canno1797

Hi Tigertass,
I have emailed you the plans I hope they come across Ok. Should be a good boat to build, are you going to race yours.

cheers Andrew

tigertass

Yes, thanks so much, they have arriwed!

rcrawford

Hi Surfdabbler

I have been following your build for a while. Looks awesome nice job. I just finished an iaac120 modelled after the France areva challenge. I enjoyed it so much would like to start a vor 70 . I requested plans to no avail .Requested again today. things may have gotton lost. maybe someone could help with that if they dont arrive.Will be watching your build as i go. I still have about 3 months before ice out around here.

thank you rcrawford

canno1797

Hi Scrawford04,
if you send me your email address I can send them to you. I had to wait a long time to get my set as well. Should turn out to be a nice build.

cheers Andrew

rcrawford

Hi Smoofty37
I would like to take you up on that offer.Like yourself i would like to start another build. have you started on it yet. What will you be modell
ing your iaac120 after. this is my e mail [email protected]
thank you
scrawford

surfdabbler

This is becoming a "ask for plans" thread! Well, I guess that's what I get for being slow and not updating my build log enough. [8D]

Work is still slowly progressing on the boat. I've just been very busy, and haven't had any time to update the build-log lately, so here's the latest report...

I'm installing servos at the moment. There's a long lead-time to buying mail-order servos, and nobody local has anything useful in stock, but I'm slowly getting bits and pieces to muck around with. I got some HXT servos, some micro 2kg jobs for the rudder and some other stuff, and 3 standard size 7kg servos to experiment with.

The rudder servo is installed and working, which is really cool. The carbon fibre rudder post has been flattened and drilled to take a customised servo arm and cotter pin. The cotter pin is just made from aluminium wire. This makes the rudder easy to remove for transport. Just remove the cotter pin, and the rudder can be taken out.

I'm still nutting out the canting keel servo. The plan is to use a standard servo, but gear it further for more power. The big sail winches are simply too heavy to put 2 of them in this size boat! It's a lot more mucking around though, so we'll see how it goes. If all goes well, I might even modify a standard servo for the sail winch too. Compared to a Hitec drum winch, a modified std servo will be lighter, cheaper and similar power and speed. It will also be a lot of extra work, and that’s what this build is all about.

I've put in some deck hatches, but I'm not sure if they are big enough. I have one hatch for the rudder at the back, and one hatch in the centre. I think I may have to enlarge the front hatch significantly before I'm done, but we'll see. I think the current hatch will be just enough working room to get access to get the keel in/out for transport, but might not be enough access to the electronics.

I've also spent some time making a stand. The boat has got to the stage where it sits nicely on the stand instead of lying around on the bench. I did make one big mistake on the stand though. I should have put the cross supports right near the top and bottom of the stand. As it is, it actually prevents the keel from swinging, because the keel hits the stand. However, when I switch to the shorter scale keel, it might not be so much of a problem anymore.

Oh, and a note of advice to anyone starting a build project... Don't go out and buy a really cool 2m eletric sailplane in the middle of your boat build. From my experience, it really slows down the boat building process. Lots of fun though!

Anyway, photos are always the best bit, so here's some...

canno1797

hi Scrawford,
plans have been sent, let me know if they do not come across. I'm going to start a build thread on the AC 12M so not to take anything away from this build.

cheers Andrew

P.S I bet its nice and wet up in good old QLD at this point.

rcrawford

Hi Smoofty37


Thank you so much for the quick response. Have been looking them over trying to decide which one to model. Just finished painting my ac120. Keep me posted on your ac12 build. Surfdabbler. Nice to see you working on your project again. Will be starting mine in a week so .Learned a lot frome your build. Its nice to have someone do all the hard work.
thanks again guys
scrawford

canno1797

Hi Scrawford04,
Not a problem mate, I have started a new thread for my Team NewZealand boat.

cheers Andrew

brettc

hi the boat looks good i have been inspired to try to build one as well

surfdabbler

Over a month since my last update. The last few weeks have been much time and frustration spent on the canting keel mechanism, building gear and pulley mechanisms, trying to buy small gears and pulleys which nobody in the world seems to sell (more on this later), and hacking servos for which I have no spare parts, and no clear direction.

