stick in an additional 6V battery for winch work. This is a bad plan, since the point of the 12V, 7AH battery was to run the winch and everything else furreva. (Or at least allow for many hours' sailing/pottering time).

2/ Run two of the same ESCs in series, dropping both inputs to 6V, in order for one to run the motor and the other to run the winch from the power output leads. But this is also a bad plan, since I'd lose some umph when in propellor mode, and I'd need to take the winch signal wire from the radio to the winch ESC signal input, and, ummm, dismantle the winch and chuck in a couple of microswitches to limit the throw - running the winch as simply a 6V geared motor? No, that can't be right.

3/ Source a 12V to 6V voltage regulator, capable of "several amps" and wire this in parallel with the current ESC across the 12V supply. There's this, capable of 5A output (is that enough?) and it's relatively cheap.  :-)) Output here would be to the 6V supply leads of the winch, with the signal wire coming from the RX.

4/ Ditch the winch completely and brew up a homemade sail winch using sticky-backed plastic and a spare 12V motor, worm gears, other gears, and microswitches. Advantage here is that I have the insane beam room to fit this in, and I could create bespoke gearing/drums for the different needs of my three sheets.

Have a missed any other options?

Andy, ruminating.
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dreadnought72

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Re: Racundra
« Reply #54 on: June 23, 2011, 03:55:10 PM »

3a/ - the addendum!

I'm betting the ~£9 option mentioned above in 3/ contains a LM338T with a heatsink, a couple of capacitors & resistors. I would brew one up myself, but I've hunted around and cannot beat a price for the primary component of about £2 online. Add similar for a heatsink, a quid or so for the capacitors and resistors, a dash more for some veroboard, and the advantages of making my own is quickly offset by the cheapness of a bought-in unit.

(Globalisation and cheap overseas labour seemingly wins once again.)

Andy
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dreadnought72

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Re: Racundra
« Reply #55 on: June 27, 2011, 01:34:38 PM »

The results of doodling on the train ...

Armed with a couple of hours, a pen and paper, and my thoughts on sail control for Racundra. First, the problem:

I have to control a loose-footed jib with two sheets, along with a main sheet, and a mizzen sheet.
The main and mizzen sheets are different lengths, and will therefore require different drum diameters.
The loose footed jib is a royal pain in the bahookie to control realistically - I see why many models go for boomed jibs, for one jib sheet and therefore ease of sheet control.

Given that I want to go for twin-jib-sheet control, how's something like this sound?



The jib sheets are controlled by a long arm - maybe using a 2:1 tackle on each side to get the sheet lengths ok.
This will work fine for close-hauled sailing, but won't for reaching or running.
This is because you need more downwind jib sheet to let out the clew to the right amount when reaching or running, and - at these points of sailing - even more upwind jib sheet to avoid "bagging" and drawing on the sail.
This is not possible with a fixed servo.

This is where the slide comes in: when moving off the wind towards running, the jib sheet servo is moved progressively forwards by the static servo. Result is more jib sheet on both sides to set the jib angle correctly, and not interfere with it by providing enough "free" sheet on the upwind side.

Sounds ok?

Part two of my mental meanderings realised that the position of the moving jib servo can be tied directly into the work done by the winch for the main and mizzen sheets. Sheets in = moving servo aft. Sheets out = moving servo forward. Brewing up a two-drum winch with an added drive to the moving servo is relatively straightforward.

So...

If you now think of one tx stick being able to control two functions, then the proposed control would have the y-axis controlling the main & mizzen sheets in/out amount (down for in), along with the position of the moving servo (down for aft), with the x-axis governing the position of the jib sheet arm (right for starboard tack).

This feels remarkably intuitive - it will be "easy" to select the sheets and jib position depending on the direction/tack required, and "easy" to temporarily back the jib during a tack, for example.

So intuitive and easy, in fact, that I'm left wondering whether this has this been done before? :-))

Andy
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JerryTodd

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Re: Racundra
« Reply #56 on: June 27, 2011, 04:09:21 PM »

I like it - it slacks the sheets when coming about.

