the pictures gallery continue …
Claudio
On previous picture the deflection under 1500g weight was too high, therefore I took the decision to adds 3 layers of Unidirectional carbon tissue of 85g/m². The result was excellent !! the weight was increased to 1750g instead of 1500g.
The Rudder is inside the specification to .
Actually I’ m thinking about a new Fin , wider and shorter and of different shape : the pictures are added.
The upper Fin shape inside the trapezoidal trunk will allow a sliding adjustment of about 5mm. The trapezoidal shape is lighter
The reasons of this ‘new’ design are severals : wider fin will allow better ‘close hauled’, allow a realative thinner profile. the resistance during ‘running’ will be lower In order to keep the wet surface low, the fin is shorter only by 1.5 cm,
End of Fin & Rudder Gallery for the time being.
Cheers
Claudio
Avant- Première !!! before continuing describing the Build Log that started 51 days ago.
Not finish yet, missing final painting.
Cheers
Claudio
Is time to show the plans of the AC100-B as depicted above.
Cheers
Claudio
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Let’ start from the beginning ! After the successful AC120 , this time some peoples ask for a small and transportable boat.
It was the June 11, 2010
As usual, I will presents a lot of pictures to show the progress step by step .
Cheers
Claudio
next 6 pics for today !
In particular the main boom is just a strip of balsa, 5mm thick, laminated with 2 layers of carbon tissue
CD
Thr hull is almost completed .
The strips used are samba/obeche of 3x5mm and the shadows are made out of ordinary plywood of 5mm - the glue is UHU Plus Hart the clamps are visibles !
6 days later from the start, the hull is removed from the support, the shadows are rectified and the interior is coated with epoxy in order to gain in rigidity before starting the external sanding.
The internal coating is of paramount importance with soft wood as balsa.
Cheers
Claudio
the images are referring to the hull preparation in view of the molding construction or direct lamination.
Before starting with sanding, the trip’s irregulatities are covered with epoxy filler, the same used for the car bodies repairs.
The last image recall the RG65 called “Trap65” already discussed in this forum, compared in size and style with the actual AC100b. I recall to that the Trap65 was made with extruded polystirene.
CD
Just finishing the sanding and preparing for lamination with 1 x 105g/m² glass cloth
more pics…
The nails insertion will help to locate on the female mold the rudder trunk and fin box positions. The central strip along the keel is the reference for the hull middle line and it is used first to drill the small holes into which the nails will be inserted and bonded afterward with cyanolite.
Cheers
Claudio
In parallel I starded the construction of the male mold for the cockpit and deck as a unique piece.
The pictures below show the working steps and the final result
Unfortunaletly my budget was limited to a complete hull coverage of 65/70g.
The calculations are simples : the deck + cockpit total surface including vertical walls is 1073cm²
The cloth used is 2x 105g/m², glass, therefore, in theory, the expected weight per dm² will be : 1.05 x 2 = 2.1g glass + 2.1 epoxy resin = 4.2g/dm² x 10.73 dm² = 45.06g
Thus below 50g could be the full deck coverage, unfortunately the lamination on the male mold was not easy and the weight raised very fast almost dubling .
After thinking, a female mould could have produced a better work !
I decided therefore to modify the construction method, being afterall, closer to the reals AC boats. In practice the vertical walls used for the cockpit are the ones already existing and composing the hull .
The cockpit is limited to a simple floor and one vertical wall positioned before the mast to insure the hull closure.
Cheers for today
ClaudioD
Continuing the presentation.
The following work refers to the hull preparation for molding .
The surface is covered with several (min. 5) layers of wax (paste)
Cheers
ClaudioD
PS : I can anticipate that the mold was a failure !
Hi Claudio, following you with my own AC100 mould, I’m wondering how you can anticipate failure with your mould ! what went wrong ?
Further, do you plan to hand lay-up the female mould or vacum bag ?
Cheers Alan
Hi Alan,
the first mould went wrong because I din’t pay attention to the mixing bewteen gelcoat and hardener, therefore I actually suspect that some small parts of resin did not polymerised within 24h. At that time I was not aware that 1 week later al the gelcoat went hard enough.
The second time for the second mold I was more carefull but a needle head appeared soft after demolding.
The actual model in the picture was directly laminated on the master.
Next model will be laminated with the female mould. Non vacuum, I do not have the equipments also because, in my opinion, is not really necessary for our model’s laminations expecially if the lamination is properly carried out ( nominally 50% cloth + 50% resin ; additional 5% resin for carbon tissues and 10% for kevlar ) - this is the way I do it.
Your master is the second I see, the other is made by Eugenio alias “eupon” in Rome. Both are looking very nice with a good shape !
Only one suggestion, be carefull in selecting material weights, the displacement is not very high ence any gramm is usefull.
Cheers
Claudio
Is arrived the time to prepare for the mold construction.
The fist 2 coats will be made with gelcoat from Axon, this product appears of green color. The lamination will be composed of various layers of glass cloth
In the next post I will show how to ruin a mold construction !
Cheers
Claudio
24h after the last lamination, the demolding went out rather easy.
