Hi Dick
The reddish color is the RTV139 . The “master” bulb is the first wooden model to be used for the mould. Actually painted in blue.
We call “masters” all the first models shapes be used for later reproduction either for direct lamination, either for moulds making.
This is apply to the first hull or to the bulb , sometimes to the fin and rudders
Stefano last name is Pecchioli - standing with is new Alinghi SUI 100
Cheers
Claudio
Is time to close the hull and preparing the final assembly.
The servo rudder is ordered.
The bumper made from balsa, it could become a ‘master’ for a silicone moulding !
Claudio
Partial view of the servo arm from a deck opening
In order to lower the jib boom I designed this approach
because is an experimental model, I prepared several mast steps and perforated chain plates in order to cope with various Class M rigs and Class AC120 rig as well, all sail plans have 7200cm².
the actual hull status
Claudio
Comparing the two sail plans : the typical AC33 derived from the AC120 and the classic Class M.
Testing wiil be done with both configurations.
Claudio
Hello Claudio
how did you paint the bumpers of silicone. You probably made a aggrappante the product?
Is not silicone or acetate?
Thank’s
Stefano Pecchioli
Stefano is not silicone but simply balsa
Claudio
Lots of good info on casting lead! I have used the RTV to make a 2 piece mold, with “keys” to fit both halves together so the bulb can be poured as one piece. I poured the bottom half as you did, then, when cured, some vaseline and poured the top half. If the mold deteriorates, I would like to look into sand casting.
I have also made a mold of the bow of my IOM, with the balsa nose in place, using polyurathane molding compound. Then remove the balsa, put the mold back on the bow, and pour silicone into the top of the mold. When removed, the silicone is a molded-in-place bow bumper. I used a few drops of acrylic paint to color the silicone to match the hull color of the hull. It did not seem to affect the silicone in any way, and mixed easily into the silicone.
I used the polyurathane as a mold. because silicone will stick to itself if it was used as both a mold and as the bumper.
Hi Claudio.
I was surpirsed with the idea of making a bulb mold with rtvc. I have to use a plaster mold every 4 or 5 bulbs out of it, because it stars to crack. The melted lead has spread all over the kitchen twice, so i will try inmediatly to get enought rtv for 2 different shapes IOm molds.
Once i got the first half, how should i isolate that from the next half to be mold?? using only glicerin or any oily stuff like the high temp was releaser we use for laminating epoxy??
How do you keep together both silicone mold halves ?? With rubberbands???
Do you place the mold horizonatl or vertical to pread the lead in??? I use to use them vertical, cause when i did one mold horizontal the bubbles produced inside bringed a bad surface finishing and even air bubbles in the cast.
Hope you can help and provide any further directions to succed…I have spent over 10 kilos of material in all these molds!!
Tato Lazo
CHI 272
Hi Tato Lazo,
I have made this sketch to explain the working sequence I will use for my bulbs
Pratically I use only 1/2 wooden bulb shape made with various layers of triplex described earlier.
Once obtained the RTV mould, I will pour 2 lead 1/2 bulb.
The 2 halves will be bonded togheter with epoxy and glass cloth of 260g/m². Elastic rubbers will help to keep the parts.
The advantage of this method consist on the fact that there is non need to have a lathing machine, but simply easy manual work, a rasp, abrasive paper and of course a good ‘shaping’ sense.
Another advantage is that the shape will be the same for the 2 halves ensuring a simmetry.
The risks associated with a manual shaping of a full bulb is that some/many dissimetry may occurs.
According to some modeler’s exerience, this type of mould can be used for several meltings
To reduce earlier degradation, the RTV compound should have, as a minimum, a thickness of 1cm all around and shall be keept inside the framing
Working steps
Claudio
Missing detail from previous message :
between step 5 and step 6 it is necessary to wait 24 hours before turning upside-down the entire ‘bulb box’.
The carton paper shall be pulled up together with the bonded bulb.
Claudio
Hello Claudio and many thanks for this excellent thread; I’m impressed by your creativity and workmanship.
I’m planning to laminate another pair of hulls for my two metre catamaran ti incorporate lessons learned and intend borrowing your cotton fabric idea to add some decoration - I’ve attached an image of the cloth I purchased in a local fabric/sewing store yesterday.
