“SET SAILS” - my IACC120 building log

This picture started it all.

Surfing on the Internet for rechargeable batteries, I stumble on this picture that instantly hooked me. This was definitively the hobby I was seeking without knowing it even exists. Well, I had seen kiddy R/C sailboat before. But almost 2 meters from bulb to top of the sail, that was a big guy toy. Since I cannot sail my 1:1 catamaran as I use to, this could be a worthy salvation: still fighting with the wind and be around the water. I understand that it would never be like being on the water, but it seems to have its own merits.

I found out later that this was a “cheap” made in China effort that could be seaworthy with some mods, but that will never show great performance. Doing my research, I realise that if I have to change over time the rigging, the sails, the servos, etc… why don’t I simply build a complete boat!

From another angle, I was wondering how to get some competition to keep the fun factor over time. There is nothing much going on in R/C sailing around here. I have found plenty of sailor friends that are more than willing to try it, but no one wants to commit ($$$) or get involved in modding. I could broaden my search… or own more than one boat! So instead of buying two or more made-in-China boat, why not building them? It would be cheaper!

Well… not. I recently found out that it will cost me more, if not way more, per boat. That’s because I have since stumble on the RCsailing forum and its top-of-the-line-racing-sailing-boat… and on the greatest and generous community of enthusiasts that makes it live. I guess I could still built a cushy R/C sailboat out of a Styrofoam plug and a broom stick as a mast. But I have been bitten by the bugs… or more precisely by you guys, with your fancy racing boat and fascinating building tales.

This previous tread will inform you of the approach behind the IACC120 choice. No need to elaborate more. Great thanks to the contributors. http://www.rcsailing.net/forum1/showthread.php?6383-AC120-vs-AC100-vs-VOR70-first-try&p=61575#post61575

Thank you for your interest in this building.



I have downloaded from these sites all of ClaudioD’s IACC120 designs.


Since Canada produces better hockey players than racing sailboat, I have no affiliation to any nation in the America’s cup. In fact, I am not bias towards any of them, cheering for all of them. So purely by aestheticism, I initially picked two of them that suit my personal taste: the Alinghi SUI-100 and Fly Emirates NZL-92, with a very small incline to the first. But… it was etching me that the second has more complete drawings, like shadows with planking lines, deck lines and an elaborate build log from Alan.

Moreover, I could built a NZL-92 and decide to paint it as an Alinghi when time comes. OK, I fully understand that most of the purists out there are now thinking that I am a crazy nut. And I won’t blame them as I would be questioning the sanity of someone building a F1 Ferrari and painting it as a McLaren. Please bear with me, I’m just trying to get this project moving.

So a NZL-92 it is (NZL-92-B in fact, according to ClaudioD’s plan). And in fact, maybe I could do the Phoenix paint scheme that I like so much! Well, I have time to think it over.

Claudio, Alan and all the others, thank you so much for sharing your passion.



And now to start the discussion…

Starting from Claudio’s PDF drawings, I am still debating if I should use wider or narrower leveling legs on the shadows. Adding some extra width in order to get a nice support edge for the first bottom plank seems like a good idea. Not too much though so that the glass layer of the male plug could drop loosely without interference. I would have to remember to mask these edges [EDIT mask the leg edge witdh were the stringers and the first plank will meet the leg] before gluing the planks for an easy cutting/releasing later on.

The narrower option will needs some extra care while positioning the first plank but it leaves a nice edge with enough depth to run the knife that will cut the plug glass layer at the deck line. And of course, the cutting of the shadows would then also be less tedious.

Maybe I am trying to cut hairs in four here, but since I have no experience in R/C boat building (moreover in racing beast), I don’t know yet where we must be careful, were to run thigh or loose tolerances and how much time will take all of these steps.

The white space below the reversed shadows is there on purpose. This leveled off cut represents the female shadow that will be used later on to provide a jig for the gluing of the balsa deck line. I figured this will be a time saver doing both cut at the same time (one at the continuous line for the male shadows, one at the dotted line for the female). I still have to figure which female shadows will be later needed. Maybe 12-8-5-4-3-1-0 are enough. Or maybe this is too much. Any thoughts?