But being a frugal sort, if not stingy, I still wonder if there isn't a one servo way to do it.

Maybe if the arm hauls back on the sliding-servo as reaches it's travel limit.  I haven't worked out the geometry, but at a glance it looks like it might save a channel. (see attached)
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dreadnought72

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Re: Racundra
« Reply #57 on: June 28, 2011, 10:27:09 AM »

Hi Jerry!

Let me get my Pondering Cap on.  :-)

Your spring solution doubles the forces on the servo when close-hauled - it's having to keep a sheet taught and stretch that spring. It might be power-hungry. Or even thread-strippingly-unpleasant, depending on the size of the rig!

When running (servo forwards) there's no bias to the sheets - so which side will the jib fly? But, on second thoughts, I think this isn't too bad: the main sail blocks much of the jib anyway (unless sailing goose-winged and, in real boats, that's a relative rarity). So the jib can make up its own (semi-ineffectual) mind.

I think the real benefit of the "spring" version would be in improving the geometries in close-hauled/broad-reaching sailing, and it would boil down to selecting the ideal geometry/correct spring tension to achieve the best results. One for the experimenters, maybe?

I'm leaning towards driving my moving servo by a threaded rod, powered by the winch. I've enough space available for this contraption, so I think my next steps are:

1/ Calculate the geometries required in Racundra's case.
2/ Evolve a plan of where the sheets ought run.
3/ Opt for choice 4/ in my list made earlier and start playing with Meccano developing a bespoke winch solution. And a full-bloodied 12V "we don't need no stinking BEC" one, at that. In this instance, I'll only need two servos: the moving one for the jib sheet arm, and a control one (think microswitches on levers) working with feedback from a (geared down) quarter turn off the main winch motor.

Incidentally, I do like the website in your sig. And you're a re-enactor, huh? I have been known to do such things myself.  %)
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JerryTodd

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Re: Racundra
« Reply #58 on: June 28, 2011, 01:31:03 PM »

The spring, or bungee, or whatever need only to be strong enough to pull the servo forward, but there's nothing saying the set-up can't be reversed and the spring pull the servo back instead.  Then it assist against the pull of the sheets and when off the wind, the servo is assisted by the sheets in pushing it forward.

When sailing, typically on helm's-a-lee the jib sheets are let go and the headsail's are brought over with help from the wind.  When the sails are sheeting home, the windward sheets are slack.

We modeler's tend to fore-go the whole operation with clubed or short footed jibs.  When we do run P/S sheets, it's basically a taught-line closed loop system meant to prevent slack lines snagging.

There's got to be some way using odd shaped disks, levers, tackle, etc to better replicate prototypical operation without a second servo.

I've got 3 heads'ls on a 1:36 scale square-rigger to work out, and a 1:20 Baltimore Clipper coming up with 2 heads'ls and a loose-footed fores'l.  I'm always looking for ideas to deal with this.
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andrewh

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Re: Racundra
« Reply #59 on: June 28, 2011, 08:13:03 PM »

Andy

Sorry not to have been pitching in recently - your thinking on BEC is (as ever) impeccable the price of the widget you showed us looks pretty reasonable

<<I'm betting the ~£9 option mentioned above in 3/ contains a LM338T with a heatsink, a couple of capacitors & resistors. I would brew one up myself, but I've hunted around and cannot beat a price for the primary component of about £2 online. Add similar for a heatsink, a quid or so for the capacitors and resistors, a dash more for some veroboard, and the advantages of making my own is quickly offset by the cheapness of a bought-in unit.>>

I kinda assumed there would be a 6V equivalent of a 9805 (9805??)  I salvage them for free out of dead equipment, also the electrolytic capacitors
(I'm not mean you understand, just careful  :})

Jib sheets - sorry again, I must have missed something quite basic - loose footed jib sheets sheet exactly the same as sparred ones.  See my thames barge with 3 foresails (but I won't attempt to name them right now)
You can get different travels with a single arm servo by using different radii and even double purchase if necessary.