Anyway, a question if I may. Referring to your posts #73 - #76, detailing your laminating of your hull, I notice that you lay the cotton cloth on and then cover it with two layers of 50g glass. I assume you do this to protect the cotton fabric? Do the extra 50g glass layers detract from the quality of the decoration in the cotton cloth by slightly obscuring it (my experience is that glass/epoxy laminates aren’t really clear) - I’m thinking of making the cotton cloth the last laminatation?
Thanks.
Ray
Ray
I really appreciate what you says.
The lamination sequence I used from inside to outside is :
Glass 80g/m²
Cotton 112g/m²
Glass 50g/m²
Glass 50g/m²
Why the cotton is covered by glass ?
Simply, as you mention, is to protect it in case you need to sand the external surface.
Why 2 layers of 50g/m² ?
Because, according to my experience, is much better then 1 layer of 100g/m², it contribute to the strength and the hermeticity.
The color of the fabrics are not obscured by the glass, generally is the resin that may give some opacity as seen on my experiment with the rice paper, but you can use “crystal clear” resin. see : http://www.rcsailing.net/forum1/showthread.php?t=5235
I’m very glad that you intend to make use of fabrics to adds decoration to your hulls.
The one shown is very nice hope is not too heavy. Mine is around 112g/m²
Waiting pictures now !
Congratulations
Cheers
Claudio
Thanks Claudio.
I bought 2.5 sq metres of the cloth and it weighs 300gms so the weight approximates to 120g sq metre. I had another look at the picture I attached and I have to say that the colours aren’t well represented; the ‘cream’ coloured areas are actually bright yelllow and the cloth is much brighter. overall I’ll take some more pictures in natural light.
I’ll be using vacuum bagging to laminate over solid wood male moulds so I should be able to get very good results with minimal finishing required so I think I’ll be OK with the cloth as the top laminate. I’ll also be using SP115 epoxy which is formulated to make the most of embedded graphics.
For my first pair of hulls I used a layer of 200g sq m carbon and a layer of 200g sq m glass.
I’m conscious that laying the cloth over a carbon backing is likely to make it a bit grey so I need to get a lighter backing and my thnnking is:
layer 1 = 200g sq m carbon twill
layer 2 = 100g sq m kevlar
layer 3 = 120g sq m cotton cloth
Although this appears slightly heavier than the first pair of hulls they were hand laminated and I think vacuum bagging the next pair will reduce the amount of resin I use so I expect the outcome to be similar overall.
Ray
I have seen your layers setup.
I will suggest to use always an external glass layer.
If you have any doubts, the best way is to prepare some samples 10x10cm with the configurations you eventually choose.
Try to sand the one with an external cotton fabric to see the limits !
Cheers
Claudio
Starting making sails !
The paper pattern for a classic M rig is ready.
Main with 5 panels
Jib with 4 panels
Details of what could be the Jib booms arrangement
The lower one is supposed to be fixed between mast and jib rack, only the upper is moving.
Having said that, it is not escluded that the lower boom could swing to the limits of the hull sides. This should allow the upper boom to have a different orientation angle with respect to the main boom.
The following drawing should explain how I intend to try this configuration where the forestay is shifted laterally.
If it is a nonsense , do not esitate …
My tools to assembly the panels. Very probably I will use the 8% for the Main and th 10% for the jib
Claudio
Thanks Claudio, I’ll think on this a bit more…
In the meantime, here are some better pictures of my cloth.
Ray
Beautiful colors ! Ray,
If you prepare samples, that I suggest, try as back layer both tissues , the carbon and the glass.
You will see the differences, if any, on the cotton appearance
Cheers
Claudio
Start cutting materials !
Here, I decided to use a relatively heavy tissue of 90g/m² for the Main, just because was stored in the corner since 4 years. I also told myself that an heavy tissue will be easier to manipulate with the news Blocs and third because I will know how much will be the maximum weight of the Rig
Actually the bare mast and booms are at 181g, see below, still missing are spreaders, shrouds and stays and tensioners.
Projected full rig weight is 255/260g, my design limit is 270g.
Claudio
Hi Claudio,
Don’t forget to align the leach of the sail to be parallel with the warp of the material. In your picture you have the luffs parallel. . . not good for minimizing stretch.
Thank you John, you are right, but I have always done in that “wrong way” and for my first experimental strong tissue 85/90g/m² , I hope it will forgive me for a certain while ! In our place in this season the winds varies from 0 to 3/5 knots.
Next time, using a lighter material 60g/m², I’ll promise to do it right as you said.
Working with blocs. The gap varies between 2mm at the bottom, 2.5mm in the center and to 3.5 mm at the top of the Main.
Cheers
Claudio