You seem to know more than you think! You are making a wise choice in boats as these boats re beautiful and sail great. You are on the right track in your thinking…

This forum and the other links you mentioned will provide you with any and all info you might need.

Good luck!


If I were doing it again, I would go with the narrow legs. With carefull cutting of the shadows, glueing in the stringers will be easy. The eventual trimming of the deck line and then putting in the deckline balsa will give you plenty of time and opportunity to fix little mistakes.

What do you mean “mask these edges” ? In either case you have drawn there will probably be no need to cut the legs back. I had to as I had the legs right out as in Alan’s initial build.

For the female shadows, I figured 4,5,6 were important then had 10 , 8 and 2 I think. The more the merrier!


Hi Sylvain,
the shadows do have a small overhang step just to support the deck line strip. See this page about the build log of the last 43-900.

Actually the design of Alinghi SUI-100, Areva FRA-93 and ETNZ 92 as well the NZL32 of Alan are the ones wich exibit very good performances. Nothing forbid to decorate the models as you like, see the Jaguar of Alan son that received a prize in Italy as the best decorated model.
Areva is winner of the Italian Championship Cup 2011, last year was 3rd and twice the winner of the regional selection.

Seriously is one of the best models to build. Very fast and nice looking. As an M design sailor and AC120 designer, I will not esitate to build one myself.

The costs for the first model according to my records are :

186 € for master and female mold
163 € for full model construction without electronics
201€ for the following models since the mold is available
180€ for the RC equipments including servos , Rx, Battery pack and trasmitter.


Brian, thank you for your pep talk!

Grav, I have edited my post for more clarity about the masking. But you got me right and I will think about your valuable suggestions, from a guy who have been there :). You made me realise that I may never have to cut the shadows.

Claudio, it is an honour to have you here. Merci. You are right, your shadow drawings already have a small overhang step for the deck line. I have played so much with them that I had forgot my starting point. Sorry about this. Now that I recall, what I didn’t like about them was the fact that I couldn’t glass the plug as it is… the overhang steps being in the way. The proposed new width will support completely the stringers and only half of the first deck line strip. By the way, why do you take the time to cut a hollow at the center of the legs? You are certainly not thinking about weight budget at this stage. Is it for convenience when it’s time to lay epoxy inside the plug?

At least for now, I don’t intend to proceed with a female mold. A male plug will be enough to make my first steps in R/C sailing modeling. From there, I will have to decide if I build two boats at the same time or just one up to the madden voyage. It seems logical to make all my mistakes on a first boat, but I will then be frustrated to be alone on the water for a long time. Since the fun discovery part won’t be there to drive my patience, the second one could end up too butchy. I know me. With two boats on the water, I could then serenely build some more if there are takers around me and I still have the drive. i guess I have just answered my dilema :rolleyes:.

I have been a good apprentice studying all the building threads and your cost estimation doesn’t come as a surprise. I am glad to have a confirmation though. It seems way too much for my pocket at first, especially for two boats, but I figured that this will be spread over time. So it’s still a go… what am I doing!!!

A hollow in the centre of the shadows? It helps with clamping the strip planks on. I went to the dollar store and got a pile of small clamps.


Not in the shadows, in the legs below the shadows that level them. There is none in my drawing since I removed them. Maybe my hollow term in not the proper one. A square cut could more appropriate.

Easier to cut off ? :slight_smile:

Hi Sylvain,

Any of Claudio designs will work perfectly well, just a matter for personal preference on hull shape and … decoration open to the imagination, how about having Canadian flavor ?

As you thinking about mould preparation at this stage, I throw my two cents into the ring.

Most important thing for me is the building board 1) it will be used for the mould and laminating and 2) use the same building board for cradle of the hull, for the hull fit out.

I make 3 sets of shadows:

1st set - Used for stringers planking etc, personally I like to cut the base board about 5 mm narrower than the mould, and cut the shadows on angle then there are no problems sanding (block catching frames) and you have more access around the sheer line for lamination, then when hull is curing (green) just run knife along the sheer line for clean cut, before the lamination fully cures.

