No Sylvain , this is only possible with the use of a female mould. In this case the gelcoat will be the first external layer.
Cheers
ClaudioD
I agree with you Row, the best is the silica also because is more effective in thickening the compound .
Was just a trial to confirm what you also says about micro ballons. Sure that it will not have the same thixotropic behaviour even I used similar quantity of product at about 5-6%.
Few hours from I will see.
It is not escluded to buy a clear epoxy gelcoat and add the red powder. The gelcoat can be made more viscous by adding 5 or 10% normal resin for easier stirring with red pigment before adding the catalizer.
Thanks about my back, but wet sanding is not really my cup of thea either !!! heheh
Cheers
ClaudioD
Here below the progress of my experimental work carried on this morning.
Since the pot with silica and µ ballons was abundant, I use also the female mould of my 5 years old CD65 (RG65)
Same pics with and without flash affects the color appearance. The real color may be in between !!!
Two pieces of wood are covered with (my) gelcoat containing 50% silica and 50 µballons and will be used to check eventual porosity or micro craters.
The gelcoat with 50%/50% was sufficiently viscous to fall from the vertical hull surface , not enought thixotropic but all my reserve of silica were finish !!
Tomorrow I will see the outcome after polymerisation. most importants aspects will be the appearance and the weight/dm²
Cheers
ClaudioD
Being too curious, 23 hours later I decided to remove the lamination from their supports just to see the other faces !!
First observation, in spite of 23 hour polymerisation time at 23°C, the laminations were still somewhat sticky as the polymerisation was not yet sufficiently completed ! The results are good but not as espected/desired !
Why ? I do not knows but I suspect two possibilities :
1 - the additions of additives may requires longer polymerisation times !
2 - because the additional weight added initially to the resin, requires proportionally more catalyser !
below the results :
a) The panel with colloidal silica presents a definitive more shining surface why the panel with mix of silica and µ ballons is dull and opaque, as visible with the neon lamp reflected onto the surface !.
b) the weight that was the important parameter, show that all part presents variations from 7.5g/dm² to 8.5g/dm², and this better then expected, while the heaviest being the panel with only colloidal silica, but observing closely this panel would be better with a little thicker gelcoat probably aftecting the weight up to 9g/dm².
c) with 9g/dm² the hull alone will be weighting around : 9 x 34dm² = 306g , including 3 layers of glass 80g/m²
Next trial will be with the transparent gelcoat but I need to procuring it !
ClaudioD
New test with 2 types of resins.
Two samples with reduced %of silica and without silica
including reduced pigment at 1.5%
3 layers of glass 105g/m²
My supplier suggested to increase the temperature.
ClaudioD
I have not tried to make a colored resin for a top coat, but have used West 423 graphite powder and silica to make a “tooling” resin for mold making. This is brushed onto a plug, usually 2-3 thin coats, and a torch lightly passed over the surface to pop the tiny bubbles that are induced during mixing. I always mix the resin and hardener first, and add the colorant and thickener afterwards. There are videos out there by some of the guys from the rcgroups.com composites forums.
After the tooling coat has set up for a few hours, I applied several layers of light FG cloth, then build up the mold with heavier weaves. This is to prevent the heavier cloth from “printing” through to the mold surface. When doing layups in a mold, my understanding is that the entire layup should cure for several days while still inside the mold to help reduce the print through.
If the Gelcoat is not too thick, it can be sprayed onto the surface, but since the layer is pretty thin, you may need to spray several coats. I have sprayed polyester gel coat onto surfaces, but you have to wetsand and polish to get a nice finish. I have also sprayed epoxy onto wooden centerboards with great results. Smooth, thin coats with no sags or runs.
Another technique is to spray paint inside the mold, preferably a two part automotive type paint (polyurethane). Then do the epoxy/cloth layup over the cured paint. Your finish will be as glossy as your mold is, either way you go.
Thanks hew565
Most of what you says I done it already several times, the point is that I want a colored gelcoat as first coat for the hull model.
Why that ?
With gelcoat is avoided having small craters induced by the tissue waiving and there is no need for paint at the end.
