Hi Claudio
I will be cutting the bow off my molds. The lay-up with the closed bow is a pain.
A question. I have never used gelcoat in my molds. I use 2 or 3 lays of heavy matt. I figure that if I’m going to paint the boat I have to sand it anyway so as long as the inside of the mold is fair it should be good enough. I have pulled a half dozen hulls out of the oldest mold and it shows no sign of wear. Why use gelcoat?? What am I missing?
Don
Here are a few videos done by an experienced mold construction guy. This one is on mixing and applying the epoxy “tooling” coat, that many people call “gel coat”, to a plug.
Hi Don,
it is right to use mat for the first layers, followed by wowen glass . Personally I prefers twill tissus
Gelcoat give generally a better finish and harder surface, rendering more resistant to several molding process.
Cheers
ClaudioD
Claudio,
Great work! Are you going to sell any hulls once you complete your molds and are happy with them? Thanks.
Brian
Thanks Claudio & Don for the heads up on not closing off the bow in female mould, I will cut it off for all reasons posted, I do recall when hand laying up the female deck mould on my 120, that combination of cloth & epoxy did not like sharp angles causing trap air that required filling afterwards, I know now to chamfer corners to avoid this problem.
Anders great work on your “first 120” as you say it is 400 grams overweight and looking for future improvement, I’m guessing you could be making other hulls? your question about the advantage of female mould is that you don’t have work on outside hull is no wrong.
When using a male and sanding for smooth finish on my first 120, I ran into the problem of creating pin-holes on the outer hull surface, due to too much sanding which, required filler and priming before final painting, all of the this added weight of course and the finish was not as smooth as I would have liked.
As Claudio says, the displacement of AC100 is critical and grams really add up quickly if you’re not careful, this is the main reason I’m using female mould, I’m planning on using colorant in the lay-up to avoid filling, sanding, primer, painting and weight.
Secondly, as I’m making a multi number of hulls on this project, I also want a durable mould and all the hard work is in the preparation.
Cheers Alan
No Brian,
my task, for the time being, is limited to the design and development of the model. I construct a prototype for the testing in the water just to confirm the soundness of the design. This model is developped with the aim to create a pure racing boat, still keeping the AC boat apperance. Is just the youngher sister of the AC120 but more easy to transport being only 100cm long.
This tread is ment to show the various phases of the construction dedicated to the modeler that wish to have an images support. I do include also the description of the “failures” as such to allert others to avoid similar mistake. In my life I learn a lot from mistakes.
Finally, to respond to your question, earning money with that it is not my cup o tea, I’m too hold.
I provide the detailed Plans including shadows in scale 1:1 and this tread, hoping that a voulenter modeler is capable to construct the full boat.
For your information an Italian group of modelers have created, with my support including tips and Plans, the Class AC100 . The official site should open in those days. Unfotunately all the text are in Italian, but the almost 250 pictures contains comments in English. Watch for this : www.ac100.it You can download all the drawings needed for the construction.
Cheers
ClaudioD
the story continue !
After the mold lamination failure, while waiting the arrival of the new material, I decided to make an Hull by direct lamination onto the wooded master plug.
see next…
ClaudioD
continuing from previous post…
About weight :
As noticed on one picture , I used for the lamination, 3 layers of glass cloats of 105g/m².
This choice is coming from the fact that for my models, varying from 100cm to 120cm in lenght, I employ the sampling of 5.5g/dm² up to 6.5g/dm². This weight per dm² and according to my experience, give sufficient strenght to the finisched hull.
The actual calculated hull surface is of 23.41 dm².
Multliplying 3 layesr of glass 3 x 1.05g/dm² we get 3.15g/dm²
Adding equivalent weight of epoxy resin of 3.15g, we reach a mix of 6.3g/dm²
therefore the “projected weight” of the hull shall be 6.3g/dm² x 23.41 dm² = 147.48g
Observing the pictures it is possible to see that the trimmed and coated ith primer, the hull is actually weighting : 164g
By adding the deck wood strip + the bow shadow + the silver paint the actual weight is : 187g.
Cheers
ClaudioD
THE AC100 SITE IS OPEN >>>>> WWW.ac100.it
cheers
ClaudioD
Continuing the Built log
The Hull is ready, now I presents the deck laminations
Cheers
Claudio
These images shows the various supports to be integrated inside the hull in order to support the mast, the winch, the rudder stock the rudder servo
I used plywood of 1.5mm laminated with tissues.
To note that at this time that I decided, for comodity, to mount booth servos over the floor after proper painting and grease on the exit axis.
The attached drawing, commented in Italian, shows two things, the vertical wall of the fist cockpit layout are removed by making a wide floor and reducing weight, the other as already wrote , to mount the servos outside. To note further that by putting the servos under the floor it is necessary to add a new support for the winch.
