Finally after a small deviation in the footy camp, I decided to come back to the ESTEREL project.
As already mentioned, I will use two different external coatings for two different hulls.
The 1st will be made with transparent Gel-coat + Cadmium pigments .
Later the 2nd hull will be using as first coat the epoxy resin loaded (slightly) with silica with the aim to reduce the micro craters visible at the end of the polymerization. This what has been suggested by a technician working with a specialized company for composites.
Both methods, of course, will imply an increased weight for the lamination process. In order to compensate the gel-coat weight, instead of using 3 layers of 105g/m², I will use only 2 layers. The gel-coat layer, while kept to the minimum, is still providing some strength.
The transparent gel coat is already mixed with pigment: 180g gel coat resin + 5.3g cadmium powder.
The product after careful mixing are now resting for some 24H to allow good mix and air bubbles exit
The mold received an additional of mirror glaze wax coat.
The glass tissues are already cut.
Before applying the gel coat, the catalyzer weight will be based upon the weight of resin + the added pigment
ClaudioD
This afternoon I will start lamination.
For what I can see this morning the resin is relatively fluid from what I was expecting . This is before mixing with the catalyst
I was expecting some more thixotropic aspect. Not excluded to add silica powder after mixing with catalyst.
ClaudioD
The Gelcoat is applied !
Prepared 286g including some silica to increase viscosity.
Out of the 286g , 125g are left in the plastic bucket. Effective Gelcoat sprayed on the hull = 161g
If that is correct the hull weight projection will be : 161g + 120g of glass lamination = 281g
120g are the results of 2 layers of 105g/m² = to 2.1g/dm² x 2 due to epoxy resin = 4.2g/dm²
The hull surface , wet and dry, is 28.6dm² x 4.2g/dm² = 120.12g
The expected weight will be 110/115g heavier then the previous hull.
Considering that the gel-coat do not requires additional surface painting, I assume that the overall hull weight will be very close to the previous one.
I am glad that you came back to 123 project when I see you using gelcoat, the question comes to my mind: how do you plan to neatly connect the hull with the deck? Or the deck will be painted?
In a classic way and then white painted !
Actually, I’m afraid that the gel-coat application with a brush is not as good as expected. The weight will very probably confirm that !
I should have used a small roller to allow a more homogeneous gel-coat distribution. Further I should use more silica to increase viscosity, or treat one side at the time and then the bottom.
Ready to repeat the operation.
ClaudioD
might be a good idea. when i was playing with gel coats, also with brush application, one layer left “daylight transparent” smudges. On the finished hull it looked really ugly. the paint on the inside solved the problem. Anyway, awaiting your progress and good luck
Hi Lukasz,
This morning, about 18hrs later, the lamination was rather sturdy giving the impression that the polymerization was rather advanced.
I decided to start cutting the glass excess.
At the end was surprisingly easy to pull up the laminated hull and get it out from the mold.
The surface appeared opaque and not brilliant as expected.
I do have two explanations :
First the there is still a wax coat onto,
Second the use of silica.
After some soft towel cleaning with water the hull recovered some shiny surface.
Defects are plenty of smudges every where that appear also without back-light. Real rubbish, although not observable with front light!
The most important one is the weight = 335g against the 182g, thus 153g too much and therefore not acceptable for my weight budget.
Possible remedies :
1st observation :
among the ones mentioned above, the hull is rather robust, the gel-coat participate very much to that result.
For the next hull I will try to use a small paint roller to get a better gel-coat distribution.
No silica will be used to increase the viscosity, but only one side at the time will horizontally positioned and sprayed with the roller.
That means that from one side to the other I should wait for about 2hrs. The hull bottom will be last.
It may be good idea to roll with small quantity of gel-coat and repeat the operation the day after.
It is expected with the above method to spare several grams !
3rd observation :
because of the observe hull strength, instead of two layers of 105g/m² I will use 2 layers of 85g/m².
The weight gain will be not very high, only 23/25g, but could be used to put reinforcements where needed.
A patch will be made to experiment what described above. BTW this is what I was suppose to do at the beginning…mistakes are part of the game …but one should try to reduce them in number anyhow while learning a lot !!!
I bought the paint rollers !
I used for the first trial the wool 4mm short hair.
The support is a 1mm plastic sheet.
The 1st pass showed up several smudges.
I let rest for about 1/2 hour and passed a second coat.
The picture shows the drastic reduction of smudging effects.
The measured & calculated weight as it stand, show 4.86g/dm²
Assuming good repeatability of the process and with the addition of two glass layers of 80g/m² and equivalent epoxy resin, the total expected weight should be about 8.35g/dm² and anticipating a total hull weight of 245/250g
Hi Claudio, I’ve never used gelcoat hence watching with keen interest, are you planning to apply the FBG after the gelcoat has gone off (wet-on-dry) ?
Is possible to apply peel-ply after last coat of gelcoat (before it goes off) to at least give the surface something rough to bond too ? …hmm just thought you would not want to peel the gelcoat off when the peel-ply is dried … drop that idea
Hi Alan,
2h 30’ later the gel coat appeared sufficiently tacky to decide the glass samples lamination.
The peel ply was applied as soon the lamination was completed and removed 30 minutes later.
For what I know, most generally, the peel ply is removed at the end of polymerization. Is not my case !
My purpose is to use the peel ply ribbons only to absorb eventual excess of resin. That is rather visible when the peel ply look saturated by the resin. See pictures.
Is not my purpose to use peel ply to get a rough surface, to do that, when apply “wet on dry” is to use a sponge scourer as said before.
If I can manage to repeat the full process on the hull, the final weight should be 100g lighter then the hull made 2 days ago and this become very acceptable !
I let the peel-ply cure with the lamination as the name suggests it does peel very easily and leaves nice rough surface for bonding during hull fit-out.
Hi Marc,
I have not well understood your question sorry ! But in my previous descriptions, I used peel ply on curved hull when freshly laminated directly on the master as well with female molds.
Peel ply can be obtained as large tissue size similar to glass fiber or as ribbons of various size.
ClaudioD
Hi Don,
the Epoxy Gel Coat I use is made by a local Company “Composites REA Industry”.
The particularity is that is colorless and specifically made to be pigmented.
How it is good compared with other gel coat I don’t knows.
What I can tell is that the Cadmium power pigment added is 3.5% in weight
See picture of cans
Cheers
ClaudioD
I made an error considering the hull surface = 28.6dm².
This was the surface of the previous hull configuration with a bowed deck.
Since the hull was modified to allow the use of a flat deck and the sides where increased by 15mm.
This modification added some 3.7dm² .
The actual hull surface is 32.3dm²
In spite of above I have a good new ! The last laminated sample exhibit 6.40g / dm²
Therefore if the same process is repeated for the hull, the new projected weight will be : 6.40g/dm² x 32.3dm² = 206.7g
