Opti-BF20 on rails

Jari has almost completed the mechanical part of our cnc-mill upgrade: fitting a new 500 mm X-travel table on linear rails and installing ballscrews.

The bearing holders for the free end of the ballscrews are not done yet, so in the pictures the free ends are ...free. Here you also see how everything is assembled: the Y-axis ballscrew and rails sit on the base of the machine, there's a two-part saddle plate on the Y-bearing blocks, and the X-rails/ballscrew attach to the underside of the table.

The new table assembly is a bit higher than the old table which means that Z-travel is restricted. We also need to make a slot in the Y-axis saddle plate to allow for the axis coupler to slide under it. Now Y-travel is only about 150 mm, but it should go up to 200 with this mod.

Initial tests with the old stepper motors and temporary crude axis couplers are promising. We have elminated backlash, and friction is down a lot meaning higher velocities and accelerations are possible. Can't wait to see how this thing moves with the servos!

Differential Encoder Interface

I threw together this board for decoding the differential encoder signals coming from the servos. I don't like etching two-sided PCBs, but I'm not sure I like this many zero-ohm jumpers either... It's basically four DS3486 ICs with input filters + a lot of connectors.

The circuit is borrowed from an IRF application note, second to last page of this document: http://www.irf.com/technical-info/refdesigns/dg-irmck201.pdf

Not very compact or cute, but hopefully functional...

Source: PADS PowerLogic schematic and PADS PowerPCB PCB-layout.

Helsinki Model Expo 2007 - Day 3

Last day at model-expo, my first try at using google video!

First the new Futaba 2.4GHz radios. There are two wheel-model radios already on the market, and I was told two stick-radios (a 3-channel and a 6-channel model) will be in stores very shortly. Priced close to the Spektrum offerings at around 200 eur. Then to the pool for some scale-models. A fast electric racing boat after that, followed by some aerobatics, and some car-racing at the end.


(the noise from the fans was not as bad as it sounds in this video...)Then MicroMagic sailing! We had a lot of fun and a fair bit of spectators for each of our sailing shows, about 15-20 minutes every hour. You can see that the two fans we brought with us don't cover all of the pool, and that the wind speed is quite fast near the fans and lighter downwind. More boats and more fans for next year!

When someone interested came to talk to us it was so easy just to point to the many MicroMagic vendors and say 'there, that's where you get it and it costs around 250eur with everything (boat, radio) included.' This relates to what I wrote earlier, I believe the success of the micromagic largely depends on it being cheap and easily available.

So, for the IOM class to experience continued growth I think it would be a great help if a competitive boat would be mass-produced (in ABS or similar). I know Graham B in the UK and John E in the USA have had some plans... but nothing seems to have materialized yet. Newcomers to our sport don't want to send 1000 or more euros overseas and then wait 3-6 months for a (hand made) boat, they want their new boat now, cheaply, and from the local hobby store.

Thanks to Jari for lending me his MiniDV camera.

Helsinki Model Expo 2007 - Day 2

A long day at Model Expo today...

Our main new attraction for this year was Micro Magic sailing in the pool - and it worked great!

This picture shows a general view of the pool, the marks, and the blowers(the yellow and blue fans at the top of the picture) that created wind for us. The size of the pool was 14x17m and we sailed a windward-leeward course along the diagonal of the pool.

Here the boats are rounding the leeward marks.

Rounding the top mark, with one of the fans in the foreground.

Looking for the stream of quickly moving air on the run.

What can be done better next year? Now we have three boats, but there's certainly room for more. Perhaps up to 6-8 MicroMagics could be sailing at the same time. I'm sure that would please the crowd as there will then always be something to watch and incidents all the time. One or two more fans would not hurt either. The power of the fans was fairly OK with a nice gust towards the top of the course and steady decreasing wind towards the leeward marks. Finally, frequency allocation between us, the motor boats, the car track, and robo-war was a bit of a hassle - bring only 2.4 GHz radios next time!

A general trend across all disciplines in model hobby(cars, boats, airplanes, etc.) seems to be towards smaller, lighter, and cheaper models. New tiny electronics makes it possible to build these models. Here's a plane with a small LiPo cell in the front (I'm told these cells can come from bluetooth headsets or similar), a combined receiver/motor controller in the middle, and two motors in each wing for propulsion/control (people use motors from CD-players, cell-phone vibration alarms etc)

Even the smallest mini servos are too heavy for the lightest models, so people use these more or less home-made coil/magnet actuators. There are two magnets, one on the moving control surface, and one on the stationary part. The stationary magnet attracts the moving magnet and thus centers the control surface. When a current is applied to the coil the control surface can be deflected each way. Weight 0.3g . Brilliant!