2nd set – Female shadows to firstly check the hull shape when sanding the mould and then after lamination use them in the same base board as cradle, I use every second one (full set not really required)

3rd set – Male shadows inside the laminated hull to keep hull in correct shape and use as measurement and positioning reference when fitting hull-out

I also go to the trouble of cutting slot into the building board where the keel fin goes just to check levels & angles etc.

You mentioned laying-up epoxy inside the mould, with the shadows I can tell you it is pain where the sun don’t shine cutting fibre and then wetting it in the mould between the shadows, honestly just mix up good quantity of epoxy and just brush it inside the mould, no need to lay-up glass fibre.

For my first experience I pulled two hull laminations of the same mould, the mistake I made was assembling both hulls at the same time, with hindsight I would only assemble one hull first & then test sail it, then make assembly the second hull after learning from the mistakes I made in the first.

Just a thought, have you considered using foam for the mould ? Claudio has proven it is lot quicker (and cheaper) for AC hull form and using packing tape as release, you should be able to pull at least two hulls off it, if not more !

Looking forward to seeing you reach your ambition of having fun sailing with your buddies, it’s damn good fun :cool:

Cheers Alan

in my case the shadows has been cut after removal from the standing support to prepare for sanding and female moulding, you can also see here and in further pages , while the work of Alan is perfect : http://www.rcsailing.net/forum1/showthread.php?5879-Ac100/page3

Lots of good tip Alan. I am sure a good start will facilitate my journey. This is why I put so much attention into it before the fun begins. Thank you for your valuable insights.

I had noticed the difference of style between Claudio and you, where you seem to approach this hobby like an engineer (cradle, mock-up of sub section of the hull, water test, etc…) as oppose to Claudio who reminds me of a master/craftsman/artist who likes to free the mould as soon as he can from the base board and then work in “open air”, probably to feel it in his hands, weighting its curves through his thumbs, probably seeing it cutting a wave (I kinda romanticing it). I hope there is no offence taken here as I truly admire both of your approach equally. Being an analytical engineer by day and a “not-so-successful” artist by night, I guess I will have to find my own style in this. To be true, I have been torn in the past two weeks by your two approaches.

A Canadian flavor? Here is a little story with a kiwi turn. My youth dreams on the open seas have been enriched by a visit on the Formula Tag maxi catamaran, with its Canadian skipper Mike Birch (Quebec-St.Malo Transat, 1984). After some great winning (first Route du Rhum, among others), the boat was pass along to Peter Blake and became “Enza New Zealand”. He won with it the “Jules Verne Trophy” for the fastest ever circumnavigation of the world under sail in 1994. The Enza had pretty dull colors in today’s standards, at least to my eyes, but the Formula Tag are… well… not too bad. I’ll think about it.

> then when hull is curing (green) just run knife along the sheer line for clean cut, before the lamination fully cures.

Can you give me a time estimate?

The foam technique seems appealing, I agree. But it eludes me how someone can succeed to achieve a symmetrical and smooth hull with it (natural curve, not steps). A veteran hobbyist may develop over time a natural sense of the hull shape and some hand sanding skills that will go beyond following printed shadows glued to the foam. And besides, I guess you still need some kind of cradle to properly glue the balsa stripe inside the deck line of the hull.

:slight_smile: Well Claudio is Italian by birth, hence his very artistic & creative approach with his hands & me being a Kiwi living & working in Germany, I can’t use anything else but an engineers approach, but with my Kiwi K.I.S.S principles and a piece of number 8 wire is always in my back pocket for those quick Kiwi fixes :stuck_out_tongue:

Curing times depend on the specific resin your using, but the Kiwi rule of thumb is, when you can only just dent the surface with your finger nail, it’s good to trim with the hull on the mould (don’t lift hull off the mould)

Claudio hands should tell you about foam, I have not tried it yet, but you still need to have shadows on base board which you use as guide to shape the hull and the secret is in the elbow motion and how you hold your tongue between your teeth as you sand :lol: right Claudio ?

When I cut my shear line, the shadows were in the way, and my cut was not great. I think I cut it about 8 hours in. Yes it is easier when it is green, but still possible fully cured.

Then when glueing in my gunwhales, a little sandpaper on a stick allowed me to clean up the shear line perfectly.

You will get practice when you glass the plug, so no worries.