Is the problem of getting the sheets around a forestay?
There has been extensive and learned discussion of this issue on severial of the fora on  http://www.rcgroups.com/scale-sailboats-653/
I can find the relevant bits if they would be of interest
andrew
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JerryTodd

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Re: Racundra
« Reply #60 on: June 28, 2011, 08:46:36 PM »

Quote
Is [it] the problem of getting the sheets around a forestay?

Yes - exactly.

Loose footed sails on models tend to get sheeted to a fixed point on the center-line usually resulting in them being sheeted in too much and spoiling their efficiency - when on real boats they often sheet to point outboard near the bulwarks (when they wrap a stay) or to a traveler (when they don't).

The subject's been dealt with in several ways over at RCGroups.com, but they all still use a constant tension set-up that drags the clews over the stay under tension and don't allow the heads'l to sheet out properlyl when sailing off the wind.
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dreadnought72

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Re: Racundra
« Reply #61 on: July 08, 2011, 12:06:27 PM »

Ok, after a bit of ponderin' juice (courtesy of Morrison's range of unusually-named bottled beers), here's a semi-scale view of how the sliding jibsheet system would work:

Click here  ...you'll need a Flash Player-equipped browser.

The box, top left, is the two-axis tx stick.

Down is sheeted in for close-hauled sailing, middle is for reaching, top for running. This axis would also drive the winch drums for the main and mizzen sheets.
Left is starboard tack, right is port tack. This is effectively a digital setting - one or the other.

The sheets (red and green) do not change length, but don't properly reflect what would happen when/if the leeward one is loose. You'll have to apply a little imagination to think about what happens in those circumstances!

The sheets never let the clew of the jib pass forward of its tack - so Chinese gybes aren't possible, and there's not enough slack for the clew to get caught up on the tack.

In a real set-up, the jib fairleads would be further apart, and further aft of the clew of the jib, making the geometry a little better for real-world sailing.

The blue line with blobs on is the sail's "normal". I was hoping to accurately depict the sail and its curvature depending on the distance between tack and clew, but this surprisingly straightforward task involves some deeply serious maths, skirting solutions to the equivalent of Kepler's Equation. Don't look it up: you'll most probably go mad.  %% So I've cheated the sail, but it's close to what would be seen.

I think this is the way to get things working.  :-))

Andy
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dreadnought72

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Re: Racundra
« Reply #62 on: July 30, 2011, 08:05:01 PM »

This morning I danced a dance to placate the glassfibre gods.

They're a rascally bunch, always on the look-out to ensure that your cat leaps onto the resinously wet surface at precisely the wrong moment. Often they lie in wait to hide your previously-cut tissue the instant you've finished mixing a batch of the stinky stuff. And - of course - they particularly enjoy ensuring that you run out of resin or catalyst or tissue or brushes or gloves at the worst time.

...But my dancing must've worked, because I've now got a sheet of tissue firmly polyestered to the hull. No lumps, air bubbles or, indeed, anything stuck to me, which is gratifying. Inside, I've gf'd the centreplate case and poured some resin into the bilges. The mixes were good, as they've all gone off on schedule, and the boat's back in the cupboard to harden off for a few days before the final filler is slathered all over it.

And at that point, the boat'll go into the bath for the first estimates of how much ballast I'll need.

Racundra weighed about 7 tonnes, so the model will come in just shy of 14kg. My battery is 2.6kg, the hull as it is now is about the same, and I doubt they'll be more than another couple of kilos when sails, spars, decks and crew are added. I'm guessing a lead bulb around the 4kg mark will be appropriate, with something like ~3kg of internal additional ballast. It all feels just about right:-))

Andy
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dreadnought72

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Re: Racundra
« Reply #63 on: August 11, 2011, 02:17:52 PM »

News just in!