Appeared immediately several soft spots large as a spike head. With the finger nail, the spots became wider.
At the end a rather large surface was affected and did not polymerised.
The investigation did not produced a definitive answer because tha causes retained are 2 :
1 - the epoxy gelcoat / hardener mixing action was not long enough to ensure a good mixing - (epoxy gelcoat is much more dense then normal epoxy resin)
2 - the ratio between epoxy resin and hardener for the glass lamination resin prepared for the first 2 glass layers was wrongly prepared.
Confusion may be raisen by the fact that the gelcoat used 33% hardener and the epoxy resin was supposed to be mixed with 55% hardener, doubts remain that the epoxy resin was mixed also at 33% instead of 55%.
Actually, 3 weeks later, all the mold surface is very hard like the polymerisation process went on at low speed.
The mold is actually used as retaing enveloppe during assembly of supports of a new hull.
New material is re ordered, for 84€ !
Cheers
Claudio
Ouch !!! …thought I was only one that has those type of days 
I will be trying my first attempt at making female mould and wish to ask some basics questions:
- Gelcoat: is it required to let each layer cure before adding next coat or do you coat wet-on-wet.
2: FBG Lamination: 7 layers 200 gsm unidrectional noted, is it appiled over Gelcoat when cured or wet-on-wet.
- I see you left the bow open, is there any reason for this ? just imagined with a female mould we could take the opportunity having this area closed for water tight bow.
Cheers Alan
Hi Alan,
I let you knows my previous experiences with “gelcoat”
Once I used the “polyester gelcoat” to produce half mold for the Tuiga. The day after I was intending to carry on for the second half. Surprise the Tuiga wooden master was not fitting in the 1st half mold anymore !
I called the supplier for explanations of the phenomenon.
Answer : It is normal, the polyester gelcoat contract during polymerisation by about 0.5% to 2% and in some cases even more, You should use for your models work the “epoxy gelcoat”.
So, since then I changed for “epoxy gelcoat” without any problems until now as explained. There si factor that I did not mentioned and this was the elevated temperature largely above 30°C of these daus. Would the temperature played a role , I do not knows !
There is difference, the “epoxy gelcoat” is much more dense and difficult to stir and mix. The supplier suggested to adds 10% , no more, of normal epoxy/hardener resin prepared separately and mixed after to reduce viscosity.
Back to you questions :
1 - generally I use two layers to be sure to get confortable thickness 0.5/1mm The interval between layers shall not be over one hour, better 1/2 hour according to local temperature. In practice is “wet on wet”
2 - FBG lamination always “wet on wet” The first 2 layers were of 105g/m² Twill. I used unidirectional just because I got it in stock and not because of a specific tecnical need. You could use Glass of 200g/m² type Twill all the times except the fist layers. It is important to use "soft " or “lighter” cloths at the beginning to avoid that “rough” tissues would let their marks or inprint into the gelcoat that it is still soft since the glass lamination started within 1/2 hour. 7 layers because I wanted a thick and solid wall.
3 - I let the bow open to facilitate the hull lamination getting better laydown of the tissues. better access with the brush. After polymerisation and trim of the tissus excess, I bond with loaded epoxy the small plywood frame. This frame, at the end will be the support for the rubber or silicon “bumper”.
At the contrary, if the bow is closed, the lamination work will be of poor quality and with the risk of letting plenty of air bubbles due to the working confined area. Further, the open bow facilitate the debonding of the laminated hull. Precaution, the small bow frame shall be bonded with the hull inserted into the mold to avoid vertical misalignement. For this operation is better to isolate the hull from the mold using the polyane film (garbage bag)- the picture show the bonding of the deck strip and final result.
A couple of pictures from my collection will help
Any questions ? I’m here !
Cheers
Claudio
Hi
When I firs started building my firs IACC120 with my dad, our idea was to build two identical boats. Therefore we went for the female mold solution.
Regarding Gelcoat layer, I have very good experienses with using Epoxy with som graphite powder stired in. This also makes the epoxy black, which makes a good contrast (to spot air boubbles) when laying up the FBG. The graphite powder should also make the epexy even harder. Attached some pictures of the process.
We made the mould with a closed bow. But I dont’t think that is the best solution. It is rather difficult to lay up the fibers with a good result. Maybe a vaccum bag solution would help, but i don’t have a vacuum pump… yet 
After seeing the good results of making the boats over a male mould, i think i will use that method in the future. I don’t think i will be makeing many of the same boat anyway.
Am I totally wrong by saying that the only advantage of the female mould is that you don’t have to smooth out and work on the outside of hull, on every hull you make?
/Anders
P.S. We finished our first AC120, and took it for the first sail. It performed well even though it is 400 g to heavy. There is room for improvement.
Hi Anders,
it is correct what you says. The gelcoat could be replaced by loaded epoxy resin with graphite or other colored powders.
it is also true that you can mold several hull (2 to 5) on the same wood master if the work is done carefully and good wax is used. Probably some small skin damages could be easy repaired if needed.
Female mold of course increase the number of replica, but it may be also needed small skin repairs .
In my opinion, vacuum is not needed for our models.
Nice pictures and nice work
Cheers
ClaudioD