Let’s start with the servo. Much of the problem is that I need a servo that is small, light and powerful. Cheap is nice, and speed is not too important - it’s OK if it takes a couple of seconds to get there. Problem is, you can’t buy this sort of thing. The lightest powerful sail winch servos are still reasonably heavy, and get very expensive (hundreds of dollars for each servo). Sure, they are really powerful, and I’m sure very high quality, but are they the best solution?

Here’s a quick comparison of the common winch servo options…

Hitec 785HB $60, 13.2 kgcm, 110g, 2.5 turns, 59x29x50, 1.4s per revolution
RMG 280EL $250, 20 kgcm, 134g, 5 turns, 74x54x59mm, 0.3s per revolution
Futaba 5801 $250, 7.8kgcm, 83g, 2-6 turns, 46x25x44mm, 0.6s per revolution

HX5010 Standard Servo $10, 7kgcm, 35g, .25 turns, 40x28x40mm, .15s per 60deg = <1s per revolution.

Standard servo wins on cost, weight, size. It’s not the best in power or revolution speed, but it’s in the ballpark. Where the standard servo loses out is that it just can’t keep going.

What’s an obsessive nut like me to do? There is only one answer – to embark on a journey into the murky waters of servo hacking…

1) Do the continuous rotation hack – pretty standard stuff in robotics, removing the pot and shaving a knob off the final gear wheel. Put on a home-made winch wheel and test it out. Works pretty nicely, and is capable of lifting my 1kg, 28 cm keel roughly 60 degrees up from vertical in a couple of seconds. Nice.
2) Problem – continuous rotation servo has no position feedback, so there’s no way to set the required absolute position. Pushing the control lever left moves it left, and pushing it right moves it right.
3) So, cut hole in side of servo case and add extra gears to put the feedback pot back in place, but slowed down, so many turns of the output spline corresponds to the original quarter turn on the feedback pot. This gives 4 full rotations of the servo wheel with proper servo positioning. Nice.
4) Problem – servo circuitry runs motor at full speed, until servo is within 1 full rotation of final position, when it slows right down and dawdles to the end. Makes sense, because the servo thinks it’s really close to final position, however, with the gear hack, it’s still got a long way to go, and still needs to drive the motor hard right to the end.
5) So, research some servo controller chips, and find out how the circuits work and find datasheets on the common chips. Turns out tuning the motor response is quite easy by replacing a few components, as outline (for the opposite problem) here… http://www.rcgroups.com/forums/showthread.php?t=1016320. Nice.
6) Problem – my servo doesn’t seem to match the common NE544 chip datasheet pinout. In addition, somebody at the servo factory has the very helpful career of filing off the chip identification numbers, so my controller chip cannot be identified.
7) So, reverse engineer the servo circuit board, and correlate the components with the NE544 datasheet, and discover that the circuit is a close correlation, and the chip seems to be fundamentally similar in design to the NE544, but with different pinouts. Nice.
8) A quick web search for other servo controller chips turned up the AA51880PP which has a pinout diagram that perfectly matches what I had deduced from analysing the circuit. http://www.dianyuan.com/blog/u/2009-...1236078510.pdf. Nice.
9) Do some resoldering of the surface mount circuit board to change some resistors. Some experimentation done to determine the best setup for fast movement and minimal jitter. Eventually decided on removing the speed feedback resistor altogether, changing the deadband resistor to 1.2k, and the pulse stretcher resistor to 470K. I've included some of my reverse-engineered diagrams of the surface mount circuit board, and the circuit layout around the chip. I probably won't remember anything about this in 1 week, so don't bother to ask me, but the resistors I changed are R6 (feedback), R3 (pulse stretcher gain) and R4 (deadband).
10) Works. Nice.

Enough on servo mods. If anyone else wants to do this, hack a digital servo, and you can probably reprogram the response and get a better result than I have with my resistors.

Stats –
7 kg.cm (from my servos spec)
4 turns over the standard 0-100% range.
About 1sec per 360, no load
40x46x38mm
45 gms (without drum. 50gm with 40mm sail winch drum)
Cost – about AUD$12 (oh, and a helluvalotta time)

End result is a small and lightweight servo that will do the job without breaking the budget. Photos below.

surfdabbler

Well, once the servos were working, it’s a small matter to knock up some home-made miniature pulleys (did I mention that you can’t buy small pulleys anywhere?), and also made my own drum winch, and string up the keel to give it maybe 10:1 or 20:1 effective gearing ratio to pull the canting keel around.

