The peel ply is the 3rd pic ‘opposite face’. The first pic shows the side that was in contact with the plastic sheet.
At the moment I covered with a new gel-coat half of the plastic sheet, tomorrow I will add and adjacent coat with some overlapping.
This is to simulate what I will do practically with the Hull.
As said before, to avoid the use of silica and increasing the viscosity (tixotropy) and therefore increasing the overall weight, I will apply the gel -coat to the hull in 3 steps, lateral sides 1 and 2 and the bottom at the end.
This process will requires 3 days due to polymerization process.
Once the full Hull will be covered with gel-coat, the surface will be made rough with the scourer sponge or abrasive paper.
I will not use peel ply to rely on the roughness since I fear to pull up also the gel-coat…
The glass lamination, although not ideal in terms of final strength, will be “wet on dry”.
My model do not requires, anyhow, to be as strong as the Glass/Epoxy may offer with the Data Sheet.
Cheers
ClaudioD
Surface scoured and laminated .
Peel ply not used to compare with the weight of previous lamination above.
The back light show the overlapping limit
In the central photo at the bottom is visible the effect of roller with almost no resin left
ClaudioD
Hi Claudio, I would be more afraid of the scoured gel-coat de-laminating from the wet-on-dry lamination, if the hull had a knock.
Is it possible to try test with wet-on-wet, applying two layers of FBG then applying the peel-ply …just like to know the result, don’t want to waste you time & materails, just curosity,
what you are asking is what was already done with the first sample. Wet-on-wet + peel ply - see post 12
The scouring is more a gentle rubbing (see 1st pic) on dry gel coat is rather soft and no delaminations are expected, it is much less risky then the pulling force needed with the peel ply !
The second gel-coat sample trial is completed.
No Peel Ply used !
Double coating with overlapping at 24hours interval.
While the general appearance is very similar to the first sample, although the back-light show some density variation due to coating overlapping, the major noticeable change is coming from the weight.
The 3 samples are close each other in term of weight but certainly higher then on the first sample.
IMO that is due to the fact that no peel ply was used to absorb part of the resin after lamination.
Thus Peel Ply help a lot in reducing weight !
The 61g overweight should largely compensated by absence of filler, primer and paint. No micro craters - no leakeages !
The presence of gel-coat render the Hull more sturdy !
A small aesthetic detail, is that the presence of the gel-coat offer the possibility to laminated the hull with overlapping patches rendering the work more simple.
All in all, the use of gel-coat requires a little more work and practice to avoid overweight excess, but the advantages are very
encouraging.
BTW any colors are possible !
This trial was for me a good lesson that deserve to be applied for the next Hull molding.
The use of charged epoxy resin, did not offer a solution to micro craters.
Plasticine to form an edge to fill up with water.
Except one spot, no other leaky points observed after 1 hour. 4 primer coats were not sufficient to fill up the craters.
The laminated patch passed from 3.39g/dm² before coating to 5.01g/dm² after coating.
it looks like the paint did not adhere to those spots where the craters are. almost looks like what I would call a “fisheye” which is a result of poor cleaning of the material prior to painting to remove all surface impurties, waxes, oils, ect…
Hi Marc,
I washed with acetone several times, I rubbed with # 600 and again washed with acetone … and that are the results.
Probably my primer spray can is expelling too large particles, but even with that, I don’t think to go that way anylonger, too much work to get it right.
I will consult my car body painter to see if there is any solution to the craters phenomenon.
Cheers
ClaudioD
Hi Claudio
I fought with pin holes for years and found no way to stop them other than using way to much resin. Not a good solution. So I tried rubbing the primer in with my fingers. You can see the primer come through so you know that the ones that go through are full. It made for a messy job and a lot of sanding. Recently I thought of rubbing the primer in and then wiping it off with a rag. It works great! I rub primer in an area about the size of my hand and then wipe it right off as much as possible. When it’s dry a light sanding and spray on a coat of primer. Presto! no holes. And absolutely minimal weight gain.
Try it, You’ll like it. I don’t even think about pin holes any more.
Don
Claudio I noticed you used wax on the Perspex, I use 80 gsm skin of FBG that is wetted out on Perspex & left to cure for all decks on my boats and never used wax & it peels off very easily.
Perspex (unscratched) is natural plastic release surface for epoxy that gives perfect shiny finished surface further, I also use lowest possible viscosity for epoxy mix (even warm it up) and never had problem with pin holes as it wets out the cloth very nicely. Jim’s tip of leaving the lamination in a cooling environment while going off definitely helps to stop any air trapped in the lamination from expanding, causing bubbles or pinholes.
I’m really not sure if it is the absence of wax, low viscosity or cooling off that prevents pin holes from forming, but it’s a good formula that works very well for me…touch wood
Yes I know that FG get easy away from perspex surface without wax, but mine is always a precaution !
I think that reducing the viscosity will not help with a female mold, the resin will sag to the mold bottom more quickly.
Rubbing and sanding is what I have done for years and it is always a dirty job !!!
For sure the best method once the laminated hull is free, is to cover entirely with thin primer a couple of times followed by wet sanding.
Use of air brush with two components polyurethane paint.
Several of my hull has been painted by a professional, but every time the weight went up almost to 100g for a class M (36dm² average)
As said above, I will pay a visit to the car body painter. It is also possible that the type of paint used with the spray can is part of the problem.
For years I have avoided, as many modelers, to use gel-coat due to the additional weight.
Now, that I finally found a way to control the weight of the gel-coat, I will continue on that direction unless I will meet another failure ! heheh !!
I will let you know about my findings ! For sure I’m a bad painter !!
Cheers
ClaudioD
in my latest carbon hull RG65 I did a layer of 5.7ounce carbon with a layer of .5 ounce glass and several coats of epoxy even after wet sanding and cleaning I had sanded to carbon in a few spots so i went back over top with some clear coat and I still had a few fisheyes which look like the micro craters… the other issue could be that the surface tension of the paint was just a bit to much to flow into the small pores…
I found this interesting reading : http://en.wikipedia.org/wiki/Spray_painting
Paint atomization and nozzles selection are part of the game, personally I ignore all !
I would like to discover the origin of the micro craters since this do not occurs on other materials. Air entrapment in the fibers, …etc.
ClaudioD
Went reading about aerosol cans : http://www.autobodystore.com/ms5.shtml
Probably nothing wrong with that although there are good and poor quality materials !
I just toke some macro shots on 80g/m² glass, and it is clear to me that the woven tissue have large “holes” to let create craters.
Obviously heavier tissues do have larger “holes”
As visible, these holes cannot be filled up with paint.
IMO only one solution, after lamination it is necessary, as I always did it, to apply a good “two components” thin primer with brush or spatula on all the surface. This operation requires wet sanding to remove all the excess of primer hoping that holes are definitively filled up other wise the operation shall be repeated.
Care shall be taken to avoid adding too much weight due to surface finish unless is taken into account during hull design !
Cheers
ClaudioD
Just started a new hull lamination trial in accordance with the method developed above for the Gel-coat application.
I used a 5cm roller with 4mm wool hair.
Amount of Gel-coat used about 58/60g covering almost 50% of the hull surface.
Expected final hull weight with 2 x 80g/m² glass : 220/225g
The second Hull half is also covered with Gel-coat !
A couples of small dots (fish eye) need to be covered in a couples of hours.
Tomorrow I will initiate the glass lamination after gentle rubbing the gel-coat surface.
ClaudioD