Racundra floats.

Now sheathed in glassfibre and P38 - but still in need of a substantial sanding - the Racundra was popped in the bath for ten minutes to see how things are. (It's maybe worth pointing out that she only just fits.) And she floats very well: right way up, keel down, and everything.

I have some changes to the weights listed above, though: the hull is currently 4kg (up from the guessed 2.8kg before fibreglassing) rising to 6.6kg with the battery in place. It took another 5kg in the form of lead diving weights placed internally to get her just about to her marks: it's hard to check this exactly when there's no obvious waterline to follow.

This suggests the lead bulb I was considering of about 4kg is wildly off the mark: it'll be too much - but that in itself is not a bad thing. The current keel is remarkably resistant to sideways movement, and the insane beam, along with the tight turn of the bilge, makes her very very stiff and stable. I'd expected good things, but it was more than I had looked forward to.

Indeed, when on her marks, I popped on a 1kg weight to the hull edge at her widest point (9" off the centreline), and her gunwhale was still completely clear of the water. She'd take 2kg no problem. (That's the equivalent of twelve adults on the original vessel sitting with their feet over the rail). So...

The original had a centreboard. I'm going to have a (removable) fin on the model, a little deeper than the centreboard, but I'm not going to bother putting a bulb on it. I'm going to melt the diving weights into numerous small, 55mm long, ingots and pop these into the keel slots between the frames where I have excellent access.

Final ballasting won't occur until she's fully decked and ready to go, of course.

Oh, and I should report that there's a small weep on the base of the centreboard case - though it's nothing some thin resin and paint won't cure.

Next task: sanding, sanding, sanding, more sanding and then painting. I bet you'll want pictures, too!

Andy
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roycv

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Re: Racundra
« Reply #64 on: August 11, 2011, 02:44:38 PM »

congratulations on a superb build and description.  If it helps, i slide a length of piano wire into the lower seem of the jib and this keeps it in shape, a quite small gauge works well.
regards Roy
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dreadnought72

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Re: Racundra
« Reply #65 on: August 11, 2011, 05:47:00 PM »

Thanks Roy. I've read of piano wire inserted into the vertical sides of square sails for advantages when close-hauled. At the moment my biggest sail question is with regards to the battens on the main. The leech is large, and will cry out for battens when sailing, but I don't recall having read about their use much in models. Room to experiment, I think?!

Andy
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andrewh

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Re: Racundra
« Reply #66 on: August 15, 2011, 12:45:23 PM »

Andy

Battens:  I have limited experience (but that's never stopped me opining before) of battens but for early trials I would suggest cutting the sails from free/cheap economic materials - I usually use umbrella nylon or old polyester/cotton shirt - or even polythene bags.  Cut with soldering iron.  That way you never get hung up on modifications or scrapping and starting again

Battens - for Footy use I attached drafting film (that's "fillum" to you, Andy :-)) with double sided tape and also have used laminating film ironed in place. 
btw - if you open up a laminating envelope - preferably one of the matt type then you have sheets of polyester (mylar) film with hot-melt adhesive on the back - lots of uses!
andrew
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dreadnought72

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Re: Racundra
« Reply #67 on: September 05, 2011, 02:46:28 PM »

Andrew - just to catch up, the sails are made. Look back a page. They'll be on the boat whether they work or not%%

Meanwhile, having got most of the way down page #2 of this thread without a photo, it's clearly time the redress the balance.

Racundra, blessed by a sunny September day, went outside for her second major sanding since the glassfibre work was done.



Here she is, basking in the golden rays having had yet another sanding with the long board, and a dash of wet-papering (240 grit) to remove the scours. I'm currently painting white-on-black to give me a layer to work to. The "exposed" wood shown here is still under 1mm or so of polyester resin, so there's nothing to worry about. The task at the moment is to fair the last edges of the glassfibre mat I put on, in order to develop a smooooooooth finish. I'm just about there, I think - a couple more coats-and-sands should do it.