There are better ways to do this from a leverage point of view, but I’ve mucked around enough with the servos. Time to get on with it and just make it work.

Some ball-bearing pulleys would be nice (Ahem, did I mention you can’t buy this stuff anywhere?) and I might take the pulleys one-step further and put some on the keel itself, as the strings have a fair amount of friction when they are loaded up through the eyelet, but for now, it’s all working.

It is using the original long and heavy keel at the moment, so I’ve limited it to 20 degrees movement to either side. With this setup, it’s about a 2-second travel from one side to the other. I will be making a lighter keel to operate better as a canting keel. I’m planning 750gms at 2/3 the length, and this setup will cant the full 40 degrees. I’ve done the torque calculations – my current servo setup can easily cant the heavy bulb to 30 degrees, and the force at this point is sufficient to put the lighter keel right out to 90 degrees, when the boat is heeling, so the current servo setup will be sufficient. It might be a little slow at 4 seconds full range side to side, so I will try to drop the pulley to 2:1 ratio, and maybe try for some better pulleys to decrease the friction.

I’ve also done the sailing force calculations, and comparing the lighter canting keel against the original designed 1080gm fixed keel, the canting keel will provide increased righting moment (which translates to being able to hold more thrust) up to about 25 degrees, and in addition, the boat is 250gms lighter (accounting for the weight of the extra servo and mechanics.) Beyond 25 degrees heeling, the canting keel falls behind in righting moment, but is still a lighter boat, so should still outperform in any reasonable winds. When looking at heeling angles of around 45 degrees or more, the heavier keel is certainly better, but if it’s tipping that far, performance is no longer your main concern.

In case you missed it in the midst of my boring technical waffle, the canting keel IS NOW WORKING!!! Yaaaay.

Here’s some pics (I know, it looks like the keel is resting on the stand in this shot, but it’s not.)
Also included a picture of how I’m making my little pulleys out of perspex and aluminium, and a nail for the axle.

canno1797

Hey Surfdabbler,
Did I hear the word "ROCKET SCIENTIST", mate you should be working for NASA one thinks. Great work on the keel setup. Me being a slack old fart will just go the RMG way and you can buy very nice blocks for QLD for about $6 to $9 each. How are you going with water proofing the keel box ?[8D]

hew565

Beautiful job so far, surfdabbler!

I have tried to pour lead in a plaster mold, like yours, but there must have still been some water in the plaster, as it flaked away the surface, and even cracked the mold after the second pour. How long did you let the molds sit and dry before the lead pour? I would like to make more than one bulb when I do it!

There are a couple of suppliers of small pulleys for model boats, the one I know of in NZL is http://isobaryachts.com with cheek blocks and bullet blocks in single and doubles. There is probably a supplier or two in AUS too. KDH blocks or Pekabe are the brands I am familiar with.

1967250s

I was thinking the same thing about the pulleys! I have some I got from Midwest Models but they're ten + bucks a pop! So I looked on feebay- lots of small ball bearings are available to make your own blocks, all sorts of sizes. Your swinging keel is awesome, too. A larger pulley with ball bearings will work more easily and a lot less wear on everything.Keep posting!

canno1797

Surfdabbler,
Have a look at this site, This is the place most poeple I know that race RC yachts get there stuff. http://www.rysa.com.au/

surfdabbler

Great link. Yes, I have come across RYSA before, but I forgot about them again, and only found them again today. They have the Pekabe stock. For what you get, they are not so expensive. I will have to buy some of those pulleys for the on-deck rigging, I think, just because they look so nice. If my other pulleys break, I might replace them with these better ones too.

rcfontes

Hi all,

I am trying to find the plans over the past month to start my project.
If posible, can anyone send me the plans.
[email protected]

Thanks,

Ricardo

canno1797

Hi Ricardo,
I have sent you the plans, please let me know if you don't get them.

cheers Andrew

et@worx

Excuse me for the abrupt interruption here. I would also love to get my hands on the plan of the VO 70. I have mailed the Italian guy and no reply yet. I have most of the building material for this project but, no plan. Will any one please be so kind to send me a plan to [email protected]

Thank You.