With gelcoat can be achieved a “very smooth” surface if the female mould is “perfect”.
i.e. According to my reading about “rugosity” a car body paint is around 5microns, with the gelcoat it can be achieved up to 1micron. Of course care shall be taken all the times by carefull cleaning !
I suppose that with such a lower rugosity , the hull shall have less drag !
Your idea of spraying paint inside the mould over a waxed surface, may not work because of low thixotropic characteristics and expecially with polyurethane components.
Most of the WAX manufacturers have written on their Data Sheet about the uncompatibility of their waxes with polyurethane products, few manufacturers are actually offering special waxes to overcome the well knone problems the 15% of moulds are sticking !
About my experiments :
the Surf Clear epoxy resin give a very good results without the addition of silica. The lamination was done on a piece of windows glass and of course obtaining a very good finish. With back light are still visibles by trasparency the tissue weaving .
The silica densifier produce lesser brilliant results.
The question now for my supplier is about the availability of a transparent gelcoat based upon the Surfclear epoxy resin.
The last pics of today
It is common for the airplane guys to paint in the mold, and over waxed mylar. There are many different waxes, and other release methods, like PVA and semi permanent releases like Freecote. Some paints work well, some don’t.
http://www.rcgroups.com/composites-fabrication-210/
ask specific questions there and several guys who make their living, molding model parts, will do their best to help out.
Thanks
cheers
ClaudioD
Claudio,
May I suggest an alternative?
Please could you mix the resin and hardener together first. As you would normally. Allow to stand for a few minutes to help the chemicals to bind together.Only then add the pigment.
If you are discovering that the mix is not curing still, the only solution to reduce the amount of pigment as this is inhibiting the reaction in some way.
My experience only comes from tinting resins and adhesives black. (very useful inside a black carbon hull)
I have used various products over the years, but the system that works best is always the recommended pigment from the same manufacturer of the resin.
I’m not saying that other ways are bad, just the quality expectations that we have nowadays, rule out the use of experimentation. Which for me, helps achieve a uniform overall finish.
I hope this moves you closer to a result!
Hi Jim
thank you for the advice.
Actually the results without silica are very good.
With the sample including silica has been exposed to higher temperature and the polymerisation was also good.
The poor polymerisation obtained was very probably due to excess of silica.
No problems with 3% pigment that is the low side of the reccomended ranges. 3% to 9%
Now I would like to try the thixotropic epoxy resin before repeating with transparent gelcoat at the condition that the transparency is as good as the Surfclear resin.
Cheers
ClaudioD
I have had zero problems with silica inhibiting the resin cure, in fact quite the opposite!
My bet is still on the pigment.
The only potential problem with silica in the matrix is that it may become very brittle and perhaps craze easily.
We also have problems with silica mixes going “milky” in high humidity…
Resin is often mixed with silica and used as a primer for the surface you are about to apply cloth to. After 6-12 months, you can see the areas that the primer mix was applied to as it shows up as a white-ish border.
To avoid this we use a Rubber toughened resin or a thixotropic to prime… should work equally well as a Gel coat.
It looks like your on the right track!
Hi Claudio, Conditions have not improved for laminating my mould and still working suitable solution …but I have not been idle :rolleyes:
I’ve now finished 3 moulds for 2012 season:
- NZL-20
- LE DEFI 2002
- BLACKMAGIC 95
All three hulls are completely have different water plans, bows & sterns and I’m interested to see the difference between on the water, have ordered sails, keel fins which will make all boats similar, only difference will be hull design.
Planning to try and have all 3 in the water for testing in March 2012 (3 months)
Cheers Alan
Hi K1W120, best compliments for very good work !! Im admiring !!
Bye, GINO
Alan,
I do not knows what to says , splendid work and extremely fast and beautifull collection !!!
I’m getting jealous of you !! hehehe !!
While myself I’m still stiring my mind with the cadmium and gelcoat that by the way is arrived yesterday.
Today was little busy as you knows.
The Le Defi form is intriguing my mind !!
You made 3 masters and my self still with one the NZL-20
Let go on !!!
Ciao
ClaudioD
Hi Claudio,
The most prolific r/c yacht designer on the planet - Congatulations!!!
just a quick question;
It would appear that each r/c design you have produced for the AC120 class is a near clone of the one prior. Do you use a basic design template and modify from it? As they all look so similar would it not, in the interests of the class be better to pursue a one design philosphy?