Meanwhile, here is the 'lectronic layout, done ages ago, which hasn't been demo'd yet:



That's the speed controller for the electric motor, and the distribution block for the various cables 'n' stuff. This is portside of the battery holder, and it will be accessible when the roof of the cabin's off. Though I suspect I'll be needing to remove the battery for access when required. My primary, overriding, concern here was to have neat wiring for once. I see builds on this forum that have wiring which is gorgeous beyond compare - certainly to my usual "this wire's almost long enough to stretch that far" approach.

And finally...



The bit that I would be tempted to pretentiously call the Main Bus Switchgear. This is the area that will be under the small (55mm diameter) forward hatch when the decks are on. The two fuses (main power and motor) are here, the phono charge socket, and two switches - one for the main power, and one for the ESC/radio. Did I need two switches? Not particularly ... but "port" and "starboard" made some sort of sense at the time!

The square hole in the ply sheet is for the samson post - this will be firmly glassfibred to the keel once in, and this entire area (hidden under the foredeck) will be stuffed full of expanded polystyrene bouyancy, living just a little room get some much-needed lead ballast up forward once done. (During the float test, and due to where the cabin is, it's going to be too easy to get her down at the stern: far harder at this end.)

Hey, it's looking lovely outside today: must get painting (again) O0, and hang the washing out!  :embarrassed:

Andy

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dreadnought72

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Re: Racundra
« Reply #68 on: January 11, 2012, 11:57:43 PM »

A hyperboloid is a mathematical surface defined by two opposing curves. Think of a horse's saddle: the bit you sit on is doubly curvy.

Decks are hyperboloids - there's a shear, a rising, fore and aft, and a camber to port and starboard. No sheet of wood, which is flat and dimensionally more-or-less stable, takes well to being bent to fit a hyperboloid: forcing it to do so causes compression and expansion at some point.

On the Racundra, now that the insides are done, I've made a start on the decks-and-above stuff: the first stage has been to plank the subdeck using strips of wood which allow me to conform to the changing hyperboloid shape of the deck's surface. Above this will be thinner "real" planking, but first I've had to face my (crash of thunder) bÍte noire:o

The cabin.



When Racundra was being built, she was built the right way up. No doubt the builders used plumb lines to ensure that the sides of the curved cabin walls (that bit with the elliptical and round portholes in the top drawing) were vertical to the local horizontal as they nailed and glued stuff together. To define the top of the cabin walls they could measure off from lines running to the building shed's roof beams.

Over to the model. I had a hole in the subdeck the right shape for the cabin, and yet no easy or obvious way to ensure that similar vertical surfaces would be added - the changing camber of the deck ensures that the angle 'twixt deck and cabin wall is varying all the time. And I had no simple way to measure the cabin wall height.

The solution, after much thought, was - as ever! - cheat!  O0

The front of the cabin meets one of my frames. My frames are vertical. It struck me that a looooong narrow strip of balsa, glued up out of several pieces with the grain parallel to the short edge, could be glued to the top of this frame and then slowly bent, glued and pinned to the subdeck edge all around the cabin to the aft bulkhead. The balsa - resisting curvature in two dimensions - would follow the curve of the cabin without distorting from the vertical as it did so.

The strip is narrow, but taller than required. Once set, I've been able to trim off the excess under the deck, and now have enough material "above" the cabin roof to allow me to mark the roof line, using heights as measured from the subdeck.

Trimming that off and cutting the portholes will follow later this weekend. There will be pictures!

The lesser evil (the bÍte grise?) that is the curved shell of the (removable) cabin roof comes later. I have evil plans to succeed in that.

Andy
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andrewh

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Re: Racundra
« Reply #69 on: January 12, 2012, 10:42:08 PM »

Andy

Glad to see you have faced and fixed your bÍtes de multi-couleurs.