More and more devices are showing up on 2.4 GHz. This is a ready-to-fly plane and transmitter from the Kyosho stand. With the electronics becoming cheaper and cheaper all the time I'm sure these things will show up in supermarkets for about 50 eur or so.

There were many heli/airplane simulators hooked up to a computer and a wall-projector. Great fun, and no expensive re-building after each crash. I might actually get one...

Another futuristic looking transmitter from the Kyosho stand. (is it for a simulator?)

One company was showing tiny cnc-lathes and mills. These were from some uknown Asian company. Looks like they are entry-level hobby-cnc stuff: small stepper motors connected to normal threaded screws.

These machines are kind of cute, and may be suitable for making a small number of very small parts in soft materials. I'm afraid that Jari's and my own cnc-hobby (or is it an addiction? 🙂 ) will require something substantially bigger and more expensive for our next machine (think Haas Minimill or similar...)

A nice long-exposure shot of one of many slotcar tracks.

I'm hoping to shoot some sailing videos tomorrow.

Preparing for Model-Expo

I spent most of the afternoon and evening preparing the Finnish RadioSailors stand at the Helsinki Model Expo which will be open Friday - Sunday. The plan is to have 2 IOMs, one 5.5mrc, and about three MicroMagics on display. A 32" LCD screen displays sailing videos while people interested in the sport can pick up an information leaflet or ask questions from our club members who will be manning the stand. New for this year is MicroMagic sailing in the pool (which is 22cm deep I am told) on Saturday and Sunday. Timo and his team from Tampere are bringing three MicroMagics while I fixed the wind: two powerful blowers leased from cramo (the two black dots in the far corner of the pool below). A quick test run showed that two blowers of this size were quite well suited for the 14x17 m pool. When blowing diagonally across the water all but the extreme corners were covered with wind, and even at the far end we had at least 2 m/s. Ofcourse the wind speed distribution is a bit uneven with the speed going significantly up close to the fans, but you can't have it all...

Noux building in Norway


Steinar from Norway sent me some more pictures of his Noux boats. He has completed the first boat (see below), and is now building a second one.


Another view of the spray-painting setup.


The bulb is home-made, cast in a plaster mould.


Here is Steinar's first boat, now completed and painted. I posted some building pictures earlier here and here.

Steinar asked if there is a Noux-logo. Sure! I just need to post it online in some common format. Stand by...

X-axis progress

Now that we have the new spindle on our mill, and the linear rail+ballscrew conversion for the Z-axis have been working for a while, it's time to upgrade the X and Y axes.

Jari has made some good progress on the table/X-axis. The IKO 15 mm linear rails are mounted, we've machined and attached the bearing holders for the ballscrew, made a motor mount for the servo, and also worked on the steel saddle plates. The new talbe is much bigger than the old one, and will allow about 500mm of X-axis movement. That's going to be enough to machine fin and bulb moulds for an IOM in one go - something that we can't do right now.

Here's a close-up of the motor mount, all parts machined from aluminium using our own mill. There's room for a coupler between the 12mm motor shaft and the 8mm ballscrew end. The motors we are using are 1.6 Nm continuous torque DC brush motors from Camtronics. Keeping to the KISS principle, we are hoping the motors are strong enough to work in direct-drive (no belt reduction or gears).

This photo shows the ballscrew (16mm diameter, 2.5mm pitch, from metallstore.de), the ball-nut, and the X-saddle plate with some steel bars under it to make room for the ballnut. Next up is a similar assembly for the Y-axis. That's going to be a bit more complicated since the parts will eventually have to be mounted on the very mill we are making them with! Hopefully not too many iterations of disassembly/assembly will be required...

Jari has also made a new tool-holder:

Micro Magic

Timo brought along his latest toy, a Micro Magic, to our annual radiosailing winter meeting. This thing really is small compared to a Marblehead or an IOM! It's an all 'plastic-fantastic' ABS moulded boat, but you do have to glue the deck to the hull in this Racing version of the kit. The vitals are LOA=554 mm, Beam=178 mm, Weight=980 g, Height=980 mm.

The fin and rudder are made of ABS plastic, and the bulb is lead. There are different sized bits that can be inserted fore and aft of the fin in the finbox to adjust the position of the fin for different conditions.