Simplicity is the ultimate sophistication

surfdabbler

A little more progress...Hey, I've gotta keep up with you, smoofty37. The canting keel is completely waterproof now. I have basically created a flexible wetbox around the inside of the keel.

The hull was fitted to the keel pivot tube, using Q-cell, so there is no gap in the hull (Well there’s maybe .3mm, but it’s a very neat perfect fit. I have added half-height bulkheads infront and behind the canting keel. These support the hull from the fore-aft twisting force of the keel, and also help to stop waterflow if the keel leaks. From there, I have stuck in a small sheet of plastic around the keel to waterproof it, with enough slack to allow for the movement for the canting keel. The plastic is TPU plastic from a kite-surfing kite bladder. Normal PE plastic would get micro-holes very quickly, and would also get increasingly brittle over time. TPU is very flexible and airtight and will last a long time. If anyone else is thinking of using this method, don’t bother going to your local hardware shop and asking for TPU. It is very specialist plastic, and the easiest place to get it is a kite bladder – either buy a spare or scavenge from an old kite. Or use vinyl from an old pool toy. Vinyl will be much easier to get. It’s a little less flexible than TPU, but probably still OK.

For sticking down the plastic, I bought a role of ‘tacky tape’ from a fibreglassing shop. It’s really good stuff. It’s like plasticine, or blu-tac, but much sticker, making an excellent airtight seal with a bit of flexibility. It's used for vaccuum bagging fibreglass moulds, so it's good stuff. It’s also easily removable and resealable if I ever need to get back in, as I may need to remove the keel later for painting.

All the main electrics are in now, with 3 servos (rudder, keel and sheet), 2.4GHz receiver, LiPo battery and voltage regulator. It's all working well, and with a little push, I can sail it around the pool. It’s all waterproof and it’s looking really good. (OK, yes, the more observant of you might see a little puddle of water inside in the pool shot, but that’s all fixed, and it’s looking really good NOW.)

Glued the deck on tonight. Internal access will be a lot more restricted from here, so there’s no looking back now.

Oh, I did buy some nice pulleys (you can see the receipt in one of the photos!). I ordered PeKaBes, but when I got them, they were a different brand - Hales - a local manufacturer. They look very nice. They are also nice and small. I'll use them on the mainsheet above the deck. If my other ones below deck ever sieze, I'll put the nice ones under there too.

surfdabbler

A quick update for today – I’ve been filling and sanding the hull. Lots of dust, lots of mess, but the hull is basically smooth now. I had sanded to 80 grit, then 120 to get it smooth. Now there’s just the little bumps left. I was hoping the Septone primer/filler would do the job, but I don’t think so. I did a test spray of the keel tonight, and there’s marks all over it that I couldn’t see before. Now that it’s all one consistent colour, it looks terrible! All the marks and dents and potholes really stand out. Even 80 grit sanding marks are very visible. Maybe some of these will come out after sanding the primer, but I think I have a lot more prep to do before priming the hull. It looks pretty good in the 2nd photo below, but under a strong side-light, the imperfections really stand out. I might give some spray-filler a go, as it might be easier than another run of Q-Cel. All this smoothing and sanding is definitely the most boring part, but I hope it’s worthwhile in getting the best possible finish in the end.

I have also started making the second keel (I feel like I will have built the entire boat twice over before I’m done). I glassed the shorter keel today, along with the 2 dagger boards, so they will harden up over the next few days, and then I’ll see whether they need another layer of glass or not. The plaster mould for the lighter keel bulb is also ready to go for the lead pour when I get the time. I’ve gone for a 3-piece mould this time, so that I don’t have to drill out the slot for the keel, so we’ll see how this goes.

Morspeed

I'd be looking at taking it down with at least 220 and ideally 280 minimum before primer spray,you will probably find a heavy coat of spray putty first will fill the 80 grit scratches. Been watching your build, nice work, thinking about putting one on my list of things to do..

Gary

safariel

Just a quick thanks to Andrew for your help Cheers
Gary

stewie_wells

great looking model! just wondering if someone could please forward me the plans? i have tried the website but no luck. my emails address is [email protected]. thanks very much.