I found myself about to dive in in the middle of you last post - but no need  - you have neatly done the deed.  I was about to mention iron-on edging strip in real wood, which I have used for similar coamings with complex curves.

It can be got from good wood work shops, and I have applied it too deep round a  coaming in a cambered and sheered deck (nay, hyperbolic) then ruled either from the deck (or from the waterline ) to get the final height.

Please keep posting the pics and explaining the thinking - I find that most useful

andrew
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dreadnought72

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Re: Racundra
« Reply #70 on: January 15, 2012, 07:19:23 PM »

And as the weekend turns into Kitchen Patrol (I am ordered to do the roast spuds tonight) there's just time for a swift update of my productive few last hours:

Here she is, with the subdeck on, cabin wall finished & strengthened, portholes cut, much of the aft coaming done, and the head/kitchen roofed over.



That thing on the foredeck between mainmast and samson post holes is the switch/charging/fuses area, now surrounded by a steamed plywood surround. Originally, this was the forward escape hatch, just wide enough for a fella to get through, and (at one eighth scale) just wide enough for all the bits I wanted in there. There will be a sealable lid.



Here's a view looking forward into the cabin. The white blocks are expanded polystyrene. (This boat is full of it). The size of this gaping maw is, incidentally, about 11" wide by 12" long. Loads of room to get in and fettle. Once the balsa coaming was glued in, I glued two thin strips of ply around the inside at the top: this strengthens the walls vastly, and will provide a surface for the cabin roof to sit on. You can see that the lower parts of the cabin walls stick below the level of the subdeck - these'll be trimmed back later. Those two vertical strips at the front are the aft end of the mast partners, which are morticed and tenoned into the frame in front of the cabin. Tough as old boots. The gap between the poly blocks at the front will give me access to chuck in a couple of pounds of lead where it's needed, later on.



And finally, further aft: the companion way. Now no longer a wooden structure sticking up from the bare frames like the sore remaining tooth on a Lanarkshire granny, it's become part of the whole thing. Hurray!

More polystyrene is buried within. The area on the left was the galley on the fullsize Racundra, and the tiny head was on the right. Doors are to be added. You can just see the right hand side of the tiny catflap door into the cabin.

The coaming at the sides here will drop down in smooth, sweeping (and maybe even matching!) curves to provide a back rest in the steerage well. Which will be the next stage of building.

(See, I do to have a plan. It's just that I'm very slow!)

One thing I've been delighted with here is that - while the construction has caused me a pile of headaches over the last week or so - the preparation and planning and (dare I say it?) accuracy at the beginning is paying off now. Frames are where I expect to find them, and the original builder's plans are resulting in many many "ah, that's why this is so!" moments. It all begins to make sense.



Next time: we meet the comfy chairs!

Andy
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dreadnought72

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Re: Racundra
« Reply #71 on: January 24, 2012, 01:23:57 PM »

...comfy chairs? Well, maybe not this time, but they are on the horizon.

You see, today's task is to start work on the cabin roof. Job one:



Line the opening with cling film (this is important!), find a pile of clamps, then glue up two whippy pieces of ply strip and combine the lot into a glue-flicking uncontrollable near-three-foot mass which only takes on order once the bends are done and the clamps are on. This process is to be repeated a couple more times in order to build up a solid laminate "inner" that precisely fits the cabin.

When internal struts and bracing are applied later, the plan is to have a solid, properly curved base on which I can build the roof. The roof will overhang this structure and rest on the outer edge of the cabin walls (there's a handy "beading" on the very edge in order to cover up the near-inevitable woodworking errors). I'm hoping, with the application of catches, latches, magnets, mastic and magic that this will be at least splashproof. And - better - possibly even fat-dollop-of-waterproof.

Next on the list:




This impressive piece of electrical butchery is what happens when a greedy Hitech servo requires 6V.

Does it work?