An arm-winch controls both sails, the mainsheet on the left side of the boat and the jibsheet on the right. Timo is using a micro-servo for the rudder, but I understand standard sized ones are used too.

There's one central hatch with a rubber seal, but I doubt it's watertight enough to be used without tape on top.

The standard carbon mast is 5 mm in diameter, and comes with two sidestays, but Timo has made some more rigs using 6/4 mm carbon tube and intends to use these rigs without sidestays. A bit surprisingly rule-writers around the world have usually not put an upper limit to the number of rigs, so I understand some skippers have made up to 5 or 6 different rigs! (the smaller ones all fit within the biggest one)

In terms of number of boats/skippers the Micro Magic is a definite success with ca 1000 or more boats registered in both Germany and the Netherlands. It makes you think that the traditional international radio sailing classes (IOM, M, 10R, A) have somehow failed since they have not as far as I know attained similar popularity. Marketing wisdom tells us that this must be because of the five Ps: Product, Place, Price, Packaging, Promotion. (I'm leaving 'Product' last in my ramblings below, since I have the most doubts about this P)

Price: the Micro Magic wins hands down over an IOM or any other international radio sailing class. The whole MicroMagic kit with the tall rig, a basic two channel radio, and everything you need to go sailing costs about the same (300 EUR) as three suits of sails for an IOM. By comparison, I estimate a competitive IOM with three rigs and radio from a commercial builder costs about 2000 EUR. Home building a boat to the same standard and performance is not much cheaper.

So does price really matter? Die-hard radio sailors usually say no: travelling to events, staying in hotels, spending all that leisure time racing etc. constitutes a much bigger investment than the price of the boat. For someone who travels internationally every year and to all big events nationally it probably doesn't matter if the boat costs 500 eur, 1000 eur or 2000 eur. But for the beginner it does matter! I see very few newcomers to competitive IOM racing in Finland - maybe that's because of the high price tag? To really get into the class you need a competitive, watertight, and fully functional secondhand, or almost completely built new boat, and that's going to cost you about 2000 eur...

Place: go to the local hobby store, hand them your credit card, and within 1-2 days you will be on the water sailing this boat. Depending on your country, getting an IOM is either a lot harder or just a bit harder. There are no industrial builders (The Robbe Windstar is not really a competitive IOM), so you can't buy an IOM from a hobby store, and the salesperson in the shop is not likely to even know there exists such a thing as an IOM class. All manufacturers are small, most amateur hobbyists and a handful of professionals, and usually sell boats in kit-form to keep down the cost. In countries where there are no commercial builders the situation is even worse. The seasoned radio-sailors do know the international suppliers, some personally, but a newcomer is quite unlikely to send a big amount of money to an unknown builder in a foreign country (and wait the usual 4-12 weeks delivery time).

Packaging/Promotion: Probably about equal between an IOM and a MicroMagic. Promotion will largely depend on what class your local club sails I guess.

Product: Here's where my doubts are. When moving from a Marblehead (4-5 kg weight, 1.3 m length) down to an IOM, the boat felt very nervous, unstable, and hard to sail in the beginning. An IOM is also definitely harder to trim for neutral balance. This was a move down in length from 1.3 m to 1 m, and in weight from about 4.5-5 kg to 4 kg. I haven't sailed a MicroMagic yet, but we must be talking about a completely different behaviour at 55 cm overall length and < 1 kg displacement.

On the other hand, do skippers want a boat that sails and handles gracefully, like a full-scale boat, or are most skippers just looking for a level playing field where they can have fun racing the boats? If the latter is most important, then there must be a bright future for boats like the MicroMagic. In reality very few people have time to design and build their own boat, so I don't think this argument against industrially produced boats really holds.

All of this seems to indicate smaller and industrially produced is better. But there must also be some kind of scale effect: If I show my IOM to someone on the street I'm sure most people would recognize it as more than a toy, capable of racing in widely varying conditions etc. Show the same people a MicroMagic and they will definitely think 'toy'.

This is an interesting topic, so I'd love to hear some thougs from my readers:

  1. I clearly haven't done my homework well enough, so could someone fill me in on the numbers of boats in the big countries for the various 'industrially' made classes: MicroMagic, RC-Laser, Victoria, etc.
  2. How does the MicroMagic sail in different conditions? preferably from people who have a solid background in Marblehead or IOM racing! How does it compare to an RC-Laser?
  3. If you have some deep thoughts on how to make a radio sailing class really succeed I'm also interested.