Mani thanks to Twister and Claudio, now i know ENZA ! bye GINO
Hi Claudio,
Are there any benefits with using the 49 gsm cloth over the 80 - or is it that you’ve run out of the ‘heavier’ cloth?
Regards,
Row
Hi Row,
yes beacause the tissue have finer weaving or yarns.
This will facilitate the next sanding by using finer grade sanding paper and therefore obtaining a very smooth finish. The final grade will be 1200 paper.
Why two layers instead of one ?
-
Simply because during the wet sanding the first layer may be removed partially or totally.
The remaning layer will still separate the white under coat and therefore reducing the risks of chemical uncompatibility and running the risk of “sticking mould” during construction. -
Why female mould this time ?
-
Since the constructional margins for the AC120 are rather confortables, I decided, for this construction, to use the Gelcoat as external layer for the hull . To do that it is necessary a female mould.
It is also known that most of the time the gelcoat is not used in order to gain weight.
In a model of this size, a Gelcoat layer may be in the order of 250g. The gelcoat can be also pigmented with the color you need and therefore no use for further painting. The Gelcoat offer a very smooth and brilliant finish better then a painted surface if the mould is carefully done.
Sorry for the lenght, but I hope it is clear for you why I make above choices.
Cheers
Claudio
Hi Claudio, last few days we’ve had 100% R.H with heavy fog throughout the whole day so I have not been game to laminate until conditions improve … will update when things improve & and I catch-up 
Cheers Alan
Claudio,
Many thanks for your reply - the 49 gsm cloth makes perfect sense. I recall when I was doing the Enterprise plug the glassing was with 160 gsm and it took additional coats of epoxy to fill the weave properly. I guess the finer weave of the 49 means not having any weave to fill which results in slightly easier sanding.
I hadn’t realised that you were going down the route of a female mold and my only experience of gelcoated hulls is with big boats. Does the thinness of the laminate coupled with a gel coat result in a finish that would crack and/or craze more readily if involved in a collision? Reason for asking is that I remember racing 1/2 & 1 tonners back in the late 80’s and start line skirmishes invariable resulted in cracked / star crazed gelcoats - the hull laminates were incredibly thin and lightweight & I suppose they weren’t really built with longevity in mind!!
Regards,
Row
Alan,
Pain about your local weather conditions - is your garage/workshop sealed well enough from the elements to warrant running a de-humidifier?
Other than that, get well soon & happy building!
Row
Alan don’t rush !!! You have plenty of times. Better to take care first.
I ordered the molding Gelcoat, but not yet the red color one since not easy to find the right color.
Actually I’v been told that is better to use a colorless epoxy gelcoat and adds some pouwder colors.
Testing are need to find the correct proportions powder/resin. The expert is suggesting to prepare a resin mix in separated pot and let it 24 hrs to stabilize the pigments before mixing the preparation with the final resin/hardener.
The definitive choice of pigments are not yet clear, waiting for an advice from expert. This is the Red Color I wish to use : http://www.materiaux-naturels.fr/fiche-291/pigment-rouge-sf-.html.
This of course will imply that if successfull, no need of paints at all . Average colored gelcoat weight is about 500g/m² according to boat manufacturer, therefore the NZL-20 will requires some 500g x 0.36m² = 180g of gelcoat.
Cheers and take care !
ClaudioD
There lays my problem, no it’s not sealed from the elements, keep telling myself to get around to it next summer but sailing gets in the way 
but I will find one way or another of over coming this small challenge.
If your going for female mould Claudio I will have plenty of time to catch-up & it will interesting to see the difference in hull weights & finish vs latex application.
Cheers Alan
Hi Alan,
according to my rough extimation the hull with the gelcoat should be :
Hull surface ~34dm² extimated from the master under construction (need confirmation)
3 x glass tissue 85g/m²
epoxy resin = tissue weight
average gelcoat 500g/m²
(3 x 0.85) x 2 + (500 x 0.34) = 343g (expected anyhow below 350g)
To remain on the subject this is the “expected weight budget” in grams
Hull…343
Deck…100
Supports…100
Whinch…65
Servo…30
Rx…12
Battery…100
Rig A…310
Rudder…35
Fin+Bulb…3000
Ballast…150
Total …4245
Rules…4500
margin …255 sufficient to control the “unknown” like Gelcoat, ServoArm and other supports .
Cheers
ClaudioD
The last lamination is 2 days old and assumed to be ready for sanding.
NZL-20 is changing color for a while the time of final wet sanding before wax, btw this color will be the final one. Was just to see what will be !
ClaudioD
As always, your step by step description and commented pictures are really helpful. I am glad you choose the female mould approach. It gives us the opportunity to appreciate this other possibility.
If I may, I would like to formulate a wish at this stage of the build: to keep this pace at a later stage. Thanks to you (threads and booklets) and a few other contributors, the hull making, appendages, bulb and even sails are now well documented. But there is a lot less on little parts like the mast spreaders, stay making, boom & boomvang, anchorage, fittings and also on the deck making (design, computer print or cardboard model(?), trap doors, closing the hull) and the tweeking at the water plan.