I dunno.  %%

I'm building up the courage to plug it in.  :embarrassed:

Andy
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Norseman

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Re: Racundra
« Reply #72 on: January 24, 2012, 02:49:55 PM »

build up a solid laminate "inner" that precisely fits

Hi Andy

Thanks - I like that advice and I can certainly use it for many things.
Enjoying your whole build too.

Dave
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dreadnought72

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Re: Racundra
« Reply #73 on: January 24, 2012, 05:44:46 PM »

Hi Dave - thanks for the comments. I've used four pieces of 1.5mm ply which has now set and feels pretty solid. It's taken (and will hold) the curve well. I'm going to let it completely set overnight and then add the brackets.

Meanwhile - news just in.

One substantial amount of courage later.

I wired everything up, and threw the switches.

No magic smoke was emitted  :-)) and the winch took off with an impressive, torquey, 6V-meat-and-two-veg grunt  O0, seeking (I foolishly thought) to find its dead spot.  :-)) :-)) And off it ran. And ran.  :o And ran.   >>:-(

No amount of stick-twiddlin', switch resets, or anything else (short of killing the power) got it to stop.  <:(

My thoughts were:

1/ Does a 4.8V pulse signal get somehow "lost" in the 6V awesomeness that was powering the winch?

2/ Did I need to ensure the pulse signal's 0V was directly connected to the ground running into the winch? (I think not - unless something mighty weird is going on inside the BEC circuits in the ESC).

3/ Do I have a tea and a think?

Not really knowing what I was doing - indeed, there are times when I have to Google "which end of the soldering iron should I hold?" -  I took option #3.

I returned ten minutes later and have chopped things up a bit. I've ditched the BEC on the ESC. Who, after all, needs a puny 4.8V when I have a solid, seemingly reliable, and certainly working 6V on call? So ... I've wired the regulator into running the receiver, winch and servos. The ESC is now just an ESC.

All seems well. The winch now does what it did at the start of this post, but with the added benefit of stopping where I want it to. This will be very useful when there's strings attached.

It also means that I can go for a sail with the ESC and motor utterly isolated from the power supply, given my switch wiring earlier. I don't think this is necessarily a Bad Thing.

Right - I've got gratings to make.

Andy
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dreadnought72

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Re: Racundra
« Reply #74 on: February 02, 2012, 11:51:36 PM »

Regretably the oft-promised gratings and comfy chairs have to come later. But before you boo and hiss, let alone resort to this emoticon  <*<, I have to report success!

For, tonight, the solder flew and wires were hacked. Neither myself, nor the carpet, nor the boat got burned.

And as a result the Mark #1 Auto-Stop Jib Sheet Winch is working. Well, at least its electrics are. This is it in its raw state:



Top left is a spare Buehler. I have many! This is a near-twin to the one that drives the propshaft. (The only difference is the shaft has been hacked off the back of the prop one, in order to clear the centreboard case.)

Bottom left are two microswitches, both wired to COM and NC, so they're shorted unless depressed. This is important!

Middle right is what I'd laughingly call the brains of the operation, based around a spare Viper 15 ESC. Its board mounts a pair of fuses and a couple of diodes, rated for 5 micro amps when driven the wrong way = not nearly enough to swing the Buehler.

The Buehler will meet the Meccano tomorrow in order to make a five-ish-turn-in-ten-seconds-or-so drum for the sheets, and a geared take-off from this, doing less-than-one-turn will be cunningly arranged, probably using a well-crafted twig, to impact the microswitches.

If I get the switches in the correct position, and the motor turning the right way, then a horizontal stick on the TX will drive the winch, at any speed, between the end stops of the winch. Due to the nature of the fiendish wiring, these end stops will be end stops: it is impossible to drive the motor further when one or other of the switches is depressed. Only backwards, away from the switch.



When not at an end stop, s1 and s2 are closed. The output of the ESC, at a and b, drives the motor in either direction.

If s1 is open, then its partner diode will only let current flow when a is positive. If s2 is open, then b must be positive for current flow.

Most simple.

(Well, it has to be, in order for me to get it.)

Andy
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