Sylvain -

regarding Canadian Flavor - somewhere (probably at home) I have photos of a Canadian decorated boat. Will see if I can find and post. In the meantime, here is “Arcelor” in 1:10 scale and with some beautiful workmanship in details. (no - not mine…but I wish)


Wow, you now have my attention Dick! Even though I have just committed myself to a pair of America’s Cup design, for multiple good reasons that I don’t regret, I still have in my heart the secret desire to build an Open60&70 someday. VOR, Vendée Globe, you name it. And even if it makes it a lesser racer, I would like to include all the deck details like we see on the dashing replica in your picture.

Mike, you just confirmed my apprehension about the shadows too-wide-wings. I will take this into account.

you may take a look at this post taken a couple of years ago : http://www.rcsailing.net/forum1/showthread.php?4991-IACC120Cup/page11&highlight=ac33
Yes some time I need a lot of elbow exercize expecially when I make the wrong choice. The sanding aspect requires practice . Alan indeed !
In term of design details, most come from may ex professional occupation as research engineer and Quality manager on satellite programmes.
The AC33 is one of various research works as well the 43-900 !
One AC120 design will be a technical good choice !

Sylvain – I found the “Canadian Flavor” photos.

Here is a series I found some time ago - with the same intent - “…to heck with racing - I want a scale boat !”

Anyway, maybe these can be used in the future. In the meantime - good luck with the AC boat build.


Hi Sylvain,

Thought I’d also pass on a few ideas that I’ve picked up from the overly generous postings of Claudio, Alan, Dick and many others.

Like you, I’m also new to this hobby having recently had to give up ‘big boat’ stuff. I note from your earlier posts that cost is going to be a fairly heavy consideration and thought I’d throw in a couple of ideas that may help.

First of all, planking. I get the impression that quite a few of the contributors to this forum and others either buy planking already sized or use balsa sheets which can be easily reduced to planking using homemade plank splitters. I don’t know what you have in the way of workshop tools or whether you have friends / aquaintances / work colleagues who have either a bandsaw or tablesaw, but a much cheaper way of getting planks is to purchase / acquire a straight grained & knot free larger bulk of timber and cut your own. When I started my J Class ‘Enterprise’ (another from Claudio’s ‘stable’ I cut my own planks on a band saw, the total cost (with plenty of spare planks) being less than £10.00 sterling (approx $15 canadian)

Second thing is laminating. I think Alan mentioned in an earlier post that it may be necessary to scrap the first hull you mold. That can certainly be a heart wrenching decision for anyone, but all the more so when you’re watching the pennies. Needless to say, there’s nothing in the rules to say you have to use epoxy - wherever you get it from it’s pretty expensive stuff. You could consider using polyester resin for your first experiments with laminating. For starters, it’s less than 25% of the cost of epoxy. Sure, it’s not as strong / flexible, but it’s certainly up to the job of an AC120 hull. Also, if things do go horribly wrong (highly unlikely as things can usually be rescued) you’re not thinking of the dollars in the garbage. Moreover, while it’s always nice to produce a competitive boat, if the initial intention is to learn the ropes so to speak with this build and then the subsequent sailing, money can be saved with fibreglass cloth selection. The savings aren’t so great here, but from your research you’ve probably realised that the weights of woven cloths generally used (50, 80, 100 gram per square metre for example) are fairly expensive per sq metre. As an example, from a couple of UK suppliers I’ve just checked, 108gsm glass cloth is £7.00 / sqm ($11.00 Canadian). Compare this with 160gsm cloth at £4.00/ sqm ($6.40 Canadian) and you can see where further funds can be saved.

Above all, remember that this hobby is fun (can also be frustrating) and that some of the larger costs involved are quite a way off hence will give you plenty of time to save. In the meantime, take your time and enjoy every step. The advice and instruction from the contributors here is phenomenal - without it I’d probably still be scratching my head & staring at drawings. There will be times when you can’t see a way around a problem - fear not and ask on these forum, however stupid you may think it is - we were all beginners once (I still am) - because if you experience a particular difficulty which hasn’t cropped up in one of the previous build logs, someone else almost certainly will in the future and you’ll be thanked for raising it…

Hope that little lot gives you some more positive reinforcement,

Good luck & regards,