AC 120 Building Workshop

Hi Guys,

Last weekend I started workshop in Munich (Germany) with two people on how to build AC 120’s

Both Jorg & Gregory are experienced skippers of IOM, M-Class & 10 Raters and found the AC 120 to be exciting to sail and quick arrangement was made to build two boats using my exiting male moulds.

Hulls were laid-up over last weekend using latex method for 1) ETNZ-92 and 2) Blackmagic NZL-32 with follow-up workshops planned for completion of fit-out, rigging in hope to have both boats ready for Italian championship later this year :slight_smile:

The Central European AC 120 fleet is growing and anyone wishing to join or start another workshop are most welcome, no costs involved just pay for your own materials.

Updates on this project will be posted from time-to-time.

Cheers Alan

Great work Alan!

Looks like you have wasted no time getting stuck in and maximising your retirement.

Good luck with the new boats,


Fantastic work Alan!
You are a very very fine boats maker!
Wellcome on board for the two new 120 skipper!



I know this has probably been covered before, but, what was your lay-up schedule for the hulls? I thought the latex method required that the latex get pulled over the mold, but it looks like here it is only draped on? or is it stapled underneath?



Hi Todd,

There is a thread on subject you can read detail [u]here[/u]

In short lay-up schedule was 2 x 245 gsm Carbon twill @ 45 degrees, wet-out first layer on plastic sheet & then draped over mould, lay second layer over wetted first layer and wet-out on the mould.

Run extra line of epoxy along the keel line for maximum saturation & then drape Latex over the lamination and roll-out large air pockets.

With light even tension, stretch Latex down to base board and staple & the roll smaller air bubbles & surplus epoxy out from underneath the Latex (in direction of weave) over the edge of the sheer line.

Cheers Alan


Thanx for the link to your building methods. About how many grams do your hulls weigh?


Hi Todd,

2 x 245 gsm Carbon hulls generally weigh-in around 300 grams, final finished boats are 2-300 grams under weight ready to sail, so there is good amount of movable ballast available to balance the boat when I start tuning.

For fit-out I’m using carbon foam sandwich which saves considerable amount of weight and provides very good strength, using heavy materials gobbles up weight pretty quickly.

For those interested in following the build of these two boats you can follow the threat [u]here,[/u] it’s in German so switch on your translator :rolleyes:

For the first hull we used Natural Latex (0.40 mm) that has excellent elasticity, it unfortunately split and for second hull used a Synthetic Latex that had not as much elasticity (felt stiff) and it was difficult to get it to lay smoothly

Cheers Alan

Hi Alan

I’m having trouble finding a supplier of latex down here in New Zealand.Are you able to give me a link to a supplier? looking forward to following this build thread

Cheers Steve


I’m not too far away from you, in Melbourne, and found a supplier close by who sells it on-line by the meter:

They probably won’t believe you when you claim to be using it to make a rc boat ;).


Hi Jim

Thank you I bet they hear all :stuck_out_tongue: sorts of reasons for buying the stuff
I was going to build a female mold but latex looks a better way to go
Cheers Steve

Gidday Steve & welcome to the AC 120 club, the latex supplier was using here has gone belly-up, if you have trouble finding it down under let me know & I’ll find another supplier, the guys in Munich are looking around.

Which hull are you starting with ? I’ve found the male mould option is good fast start however if your wanting to start a fleet pays to think about possibly going to female if you want reproductions later on.

Will be following your progress in land of the Long White Cloud & helping where I can.

Cheers Alan

Hi Steve,
this is the address I used to get some free samples :
Four D Rubber CO LTD - Heanor Derbyshire England
Email : and Web :
Alan is more expert in the matter and may suggest the best thickness. Personally I would stay in the range 0.4/0.5mm
The natural rubber grade S is probably what you need see data sheet :

Spot on with the thickness Claudio, from my experience the natural rubber is the best, the synthetic version is not so good to work with.

Wish to share few pics about issues with latex tension, this hull the owner wanted to have a carbon optical finish so the weave needed to be straight, once you put latex tension on the wetted out carbon do-not let the tension off otherwise the latex will creep the carbon where tension is eased and it will look like this…

If you are painting the hull, naturally the weave pattern does not matter.

With this next hull I had the latex split at the stern (caused by small splitter) I panicked and tried to recover it by increasing tension horizontally along the keel line, but it only made the problem worse by having too much tension along the stern quarter freeboard which made the carbon creep again.

This hull was binned, but in hind sight I should have taken the latex off the wet lamination and continued with normal hand lamination (with lots of sanding later) as it would have at least saved the carbon material :rolleyes:

Cheers Alan

Is the latex a one-time use thing? I found a place in Canada to buy it but it’s $15 a yd. If I could get more than one use out of it might be worthwhile. I can sand quite a bit for $15. Yes, I am cheap.

You’d be a cheap date Don ! A Mac for dinner then straight into the latex uh :wink: it can be re-used if you handle it carefully after taking it off (the mould) staple removal & has tendency to want to stick to itself (don’t let it bunch up straight off the mould) giving it sprinkle of talcum powder helps brings it back to original condition again.

Of course you can use both sides (2 hulls) if you don’t plan re-using it again, but don’t try this with your pocket latex Don, could end up with more than you bargained for :stuck_out_tongue:

Cheers Alan

This was our 3rd workshop weekend in Munich, progress has been good with Jorg making great work with his Blackmagic construction and Grigorios has not had a much time, so spent most time bringing his ETNZ up-to-date, further details should be posted on the German site soon.

The team is having a lot of fun & now we have CNC machine available :shades: Jorg is experimenting making fins.

You lucky so & so !! How on earth have you managed to get your grubby mitts on that?


You won’t believe this :what: the company the guys work for provide a dedicated modelling workshop and all the equipment they need for their employee’s … only thing missing is VAC gear, but most are building aircraft and don’t need one … :roll: yet !

Tell you what, if I was working there you know where you could find me almost any time of the day !!!

I’m vaguely familiar with employment law and I’m pretty sure I’ve never come across anything regarding provision of CNC machines or potential Vac systems as ‘employee benefits’…

Gone wrong somewhere!!


Yes, we don´t believe it and you shouldn’t as well. It was a joke or at least a misunterstanding. All equipment and each and everything is bought from our own means, nothing from a company (But our bosses also read the Internet, and this could bring us into a lot of trouble, so please stop this subject now).

cheers, Jo