Sorry that was 2 questions
Tony
Hi Tony ,
each single design is very different in form and specifications from another.
You have also to consider that very few degrees of freedom exist from the AC120 class Rules that pretend a minimum
displacement of 4500g at the buoy and a maximum appendages weight FIN+BULB of 3000g
The remaining 1500g are needed for the RIG, Electronis , Rudder and Construction.
Fortunately the average models have still place in the built as such that often is obliged to add several gramms of ballast.
The Rules also requires to develop a model with very close look to the real corresponding ones.
Inside these limitations there is still room for the designer to satisfy the rules and also researching the best architectural compromise for what concern the typical design parameters like :
The Prismatic Coeficient
Wet Area
The Water Plan Area and form
The Water lines at entrance and exit of the water plan including at 30° tilt
The CB position
The CG position
The CF position
The FIN- RIG position
The Lead percentage
The Beam width
The Water Beam width
The LWL lenght
The appendages forms and volumes
The B/L ratio
The Curve of Areas
The Main immersed surface area
Etc.
All these parameters and the respect of the original real boat shape and the Rules, produce differents design issues.
All the hull shapes presented above by Alan are very differents each other, you may consults the related drawing presented and read the parameters associated with each.
Is true that one single design would solve a lot of design problems by introducing the Monotype Concept that until now was refused in spite of all the interpretations problems in the class that pretend to be almost free, but imposing a lot of restrictions including rigging.
My dream for an AC120 class evolution will be as it is done with US-12, EC-12, Canterbury J-Class, and others single design and changing only the decorations. The risk is anyhow that during a race you may find 3 Alinghi, 2 NewZealand, 4 Oracle, etc and this make the things more complicated. Not easy for the designer to pretend to copy the existed America Cup Boats while remaining insides the Rules.
Regarding the authorised models in the AC120 Class as well in the AC110 Class ,are the ones that partecipated to the America Cup from year 1995 up to 2007, are numerous and each modeler have a wide choice , obviously with Scale Volume Adaptations.
In real 1:20 scale of a 24tons boat, the modell should weight only 3kg but almost impossible to built and therefore the 4.5kg minimum is requested.
One of my lighter design AC120 Sport present in this forum is weighting 4.0kg
Sorry for the long reply
Cheers
ClaudioD
Hi Tony, There is still quite a bit of freedom within rule issue 1.5, albeit there are moves to try and restrict with rule changes, but it is not a point of discussion for this threat.
The attached list of IACC 120’s shows the scope variance in boat design currently available showing minimum and maximin specs being used.
As Claudio says the perfect yacht has yet to found and compromises are always present with the changing the weather conditions.
Cheers Alan
Finally managed to laminate the moulds, was bit of a risky exercise as it is snowing here and this means fire place goes on … :rolleyes: hmm me thinks !
Today also happens to be time for erecting the Xmas tree and family tradition is that this is the guys job and she who must be obeyed … goes shopping !
Think you’ve got the picture by now … 3 moulds laminated in the lounge by nice warm fire place, super spring clean to make sure there was no evidence, Xmas tree erected with blinking bits & pieces running and then little lady comes home & wonders why I feeling so happy (none the wiser about my crime of course) … It’s Christmas Honey !!! 
Thanks to my accomplices (two sons) great team work guys ! knowing full well I will blackmailed over Xmas to keep them quite. :scared:
Merry Christmas everyone :xmas:
Cheers Alan :zbeer:
Alan,
Many congratulations on the progress x 3 !! Shall definitely look forward to reading your observations of the on-water trials.
Like your idea for getting lamination done - no snow here, just temps hovering between 3 & 7 C with lots of rain. Unfortunately our household ‘finance director’ (she also does the compliance and auditing!!) recently suffered a ruptured appendix & is now home from hospital so I can’t get away with anything - bah humbug!! At least I think I’ll be earning serious brownie points for her Christmas present (hopefully not being over confidant) thus will earn the right to serious workshop time in the new year!!
Well, here’s wishing you and yours a fabulous christmas and that you get plenty of steering servos & sail winches in your christmas stocking!!
Regards,
Row