I am not talking about the drawings which are plentiful, but their step by step realization, technique and tips. Just a thought, of course, there is no obligation from your part.
Love it !!! :love:
Sylvain you are faster then Alan !!! heheh !!
The time will arrive also for these details, meanwhile you may consults the others treads availables in this forum about the AC120 and AC100
Cheers
ClaudioD
I only wish. My posts are either done during pauses at work or between diaper changes or other young kids duties. In the past two weeks I only found time to print, scissors cut and glue the frame layouts on my shadow boards. I’ll be alone at home next Thursday night so I may be finally able to play with some power tools :).
I guess this gives me lots of (too much) time to think about the steps ahead 
. I promise I’ll be patient:rolleyes:. It was only presented as a suggestion for a more detailed coverage of the little steps lying ahead, the ones that usually get less visibility (see the list in my previous post). No blame here though, I am sure that I will take the same pitfall on my thread when the excitement of the coming madden day will kick-in. I guess I just want to let you know that your efforts are not useless. That there is at least one apprentice who will read eagerly everything you have to say about access doors, stay material, shaft sealing, painting or the like.
That all sounds very familiar. I’ll sneak off to the workshop only to be interrupted 5 minutes later with a little voice calling ‘Da-deee…’. Bless 'em!!
For additional info on build tecniques etc it’s worth reading through the following:
http://www.rcsailing.net/forum1/showthread.php?5335-ETNZ-IACC120-Dual-build-thread
It’s Alan & Goose’s AC120 build with Claudio ‘instructing’. Plenty of very useful info that applies to many different designs. Happy reading!!
Regards,
Row
That all sounds very familiar. I’ll sneak off to the workshop only to be interrupted 5 minutes later with a little voice calling ‘Da-deee…’. Bless 'em!!
For additional info on build tecniques etc it’s worth reading through the following:
http://www.rcsailing.net/forum1/showthread.php?5335-ETNZ-IACC120-Dual-build-thread
It’s Alan & Goose’s AC120 build with Claudio ‘instructing’. Plenty of very useful info that applies to many different designs. Happy reading!!
Regards,
Row
edit: Seem to be all fingers & thumbs today, so apologies for this post appearing twice!
In principle I should go out for the final wet sanding, but before was raining anf now I got back pain !!!
The NZL-20 hull will be RED of course, but this time the color will be obtained with the gelcoat !!!.
Almost impossible to find Red colored Epoxy gelcoat unless ready to buy 300kg.
So I decided to make it myself for the first time in my life. I will succed ? who knows , but ready to describe steps by step what I will do.
1st operation : purchased the basic product for 21€ a pot of 120g of Cadmium Red Light natural powder as depicted.
Not all pigments are compatible with epoxy resins , the natural powder (not artificial/chemical powder) are the best for this application, This is what the composites specialists told me.
Before starting gelcoat preparation, may be interesting to read about addition of pigments a fillers.
All these info and many more can be found here :
http://www.westsystem.com/ss/techniques-materials/
ClaudioD
Two samples prepared around 20g of epoxy resin each.
The 1st contains 1g (5%) of cadmium powder and after mixing I added 4 theaspoons of colloidal silica. The appearance is rather thick compound and will presents probably too high thixotropic characteristics.
The 2nd contain 2g (10%) of cadmium powder and after mixing I added 1 soupspoon of µ ballons. The mix is still presenting higher viscosity compared with the 1st.
Booth samples have been mixed and stirred with my set-up mini drill powered with low DC voltage , ~2.5V.
The sample will rest until tomorrow when I will add 55% of catalizer followed by stirring and brush on 60° tilted plastic support
ClaudioD
PS : Forgot to tell that after adding the cataliser, will be necessary to adjust the additive ratio.
The red color looks imperial. Very nice.
I understand that you want to color your gelcoat. But could this technique be use with regular lamination over a male plug? I mean, with the fiber absorbing the resine and the red pigment, will we get a nice and even color after wet sanding? Maybe something to try.
Claudio,
I’m sure Jim (Astute Composites) can give a definitive answer, but I’m sure I’ve read somewhere cautioning the use of microballoons as a gelcoat thickener. If my memory serves me well (doesn’t happen very often!!) I’m pretty sure the general consensus was that it wasn’t a particularly good idea because if it’s necessary to polish/wet sand the finish you may end up with a ‘pin hole’ texture. It had something to do with the hollow nature of m-balloons and that when polished/sanded effectively ‘opened up’ the glass spheres.
As I said, could be wrong & I’d certainly want to check it with Jim. Other than that, great progress and definitely looking forward to your ‘tutorials’ on gelcoat application!
Read that WEST article and was amazed that some pigments actually improved adhesion with virtually no impact on hardness - I think the term was ‘statistically insignificant’. Obviously their trials were with the 105/206 resin/hardener combination but I don’t suppose there’s any reason to think they’d behave any differently with any other ‘consumer grade’ epoxies.
You have my sympathies for the back pain & I hope it’s a short lived issue - I know only too well what it’s like being prevented from doing what we enjoy because of it, so get well soon…
Regards,
Row