Cheers
ClaudioD
These images shows the various supports to be integrated inside the hull in order to support the mast, the winch, the rudder stock the rudder servo
I used plywood of 1.5mm laminated with tissues.
To note that at this time that I decided, for comodity, to mount booth servos over the floor after proper painting and grease on the exit axis.
The attached drawing, commented in Italian, shows two things, the vertical wall of the fist cockpit layout are removed by making a wide floor and reducing weight, the other as already wrote , to mount the servos outside.
Cheers
ClaudioD
These images shows the various supports to be integrated inside the hull in order to support the mast, the winch, the rudder stock the rudder servo
I used plywood of 1.5mm laminated with tissues.
To note that at this time that I decided, for comodity, to mount booth servos over the floor after proper painting and grease on the exit axis.
The attached drawing, commented in Italian, shows two things, the vertical wall of the fist cockpit layout are removed by making a wide floor and reducing weight, the other as already wrote , to mount the servos outside. To note further that by putting the servos under the floor it is necessary to add a new support for the winch.
Cheers
ClaudioD
Hi Claudio,
I have just been catching up on this interesting article and I have a couple of important pointers that might help others avoid the same problems with the mould manufacturing process -
My personal recommendation is - If you "post-cured’ the mould before removing the mould from the plug…Any doubt about the mix ratio or quality is removed, or, just as importantly - proved… !
An elevated temperature cure cycle is a must for a stable mould structure… You would get a high profile ‘stringing up’ not doing this in my world.
Just second guessing is not scientific , I suggest at least one cycle of cold-hot- cold for the mould when still on the plug.
I am trying not to sound too up my own arse, but, you might just thank me for saving time and money later…
You havn’t said if the mould was heated or not, so ~I am presuming that they were not… If it was, then that is real bad luck and that happens to us all.
Cheers,
Jim
Tanks Jim for the very good suggestion.
Obviously my mold was not exposed to any post curing just standing there at 32°C for 24hours waiting for me !
Could you be more precise about the cycle time and temperature gradient ? the manufacturer of my resin do not suggest any post curing .
In the past I used a resin where was specified for ‘ultimate strenght’ to expose at 60°C for 4 to 6 hours. - sincerely never done because I did not considered necessary to search for “ultimate strenght”, being just a simple model hull.
Similarly, I do not consider worth to spend money for Carbon cloth judging not necessary if the “mechanical strenght” is the justification.
Question : I should make a wooden box fitted with bulbs ?
Thank you again
Cheers
ClaudioD
Hi Claudio,
Okay… without full knowledge of the resin system you prefer, it is hard to give a proper cure regime.
However, with my general knowledge I would offer a minimum of 7 - 10 hours @ 50c - 65c… Depending… some resin systems are nearly double that.
Remember, that the ‘tool’ is the key to success!
Firstly, Pre- cure the plug to the same temp/time you will cure the mould to… Important to remove the initial shrinkage from the plug and to stabilise it at the cure temperature.
‘Muppets’ always overlook this and consider it as a waste of time, but those in the know, wouldn’t do it any other way.
My preferred post cure technique for non vacuum - is to first have an ambient temp cure and then use a ‘axial’ fan heater with cardboard boxes. Measure the temperature with a thermocouple - taped to the mould or the inside of the plug.
Ramp rate should be around 1 -2 c per hour if you want to be really fussy. ~IMO not really that important as the “cool down cycle” which should be as slow as possible. (Half the ramp rate to temp - back to ambient)
Air flow is a good thing, as it helps to distribute the heat evenly, I say again - VERY GOOD IDEA!
Light bulbs do not offer the airflow needed to successfully post cure an item evenly, and could introduce twists or cause the mould to pre-release from the plug due to hot spots.
This is a really generalised guide to a post cure without vacuum, but not a bad place to start.
Avoid temps exceeding 75c as wood/fillers/paint can shrink alarming amounts beyond this…
Have fun!
Jim
Thanks Jim , I will think about and how to organise the set-up.
Once I remember, I did put the rg65 hull and mould into a black garbage bag and the suspended outside in a sunny hot day for four hours. I don’t recall if this was providing benefits and in any case not measurables.
Cheers
ClaudioD
continuation of assembly,
Here is the Fin Box integration as the rudder trunk as well.
In order to ensure the “verticality” of the Fin Box, I first leveled the hull, then I used a false Fin, plywood blade with a counter weight to get the vertica squared position.
Cheers
ClaudioD
Others few images …about the various supports
Cheers
ClaudioD
hull support’s mounting process …continue
This is the area where one can loose or gain weigts… important for competition models when every gained gramm could go in the bulb or ballast.
It is also my thinking that as the the model design get smaller, the gaining gramms is not important anymore at the contrary search for some inertia will pay. It is my opinion that too light boats become ungovernables as soon some small waves start coming up.
In the pictures can be seen the weight grow, 230g, 295g, 355g …
I shall recall that the bulb alone is supposed to be 1750g by design
Cheers
ClaudioD